Research Changping Sewage Treatment Plant Sludge Bulking Characteristics And Control Measures

Carrousel2000-oxidation Ditch was applied in Changping WWTP to treatmunicipal wastewater from Changping district and the industrial wastewater ofChangping Park of Zhong Guancun Science Park. The treated effluent of WWTPneed follow the First grade B criteria. However，The Carrousel2000-oxidationDitch suffered seriously seasonal sludge bulking since September to Novemberof2004, witch impacted the normal process operation of the WWTP and thetreated effluent discharge standards.In this paper, the operation performance of the WWTP during from2004to2007and the main sewage treatment structure and equiment is analyzed, and thecharacteristic parameters during sludge bulking were studied. The main goal isthat determine the factors causing sludge bulking, to propose the suitablesolving solutions, and to control the sludge bulking. The main results were asfollows:(1) There was no obvious impact to COD, BOD, SS and TN removalefficiency during initial phase because of sludge bulking of the WWTP. Thetreated target of COD, BOD, SS and TN were achieved. After Sludge bulkingoccurred, the above mentioned indices all exceeded the discharge standard fromNovember of every year.(2) The main reason of the WWTP sludge bulking was that the activated sludgesystem was operated with the sludge load less than0.04(kgBOD5/kgMLSS·d). Theminimum sludge load was0.025(kgBOD5/kgMLSS·d), which was far below thedesigned operation value of the WWTP. According to the monitor of the DOconcentration in oxidation ditch, the area where the DO concentration values werebellow0.5mg/L existed in oxidation ditch channel from both time perspective and spaceperspective. It was also one reason that caused the activated sludge bulking. The mainmethods to control sludge bulking of Changping WWTP: One method was to improvethe sludge loading of activated sludge system to ensure the sludge load of the activatedsludge system was not less than0.058(kgBOD5/kgMLSS·d). To achieve this target, itwas needed to replace the sludge dewatering equipments to ensure continuous andstable surplus activated sludge discharge and control the SRT between15to19days. Another method was to increase the DO concentration in Oxidation ditch. The averageDO concentration in the oxidation ditch was increased from2.0mg/L to2.8mg/L.(3) After replace of the sludge dewatering equipments, the main process operationparameters were: DO≥2.8mg/L, sludge load was0.063~0.067(kgBOD/kg MLSS·d), the sludge concentration maintained about3500mg/L. Successful prevention ofsludge bulking was achieved, and a very good operation result of WWTP was realized.(4) Considering the various situations before and after the sludge bulking of theWWTP, the main early warning and monitoring indicators and operation range of theWWTP were put forward to provide the basis for the early prevention of the occurrenceof sludge bulking.