Study On Denitrifying Phosphorus Removal From Low Carbon Source Wastewater In SBMBBR

Denitrifying phosphorous removing process has advantages of using the same carbon source and reducing carbon consume,providing effective approach for nitrogen and phosphorus standard treatment of low carbon source urban wastewater.The experiment was carried out in a sequencing batch moving bed biofilm reactor under low carbon source.In the experiment,the factors which could affect the performance of denitrifying phosphorous removal,such as COD concentration,concentration and addition modes of nitrate, concentration of nitrite,pH value and stirring speed.The performance of A₂N-SBMBBR was studied after two-sludge system was introduced,and the treatment effect on the actual domestic wastewater was investigated too.The experimental results were shown as follows:(1) Through three stages of cultivating and domesticating biofilm,R_DPB rose from 15.7% to 71.3%and target of selecting and enriching DPB was achieved.(2) With increasing COD concentration,amounts of PHB conversion and phosphorus release increased.When COD concentration was 200 mg/L and deficient,phosphorus removal efficiency was only 81.8%.Phosphorus removal efficiency was the highest and was 90.6%under 300 mg/L COD.When COD concentration was 400 mg/L,amount of PHB occured accumulation,and phosphorus removal efficiency was low because of simple denitrification.(3) When COD concentration was 200 mg/L,deficiency and excess of nitrate both decreased phosphorus removal efficiency and accumulated contents of PHB in biofilm. Phosphorous release occurred in the end of anoxic phase when nitrate was deficient.Under the same nitrite concentration,addition modes couldn't affect the efficiency of denitrifying phosphorus removal,but affected its rate in the early anoxic stage.With increasing times of addition,rate of denitfifying phosphorus removal decreased.(4) Under low concentration(between 5 and 10 mg/L),nitrite could serve as electron acceptor and carry out denitrifying phosphorous removal.Under high concentration(15 mg/L), denitrifying phosphorous removing was inhibited and occured phosphorous release.(5) Amount of PHB conversion was the highest when pH value was neutral, meta-alkalescence was second and weak acidity was the lowest.So,reactor should be controlled under neutral and alkaline environment to release phosphorous.Too large or too small stirring speed both affected phosphorous removal and biofilm biomass.Proper stirring speed of the reactor was 80 r/min.(6) Denitrifying phosphorous removing of the reactor mainly depended on sludge discharge to remove phosphorous,and other transformation forms were slight.Phosphorous of the reactor system reached a rough balance.(7) Under the condition that concentration of COD,PO₄^3--P and NH₄⁺-N were 200 mg/L, 7 mg/L and 50 mg/L,A₂N-SBMBBR had better ability of denitrifying phosphorous removal, removal rates of PO₄3^3--P,TN were 83.7%and 64.0%,respectively.(8) Actual low carbon source domestic wastewater was treated in the system of A₂N-SBMBBR and gained better treatment result.The performance of denitrifying phosphorous removal was presented and average removal rates of PO₄^3--P,TN were 85.2% and 84.5%,respectively.