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The nitrogen removal efficiency in constructed wetlands (CWs) was largely affected by the dissolved oxygen (DO). In this study, micro-aeration with different numbers of hollow fiber membrane modules (HFMEs) was adopted to increase the oxygen availability and improve the nitrogen removal efficiency in CWs under different air temperatures and differe...
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A lab-scale hybrid anoxic-oxic biofilm reactor (HAOBR) with one anoxic compartment and two oxic compartments in sequence was constructed to treat domestic wastewater in this study. Performance of the HAOBR was evaluated at 25°C and hydraulic retention time 12 hr with reflux ratio increased from 100% to 300% by stages. The results showed that COD,...
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... At present, the enhancement of nitrification at low temperatures in WWTPs mainly include the retrofitting of treatment process, e.g., the development of attached biofilm systems such as moving bed biofilm reactors, membrane bioreactors, and aerated biological filters to allow for slow-growing nitrifiers (Dong et al. 2011;Almomani et al. 2014) and adjustment of operating parameters (increasing dissolved oxygen or prolonging sludge retention time) (Wu et al. 2015a;Song et al. 2020). Although these methods can improve lowtemperature nitrification performance to some extent, their enhancement is too limited to solve the problem of low nitrification efficiency. ...
The development of an effective approach to improve low-temperature nitrification of domestic wastewater remains an important issue that needs to be urgently addressed. This study was intended to verify the feasibility of using iron scraps as an effective immobilization material to enhance nitrification activity in domestic wastewater-treatment systems at low temperatures. Iron scraps were tried and compared with one common immobilization material (PVA-SA embedded balls) in terms of low-temperature nitrification performances, anti-shock capacity, dynamics of microbial community, and economic costs. The results showed that compared with control, the average nitrification efficiency of iron scraps and PVA-SA embedded balls increased separately by 15.7% and 27.6% at low temperatures. Among these groups, the iron scrap-based group demonstrated the best anti-shock capacity and the smallest fluctuation (lower than 10%) with the shortening of HRT (hydraulic retention time) or the increase of inlet ammonium level. Nitrosomonas was found to be the dominant bacterial genera for these two immobilization materials. The increased costs of iron scraps and PVA-SA embedded balls were about ¥0.03 and ¥0.78 per ton of treated domestic wastewater. Taken together, iron scraps have some significant advantages including low costs, easy availability, and good anti-shock capacity, which make them a promising candidate for enhanced nitrification of domestic wastewater at low temperatures.
... Statistically analyzed data for the effects of the different concentrations of Fe 3 O 4 on NO 3 − -N removal and V DN by using SPSS 20.0 software evaluate the significance of data. Significance was established at p < 0.05 (Song et al. 2019). Office Excel 2016 (Microsoft, USA) was performed to analyze data and the graphs were plotted using Origin 8.5 for data visualization. ...
This work evaluates the impact of the different concentrations of Fe3O4 on nitrate removal and organic matters utilization in the sequencing batch reactors (SBRs) using the sludge alkaline digestion supernatant as external sludge carbon source. Results indicated that the optimal concentration of Fe3O4 was 1 g/L for enhancing denitrification with NO3--N removal efficiency of 93.13% (up to a 11.93% increase) and without NO2--N accumulation after 18 days. The changes of soluble chemical oxygen demand (SCOD), protein, and carbohydrate during denitrification process were analyzed to gauge the utilization of sludge fermentation products by denitrifiers. The SCOD was consumed for organisms involved in NO3--N removal and the Fe3O4 could promote the utilization of carbohydrate better than protein by denitrifiers during denitrification process. Denitrification rate (VDN) and the nitrate-to-nitrite transformation ratio (NTR), as the kinetics parameters, were also investigated in different concentrations of Fe3O4.
The start-up process, microbial communities, and metagenomic features of a micro-aerated anaerobic reactor for the treatment of sulfate wastewater were investigated. At a COD/SO4²⁻ ratio of 1.0 of the influent, the average COD, SO4²⁻ and NH4⁺-N removal rate in the micro-aerated anaerobic reactor was 93.43%, 34.97%, and 28.88%, respectively. However, with the COD/SO4²⁻ ratio increased from 1.0 to 1.5, the average COD removal rate reduced by 15.55% and the average removal rate of SO4²⁻ increased by 2.85%. When the COD/SO4²⁻ ratio was 1.5, the activities of sulfite reductase, acetate kinase, and coenzyme F420 were highest in the sludge, with average concentrations of 0.12 Um/L, 0.089 mol/L, and 0.00913 mmol/g, respectively. During the whole experiment, the fluorescence peak of coenzyme F420 appeared in the LB-EPS, while the peaks of tryptophan-like protein and tyrosine-like protein appeared in TB-EPS. Proteobacteria was the main phylum in all three stages, with relative abundances of 28.17%, 22.74%, and 19.94%, respectively. Methanosaeta was the main genus, with relative abundances of 8.98%, 5.64%, and 7.08%, respectively, in stages A, B, and C. Meanwhile, the relative abundance of the dissimilation sulfate reduction modules was 0.0083%, 0.0189%, and 0.0115%, which ensured the removal of sulfate in the micro-aerated anaerobic reactor.
