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1.
J Hazard Mater ; 416: 125912, 2021 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-34492846

RESUMO

Emerging contaminants (ECs) in wastewater have recently attracted the attention of researchers as they pose significant risks to human health and wildlife. This paper presents the state-of-art technologies used to remove ECs from wastewater through a comprehensive review. It also highlights the challenges faced by existing EC removal technologies in wastewater treatment plants and provides future research directions. Many treatment technologies like biological, chemical, and physical approaches have been advanced for removing various ECs. However, currently, no individual technology can effectively remove ECs, whereas hybrid systems have often been found to be more efficient. A hybrid technique of ozonation accompanied by activated carbon was found significantly effective in removing some ECs, particularly pharmaceuticals and pesticides. Despite the lack of extensive research, nanotechnology may be a promising approach as nanomaterial incorporated technologies have shown potential in removing different contaminants from wastewater. Nevertheless, most existing technologies are highly energy and resource-intensive as well as costly to maintain and operate. Besides, most proposed advanced treatment technologies are yet to be evaluated for large-scale practicality. Complemented with techno-economic feasibility studies of the treatment techniques, comprehensive research and development are therefore necessary to achieve a full and effective removal of ECs by wastewater treatment plants.


Assuntos
Praguicidas , Poluentes Químicos da Água , Purificação da Água , Humanos , Eliminação de Resíduos Líquidos , Águas Residuárias/análise , Poluentes Químicos da Água/análise
2.
J Hazard Mater ; 416: 126206, 2021 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-34492968

RESUMO

Sludge lysate is an unavoidable and refractory liquid produced from the waste activated sludge hydrothermal pyrolysis, which contains plenty of hazardous refractory organic compounds and value-added organic resources. Here, the proof of concept for an integrated strategy that couples technically compatible pretreatment to microbial electrolysis assisted AD (ME-AD) system is investigated for sludge lysate treatment and resource recovery. The pretreatment process shows a positive effectiveness on the ME-AD by reducing the organic load and inhibitory matters, which promote the residual refractory organic compounds (Maillard reaction products and humic acid-like substances) and carbon sources further biodegradation and bio-transformation. Combining membrane separation with ME-AD increased not only both the yield and purity of methane to 268.76 mL CH4/g COD and 98%, respectively, but also the recovery of 70.0~82.4% crude proteins (9.1 ± 0.5 g/L) from sludge lysate. Alternatively, the alkaline precipitation combined with ME-AD enhanced the recovery efficiency of short-chain fatty acids (SCFAs). The visible decreasing in the unpleasant color of the effluents was observed, implying that the degradation of harmful refractory organic was almost eliminated in sludge lysate. This strategy is worthy to be developed in WWTP for sludge lysate treatment with considerable bio-resources recovery and refractory organics removal.


Assuntos
Metano , Esgotos , Anaerobiose , Reatores Biológicos , Eletrólise , Ácidos Graxos Voláteis , Eliminação de Resíduos Líquidos
3.
Water Sci Technol ; 84(5): 1059-1078, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34534106

RESUMO

The importance of water recovery and reuse is increasing day by day. Therefore, the use of advanced technologies is applied for the treatment and recovery of textile wastewater. The fact that ceramic membranes are resistant to the challenging characteristics of textile wastewater makes the use of ceramic membranes useful. Within the scope of this review, general information about the textile industry and treatment techniques are mentioned, as well as the properties of ceramic membranes and textile wastewater treatment. In the literature review made in this study, recent studies on the production of ceramic membranes and laboratory applications have been compiled. However, it has been observed that although the real-scale studies are relatively higher in industries such as the food and petrochemical industry, it is rather limited in the textile industry.


Assuntos
Indústria Têxtil , Purificação da Água , Cerâmica , Membranas Artificiais , Eliminação de Resíduos Líquidos , Águas Residuárias
4.
Artigo em Inglês | MEDLINE | ID: mdl-34444382

RESUMO

The rapid growth of the livestock and poultry industries has resulted in the production of a large amount of wastewater, and the treatment of this wastewater requires sustainable and environmentally friendly approaches such as phytoremediation. A substrate-free floating wetland planted with water dropwort (Oenanthe javanica), a common vegetable in Southeast China, was constructed to purify a lagoon with anaerobically and aerobically treated swine wastewater in Suqian, China. The average removal rates of total nitrogen, ammonium nitrogen, nitrite nitrogen, and chemical oxygen demand were 79.96%, 95.04%, 86.14%, and 59.91%, respectively, after 40 days of treatment. A total of 98.18 g∙m-2 nitrogen and 19.84 g∙m-2 phosphorus were absorbed into plants per harvest through the rapid growth of water dropwort biomass, and the nitrogen accumulation ability was similar to that observed of other plants, such as water hyacinth. In addition, the edible part of water dropwort was shown to comply with the Chinese National Food Sanitation Standards and be safe for human consumption. Its low soluble sugar content also makes it a suitable addition to the daily diet. Overall, substrate-free floating constructed wetlands planted with water dropwort could be more widely used for livestock wastewater purification and could be integrated with plant-livestock production in China because of its high removal efficiency and recycling utilization of water dropwort biomass.


Assuntos
Águas Residuárias , Purificação da Água , Animais , Biodegradação Ambiental , Gado , Nitrogênio , Fósforo , Suínos , Eliminação de Resíduos Líquidos , Áreas Alagadas
5.
Artigo em Inglês | MEDLINE | ID: mdl-34444611

RESUMO

The current study investigated the distribution of microbial populations and diversity in treated wastewater used for irrigation at the University of Limpopo Experimental Farm (ULEF), from different stages of post treatment disposal at Mankweng Wastewater Treatment Plant (MWTP) in Limpopo Province, South Africa. The study was arranged in a 4 × 5 factorial experiment, which studied the interactive effects of four collection points and five months of sampling, with borehole water used as a reference point. Water samples were analyzed for bacteria, helminths, and protozoa. All data were transformed and subjected to factorial analysis of variance. The site-time interactions were significant for Salmonella spp. and Ascaris lumbricoides, whereas collection point was significant for all variables. In conclusion, movement and storage of water post treatment at MWTP were able to improve the microbial quality of the treated wastewater disposed for irrigation at ULEF.


Assuntos
Águas Residuárias , Purificação da Água , Salmonella , Eliminação de Resíduos Líquidos , Água
6.
Artigo em Inglês | MEDLINE | ID: mdl-34444631

RESUMO

This research assessed a novel treatment process of winery wastewater, through the application of a chemical-based process aiming to decrease the high organic carbon content, which represents a difficulty for wastewater treatment plants and a public health problem. Firstly, a coagulation-flocculation-decantation process (CFD process) was optimized by a simplex lattice design. Afterwards, the efficiency of a UV-C/ferrous iron/ozone system was assessed for organic carbon removal in winery wastewater. This system was applied alone and in combination with the CFD process (as a pre- and post-treatment). The coagulation-flocculation-decantation process, with a mixture of 0.48 g/L potassium caseinate and 0.52 g/L bentonite at pH 4.0, achieved 98.3, 97.6, and 87.8% removals of turbidity, total suspended solids, and total polyphenols, respectively. For the ozonation process, the required pH and ferrous iron concentration (Fe2+) were crucial variables in treatment optimization. With the application of the best operational conditions (pH = 4.0, [Fe2+] = 1.0 mM), the UV-C/ferrous iron/ozone system achieved 63.2% total organic carbon (TOC) removal and an energy consumption of 1843 kWh∙m-3∙order-1. The combination of CFD and ozonation processes increased the TOC removal to 66.1 and 65.5%, respectively, for the ozone/ferrous iron/UV-C/CFD and CFD/ozone/ferrous iron/UV-C systems. In addition, the germination index of several seeds was assessed and excellent values (>80%) were observed, which revealed the reduction in phytotoxicity. In conclusion, the combination of CFD and UV-C/ferrous iron/ozone processes is efficient for WW treatment.


Assuntos
Ozônio , Poluentes Químicos da Água , Purificação da Água , Floculação , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água/análise
7.
Environ Res ; 200: 111777, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34333016

RESUMO

The presence of antibiotics in the wastewater is one of the important issues related to environmental management. In this study, antibiotics-degrading bacteria were screened from the enriched sewage sludge sample. Among the isolated bacterial strains, Bacillus subtilis AQ03 showed maximum antibiotic tolerance (>2000 ppm). The characterized strain B. subtilis AQ03 degraded sulfamethaoxazole and sulfamethoxine and the optimum nutrient and physical-factors were analyzed. B. subtilis AQ03 degraded 99.8 ± 1.3 % sulfamethaoxazole, and 93.3 ± 6.2 % sulfamethoxine. Sodium nitrate and ammonium chloride were improved antibiotics degradation (<90 %). The optimized conditions were maintained in a moving bed bioreactor for the removal of antibiotics and nutrients from the wastewater. The selected strain considerably produced proteases (109.4 U/mL), amylases (55.1 U/mL), cellulase (9.6 U/mL) and laccases (15.2). In moving bed reactor, sulfamethaoxazole degradation was maximum after 8 days (100 ± 1.5 %) and sulfamethoxazole (100 ± 0) was removed completely from wastewater after 10 days. In moving bed reactor, biological oxygen demand (92.1 ± 2.8 %), chemical oxygen demand (79.6 ± 1.2 %), nitrate (89.4 ± 3.9 %) and phosphate (91.8 ± 1.2) were removed from the wastewater along with antibiotics after 10 days of treatment. The findings indicate that the indigenous bacterial communities and the ability to survive in the presence of high antibiotic concentrations and xenobiotics. Moving bed bioreactor is useful for the removal of nutrients and antibiotics from wastewater.


Assuntos
Preparações Farmacêuticas , Águas Residuárias , Reatores Biológicos , Nutrientes , Esgotos , Eliminação de Resíduos Líquidos
8.
Artigo em Inglês | MEDLINE | ID: mdl-34338138

RESUMO

The use of advanced oxidative processes (AOPs) is an efficient alternative for the treatment of textile wastewaters. The aim of this study was to assess the dye removal efficiency of a Fenton-based degradation process followed by a polishing step using biochar prepared from rice husk. Six recalcitrant textile dyes - Reactive Red 195 (D1), Synolon Brown S2 (D2), Orange Remazol RGB (D3), Yellow Synozol K3 (D4), Reactive Orange (D5), and Reactive Black 5 (D6) - were treated with Fenton and photo-Fenton processes (with and without biochar polishing) under optimized conditions. The results showed a general efficiency ranking: photo-Fenton + biochar ≈ Fenton + biochar > photo-Fenton ≈ Fenton. The Fenton process was also efficient for the regeneration of the dye-saturated biochar. The photo-Fenton + biochar process achieved the following color removal percentages: D1 (98.8%), D2 (99.7%), D3 (98.9%), D4 (96.3%), D5 (94.2%) and D6 (94.8%). This process was applied to a real conventionally-treated textile wastewater and analysis showed a reduction in BOD (87.5% degradation), COD (62.5% degradation) and color (93.5% mean removal). These results reveal the possibility for the reuse of the treated water for non-potable industrial uses, for example, floor washing or the cleaning of machines and toilet areas.


Assuntos
Eliminação de Resíduos Líquidos , Poluentes Químicos da Água , Carvão Vegetal , Corantes , Peróxido de Hidrogênio , Oxirredução , Têxteis
9.
Water Res ; 202: 117461, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34343872

RESUMO

The highly hydrated colloidal structure of waste-activated sludge (WAS) is the main obstacle of enhanced dewatering for sludge volume minimization. Extracellular polymeric substances (EPS) maintain the colloidal stability of bio-flocs in a three-dimensional matrix due to bindings with bivalent cations (i.e., Ca2+ and Mg2+) and hydrophobic interactions. However, few studies specifically focused on the quantitative relationships among spatial distribution of EPS, microstructure of bio-flocs and fractions of bound water (e.g. vicinal water and interstitial water). Thus, there may be still some debates on whether and what extent of the lysis or flocculation of sludge flocs is optimal for the dewaterability improvement. This study applied the gradient addition of cation exchange resin (CER) to remove EPS-complexed cations and loosen the spatial distribution of EPS. Consequently, how the spatial extension of EPS layers with relief of complex cations influenced the particle size distribution, fractal dimension, interfacial free energy and water occurrence states of WAS was systematically investigated. The quartz crystal microbalance with dissipation (QCM-D) was also applied to analyze the water-EPS interactions with and without the presence of Ca2+ and Mg2+. All the results confirmed that the dispersed EPS adhering layers led to the higher fractal dimension (Df) but the lower space filling degree of bio-flocs. Also, the 4-fold reduction in the polar/acid-based interfacial free energy could be induced by the removal of cations from EPS matrix, which indicated the significant increase in hydrophobicity. Predictably, the fractions of vicinal water and interstitial water were dominated by the polar/acid-based interfacial free energy and pore structure of microbial aggregates, respectively, which were confirmed by the strong Pearson correlation (Rp>0.80, p-value<0.04). These findings are expected to provide the improved mechanistic insights into the relationship between water occurrence states and colloidal structure of WAS, and can serve as the basis for the optimal combination of various sludge conditioning approaches towards regulating aggregation states of bio-flocs.


Assuntos
Matriz Extracelular de Substâncias Poliméricas , Esgotos , Cátions , Floculação , Eliminação de Resíduos Líquidos , Água
10.
Water Res ; 202: 117465, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34358907

RESUMO

Thermal alkaline pretreatment (TAP) of waste activated sludge (WAS) before anaerobic digestion (AD) was reviewed. Focus of the review was on impact of TAP process parameters on biomethane yield (BY) and kinetics of AD and downstream dewatering. With higher initial biodegradability of untreated WAS, effect of TAP on BY decreases. Depending on initial biodegradability, BY increase of 22-97% is expected. Treatment temperatures below 100 °C showed to be as effective as temperatures higher than 100 °C in terms of BY increase. Alkali dosage and resulting initial pH have a significant effect on BY increase and showed to have an optimum range of 40-60 mg NaOH per g total solids (TS) of sludge. It is advised that alkali is dosed based on solids content in WAS and monitored by pH. Treatment time of 1.5-5 h is sufficient for an effective low temperature TAP (T < 100 °C), with longer treatment times showing no positive impact on BY increase. Load of sludge liquor with organics and nutrients increases with more intensive TAP conditions. Despite kinetic enhancement of hydrolysis step in AD, more research is needed to clarify if TAP improves kinetics of entire AD process which determines required digester volume. Impact of TAP on dewaterability of digestate is ambiguous and needs more investigation using standardized methods, also with regards to potential effects on polymer demand. Findings of experimental studies were reflected against available data from commercialized TAP process of Pondus®, throughout review. Finally, important process design parameters of TAP such as input TS and point of alkali dosage are discussed and recommendations for future research are presented.


Assuntos
Biocombustíveis , Esgotos , Anaerobiose , Hidrólise , Metano , Eliminação de Resíduos Líquidos
11.
Water Res ; 202: 117459, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34358908

RESUMO

Current practice to enhance resilience in Water Resource Recovery Facilities (WRRFs) is to ensure redundancy or back-up for most critical equipment (e.g. pumps or blowers). Model-based assessment allows evaluation of different strategies for quantitatively and efficiently enhancing resilience and justifying the allocation of resources. The goal of this study is to provide guidance for the development of tailored deterministic models of full-scale WRRFs. A framework for model-based resilience assessment is proposed that provides guidance on data collection, model selection, model calibration and scenario analysis. The framework is embedded into the Good Modeling Practice (GMP) Unified Protocol, providing a new application for resilience assessment and an initial set of stressors for WRRFs. The usefulness of the framework is illustrated through a resilience assessment of the WRRF of Girona against power outage. Results show that, for the Girona facility, limited energy back-up can cause non-compliance of WRRF discharge limits in the case of a blower power shut-down of 6 h, and around 12 h when the blower shut-down is also combined with a shut-down of the recirculation pumps. The best option to enhance resilience would be increasing the power back-up by 218%, which allows the plant to run with recirculation pumps and blowers at minimum capacity. In such a case, resilience can be further enhanced by manipulating the air supply valves to optimise the air distribution, to balance oxygen needs in each reactor with the overall system pressure. We conclude that, with industry consensus on what is considered an acceptable level of resilience, a framework for resilience assessment would be a useful tool to enhance the resilience of our current water infrastructure. Further research is needed to establish if the permit structure should accommodate levels sof functionality to account for stress events.


Assuntos
Purificação da Água , Recursos Hídricos , Oxigênio , Eliminação de Resíduos Líquidos , Águas Residuárias
12.
Water Res ; 202: 117452, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34358910

RESUMO

A comprehensive dataset of pollutant concentrations in German urban wastewater systems is available from recently completed monitoring projects. It contains up to 1000 concentration values for each of 79 substances in wastewater treatment plant (WWTP) effluents from 49 sites, and up to 157 values for each of 95 substances in combined sewer overflows (CSOs) from 12 sites. WWTP influents and stormwater outfalls were sampled to a lesser extent. All sampling methods were harmonised and aimed at collecting event or multi-day composite samples over periods of ≥1 year. Among the substances analysed were biocides and pesticides, polycyclic aromatic hydrocarbons, perfluorinated alkyl substances, metals, pharmaceuticals, benzotriazoles, phenols, acesulfame, di-(2-ethylhexyl)phthalate, and hexabromocyclododecanes. Occurrence, concentration ranges, and removal rates of selected WWTPs are presented. CSOs can be confirmed as an important pathway of metals and PAH to receiving waters when compared to WWTPs on the basis of annual per capita loads. The derived volume-weighted site mean concentrations are qualified to be used as representative input data for estimation of average substance emissions in large areas, e.g. on river basin scale, if no site-specific data are available. As such, they will contribute to the development of strategies to reduce substance emissions, taking into account not only WWTPs but also stormwater-related discharges.


Assuntos
Hidrocarbonetos Policíclicos Aromáticos , Poluentes Químicos da Água , Purificação da Água , Monitoramento Ambiental , Rios , Eliminação de Resíduos Líquidos , Águas Residuárias
13.
J Environ Manage ; 296: 113370, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34351289

RESUMO

Herein we proposed an ecology model, based on a non-steady-state mass balance (16S rRNA MiSeq reads normalized by volatile suspended solids), to quantify microbiome responses to disturbances in wastewater bioreactors. Rather than focusing on the most abundant microbial groups commonly used in the literature, the goal of the model was to identify active species within the community. The model incorporated the temporal changes of operational taxonomic units following a disturbance, through considering the density and type of genotypes in the influent entering the bioreactor, in the effluent leaving the bioreactor, growing in the bioreactor, and in the waste sludge discharged from the bioreactor continuously or instantaneously, as well as the prior microbial community and the sludge characteristics. One application of this model demonstrated that significant differences existed between the key populations responding to an increasing organic loading rate and the dominant species in a high-rate thermophilic upflow anaerobic sludge blanket reactor.


Assuntos
Microbiota , Águas Residuárias , Anaerobiose , Reatores Biológicos , Microbiota/genética , RNA Ribossômico 16S/genética , Esgotos , Eliminação de Resíduos Líquidos
14.
Water Sci Technol ; 84(3): 632-643, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34388123

RESUMO

The water body inside the constructed wetland is affected by various factors, and the flow state is relatively complicated. There will always be a certain degree of low velocity area and rapid outflow phenomenon, which makes part of the space in the wetland unable to be effectively used. Based on Computational Fluid Dynamics (CFD) technology, this paper uses Fluent's porous media model and discrete phase model to establish a hydrodynamic model of up and down baffled subsurface flow constructed wetland system. The internal flow field of the wetland is simulated, and the hydraulic performance of different baffle settings and substrate laying methods in the wetland is systematically evaluated. The results show that when the number of baffles is the same, the hydraulic efficiency is higher when the first baffle is located on the lower part of the substrate. Compared with the position of the baffle, the increase in the number of baffles does not significantly improve the hydraulic efficiency of the constructed wetland. The substrate layer thickness ratio has a significant effect on the two parameters of the variance of the hydraulic residence time distribution (σ2) and the flow divergence (σ02). By increasing the thickness of the middle substrate, the low flow rate phenomenon caused by the small porosity substrate area of the upper layer and the rapid outflow phenomenon of the lower substrate can be improved to a certain extent, the utilization efficiency of the middle substrate layer is improved, and the hydraulic performance is increased. The research results are of great significance for improving the utilization of wetland space and ensuring its efficient decontamination and purification function.


Assuntos
Purificação da Água , Áreas Alagadas , Simulação por Computador , Hidrodinâmica , Eliminação de Resíduos Líquidos
15.
Water Sci Technol ; 84(3): 752-762, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34388132

RESUMO

In this study, an electro-oxidation (EO) process using graphite electrodes as electrode pairs was used for the removal of chemical oxygen demand (COD), ammoniacal nitrogen (NH4+-N), and color from real textile printing wastewater. The effects of solution pH, sodium chloride (NaCl) dosage, sodium hypochlorite (NaOCl), which is the oldest and still most important chlorine-based bleach, dosage, and oxidation time were investigated on the removal efficiencies. Operating conditions for the EO reactor were applied to current density 1 mA/cm2, distance between the electrodes: 2 cm, 150 min operation time, and stirring speed of 500 rpm. At optimum conditions: pH 9.5, applied current density 1 mA/cm2, NaCl dosage of 8 g/L, NaOCl dosage of 44.4 mg/L and 150 min electro-oxidation time, the obtained removal efficiencies were 86.5% and 91.1% for chemical oxygen demand (COD) and ammoniacal nitrogen, respectively. Efficiency was increased to 91.1% for ammoniacal nitrogen from 21.7% after applying EO combined with NaOCl addition compared to individual NaOCl addition.


Assuntos
Águas Residuárias , Poluentes Químicos da Água , Análise da Demanda Biológica de Oxigênio , Eletrodos , Nitrogênio , Oxirredução , Impressão Tridimensional , Cloreto de Sódio , Têxteis , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água/análise
16.
Huan Jing Ke Xue ; 42(9): 4296-4303, 2021 Sep 08.
Artigo em Chinês | MEDLINE | ID: mdl-34414727

RESUMO

This study used vertical and horizontal subsurface constructed wetlands with continuous inflow, to compare and analyze the effects of four hydraulic residence times on the removal efficiency of conventional pollutants. Using the optimal hydraulic retention time, the two types of wetlands were examined in terms of the stromal layer nitrification, denitrification, and ammonia oxidation abundance of functional genes, as well as the intensity of nitrification and denitrification. In addition, redundancy analysis and variance decomposition analysis were used to determine the main factors affecting nitrogen removal in the two kinds of wetlands, so that targeted improvement measures can be suggested. The best removal efficiency of conventional pollutants (COD, TP, TN, and NH4+-N) was achieved with a hydraulic retention time of 24 h, resulting in a removal rate of more than 70%. With a 24 h retention time, the removal rate of NH4+-N and TN and the intensity of nitrification and denitrification exhibited a gradually decreasing trend along the flow direction. Among the three functional genes, the abundance of denitrification functional genes (nirS) was much higher than that of nitrification functional genes (nxrA) and ammonia oxidation functional genes (AOB-amoA). In this study, the nitrogen removal ability of the two subsurface flow constructed wetlands was jointly affected by environmental factors and microbial factors, among which microbial factors contributed the most to nitrogen removal (55% and 48%). In addition, the removal rates of TN and NH4+-N were proportional to DO, specific surface area of substrate, COD concentration, as well as nitrification and denitrification functional genes, but inversely proportional to pH. Therefore, in order to improve the nitrogen removal efficiency of both systems, the amount of dissolved oxygen and carbon sources in the substrate layer should be increased, while the pH value should be appropriately reduced. Moreover, the horizontal subsurface constructed wetland significantly improves the nitrogen removal efficiency of the system, as the substrate layer has a larger specific surface area. This study provides a theoretical basis for the design of constructed wetlands and the selection of an optimal hydraulic residence time. Quantitative analysis of nitrogen removal pathways is of great significance for understanding the nitrogen removal mechanism and improving the nitrogen removal rate in constructed wetlands.


Assuntos
Poluentes Ambientais , Áreas Alagadas , Desnitrificação , Nitrogênio/análise , Eliminação de Resíduos Líquidos
17.
Huan Jing Ke Xue ; 42(9): 4406-4413, 2021 Sep 08.
Artigo em Chinês | MEDLINE | ID: mdl-34414740

RESUMO

In this study, domestic sewage was used to inoculate mature short-cut nitrification denitrifying phosphorus removal particles, which were cultivated and matured under artificial water. The operation of the short-cut nitrification denitrifying phosphorus removal system was optimized using different aerobic/anoxic durations combined with zoned sludge discharge. The results showed that regulating the aerobic/anoxic duration, in combination with zoned sludge discharge, can realize the stable operation of the system. In the later stable period, the effluent COD concentration was below 50 mg·L-1, the effluent TN concentration was below 15 mg·L-1, the TN removal rate reached about 83% and remained stable, the effluent P concentration was below 0.5 mg·L-1, and the average P removal rate was 93.72%. At the same time, zoned sludge discharge (70% top sludge and 30% bottom sludge) can be used to screen out microorganisms, maintain good nitrosation and phosphorus removal performance, limit the particle size distribution, and ensure the growth advantages of AOB and DPAOs. Increases in the anoxic duration improved the growth rate of anoxic heterotrophic bacteria, causing them to secrete more EPS and ensuring granular sludge improvements and continued stability.


Assuntos
Fósforo , Esgotos , Reatores Biológicos , Nitrificação , Nitrogênio , Eliminação de Resíduos Líquidos
18.
Sci Total Environ ; 790: 148212, 2021 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-34380271

RESUMO

Increasing attention is being paid to the environmental impacts of wastewater treatment plant (WWTP) effluent. In this study, comprehensive environmental impact analyses (EIAs) were performed for the secondary treatment processes, tertiary treatment processes, and entire plants at five full-scale WWTPs in Kunming, China. The EIAs took into account greenhouse gas (GHG) emissions, potential for the effluent to cause eutrophication, ecological risks posed by endocrine disrupting compounds (EDCs) in treated effluent, and the risks posed by heavy metals in excess sludge. A comprehensive assessment toward environmental sustainability was performed using a fuzzy approach. The results indicated that the biological treatment process made the largest contribution (>68% of the total) of the secondary treatment processes to GHG emissions and that electricity consumption made the largest contribution (>64% of the total) of the tertiary treatment processes to GHG emissions. Large numbers of EDCs were removed during the secondary treatment processes, but the potential ecological risks posed by EDCs still require attention. High mercury concentrations were found in excess sludge. The plant that removed the largest proportion of pollutants and produced effluent posing the least ecological risks gave the best comprehensive EIA performance.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Meio Ambiente , Monitoramento Ambiental , Eliminação de Resíduos Líquidos , Águas Residuárias , Poluentes Químicos da Água/análise
19.
Artigo em Inglês | MEDLINE | ID: mdl-34360363

RESUMO

Herein, the responses of the operational performance of a membrane bioreactor (MBR) with a high ammonium-nitrogen (NH4+-N) load and microbial community structure to increasing carbon to nitrogen (C/N) ratios were studied. Variation in the influent C/N ratio did not affect the removal efficiencies of chemical oxygen demand (COD) and NH4+-N but gradually abated the ammonia oxidization activity of sludge. The concentration of the sludge in the reactor at the end of the process increased four-fold compared with that of the seed sludge, ensuring the stable removal of NH4+-N. The increasing influent COD concentration resulted in an elevated production of humic acids in soluble microbial product (SMP) and accelerated the rate of membrane fouling. High-throughput sequencing analysis showed that the C/N ratio had selective effects on the microbial community structure. In the genus level, Methyloversatilis, Subsaxibacter, and Pseudomonas were enriched during the operation. However, the relative abundance of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) involved in nitrification declined gradually and were decreased by 86.54 and 90.17%, respectively, with influent COD increasing from 0 to 2000 mg/L. The present study offers a more in-depth insight into the control strategy of the C/N ratio in the operation of an MBR with a high NH4+-N load.


Assuntos
Amônia , Microbiota , Reatores Biológicos , Carbono , Nitrogênio , Esgotos , Eliminação de Resíduos Líquidos
20.
Chemosphere ; 277: 130244, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34384173

RESUMO

The recovery and utilization of organic matter in municipal wastewater are essential for the establishment of a sustainable society, such that these factors have drawn significant recent attention. The up-concentration of organic matter via direct membrane filtration (DMF), followed by anaerobic digestion, is advantageous over the treatment of the entire wastewater by an anaerobic process, such as an anaerobic membrane bioreactor (AnMBR). However, the occurrence of severe membrane fouling in the DMF is a problem. In this study, DMF was carried out at an existing wastewater treatment plant to attempt long-term operation. A combination of vibration of membrane modules, short-term aeration, and chemically enhanced backwash (CEB), with multiple chemicals (i.e., the alternative use of citric acid and NaClO), was found to be effective for the mitigation of membrane fouling in DMF. Furthermore, switching the feed from influents to effluents in the primary sedimentation basin significantly mitigated membrane fouling. In this study, in which microfiltration membrane, with a nominal pore size of 0.1 µm, was used, ∼75% of the organic matter in raw wastewater was recovered, with the volumetric concentration of wastewater by 50- or 150-fold. Organic matter recovered by DMF had significantly higher potentials for biogas production than the excess sludge generated from the same wastewater treatment plant. An analysis of the energy balance (i.e., the energy used for DMF and recovered by DMF) suggests that the proposed DMF can produce a net-positive amount of electricity of ∼0.3 kWh from 1 m3 of raw wastewater with a typical strength (chemical oxygen demand of 500 mg/L).


Assuntos
Eliminação de Resíduos Líquidos , Águas Residuárias , Anaerobiose , Reatores Biológicos , Filtração , Membranas Artificiais , Esgotos
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