Enrichment And Degradation Characteristics Of A Heterotrophic Nitrification Consortium In Coking Wastewater

Coking wastewater is a kind of toxic and organic wastewater in coking industry.The wastewater contains ammonia nitrogen,phenol,naphthalene,cyanide and other refractory substances.The concentrations of the pollutants are high.At present,the traditional activated sludge method has been the most widely used method for the treatment of coking wastewater.However,there are different degrees of excessive emissions of ammonia nitrogen and organic matter.Therefore,the removal of ammonia nitrogen has been received more and more attention and it is an urgency to find an effective method which can reduce the ammonia nitrogen and COD in the wastewater.The biological technology of nitrogen removal has been widely concerned because of it's easy realization,high efficiency and good cost-effectiveness.In recent years,the discovery of heterotrophic nitrification-aerobic denitrification bacteria has made the simultaneous nitrification and denitrification come true.And it made up for the shortcomings of low rate of nitrification and time-consuming in traditional nitrogen removal.In order to achieve the ideal removal effect,it is an important development direction to screen or construct the dominant consortium.A microbial consortium has more advantages than a single strain in the industrial application,both from the time and the stability of the treatment results.In this study,a heterotrophic nitrification consortium with excellent nitrogen removal ability named FG-06 was enriched from the activated sludge which collected from the coking wastewater treatment plant of Tisco.The consortium was analyzed by high throughput sequencing.The results showed that the proportions of Acinetobacter spp.and Pseudomonas spp.were higher,which were 54.37% and 26.52%,respectively.Studies on nitrogen removal characteristics of FG-06 showed that the optimum C/N and initial inoculant dosage for heterotrophic nitrifying was 16 and 1% separately,and the removal efficiency was about 82.36% in the medium with 800 mg/L ammonia nitrogen.When the salinity was increased from 0 to 50 g/L,the ammonia nitrogen removal efficiency by the consortium FG-06 could still reach 71.76%.In the pH experiment,the consortium FG-06 could play a good role in the degradation of ammonia nitrogen when the initial pH value of the culture medium was gradually changed from 5.0 to 10.0 and the removal efficiencies could reach more than 97%.Aerobic denitrification experiment showed that the consortium could remove nitrate and nitrite nitrogen,and the maximum removal rates were 4.53 and 6.53 mg/L/h,while the COD removal efficiencies were 96.30% and 95.73%,respectively.When cultured in simultaneous nitrification and denitrification medium,the consortium could remove ammonia nitrogen,nitrate and nitrite simultaneously.Study on the effect of phenol on heterotrophic nitrification performance of FG-06 showed that the addition of 200~800 mg/L phenol had almost no impact on the growth and nitrification performance of the consortium FG-06.And the phenol was degraded by the consortium gradually.The consortium could use phenol as carbon source for growth and metabolism.When the phenol concentration was 200 mg/L,500 mg/L,800 mg/L and 1000 mg/L,the removal efficiencies of ammonia nitrogen by consortium FG-06 were 95.08%,91.36%,80.34% and 27.89% separately.The removal efficiencies of phenol were 100%,93.90%,88.08% and 19.07% separately.Therefore,the simultaneous removal of ammonia nitrogen and phenol in coking wastewater may be realized by using the consortium.The raw wastewater experiment was conducted to investigate the removal effect by the consortium.Shaking flask test showed that the removal efficiencies of ammonia nitrogen and COD in coking wastewater were 98.41% and 83.69% separately with initial inoculant dosage of 3%,and the pH rose from 6.0 to 9.0.In the reactor experiment,the dissolved oxygen was controlled between 2~5 mg/L and the temperature was 23~30 °C.The sequencing batch reactor(SBR)was made of organic glass and the addition of bacteria was 2‰ after centrifugation.The blank system was with no addition of bacteria.The results showed that the maximum removal efficiencies of ammonia nitrogen and COD by the inoculation system were improved 15.87% and 6.17% respectively compared with the control system through the operation period of 50 days.