Effects of zinc oxide nanoparticles on sludge anaerobic fermentation: phenomenon and mechanism.

Zinc oxide nanoparticles (ZnO NPs) production and usage might lead to a large discharge of ZnO NPs into the natural environment, raising concerns of pollution and ecological security. The effects of ZnO NPs on waste activated sludge hydrolytic acidification and microbial communities were studied in semi-continuous fermentation systems. The fermentation performance of eight ZnO NPs concentrations including ZnO NPs normal [0.01, 0.1, 1 and 10 mg/g mixed liquor suspended solids (MLSS)] and ZnO NPs shock (10, 1000, 1000 and 10,000 mg/g MLSS) were discussed, and their biodegradability was also analyzed. The experimental results showed that proteins, polysaccharides and short-chain fatty acids were enhanced by ZnO NPs, particularly by ZnO NPs shock. Low ZnO NPs concentrations inhibited coenzyme 420 (F420) and dehydrogenase activities but enhanced α-glucosidase and protease activities. Illumina MiSeq sequencing revealed that ZnO NPs addition enriched Azospira, Ottowia and Hyphomicrobium but not Anaerolineaceae.

Response of extracellular polymeric substances and enzymatic activity to salinity for the waste activated sludge anaerobic fermentation process.

Salinity (NaCl) was used in waste activated sludge (WAS) anaerobic fermentation system which had been presented to greatly enhance the extracellular polymeric substance (EPS) production including protein and polysaccharide and short-chain fatty acids (SCFAs). Salinity enhanced soluble protein and polysaccharide (SB-EPS) release which was 4.04 times (protein) and 1.83 times (polysaccharide) compared to 0 g/L NaCl level. More important, salinity restrained the coenzyme 420 activity (F420), but increased the hydrolase activity. Abundant hydrolysis of substrate and highly active hydrolase led to abundant SCFA production. Pearson correlation coefficient showed that the protein became the main reaction substrate for SCFA generation.

New insights into the enhancement of biochemical degradation potential from waste activated sludge with low organic content by Potassium Monopersulfate treatment.

Waste activated sludge with low organic content (WAS-LOC) always led to the failure of anaerobic fermentation. A potentially practical technology based on SO4-, i.e. Potassium Monopersulfate (PMS) was used into WAS-LOC anaerobic fermentation system and had been presented to greatly improve both the intracellular and extracellular constituents, which improved the biological enzyme activity and produced a mass of short-chain fatty acids (SCFAs). Results showed that the maximal SCFAs production was 716.72 mg chemical oxygen demand (COD)/L (0.08 mg PMS/mg SS), which increased to 43.70 times comparing to that of 0.00 mg PMS/mg SS level (16.40 mgCOD/L). The activities of biological enzymes increased 1.42 times for protease, 4.38 times for α-glucosidase, 2.1 times for alkaline phosphatase, 1.70 times for acidic phosphatase and 1.37 times for dehydrogenase respectively comparing to natural fermentation system, but the coenzyme 420 was restrained prominently. PMS positively enriched the abundance of microbial community responsible for WAS-LOC hydrolysis and SCFAs production.