Effects of carbon source and C/N ratio on treatment of aquaculture wastewater by multiple microorganisms

Abstract

To address the problem of insufficient carbon source in the biological denitrification of aquaculture wastewater,and improve the efficiency of biological denitrification,this study tested the effects of six carbon sources and different C/N ratios,using the removal rate of ammonium nitrogen and accumulation rate of nitrite as indicators.Preliminary screening results of carbon sources showed that when glucose and glycerol were used as the carbon sources,there was clear nitrite accumulation,which was up to 12.4mg/L.When alcohols were used as the carbon source,the highest accumulation of nitrite was only 1.3mg/L.Rescreening results of carbon sources showed that different carbon sources and C/N ratios did not significantly impact the removal rate of ammonium nitrogen,which was up to 98.2% in the treatment groups,significantly higher than that in the control group(P0.05).When ethanol was used as the carbon source and C/N ratio was 3:1,the removal rate of total nitrogen,ammonia nitrogen and nitrate were especially high,up to 93.3%,98.9% and 91.8%,respectively,significantly higher than that in the control group(P0.05).Considering the practicality and economy of extra carbon sources,choosing ethanol as additional carbon of purifying aquaculture wastewater by multiple microorganisms,and relative C/N ratio was 3:1.Although the extra carbon could substantially increase the concentration of CODMn,but it may be rapidly degraded by multiple microorganisms within a short time.In addition,the extra carbon could improve the stability of pH value of aquaculture wastewater to be kept between 7.2-7.8.The results of the present study suggest that the extra carbon source could significantly improve water quality and biological nitrogen removal efficiency during wastewater purification process in recirculating aquaculture systems.