RESUMEN
To address the increasing issue of antibiotic wastewater, this study applied a static magnetic field (SMF) to the activated sludge process to increase the efficiency of tetracycline (TC) removal from swine wastewater and to reveal its enhanced mechanisms. The results demonstrated that the SMF-modified activated sludge process could achieve almost complete TC removal at sludge loading rates of 0.3 mg TC/g MLSS/d. Analysis of zeta potential and extracellular polymeric substances composition of the activated sludge revealed that SMF increased electrostatic interactions between TC and activated sludge and made activated sludge has much more binding sites, finally resulting in the increased TC biosorption. Metagenomic analysis showed that SMF promoted the enrichment of ammonia-oxidizing bacteria, TC-degrading bacteria, and aromatic compounds-degrading bacteria; it also enhanced ammonia monooxygenase- and cytochrome P450-mediated TC metabolism while upregulating functional genes associated with oxidase, reductase, and dehydrogenase - all contributing to increased TC biodegradation. Additionally, SMF mitigated the enrichment and spread of antibiotic resistance genes (ARGs) by decreasing the abundance of potential hosts of ARGs and inhibiting the upregulation of genes encoding ABC transporters and putative transposase. Based on these findings, this study demonstrates that magnetic field is an enhancement strategy with great potential to relieve the harmful impacts of the growing antibiotic wastewater problem on human health and the ecosystem.
Asunto(s)
Farmacorresistencia Microbiana , Campos Magnéticos , Aguas del Alcantarillado , Tetraciclina , Tetraciclina/farmacología , Farmacorresistencia Microbiana/genética , Antibacterianos/farmacología , Aguas Residuales/química , Animales , Eliminación de Residuos Líquidos/métodos , Bacterias/genética , Bacterias/metabolismo , Biodegradación Ambiental , PorcinosRESUMEN
This study aimed to explore whether the "window" effect of static magnetic field (SMF) on nitrous oxide (N2O) emission from the biological nitrogen removal process at low temperature existed and reveal its biological mechanism at the gene level. Four sequencing batch reactors (SBRs) with SMFs of 0, 10, 45, and 75 mT were operated continuously for 110 days at 10 °C and the lowest N2O-Gas cumulative emission (5.50 mg N/day) and N2O conversion rate (4.28 %) in 45 mT SMF-SBR verified the existence of the "window" effect. In 45 mT SMF-SBR, nearly all enzymatic activities related to N2O reduction and corresponding functional gene abundances improved significantly. Metagenomic high-throughput sequencing analysis revealed that Alicycliphilus denitricans, Paracoccus denitrificans, Rhodopseudomonas palustris, Pseudomonas stutzeri, and Dechloromonas aromatica, as species related to N2O reduction, could be separately enriched by applying suitable SMF intensity. Gene functions annotation based on KEGG and CAZy databases indicated that SMF not only accelerated the rate of free ammonia into ammonia-oxidizing bacteria and electrons delivered to the corresponding denitrification reductases, but also enhanced the degradation of complex organic matter into smaller molecules, and thus reducing the production of N2O via nitrifier denitrification and incomplete denitrification pathways at 10 °C. These findings provided a guideline and presented a blueprint of ecophysiology for the future application of magnetic field to the reduction of N2O emission in wastewater treatment plants in the cold region.
Asunto(s)
Desnitrificación , Óxido Nitroso , Betaproteobacteria , Reactores Biológicos , Campos Magnéticos , Nitrificación , Nitrógeno , Óxido Nitroso/análisis , Rhodopseudomonas , Aguas del Alcantarillado , TemperaturaRESUMEN
This study aimed to investigate the effects and biological mechanism of external static magnetic fields (SMFs) on enhancing nitrogen removal at different influent ammonium nitrogen (NH4+) concentrations. Four sequential batch reactors (SBRs) with SMFs of 0, 15, 30, and 50 mT were operated continuously for 196 days, during which the influent NH4+-N concentration increased stepwise as 50, 100, 350, and 600 mg L-1. The results showed that 50 mT had optimum effects on enhancing nitrogen removal, especially at high NH4+-N concentrations (350 and 600 mg L-1). The biological mechanism by which SMF influences nitrogen removal varies depending on the NH4+ concentration. At low NH4+-N concentrations (50 and 100 mg L-1), a field of 50 mT increased key enzyme activities and corresponding functional gene abundances. Additionally, it further improved functional bacterial abundances, which involved nitrifying and denitrifying bacteria at high NH4+ concentrations. These findings could provide guidance for the selection of optimum SMF intensity at different influent NH4+ concentrations.
Asunto(s)
Compuestos de Amonio , Nitrógeno , Reactores Biológicos , Desnitrificación , Campos Magnéticos , Aguas del AlcantarilladoRESUMEN
Granular size plays a key role in the performance of the aerobic granular sludge (AGS). As the diameter of the granule increases, stratification may begin to appear due to the increase in mass transfer resistance. Aerobic granules harvested from a lab-scale anaerobic-aerobic sequencing batch reactor (AO-SBR) were classified into three categories according to their size: (a) 0.15-0.28â mm, (b) 0.28-0.45â mm and (c) larger than 0.45â mm. In this study, the categories were called small-size, medium-size and large-size granules, respectively. A fraction of the different forms of phosphate and denitrification efficiency was investigated in each category. Results show that small-size granules present much more easily mobile phosphorus than other granules. Moreover, the denitrification performance has been tested by using dumping and trickling patterns for COD and NO3--N feeding. The results demonstrated that the large-size granules exhibit poor denitrification rates, as opposed to the medium-size granules. Therefore, medium-size granules, with a size of 0.28-0.45â mm, are regarded as the most suitable granular size for AGS in this experiment from the perspective of denitrification and phosphorus removal.
Asunto(s)
Fósforo , Aguas del Alcantarillado , Aerobiosis , Reactores Biológicos , Desnitrificación , Nitrógeno , Eliminación de Residuos LíquidosRESUMEN
Managing wastewater treatment plant (WWTP) based on respirometric analysis is a new and promising field. In this study, a multi-dimensional respirogram space was constructed, and an important index Res/t (ratio of in-situ respiration rate to maximum respiration rate) was derived as an alarm signal for the effluent quality control. A smaller Res/t value suggests better effluent. The critical R'es/t value used for determining whether the effluent meets the regulation depends on operational conditions, which were characterized by temperature and biomass ratio of heterotrophs to autotrophs. With given operational conditions, the critical R'es/t value can be calculated from the respirogram space and effluent conditions required by the discharge regulation, with no requirement for calibration of parameters or any additional measurements. Since it is simple, easy to use, and can be readily implemented online, this approach holds a great promise for applications.
Asunto(s)
Reactores Biológicos , Eliminación de Residuos Líquidos , Biomasa , Aguas del Alcantarillado , Aguas ResidualesRESUMEN
Robustness of an activated sludge system, describing uncertainty and operational risk, was evaluated using the absence or presence of calcium-induced enhancement of respiration (CaER) effect. Generally, the fast-growing system was susceptible to external environmental variations, of which the sludge exhibited significant CaER effect under normal operational conditions, while the slow growing system showed less significant CaER effect. However, sludge in both systems exhibited CaER effect under stressed conditions of decreasing temperature or ammonia shocking. Therefore, the absence of CaER effect indicates a more robust system, while the presence of CaER effect indicates a susceptible system. Additionally, a method to identify safe and dangerous shocking was established by a hybrid usage of absence or presence of CaER effect and recovery index (RI) curve type. The evaluation of robustness could help determining when adjustment should be really taken to cope with the uncertainty, and thus holds a high promise for field application.