Construction of Giresun Wastewater Treatment Plant  Tender Dossier Volume 3 Employer’s Requirements  Section 3: Plant Description  37 of 74  The thickened primary sludge shall be pumped directly to the anaerobic digesters or to the digested  sludge storage tank. Quantity of primary sludge transferred to anaerobic digester or digested sludge  storage tank shall be measured. The pumps shall be speed controlled by means of frequency- converters. Adequate space within the unit shall be left for proper operation and maintenance of all  equipment. Access to the pumps and components (such as valves and local control panels) shall be  secure and unhindered. A permanent crane or lifting system shall be provided to carry out the  maintenance works for thickened primary sludge pumps. Washing water shall be connected to both the suction and discharge lines of the sludge pumps. This  washing system will engage automatically when the pumps are not operated. In addition, the service  water line shall be installed to the appropriate places of the thickened primary sludge pumping station  and sufficient number of connection points shall be supplied. The treated water should be used for this  purpose.  The Anaerobic sludge digester tanks shall be designed, constructed and equipped regarding the  requirements set in Table 2-1. The organic material in primary settled sludge and excess sludge are biologically converted in the  anaerobic digestion process. The preferred anaerobic process used for the treatment of sludge is  mesophilic, fully mixed digestion where the sludge is heated to approximately 35°C because it is  widely used in Turkey. The digesters shall be constructed as insulated cylindrical concrete tanks. Epoxy coating shall be  applied to anaerobic digester tank that come into contact with the biogas so that the coating protects  concrete against the effects of H$_{2}$S gas and a threat of sulphuric acid formation. Epoxy product to be  used for coating is subject to Engineer’s approval.  To create optimum process conditions for the methane bacteria in the digesters, effective mixing shall  be provided. The mixing system shall be designed for complete mixing so that floating sludge layers  and sedimentation of sludge at the bottom are avoided. All parts in contact with the sludge shall be  stainless steel. The effective mixing may be performed by using top mounted agitators or may be  using gas compressors and gas injection pipes. The tenderer shall provide details of mixing calculation  with his proposal.  If the Contractor intended to use a patented process like thermal hydrolysis and ultrasound  disintegration in combination with anaerobic sludge digestion process, the Contractor shall provide all  relevant information, data and calculation related with this system to the Employer during the tender  period. The proposed system should be technically and operationally proved by on-site data from three  wastewater treatment plant with the proposed alternative process like thermal hydrolysis process and  ultrasound disintegration.  3_Vol3_d4.3_Section 3_Plant Description_GIR_rev08  3.3.4.26 Anaerobic sludge digester Minimum number of thickened primary sludge pump  : 1 duty + 1 stand-by  Type of thickened primary sludge pump  : eccentric screw pump  Minimum number of sludge screen  : 1 duty + 1 stand-by  Operation hour of the thickened primary sludge pumps  :   16  h/d 