22 of 74  Construction of Giresun Wastewater Treatment Plant  Tender Dossier Volume 3 Employer’s Requirements  Section 3: Plant Description  The tanks shall be constructed as reinforced concrete structures. Each of the anaerobic tanks shall be  equipped with submerged energy efficient mixers in order to ensure an efficient mixing of sludge and  water and to avoid the settlement of sludge in the tanks. The proposed mixers by the Contractor shall  be in accordance with the specifications given in Section 7.8.30. Each mixer has a separate lifting  equipment compliant with Section 7.8.1 for the hoisting of the mixers. The mixers shall be designed  for minimum horizontal velocity of the water of 0.3 m/s. Computational Fluid Dynamic (CFD)  analyses for the mixers shall be submitted during the design stage and the mixers will be subject to the  approval of the Engineer.  The tanks shall be equipped with service bridges. The sprinkler system shall be designed and installed  along the service bridges to prevent and/or remove the surface scum in the anaerobic bio-phosphorus  tanks. The treated water should be used for this purpose. The drainage pit shall be designed and  constructed on the bottom of each anaerobic tank. This drainage pit shall be equipped with the  drainage valve that is extended spindle and manual operated.  In addition to these, each anaerobic tank shall be equipped with one oxidation reduction potential  (ORP) measurement devices, at the outlet of the tank.  The volume of anaerobic biophosphorus tank should not be taken into consideration for sludge age  determination.  Minimum number of anaerobic bio-phosphorus tank for Stage 2 : 2 tanks  Minimum contact time at  : 0.75 hour  (Q$_{DW,h}$ +Q$_{RS}$) where Q$_{RS}$ : 0.75·Q$_{WW,h}$  In addition to the anaerobic bio-phosphorus tanks, the Tenderer may suggest other hi-tech  technologies (except phosphate electrodes and pre-fermentation) to support the biological phosphorus  removal in order to minimize the chemical consumption to meet the phosphorus effluent  concentration. In this case, all the necessary calculations, equipment specifications shall be provided  together with his tender. Biological phosphorus removal shall be supplemented by chemical phosphorus treatment. The  chemical dosing facilities shall be designed for chemical phosphorus removal. The extra sludge  quantities shall be taken into account in the design of the sludge treatment facilities considering that no  biological enhanced phosphorus and other hi-tech phosphorus removal takes place. 3.3.4.10 Chemical Phosphorous Precipitation  Chemical phosphorus removal shall be carried out by simultaneous precipitation of the iron trivalent  (40% FeCl$_{3}$). The dosing system shall consist of as a minimum;  -  storage tanks -  dosing pumps in accordance with Section 7.8.19.8  -  pulsation damper  -  filters  -  service water connection  -  pipes, valves and accessories  3_Vol3_d4.3_Section 3_Plant Description_GIR_rev08 