Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Yan Gao, Wen Zhang, Bin Gao, Wen Jia, Aijun Miao, Lin Xiao, Liuyan Yang Electrolysis combined with biochar (BC) was used in a constructed wetland to intensify nitrogen (N) and phosphorus (P) removal from wastewater simultaneously. A pilot study was conducted using an electrolysis-integrated, BC-amended, horizontal, subsurface-flow, constructed wetland (E-BHFCW). The research results showed that both electrolysis and BC substrate played important roles in the intensified, constructed wetland. The electrolysis combined BC substrate greatly enhanced the removal rates of nitrate (49.54%) and P (74.25%) when the E-BHFCW operated under the lower current density of 0.02 mA/cm 2 and an electrolysis time of 24 h. Improved N removal was accomplished with the electrochemical denitrification of iron cathodes; the autotrophic denitrification bacteria appeared to remove nitrate which was adsorbed on the BC substrate because hydrogen gas was produced by cathodes in the E-BHFCW. Less nitrate was taken directly by wetland plants and microbes. The in-situ formation of ferric ions from a sacrificial iron anode, causing P chemical sedimentation and physical adsorption, improved P removal. BC, modified by iron ions from an iron anode to adsorb the nitrate and P, was a good material to improve effluent water quality. It can also serve as a favorable microbial carrier to bio-transform nitrate to N gas. This is because there were abundant and diverse bacterial communities in the biofilm on the BC substrate in the E-BHFCW. Thus, electrolysis integrated with BC in a constructed wetland is a novel, feasible and effective technique for enhancing wastewater N and P removal. Graphical abstract

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Wei Ouyang, Wanxin Yang, Mats Tysklind, Yixue Xu, Chunye Lin, Xiang Gao, Zengchao Hao The formation and transportation processes of non-point source (NPS) pollution varied among the studied watersheds in the Northeastern China, so we hypothesized that the driving force behind NPS pollution followed the spatial scale effect. With a watershed outlet sedimentary flux analysis and a distributed NPS pollution loading model, we investigated the temporal dynamics of NPS and the differences in driving forces. Sediment core samples were collected from two adjacent watersheds, the smaller Abujiao watershed and the larger Naoli watershed. The natural climatic conditions, long-term variations in the distribution of land use, soil properties and tillage practices were the same in the two watersheds. The vertical distributions of total nitrogen, total phosphorus, Zn and As at 1-cm intervals in the section showed clear differences between the watersheds. There were higher concentrations of total nitrogen and total phosphorus in the larger watershed, but the heavy metals were more concentrated in the smaller watershed. Lead-210 ( 210 Pb) analyses and the constant rate of supply model provided a dated sedimentary flux, which was correlated with the corresponding yearly loading of NPS total nitrogen and total phosphorus in the two watersheds. The total phosphorus showed a stable relationship in both watersheds with an R 2 value that ranged from 0.503 to 0.682. A rose figure comparison also demonstrated that the pollutant flux in the sediment was very different in the two watersheds, which had similar territorial conditions and different hydrological patterns. Redundancy analysis further indicated that expanding paddy areas had a large impact on the sedimentary flux of nitrogen and phosphorus in the smaller watershed, but precipitation had a direct impact on NPS loading in the larger watershed. We concluded that the spatial scale effect affected the NPS pollution via the transport processes in the waterway, which was mainly influenced by branch length and drainage density.

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Li Ma, Scott R. Yates Laboratory degradation tests with two model estrogen conjugates, 17ß-estradiol-3-glucuronide (E2-3G) and 17ß-estradiol-3-sulphate (E2-3S), using river water and sediment as inoculum under aerobic conditions were investigated. Throughout the 14-day incubation, degradation of E2-3G in river water, at environmentally-relevant level (25 ng/L), obeyed first-order kinetics with the formation of 17-ß estradiol and estrone; in contrast, E2-3S was slowly converted to estrone-3-sulphate stoichiometrically. Degradation of the two conjugates across the spiking concentrations (0.01–1 μg/g) was much faster in sediment than in river water where 25 ng/L of conjugate standards were spiked, possibly due to relatively high population densities of microorganisms in sediment. De-conjugation of the thio-ester bond at C-3 position and oxidation at C-17 position were the predominant degradation mechanisms for E2-3G and E2-3S, respectively, with negligible presence of metabolites estrone-3-glucuronide for E2-3G and 17ß-estradiol for E2-3S. In addition, delta-9(11)-dehydroestrone and 6-ketoestrone were determined as new metabolites of the two conjugates. Also, a lactone compound, hydroxylated estrone and a few sulfate conjugates were tentatively identified. With the observation of new metabolites, biodegradation pathways of E2-3G and E2-3S were proposed. The formation of new metabolites may pose unknown risks to aquatic biota. Graphical abstract

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): F. Sánchez, H. Rey, A. Viedma, F. Nicolás-Pérez, A.S. Kaiser, M. Martínez Due to the aeration system, biological reactors are the most energy-consuming facilities of convectional WWTPs. Many biological reactors work under intermittent aeration regime; the optimization of the aeration process (air diffuser layout, air flow rate per diffuser, aeration length …) is necessary to ensure an efficient performance; satisfying the effluent requirements with the minimum energy consumption. This work develops a CFD modelling of an activated sludge reactor (ASR) which works under intermittent aeration regime. The model considers the fluid dynamic and biological processes within the ASR. The biological simulation, which is transient, takes into account the intermittent aeration regime. The CFD modelling is employed for the selection of the aeration system of an ASR. Two different aeration configurations are simulated. The model evaluates the aeration power consumption necessary to satisfy the effluent requirements. An improvement of 2.8% in terms of energy consumption is achieved by modifying the air diffuser layout. An analysis of the influence of the air flow rate per diffuser on the ASR performance is carried out. The results show a reduction of 14.5% in the energy consumption of the aeration system when the air flow rate per diffuser is reduced. The model provides an insight into the aeration inefficiencies produced within ASRs. Graphical abstract

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Robyn S. Wilson, Derek A. Schlea, Chelsie M.W. Boles, Todd M. Redder To address the management of eutrophication in aquatic systems, the behavioral mechanisms that drive change at the individual level must be considered when designing policy interventions. This analysis identifies the beliefs that are critical to behavioral change, and explores the likelihood that farmers will adopt two management practices believed to be critical to reducing nutrient loading to recommended levels in Lake Erie. We find that there is potential for farmers to adopt key infield practices needed to reduce nutrient inputs. And further, that increased adoption of such practices is possible by increasing the perceived efficacy of the majority of farmers who are motivated to take action. Integrating these findings with physical models of nutrient movement indicates that adoption of these practices in combination with edge of field practices can attain phosphorus reduction targets for the lake. Future research should focus on measuring the effectiveness of education and outreach programs aimed at engaging farmers and promoting adoption of recommended practices. Such programs may only be effective if they are successfully building farmer confidence in their ability to implement the practices (i.e., perceived self efficacy) and increasing farmer's belief in the effectiveness of the practices at reducing nutrient loss and improving local water quality (i.e., perceived response efficacy). Graphical abstract

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Wai Hing Wong, John J. Dudula, Therese Beaudoin, Kimberly Groff, Warren Kimball, Juliet Swigor Over the last century, nutrient concentrations in streams, rivers, lakes and ponds have increased substantially in the United States. Elevated phosphorus levels are a concern due to their ability to cause changes in freshwater ecosystems that are detrimental to humans and wildlife. In the present study, long-term trends in total phosphorus (TP) concentrations from 20 rivers in central Massachusetts from 1999 to 2013 were investigated. Kendall's correlation coefficients were used to demonstrate that 18 of the 20 rivers had significant reductions in TP concentrations (P 〈 0.05). A similar trend was found when flow-adjusted TP concentrations were analyzed. At the beginning of monitoring activities, the average TP concentration in 9 of the 20 rivers was greater than 0.05 mg/L and 6 of these 9 rivers contained TP concentrations greater than 0.1 mg/L; about fifteen years later, only 3 rivers contained TP greater than 0.05 mg/L and none had concentrations> 0.1 mg/L. TP decreases were greater in rivers with more anthropogenic inputs. Principal component analysis (PCA) revealed that the decline of TP in these Massachusetts streams is likely the result of advancements in wastewater treatment and implementation of effective non-point source management practices. Graphical abstract

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Qi Zhang, Zhigang Yu, Liandong Zhu, Ting Ye, Jiaolan Zuo, Xuemei Li, Bo Xiao, Shiping Jin A win-win strategy by the integration of wastewater treatment with value-added products production through a vertical-algal-biofilm enhanced raceway was investigated in the present study. Raceway pond was enhanced by vertically setting the biofilm in the system with a certain interval distance that could be adjusted for different light conditions and wastewater types. Two types of synthetic wastewater were treated with suitability-proven materials as biofilm carriers under four operation distances. Composition of the harvested algal biomass was analyzed. Coral velvet with 5–8 mm length villus was the optimal carrier, since it was durable and with high biomass productivity (6.95–8.11 g m −2 ·day −1 ). Nutrients in the wastewaters were efficiently removed with the COD, TN and TP reduction of over 86.61%, 73.68% and 89.85%, respectively. Wastewater with the low nutrients concentration experienced lower biomass and lipid productivity but larger biodiesel productivity and higher nutrient removal efficiency. In addition, as the operation distance increased, wastewater treatment efficiency was first increased but then decreased, while algal biomass footprint production was decreased. Differences in nutrients removal efficiencies were mainly due to the distance difference, which caused different biofilm culture surface areas and light regimes. The optimal operation distance as a function of the efficient nutrient removal and biodiesel production in this study was 6 cm. Graphical abstract

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): To-Hung Tsui, George A. Ekama, Guang-Hao Chen Knowledge of leveraging biomass characteristics is essential for achieving a microbial community with a desired structure to optimize anaerobic bioreactor performance. This study investigates the successive granule transformations in a high-rate anaerobic system with intermittent gas sparging and sequential increases in organic loading rates (OLRs), by establishing the correlations between the granule microstructures and reactor operating parameters. Over the course of a 196-day lab-scale trial, the granules were visualized in various stages using scanning electron microscopy, and digital image processing was applied for further quantifying their surface properties. Correlation analyses revealed that irregularities of the granule microstructures (surface properties, specific surface area and pore volume) emerged at stage 4 when the OLR was 13.31 kg COD/m 3 ·day and in stage 5 in the absence of gas sparging. The loading ratio (substrate surface loading to upward velocity) was identified to be the main parameter controlling the granule transformations, and the surface structures were classified into three categories for further interpretation. Confocal laser scanning microscopy analyses showed that the granule core started to hollow out from stage 4. It is also found that a rough granule surface helped accelerate the growth of the granular diameter under gas sparging. Overall, this study not only establish quantitative correlations between the granules microstructures and reactor operating parameters, but also shed light on the use of intermittent gas sparging to control the surface properties of anaerobic granules in high-rate anaerobic bioreactors. Graphical abstract

Description: Publication date: 1 July 2018 Source: Water Research, Volume 138 Author(s): Min Cheng, Guangming Zeng, Danlian Huang, Cui Lai, Yang Liu, Chen Zhang, Jia Wan, Liang Hu, Chengyun Zhou, Weiping Xiong The presence of antibiotics in aquatic environments has attracted global concern. Fenton process is an attractive yet challenging method for antibiotics degradation, especially when such a reaction can be conducted at neutral pH values. In this study, a novel composite Fe/Co catalyst was synthesized via the modification of steel converter slag (SCS) by salicylic acid–methanol (SAM) and cobalt nitrate (Co(NO 3 ) 2 ). The catalysts were characterized by N 2 -Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results indicated that the Co-SAM-SCS/H 2 O 2 Fenton-like system was very effective for sulfamethazine (SMZ) degradation at a wide pH range. At initial pH of 7.0, the degradation rate of SMZ in Co-SAM-SCS/H 2 O 2 system was 2.48, 3.20, 6.18, and 16.21 times of that in Fe-SAM-SCS/H 2 O 2 , SAM-SCS/H 2 O 2 , Co(NO 3 ) 2 /H 2 O 2 and SCS/H 2 O 2 system, respectively. The preliminary analysis suggested that high surface area of Co-SAM-SCS sample and synergistic effect between introduced Co and SAM-SCS are responsible for the efficient catalytic activity. During the degradation, three main intermediates were identified by high performance liquid chromatography–mass spectrometry (HPLC–MS) analysis. Based on this, a possible degradation pathway was proposed. The SEM images, XRD patterns and XPS spectra before and after the reactions demonstrate that the crystal and chemical structure of Co-SAM-SCS after five cycles are almost unchanged. Besides, the Co-SAM-SCS presented low iron and cobalt leaching (0.17 mg/L and 2.36 mg/L, respectively). The studied Fenton-like process also showed high degradation of SMZ in river water and municipal wastewater. The progress will bring valuable insights to develop high-performance heterogeneous Fenton-like catalysts for environmental remediation. Graphical abstract

Description: Publication date: 1 July 2018 Source: Water Research, Volume 138 Author(s): Jianfa Gao, Jiaying Li, Guangming Jiang, Zhiguo Yuan, Geoff Eaglesham, Adrian Covaci, Jochen F. Mueller, Phong K. Thai Since alcohol and tobacco consumption are among the leading causes of population health harm, it is very important to understand the consumption behaviour to develop effective harm reduction strategies. Wastewater-based epidemiology (WBE) is a potential tool for estimating their consumption, but there are several uncertainties that need to be determined, including the stability of biomarkers in the sewer. Utilizing a real rising main sewer, this study investigated the stability of alcohol and tobacco consumption biomarkers. Rhodamine and acesulfame were used as flow tracer and benchmarker to understand the transportation of wastewater in the sewer with a hydraulic retention time between 2.7 and 5.0 h. Ethyl sulphate (EtS) and ethyl glucuronide (EtG), two biomarkers of alcohol consumption, were found to have different in-sewer stability, with EtS much more stable than EtG. The degradation rate of EtS is approximately 8% per hour, while EtG has a half-life of 1.9 h. Formation of nicotine, cotinine and trans -3′-hydroxycotinine, three biomarkers for tobacco consumption, was observed during the experiment, probably due to deconjugation of their glucuronide chemicals. The deconjugation process has prevented the determination of actual stability of the three chemicals. However, it is suggested that cotinine is relatively stable, while nicotine and trans -3′-hydroxycotinine degrade to a certain degree in the sewer system. According to our findings, the in-sewer degradation is more important during the interpretation of alcohol consumption estimation than for tobacco consumption estimation. Graphical abstract