Research On The Mathematical Model Of Coagulant Dose In The CEPT Process And The Characteristics Of The Sludge

Most of new wastewater treatment plants built these years in China adopt the second biological treatment process which needs a lot of energy and operating costs, so that many of them can not operate normally. For the concentration of organic substances in the sewage is low in our southern cities, the Chemical Enhanced Primary Treatment (CEPT) process, which can remove more pollutants at less cost and greatly increase the removal of organic substances in primary treatment process, will be widely applied.Based on the mechanism of wastewater treatment, in this paper it has analyzed that the physical form of removed pollutants by the CEPT process, ascertained the mathematical model of PAC dose according to the research on related influencing factors, and studied characteristics of the chemical sludge from the process. Thus it is to aim at establishing the base for the further application of CEPT.It has been found that the removal of COD will increase with the augment of PAC dose, the optimal dose is about 20mg/L; most of removed pollutants in sewage by CEPT are colloidal and suspended particles whose diameter is above over 0.22~0.30μm, most of unsolvable solid matter in the wastewater discharged from the process is composed of submicron particles.The dominative factors of PAC dose include temperature, pH, SS and turbidity. The higher the temperature is, the less the dose will be; it will be a minimum dose when pH comes up to 7.0; PAC dose increases with the hoist of SS and turbidity of the wastewater. The mathematical model of PAC dose can be applied efficiently to automation system in CEPT wastewater treatment plants in the future.The removal of undissolved solid by CEPT can be over that of conventional settling tank. But the condensation and fluidity performance of the former is inferior to that of the latter. As to the wastewater treatment plant in CEPT, the reasonable interval to discharge sludge is less than 8h.The design of sludge-hopper in sedimentation-tank and operation of discharging sludge needs to be standardized. It can avoid sludge-floating in settling tank efficiently. For the viscidity coefficient of chemical sludge is bigger than that of the sludge from conventional primary settling tank, the gradient of pipeline and the loss of water head ought to be ample properly in the design of the sludge-pipeline and sludge-pump.