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In this study, the efficient recovery of high-quality short-chain fatty acids from wine vinasse and waste activated sludge mixtures was investigated. The highest accumulation of short-chain fatty acids reached 3502 mg chemical oxygen demand per litre with a proportion of 82.5% acetic and propionic acids in the reactor with a wine vinasse/waste activated sludge mixture under optimized fermentation conditions, while merely 236 and 618 mg chemical oxygen demand per litre was accumulated in the reactors with waste activated sludge and wine vinasse systems alone, respectively. The mechanisms of the exceptional short-chain fatty acids promotion were mainly attributed to the simultaneous increase of bioavailable substrates and the fermentative community. The general microbial activity, key enzymes responsible for short-chain fatty acids generation, and diversity and abundance of fermentative bacteria were all enhanced under optimum conditions, which resulted in the rapid hydrolysis and acidification of bioavailable substrates for short-chain fatty acids generation. Moreover, the dewaterability of fermentation residues was also enhanced due to the presence of wine vinasses as skeleton builders.

Evident synergistic effects of iron activated persulfate (Fe/PS) on the marked promotion of volatile fatty acids (VFAs) from waste activated sludge during anaerobic fermentation were reported. The maximal VFAs concentration was up to 2255 mg COD/L with the proportion of 72.8% acetic acid in the Fe/PS reactor while it was merely 120 and 517 mg COD/L in Fe and PS reactors, respectively. Fe/PS treatment could substantially improve the solubilization and hydrolysis processes via the combined chemical and biologic effects to provide sufficient bioavailable substrates for acidogenic bacteria. Meanwhile, the presence of Fe in Fe/PS reactors could alleviate the adverse effects of PS on environmental factors (i.e. ORP and pH) and simultaneously involve in the regulation of microbial growth and activities. The fermentative bacteria responsible for VFAs production were highly enriched and the activities of key acid-forming enzymes and ATP concentration were greatly improved in Fe/PS reactors. It was the overall improvement of bioavailable substrates, abundance and activities of acidogenic bacteria, and fermentation conditions that led to the high VFAs accumulation in Fe/PS reactors.

The study explored an approach to improve the deep denitrification of tail water in denitrifying biofilter (DNBF) by utilizing alternative carbon sources withdrawn from the anaerobic fermentation of soybean wastewater due to its abundance and low costs. It was found in the batch tests that the alternative carbon sources could be obtained from soybean wastewater rapidly under optimal conditions. The obtained carbon sources were mainly consisted of acetic and propionic acids. The denitrification efficiency reached above 91% with the addition of fermented soybean liquids (FSL) with C/N ratio of 5 which was comparable to that of the commercial acetate. Further analysis demonstrated that the FSL was advantageous over the commercial acetate on the formation of biofilms and microbial diversity in DNBF which accounted for the satisfying performance of DNBF on the pollutants removal. Moreover, the potential environ-economic benefits could be expected by utilizing FSL as the alternative carbon source for deep denitrification which exhibited certain prospects in large-scale application.

Two-stage aerobic coupled process consisted of anoxic, aerobic-1 with low DO and aerobic-2 with high DO (short for “A-LO-HO” process), was applied for post-treatment of poultry manure wastewater, which suffered by high ammonia nitrogen and high salinity. Outstanding NH4+-N removal efficiency of 99.5% was obtained, and the COD removal efficiency was about 75%, even under the severe stress. Multiple molecular technologies, include DGGE, real time PCR and high-throughput sequencing were applied to reveal the microbial community of the sludge. The reasonable distribution of the dominant bacteria Nitrosomonas and Nitrobacter would explain the synergistic effect of the partial nitrification in “A-LO” section and the completed nitrification in “HO” section. The microbial community and EPS analysis further confirmed the outstanding nitrifying ability, good salt-tolerant ability, and unaffected sedimentation property of the sludge with particular enhanced features which is acclimated for long time by the targeted coupled process and suitable for this kind of wastewater treatment.