Effect of C/N on biogas production and organic and nitrogen removal performance in an EGSB system
An expanded granular sludge bed(EGSB)was used to treat high-strength organic wastewater containing both ammonia and nitrate.The effects of carbon to nitrogen ratio(COD/TN)on biogas production and nitrogen and carbon removal were mainly investigated.The 136-day operating results showed that C/N had no significant effect on COD removal,while significantly affected methanogenesis and TN removal efficiency.The time-course water quality determination confirmed nitrite accumulation and the coupling of nitrate partial reduction with anaerobic ammonia oxidation(Anammox).When C/N was 5.71,the coupling effect of Anammox with methanogenesis and nitrate partial reduction was optimal.With the rise of C/N,anammox activity decreased,while activities of methanogenesis and nitrate dissimilation reduction(DNRA)increased.C/N could significantly change the composition,content and organic groups of extracellular polymeric substance in sludge,and then affect the stability of sludge structure and microbial metabolic activity.The relative abundances of Candidatus Kuenenia and Candidatus Brocadia of Anammox bacteria were much higher at low C/N than those at high C/N.At high C/N,a large number of methanogens including Methanothrix,Methanolinea and Methanobacterium were detected,meanwhile,denitrifying and DNRA bacteria were co-existed.Microbial functional gene annotation proved that partial denitrification/DNRA promoted nitrite accumulation and thus Anammox occurrence,as well as methane production via acetic acid pathway.Finally,synchronous carbon and nitrogen removal mechanism was proposed at optimal C/N.
万方数据
维普
