Study On High Efficiency Enrichment And Bioaugmentation Of High Activity Nitrification Sludge

Municipal wastewater treatment plant(WWTP)is the critical processing step before the domestic and industry wastewater discharged into the surface water. Nitrogen discharging control is more strict, in particular, in some drinking water upstream regions. Nitrification is the first step of the biological denitrification, in which the nitrifying bacteria is the decisive microorganisms. Nitrification system of the WWTP slowly starting up and easily crashing under conditions of shock loads such as high ammonia nitrogen, nitrate nitrogen, heavy metal ions, toxic and harmful organic matters because of the physiological and ecological characteristics of nitrifying bacteria which are low growth rate, long generation cycle, sensitive towards surrounding factors. Adding activated sludge can not fast remedy, which would affect the quality of the effluent. But bioaugmentation could improve the removal of the target pollutant and the sludge properties effectinely, in which, adding nitrifying biomass could efficiently implement bioaugmentation. Commercial bacterium agents is single strains, high cost and poor environmental compatibility, while nitrifying actived sludge is rich strains, low cost, better compatibility. At present, the purity and speed of nitrifying actived sludge enrichment are the most critical problem.This study investigated the shocks of the nitrification system of a WWTP in Yixing City and put forward some corresponding suggestions. In terms of high ammonia shock, we came up with highly reactive nitrifying activated sludge enrichment and bioaugmentation technology, and then examined the key factors control, continuous output and bioaugmentation feasibility of the enrichment system. Moreover, the optimal method of bioaugmentation in deal with high ammonia shock and rapidly starting up was evaluated from acceleration of nitrogen removal and predation on the microbial community systematically. Finally, the bioaugmentation effect of the enriched nitrifying activated sludge with the commercial bacterium agents was compared. The main results and conclusions are as fllows.(1)The number of the AOB and NOB in the WWTP of Yixing City were almost the same. Nitrosomonas and Nitrosococcus were the dominate AOB, meanwhile, Nitrobacter and Nitrospira were the dominate NOB. The shocks of the nitrification system were the high concentration of easily degradable organics and high ammonia nitrogen, while toxic and harmful organic and heavy metal ions were the potential shock factors. All these could be monitored by upstream enterprise and highly reactive nitrifying activated sludge bioaugmentation technology.(2)The nitrifying activated sludge enrichment reacter is submerged MBR. On day 81, the nitrification activity of nitrifying bacteria reached more than 2600 mgN/(L·d) stably and the rate of nitrification was 43.2 mgO2/g(MLSS)·h when the HRT was 4 h and the SRT was ∞(no desludging), which was above the literature reports level with the similar methods. The enriched nitrifying activated sludge, with Nitrosomonas and Nitrobacter as the dominate AOB and NOB, had the rich species and the number which was close to commercial bacterium agents. The enriched system could produce nitrifying activated sludge with 2800 mg NH4+-N/(L·d), 3.1×1011 nitrifiers/L and 16.3% ratio under 20 d SRT, which bioaugmented for the main nitrification process of the WWTP only need 8.57 d.(3)Packing was screened as to replace part of the organic carbon source and improve the purity of nitrifying bacteria. When the NH4+-N load was 3.0 kgNH4+-N/(m3·d), adding 30%(V/V)PVDF porous packing ring could improve nitrification activity of the sludge and system nitrification stability. Powder activated carbon with 1 g/L added dosage was useful for the system nitrification stability. The scores level dynamics can quantitative evaluation the equationtiny difference of each nitrifying sludge.(4)When used for nitrification system rapidly starting up, the enriched nitrifying activated sludge, with 10%( V/V) adding dosage, could make the intermittent aeration sequencing batch fast and stable starting up, in which ammonia nitrogen removal rate can be stable at more than 97% at least 30 d.(5)When used for municipal wastewater emergency treatment, the enriched nitrifying activated sludge, with 14%(V/V)adding dosage, ammonia nitrogen removal rate increased by 50.6% and 13% respectively compared with the control group after twice high ammonia nitrogen shock two days. And ammonia of the effluent could quickly meet the standard after stopped the shock. The effect of the bioaugmentation was brriliant, to some level, certain persistence. After bioaugmentation, the obvious species richness had an obviously increase, moreover, Nitrosomonas and Nitrobacter increased significantly together. Bioaugmentation made the dominate AOB unchanged, while the dominate NOB changed from Nitrospira to Nitrobacter. Under the same dosing quantity, the ammonia nitrogen removal rate of the group with nitrifying sludge was higher than the group with commercial bacterium agents 9.6% when shocked two days. Moreover, when the dosing of commercial bacterium agents was three times than nitrifying sludge, the ammonia nitrogen removal rate of the group with nitrifying sludge was higher than the group with commercial bacterium agents 5.5%. The compatibility and stability of the enriched sludge had distinctly advantage than commercial bacterium agents in resisting high ammonia shock.