Influence of cell lysis by Fenton oxidation on cryptic growth in sequencing batch reactor (SBR): Implication of reducing sludge source discharge

Changes in microbial community during hydrolyzed sludge reduction

In this study, the effects of different enzymes (lysozyme, α-amylase and neutral protease) on sludge hydrolysis efficiency and microbial community in sequencing batch reactor (SBR) were introduced. The results showed that the hydrolysis efficiencies of the three enzymes were 48.5, 22.5 and 31%, respectively, compared with the accumulated sludge discharge of the blank control group. However, it has varying degrees of impact on the effluent quality, and the denitrification and phosphorus removal effect of the system deteriorates. The lysozyme that achieves the optimal sludge hydrolysis effect of 48.5% has the greatest impact on the chemical oxygen demand (COD), total nitrogen (TN), and nitrate nitrogen (NO3--N) of the effluent. The sludge samples of the control group and the groups supplemented with different enzyme preparations were subjected to high-throughput sequencing. It was found that the number of OTUs (Operational Taxonomic Units) of the samples was lysozyme > α-amylase > blank control > neutral protease. Moreover, the abundance grade curve of the sludge samples supplemented with lysozyme and α-amylase was smoother, and the community richness and diversity were improved by lysozyme and α-amylase. The species diversity of the sludge supplemented with lysozyme and neutral protease was great, and the community succession was obvious. The introduction of enzymes did not change the main microbial communities of the sludge, which were mainly Proteobacteria, Actinobacteria and Bacteroidetes. The effects of three enzyme preparations on sludge reduction and microbial diversity during pilot operation were analyzed, the gap in microbial research was filled, which provided theoretical value for the practical operation of enzymatic sludge reduction.

Integrating electrochemical pre-treatment with carrier-based membrane bioreactor for efficient treatment of municipal waste transfer stations leachate

An integrated process of electrochemical pre-treatment with carrier-based membrane bioreactor (MBR) was constructed for fresh leachate from waste transfer stations with high organic and NH₄⁺-N content. Results showed that within a hydraulic retention time 40 h, the removal efficiencies of chemical oxygen demand (COD), NH₄⁺-N, suspended solids (SS) and total phosphorus (TP) were over 98.5%, 91.2%, 98.3% and 98.4%, respectively, with the organic removal rate of 18.7 kg/m³. The effluent met the Grade A Standard of China (GB/T31962-2015). Pre-treatment contributed about 70 % of the degraded refractory organics and almost all the SS, with the transformation of the humic-like acid to readily biodegradable organics. Biotreatment further removed over 50% of nitrogen pollutants through simultaneous nitrification and denitrification (SND) and consumed about 30% of organics. Meanwhile, the addition of carriers in the oxic MBR enhanced the attached biomass and denitrification enzyme activity, alleviating membrane fouling.

Fenton oxidation treatment of oxytetracycline fermentation residues: Harmless performance and bioresource properties

The pharmaceutical factories of oxytetracycline (OTC) massively produce OTC fermentation residues (OFRs). The high content of residual OTC and antibiotic resistance genes in OFRs must to be considered and controlled at an acceptable level. This study therefore investigated the applicability of Fenton oxidation in OTC degradation and resistant gene inactivation of OFRs. The results revealed that Fe²⁺ as catalyzer could very rapidly activate H₂O₂ to produce HO^•, leading to instantaneous degradation of OTC. The optimum conditions for OTC removal were 60 mM H₂O₂ and 140 mg/L Fe²⁺ under pH 7. After Fenton oxidation treatment, the release of water-soluble polysaccharides, NO₃-N, and PO₄-P was enhanced, whereas for proteins and NH₃-N were reduced. Three soluble fluorescence components (humic, tryptophan-like, and humic acid-like substances) were identified through fluorescence spectra with parallel factor analysis, and their reduction exceeded 50% after Fenton oxidation. There were twelve intermediates and three degradation pathways of OTC in OFRs during Fenton process. According to toxicity prediction, the comprehensive toxicity of OTC in OFRs was alleviated via Fenton oxidation treatment. In addition, Fenton oxidation showed the ability to reduce antibiotic resistance genes and mobile genetic elements, and even tetO, tetG, intI1, and intI2 were eliminated completely. These results suggested that Fenton oxidation treatment could be an efficient strategy for removing OTC and resistance genes in OFRs.