A Pilot-Scale Study On The Biological Diatomite Earth Reactor In The Treatment Of Municipal Wastewater

This study is about biological diatomite earth wastewater treatment technology in treatment of municipal wastewater. The aim of the study is to find a practical denitrogenation and phosphorus removal technology for municipal wastewater. The study include following contents :1.the start-up of biological diatomite earth reactor,2.optimizing the function parameters of biological diatomite earth reactor in the treatment of municipal wastewater,3.the study of pollutant removal process of biological diatomite earth reactor in the treatment of municipal wastewater,4.the study about dehydrate of sludge produced from biological diatomite earth reactor in the treatment of municipal wastewater,5.the analyse of technological economics of biological diatomite earth reactor in the treatment of municipal wastewater.The results are detailed in following contents:1. The start-up has two steps. 1) Carry on cultivation and domestication of the microorganism at first, adopt intermittence enter water way with intermittence aeration, add diatomaceous earth and culture once only, should pay attention to the adjustment of pH during this time , control it in 7 to 8. The identification index of microorganism cultivation and domestication finished is the NH_3-N removal rate is above 80%.2 ) After finishing microorganism's cultivation and domestication, carry on hydraulic load test , test course keep suspend layer steady improving hydraulic load value to design load progressively. The identification index hydraulic load test finished are: â‘ MLVSS of aerobic section reaches about 4.0g/L;â‘¡ Handle the removal effect stability and satisfy new emission control regulations(GB 18918-2002 ) first class B;â‘¢Hydraulic load reaches the design load (4.0m³/h).2. The practical performance of biological diatomite earth reactor in the treatment of municipal wastewater shows that when HRT is 7.8 h (anaerobic section of 2.8 h , aerobic section of 5.0 h ), dissolve oxygen density 2.0 3.0 mg/L, reflux ratio 150% , composite refined diatomaceous earth addition 30 ppm., PAC addition 25 ppm, each effluent index can satisfy first class A standard of new emission control regulations (GB18918-2002).3. The change of aerobic section's dissolve oxygen value from 1.0 to 3.5 mg/L, basically has no influence to the removal of COD , SS .The average removal rate of COD was steady in 87%,while SS basically fluctuated in 10 mg/L. But when dissolve oxygen value is lower than 1.5 mg/L, whether " run mud " phenomenon happened is needed further study . The change of aerobic section's dissolve oxygen density basically has no influence to nitrification process and denitrification process. The effluent NH3-N value kept under 1 mg/L , 98% removed on average;in aerobic section NO3 ^-N value was basically lower than the method limit (<0.02 mg/L);dissolve oxygen value controlled about 2 mg/L is more favorable to denitrification, and effluent TN value can satify new emission control regulations (GB18918-2002 ) first class A;the removal of TP was hardly influenced by change of dissolved oxygen value.4. Change of composite refined diatomaceous earth and PAC's addition mostly has no influence to COD's removal;when composite refined diatomaceous earth's addition was 30ppm alone, effluent TP value can satisfy first class B standard basically(<1.0mg/L),while composite refined diatomaceous earth's addition 30ppm , PAC's addition 25ppm , effluent TP value can satisfy first class A standard basically (<0.5 mg/L).5. This technology is a kind of A/O process, it is so as reflux ratio increasing ,the removal effect of TN is enhanced. During the practical performance, when the reflux ratio was 100%, effluent TN value was still lower than 15 mg/L , met new emission control regulations (GB 18918-2002 ) first class A standard. Decreasing of reflux ratio had little influence to the removal effect of COD and TP .6. Hydraulic load impact exerts a tremendous influence to clarifier-tank's solid-liquid separation, and its surface loading is lower than 0.84m3/m2*h.7. Biological diatomaceous earth strengthen nitrification and denitrification process , and the rate of nitrification and denitrification were far greater than traditional active sludge process's, 9.95 mg (N) / g*h, 6.78 mg (N) / g*h respectively.8. On condition that shelter facilities from the rain, there is no sunshine to shine but ventilate well, construct sludge produced from biological diatomaceous earth reactor thickness 200mm on dehydration bed, take 14d moisture content can reduce to about 80%, satisfies requirement handled to transport outward.9. Economic analysis results show biological diatomite earth reactor in the treatment of municipal wastewater saves about 30% on each ton of water investment as traditional active sludge process.