103625 THE ZIMBABWE WATER FORUM October 2013 POLICY NOTE 7 Page 1 The Zimbabwe Water Forum provides a platform for Government and Development Partners to share international best practices in the water sector between Zimbabwe and other countries. The forum was formed through a partnership between the Ministry of Water Resources Development and Management, the Multi-Donor Trust Fund and the World Bank and is hosted by the World Bank’s Zimbabwe Country Office and the Urban WSS Thematic Group. Improving the operation of Harare’s water and wastewater treatment plants The Government of Zimbabwe requested technical assistance from the World Bank to assist the City of Harare in developing design briefs for the appointment of professional service providers to undertake the design and tender process for key urgent projects in the water and wastewater sector (WWS). The consultants from Arup Pty were requested to identify the scope of selected urgent works projects and to prepare project design briefs that would specify the work required for each project. These briefs could then be used as the basis for consultants to conduct further research, or for contractors to bid on design, construction, and supervision for the urgent refurbishment needed to bring the struggling Harare WWS sector back to the high standards of the past. The consultants were also requested to develop a schedule for the studies, surveys, tests, and reports that would be needed for each project. In addition to the scope of work and design briefs, the consultants prepared contract data for each project that included the special conditions required to comply with all necessary regulations. This policy note focusses on six of the highest priority tasks that were identified during the study. Procurement strategies appropriate to the  The rationale for the project and the project specific objectives to be achieved There are a number of options for executing  The solution proposed for the project WWS projects: a consultant can be hired to  The scope of the work to be carried out undertake the studies, surveys, and design prior  The studies and surveys required to carry to tender, with the contractor responsible only out the design and supervision of the for carrying out the project; or the contractor may project be made responsible for the research and design in addition to the execution of the project.  Contract data completed for a standard contract including special conditions When studies and surveys are required to required to comply with City of Harare determine engineering details—such as plant Standing orders and the Urban Councils capacity—or when the project’s feasibility might Act be affected by ground conditions, it is preferable  A brief project proposal or funding to have the design completed before the issue of application tenders. However, when the scope of the project is already well defined—such as when old Six key tasks for renewal of the WWS system equipment is to be renewed without any Based on previous research by the consultants, six significant changes in function—a design-and- urgent tasks were chosen as the subject of the build model can work well. Each project in this scope of work and design briefs. These tasks report was evaluated to choose the approach that focused on upgrades and refurbishment of water was most suited to its specific design needs. The treatment facilities at the Prince Edward and contract and design brief templates prepared by Morton Jaffray Works and of wastewater the consultants were designed to accommodate treatment facilities at the Firle and Crowborough both options. The project briefs included: wastewater treatment works and the Budiriro  The background to each project sewage pumpstation. In addition, the consultants THE ZIMBABWE WATER FORUM October 2013 POLICY NOTE 7 Page 2 were asked to prepare a scope of works and disrepair and struggle to supply the needs of the project brief for the optimization of all the quickly increasing population of Harare. biological nutrient removal (BNR) plants, which A critical component of the works, Clarifier Three, had been struggling with poor performance has been out of commission for many years, and because of frequent power outages and other repairs are urgently needed to return the plant to technical issues. These tasks were chosen full operating capacity. Retrofitting of lamella because they answered urgent needs for type settlers would increase the efficiency and refurbishment of the system but were also production capacity of Clarifier Eight. carefully designed to dovetail with the ongoing work of the Urgent Water Supply and Sanitation Currently, there is little mechanical control of the Rehabilitation Project (UWSSRP). flow of water at the mixing chamber. Flow from Lake Chivero can only be cut off by manually Task One: Prince Edward Works closing butterfly valves in the intake tower, and Prince Edward Works is the City of Harare’s control of Lake Manyame flows requires secondary potable water source, with a design switching off the Darwendale pumps. The inflows capacity of 90Ml/day. Prince Edward has recently are subject to irregular, powerful surges that are undergone some refurbishment, primarily of its not totally contained within the chamber and that chemical dosing and disinfection facilities, which repeatedly drench the surrounding area. This has considerably improved the effectiveness of the led to accelerated corrosion of equipment, and plant. More improvements are now being workers are at risk of serious injury as they access planned by the UWSSRP, but it is critical for this the chamber. upgrade to be designed as a single project to Cavitation of the medium-capacity pumps has maximize efficiency. seriously damaged the pump sets and the The Prince Edward Works was originally designed connecting pipework, which causes frequent to supplement potable water during peak down time. The filters and filter galley buildings demand periods, rather than to provide a are structurally sound, but the mechanical, continual supply. Given increasing demand from electrical, and control plant equipment have Greater Harare, the consultants suggested the exceeded their design life and must be replaced. appointment of a contractor to undertake a It is absolutely necessary to address the restricted design check of the entire works. suction head that is the primary cause of the The design check would include a preliminary cavitation. The building itself also requires refurbishment. engineering design, design development, construction procurement, inspection, and Planned projects for refurbishment of the Morton project close out. The project will require the Jaffray Works include: services of a number of specialists including civil,  designing, fabricating, installing, and electrical, mechanical, process control, and testing the mechanical and electrical structural engineers. The coordination of these components of the Accentrifloc Clarifier specialists by a single consultant will be a critical (Clarifier Three); component of the selection process for the consulting firm.  designing, fabricating, constructing, installing, and testing the filtration Task Two: Morton Jaffray Works system, equipment, controls and power The Morton Jaffray Water Treatment Works is the supply needed to completely refurbish primary source of potable water for Greater the existing filtration system; Harare. With a design capacity of 614Mld, the  designing, constructing, and works are located below Lake Chivero, outside commissioning a new pump sump to re Harare. The facility comprises three plants deduce cavitation of the medium-capacity constructed between 1952 and 1994. While the pumps; plants once functioned efficiently, the economic  designing, constructing, testing, and crisis of the last decade has taken a heavy toll. commissioning an additional filter bank to Lacking the funds for maintenance and match the increase in Clarifier Eight’s improvements, the works have fallen into serious production; THE ZIMBABWE WATER FORUM October 2013 POLICY NOTE 7 Page 3  delineating the scope of work for the Task Four: Firle Existing Effluent Pump appointment of a specialist to undertake Station and rising mains and Mufakose a geotechnical investigation into pumpstation at Crowborough WWTW subsidence of plant three clarifiers and to Harare Water is presently installing new pumps in propose mitigation; and the effluent pump station at Firle Wastewater  delineating the scope of work for the Treatment Works, but a number of serious replacement of inlet control valves from problems remain including: pumping capacity, Lake Chivero and Lake Manyame. corrosion, and excessive leakage of the pump station discharge manifold and from the two Task Three: Little Marimba Outfall Sewer rising mains. New pumps will prevent sewage The Little Marimba Outfall Sewer is in a poor state from discharging into the Mukuvisi River by lifting of repair, and sewage spills into the catchment in treated effluent to council-owned farms for many places. Some resources have been made irrigation and fertilizer. Under the UWSSRP, available under the UWSSRP to carry out additional pumps will be installed, repairs will be refurbishments, but, while these will address made to the pumpstation pipework, and parts of some immediate problems, a more strategic view the rising mains will be replaced. This report is needed to implement a longer-term solution. proposes hiring a consultant engineer to check The capacity of the existing sewers has already the suitability of the pumps being procured—and been exceeded, and the system cannot meet the recommend any changes if necessary—and to challenge of the extensive urban growth in this design and procure permanent repairs or catchment. replacement of the rising mains, control systems, The tasks required include: pipework, and valves.  carrying out a survey to determine The trickling filters and humus tanks of the current and future number of Crowborough Units 1 and 2 are to be refurbished connections in the Little Marimba under the UWSSRP, but there will be no way to catchment; dispose of the sludge from the repaired tanks. Formerly, the sludge was mixed with the raw  preparing estimates for credible sewage from the Mufakose outfall sewer and scenarios of existing and future pumped to the inlet works, but this pumpstation sewage generation in the catchment is no longer functional, and raw sewage from the and flow regimes; Mufakose Outfall Sewer is discharging directly  undertaking a detailed survey of the into the Marimba River. Without pumps and existing sewerage system to calculate without raw sewage to dilute the sludge, the its capacity, determine its condition, trickling filters cannot be used, rendering the and determine the extent and investment completely ineffective. This report feasibility of in-situ repair; outlines the scope for a consultant project that  determining the most appropriate includes: location for additional treatment  surveying the condition of the Mufakose capacity and the required Outfall Sewer, inlet works, raw sewage combination of repair, replacement, pumpstation and rising main; or duplication of existing facilities  determining the feasibility of repair,  designing the rehabilitation and new relining, or replacement of pipelines; facilities; and  designing the necessary repair and  preparing a phased investment plan rehabilitation works for the sewer, rising for implementation of the works main and inlet works; including the repair or replacement of existing sewer pipes and the repair of  selecting pump type and duty; structures and manholes.  procuring, installing, testing and commissioning pumps and associated electrical and control equipment; and  procuring, constructing, testing and commissioning pipelines and civil works. THE ZIMBABWE WATER FORUM October 2013 POLICY NOTE 7 Page 4 Task Five: Budiriro pumping station particularly in the light of frequent, extended The Budiriro catchment lies on the south-western power cuts. fringe of the City of Harare. Its sewage used to be This report presents a project brief for hiring a pumped into an outfall sewer that discharged to consulting firm and contractor for two years to the Firle WWTW. Unfortunately, this pump optimize the operation of the rehabilitated BNR station no longer functions, and all sewage is plants. The tasks required include: discharged into surface water that drains  characterizing and monitoring raw untreated into Lake Chivero, the main source for sewage and partially treated effluent the city’s drinking water. The UWSSRP includes throughout the plants; plans to refurbish the pump station, but  carrying out a check on the process additional pump stations will be needed to design for all BNR plants; service the substantial areas of housing planned for the catchment downstream of the pump  optimizing operation of each plant station site. including mitigation of the effects of interruptions to power supply; and This report provides the design brief for a strategic plan, and subsequent engineering, for  producing an operations and the Budiriro catchment to determine whether all maintenance manual specific for each effluent from the catchment should be pumped design of BNR plant. to the Firle treatment works, or whether some or A coordinated and long-term approach is all the sewage should be treated within the critical for success catchment. Solutions may include full or partial The authors of this report stressed the need to treatment of sewage before pumping or undertake a thorough design review for each discharge, the construction of storm overflows project and recommended that specialist water with storage or treatment before pumping or and wastewater treatment consultants be hired disposal, or other strategies to reduce the impact to undertake the design and to supervise the of sewage pumping from this area on the post-design construction. It is recommended that treatment works at least cost. A comprehensive the design for all water treatment packages be survey of the sewage reticulation of the entire carried out by a single consultant to avoid catchment is urgently needed to calculate its numerous interfaces between design teams. This capacity, determine the current and future integrated design approach was not considered as number of connections, and to identify points critical for the wastewater treatment works, but where stormwater and grit enter the system. All careful planning and co-ordination will be stakeholders should be consulted in preparing the essential for all projects to avoid duplication and strategic plan including residents, planning conflict with existing plans. departments, housing co-operatives, and other developers. Once the strategic plan is in place, The authors also identified short- to medium- the design, installation, and commissioning of the term measures to mitigate the pollution caused chosen system can be undertaken. by the failure of the wastewater treatment systems and the overall lack of capacity. These Task Six: Optimization of Sewage Treatment include the repair of existing waste stabilization Plants ponds and the construction of new ponds. While Harare Water is in the process of rehabilitating the effluent would not meet the current the sewage treatment plants serving the city. This regulations, they would significantly reduce the includes a number of Biological Nutrient Removal pollution load on Lake Chivero and should be (BNR) activated sludge sewage treatment considered as part of the overall strategy. processes at the Firle and Crowborough Although the work outlined is urgent and must treatment works. These plants are intended to form the basis for planning and investment in the produce treated sewage effluent that complies short term, it is important to take a longer-term with the Environmental Management Regulations strategic view to ensure that the residents of of 2007. Since re-commissioning the first of the Greater Harare are provided with clean water and rehabilitated plants, Harare Water has safe sewage disposal in a cost-effective and experienced difficulty in managing the process, sustainable manner. THE ZIMBABWE WATER FORUM October 2013 POLICY NOTE 7 Page 5 The Zimbabwe Water Forum Policy Notes Series Between 2011 and 2013, at the request of the Government of Zimbabwe, through the Ministry of Water Resources Development and Management, and with support from the Zimbabwe Analytical Multi-Donor Trust Fund, the World Bank has undertaken a series of analytical studies and technical assistance in the water and sanitation sector. These studies are captured in the Zimbabwe Water Forum Policy Note Series. The task team leader for the studies is Michael Webster, Sr. Water and Sanitation Specialist in Harare (mwebster@worldbank.org) with support from Priscilla Mutikani (pmutikani@worldbank.org). All notes have been edited by Rolfe Eberhard and Hilary Gopnik.  Policy Note 1: A 24/7 water supply is possible for Harare and other cities: Lessons on what it takes from water manager Neil Macleod  Policy Note 2: Modeling the water sector in South Africa and Zambia  Policy Note 3: Zimbabwe’s new National Water Policy: Responding to Challenges to Create a Foundation for Sustainable Growth  Policy Note 4: The Future of Sanitation in Harare and Other Cities: Perspectives on Possible Pathways to Recovery  Policy Note 5: The Beitbridge Emergency Water Supply and Sanitation Project: Lessons Learnt  Policy Note 6: Zimbabwe Urban Water Tariff Study  Policy Note 7: Improving the operation of Harare’s water and wastewater treatment plants  Policy note 8: Zimbabwe Dam Safety Study