Enhancing Nitrification In Wastewater Treatment Plant Through Bioaugmentation With Nitrifiers Enriched By Reject Water

Nitrifiers were enriched in O/A process （side-stream system） feeding withammonia-rich reject water and then were seeded into A2/O reactor （main-stream system）which was a municipal wastewater treatment system to achieve the enhancing biologicalnitrification. The main results and conclusions are as following:（1） Side-stream system accomplished the high removal efficiency of ammonia. Theaverage removal efficiency of ammonia and TKN were both99%above. However,removal efficiency of TN was only11%because of the low C/N.（2） The KN（Half-saturation constant） of ammonia oxidizing bacteria and nitriteoxidizing bacteria were1.3052±0.2208mgNH₄⁺-N/L and1.1012±0.0733mgNO₂^--N/L;the τN（The temperature correction factors） of ammonium utilized rate （AUR） and nitriteutilized rate （NUR） were1.072and1.027respectively, the values of KNand τNofnitrifiers were similar to those in wastewater treatment plants. The Maximum AUR andNUR were26.08mgNH₄⁺-N/（gVSS·h） and35.81mgNO₂^--N/（gVSS·h） respectivily, thosevalues were more than five times of the nitrification utilized rate in wastewatertreatment plants.（3） Bioaugmentation could improve the capacity of nitrification of the main-streamsystem, the nitrification utilized rate was1⁷mgNH₄⁺-N/（gVSS·h） more than that inwastewater treatment plants. The concentration of ammonia in effluent was lower5¹0mg/L than before bioaugmentation and the removal efficiency of ammoniaincreased by20%at low temperature. Even if the solids retention time （SRT） was lessthan10d and aerobic hydraulic retention time was only4.33h, the concentration ofammonia still more than95%, above17℃. （4） Shorter aerobic hydraulic retention time （HRT） would result in incompletenitrification of ammonia in main-stream system, as water temperature belew15℃.When the aerobic hydraulic retention time （HRT） was increased to5.43h, Theconcentration of ammonia in effluent was reduced to1mg/L.（5） In spite of bioaugmentation could reduce the ammonia loading of wastewatertreatment syetem and improve the efficiency of ammonia removal, which could notreduce the total nitrogen loading of wastewater treatment syetem, so there are morework to do to find out how to improve the efficiency of total nitrogen removal.（6） The effective suppression of phosphorus release and dephosphatation process insecondary settling tank could be achieved by increasing the ratio of return sludge andthe values of dissolved oxygen, the concentrations of phosphorus and total phosphorusreduced to0.8mg/L and0.5mg/L. The value of total phosphorus could reach the the firstof urban sewage treatment plant effluent discharge standards （GB18918-2002） Aemissions standard by preventing phosphorus release process in secondary settling tankand removing the mixed liquor suspended solid in effluent.