Cassava stillage and its anaerobic fermentation liquid as external carbon sources in biological nutrient removal

Abstract

Abstract:The aim of this study was to investigate the effects of one kind of food industry effluent, cassava stillage and its anaerobic fermentation liquid, on biological nutrient removal (BNR) from municipal wastewater in anaerobicanoxic-aerobic sequencing batch reactors (SBRs). Experiments were carried out with cassava stillage supernatant and its anaerobic fermentation liquid, and one pure compound (sodium acetate) served as an external carbon source. Cyclic studies indicated that the cassava by-products not only affected the transformation of nitrogen, phosphorus, poly-β-hydroxyalkanoates (PHAs), and glycogen in the BNR process, but also resulted in higher removal efficiencies for phosphorus and nitrogen compared with sodium acetate. Furthermore, assays for phosphorus accumulating organisms (PAOs) and denitrifying phosphorus accumulating organisms (DPAOs) demonstrated that the proportion of DPAOs to PAOs reached 62.6% (Day 86) and 61.8% (Day 65) when using cassava stillage and its anaerobic fermentation liquid, respectively, as the external carbon source. In addition, the nitrate utilization rates (NURs) of the cassava by-products were in the range of 5.49-5.99 g N/(kg MLVSSh) (MLVSS is mixed liquor volatile suspended solids) and 6.63-6.81 g N/(kg MLVSSh), respectively. The improvement in BNR performance and the reduction in the amount of cassava stillage to be treated in-situ make cassava stillage and its anaerobic fermentation liquid attractive alternatives to sodium acetate as external carbon sources for BNR processes.

Factors influencing the accuracy of the denitrifier method for determining the oxygen isotopic composition of nitrate

“…The reason why isotopic measurement was poor at DO concentrations above 3 mg/L might be that excessive DO inhibits the activity of nitrite reductase and causes the accumulation of intermediate products (Fig. 3) (Bu et al, 2015). Kumar and Lin (2010) confirmed that the reductase in the denitrification process was sensitive to oxygen, and its activity was affected by DO concentrations.…”

Treatment of artificial secondary effluent for effective nitrogen removal using a combination of corncob carbon source and bamboo charcoal filter

“…Traditional carbon sources contain low molecular organic matter and sugars (Karanasios et al, 2016). Liquid organic matter, such as glucose, methanol, ethanol, and acetic acid, are preferred as they are easily used by denitrifying bacteria (Bu et al, 2015;Lim et al, 2006). Sugars such as glucose and sucrose are already in use as additional carbon sources.…”