35 of 74  Construction of Giresun Wastewater Treatment Plant  Tender Dossier Volume 3 Employer’s Requirements  Section 3: Plant Description  3.3.4.23 Potable water system  3.3.4.24 Mechanical Thickeners for Excess Sludge 3_Vol3_d4.3_Section 3_Plant Description_GIR_rev08  Polymer shall be used for conditioning the sludge. The polymer shall be prepared in a polymer  generation unit. The polymer generation unit shall allow powder polymer to be diluted/dissolved to a  predefined concentration and automatically mixed and matured. The polymer generation unit shall be  a stand-alone unit and be automatically controlled locally by a local control panel. The minimum  storage capacity of polymer shall be 30 days.  Special care shall be taken to avoid pollution peak loads caused by the addition of return flows. Supernatant from thickening process(es) shall be delivered back to the system by gravity as possible.  The mixture of supernatant with drainage water and sewerage generated in the WWTP is not  permitted.  The service and technical water supply system and sufficient connection port shall be supplied for  sludge dewatering building and equipment (mechanical thickener, dewatering decanters, etc.). In order to be able to back wash of all thickeners, the service water line shall be installed and the  appropriate number of connection points will be supplied. Flow of service water supplied for this  purposes shall be measured to calculate the filtrate water flow.  Thickeners, polymer preparation unit, and their auxiliary equipment and instruments shall be located  in the dewatering building. In order to make it easier to access to mechanical thickeners during  operation or in case of maintenance / repair, structures such as platform / walkway etc. around  thickeners will be provided and equipped. These structures such as platform etc. shall be made in  accordance with Section 7.7 of the mechanical specification. Belt thickener type, drum thickener or centrifugal decanters shall be used for excess sludge thickening.  The units shall be fully closed for the provision of odor control. The extracted foul air from the units  shall be transferred into the odor removal unit. Mechanical thickeners shall be used to increase the dry solids content of the excess sludge up to  minimum 6 % DS. In order to measure the quantity of excess sludge incoming to each mechanical  thickener, flow meters shall be provided.  Potable water supplies shall be made available to the Administration Building, the Guard House,  workshop, screen building, digester operation room, sludge dewatering building and any other  locations as required. Firefighting, polymer preparation and dilution water shall also use potable water.  The firefighting system shall be supplied and erected in complete compliance with the relevant  Turkish Law and local regulations. The Tenderer shall design, supply, install and commission all the  necessary pumping and storage systems together with the necessary piping and auxiliary units in  complete. In order to control the water level of firefighting water storage tank, a valve with hydraulic  floater shall be provided. Storage tanks and all other necessary equipment (e.g. pumps, valves, etc.) for  treated wastewater, potable water and firefighting water shall be located in the same building.