Search

Abstract The tailwater from wastewater treatment plants serves as an important water resource in arid regions, alleviating the conflict between supply and demand. However, the effects of different tailwater discharge proportions on microbial community dynamics remain unclear. In this study, we investigated the effects of different tailwater discharge proportions on the water quality and microbial community characteristics of sediments in receiving water bodies under controlled conditions (WF-1, WF-2, WF-3, WF-4, and WF-5, containing 0% tailwater + 100% natural water, 25% tailwater + 75% natural water, 50% tailwater + 50% natural water, 75% tailwater + 25% natural water, and 100% tailwater + 0% natural water, respectively). Microbial co-occurrence networks and structural equation model were used to unveil the relationship between microbial communities and their shaping factors. Results showed that distinct microbial community compositions were found in the sediments with low- ( 50%) proportions of tailwater. Specifically, WCHB1-41 and g_4-29–1, which are involved in organic degradation-related functions, were the key genera in the high-proportion cluster. A total of 21 taxa were more abundant in the low-proportion ( 50%). Moreover, higher modularity was observed in the low-proportion. Total phosphorus directly affected while ammonia nitrogen indirectly affected the microbial community structure. Our findings support the distinct heterogeneity of microbial communities driven by tailwater discharge in receiving water bodies, and further confirmed that high-proportion tailwater depletes sensitive microbial communities, which may be avoided through scientific management.

The tailwater from wastewater treatment plants serves as an important water resource in arid regions, alleviating the conflict between supply and demand. However, the effects of different tailwater discharge proportions on microbial community dynamics remain unclear. In this study, we investigated the effects of different tailwater discharge proportions on the water quality and microbial community characteristics of sediments in receiving water bodies under controlled conditions (WF-1, WF-2, WF-3, WF-4, and WF-5, containing 0% tailwater + 100% natural water, 25% tailwater + 75% natural water, 50% tailwater + 50% natural water, 75% tailwater + 25% natural water, and 100% tailwater + 0% natural water, respectively). Microbial co-occurrence networks and structural equation model were used to unveil the relationship between microbial communities and their shaping factors. Results showed that distinct microbial community compositions were found in the sediments with low- (< 50%) and high- (> 50%) proportions of tailwater. Specifically, WCHB1-41 and g_4-29–1, which are involved in organic degradation-related functions, were the key genera in the high-proportion cluster. A total of 21 taxa were more abundant in the low-proportion (< 50%) cluster than that in high-proportion (> 50%). Moreover, higher modularity was observed in the low-proportion. Total phosphorus directly affected while ammonia nitrogen indirectly affected the microbial community structure. Our findings support the distinct heterogeneity of microbial communities driven by tailwater discharge in receiving water bodies, and further confirmed that high-proportion tailwater depletes sensitive microbial communities, which may be avoided through scientific management. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Hydrobiology is the property of Editorial Department of Journal of Hydrobiology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The scouring depth caused by the water jet outputs from a dam is one of the crucial parameters for design purposes. Due to the importance of the subject, several laboratory studies have been conducted to understand this subject. Nevertheless, using soft computing techniques is a new attitude for modeling and predicting the natural process parameters. Herein, the types of soft computing techniques for estimating the scouring depth of a plunge pool caused by the symmetrical crossing jets have been explored. The parameters involved in the scouring phenomenon are densimetric Froude number, tailwater depth, vertical jet angle, horizontal crossing angles, and the distance between the crossing points of two jets and the water level. The prediction results show that the Multi-Layer Perceptron (MLP) model gives the best performance among the other models tested here. The Pearson correlation coefficient, root mean square error, and normalized root mean square error for the MLP model were 0.9527, 0.9039, and 19.36% for the test phase, respectively. Furthermore, based on the sensitivity analysis, the parameters, for instance, tailwater depth and vertical jet angle have the highest and lowest effects for predicting the scouring depth of a plunge pool, respectively. HIGHLIGHTS Predicting the scour depth of a plunge pool.; Using different methods of artificial intelligence like Multi-Layer Perceptron (MLP) model, Radial Basis Function (RBF) network, Random Forest Algorithm (RFA), and Multivariate Adaptive Regression Splines (MARS) model.; Performing sensitivity analysis based on the parameters of the present study.;

Fecal coliform in the tailwater from sewage treatment needs to be deeply removed by chlorine disinfection, but ensuing disinfection by-products (DBPs) bring severe environmental and sanitary risks. Therefore, current work focused on whether bioretention cells can be used as an eco-friendly method to effectively remove fecal coliforms from tailwater remains to be further studied. Three saturated arbuscular mycorrhizal fungi (AMF)-Canna indica L. induced bioretention cells with anthracite of different sizes (0.5–1, 1–2, and 2–4 mm) and their control groups were designed to investigate tailwater fecal coliform removal efficiency. The AMF colonization of Glomus on Canna and its improvement effect, as well as the factors affecting the fecal coliform removal efficiency of the AMF-Canna bioretention cells, were discussed. The results revealed that AMF could successfully inoculate on Canna to form a stable symbiotic system and improve its plant height, root length, and underground biomass. The bioretention cells could remove fecal coliforms of 1.37 log to 3.73 log in the tailwater from sewage treatment (103.04–104.73 MPN/L). The removal efficiency of fecal coliforms of bioretention cells would be improved with AMF inoculation and the increase of the influent fecal coliform concentration, but the influence of hydraulic retention time (HRT) was relatively limited. Current findings proved that bioretention cells investigated in the present study had potential to further reduce the HRT and increase the influent pollution load on the premise of performing efficient fecal coliform removal.

Constructed wetlands (CWs) have been widely used in tailwater treatment. However, it is difficult to achieve considerable removal efficiency of nitrogen and phosphorus in tailwater solely by CWs—an efficient green wetland filler is also important. This study investigated 160 domestic sewage treatment facilities (DSTFs) in rural areas from two urban areas in Jiaxing for TP and NH3-N and found that TP and NH3-N concentrations in rural domestic sewage (RDS) in this plain river network are still high. Therefore, we selected a new synthetic filler (FA-SFe) to enhance nitrogen and phosphorus reduction, and we discuss the importance of filler in constructed wetlands. Experiments revealed the adsorption capacity of the new filler: the maximum adsorption amounts of TP and NH3-N reached 0.47 g m-2 d-1 and 0.91 g m-2 d-1, respectively. The application potential of FA-SFe was verified in actual wastewater treatment, with the removal rates of ammonia nitrogen and TP reaching 71.3% and 62.7%, respectively. This study provides a promising pathway for nitrogen and phosphorus removal from rural tailwaters.

In recent years, with the continuous growth of aquaculture output and scale, aquaculture tail water treatment has become an urgent problem to be solved. Efficient treatment of aquaculture tail water can not only effectively reduce water pollution, but also save water resources. According to different treatment mechanisms, tail water treatment methods can be divided into three categories:physical method, chemical method and biological method, and the actual treatment process is often a combination of these three methods. Based on the existing theoretical knowledge and combined with domestic and international literature, this paper provides a comprehensive description of the current research status of physical, chemical and biological method technologies and their typical equipment, and introduces and problematically analyzes the processes of several commonly used treatment processes. It provides a reference and direction for the research of aquaculture tailwater treatment technology and equipment. [ABSTRACT FROM AUTHOR]

Tailwater is becoming the main water source supplied to surface freshwater worldwide. However, few studies have compared the effect of tailwater replenishment at different time intervals on eutrophic surface freshwater. In this study, we investigated the changes of water quality, sediment, and submerged macrophytes in eutrophic water in an outdoor mesocosm in response to different tailwater replenishment time intervals [every 7 days (TW7), 14 days (TW14) and 28 days (TW28)]. An 84-day simulation experiment demonstrated that there were only significant differences in the total nitrogen (TN) concentration of the overlying water, with the lowest mean value occurring in TW28. Nevertheless, the sediment TN was lowest in TW7 with a denitrification rate of 102.9 μmol/m2/h. Tailwater replenishment also increased the nitrogen content and total biomass of Vallisneria spiralis, and TW7 had the highest total biomass of 20.19 g. Additionally, tailwater replenishment also affected plant enzyme activity, causing an increase in superoxide dismutase, peroxidase, and catalase, coupled with a decrease in malondialdehyde concentration in leaves. Overall, TW28 can be adopted as a tailwater replenishment strategy to ensure water quality, whereas TW7 can be applied without a strict water quality requirement for TN. HIGHLIGHTS Tailwater replenishment strategy with three different application time intervals was tested in eutrophic water bodies.; Replenishment with tailwater every 28 days can be adopted as a tailwater replenishment strategy to ensure water quality.; Replenishment with tailwater every 7 days can be applied without a strict water quality requirement for TN.;

Rapid filling in horizontal partially filled pipes with entrapped air may result in extreme pressure transients. This study advanced the current understanding of dynamic behavior of entrapped air above tailwater (the initial water column with a free surface in a partially filled pipe) through rigid-column modeling and sensitivity analysis of system parameters. Water and air were considered as incompressible fluid and ideal gas, respectively, and the continuity and momentum equations for water and a thermodynamic equation for air were solved by using the fourth order Runge-Kutta method. The effects of system parameters were examined in detail, including tailwater depth, entrapped air volume, driving head, pipe friction, and relative length of entrapped air and pipe. The results indicate that the presence of tailwater can mitigate the peak pressure when with identical initial volumes of entrapped air, as it can be considered to reflect a certain amount of loss of the net driving head. However, the peak pressure can increase as much as about 45% for the cases with fixed pipe length, due to the reduction in the initial entrapped air volume. The rise time for the first peak pressure was closely related to pipe friction, whereas the oscillation period (defined as the time duration between the first and second peaks) was virtually irrelevant. The applicability of the rigid-column model was discussed, and a time scale relevant indicator was proposed. When the indicator is larger than 20, the relative difference between the peak pressure estimation and experimental measurements is generally below 5%.

The transformation of riverbeds and reduction in water levels downstream of a number of hydroelectric power plants (HPP) are discussed. The influence of this process on the operating conditions and stability of hydraulic structures, conditions for dissipation of discharge energy, and headwater-tailwater connection downstream of the spillway structures is assessed. The effect of decrease in the tailwater level on the hydropower performance of HPPs is shown: increase of navigational discharges into the tailwater and reduction of the share of HPPs in peak power generation, while increasing annual power generation. The influence of an increase in the draft head of hydraulic turbines caused by a decrease in the tailwater level on their operating efficiency is considered. [ABSTRACT FROM AUTHOR]

Piano Key Weirs (PKWs) are often preferred over other spillways for the dam rehabilitation due to high discharging capacity. The present study investigates scour downstream of three cycles of PKWs with and without solid apron under both free and submerged flow conditions. The scour formations downstream of the inlet and outlet keys were investigated by varying discharges and tail water depths. Three different types of aprons were used under varied discharges and tail water depths. Falling and impinging jets emanating from inlet and outlet keys were noted as being responsible for the formation of ridge and dip, respectively. The maximum depth of scour was 40%–80% of the total weir height under different discharges. For high submergence, negligible scour development was reported. The average reduction in the scour depth with a solid apron lies in the 60%–80% range. Empirical equations were developed using a least square technique for the computation of maximum scour depth for both the conditions, that is, with and without a solid apron. Statistical and graphical analysis indicates better conformity of the proposed equation with the previous investigation. Sensitivity analysis indicates that the ratio of tailwater depth to the median size of a sediment particle (yt/d50) and the ratio of the crest length to the width of the weir (L/W) are the most sensible parameters affecting maximum scour with and without a solid apron, respectively. [ABSTRACT FROM AUTHOR]

Dam-break flood waves represent a severe threat to people and properties located in downstream regions. Although dam failure has been among the main subjects investigated in academia, little effort has been made toward investigating wave propagation under the influence of tailwater depth. This work presents three-dimensional (3D) numerical simulations of laboratory experiments of dam-breaks with tailwater performed at the Laboratory of Hydraulics of Iskenderun Technical University, Turkey. The dam-break wave was generated by the instantaneous removal of a sluice gate positioned at the center of a transversal wall forming the reservoir. Specifically, in order to understand the influence of tailwater level on wave propagation, three tests were conducted under the conditions of dry and wet downstream bottom with two different tailwater depths, respectively. The present research analyzes the propagation of the positive and negative wave originated by the dam-break, as well as the wave reflection against the channel's downstream closed boundary. Digital image processing was used to track water surface patterns, and ultrasonic sensors were positioned at five different locations along the channel in order to obtain water stage hydrographs. Laboratory measurements were compared against the numerical results obtained through FLOW-3D commercial software, solving the 3D Reynolds-Averaged Navier–Stokes (RANS) with the k-ε turbulence model for closure, and Shallow Water Equations (SWEs). The comparison achieved a reasonable agreement with both numerical models, although the RANS showed in general, as expected, a better performance. [ABSTRACT FROM AUTHOR]

Somatic growth exerts strong control on patterns in the abundance of animal populations via effects on maturation, fecundity, and survival rates of juveniles and adults. In this paper, we quantify abiotic and biotic drivers of rainbow trout growth in the Colorado River, Arizona, USA, and the resulting impact on spatial and temporal variation in abundance. Inferences are based on ~10,000 observations of individual growth rates obtained through an intensive mark–recapture effort conducted over 5 yrs (2012–2016) in a 130‐km long study segment downstream of Glen Canyon Dam. Prey availability, turbidity‐driven feeding efficiency, and intraspecific competition were the dominant drivers of rainbow trout growth. Discharge, water temperature, and solar insulation were also evaluated but had a smaller influence. Mixed‐effect models explained 79–82% of the variability in observed growth rates, with fixed covariate effects explaining 79–87% of the total variation in growth parameters across five reaches and 18 quarterly sampling intervals. Reductions in growth owing in part to a phosphorous‐driven decline in prey availability, led to a substantive loss in mass and poor fish condition. This in turn lowered survival rates and delayed maturation, which led to a rapid decline in abundance and later recruitments. Reductions in feeding efficiency, due to episodic inputs of fine sediment from tributaries, and warmer water temperatures, contributed to reduced growth in downstream reaches, which led to more severe declines in abundance. Somatic growth rates increased following the population collapse due to reduced competition, and in the absence of substantive increases in prey availability. Our study elucidates important linkages between abiotic and biotic factors, somatic growth, and vital rates, and demonstrates how variation in somatic growth influences temporal and spatial patterns in abundance. [ABSTRACT FROM AUTHOR]

Other than seasonal variation, river regulation due to hydropower generation can influence the water quality downstream. Therefore, the objectives of this study were to determine the water quality and estimate the pollutant loading of the Rajang River and its tributaries at the Pelagus area downstream of the Bakun hydroelectric Dam. The study was conducted at 11 stations three times, in July 2015 during dry season (spillway opened), in January (spillway closed) and March 2016 (spillway opened) during wet season. Results of the water quality classification show deterioration from 91% Class II in dry season to 64–82% Class III in rainy season mainly due to an increase in total suspended solids caused by soil erosion in the river basin. The pollutant loads were high particularly during wet season with TSS reaching 945,763 Mg/day, and hence, mitigation measures to reduce the pollutant loads in the river are essential. Nevertheless, two tributaries, Mela River and Kapit Hulu River where stations 4 and 5 are located, are recommended for the conservation of sensitive aquatic organisms as they are classified as Class II throughout the seasonal variation indicating good quality freshwater. The Bakun dam turbine discharge affected the downstream river water quality as shown by the low dissolved oxygen content of < 5 mg/L extending beyond 204 km downstream of the dam when the spillway was closed. Thus, raising the level of dissolved oxygen downstream of the dam during closed spillway and reducing suspended solids are recommended for the benefits of sensitive aquatic organisms. [ABSTRACT FROM AUTHOR]

Microbial pollutants, some of which can cause illnesses in humans, chronically contaminate many California water bodies. Among numerous sources, runoff from irrigated pastures has been identified as an important regulatory target for improving water quality. This study examined the potential to reduce E. coli contamination from cattle in irrigated pastures. During the 14 irrigation events examined, we found that E. coli concentrations were lowest with a combination of three treatments: filtering runoff through a natural wetland, reducing runoff rates, and letting the pasture rest from grazing at least a week prior to irrigation. Integrated pasture and tailwater management are required to significantly reduce E. coli concentrations in runoff.

Dam-break flood waves represent a severe threat to people and properties located in downstream regions. Although dam failure has been among the main subjects investigated in academia, little effort has been made toward investigating wave propagation under the influence of tailwater depth. This work presents three-dimensional (3D) numerical simulations of laboratory experiments of dam-breaks with tailwater performed at the Laboratory of Hydraulics of Iskenderun Technical University, Turkey. The dam-break wave was generated by the instantaneous removal of a sluice gate positioned at the center of a transversal wall forming the reservoir. Specifically, in order to understand the influence of tailwater level on wave propagation, three tests were conducted under the conditions of dry and wet downstream bottom with two different tailwater depths, respectively. The present research analyzes the propagation of the positive and negative wave originated by the dam-break, as well as the wave reflection against the channel’s downstream closed boundary. Digital image processing was used to track water surface patterns, and ultrasonic sensors were positioned at five different locations along the channel in order to obtain water stage hydrographs. Laboratory measurements were compared against the numerical results obtained through FLOW-3D commercial software, solving the 3D Reynolds-Averaged Navier–Stokes (RANS) with the k-ε turbulence model for closure, and Shallow Water Equations (SWEs). The comparison achieved a reasonable agreement with both numerical models, although the RANS showed in general, as expected, a better performance.

The scour process induced by plunging jets is an important topic for hydraulic engineers. In recent decades, several researchers have developed new strategies and methodologies to control the scour morphology, including different jet arrangements and structures located in the stilling basin. It has been found that multiple jets can cause less scouring than single plunging jets. Based on this evidence, this study aimed to investigate the equilibrium morphology caused by multiple non-crossing jets. A dedicated laboratory model was built and experimental tests were carried out under different combinations of jet inclination angles, by varying the tailwater level and the virtual crossing point location, which was set below the original channel bed level. It was experimentally shown that the equilibrium scour morphology depends on the jet discharge, the differences in non-crossing jet inclination angles, the downstream water level, and the distance of the virtual crossing point from the original channel bed level. In particular, the last parameter was found to be one of the most influential parameters, because of the resulting flow patterns inside the water body. Furthermore, the analysis of experimental evidence allowed for a complete and detailed classification of the scour hole typologies. Three different scour typologies were distinguished and classified. Finally, based on previous studies, two novel relationships have been proposed to predict both the maximum scour depth and length within a large range of hydraulic and geometric parameters.

To determine the sources and characteristics of suspended particulate organic matter (SPOM), the spatial distribution of carbon and nitrogen and their isotopic values (δ13C and δ15N) were measured from upstreamto downstream (i.e. site 1 to site 4) in the head waters of the Qingjiang River in central China. The mean annual SPOM δ15N and δ13C values varied between sites but exhibited a unimodal pattern. The mean annual δ15N increased from site 1 (2.5‰) to 3 (5.3‰), followed by a major decrease to 2.2‰ at site 4. Furthermore, the mean annual δ13C varied unimodally, being the most positiveat sites 1 (−21.6‰) and 4 (−22.8‰) followed by sites 2 (−24.5‰) and 3 (−26.4‰). In particular, the mean SPOM δ15N and δ13C in the tailwaters from a domestic wastewater treatment plant, which was located approximately 0.3 km upstream of site 4, were 2.2‰ and −25.6‰, respectively. The SPOM C/N values from stream water at site 4 (8.5 ± 1.5) and tailwater (6.2 ± 0.9) were similar. Collectively, the results suggested that wastewater treatment plant tailwater influenced the stable isotope values of SPOM in the stream and affected the variation trendfrom upstream to downstream.

• AMF- Canna induced bioretention cells were applied for advanced treatment from sewage treatment plant tailwater. • Bioretention cells were used as replacement of chlorine disinfection. • Inoculation with AMF can promote Canna growth. • AMF- Canna symbiotic system can improve the removal efficiency of fecal coliform. Fecal coliform in the tailwater from sewage treatment needs to be deeply removed by chlorine disinfection, but ensuing disinfection by-products (DBPs) bring severe environmental and sanitary risks. Therefore, current work focused on whether bioretention cells can be used as an eco-friendly method to effectively remove fecal coliforms from tailwater remains to be further studied. Three saturated arbuscular mycorrhizal fungi (AMF)- Canna indica L. induced bioretention cells with anthracite of different sizes (0.5–1, 1–2, and 2–4 mm) and their control groups were designed to investigate tailwater fecal coliform removal efficiency. The AMF colonization of Glomus on Canna and its improvement effect, as well as the factors affecting the fecal coliform removal efficiency of the AMF- Canna bioretention cells, were discussed. The results revealed that AMF could successfully inoculate on Canna to form a stable symbiotic system and improve its plant height, root length, and underground biomass. The bioretention cells could remove fecal coliforms of 1.37 log to 3.73 log in the tailwater from sewage treatment (103.04–104.73 MPN/L). The removal efficiency of fecal coliforms of bioretention cells would be improved with AMF inoculation and the increase of the influent fecal coliform concentration, but the influence of hydraulic retention time (HRT) was relatively limited. Current findings proved that bioretention cells investigated in the present study had potential to further reduce the HRT and increase the influent pollution load on the premise of performing efficient fecal coliform removal. [ABSTRACT FROM AUTHOR]

Total catch-and-release (C&R) is a regulatory measure implemented for maintaining the self-sustainability of stocks encountering strong fishing pressure. The River Đetinja is a tailwater with very strong fishing pressure, managed for more than a decade by C&R. That fishing regime was questioned by a new fishery manager, without the justification provided. The only available data for examining the brown trout growth were those from catches of two fly fishermen over five consecutive years. Only in one year did the average catch of one fisherman slightly surpass the legal limit for taking brown trout, and in none of years was the average size of pooled catches close to it. Survival data were similar, suggesting the stability of the brown trout stock through the period of investigation. Asymptotic length L ∞ gradually increased and coincided with the growth speed ϕ and maximal yield length L opt values. In spite of that, the high fishing pressure and low proportion of brown trout above both the legal taking limit of ≥25 cm SL and L opt values in catches strongly support the retention of C&R as a regulatory measure on the River Đetinja. [ABSTRACT FROM AUTHOR]

Constructed wetlands (CWs) have been widely used in tailwater treatment. However, it is difficult to achieve considerable removal efficiency of nitrogen and phosphorus in tailwater solely by CWs-an efficient green wetland filler is also important. This study investigated 160 domestic sewage treatment facilities (DSTFs) in rural areas from two urban areas in Jiaxing for TP and NH 3 -N and found that TP and NH 3 -N concentrations in rural domestic sewage (RDS) in this plain river network are still high. Therefore, we selected a new synthetic filler (FA-SFe) to enhance nitrogen and phosphorus reduction, and we discuss the importance of filler in constructed wetlands. Experiments revealed the adsorption capacity of the new filler: the maximum adsorption amounts of TP and NH 3 -N reached 0.47 g m -2 d -1 and 0.91 g m -2 d -1 , respectively. The application potential of FA-SFe was verified in actual wastewater treatment, with the removal rates of ammonia nitrogen and TP reaching 71.3% and 62.7%, respectively. This study provides a promising pathway for nitrogen and phosphorus removal from rural tailwaters., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Wang, Yang, Che, Huang and Yang.)

In recent years, the break of COVID-19 makes the large use of disposable products, which causes the removal of microplastics become an imperative problem. Electrocoagulation is one of the effective removal technologies, but there is hardly research concentrating on the effect of substrate in the actual water on the microplastics removal with electrocoagulation. As an important role of water bodies, dissolved organic matter (DOM) has a vital and inevitable effect on the efficiency of electrocoagulation. In this study, the effect of DOM in tailwater on microplastics during electrocoagulation is elucidated by comparing the electrocoagulation treatment results between simulated wastewater and tailwater, using parallel factor analysis (PARAFAC), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectrometer (FTIR) and zeta potential analyzer. Three kinds of microplastic particles (i.e. polypropylene, polyethylene, and polymethyl methacrylate) were added into each of the two kinds of wastewaters to form six electrocoagulation systems. Results show that DOM in tailwater promotes the production of flocs and free radicals during electrocoagulation process. Fe2+ and Fe3+ are adsorbed on the surface of DOM molecules and combined with •OH form flocs. Although DOM accelerates the production of free radicals and thus promotes the aging of microplastics, flocs with DOM as crystal nucleus can prevent toxic substances and small-sized microplastics from leaching into water again. Therefore, electrocoagulation is preferred to removal microplastics in water with high concentration of DOM. This study provides a significant reference for microplastics removal by electrocoagulation in actual water, and promote the practical application of electrocoagulation for microplastics removal in water treatment. [Display omitted] • Parts of DOM is degraded into small molecules in electrocoagulation process. • DOM accelerates the aging of microplastics in electrocoagulation process. • DOM has an impact on the trend of microplastic aggregation in suspension. • DOM promotes the production of flocs and free radicals in electrocoagulation. [ABSTRACT FROM AUTHOR]

Excessive anthropogenic nitrogen discharges have led to increasing nitrogen in aquatic systems, resulting in eutrophication problems. To address this problem, urban wetlands are used to remove nitrogen from wastewater treatment plant tailwater because of their efficient nitrogen removal capabilities. At the same time, high‑nitrogen tailwater can exert numerous impacts on the sediment denitrifier communities and denitrification of urban wetlands, and it is necessary to clarify this impact. In this research, we investigated denitrifier (nirK -, nirS - and nosZ -denitrifier) abundances and potential denitrification rate of 30 sediment samples from two urban wetland rivers in Haizhu National Wetland Park (China). One river called experimental river (ER) receives tailwater from a wastewater treatment plant, and the other called control river (CR) is unaffected by the tailwater. Moreover, we also determined the environmental variables to distinguish their relative effects on the variance of denitrifier abundances and denitrification rate in the two rivers. The results showed that the water quality was significantly different between ER and CR, while sediment property was not significant (p < 0.05). And it is unable to distinguish which has the greater denitrification rate between ER and CR. The redundancy analysis and path analysis indicated that riverine nutrient concentrations (e.g., ambient carbon and nitrogen) and physicochemical parameters (e.g., ambient temperature, dissolved oxygen and pH) were important determinants for denitrifier abundances and denitrification in ER and in CR, respectively. Furthermore, denitrifier abundances had an insignificant impact on denitrification in ER, but a considerable impact on denitrification in CR. The findings of this research can help to further understand how the tailwater affects sediment denitrifier communities and denitrification in urban wetland rivers, and to make better use of urban wetlands as a natural purification method. [Display omitted] • Tailwater significantly affected water quality but not sediment properties. • Nutrient concentrations were determinants for N removal in the river with tailwater. • Physicochemical parameters controlled the N removal in the river without tailwater. [ABSTRACT FROM AUTHOR]