Study On The Phosphate Reduction System Construction And Efficiency Influencing Factors In Treating Hypersaline & High Phosphate Wastewater

Along with the rapid development of mustard industry,a large amount of hypersaline wastewater containing high nitrogen and phosphorus has been discharged into the Three Gorges Reservoir annually. With the aggravation of nitrogen and phosphorus pollution and eutrophication of the water environment, as well as the improvement in discharge standards of nitrogen and phosphorus, it is becoming increasly ungent to develop a highly efficient phosphorus technology.This thesis, studying on hypersaline and high phosphorus wastewater, according to the problem of slow construction and low phosphorus removal efficiency of the phosphate bio-reduction system in the anaerobic environment,explored the effect of aerobic and anoxic environment on phosphate bio-reduction system construction through parallel tests, and successfully constructed the reduction of phosphate phosphorus system for the first time in squencing batch biofilm reactor (SBBR ). Through the analysis of the balance of phosphorus and the composition and transformation of the various phosphorus forms of sludge in the reactor , the thesis preliminarily proofed that approaches for phosphate reduction is phosphate bio-reduction .Then the thesis systemically researched on the effect of initial pH value,carbon-phosphorus ratio, dissolved oxygen,temperature,phosphorus concentration,biofilm densty,nitrate concentration and organic loading on phosphorus removal efficiency of the SBBR phosphate bio-reduction system,and got the key control parameters to get high removal efficacy of phosphate bio-reduction system. The main conclusions are as follows:The results showed that:oxygen environment had significant effects on the phosphate bio-reduction system construction. On the condition of temperature 30℃,organic loading 1.0kgCOD/m~3·d and influent pH value 4.5,using the way of 3% to 7% salinity shift manner to startup the reactor , 26 days later , the removal rate of COD and phosphate achieved 86% and 23% in the anoxic environment and achieved 95% and 70% in the aerobic environment. Rapid construction and high efficiency of the phosphate bio-reduction system has been realized that when dissolved oxygen was 6mg/L. Furthermore ,influent nitrate concentration had significant effects on phosphorus removal efficiency of the anoxic phosphate bio-reduction system, nitrate concentration between 105mg/L~160mg/L was beneficial to anoxic phosphate bio-reduction, low or high nitrate concentration could inhibit anoxic phosphate reduction bacteria. After the biological dephosphorization system without excess sludge running 26 cycles, the removal rate of phosphate achieved 70%.Results of analyzing the balance of phosphorus and phosphorus various forms of sludge in the reactor showed that: averagely 41.8mg/L of external phosphorus got lost per day, and that 155mg of internal phosphorus in sludge got lost through the path of phosphorus forms transformation and phosphate reduction, which accounted for 14.2% of the external phosphorus loss and 12.5% of the total phosphorus loss, respectively. The transformation path of phosphorus forms in sludge is Org-P→NaOH85-P→HCl-P→NaOH-P→BD-P→H2O-P. The SBBR biological dephosphorization system which successfully constructed was phosphate bio-reduction system.Initial pH value,carbon-phosphorus ratio,dissolved oxygen,temperature,biofilm densty and organic loading had significant effects on phosphorus removal efficiency of the SBBR phosphate bio-reduction system. pH value 8,carbon-phosphorus ratio 100,dissolved oxygen 6mg/L,temperature 30℃,biofilm densty 40% and organic loading 1.0kgCOD/m~3·d was the best operating conditions for the phosphate bio-reduction system. On the best operating conditions,the effluent COD and phosphatenitrate concentration achieved 106mg/L and 15.04mg/L which removal rate achieved 99% and 69% respectively when the influent COD and phosphate concentration was 4837mg/L and 48.40mg/L.There was a significant positive correlation between influent phosphate concentration and the volume of phosphate-removing . There was a significant positive correlation between COD removal volume and the volume of phosphate-removing too. Influent nitrate concentration had significant effects on phosphorus removal efficiency of the SBBR phosphate bio-reduction system, the volume of nitrate nitrogen-removing and phosphate removing volume had significant negative correlation .The research results are important in practicality value which has an important realistic significance. This thesis has opened up another approaches for biological dephosphorization which will provide theoretic and technical support in exploiting the new biological phosphorus technic based on phosphate reduction.