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Excess sludge a resource-rich organic waste, can be solubilized by thermophilic enzymes to extract proteins and anaerobic digestion of methane production to reduce sludge and use resources. At the same time, it can improve new ideas to relieve the pressure of the energy industry. To solve the problems of low enzyme-producing activity of wild strains and low hydrolysis rate of ES, this study utilized UV-DES compound mutagenesis to screen dominant mutant strains under optimized conditions, which were added to ES hydrolysis reaction system. The results showed that UV-DES mutagenesis could effectively improve the ability of S-TE and promote the hydrolysis of ES. The protease activity of the mutant strain KT16 obtained by screening was 46.7% higher than that of the original strain DC8. KT16 effectively degraded insoluble organic matter, reduced the average particle size of ES, and increased the concentrations of extracellular proteins, polypeptides, and amino acids to 1731.8, 521.3, and 510 mg·L-1, respectively. This study will provide a reference for the resource utilized.

In order to improve the utilization rate of the surplus sludge, this experiment investigated the efficient hydrolysis of the residual sludge, explored the effect of sludge nitrogen source, analyzed the influence on the content of protein, amino acid, polypeptide and particle size of the sludge hydrolysis index, and the extraction conditions were optimized by response surface analysis. The maximum protein extraction rate of the residual sludge at the reaction pH of 60°C and =7. Here, the particle size of S sludge was gradually reduced, reduced by 1.1% by 500 m-100 um, 7.5% by 30-50 μ m, 5.4% by 10 μ m-30 μ m, and 0-10 μ As m decreases 13% and sludge increased 13% Nt particles become thinner, larger than surface area and more developed pore structure.

Highlights • Swine slaughterhouse waste produced a maximum methane yield of 999.2 mL/g VS. • Lipid hydrolysis led to serious accumulation of linoleic, oleic and palmitic acids. • Increase of palmitic acid produced by degradation of oleic acid was observed. • Predominant microorganisms were Clostridium , Syntrophomonas and Methanospirillum. Abstract This study investigated methane production, long-chain fatty acids (LCFAs) profile, and predominant microorganisms in anaerobic digestion (AD) of lipid-rich swine slaughterhouse waste (SSW). The maximum methane yield was 999.2 mL/g VS. LCFAs, as inhibitory hydrolysis products, accumulated first to 1165 mg/L on day 3, and then decreased sharply to 125.7 mg/L on day 9, and finally were degraded to 20 mg/L on day 27. Linoleic acid (C18:2), oleic acid (C18:1) and palmitic acid (C16:0) were the dominant LCFAs. The easy conversion of C18:1 to C16:0 compared with difficult degradation of C16:0 resulted in an increase of C16:0 on day 4–6. Predominant microorganisms were Clostridium , Syntrophomonas and Methanospirillum. This study proved the high methane potential of lipid-rich SSW and gained insights into the degradation process by analysis of intermediates of LCFAs and predominant microorganisms. The results can provide valuable guidance for efficient utilization of this waste to produce methane in future. [ABSTRACT FROM AUTHOR]

• Biochar improved the efficiency of anaerobic digestion of antibiotic residues. • BC and nZVI-BC increased the gas production efficiency by 20.75% and 15.50%, respectively. • The effect of nZVI-BC was greater than BC in reducing ammonia nitrogen content. • nZVI-BC significantly enhanced the removal of aad A, ant (2″)-Ⅰ, qacEdelta 1 and sul 1. To address the problem of antibiotic mycelial dreg (AMD) treatment and removal of antibiotic resistance genes (ARGs), this study adopted anaerobic digestion (AD) technology, and added biochar (BC) and biochar loaded with nanosized zero-valent iron (nZVI-BC) to promote the AD of AMD and enhance the removal of ARGs. Results showed that nZVI-BC was better than BC in promoting AD due to the hydrogen evolution corrosion and the synergistic effect of nZVI and BC. In addition, BC and nZVI-BC can enhance the oxidative stress response and reduce ammonia stress phenomenon, which significantly reduces the abundance of aad A, ant(2″) -Ⅰ, qacEdelta 1 and sul 1. In conclusion, the enhance effect of nZVI-BC is greater than BC. The removal efficiency rates of nZVI-BC on the above-mentioned four ARGs were improved by 33%, 9%, 24% and 11%. [ABSTRACT FROM AUTHOR]

China produces large amount of cotton stalk (CS) residues as agricultural biomass, which are incinerated on-site, causing air pollution. The high organic content of CS could be utilized for biogas production, but the direct digestion without pretreatment always leads to a low methane yield and biodegradability, due to the complicated structure of lignocellulose. In order to search best fitting pretreatment methods in effective anaerobic digestion (AD) of CS, effects of various pretreatments including KOH, NaOH, Ca(OH) 2 , alkali hydrogen peroxide (AHP), H 2 SO 4 , H 3 PO 4 and steam explosion (SE) were studied. It was seen that all treatments resulted in varying methane yields. Among all the pretreatments, acid pretreatment is not suitable for AD of CS. The results showed that the highest cumulative methane yield (CMY) of 192.4 mL·gVS -1 was obtained after 3% AHP pretreatment of CS, and the methane yield improved by 254.3% than the untreated CS. Therefore, AHP treatment was proven to be an efficient pretreatment technique. XRD and FTIR analyses had shown that pretreated CS had favorable structural changes. This research is beneficial in developing environment friendly and cost-effective pretreatment technologies to utilize CS for methane production in future application.