Pilot Study Of The Chemical Enhanced Primary Treatment Technology In Domestic Wastewater Treatment

The contaminations of municipal sewage include suspended, colloidal and dissolved organic substances. The primary treatment by throwing coagulant into wastewater has obvious effect in removing the suspended and colloidal substances and improve the discharging water quality, CEPT can make pollutant total quantity decrease and reduce treatment consumption of the following processing unit. At the same time, it saves the occupying a land area. On the base of previous researches, by the dynamic experiment, we can validate the treatment effect by inputting the coagulants and flocculants into the domestic wastewater. Combined ozone and precipitation process as the following treatment unit is proposed and studied, as well as some research achievements in aspects of characteristics of chemical sludge, treatment methods utilization of resources.(1) Under continuous running experiment, CEPT's best operating condition is: PAC throws increment 90～100mg/L,PAM 0.8mg/L, the mix time 9min, the reaction time 36min, the precipitation time 15min. Under the best operation condition, continuous running, suspended solid removing rate reaches above 97%,COD average removing rate reaches 75.1%, BOD average removing rate reaches 63%, TP average removing rate reaches 78.5%. compared to treatment level of conventional primary process, CEPT technique separately enhanced 40% , 30% , 30%, 50%, but regarding NH₃-N, TN removing rate is low, only 25%, 42.7%, removes to the chromaticity is not thorough water leakage chromaticity still above 20.Chemical Enhanced Primary Treatment can reduce in big scale the suspended and colloidal substance, but the dissolved contamination is hardly to remove.(2) In the following treatment unit, best operating condition is: the dosing ratio is 0.5g/L of ozone, PAC throws increment 40mg/L, PAM 0.2mg/L, and the best oxidation time is 30min. Under continuous running experiment, The chromaticity is easy to be removed by ozone oxidation, the average removing rate reaches 97.9%, and this treatment process have some effect on the removal of COD, turbidity,TP, the average removing rate reaches 88.8%,99.65%, 90.4%. but it has less influence on the removal of TN, NH₃-N.(3) The moisture of chemistry sludge will increase, if the amount of flocculants will be enhanced. The average VSS/SS reach to 0.7 in chemical sludge, comparing to the surplus active sludge's 96% ～ 99%, 60% ～ 80%, 29×10¹¹ cm/g, it indicates that the organic content is high, the chemistry sludge need to continue to carry on sludge stable processing. The chemistry sludge is difficult to be dehydrated; the sludge specific resistivity is 1.21×10¹² cm/g.(4) The dosing amount of coagulant and the output of dried sludge are linearly dependent, The linear correlation formula is Y=Q×(2.86×X+0.37×SS)× 10～(-6).(5) When CEPT technique enhance the removal of phosphorus in raw water, it can reduce in big scale the pollution load of the following processing unit and reduce greatly the construction volume of secondary treatment unit, if the level of discharging water is not high, the secondary treatment unit can be omitted, We can use CEPT to reach some lower level of treatment requirement. So it's reasonable for the investment and total pollution control.