Research and development of high standard reclaimed water treatment process based on municipal wastewater
To protect certain sensitive water environment in cold northern regions,high standard reclaimed water was developed using municipal wastewater.The main pollutant indicators of the effluent water were in accordance with the Class Ⅱ standard of"Environmental quality standards for surface water"(GB 3838-2002)(except for TN,TN＜10 mg/L,hereinafter referred to as GB 3838-2002"quasi Class Ⅱ"standard),and the feasibility of improved multistage AO+powder activated carbon(PAC)treatment technology(PACT)-membrane bioreactor(MBR)-ozone catalytic oxidation-disinfection-constructed wetland process was explored.The pilot test results showed that using improved multistage AO+PACT process,the pollutant removal effect was significant,the settling ability of activated sludge and system stability were improved,and the system had denitrification phosphorus removal and PAC synergistic denitrification function.Among them,adding 50 mg/L PAC resulted in COD removal rate and compliance rate of 94.23％and 84.34％,respectively,which were 2.92 and 31.57 percentage points higher than traditional process.Under the condition of low carbon to nitrogen ratio water quality,with the addition of 52 mg/L sodium acetate,the effluent TN met the standard(average value 5.61 mg/L),and the average TN removal rate was 91.78％,which was about 31.78 percentage points higher than the traditional process.TN was mainly removed by three methods:traditional biological denitrification,denitrification by denitrifying phosphorus and nitrogen removal,and PAC synergistic denitrification,the TN removal rates of the first two methods and the later method were 44.40％and 47.38％respectively.TP was removed by denitrifying phosphorus removal and traditional biological phosphorus removal methods.TP in improved multistage AO+PACT process secondary sedimentation tank effluent reached 0.1-0.3 mg/L.When 120 mg/L of ferrous chloride was added separately to the aerobic tank or 25 mg/L of ferrous chloride or 50 mg/L polyaluminum chloride was added to the effluent of the secondary sedimentation tank,the effluent TP could stably reach below 0.1 mg/L.Constructed wetland reduced organic matter and nitrogen and phosphorus to varying degrees,the removal rates of COD,ammonia nitrogen,TN,TP and SS were about 41％,66％,18％,50％and 50％,respectively.The plants grew well in summer,and the removal rate of pollutants was high.In low temperature environments in winter,although insulation measures were taken,the plants could survive,but the removal of pollutants was limited.The results indicated that the combination of improved multistage AO+PACT process and the MBR-ozone catalytic oxidation-disinfection-constructed wetland process could meet GB 3838-2002"quasi Class Ⅱ"standard.
high standard reclaimed waterPACTGB 3838-2002"quasi Class Ⅱ"standardconstructed wetlanddenitrifying phosphorus removal
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