Enhancement of Sulfur Autotrophic Denitrification by Solid-State Carbon Source PHBV for Nitrate Removal of Aquaculture Wastewater

The aim of this study was to evaluate the effect of a solid slow-release carbon source (3-hydroxybutyrate-co-3-hydroxyvalerate, PHBV) on heterotrophic and sulfur autotrophic cooperative denitrification (HAD) of aquaculture wastewater. Batch tests were carried out to analyze the effect of different PHBV/S volume ratios in the range of 30-70% on the denitrification of synthetic aquaculture wastewater under a short hydraulic retention time (HRT). The performance of the HAD process showed that the NO3--N removal was increased with an increase in the PHBV/S volume ratio. When the PHBV/S ratio reached 70%, the average NO3--N concentration of effluent was 0.38 mg/L in the stable phase. The variation in pH and alkalinity showed that the average pH value and residual alkalinity were above 7.03 and 57.63 mg/L at the PHBV/S ratio of 50%. Based on the relationship between sulfate generation and nitrate removal under different ratios of PHBV/S, analysis of the proportion of autotrophic and heterotrophic denitrification (HD) showed that sulfur autotraophic denitrification (SAD) was enhanced at a PHBV/S ratio of 50%, and competition for nitrate substrates occurred between autotrophic and heterotrophic at a PHBV/S ratio of 70%.