33 of 74  Construction of Giresun Wastewater Treatment Plant  Tender Dossier Volume 3 Employer’s Requirements  Section 3: Plant Description  Adequate space within the unit shall be left for proper operation and maintenance of all equipment.  Access to the machines, pumps and components (such as valves and local control panels) shall be  secure and unhindered.  Return sludge pumps  3.3.4.21 Flow Measurement  3.3.4.21.1 Inlet Flow Measurement  3_Vol3_d4.3_Section 3_Plant Description_GIR_rev08  A standard open channel measurement (ultrasonic) unit or in-line flow meter (electromagnetic) shall  be installed downstream of the grit and grease removal tanks for continuous flow monitoring and  recording. Regardless of type, easy access to flow meter for installation, dismantling and maintenance  shall be secured and unhindered. In addition to this pH, conductivity and temperature of wastewater  shall be measured at this unit. 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 excess sludge pumping station and  sufficient number of connection points shall be supplied. The treated water should be used for this  purpose. The pumps for excess sludge shall be submersible pumps or eccentric screw pump. 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 machines, pumps and components  (such as valves and local control panels) shall be secure and unhindered. Service water connections  shall be supplied so that the pump can be washed back on the suction and discharge lines. Minimum one additional stand-by excess sludge pump shall be provided.  The measured flow and status of the pumps should be monitored by the SCADA system.  The pumps shall be of the centrifugal type and be rated for return sludge. Hence, the impellers shall be  designed either as canal or screw centrifugal types.  The total installed capacity of return sludge pumps shall be minimum 75% x Q$_{WW,h}$ without using the  standby unit.  The pumps for return sludge shall be submersible pumps with frequency converters. The actual  capacity of the pumps shall be regulated automatically based on the wastewater flow measured by the  intermediate flow meter and a selected rate of return of activated sludge. The return rate shall be  determined by the required sludge concentration in the activated sludge tanks.  Excess sludge pumps  Minimum number of excess sludge pump  : 3 (2 duty +1 standby) units  Design of operation hour of the excess sludge pumps  :   16 hours/day