Ammonia Nitrogen Treatment Of Coke Plant Wastewater

Components were complex in coke plant wastewater,in which contains high concentration of ammonia nitrogen and a number of toxic and refractory organic compounds,and great changes happened usually to water quality and water flow.Most of the original treatment processes were conventional activated sludge method,though which the COD and ammonia nitrogen removal were not favorable and the effluent concentration couldn't attain the wastewater drainage level,which brought severe harm to our environment and human body.lt had been demonstrated that using anaerobic acidification as pretreatment and denitrification-carbonization-nitrification as secondary biological treatment to removal ammonia nitrogen in coke plantwastewater was a cost effective technology.In this research , firstly, six efficiency predominant bacteria of degradating refractory organic compounds and nitrogen removal bacteria after they were cultured and domesticated and immobilized in certain condition were thrown into carbonization, nitrification and denitrification reactor individually. Then biogradation pathway and biogradation process analysis and influence factors to biological nitrogen removal had been investigated in individual reactor. Secondly, these predominant bacteria were used in compound nitrogen removal process of treatment of coke plant wastewater,meanwhile,nitrogen removal process and operating parameters were studied.Finally, the optimum process was defined as A1-A2-O-M ,and the optimum process conditions and operating parameters were summarized as following:The total hydraulic retention time was 51 hours,among which 10.5h for anaerobic, 12.5h for anoxic and 20h for aerobic O stage,8h for aerobic M stage.The pH value of the anaerobic reactor was maintained at 6.5 -7.5.Recycled ratio of mixed liquidto the anoxic reactor influent was 3.5-5.0.MeOH must be added to anoxic unit as an external carbon source in the denitrification process.The ratio of BOD5 to TN was 10.6.In aerobic stage ,the temperature was maintained in 25-32℃,the pH value in aerobic O unit should be maintained in the level of 7.7-8.2 by the addition of sodium bicarbonate,the remaining alkalinity in the effluent was 100-200mg/L,the dissolved oxygen(DO) was at 6.59-6.83mg/L.Less than 0.05kgCOD/kgMLSS.d of COD loading rate and less than 0.01 kgNH3-N/kgMLSS.d of ammonia nitrogen loading rate should be controlled in the feed of aerobic stage. Given the above conditions,up to 87.7-93.9% of COD and up to 86.5-92.4% of ammonia nitrogen could be removed. Moreover, the overall nitrogen removal was more than 75%.When the influent concentration for COD and ammonia nitrogen were less than 800mg/L and 260mg/L respectively,the average effluent concentration for COD and ammonia nitrogen was less than 100mg/L and 25mg/L each, the two indices of which had attained the primary and secondary national standard about wastewaterdischarge 《GB8978-1996》 respectively.