E1138 Volume 2 ENVIRONMENTAL ASSESSMENT STUDY FOR THE LAGOS WATER CORPORATION UNDER THE WORLD BANK ASSISTED PROJECT PREPARATION FACILITY FOR THE SECOND NATIONAL URBAN WATER SECTOR REFORM PROJECT FINAL REPORT July 2005 U Environmental Assessment Study of Lagos Water Corporation July 2005 EXECUTIVE SUMMARY This project titled "Environmental Assessment Study for the Lagos Water Corporation" under the World Bank Assisted Project Preparation Facility for the National Water Rehabilitation Project has been carried out. The Project is aimed at addressing the environmental impact of wastewater disposal at Lagos Water Treatment Plants at Adiyan and Iju. The objectives of the Project included the following: (i) To analyse the current adverse impacts of the two treatment plant on nearby river and land uses. (ii) To define practical design and performance standards for treatment and disposal of sludge and wastewater from the plants that will eliminate plant-induced adverse effects on the receiving waters and related land uses. (iii) To design a practical, costed program for improving the receiving waters to a condition similar to, and commensurate with, their condition upstream of the plant discharges. The above study has been considered from the points of view of Environmental Geochemistry, Ecology and Environmental Engineering. The "Project Area" is located north of Lagos between latitude 6038'N and 6043'N and longitudes 3017'E and 3023'E on Lagos Topo Sheet 279NE on a scale of 1:50,000. The project is located in Ogun State under the Ifo South Local Government Area. Prior to fieldwork, deskwork was carried out for the on-the-spot assessment of the current situation, identification of impacts as well as the collection and evaluation of baseline data for the two Waterworks. Such baseline data included _ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1 Environmental Assessment Study of Lagos Water Corporation July 2005 . physico-chemical data for the month of August to November 2004 and the months of January and April 2005. The result of the evaluation revealed Adiyan Waterworks to be producing better quality water than Iju waterworks. Iju Waterworks have impacted more on the nearby environmental than the Adiyan Waterworks because it generated more wastewater and more sludge than the Adiyan Waterworks. From the fieldwork point of view, 9 pairs of water samples, 8 plant samples, 3 soil samples as well as life forms comprising phytoplankton, zooplakton and nekton in water were collected, analysed and evaluated on the basis of environmental geochemistry and ecology. The above samples were collected from both the upstream and down stream sectors of River Adiyan as well as from the clean waters of the two waterworks and their evaluations revealed current adverse impacts of the two plants on the nearby River Adiyan. From the geochemical point of view, the results of the analysis of water, plants and soil indicated higher concentration of heavy metals in samples from the upstream sector of the Adiyan River than its downstream sector. This has resulted in the reduction of fishes as well as aiding eutrophication resulting in high growth of weeds (ferns) in the downstream sector than in the upstream sector of River Adiyan. The weeds themselves have impacted negatively on the environment. The weeds have become a breading ground for mosquitoes thereby resulting in high prevalence of malaria among the people of the area. From the ecological point of view, the results and the evaluation of the physical, chemical and primary productivity revealed a negative impact of the two plants on the nearby community. The primary productivity at Akute and the upstream sector of River Adiyan were found to be higher than at the downstream sector of the Adiyan River. The low primary productivity was as a result of the 111 Environmental Assessment Study of Lagos Water Corporation July 2005 wastewater discharged from both Adiyan plant and Iju plant respectively into the downstream sector of River Adiyan. The wastewater coupled with high amount of silt contained therein (resulted from the non-proper functioning of both plants) are discharged into River Adiyan thereby causing siltation of the river beds resulting in the flooding of River Adiyan as well as eutrophication. As a result of the above, life forms in the downstream sector of River Adiyan have been reduced and much room has been given to large scale breeding of mosquitoes. The consequences of this is the prevalence of malaria in the community. From the Engineering point of view, attempts have been made to calculate the wastewater generated per day at the two plants. From Adiyan plant, a maximum of 1.953 million gallons of wastewater is generated per day while an average of 0.739 million gallons of wastewater is generated per day. At Iju waterworks, a maximum of 5.635 million gallons of wastewater is generated per day while an average of 2.515 million gallons of wastewater is generated per day. From the above values, the average quantity of dissolved solids vis-A-vis sludge/slit contained in the wastewater is estimated at 1.10%. The above wastewater and the contained dissolved solids emanated from the non-proper functioning of the equipments like pump, sedimentation beds and filtration beds in the plants. Now to define practical design and performance standards for treatment and disposal of sludge and wastewater from the plants that will eliminate plant induced adverse effects on the receiving waters and land uses is to rehabilitate the two plants especially the sedimentation beds and the filtration beds. This Iv Environmental Assessment Study of Lagos Water Corporation July 2005 operation will reduce quite tremendously the amount of wastewater generated as well as the amount of dissolved solids. From the above, the volume of dissolved solid generated and discharged will probably assist in designing a practical, costed program for improving the receiving waters to a condition similar to and commensurate with their condition up stream of the plant discharges. This practical, costed program will be achieved through the channelisation of River Adiyan from Adiyan Plant to the downstream of Iju plant. The dredging will span an average width of 25 meters, a length of 3 km and a maximum depth of 1 meter. The total volume of material to be excavated will be 15,000 cubic meters when one takes into consideration the trapezoidal nature of the sector of the river. The channelisation involves removing the unwanted materials from the river, channel and disposing the materials. The average cost of carrying out this operation is estimated at N2000 per cubic meter, making the total cost of the operation to be N30,000,000 ($231,000). This approach will enhance flow in the river, encourage fishing and navigation; and minimize the impact of dredging on the environment. Subsequently, a community-based forum should be initiated by the Lagos State Water Management Board which will be aimed at discouraging indiscriminate dumping or building on the water course by the community. In addition to the above, a further need for more detailed studies is recommended, among others, to: 1. Examine the river form and function and develop costed alternative for how these can be restored and 2. Determine how the dredging needs to be done, and the spoils disposed of, so as not to cause other environmental and social impacts. v Environmental Assessment Study of Lagos Water Corporation July 2005 It is however very important to note that the above recommendations can only be meaningful after the rehabilitation of the plants earlier suggested has been completed and properly operated. vi Environmental Assessment Study of Lagos Water Corporation July 2005 TABLE OF CONTENTS EXECUTIVE SUMMARY CHAPTER ONE 1 1.0 INTRODUCTION 1 1.1 Terms of Reference 1 1.2 Objective of the Study 2 CHAPTER TWO 3 2.0 METHODOLOGY 3 2.1 Scope of Work 3 2.2 Research Approach 3 2.2.1 Desk study 3 2.2.2 Adiyan Waterworks 4 2.2.3 Comparison of Water quality from Iju and Adiyan Waterworks 6 2.3 Field Studies 8 2.3.1 Location and Accessibility 8 2.3.2 Relief and Drainage 11 2.3.3 Climate and Vegetation 12 2.3.4 Vegetation 14 2.3.5 Land Use 16 2.3.6 Geomorphology 17 2.3.7 Local Geology and Hydrogeology 17 2.3.8 Hydrology 19 2.4 Samples Collection 20 2.4.1 Water Samples 20 2.4.2 Plant Samples 21 2.4.3 Soil Samples 21 2.4.4 Life-Form Samples 22 2.5 Laboratory Analysis 22 vii Environmental Assessment Study of Lagos Water Corporation July 2005 2.5.1 Geochemical Samples 22 2.5.2 Ecological Samples 22 CHAPTER THREE 27 3.0 RESULTS OF LABORATORY ANALYSES 27 3.1 Geochemical Consideration 27 3. 1.1 Water Analysis - Heavy Metals 27 3.1.2 Plant Analysis - Heavy Metals 35 3.1.3 Soil Analysis - Heavy Metals 40 3.1.4 Environmental Implications 46 3.1.5 Mitigation Measures 47 3.2 Ecological Consideration 48 3.2.1 Comparative Study of River Ogun at Akute Intake, River Adiyan Upstream and River Adiyan Downstream 48 3.2.2 Primary Productivity 5 1 3.2.3 Morpho-edaphic Index (M.E.I) 51 3.2.4 Flora and Fauna 52 3.2.5 Comparative Study of Iju and Adiyan Waterworks 54 3.2.6 Environmental Impacts 61 3.2.7 Mitigation Measures 64 CHAPTER FOUR 65 4.0 ENGINEERING CONSIDERATIONS 65 4.1 The Waterworks 65 4.1.1 Introduction 65 4.1.2 Akute Intake on River Ogun 65 4.2 The Water Treatment Plants 68 4.2.1 The Adiyan Water Treatment Plant 68 4.2.2 The Iju Water Treatment Plant 72 4.3 Plant-Induced Problems 78 4.4 Mitigation Measures 79 viii Environmental Assessment Study of Lagos Water Corporation July 2005 4.4.1 Immediate Action 79 4.4.2 Future and Regular Action 80 CHAPTER FIVE 86 5.0 DISCUSSION OF RESULTS 86 5.1 Geochemical Impact 86 5.2 Ecological Impact 87 5.3 Water Quality 88 5.4 Geomorphology 88 5.5 Mitigation Measures 89 CHAPTER SIX 92 6.0 CONCLUSION AND RECOMMENDATION 92 6.1 Conclusion 92 6.2 Recommendation 93 Reference 95 LIST OF FIGURES Fig. 2.1: Monthly-seasonal variation of colour in raw and treated water from Adiyan Waterworks 4 Fig. 2.2: Monthly-seasonal variation of turbidity in raw and treated water from Adiyan Waterworks 5 Fig. 2.3: Monthly-seasonal variation of pH in raw and treated water from Adiyan Waterworks 6 Fig. 2.4: Monthly-seasonal variation of pH in raw and treated water from Iju and Adiyan Waterworks in 2004 - 2005 6 Fig. 2.5: Monthly-seasonal variation of alkalinity in raw and treated water from Iju and Adiyan Waterworks in 2004 - 2005 7 Fig. 2.6: Monthly-seasonal variation of total hardness in raw and treated Water from Iju and Adiyan Waterworks in 2004 - 2005 8 ix Environmental Assessment Study of Lagos Water Corporation July 2005 Fig. 2.7: Topographical map of the Project Area 10 Fig. 2.8: Mean monthly rainfall of the Project Area 12 Fig. 2.9: Mean annual rainfall of Nigeria 13 Fig. 2.10: Effective temperature of Project Area 15 Fig. 2.11: Climatic zones of Nigeria 15 Fig. 2.12: Geological map of Project Area 18 Fig. 3.1: Iron content of water 32 Fig. 3.2: Copper content of water 32 Fig. 3.3: Zinc content of water 33 Fig. 3.4: Lead content of water 33 Fig. 3.5: Arsenic content of water 33 Fig. 3.6: Cadmium content of water 34 Fig. 3.7: Nickel content of water 34 Fig. 3.8: Manganese content of water 34 Fig. 3.9: Molybdenum content of water 35 Fig. 3.10: Iron content in plant tissue 38 Fig. 3.11: Copper content in plant tissue 38 Fig. 3.12: Zinc content in plant tissue 39 Fig. 3.13: Manganese content in plant tissue 39 Fig. 3.14: Molybdenium content in plant tissue 39 Fig. 3.15: Iron content of soils 44 Fig. 3.16: Copper content of soils 44 Fig. 3.17: Zinc content of soils 44 Fig. 3.18: Lead content of soils 45 Fig. 3.19: Arsenic content of soils 45 Fig. 3.20: Cadmium content of soils 45 Fig. 3.21: Nickel content of soils 46 Fig. 3.22: Mercury content of soils 46 Fig. 4.1: Volume of waste generated in Adiyan Plant in 2004 72 x Environmental Assessment Study of Lagos Water Corporation July 2005 Fig. 4.2: Volume of waste generated in IJu Plant in 2004 77 Fig. 4.3: Sketch of the river channel 81 LIST OF TABLES Table 2.1: Water supply borehole data 19 Table 3.1: Distribution of heavy metals in the analysed water samples 28 Table 3.2: Distribution of heavy metals in the analysed plant samples 35 Table 3.3: Distribution of heavy metals in the analysed soil samples 40 Table 3.4: Physical characteristics of water at Akute Intake, River Adiyan upstream and River Adiyan downstream 48 Table 3.5: Chemical characteristics of water at Akute Intake, River Adiyan upstream and River Adiyan downstream 49 Table 3.6: Mineral and Heavy metals content of Akute Intake, River Adiyan upstream and River Adiyan downstream 50 Table 3.7: Primary productivity of Ogun River, River Adiyan Upstream and River Adiyan downstream 51 Table 3.8: Morpho-edaphic Index of water from River Ogun at Akute and River Adiyan 52 Table 3.9: Flora and fauna composition of River Ogun and River Adiyan 53 Table 3.10: Record of human activities and sources of pollutants in and around River Ogun and River Adiyan 54 Table 3.11: Physical characteristics of clean water from Iju and Adiyan Waterworks 56 Table 3.12: Chemical characteristics of clean water from Iju and Adiyan Waterworks 57 Table 3.13: Mineral and Heavy metals content of clean water from Iju and Adiyan Waterworks 58 Table 3.14: Physical characteristics of sludge from Iju and Adiyan Waterworks 59 xi Environmental Assessment Study of Lagos Water Corporation July 2005 Table 3.15: Chemical characteristics of sludge from Iju and Adiyan Waterworks 60 Table 3.16: Mineral and Heavy metals content of sludge from Iju and Adiyan Waterworks 61 Table 3.17: Summary of identified impacts at Akute, Iju and Adiyan Waterworks 62 Table 4.1: Functional Assessment Plan for the Lagos Water Supply Corporation 82 Table 4.2: Monthly Performance Assessment Summary 85 LIST OF PLATES Plate 4.1: Discharge channel from Adiyan Plant 69 Plate 4.2: Point of discharge of wastewater from River Adiyan - a building is obstructing the flow. 70 Plate 4.3: River Adiyan at upstream section before the discharge point 70 Plate 4.4: Downstream section of River Adiyan 71 Plate 4.5: Old inlet house at iju Waterworks now flooded and overgrown with weed (April 2005) 73 Plate 4.6: A team of Consultant within the sedimentation tank area 75 Plate 4.7: Effect of backflow from River Adiyan to the staff quarters within Iju plant (April 2005) 75 Plate 4.8: State of River Adiyan at the downstream end of Iju Plant (April 2005) 76 xii CHAPTER ONE 1.0 INTRODUCTION The Lagos Urban Water Corporation, having realized the environmental impacts of its two waterworks at Iju and Adiyan on the nearby river as well as the seasonal flooding of the community road in the area resulting from the discharge of wastewater into the nearby river, has decided on measure to arrest the ugly situation. To achieve this, an Environmental Assessment study of the area under the World Bank Assisted Project Preparation Facility for the National Water Rehabilitation Project has been proposed. 1.1 Terms of Reference The Term of Reference (TOR) of this study is the Environmental Assessment Study for the Lagos Urban Water Supply Project (LUWSP). Under this "Term of Reference", an environmental issue associated with the disposal of wastewater at Iju and Adiyan plants has been found to exist. This has been as a result of the clarifiers which do not work and the sludge which is discharged into the nearby river - Adiyan River. Consequently, water quality, river ecology and geomorphology of the immediate environment appear to have been affected. At Adiyan, the sediments are contributing to periodic flooding of a community road. In view of the above, the LUWSP requires the definition and implementation of appropriate sludge disposal measures at the two treatment plants. 1.2 Objectives of the Study The objectives of the study are to: (i) Analyse the current adverse impacts of the two treatment plants on nearby river and land uses. (ii) Define practical design and performance standards for treatment and disposal of sludge and wastewater from the plants that will eliminate plant- induced adverse effects on the receiving waters and related land uses; and (iii) Design a practical, costed program for improving the receiving waters to a condition similar to, and commensurate with, their condition upstream of the plant discharges. The above objectives are expected to be accomplished through the following: i. Desk and Field studies ii. Study of the hydrology, geomorphology quality and ecology of the receiving waters. I iii. Study of land uses related to the receiving waters. iv. Consultation with Lagos Water Supply Corporation (LWSC) officials, their engineering consultants and nearby community members. CHAPTER TWO 2.0 METHODOLOGY 2.1 Scope of Work The Scope of this work included environmental geochemistry, environmental geology, water resources/environmental engineering as well as ecology. 2.2 Research Approach As indicated under the objectives above, the general approach adopted in this work included. (i) Desk work (ii) Field studies and sampling (iii) Laboratory Analysis (iv) Evaluation of Results on the basis of the Terms of Reference vis-a-vis objectives of the study 2.2.1 Desk study Prior to the Field Studies and sampling, a one-day visit was made to the two plants at Adiyan and Iju as well as Akute for on-the-spot assessment of the current situation, identification of impacts as well as collection of baseline data. Physico-chemical data for the months of August, 2004 (Late rainy season), November, 2004 (Early dry season), January, 2005 (Late dry season) and April, 2005 (Early rainy season) were obtained from both Iju and Adiyan waterworks for evaluation as presented below. However, no data were available for the effluent. 2.2.2 Adiyan Waterworks (i) Colour 2 The colour of raw water arriving from Akute intake at Adiyan waterworks was observed to be far above that of the treated water throughout the year. Treated water was colourless with a zero hazen unit while raw water had a range of 100- 300 hazen units as shown in Fig. 2. 1. Fig. 2.1: Monthly-seasonal variation of colour in raw and treated water from Adiyan Waterworks 350 C 300 N 250' - - I 200 O 150 ,RA I "Ia , l . oETREATED 0 100 1 F ° 150' AUG NOV JAN APR Month-Seasun. (ii) Turbidity The turbidity of the treated water was zero while that of the raw water ranged between 60 andr 1o NTU. This difference was observed to be remarkable and significant (p<0.05). This trend was maintained throughout the year (Fig. 2.2). between 60 -/ eTREATED 20 { AUG NOV JAN APR Month-Season 3 Fig. 2.2: Monthly-seasonal variation of turbidity in raw and treated water from Adiyan Waterworks (iii) pH The pH of the raw water was found to be higher than that of treated water and this was observed to be remarkable only in the month of November as depicted in Fig. 2.3. 7 6 p)H3 3 ~~~~~ETREATED 0 AUG NOV JAN APR [YIDItII-Season Fig. 2.3: Monthly-seasonal variation of pH in raw and treated water from Adiyan Waterworks 2.2.3 Comparison of Water Quality from Iju and Adiyan Waterworks (i) pH The pH of water from both Iju and Adiyan Waterworks varied insignificantly (p>0.05) and were both within set standards for portable water pH (Fig. 2.4). 4 7 n 5 1)H 47 AUG NOV JAN APR r;lontli-seasoni Fig. 2.4: Monthly-seasonal variation of pH in treated water from Iju and Adiyan Waterworks in 2004-2005 (ii) Alkalinity Fig. 2.5 depicts month-seasonal variation in the alkalinity of water from both Ij'u and Adiyan Waterworks. From this figure, tt was observed that Iju Waterworks recorded higher alkalinity values than Adiyan Waterworks and this difference was significant (p<0.05), except the month of November when no value was given for Adiyan. Z, 25 20 4 L / __ 1 : l | * ADIYAN y. 10 AUG NOV JAN APP Month-Season Fig. 2.5: Monthly-seasonal variation of total alkalinity in treated water from Iju and Adiyan Waterworks in 2004-2005 iii. Hardness 5 I~~~~i.25dpcsmnhsaoa aitini h laiiyo ae rmbt j The hardness of water was observed to be higher at Iju than Adiyan Waterworks for the months of August to November 2004 and significant at 5% (p<0.05) confidence interval. Figure 2.6 shows the variation in hardness. 0 u 60 00 AUG NOV JAN APR M1onth-Season Fig. 2.6: Monthly-seasonal variation of total hardness in treated water from Iju and Adiyan Waterworks in 2004-2005. 2.3 Field Studies Armed with topographical maps of the project area i.e. Lagos Sheet 279, NE and SE, sample bags, sample bottles (plastic and glass), thermometer, conductivity meter bridge as well as digital pH meter, the field study was embarked upon. The report on the field study is as indicated in paragraphs 2.3.1 -2.3.7. 2.3.1 Location and Accessibility The "Project Area" is located north of Lagos between Latitudes 6°38'N and 6°43'N and Longitudes 3°17'E and 3°23'E and on Lagos Topo Sheet 279NE on a scale of 1:50,000 (Fig. 2.7). The Akute intake on River Ogun is located almost west of Iju Waterworks at a distance of 4.75 km. Both Iju Waterworks and Akute intake are located in Ogun State. I Adiyan Waterworks also in Ogun State is located north of Iju waterworks at a distance of about 2.8 km. The two waterworks discharge their sludge into the same Adiyan River but at different locations. Adiyan waterworks is about 750m from the Adiyan River (discharge point) while the Iju Waterworks is about 350 meters away from the Adiyan River (discharge point). The two waterworks as well as the Iju Intake on River Ogun are all accessible through tarred roads from either the Lagos State end (i.e. through Ikeja, Agege or Magodo) or through the Ogun State end (i.e. through Ifo South Local Government Area of Ogun State). All the roads leading to the "Project Area" are motorable throughout the year. 7 b~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4°E - N ';ER REPJ3LjIC AFIUJA A 0;-J ... N WA t X, + CA S >EFOlJN t. V .o 1 1 Ok-r / ] ~~SCA LE | °43 ,7E aI I Y E 3'20 E 3 21EC 3'2?E _ 3"23 \ , '4' 2 , * ' ; 3/ 6 4 . ; ,\ -- 'i At ~~~~~~~~~ 4' ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ V4 ~~~~~~~~~~~~~~~~ A f ~ ~ ~ ~ fI ~uUp Ac,s kOI~Q Ccmot ',. t'. Scho> s ScN . ~ 'h Cha ,, ~ ~ a map of the std a (A) J~~~~~ I~~~~~~~~~~~~~~~~~~~K BUWUp rcls ls.our5ro( CCPS s SC - ~ ) Sc C hu., C tvr Ma ( o Roi Ro c;ds Pah RO11,5 1.u1tu I i'nQ, Mg> and Fe> as well as the heavy metals Cu, Zn, Pb, As, Cd, Ni, Mn and Mo. To this group of water, one or two drops of concentrated nitric acid (con HNO3) were added. The other pairs of water samples collected in glass bottles were used for the determination of the physical parameters - colour, temperature, pH, dissolved oxygen (DO), hardness, conductivity; the chemical parameters like alkalinity, NH3-N, N03-N, P04-P. The cations and the heavy metals in the plastic bottles were analysed using Atomic Absorption Spectrophotometric method. The physical parameters as well as the chemical properties of the water samples in the glass bottles were analysed using the Standard methods of Lind (1977a); APHA (1980); Sterling (1985) as described below. 2.4.2 Plant Samples In all, eight (8) samples were collected for analysis. The samples comprised of banana leaves and water hyacinth from the Akute intake, plants (ferns) from the upstream of Adiyan river, plants (ferns) from the downstream of Adiyan river and at Adiyan bridge, plants (ferns) at the downstream of Adiyan river at Iju bridge, plants (ferns) at Iju sludge area, and another plants (banana leaves) at Akute area. All the plant samples were analysed to determine the level of concentration of the major elements and heavy metals: Na, K, Ca, Mg, Cu, Zn, Fe, Al, As, Mo, Mn, Hg and Ni. The concentration of the analysed elements were compared to that of the World average for plants as compiled by Vinogradov (1959); Taylor (1964); Bear (1964) and Bowen (1966). 2.4.3 Soil Samples Three soil samples including sludge were collected from Iju, Akute and Adiyan sludge. From these samples the following samples were analysed for: Na, K, Ca, Mg, Pb, Cu, Zn, Fe, As, Cd, Ni, Hg and Al. The results of the analysis were later compared with the world average for soil by Vinogradov, (1959); Taylor, (1964); Bear, (1964) and Bowen, (1966). 2.4.4 Life-Forms Samples Life-forms samples - phytoplankton, zooplankton and nekton in the water were collected. The life-forms samples were for the evaluation of primary productivity and potentiality for fish production. The evaluation was carried out by measuring the dissolved oxygen using the light and dark bottle technique. It 18 I was based on the principles of photosynthesis and respiration taking place in the light bottle and respiration in the dark bottle to compensate for the loss due to respiration in the light bottle. The gross oxygen produced is expressed as gramme oxygen produced per day. 2.5.0 Laboratory Analysis 2.5.1 Geochemical Samples All the samples (i.e. water, plants and soils) for geochemical analysis were analysed for the following heavy metals - Fe, Cu, Pb, As, Mn, As, Zn, Cd, Ni, and Mo after the normal digestion (plants and soils) using Atomic Absorption Spectrophotometer. 2.5.2 Ecological Samples For the ecological samples, the following physical parameters - Temperature, Transparency, Suspended solids (%) and Colour (in Hazen units) were measured as described below. Furthermore, the following chemical parameters pH, DO, Conductivity, Alkalinity, Hardness, NH3N, NON, PO4 and Cl were measured. Also heavy metals like lead, mercury, arsenic, nickel etc. were all measured. Standard methods according to Lind (1979), APHA (1980) and Stirling (1985) were employed as stated below: 2.5.2.1 Colour Colour was measured in Hazen Units using Lovibond Water-Test Kit. 2.5.2.2 Temperature Mercury bulb thermometer of 1 00°C capacity was used to measure both air and water temperature at sampling sites in the morning hours (9:00-11:00 a.m). 2.5.2.3 pH Calibrated pH paper with colour chart (0-14) was used to measure pH of water on the spot at the sampling points. 2.5.2.4 DO Dissolved Oxygen was measured titrimetircally using Standard Winkler Method (Lind, 1979; APHA, 1980; Stirling, 1985). Samples were fixed in the field and taken to the laboratory for further analysis. 19 I' 2.5.2.5 Hardness Standard method according to Lind (1979), APHA (1980) and Stirling (1985) was employed. Aliquot sample was taken, buffered in ammonia-buffer, titrated against diasodium salt of EDTA (Na2-EDTA) using Erichrome Black-T dye as indicator. 2.5.2.6 Conductivity The electrical conductivity of the water samples from the nine sites was measured using a conductivity meter of Kent model. The unit of measurement was in micro-siemen per centimeters, with a cell constant range of 1-2, and a provision for cell correction. Lead compensation was used with a cell constant setting of 1.0 as described in its manual and the aforementioned standard texts. 2.5.2.7 Alkalinity This is the buffering capacity of water to restore its integrity in terms of pH change. The alkalinity was measured titrimetrically as Total Alkalinity comprising Carbonate, Bicarbonate and Hydroxide Alkalinity. Titration of aliquot of water sample with methyl-orange indicator against a 0.O1M HCI to pink end point was carried out as described in the standard methods. 2.5.2.8 Ammonia-Nitrogen (NH,IN) This was determined using Lovibond Water Test Kit as described in its manual, using disc 3/113 on the comparator where water samples treated in Ammonia tablets 1 and 2 was cross-marched against untreated water samples and the marching number represented the amount of ammonia in mg/l. 2.5.2.9 Nitrate-Nitrogen (NOjN) The procedure is the same as for NH3-N except that Nitratest powder and disc 3/124 were used. 2.5.2.10 Phosphate Phosphorus (PO4 P) This was done spectrophotometrically as follows; 1Oml of vanadomolybdate reagent was added to 2.5ml of water sample, digested and made up to lOOml with distil water. Colour was allowed to develop for the next 30 minutes. Absorbance was read at 420nm. Absorbance of standards of phosphorus earlier read spectrophotometrically was plotted against concentration to obtain a calibration curve. Absorbance of samples treated as earlier described would be used to extrapolate concentration of phosphate phosphorus in the samples. 2.5.2.11 Mineral/Heavy Metals Determination Water samples fixed in aqua-regia was read off photometrically using an Atomic Absorption Spectrophotometer for calcium, magnesium, iron, copper, zinc, manganese and heavy metals using appropriate lamp while flame photometer was used for sodium and potassium determination using appropriate 20 filter. Standards prepared were treated as described for phosphorus to plot calibration curve, from where concentrations of minerals were extrapolated. 2.5.2.12 Suspended Solids This is a measure of solids in suspension in the water samples. It is otherwise a measure of insoluble solids. It is simply gravimetric in nature where weight of suspended solids is calculated as a percentage of water or concentration in mg/l. Sample particles were allowed to sediment completely, filtered and residues dried. Weight of dried residue is expressed as a percentage of water sample. 2.5.2.13 Total Dissolved Solids This was determined gravimetrically as for suspended solids except that the filtrate is evaporated to dryness leaving behind the dissolved solids. In practice, it is measured as total solids in water -both suspended and dissolved. It is a useful index of stock as morpho-edaphic index (M.E.I.) is a determinant of fish- stock. Aliquot of water sample was taken and evaporated to dryness. The weight of solids left behind was expressed as a percentage of that of water sample. 2.5.2.14 Primary Productivity This is a measure of phytoplankton in the rivers. It was measured by dissolved oxygen evaluation using the light and dark bottle technique. It was based on the principles of photosynthesis and respiration taking place in the light bottle and respiration only in the dark bottle to compensate for loss due to respiration in the light bottle. The gross oxygen produced is expressed as milligramme oxygen produced per litre per hour. 2.5.2.15 Morpho-Edaphic Index This was calculated using the formula below; M.E.I= ITDS/MD TDS = Total Dissolved Solids MD Mean Depth. 2.5.2.16 Sampling of Zooplankton Zooplankton net was towed three time and content of known volume emptied into sampling bottle. The content was fixed in 4% formalin and taken to the laboratory for examination. 21 I~~~~~~ Environmental Assessment Study of Lagos Water Corporation July 2005 CHAPTER THREE 3.0 RESULTS OF ALL LABORATORY ANALYSES The results of all the analysed samples (water, plants, soils and life forms) from both the geochemical and ecological points of view are as shown in Table 3.1 - 3.17 and their diagrammatic representations are as shown in Figs. 3.1 - 3.22 3.1 Geochemical Consideration 3.1.1 Water Analysis - Heavy metals The concentration of heavy metals in all the analysed water samples were generally below the WHO (2000) guideline values for these metals in drinking water. However, slightly higher concentrations of the elements (impact of the two plants) were recorded in samples SSW-03 (Adiyan Sludge water) and sample SSW-04 (Iju sludge water) when compared with other analysed water samples (see Table 3.1). 3.1.1.1 Iron (Fe) The concentration of Fe in all the analysed water samples varied between 0.1 ppm and 0.22ppm. The lowest concentration of 0.1 1ppm was recorded in Sample No. SSW-06 at Adiyan Intake, while the highest concentration of 0.22ppm was recorded in the sludge waters Sample No. SSW-03 (Adiyan) and Sample No. SSW-04 (Iju). The next high concentration of 0.2 lppm was recorded at the downstream sector of the Adiyan River. Although all the above concentrations are far below the WHO (2000), G.V of 0.3ppm for Fe in drinking water, the high concentration of Fe recorded in Samples No. SSW-03, SSW-04 and SSW-07 may be related to the impact of the two plants. Table 3.1: Distribution of heavy metals in the analysed water samples (All measurements in ppm) S/N Sample Sample Fe Cu Zn Pb As Cd Ni Mn Mo No. Location 1. SSW-01 Akute 0.16 0.025 0.005 0.05 0.02 0.005 0.50 0.20 0.006 Intake 2. SSW-02 Adiyan Cl 0.13 0.033 0.004 0.08 0.01 0.002 0.62 0.25 0.005 3. SSW-03 Adiyan 0.22 0.035 0.008 0.19 0.04 0.009 0.85 0.50 0.009 Sludge 4. SSW-04 Iju Sludge 0.22 0.091 0.012 0.22 0.05 0.008 0.92 0.62 0.010 5. SSW-05 Iju Intake 0.19 0.023 0.004 0.07 0.01 0.001 0.55 0.31 0.007 6. SSW-06 Adiyan 0.11 0.025 0.005 0.07 0.02 0.002 0.61 0.45 0.006 Intake 7. SSW-07 Adiyan R. 0.21 0.034 0.006 0.09 0.01 0.003 0.53 0.55 0.005 D-Stream 8. SSW-08 Adiyan R. 0.20 0.025 0.004 0.075 0.02 0.002 0.54 0.46 0.007 27 Environmental Assessment Study of Lagos Water Corporation July 2005 U-Stream 9. SSW-09 lju Clean 0.I8 0.021 0.005 0.08 0.02 0.003 0.55 0.43 0.006 Water 10. After WHO (2000) 0.3 2.0 3.0 0.01 0.01 0.003 0.02 0.5 0.5 3.1.1.2 Copper (Cu) The concentration of Cu in all the analysed water samples varied between 0.02 1pm and 0.04ppm. The lowest concentration of 0.021lppm was recorded in Sample No. SSW-09 (Jju clean water) while the highest concentration of 0.041ppm was recorded in Sample No. SSW-04 (Iju sludge water). All the above concentrations of Cu recorded in all the analysed water samples are below the WHO (G.V) for Cu in drinking water. However, the higher concentration of Cu recorded in sludge waters at Adiyan Sample No. SSW-03 (0.035ppm) and Iju - Sample No. SSW-04 (0.041ppm) may eb related to the two plants. Similarly, the high concentration of Cu (0.034ppm) recorded downstream of Adiyan may be equally be related to the two plants (as a result of discharged sludge water). 3.1.1.3 Zinc (Zn) The concentration of Zn in all the analysed water samples varied beween 0.004ppm and 0.01l2ppm. The lowest concentration of 0.004ppm was recorded in three samples - Sample No. SW-02 (Adiyan clean water), Sample No. SSW- 05 (Iju Intake) and Sample No. SSW-08 (Adiyan River Upstream). The highest concentration of 0.l2ppm was recorded in Sample No. SSW-04 (Iju sludge water). Compared to all other values of the analysed water samples, the concentration of Zn in Sample Nos. SSW-03 and SSW-04 were found to be highest, and these high values may not be unconnected with the wastewater from the plants. In spite of the above, the concentration in all the analysed water samples are below the WHO (2000) G.V of 3ppm for Zn in drinking water. 3.1.1.4 Lead (Pb) The concentration of lead in all the analysed water samples varied between 0.05ppm and 0.22ppm. The lowest concentration of 0.05ppm was recorded in Sample No. SSW-01 (Akute Intake) whilst the highest concentration of 0.22ppm was recorded in Sample No. SSW-04 (Iju sludge water). Furthermore another high concentration of 0. 09ppm was also recorded in Sample No. SSW- 03 (Adiyan sludge water). The very high concentration in the two water samples can be regarded as environmental impact related to the two plants at Adiyan and Jju. However, all the concentrations of Pb in all the analysed water samples are below the WHO (2000) G.V of 0.01 for Pb in drinking water. 3.1.1.5 Arsenic (As 28 I ~ ~~Tecnetaino edi l h nlsdwtrsmlsvre ewe Environmental Assessment Study of Lagos Water Corporation July 2005 The concentration of arsenic in all the analysed water samples varied between 0.Olppm and 0.05ppm. The lowest concentration was recorded in Sample No. SSW-05 (Iju Intake) and the highest concentration of 0.O5ppm as well as 0.04ppm were recorded in Sample No. SSW-04 (Iju sludge water) and Sample No. SSW-03 (Adiyan sludge water). When compared with the rest of the other analysed water samples, the high concentration of 0.04ppm and 0.O5ppm recorded in the sludge water samples can be related to the two plants at both Adiyan and Iju. However, all the other concentrations are within the WHO (G.V) of O.O lppm for arsenic in drinking water. 3.1.1.6 Cadmium (Cd! The concentration of cadmium in all the analysed water samples varied between 0.00lppm and 0.OO9ppm. The lowest concentration was recorded in Sample No. SSW-05 and the highest concentration of 0.OO9ppm were recorded in Sample No. SSW-03 (Adiyan sludge water). Iju sludge water (Sample No. SSW-04) also recorded a high concentration of 0.008ppm. These high concentrations recorded in the two water samples could be attributable to the two plants. All the other concentrations are within the WHO (G.V) of 0.003ppm for Cd in drinking water. 3.1.1.7 Nickel (Ni) The concentration of nickel in all the analysed water samples varied between 0.50ppm in Sample No. SSW-01 (Akute Intake) and 0.92ppm in Sample No. SSW-04 (Iju sludge water). The concentrations of nickel in all the analysed water samples were higher than the WHO (2000) G.V of 0.O5ppm for Ni in drinking. However, the very high concentrations of 0.85ppm in Sample No. SSW-03 (Adiyan sludge water) and 0.92ppm in Sample No. SSW-04 (Iju sludge water) could be attributable to the two plants. 3.1.1.8 Manganese (Mn) The concentration of manganese in all the analysed water samples varied between 0.20ppm and 0.62ppm. The lowest concentration of 0.20ppm was recorded in Sample No. SSW-01 (Akute Intake) while the highest concentration of 0.62ppm was recorded in Sample No. SSW-04 (Iju sludge water). Another high concentration of 0.55ppm was recorded in Sample No. SSW-07. The two high concentrations might be attributable to the two plants. Apart from these two concentrations, all the other concentrations recorded were below the WHO (2000) G.V. of 0.5ppm for manganese in drinking water. 3.1.1.9 Molybdenum (Mo) The concentration of molybdenum in all the analysed water samples varied between 0.005ppm and 0.0lOppm. The lowest concentration of 0.005pm was 29 Environmental Assessment Study of Lagos Water Corporation July 2005 recorded in Sample No. SSW-02 (Adiyan clean water) and Sample No. SSW-07 (Adiyan River Downstream). The highest concentration of 0.009ppm and 0.010ppm were recorded in Sample No. SSW-03 (Adiyan sludge water) and Sample No. SSW-04 (Iju sludge water). These high concentrations can be attributable to the two waterworks. There is for now, no guideline (G.V) set for Mo in drinking water by the World Health Organisation (WHO). 0.4 0O.2 Akute Adiyan Adiyan Adiyan Wju iju Iju River River WHO intake sludge intake clean sludge intake clean Adiyan Adiyan (2000) water water -down -up Fig. 3.1: Iron content of water 0.4 Akute Adiyan Adiyan Adiyan Iju iju Iju River River WHO intake sludge intake clean s ludge intake clean A diyan A diyan (2000) water water -down -op Fig. 3.2: Copper content of water 0.2 -~0. 1 0 Akaute Adiyan Adiyan Adiyaa Ije ija Ija River R ive r WHO intake sladge intake c leanf s ladge intake c lean A diyan A diyan (2 0 00) water water -do wn -up Fig. 3.3: Zinc content of water 30 Environmental Assessment Study of Lagos Water Corporation July 2005 0.3 -~- 0.2] 0.1 Akute Adiyan Adiyan Adiyan Iju iju Iju River River WHO intake sludge intake clean s ludge intake clean Adiyan A diyan (2000) water water -down -up Fig. 3.4: Lead content of water 0 . ) ~~~~~~~~~~~~~0 -l _ -_I T Akute Adiyan Adiyan Adiyan Iju iju 5ju River River WHO intake sludge intake clean sludge intake clean Adiyan Adiyan (2000) wa ter water -down -up Fig. 3.5: Arsenic content of water 0.1 -1 0.1 | 0 EL Akute Adiyan Adiyan Adiyan Iju iju lju River River WHO intake sludge intake clean sludge intake clean Adiyan Adiyan (2000) water water -doiw -up Fig. 3.6: Cadmiun content of water 31 I Environmental Assessment Study of Lagos Water Corporation July 2005 |~~~~ z ° Adyn - _ _0H Akute Adiyan Adiyan Adiyan Iju iju 5ju River River WHO intake sludge intake clean sludge intake clean A diyan Adiyan (2000) water water -do wn -up Fig. 3.7: Nickel content of water 1.. .5 0 5nflI Lfl Lii (2000)'f L Akute Adiyan Adiyan Adiyan Iju iju Iju River River WHO intake sludge intake clean sludge intake clean Adiyan Adiyan (2000 water water -down -up Fig. 3.8: Manganese content of water Fig. 3.9: Molybdenum content of water 0.2 &0.1 Akute Adiyan Adiyan Adiyan Iju iju Ij clean River River intake sludge intake clean sludge intake water Adiyan - Adiyan - water down up 3.1.2 Plant Analysis - Heavy Metals The concentration of heavy metals in all the analysed plant samples are generally below the world average for plants except molybdenum (Vinogradov, 1959); Taylor, (1904); Bear, (1964) and Bowen, (1966). Furthermore, no 32 Environmental Assessment Study of Lagos Water Corporation July 2005 specific concentration of specific element could be related to the impact of waterworks (see Table 3.2). Table 3.2: Distribution of heavy metals in the analysed plant samples (All measurements in ppm) S/N Sample Sample Location Fe Cu Zn As Mo Mn Hg Ni No. 1. SSP-01 Akute Hyacinth 45 6 20.55 nd 2.45 25.00 Nd nd 2. SSP-02 Akute (Banana) 49.92 7.45 19.06 nd 1.98 27.75 Nd nd 3. SSP-03 Akute (Banana) 51.62 8.12 21.52 nd 2.32 22.06 Nd nd 4. SSP-04 Iju (Fern) 52.40 9.10 25.02 nd 2.46 24.25 Nd nd 5. SSP-05 Iju (Fern) 60.12 8.56 21.62 nd 2.84 20.76 Nd nd 6. SSP-06 Akute 56.17 9.42 23.04 nd 2.95 24.92 Nd nd 7. SSP-07 Adiyan. 60.24 8.91 20.35 nd 2.84 29.96 Nd nd U-Stream 8. SSP-08 Adiyan 65.09 9.25 19.95 nd 2.79 30.08 Nd nd D-Stream I * 10000 200 900 30 20 7500 0.001 50 * After Vinogradov (1959), Taylor (1964), Bear (1964) and Bowen (1966) 3.1.2.1 Iron (Fe) The concentration of Fe in all the analysed plants samples varied between 45.00ppm and 65.09ppm. The lowest concentration of 45.00ppm was recorded in Sample No. SSP-01 (Akute Hyacinth) while the highest concentration of 65.09ppm was recorded in Sample No. SSP-08 (Fern at Adiyan River Upstream). From the above analyses, no pollution of iron in any of the samples could be established as the concentration of iron in all the plants are far below the world average. (Vinogradov, 1959); Taylor, (1904); Bear, (1964) and Bowen, (1966). 3.1.2.2 Copper (Cu) The concentration of Cu in all the analysed plant samples varied between 6.82ppm and 9.25ppm. The lowest concentration was recorded in Sample No. SSP-01 (Hyacinth plant from River Akute), while the highest concentration of 9.25ppm was recorded in Sample No. SSP-07 (Fern plant at the Upstream of River Adiyan). Like in the case of iron, no pollution of Cu could be established with the various plants leaves that could be associated with either Adiyan on Iju plants. Furthermore, the concentrations of Cu in all the plants are too much lower than the world average of 14ppm (Vinogradov, 1959); Taylor, (1904); Bear, (1964) and Bowen, (1966). 3.1.2.3 Zinc (Zn) The concentration of zinc in all the analysed plant leaves varied between 19.06ppm and 25.02ppm. The lowest concentration of 19.06ppm was recorded 33 Environmental Assessment Study of Lagos Water Corporation July 2005 in Sample No. SSP-02 (Banana Leaves at Akute Intake) while the highest concentration of 25.02ppm was recorded in Sample No. SSP-04 (Fern leaves at Iju waterworks environment. From the results of he analyses, it was difficult to establish pollution of the plant leaves that could be related to any of the two waterworks. In addition all the zinc values in the analysed plant leaves are below the world average of plants of lOOppm (Vinogradov, 1959); Taylor, (1904); Bear, (1964) and Bowen, (1966). 3.1.2.4 Manganese (Mn) The concentration of manganese in all the analysed plant leaves varied between 22.06ppm and 30.08ppm. The lowest concentration was recorded in Sample No. SSP-03 (Banana leaves at Akute Intake) whilst the highest concentration was recorded in Sample No. SSP-07 (Fern leaves at the Upstream of River Adiyan). All the recorded concentrations are below the world average of 630ppm for plants (Vinogradov, 1959); Taylor, (1904); Bear, (1964) and Bowen, (1966). In view of the above, no pollution of Mn in any of the leaves that could be related to the activities of the two waterworks. 3.1.2.5 Molybdenum (Mo) The concentration of molybdenum in all the analysed plant leaves varied between 1.98ppm and 2.84ppm. The lowest concentration of 1.98ppm was recorded in Sample No. SSP-02 (Banana leaves at Akute Intake), while the highest concentration was recorded in Samples No. SSP-05 (Fern leaves at Iju bridge) and Sample No. SSP-06 (Fern leaves at the Downstream sector of River Adiyan). Generally, there seemed to be an enrichment of molybdenum in all the analysed plant leaves as all the recorded values were above the world average value of molybdenum of 0.90ppm, (Vinogradov, 1959); Taylor, (1904); Bear, (1964) and Bowen, (1966). 34 I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Environmental Assessment Study of Lagos Water Corporation July 2005 80 -- 60 2 0]2 - Akule Akue Akute Iju (Fern) Iju (Fe n) Akule Adiya. U- Adiyan D- (Hyacinth) (B anana) (B anana) stream stream Fig. 3.10: Iron content of plant tissue 10 . 60 Ak.le Akute Ak.te Iju (Fern) lIa (Fer-) Akute Adiyan U- Adiyan D- (Hyacinth) (B anana) (Banana) stsre m stream Fig. 3.11: Copper content of plant tissue 30 E~ 1 5 Akute Akule AkAkule Addiyan U-A - (Hyacinth) (Banana) (B anana) steam siream Fig. 3.12: Zinc content of plant tissue 35 Environmental Assessment Study of Lagos Water Corporation July 2005 4 0 2 01. _ HF1... . .. ... ',20 I I _ _ l_ 1 Akute Akule Aku k u (Fern) Iju Fa ) Ak.te Adiyan U- Adiyan D- (Hyacinth) (Banana) (Banana) stream stream Fig. 3.13: Manganese content of plant tissue 3 - - 0~ Akule Akute Akule lj. (Fern) Iju (Fern) Akute Adiyan U- Adiyan D- (H4yacinth) (Ban... (Banana) stre stream Fig. 3.14: Molybdenium content of plant tissue 3.1.3 Soil Analysis - Heavy Metals The concentration of heavy metals in all the analysed soil samples are generally below the world average for soil with the exception of copper/ cadmium and mercury. When compared with other soil samples, Adiyan sludge sample indicated plant-induced enrichment of all elements except iron (see Table 3.3). Table 3.3: Distribution of heavy metals in the analysed soil samples (All measurements in ppm) S/N Sample Sample Fe Cu Zn Pb As Cd Ni Hg No. Location I 1. SSS-01 Iju 80 100 60 60 20 30 200 1 2. SSS-02 Akute 60 120 50 70 1 0 35 210 1 3. SS3-03 Adiyan 40 150 100 120 - 30 38 240 3 l* _ Sludge 550,000 100 300 200 40 - 0.7 1000 0.3 * Maximum values in soil (After Vinogradov 1959; Taylor, 1964; Bear, 1964 and Bowen, 1966) 3 6 Environmental Assessment Study of Lagos Water Corporation July 2005 3.1.3.1 Iron (Fe) The concentration of iron in all the analysed soil samples varied between 40ppm and 80ppm. The lowest concentration of 40ppm was recorded in Sample No. SSS-03 (Adiyan sludge sample) while the highest concentration of 80ppm was recorded in Sample No. SSS-01 (Iju Soil Sample). All the iron concentrations are far below the world average of 550,000ppm for iron (Vinogradov, 1959); Taylor, (1904); Bear, (1964) and Bowen, (1966). 3.1.3.2 Copper (Cu) The concentrations of copper in all the analysed soil samples are generally high and varied between lOOppm and 150ppm. The lowest concentration of lOOppm was recorded in Sample SSS-01 (Iju soil sample) while the highest concentration of 150ppm was recorded in Sample No. SSS-03 (Adiyan sludge sample). With the exception of Sample No. SSS-01, with a concentration of lOOppm, all other samples had values between 120ppm and 150ppm and these values were higher than the world soil average of lOOppm for Copper (Vinogradov, 1959); Taylor, (1904); Bear, (1964) and Bowen, (1966). Furthermore, plant induced enrichment for Copper could be established in Sample No. SSS-03. 3.1.3.3 Zinc (Zn) The concentration of zinc in all the analysed soil samples varied between 50ppm and lOOppm. The lowest concentration of 50ppm was recorded in Sample No. SSS-02 (Akute soil sample) while the highest concentration of lOOppm was recorded in Sample No. SSS-03 (Adiyan sludge).All the recorded concentrations were below the world average of 300ppm for zinc Vinogradov, (1959), Taylor (1964), Bear (1964) and Bowen (1966). Considering the above, impact of Adiyan plant soil could be established considering the highest concentration of zinc in all the soil samples. 3.1.3.4 Lead (Pb) The concentration of lead in all the analysed soil samples varied between 60ppm and 120ppm. The lowest concentration of 60ppm was recorded in Sample No. SSS-Ol(Iju soil), while the highest concentration of 120ppm was recorded in Sample No. SSS-03 (Adiyan sludge). Although each of the analysed soil has concentration below the world average of 200ppm for lead in soil, an impact of the plant on the enrichment of lead in Adiyan could be established. 3.1.3.5 Arsenic (As) 37 Environmental Assessment Study of Lagos Water Corporation July 2005 The concentration of arsenic in all the analysed soil samples varied between lOppm and 30ppm. The lowest concentration of lOppm was recorded in Sample No. SSS-02 (Akute soil) whilst the highest concentration of 30ppm was recorded in Sample No. SSS-03 (Adlyan sludge). Although the concentration of arsenic in each of the analysed samples is lower than that of world average of 40ppm for soil (Vinogradov, 1959); Taylor, (1904); Bear, (1964) and Bowen, (1966). However, evidence of impact of Adiyan plant could be established regarding the arsenic content of its sludge/soil. 3.1.3.6 Cadmium (Cd) The concentration of cadmium in each of the analysed soil samples seemed to be extremely higher than the world average of 0.7ppm for soil by a factor of between 40 and 50. In all the analysed soil samples, the concentration of cadmium varied between 30ppm and 38ppm. The lowest concentration of 30ppm was recorded in Sample No. SSS-01 (Iju soil) and the highest concentration of 38ppm was recorded in Sample No. SSS-03 (at Adiyan). Like in the case of arsenic the highest concentration of cadmin in Sample No. SSS-03 could be attributable to the Adiyan plant. 3.1.3.7 Nickel (Ni) The concentration of nickel in the analysed soil samples varied between 200ppm and 240ppm. The lowest concentration of 200ppm was recorded in Sample No. SSS-01 (Iju soil) while the highest concentration of 240ppm was recorded at Adiyan. All the above concentrations were much lower than the world average of lOOOppm of Ni for soil (Vinogradov, 1959); Taylor, (1964); Bear, (1964) and Bowen, (1966). 3.1.3.8 Mercury (Hg) The concentration of mercury in all the analysed soil samples of the Project Area varied between lppm and 3ppm. The lowest concentration of lppm was recorded in Sample No. SSS-01 (Iju) and Sample No. SSS-02 (Akute), while the highest concentration of 3ppm was recorded in Sample No. SSS-03 (Adiyan). All the analysed soil samples have mercury concentration were higher than the world average by a factor of between 3 and 30 respectively. As indicated earlier in other heavy metals, the high concentration of 3ppm in Adiyan (Sample No. SSS-03) could be attributable to the Adiyan waterworks. 38 Environmental Assessment Study of Lagos Water Corporation July 2005 1000 - E 6D00 600- C)400~ 200 - 0 l l__ Iju Akute Adiyan sludge Max. allowble Fig. 3.15: Iron content of soils 150~ ~100~ 0- Iju Akute Adiyan sludge Max. allowable Fig. 3.16: Copper content of soils -~150I 0 L I~~~~ju Akute Adiyan sludge Max. allowable Fig. 3.17: Zinc content of soils 39 I Environmental Assessment Study of Lagos Water Corporation July 2005 200~ g 1001 C- L Iju Akute Adiyan sludge Max. allowable Fig. 3.18: Lead content of soils 50 1 E &25 Iju Akute Adiyan sludge Max. allowable Fig. 3.19: Arsenic content of soils 40 - -----_ ,e 20 - ~l0 L I~~~~ju Akute Adiyani sludge Max. allowable Fig. 3.20: Cadmium content of soils 40 Environmental Assessment Study of Lagos Water Corporation July 2005 1000 3 500 lju Akute Adiyan sludge Max. allowable Fig. 3.21: Nickel content of soils 4 - 4 --~... .. .. .. 1 32- Iju Akute Adiyan sludge Max. allowable Fig. 3.22: Mercury content of soils 3.1.4 Environmental Implications From the geochemical point of view, it has been established that enrichment of some heavy metals in water, plants and soils could be related to the two plants at Adiyan and Iju as environmental impact/implication. These implications could not be ascertained on the community unless the blood of individual member of the community is examined for the level of each of the heavy metals in their blood. However, this aspect of research is outside the scope of this study. The major environmental implication of the two plants on the nearby river in the siltation of the river beds caused by inadequate functioning of the major parts of the plants such as the pumps, sedimentation beds as well as the filtration beds from which about four had completely broken down. If all these have been functioning well, there will be less wastewater generated and the sludge so generated will be reduced to the barest minimum. 3.1.5 Mitigation Measures 41 lI Environmental Assessment Study of Lagos Water Corporation July 2005 From the above implication, there are two foreseeable mitigation measures to arrest the flooding of the nearby river as a result of the impact of the two waterworks on the environment. These are: i) Dredging of River Adiyan from its Upstream sector after the discharge point of wastewater from Adiyan Plant down to the Downstream sector after the discharge point of wastewater from the iju Plant. This measure will remove the silt and the weed covering River Adiyan within this regime and thereby allowing free flow of River Adiyan. (ii) Rehabilitation of the two plants by providing new pumps, sedimentation beds as well as filtration beds. This measure allow the reduction in the wastewater generated as well as reduction in the sludge vis-w-vis silt discharged into the nearby River Adiyan. 3.2.0 Ecological Considerations 3.2.1 Comparative study of River Ogun at Akute Intake, River Adiyan Upstream and River Adiyan Downstream 3.2.1.1 Physical Characteristics The result of the physical characteristics are shown in Table 3.4. The physical characteristics of River Ogun supplying Akute Intake is that of a river in its middle course. The water was turbid mainly due to total dissolved solids with low transparency. The colour of the water was light milky. The physical characteristics of water samples at River Adiyan indicate higher water temperature at downstream than upstream. The colour of water was light-milky to brown-milky at both upstream and downstream respectively. Suspended solids level was higher at downstream than upstream and this was the order for the total dissolved solids. Transparency was under Im at both locations. The odour of water from Adiyan downstream indicated abnormality. Table 3.4: Physical characteristics of water at Akute Intake, River Adiyan Upstream and River Adiyan Downstream Characteristics Akute Intake Adiyan Adiyan FEPA/WHO Upstream Downstream Standards Air Temp (°C) 36a 35a 36a Water Temp (°C) 34a 34a 36b 20-35 Tranparency (m) 0.5a 0.5a 0.5a NA Suspended Solids (%) Oa Oa 5b NA Total Dissolved 0.03a 0.06b 0.09c 500 Solids (%) 42 Environmental Assessment Study of Lagos Water Corporation July 2005 Colour 10a 1Oa 1Oa 5 (Hazen Units) Odour Free from Free from Not free from Free from abnormality abnormality abnormality abnormality NA=Not Available Raw data with the same letter do not differ significantly from each other (p>0.05). 3.2.1.2 Chemical Characteristics The results of the chemical characteristics are as shown in Table 3.5. The chemical characteristics of water samples from Akute Intake indicating high levels of dissolved oxygen, conductivity, alkalinity and hardness. These were observed to be significantly higher than the levels at River Adiyan (p<0.05). Ammonia-nitrogen and nitrate-nitrogen levels were generally low. There was insignificant difference in the hardness of water from both upstream and downstream Adiyan (p>0.05) while alkalinity was significantly higher upstream than downstream (p<0.05). Table 3.5: Chemical characteristics of water at Akute Intake, River Adiyan Upstream and River Adiyan Downstream Characteristics Akute Adiyan Adiyan FEPA/WHO Intake Upstream Downstream Standards pH 7.Oa 7.Oa 6.5a 6.5-9 DO 7.6b 4.0a 3.6a 3-7 Conductivity 0.5a 0.5a 0.5a NA (uS/cm) Alkalinity 64.8b 47.3b 27.4a 200 (mg/l) Hardness 47.2b 16.0a 16.Oa 300 (mg/l) NH3-N (mg/I) Oa Oa Oa 100 N03-N (mg/l) 0. la 0. la O.la NA P04-P (mg/l) ND 0.02a 0.55b 0.0 Cl[(mg/l) ND ND ND 200 Raw data with the same letter do not differ significantly from each other (p>0.05). 3.2.1.3 Mineral and Heavy Metals The result of the mineral and heavy metals are as shown in Table 3.6. Mineral contents of water samples showed significant variation amongst the three locations (p<0.05). Minerals of groups I & II elements were found to be highest 43 Environmental Assessment Study of Lagos Water Corporation July 2005 Upstream Adiyan while both Upstream and Downstream Adiyan were higher than Akute Intake for iron, copper, aluminum, lead and manganese. Table 3.6: Mineral and Heavy Metals Content of Akute Intake, River Adiyan Upstream and River Adiyan Downstream Mineral/Heavy Akute River River FEPA/WHO Metal Intake Adiyan Adiyan Standards Upstream Downstream K 12.00 20.14b 14.62a NA Na 18.00 25.06 18.55a 200 Ca 20.00 25.00 20.00a 75-200 Mg 24.00 28.00 26.00b 50-150 Fe 0.16 0.20 0.21b 0.3 Cu 0.025 0.025 0.034 2.0 Zn 0.005 0.004 0.006a 1.0 Al 2.50 5.42 6.19 NA Pb 0.05 0.075 0.07 0.05 As 0.02 0.02 0.01a 0.01 Cd 0.005 0.002 0.003 0.01 Ni 0.50 0.54 0.56 0.05 Mn 0.20 0.46 0.55 0.05 Mo 0.006 0.007 0.005 NA NA=Not Available Data in the same row carrying different letters differ significantly from each other (p<0.05) 3.2.2. Primary Productivity The result of the primary productivity evaluation is as shown in Table 3.7. Upstream and Downstream samples of River Adiyan indicated high impact of sludge on the productivity of the river. Primary productivity of the river upstream was significantly higher than that of downstream. When compared to Akute Intake, it was highest at Akute and lowest at River Adiyan-downstream as presented in Table 3.7. Table 3.7: Primary productivity of Ogun River, River Adiyan Upstream and River Adiyan Downstream Primary River Ogun at River Adiyan River Adiyan Productivity Akute Intake Upstream Downstream 44 l Environmental Assessment Study of Lagos Water Corporation July 2005 Carbon Fixed 0.62b 0.50b 0.25a (mg/litre/hr) Energy Fixed 6.1 5b 4.92b 2.46 (kcal/litre/h) Data in the same row carrying different letters differ significantly from each other (p<0.05) 3.2.3 Morpho-edaphic Index (M.E.I.) The result of the M.E.I. evaluation is as shown in Table 3.8. Fish productivity as a function of morpho-edaphic index when water depth is brought into consideration shows that River Adiyan downstream does not differ significantly from River Adiyan upstream. Table 3.8: Morpho-edaphic Index of water from River Ogun at Akute and River Adiyan River Ogun at River Adiyan River Adiyan Akute Intake Upstream Downstream TDS(%) 0.03a 0.06b 0.09c M.E.I. 0.2a 0.3a Data in the same row carrying same letter do not differ significantly from each other (p>0.05) 3.2.4 Flora and Fauna The results of the flora and fauna evaluation are as shown in Table 3.9. Table 3.9 shows that at the Akute intake, water hyacinth (Eichornia crassipes) was the dominant aquatic vegetation, particularly as the bankroot biotope. Phytoplankton was non-existence as no algal colouration was observed. Zooplankton prevalence was evident but low. There was record of cichlid fishes especially the Nile tilapia (Oreochromis niloticus). 3-4 fishermen were observed fishing using dug-out canoes. Shell-fish represented by shrimps were observed as by-catches in the canoes of the fishermen. River Adiyan downstream showed the presence of ferns characteristic of a silted riverbed. Some ferns were equally observed upstream indicating other sources of siltation apart from discharge 45 Environmental Assessment Study of Lagos Water Corporation July 2005 from the Adiyan Waterworks. No record of phytoplankton indicated by the absence of algal colouration. Zooplankton presence was evident but low. Some cichlid fishes especially the Nile tilapia were found observed. Spats of gastropod molluscs were observed. Table 3.9: Flora and fauna composition of River Ogun and River Adiyan Flora/Fauna Group/Taxon River Ogun River River Adiyan at Akute Adiyan Downstream Intake Upstream _ ___ Phytoplankton Spirogyra sp x x x and related algae Zooplankton Rotifers x x x Ostracods x x x Cladocera x x x Copepods x x Worms Roundworms x X - Aquatic Eichornia X x Macrophytes crassipes Ferns x 'I Fin-Fish Oreochromis 1 x i niloticus Shell-fish Shrimp x x Gastropod x x i spat X -Not Observed 7I -Observed Human activities were observed Akute on River Ogun but this was observed to be more pronounced on River Adiyan at upstream and downstream from the discharge point at Adiyan Waterworks. These range from domestic, commercial, agricultural to industrial, in decreasing order of impact magnitude. Residential houses were within the vicinity of River Ogun and catchment of River Adiyan. Table 3.10 presents a checklist of human activities on the rivers. Table 3.10: Record of human activities and sources of pollutants in and around Rivers Ogun and River Adiyan 46 Environmental Assessment Study of Lagos Water Corporation July 2005 Activity Activity River Ogun River River Adiyan Group at Akute Adiyan Downstream Intake Upstream Domestic Washing x Activity Commerce Hawking x -'1 Agriculture Crop -'1 - Farming Industry Waterworks - x - Water x -"i Packaging Construction x - works Recreation Swimming x - x X -Not Observed 4 -Observed 3.2.5 Comparative Study of Iju and Adiyan Waterworks The Iju waterworks is located on the bank of River Adiyan at Iju town. Water entering the waterworks comes from Akute Intake via delivery water-pipes. The water at this point shares characteristics of water at Akute Intake. The water treatment plant is comprised of Vertical Sedimentation Tank, Horizontal Sedimentation Tank, Old Gravity Filtration Tank and New Gravity Filtration Bed, Post Chlorination Point, Underground Clean Water Tank and Sewage Treatment Plant. The Adiyan Waterworks is also located on the bank of River Adiyan at Adiyan town. The treatment plant is comprised of the Sedimentation Tank, Filtration Tank and two Surface Clean Water Tanks of 500,000 cubic metres of water each. Water samples taken at this plant were clean water (treated water), sludge and wastewater. In addition, water samples were also taken upstream and downstream River Adiyan from the point of discharge from Adiyan Waterworks. 3.2.5.1 Physical Characteristics of Clean Water from Iju and Adiyan Waterworks 47 Environmental Assessment Study of Lagos Water Corporation July 2005 The results of the physical characteristics measured are as indicated in Table 3.11. The physical analysis of the samples as in Table 5a indicated that the clean water (treated water) was colourless and odourless from both waterworks. There was near zero suspended solids and total dissolved solids with a near 100% transparency of the clean water. These were observed to conform with standards as they vary insignificantly with standard values (p >0.05). Table 3.11: Physical characteristics of clean water from Iju and Adiyan Waterworks Physical Iju Waterworks Adiyan FEPA/WHO Characteristics Waterworks Standards Air Temp °C 34a 34a Water 32a 34a 20-35 Temperature (°C) Transparency (m) 100a 100a NA Suspended I a Oa NA Solids (%) Total Dissolved 0.03a 0.03a 500 Solids (%) Colour 5a 5a 5 (Hazen Units) Odour Free from Free from Free from abnormality abnormality abnormality Data in the same row carrying same letter differ insignificantly from each other (p>0.05) 3.2.5.2 Chemical Characteristics of Clean Water from Iju and Adiyan Waterworks The chemical characteristics of clean water from both plants indicate a neutral pH , high level of dissolved oxygen. Hardness and alkalinity were generally moderate. There was absence of ammonia-nitrogen and a near zero nitrite- nitrogen, Chloride could be in trace amount as presented in Table 3.12. 48 I . .** * Environmental Assessment Study of Lagos Water Corporation July 2005 Table 3.12: Chemical characteristics of clean water from Iju and Adiyan Waterworks Chemical Iju Adiyan FEPA/WHO Characteristics Waterworks Waterworks Standards PH 7.Oa 7.Oa 6.5-9 DO (mg/I) 12a lOa 3-7 Conductivity 273a 265a NA (uS/cm) Alkalinity 37.4a 34.9a 200 (mg/l) Hardness 41.6a 46.4a 3001 (mg/l) NH3-N (mg/I) Oa Oa 1001 N03-N (mg/l) O.la O.la 100 P04-P (mg/i) ND ND 0.1 Cl- (mg/l) Trace Trace 200 Data in the same row carrying same letters do not differ significantly from each other (p>005) 3.2.5.3 Mineral and Heavy Metals Content of clean water from Iiu and Adiyan Waterworks The clean water samples from Iju and Adiyan Waterworks were observed to contain some mineral elements including heavy metals. Minerals found in water samples from the two stations varied insignificantly (p>0.05) except for sodium that was higher at Adiyan than Iju Waterworks. The minerals were found (Table 3.13) to be below maximum allowable limit for clean water, except for nickel and manganese whose levels were at least five times the limit. Table 3.13: Mineral and Heavy Metals Content of clean water from Iju and Adiyan Waterworks Mineral/Heavy Iju Clean Adiyan Clean FEPA/WHO Metal Water Water Standards K 18.50a 19.00a NA Na 17.55a 25.70b 200 49 Environmental Assessment Study of Lagos Water Corporation July 2005 Ca 22.Oa 18.00a 75-200 Mg 24.00a 22.00a 50-150 Fe 0. 18a 0. 13a 0.3 Cu 0.021a 0.033a 1 Zn 0.005a 0.004a 1.0 Al 4.55a 3.AdiOa NA Pb 0.08a 0.08a 0.05 As 0.02a 0.Ola 0.01 Cd 0.003a 0.002a 0.01 Ni 0.55a 0.67a 0.05 Mn 0.43a 0.25a 0.05 MO 0.006a 0.005a NA NA=~Not Available Data in the same row carrying same letter differ insignificantly from each other (p>0. 05) 3.2.5.4 Physical Characteristics of Sludge from Iju and Adiyan Waterworks Physical characteristics of sludge from both locations differed remarkably from clean water with respect to colour and odour, except temperature. Suspended solids and total dissolved solids levels are higher in sludge from Adiyan Waterworks than Jju Waterworks. The sludge from both locations was milky- brown and odour not free from abnormality (Table 3.14). Table 3.14: Physical characteristics of sludge from Iju and Adiyan Waterworks Physical Iju Waterworks Adiyan FEPA/WHO Characteristics Waterworks Standards Air Temp 'C 32a 34a Water 34a 35a 20-35 Temperature (0C) Transparency (n) Ga Oa NA Suspended Solids 3a 0b NA Total Dissolved 0.28a 1.18b 500 Solids Colour 45a 10a 5 (Hazen Units) Odour Free from Free from Free from 50 Environmental Assessment Study of Lagos Water Corporation July 2005 abnormality abnormality abnormality Data in the same row carrying different letters differ significantly from each other (p<0.05) 3.2.5.5 Chemical Characteristics of Sludge from Iju and Adiyan Waterworks The chemical characteristics of the sludge indicated moderate alkalinity, higher at Iju than Adiyan waterworks. Hardness was generally low but sludge from Adiyan was higher than that of Iju. Ammonia-nitrogen and nitrate-nitrogen were generally low within standard limits. Chloride was not detectable and reported in trace amount since chlorination was on at Iju Waterworks but not at Adiyan Waterworks (Table 3.15). Table 3.15: Chemical characteristics of sludge from Iju and Adiyan Waterworks Chemical Iju Adiyan FEPA/WHO Characteristics Waterworks Waterworks Standards PH 6.0a 7.0a 6.5-9 DO (mg/I) 9.2b 2.4a 3-7 Conductivity 270a 265a NA (uS/cm) Alkalinity 29.9a 24.9a 200 (mg/I) Hardness 40a 45.2a 300 (mg/l) NH3-N (mg/l) Oa Oa 100 N03-N (mg/I) O.la O.la 100 P04-P (mg/l) ND ND 0.01 ClF (mg/I) Trace Trace 100 NA=Not Available Data in the same row carrying different letters differ significantly from each other (p<0.05) 3.2.5.6 Mineral and Heavy Metals Content of sludge from Iju and Adiyan Waterworks Minerals found in sludge samples from the two stations varied insignificantly (p>0.05) except for potassium that was higher at Iju than Adiyan Waterworks. The minerals were found to be below maximum allowable limit for natural 51 Environmental Assessment Study of Lagos Water Corporation July 2005 water, except for lead, arsenic, nickel and manganese whose levels were at least three times the limit (Table 3.16). Table 3.16: Mineral and Heavy Metals Content of sludge from Iju and Adiyan Waterworks (All measurements in ppm) Mineral/ Iju Adiyan FEPA/WHO Heavy Sludge Sludge Standards Metal ___ _ K 22.00b 15.00a NA Na 54.40a 50.40a 200 Ca 50.00a 48.00a 75-200 Mg 49.50a 52.00a 50-150 Fe 0.22a 0.22a 0.3 Cu 0.041a 0.035a 1 Zn 0.012a 0.008a 1.0 Al 9.21a 7.80a NA Pb 0.22a 0. 19a 0.05 As 0.05a 0.04a 0.01 Cd 0.008a 0.009a 0.01 Ni 0.92a 0.85a 0.05 Mn 0.62a 0.50a 0.05 Mo 0.OlOa 0.009a NA NA = Not Available Data in the same row carrying different letters differ significantly from each other (p<0.05) 3.2.6 Environmental Impacts The impacts of the activities of the Lagos Water Corporation at Akute Intake, Iju and Adiyan Waterworks from ecological view-point can be divided into Associated Impacts and potential impacts as shown in Table 3.17 below. Table 3.17: Summary of Identified Impacts at Akute Intake, Iju and Adiyan Waterworks. Location Activity Associated Potential Impact Impact Impact Classification Akute Intake Construction Earth Loss of aquatic Negative of Weir Movement lives Change of Change in Negative Ecosystem to biodiversity and 52 Environmental Assessment Study of Lagos Water Corporation July 2005 semi- species lacustrine composition Clearing of Change in Navigation by Positive Aquatic water-flow fishermen and Weeds and freeing aquatic of waterway organisms improved Exposure to Increase in Positive atmosphere primary and and solar zooplankton radiation productivity leading to (aquatic increase in productivity) temperature and aeration. Water Reduction in Loss of aquatic Negative Uptake water volume lives -not significant relative to the river volume Iju Treatment of Improvement Sustainance of Positive Waterworks Raw-water of water human lives quality for human consumption Disposal of Earth Soil degradation Negative Solid Wastes Movement and pollution as landfill Sludge Flooding of Change in Negative discharge the biodiversity as into River immediate organisms are Adiyan at Iju environment, dislodged form Silting of the erosional riverbed biotope and new live forms emerged in the depositional biotope - sited riverbed Pollution from Negative sludge biomass 53 Environmental Assessment Study of Lagos Water Corporation July 2005 Eutrophication Negative of the river River blockade Adiyan Treatment of Improvement Sustenance of Positive Waterworks Raw-water of water human lives quality for human consumption Disposal of Earth Soil degradation Negative Solid Wastes Movement and pollution as landfill Sludge Flooding of Change in Negative discharge the biodiversity as into River immediate organisms are Adiyan at environment, dislodged form Adiyan Silting of the erosional riverbed biotope and new live forms emerged in the depositional biotope - sited riverbed Pollution from Negative sludge biomass Eutrophication Negative of the river l ___________ ____________ ____________ River blockade N egative 3.2.7 Mitigation Measures These can be divided into short-term and long-term, routine and non-routine mitigation measures. Long-term measures should address the physical dredging of the River Adiyan from Upstream Adiyan to Downstream Iju to facilitate free flow of sludge discharged into the river. 54 Environmental Assessment Study of Lagos Water Corporation July 2005 Reconstruction and maintenance of filtration-bed and sedimentation tank will guarantee less wastes into the river during discharge. Solid wastes treatment plant be reactivated to take care of solid wastes in wastewater before discharge. CHAPTER FOUR 4.0 ENGINEERING CONSIDERATIONS 4.1 The Waterworks 4.1.1 Introduction The Lagos Water Corporation has a water intake system at Akute on Ogun River, and two water treatment plants at Adiyan and Iju. Figure 2.7 shows the location of the treatment plants. The Iju treatment plant started operation in 1904, then water was abstracted directly from River Adiyan. By 1953, an intake system at Akute on River Ogun was commissioned. The intake system supplements the raw water to the Iju plant. There was a major expansion on the Akute intake system in 1972, and by 1994, the Iju plant depended solely on the water from Akute intake. The Adiyan plant was commissioned in 1991 to produce 72 MGD (million gallons per day) of water, while that of Iju has a capacity of 48 MGD. 4.1.2 Akute Intake on River Ogun 4.1.2.1 Hydrology of the Ogun River River Ogun (Figure 2.7) is fed by rivers originating from the Yoruba highlands. It flows slowly from north to south into the Lagos lagoons before discharging through creeks and swamps into the Atlantic Ocean. The approximate surface area of the basin is 2,237,000 ha. 4.1.2.2 Operation of the Intake System The intake system is located on River Ogun in Akute town of Ogun State. The intake system for Adinya has a capacity of abstracting 72 MGD of water, while that of Iju has a capacity of 48 MGD. Prior to 1996, the pumps take water directly from the river, but by 1996 a weir, which is one metre above sea level 55 Environmental Assessment Study of Lagos Water Corporation July 2005 was constructed across the river. The function of the weir is to stabilise the flow into the intake system, and prevent backflow of water during periods of low flow, especially between December and March. It was reported that water from the sea flows into the system during the dry months of 1983 (the Sahelian drought period). The weir has an advantage of preventing the re-occurrence of this phenomenon. The intake system for Adiyan plant has 5 pumps each having a capacity of 24 MGD. Two of the pumps serve as standby. The intake system for Iju has two types of pumps (12 and 6 MGD sizes). There are 5 and 4 numbers of the respective type, with two of each type as standby. At present, the intake system to Iju plant is operating at 40% while that of Adiyan is operating at 60%. The low utilisation capacity is attributed to a number of reasons, namely: * Non-functioning pumps. At present, none of the intake systems has a standby pump system, which means that when a pump is faulty, the unit is out of the system. * lack of spare parts for the broken-down components, and * epileptic power supply. The electricity supply from the National Electric Power Authority has been unreliable. 4.1.2.3 Maintenance of the Intake System The Ogun River is infested by weed due to human activity along the river bank. The management of the Akute intake system in collaboration with the community of the catchment work together in removing this deadly weed. The community, in particular the fishermen, clears the areas downstream and upstream of the intake system, while the management of the intake system clears the 500 metres length of the portion of the river which forms the intake system. The benefits of the maintenance includes: abstraction of water from the system without obstruction, free flow of water in the river thereby reducing water-bome disease, reduction in the risk of bank overflow during period of peak flow. Environmental issues raised recently include the following:- (i) change in colour of water in the river at the intake, suggesting that there was an industrial pollution upstream of the plant, (ii) (ii) flooding of flood plain downstream of the intake system, especially in August 2004. The level of water in the river depends on the rainfall contribution within the catchment. 56 Environmental Assessment Study of Lagos Water Corporation July 2005 4.2.0 The Water Treatment Plants There are two Water treatment plants now operational under the Lagos Water Corporation in the Project Area. They include the Adiyan and the Iju Water treatment plants respectively. 4.2.1 The Adiyan Water Treatment Plant The Adiyan plant was commissioned in 1991 to treat 72 MGD of water. The plant receives water from Akute Intake via a ductile iron pipe. The raw water moves via the alum dosing unit to the clarifier unit and then to the filtration bed. Appropriate dose of lime and chlorine are added to the filtered water. The sludge from the clarifier and filtration bed (during backwashing) is discharged via conduit and open channels to the Adiyan River. Plate 4.1 shows the wastewater flowing in an open channel within the Mobolowaduro - Mopara community, just before the canal discharge to the river. Plate 4.2 shows the point of discharge of wastewater to the river. It shows a building erected on the channel as at April 2005. The associated problems to this practice include obstruction to the flow resulting in the backflow to the upstream section. Plates 4.3 and 4.4 show the state of the river at upstream and downstream sections respectively. The river is also infested with weeds, both at upstream and downstream sections, indicating a poor management practice. It was also reported that some units of the clarifier at the plant are not functioning appropriately. This situation increase the volume of water discharged as wastewater. The quality of wastewater discharged to the river is also affected. The situation promotes rapid siltation, weed growth and flooding of adjacent area under a moderate rain. 57 Environmental Assessment Study of Lagos Water Corporation July 2005 , Plate 4.1: Discharge channel from Adiyan plant 58 Environmental Assessment Study of Lagos Water Corporation July 2005 Plate 4.2: Point of discharge of wastewater from River Adiyan - a building is obstructing the flow. Plate 4.3: River Adiyan at upstream section before the discharge point 59 Environmental Assessment Study of Lagos Water Corporation July 2005 Plate 4.4: Downstream section of River Adiyan 4.2. 1.1 Estimate of quantity of wastewater generated by the plant Figure 4.1 shows the volume of waste generafed, as a proportion of the inflow to the plant. The proportion of waste generated varies from 0.89% to 4.65% of the inflow to the plant. The mean value of waste generated is 1.78% of the inflow. This is the amount of wastewater that is discharged to the niver. The amount of waste discharged varies with season, with the highest occurring between week 20 and 39 of the year (that is May to September). The implication of this is that more wastewater is discharged to the river during the rainy season, which compounds the flooding of the river plain. 4. - o 2 - 0 - 0 25 50 Week Fig. 4.1: Volume of waste generated in Adiyan Plant in 2004 60 Environmental Assessment Study of Lagos Water Corporation July 2005 The amount of waste generated is calculated as follows: Design capacity of the plant = 70 million gallons per day Utilization Capacity (Maximum) = 60% Maximum inflow = 42 million gallons per day Proportion of waste generated (peak) = 4.65% The maximum amount of wastewater generated = 0.0465 x 42 = 1.953 million gallons per day The average amount of wastewater generated = 0.0176 x 42 = 0.739 million gallons per day (2797.4 m3/day) The average quantity of total dissolved solid in the waste = 1.10% 4.2.2 The Iju Water Treatment Plant The Iju plant was commissioned in 1901, with an additional unit installed in 1991. The total installed capacity of the plant is 48 MGD of water. Between 1901 and 1954, raw water for the treatment plant was abstracted from River Adiyan. Between 1954 and 1996, the raw water was obtained from both River Adiyan and Akute Intake. Plate 4.5 shows the state of the intake system on River Adiyan as at April 2005. The LSWP management used to maintain the river channel on regular basis when the intake system at Iju was in operation. As at 2005, this practice has stopped. Weed has taken over the river channel at the upstream and downstream sections of the intake unit. This practice has encouraged flooding. In addition, the river bank has overflow to the pump house at Iju, as shown in Plate 4.5. 61 Environmental Assessment Study of Lagos Water Corporation July 2005 Plate 4.5: Old inlet house at Iju Waterworks now flooded and overgrown with weed (April 2005) The raw water moves via the alum dosing unit to the clarifier unit and then to the filtration bed. Appropriate dose of lime and chlorine are added to the filtered water. The sludge from the clarifier and filtration bed (during backwashing) is discharged via conduit to the Adiyan River. It was reported by the early 1990s that the conduit pipe carrying wastewater from the plant to the river had blocked resulting in spillage at the inspection chamber that is within the treatment plant compound. In 1995 a surface channel was constructed from the inspection chamber to the river as an alternative sewer. It was observed that while the clarifier unit of the earlier horizontal sedimentation system has not been functioning, the backwashed water of the new filter bed cannot be recycled due to faulty pump. The ultimate effect is increase in volume of wastewater, water-logging within the compound of the treatment plant, siltation of the river channel and flooding of adjacent properties. Plate 4.6 shows the horizontal sedimentation tank, while Plate 4.7 shows the area affected by backflow. Plate 4.8 shows the state of the river at the downstream section of the plant. Plate 4.6: A Team of Consultant within the sedimentation tank area 62 Environmental Assessment Study of Lagos Water Corporation July 2005 Plate 4.7: Effect of backflow from River Adiyan to the staff quarters within Iju plant (April 2005) 1F 1 1' Plate 4.8: State of River Adiyan at the downstream end of Iju plant (April 2005) 63 Environmental Assessment Study of Lagos Water Corporation July 2005 4.2.2.1 Estimate of quantity of wastewater generated by the plant Figure 4.2 shows the volume of waste generated, as a proportion of the inflow to the plant. The proportion of waste generated varies from2.12% to 29.35% of the inflow to the plant. The mean value f waste generated is 13.1% of the inflow. This is the amount of wastewater that is discharged to River Adiyan at Iju. The amount of waste discharged varies with season, with the highest occurring between April and June. The implication of this is that a high volume of wastewater with high silt content is discharged to the river during the rainy season. 3 0 20 o Jan M ar M ay Jul Sep Nov M onth Fig. 4.2: Volume of waste generated in Iju Plant in 2004 The amount of waste generated is calculated as follows: Design capacity of the plant = 48 million gallons per day Utilization Capacity (Maximum) = 40% Mean inflow = 19.2 million gallons per day Proportion of waste generated (peak) = 29.35% Proportion of waste generated (mean) = 13.1% The maximum amount of wastewater generated = 0.2935 x 19.2 5.635 million gallons per day The average amount of wastewater generated = 0.0131 x 19.2 = 2.515 million gallons per day (9745.6 m 3/day) The proportion of waste generated at Ij.u plant in 2004 exceeded that of Adiyan plant. This could be attributed to the state of the plants, since Jju plant is older than Adiyan plant. 64 Environmental Assessment Study of Lagos Water Corporation July 2005 4.3.0 Plant Induced Problems The treatment plants at Adiyan and Iju produce 70 MGD of potable water for Lagos city. Both plants discharge their wastewater to River Adiyan. The Iju plant is at the downstream end of the Adiyan River. The Iju plant came into operation some years before the Adiyan plant. Prior to the commencement of operation at Adiyan, water was available at River Adiyan for abstraction at Iju plant. The first plant-induced environmental problem was noted at Iju plant, when water could not be abstracted from the river as a result of siltation and weed infestation. The intake - house at Iju plant was later abandoned. Later, the river became silted-up, resulting in stagnation of flow. This has resulted in flooding of adjacent highways and buildings at Iju and Adiyan. In addition, there has been a back-flow from the river to the Iju plant environment. This has resulted in the flooding of a number of houses within the Iju plant. Some of the houses had been demolished, and some are marked for demolition. The plant-induced problems have been compounded by the land-use pattern in the area, indiscriminate construction of building on river or discharge channel courses, indiscriminate dumping of refuse, topography of the area. 4.4.0 Mitigation Measures Suggested mitigation measures categorized into two main groups: immediate action and future operational schedule. The immediate action plan is expected to restore the receiving water (River Adiyan) to its condition upstream of the Adiyan plant. The future and regular action plan is to ensure that the condition of the receiving water is maintained within the acceptable standard. 4.4.1 Immediate Action (i) Dredging of River Adiyan from the Adiyan plant to the downstream end of Iju plant. The channel improvement exercise is to span an average width of 25 metres and a length of 3 kilometres. The maximum depth of the river at upstream of Adiyan plant is 1.5 m, but the depth of river at downstream end of Iju plant is 0.5m. Thus, the maximum depth of deposit to be excavated is 1.0 m. The dredging will involve the use of mechanical dredge to remove the silt deposits and the growing weeds. The operation will involve hydrological survey, mobilization of equipments to site, removal of unwanted materials and disposal of unwanted material from site. Considering that the section of the river is trapezoidal, and the depth of excavation ranged from zero at upstream to 1.0 m at downstream end, the volume of material to be excavated is 15,000 cubic metres (Fig. 4.3). The cost of the operation is put at N30,000,000 (N2.000 per cubic metre). 65 Environmental Assessment Study of Lagos Water Corporation July 2005 (ii) Rehabilitation of the treatment plant, especially the clarifier and filter beds. This will reduce the quantity of silt materials discharged as wastewater to the river. In addition, this will reduce the operation loss at the plants, and reduce the volume of wastewater discharged. 4.4.2 Future and Regular Action (i) Regular maintenance of the treatment plants, receiving water bodies and other hydraulic systems based on FAP and Monthly Performance Assessment Plan (Table 4.1). (ii) Treat water and dispose wastewater such that the effluent complies with the regulatory standard. (iii) Community-based management of River Adiyan should be formed. This forum should focus on educating the community on the impact of dumping refuse on the water course, as well as the menace of building on the water course. In addition, the community should be aware of the benefit of the channelisation, such as fishing, navigation, reduction in flooding of the environment. Cz Cz G |ISettlement | °G m ~~~~~Z3 _C- = '_ O-~--------~----' -O C ___ c [73 ) 2 C - ~ C O r r. - G ] 2 (a) Plan of river channel Adiyan Plant FIju Plant | |Settlement 66 Environmental Assessment Study of Lagos Water Corporation July 2005 Cross-section of Zone of river channel to be river channel de-silted, varies from 0 m at upstream of Adiyan plant to Im at Iju plant (b) Longitudinal profile of channel Fig. 4.3: Sketch of river channel showing zone to be de-silted 67 Environmental Assessment Study of Lagos Water Corporation July 2005 Table 4. 1: Functional Assessment Plan for the Lagos Water Corporation WATER TREATMENT PLANT FAP Assessment Levels (AL) Assessment Frequency (Freq) Method of Assessment (MOA) A - Annually PS - Periodic Sampling Start assessment at this Level Q - Quarterly RS - Random Sampling M - Once per month VCC - Validated Customer Complaints Add this Level if performance BW - Once every 13-16 days UV - Unscheduled Visits for ALI is Unsatisfactory W - Once per week CE - Customer's Evaluation R - As required Add this Level if performance at ALI or AL2 is _ nsatisfactory Note: The first method listed in the MOA column Level when perfonnance below is the primary assessment method. improves. Spec Assessment Level Sample Size Item Performance Objective Performance Standard MOA ALl AL2 AL3 Normal Reduce Freq 3.1 Operation The LUWP management shall Plant and Systems equipment and PS N/A N/A 10% 5% M operate the Water Treatment components are efficiently, safely and VCC Plant and Collection System to continuously operated per specified efficiently and safely collect, treat operating criteria to collect, treat and and dispose of wastewater such dispose of wastewater and effluent that the effluent complies with complies with the regulatory the regulatory discharge permit discharge permit. 24 hours per day, seven days per 68 Environmental Assessment Study of Lagos Water Corporation July 2005 Spec Assessment Level Sample Size Item Performance Objective Performance Standard MOA Reduce Freq ALI AL2 AL3 Normal d week, throughout the contract Unscheduled interruptions are period. minimized such that collection demand and effluent quality requirements are met 99 percent of the time annually. 3.1.1 '\aste%%ater Ellluent Qualit. Th1 LiAVP nianagenient ihall LaboratorN analk ses confimi that PS N A N A lI u,- N A NI produce treated %ater and %%aste%%aler etlluent conlplies v ith tihe \\aste%%ater ettlueiit that complies reguilatorN dischaiVe pemlit. x% iih the regulaworN discharge permlit 3.1.'2 Ninimum Operator Attendance The m11in1imumLI111 nmibers aid tNpes of PS N A N A 1(r', N A I\ The L[I JVP managementi shall treatmnent Plant operators support pro% ide treatmienit plant operalors personnel. and superx isorN Operators aind support perionnel in in direct responsiblle c.harge, shall s,Ufficient quantities of staffing conmpk. b\ each applicable shitt. xilth per shilt to elficientl\ and safely FFP.\ (Ngerian regulator\) standard operate eqtiipniien at all timiies of t10r ihe dis.charge. opelation. 24 lhcours per di\. seen klada!s per \keek. thioULho10ut the contract period. 3.1.1 Operating Records, Logs. Reports and Procedures I lie Ll WP niaanageiienl shall All reqtiired operating records. logs. I'S N A N A lil" N A NI prepare, stibnilt and maintain reports and procedures are 69 Environmental Assessment Study of Lagos Water Corporation July 2005 Spec Assessment Level Sample Size Item Performance Objective Performance Standard MOA Reduce Freq ALl AL2 AL3 Normal d __ operating records, logs and maintained current and complete and reports for in-process tracking of applicable copies provided to the plant output characteristics. knock out within the specified times. The LUWP management shall develop and update operating procedures to reflect current operating processes and Plant and Systems configuration. 3.2 Integrated Maintenance Program (IMP) The LUWP management shall IMP is accomplished per PS N/A N/A 10% 5% M develop and implement an IMP Management's incorporated Program for the Intake system, Treatment and schedule. Plant and Discharge System to ensure all equipment and All repairs costing at or less than the components remain in optimum Management's limit of liability are condition and sustain maximum responded to within 24 hours. life. _ 70 4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Environmental Assessment Study of Lagos Water Corporation July 2005 Table 4.2: Monthly Performance Assessment Summary Annex/sub-annex: _ Month/Year: Spec n ALZi'AL3 Rating Title -A f lteni~~~~~~~~ Samiples A Li h ape Item TilA} l X|l Samples 3.1 Operation __________ 3.1 I \a[er QuaIitN _ 3 1.I \VasLe\\acer Efltuent (Q,ualt. __\ '.1 .3 _ lininium (O)perator .-\tIendtanLe 3.1.4 ()peraiing Records. Logs. Re ports _ anid Piocedures ___ _ _ 3.2 Integrated Nlaintenance Program (INIP) 3 .2. ipsireai n1 er chalnnel 3 f Efflluenl discharge chainnel f-A j _ 1 3 D-x instreani of ri\ er chanel _' 111_ IF __ _ Comments: Recommended Actions: MPAR Signature: Date: 71 I Environmental Assessment Study of Lagos Water Corporation July 2005 CHAPTER FIVE 5.0 DISCUSSION OF RESULTS From the result of all the analysed samples and the evaluation of all the data acquired therefrom, this study has revealed the adverse impacts of the two treatment plants - Adiyan and Iju on the nearby River Adiyan and the land uses. 5.1 Geochemical Impact From the geochemical point of view, geochemical impacts on the nearby River Adiyan and the land uses have been revealed by the concentration of heavy metals in water, plants and soils. Those samples (water, plants and soil) found within the downstream sector of both Adiyan and Iju discharge points contained higher concentration of such heavy metals when compared with their counterparts at the upstream sector. The consequence of the above is reduction of fishes and variety of plants in the downstream sector than the upstream sector of the River Adiyan. Furthermore, the riverbed at the downstream has been so much silted to the extent that River Adiyan at the downstream is almost stagnant. Coupled with this is the eutrophication caused by some heavy metals emanating from the plants. Consequent on the above, is the fact that the stagnant River Adiyan coupled with large quantities of weed have turned the riverbed into a breeding ground for mosquitoes. This has resulted in the high rate of malaria prevalent among the people of the community in the "Project Area". Also, the fishing and farming activities prevalent at the upstream sector of River Adiyan is no more possible at the downstream sector as a result of the reasons mentioned earlier. 5.2 Ecological Impact From the ecological points of view, the results of the physical, chemical characteristics, minerals and heavy metals, primary productivity, morpho- edaphic index of water, as well as flora and fauna at Akute Intake, River Adiyan upstream and River Adiyan downstream were compared. Similarly, the physical and chemical characteristics as well as mineral and heavy metal from Adiyan and Iju sludges were also compared. The result of the above comparisons revealed a negative impact of the two plants on the nearby River Adiyan and the community. 72 Environmental Assessment Study of Lagos Water Corporation July 2005 The primary productivity at Akute and the upstream sector of River Adiyan was found to be higher than at the downstream of River Adiyan. The low primary productivity resulted from the wastewater from both Adiyan and Iju plants discharged into the downstream sector of Rive Adiyan. The wastewater and the high amount of silt contained therein are discharged into the downstream sector of River Adiyan thereby causing siltation of the riverbeds. This activity had led to the flooding of River Adiyan and flourishing of weeds (ferns). Consequently, life forms in the downstream sector of River Adiyan have reduced, large scale breeding of mosquitoes has prevailed resulting in the prevalence of malaria in the community. 5.3 Water Quality From the result of both the geochemical and ecological studies, it has been revealed that the water quality is not at its best especially the clean waters produced at the two plants. This is due to the non-proper functioning of both the sedimentation and the filtration beds. 5.4 Geomorphology The geomorphology of the Project Area has been described as relatively plain in its northern sector. Towards the southern axis of the area, the landform could be said to be associated with undulating plain characteristic of wetland along the main river channels. There is a distinct flood plain located at the top right corner of the "Project Area" especially around River Ogun. The river valley cuts across the study area in a diagonal nature with the associated oil palm trees and raffia palm trees along the river valley (River Adiyan). Generally, the left southern corridor is associated with gentle slope. As a result of the above and as part of the adverse impacts of the two plants on the nearby River Adiyan, and land use, the morphology of the area has aided in large scale erosion when it rains, and this causes large scale flooding of the area. 5.5 Mitigation Measures On the basis of the result of this study, two mitigation measures have been suggested: (i) Practical design and performance standards for treatment and disposal of sludge and wastewater from the plants that will eliminate 73 Environmental Assessment Study of Lagos Water Corporation July 2005 plant-induced adverse effects on the receiving waters and related land uses. (ii) Designing a practical, costed programme for improving the receiving water to a condition similar to, and commensurate with their condition upstream of the plant discharge. The first mitigation measure can be achieved through the rehabilitation of the two plants by replacing the damaged sedimentation and filtration beds as well as the pumps. It has been fully established that the broken down equipments like the sedimentation beds and the filtration beds have been considered to be the major contributors to the large volume of wastewater been generated and discharged into the downstream sector of River Adiyan. From Iju plant, a maximum of 5.635MGD of wastewater is generated and discharged in River Adiyan while an average of 2.515MGD is also generated and discharged. From Adiyan plant, a maximum of 1.953MGD of wastewater is generated and discharged while an average of 0.739MGD of wastewater is generated and also discharged into River Adiyan. The wastewater generated and discharged has been estimated to contain about 1.10% dissolved solids which now functions as the siltation discharged into the downstream sector of River Adiyan. The rehabilitation of the plants as suggested will reduce to the barest minimum, the amount of wastewater generated and discharged vis-a-vis the amount of dissolved solids contained therein. The second mitigation measure can be achieved through the dredging of River Adiyan from Adiyan plant to the downstream of Iju plant. The dredging will span an average width of 25 meters, a length of 3km and a maximum depth of 1 meter. The total volume of material to be excavated, when one takes into consideration the trapezoidal nature of the section of the river is estimated at 15,000 cubic meter. The total cost of the dredging is estimated at N30 million at the rate of N2,000 per cubic meter. The following factors were considered in recommending the mitigation measure, as well as in estimating the cost of activity. * Maximising the benefit of channel improvement such as increase in flow velocity and reduction in peak flow. * Reducing the environmental induced problems of big-scale dredging such as, reduction in the natural bank vegetation and the habitat diversity * The available equipment and manpower in the Nigerian market. 74 Environmental Assessment Study of Lagos Water Corporation July 2005 CHAPTER SIX 6.0 CONCULUSION AND RECOMMENDATION 6.1 Conclusion The "Environmental Assessment Study of the Lagos Water Corporation" under the World Bank Assisted Project Preparation Facility for the 2nd National Urban Water Reform Project has been carried out. The study showed that the two plants at Adiyan and Iju have impacted quite negatively on the neighboring community from the points of environmental geochemistry, ecology and environmental engineering. The water quality has reduced considerably as some of the waters, plants and soil contained more heavy metals in the downstream sector of River Adiyan when compared to the upstream sector. Furthermore, the primary productivity in the downstream of River Adiyan is quite lower than that of the upstream sector of River Adiyan. In addition, much siltation and eutrophication were found to be more in the downstream sector of River Adiyan than the upstream. Because of much siltation, the River Adiyan downstream has refused to flow normally, and this has always led to flooding of the river whenever it rains. In addition, the siltation of the riverbed coupled with eutrophication has resulted in the area being a breeding ground for mosquitoes. This has eventually led to prevalence of malaria in the community. All the above impacts are related to the non-functioning of some equipments in the plant most especially the sedimentation beds and the filtration beds. The above suggested mitigation measures when carried out will help arrest the above described negative impacts related to the two plants. 6.2 Recommendation As already indicated, the following recommendations are being suggested to arrest the environmental impacts of the two water treatment plants on the nearby River Adiyan and the community of the Project Area in general. 1. Total rehabilitation of the two plants especially the sedimentation tanks, the filtration beds and the pumps. 75 Environmental Assessment Study of Lagos Water Corporation July 2005 2. Dredging of River Adiyan from the point of discharge of Adiyan Plant up to the downstream sector beyond Iju Plant, to allow for free flow of River Adiyan. 3. Formation of community-based River Adiyan management forum to sustain the benefits of (1) and (2) above. 4. In addition to the above, a further need for more detailed studies is recommended, among others, to: a) Examine the river form and function and develop costed alternative for how these can be restored and b) Determine how the dredging needs to be done, and the spoils disposed of, so as not to cause other environmental and social impacts. It is however very important to note that the above recommendations can only be meaningful after the rehabilitation of the plants earlier suggested has been completed and properly operated. 76 b Environmental Assessment Study of Lagos Water Corporation July 2005 References Adefolalu, D. 0. (2002) Climate of Nigeria. In: Africa Atlases, Les Editions J.A., 62 - 65. APHA (1980). Standard Methods for the examination of water and wastewater. 15th Edition, Washington, D.C. American Public Health Association, 1134pp. Bear, F.E. (Editor) (1964). Chemistry of the soil, 2nd Edition, Reinhold Publishing Corp., New York, 515pp. Bowen, H.J.M. (1966). 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Geochemistry of Rave and Dispersed Chemical Elements in soils (translation in Russia), Consultants Bureau, New York, 209pp. WHO (2000). Guidelines for Drinking Water Quality, WHO, Geneva. 77 I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Environmental Assessment Study of Lagos Water Corporation July 2005 ENVIRONMENTAL ASSESSMENT STUDY FOR THE LAGOS WATER CORPORATION UNDER THE WORLD BANK ASSISSTED PROJECT PREPARATION FACILITY FOR THE NATIONAL WATER REHABILITATION PROJECT PREPARED BY A TEAM OF CONSULTANTS LED BY DR M. I. OGUNBAJO 78