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Title: Environmental impact assessment for the proposed additional desalination facilities at Malé City, Kaafu Atoll, Maldives
Authors: Sandcays
Keywords: Desalination plants
Legislative and regulatory considerations
Existing environment
Constructional impacts
Operational impacts
Mitigation measures
Environmental monitoring
Environmental impact assessments
Issue Date: Apr-2016
Citation: Sandcays. (2016). Environmental impact assessment for the proposed additional desalination facilities at Malé City, Kaafu Atoll, Maldives. Male': Maldives
Abstract: This report discusses the findings of a social and environmental impact study under the proposed project for setting up 2 new desalination plants with 5 additional boreholes in Malé City. The project is proposed by Malé Water and Sewerage Company Ltd. The proposed project involves establishing two new reverse osmosis desalination plants to add to the existing capacity in Malé to cater for the ever increasing demand. 5000 tons per day plant will be installed at the MWSC warehouse facility in Ameenee Magu and 2000 tons per day plant will be installed in the Haveeree Hingun site which is also a designated site for MWSC. Each plant will have sufficient number of boreholes to cater for the demand with 3 boreholes in the MWSC warehouse plot and 2 boreholes in the Haveeree Hingun site. The use of boreholes will overcome the need for sedimentation tanks. Given the restriction in space difficulties in laying intake pipes from sea, borehole is proposed for feed water. Desalination based on reverse osmosis technology is the same technology used in Malé currently and has been considered as the most suitable. RO desalination plant has recovery rate of no less than 40%. The proposed drilling method for boreholes is Rotary Mud Drilling; the drill bit is attached to the drill rod while being rotated and advanced into the borehole while pumping a drill mud consisting of bentonite or polymer slurry into the borehole. The project activities include clearing out the existing structures from the sites, mobilization of equipment and materials to the site, plant set up, borehole drilling and setting up of storage tanks. The project duration proposed is 6 months from the start of construction. The general construction materials and specific components that would be required for the project have been identified in the project. Major project output is brine discharge and small amounts of construction waste. Brine from the Ameenee Magu site will be discharged to the lagoon on the southern side which is also used as a harbour. The Haveeree Hingun site brine outfall is located on the north western end of Malé out from the harbor walls. Alternatives have been identified in the project document. Of these alternatives, the recommended alternative would be using sewage outfall pipe to dispose the brine as the proposed lagoon do not have much of a current hence, poses low dilution potential. Nonetheless, the brine outfall locations are devoid of marine life and is on the vicinity of harbours the impacts would be negligible. Alternatives for feed water have been discussed as obtaining from sea compared to the proposed method of boreholes. Given the need for sedimentation tanks and the quality of water obtained the use of boreholes has been proposed. Sedimentation tanks require a large space and space constraints in Malé renders the option unfeasible. Borehole drilling methods including manual drilling, jetting, precussion drilling and rotary drilling have been discussed out of which rotary drilling, which is the proposed option, has been considered as the preferred option. The proposed project is to meet the water demands of Malé City and is an improvement to the quality of services provided by MWSC to the public. It is inevitable that there would be some negative environmental impacts. However, most of the impacts of the proposed project are minor to negligible compared to the positive effects of the proposed system. Yet, monitoring to ensure the effectiveness of the proposed system would be necessary. Therefore, a monitoring component has been suggested which takes in to consideration, the most important elements that require regular checks. This monitoring component will be adhered to and will allow the assessment of changes due to construction and implementation of the project. Monitoring is specifically focussed on water quality, to include feedwater from the borehole (or other source and seawater at brine discharge location (upstream and downstream). Reef or marine ecological monitoring may be considered if the proposed location of the brine discharge or intake is found to be of ecological significance. In conclusion, it is justified from a technical and environmental point of view, to carry out the proposed project to install and operate 2 desalination plants of a total capacity of 7000tonnes per day.
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