Study On Sidestream Sludge Contacted With Leachate For Domestic Sewage Treatment In Wwtp

Partial nitrification and denitrification biological denitrification process has the advantage of saving carbon source and aeration energy consumption and reducing sludge production.Achieve partial nitrification is of great significance to solve the problem of denitrification under low carbon conditions in today's activated sludge treatment process.However,the realization of partial nitrification usually requires complex and rigorous condition control,which makes the large-scale application of partial nitrification technology have great limitations.Landfill leachate is a kind of refractory high-concentration organic wastewater with high ammonia nitrogen,high pH,high organic concentration and rich in heavy metal ions.Among them,high ammonia nitrogen and high pH will form free ammonia(FA),which has a strong sterilizing effect.This study proposes a technical method for the lateral flow accepantance and treatment of landfill leachate in municipal sewage treatment process,namely: firstly,landfill leachate was mixed with a certain proportion of activated sludge and soaked for 24 hours,and then the sludge mixture is returned to the reactor to realize the regulation and control to the effect of domestic sewage treatment.In this study,high concentration FA in landfill leachate was used to inhibit nitrite oxidizing bacteria in activated sludge through the above operation mode,and partial nitrification and denitrification biological denitrification process was realized under the combined treatment of landfill leachate.The effects of daily immersion of 20% activated sludge in municipal wastewater treatment reactors with 1%,3% and 5% landfill leachate mixture(as compared with domestic sewage)on the operation of the main biological treatment process were studied.The results show that the total nitrogen removal rate can be increased by about 15% when the leachate content is 1%.When adding 3% and 5% leachate,partial nitrification could be achieved in the first two weeks of the reaction,and the accumulation rate of nitrite in the effluent(calculated by the percentage of nitrite nitrogen in total nitrite/nitrate nitrogen)reached 40.5±16.9% and 67.5±22.5%,respectively.However,in the reactor with 3% leachate,the activity of NOB can be restored because of the adaptability of NOB to high concentration FA.In the reactor with 5% leachate,as the concentration of FA was too high,the activity of nitrifying bacteria(contains ammonia oxidation and nitrite oxidation)decreased significantly.In addition,the addition of leachate can improve the removal effect of phosphorus in the bioreactor.In the 5% group,the removal rate of phosphorus can reach 80%(compared with 20%).The microbial community structure of the activated sludge in each reactor was analyzed by high-throughput sequencing and real-time fluorescence quantitative PCR.The results showed that the NOB(Nitrospira)in activated sludge can be eliminated by soaking it in a certain amount of leachate.However,under different treatment conditions,the effect of NOB elimination will also be affected.NOB tolerance may occur during long-term operation,and NOB regrowth may occur after long-term treatment.There was no significant effect on the polyphosphor bacteria(PAOs)community in the sludge treated with sidestream leachate.