Mechanism Of Microbial Degradation Of Phenol And Ammonia Nitrogen In Drinking Water Sources And Biological Treatment Technology Research

Drinking water is an indispensable element for human survival,and drinking water safety is the most important of food safety.In recent years,seasonal ammonia and organic micro pollution was widespread in drinking water sources in Pearl River Delta city of China.Conventional water purification processes of drinking water including coagulation,sedimentation,filtration,disinfection can not remove organics and ammonia completely.Therefore,increasing biological pretreatment process could effectively and economically remove the trace organic pollutants and ammonia nitrogen in drinking water source.Based on this,we used high-throughput sequencing technology to study microbial diversity in drinking water biofilter.Meanwhile,we isolated indigenous phenol and ammonia degrader from drinking water biofilters.At the same time,proteomics and transcriptome were used to study the phenol degradation mechanism.A bioreactor was constructed by using the highly efficient degradation bacteria and the biological stability of the highly degrading bacteria in the water treatment process was studied.The main results are as follows:This study examines an acclimated bacterial community that degrades phenol.The enriched culture was observed to degrade over 80% of 300 mg/L phenol within 3 d.Based on the PCR denatured gradient gel electrophoresis(PCR-DGGE)profiles of bacteria from biological activated carbon(BAC),a shift in bacterial community structure was observed with phenol biodegradation.Moreover,the most effective phenol degrader corresponding to the main band in DGGE profile was isolated and identified as Acinetobacter sp.,according to phylogenetic analyses of the 16 S ribosomal ribonucleic acid(rRNA)gene sequences.This species also produces the most important component of the phenol-degrading mechanism,phenol hydroxylase,which has the potential to eliminate phenol.In order to reveal the phenol biodegradation molecular mechanism,we performed proteome and transcriptome analysis of Acinetobacter sp.DW-1 during phenol biodegradation.The results showed that Acinetobacter sp.DW-1 degrades phenol mainly by the ortho pathway because of the induction of phenol hydroxylase,catechol-1,2-dioxygenase.Furthermore,some novel candidate proteins(OsmC-like family protein,MetA-pathway of phenol degradation family protein,fimbrial protein and coenzyme F390 synthetase)and transcriptional regulators(GntR/LuxR/CRP/FNR/TetR/Fis family transcriptional regulator)were successfully identified to be potentially involved in phenol biodegradation.In particular,MetA-pathway of phenol degradation family protein and fimbrial protein showed a strong positive correlation with phenol biodegradation,and Fis family transcriptional regulator is likely to exert its effect as suppressor of gene expression.This study provides valuable clues for identifying global proteins and genes involved in phenol biodegradation and provides a fundamental platform for further studies to reveal the phenol degradation mechanism of Acinetobacter sp..High-throughput sequencing technology was used to study the microbial diversity in drinking water carbon sand filter.The results showed that the dominant bacteria in the carbon sand filter were Bacillus,Lactococcus,Enterococcus,Paenibacillus and Alkaliphilus etc.Microorganisms in carbon sand particles were enriched by phenol and an efficient phenol-degrading strain CS-1 was isolated.After identification by 16 SrRNA gene sequencing,the strain CS-1 belonged to Rhodococcus sp.and it could completely degrade 500 μg/L pehnol within 100 min.Moreover,immobilized Rhodococcus sp.CS-1 cells also exhibited a good ability to degrade phenol.According to the comparative transcriptome analysis we found that the phenol degradation pathway of Rhodococcus sp.CS-1was ortho-cleavage.,and it is first time to find that Rhodococcus sp.can catalyze aromatic hydrocarbon ring to crack by the pathway of protocatechuic acid 3,4-dioxygenase.High-throughput sequencing technology was used to study the microbial diversity in drinking water sand filter.The results showed that the dominant bacteria in sand filter were Nitrospira,Hyphomicrobium,Bacillus and Bradyrhizobium.Furthermore,a high abundance bacterium Bacillus SF-4 was isolated from sand filter,which exhibited a good ability to degrade ammonia nitrogen.Therefore,the application of indigenous bacterium SF-4 has great potential for removal of ammonia nitrogen from drinking water source.AOA and AOB amoA fluorescence quantitative results showed that ammonia oxidizing bacteria and archaea were generally distributed in sand filter,and the abundance of ammonia oxidizing archaea was higher than ammonia oxidizing bacteria in sand filters,which let us recognize the significant role of archaea in the nitrogen cycle in drinking water treatment system.To sum up,screening of indigenous phenol and ammonia nitrogen-degrading bacteria in drinking water system can provide excellent strains for strain resource library which is removal of micro-pollutants from drinking water source.It also provides a way for the screening of micro-pollutants degrading bacteria in drinking water.Through exploring the molecular metabolic mechanism of phenol degrading bacteria,it laid a theoretical foundation for the construction of phenol degrading engineering bacteria.The construction of a new type of micro-pollutant removal device and the stability study of functional bacteria in the actual water treatment process provide a reference for the engineering practice of functional bacteria in biological pretreatment process.