Enhancement Of Nitrification Performance Of Sewage Treatment System By Bioaugmentation

At present, most of wastewater treatment plants ( WWTP ) face the problems of low nitrogen removal efficiency and misconduction of the reject water. Ihese two issues can be solved simultaneously by bioaugment, that is sewage sludge water is used to enrichment the nitrifier, and then added to the sewage treatment system. An SBR reactor was built in order to explore the effect of bioaugmentation on the microbial community and nitrification performance of the sewage treatment system. COD and NH3-N were determined before and after the bioaugmentation and fluorescent in situ hybridization (FISH) was used to detect the number of nitrifer and the microbial community. Finally, the impact of community structure and nitrification performance was analysed. The main research results are as follows:(1) In use of SBR reactor, the influent ammonia nitrogen concentration of 50 mg/L of artificial simulation of urban sewage, under the conditions of the HRT for 8 hours and the SRT for 6 day, the average concentration of effluent ammonia was 35mg/L, the removal rate of only 30%; in the same operating conditions, add 1.2% of influent flow nitrifier culture medium, the effluent ammonia concentration gradually decreased to 1mg/L the following, the final state in a stable nitrogen removal rate above 99%. The results show that the bioaugmentation can strengthen the nitrification of sewage treatment plant.(2) When SBR operated steadily before bioaugmentation , the ammonia uptake rate and nitrite uptake rate was 2.59mgNH₄⁺-N/L·h,0.8mgNO₂^--N/L·h respectively. After the bioaugmentation, the ammonia uptake rate and nitrite uptake rate was 15.25mgNH₄⁺-N/L\h,4.02mgNO₂^--N/L·h respectively,The bioaugmentation can greatly enhanced the activity of the sludge in the simulation of municipal wastewater treatment plant reactor.(3 ) Bioaugmentation can increase the amount of nitrifiers quickly. Before bioaugmentation, the number of the ammonia oxidizing bacteria (AOB ) and the nitrite oxidizing bacteria (NOB) were 10^6.7 nitrifiers /mL, accounted for 3.7% (±1.2%) and 2.1% (±0.1%) of the total number of bacteria respectively. After added, the number of ammonia oxidizing bacteria were 10^7.6 nitrifiers /mL,and the nitrite oxidizing bacteria changed to 10^7.3 nitrifiers /mL.The number of the ammonia oxidizing bacteria (AOB) and the nitrite oxidizing bacteria (NOB) accounted for 8.1% (±4.7%) and 5.2% (±2.5%) of the total number of bacteria.(4) After bioaugmentaion, the community structure was similar to the seed source. After added the nitrifier culture medium which the dominant ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) was Nitrosococcus mobilis and Nitrobacter respectively, the dominant ammonia oxidizing bacteria (AOB) was still Nitrosococcus mobilis before and after bioaugmentaion; the dominant nitrite oxidizing bacteria (NOB) was gradually transferred from Nitrospira to Nitrobacter spp.