1.
Effects of zinc oxide nanoparticles on sludge anaerobic fermentation: phenomenon and mechanism.
Jin, B, Yuan, Y, Zhou, P, Niu, J, Niu, J, Dai, J, Li, N, Tao, H, Ma, Z, Zhang, J, et al
Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering. 2020;(9):1094-1103
Abstract
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.
2.
A review on removing antibiotics and antibiotic resistance genes from wastewater by constructed wetlands: Performance and microbial response.
Liu, X, Guo, X, Liu, Y, Lu, S, Xi, B, Zhang, J, Wang, Z, Bi, B
Environmental pollution (Barking, Essex : 1987). 2019;(Pt A):112996
Abstract
Pollution caused by antibiotics has been highlighted in recent decades as a worldwide environmental and health concern. Compared to traditional physical, chemical and biological treatments, constructed wetlands (CWs) have been suggested to be a cost-efficient and ecological technology for the remediation of various kinds of contaminated waters. In this review, 39 antibiotics removal-related studies conducted on 106 treatment systems from China, Spain, Canada, Portugal, etc. were summarized. Overall, the removal efficiency of CWs for antibiotics showed good performance (average value = over 50%), especially vertical flow constructed wetlands (VFCWs) (average value = 80.44%). The removal efficiencies of sulfonamide and macrolide antibiotics were lower than those of tetracycline and quinolone antibiotics. In addition, the relationship between the removal efficiency of antibiotics and chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP) and ammonia nitrogen (NH3-N) concentrations showed an inverted U-shaped curve with turning points of 300 mg L-1, 57.4 mg L-1, 40 mg L-1, 3.2 mg L-1 and 48 mg L-1, respectively. The coexistence of antibiotics with nitrogen and phosphorus slightly reduced the removal efficiency of nitrogen and phosphorus in CWs. The removal effect of horizontal subsurface flow constructed wetlands for antibiotic resistance genes (ARGs) had better performance (over 50%) than that of vertical wetlands, especially for sulfonamide resistance genes. Microorganisms are highly sensitive to antibiotics. In fact, microorganisms are one of the main responsible for antibiotic removal. Moreover, due to the selective pressure induced by antibiotics and drug-resistant gene transfer from resistant bacteria to other sensitive strains through their own genetic transfer elements, decreased microbial diversity and increased resistance in sewage have been consistently reported. This review promotes further research on the removal mechanism of antibiotics and ARGs in CWs.
3.
[Biological phosphorus removal in sequencing batch reactor without anaerobic phase].
Wang, DB, Li, XM, Yang, Q, Zhang, J, Liu, YL, Liu, X, Jia, B, Zeng, GM, Liao, DX
Huan jing ke xue= Huanjing kexue. 2008;(7):1867-73
Abstract
The performance of phosphorus removal with a sequencing batch reactor was investigated by simulated municipal wastewater. The experimental results showed that phosphorus removal could be achieved in sequencing batch reactor without anaerobic phase, which was conventionally considered as a key phase for phosphorus removal. Phosphorus concentration in the effluent was 1.0 mg x L(-1) below after 4 h aeration, during which pH was 7.0 +/- 0.2. Which indicated the removal rate of phosphorus was above 90% when the COD and phosphorus concentrationof influent were about 400 mg x L(-1), 15-20 mg x L(-1), respectively. Intracellular storage of poly-phosphate (poly-P) was increasing in the aeration after decreasing in first hour aeration (the content of poly-P was 83.034 mg x g(-1) at the beginning of aerobic phase, 79.980 mg x g(-1) in first aeration and 83.086 mg x g(-1) in end), but the energy storage poly-beta-hydroxyalkanoates (PHA) was constant nearly and the content was very low (PHA concentration was about 5 mg x L(-1)). The researches indicated that phosphate could be transformed to poly-P by poly-phosphate-accumulating organisms without anaerobic zone and PHA, biological phosphorus removal was obtained by removing sludge with rich phosphorus, and this phenomenon could not be explained by conventional theory.