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 July 2018 Source: Water Research, Volume 138 Author(s): Weikun Yao, Syed Waqi Ur Rehman, Huijiao Wang, Hongwei Yang, Gang Yu, Yujue Wang The electro-peroxone (E-peroxone) process is an emerging ozone-based advanced oxidation process (AOP) that has shown large potential for micropollutant abatement in water treatment. To evaluate its performance under more realistic conditions of water treatment, a continuous-flow pilot E-peroxone system was developed and compared with conventional ozonation and a UV/O 3 process for micropollutant abatements in various water matrices (groundwater, surface water, and secondary wastewater effluent) in this study. With a specific ozone dose of 1.5 mg O 3 /mg DOC, micropollutants that have high and moderate reactivity with ozone (O 3 ) (diclofenac, naproxen, gemfibrozil, and bezafibrate) could be sufficiently abated (>90% abatement) in the various waters by all three processes. However, ozone-resistant micropollutants (ibuprofen, clofibric acid, and chloramphenicol) were abated only by ∼32–68%, 68–91%, and 73–90% during conventional ozonation of the selected groundwater, surface water, and secondary wastewater effluent, respectively. By electro-generating H 2 O 2 or applying UV irradiation to enhance O 3 transformation to •OH during ozonation, the E-peroxone and UV/O 3 processes similarly enhanced the abatement efficiencies of ozone-resistant micropollutants by ∼15–43%, ∼5–15%, and ∼5–10% in the groundwater, surface water, and secondary wastewater effluent, respectively. In addition, the E-peroxone and UV/O 3 processes significantly reduced bromate formation during the treatment of the three waters compared to conventional ozonation. Due to its higher efficiency, the E-peroxone process reduced ∼10–53% of the energy consumption required to abate the concentration of chloramphenicol (the most ozone-resistant micropollutant spiked in the waters) by 1 order of magnitude in the three waters compared to conventional ozonation. In contrast, the UV/O 3 process consumed approximately 4–10 times higher energy than conventional ozonation. This pilot-scale study demonstrates that the E-peroxone process can provide a feasible, effective, and energy-efficient alternative for micropollutant abatement and bromate control in water and wastewater treatment. Graphical abstract

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Stephan Wagner, Thorsten Hüffer, Philipp Klöckner, Maren Wehrhahn, Thilo Hofmann, Thorsten Reemtsma Tire wear particles (TWP), generated from tire material during use on roads have gained increasing attention as part of organic particulate contaminants, such as microplastic, in aquatic environments. The available information on properties and generation of TWP, analytical techniques to determine TWP, emissions, occurrence and behavior and ecotoxicological effects of TWP are reviewed with a focus on surface water as a potential receptor. TWP emissions are traffic related and contribute 5–30% to non-exhaust emissions from traffic. The mass of TWP generated is estimated at 1,327,000 t/a for the European Union, 1,120,000 t/a for the United States and 133,000 t/a for Germany. For Germany, this is equivalent to four times the amount of pesticides used. The mass of TWP ultimately entering the aquatic environment strongly depends on the extent of collection and treatment of road runoff, which is highly variable. For the German highways it is estimated that up to 11,000 t/a of TWP reach surface waters. Data on TWP concentrations in the environment, including surface waters are fragmentary, which is also due to the lack of suitable analytical methods for their determination. Information on TWP properties such as density and size distribution are missing; this hampers assessing the fate of TWP in the aquatic environment. Effects in the aquatic environment may stem from TWP itself or from compounds released from TWP. It is concluded that reliable knowledge on transport mechanism to surface waters, concentrations in surface waters and sediments, effects of aging, environmental half-lives of TWP as well as effects on aquatic organisms are missing. These aspects need to be addressed to allow for the assessment of risk of TWP in an aquatic environment. Graphical abstract

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Frederic D.L. Leusch, Peta A. Neale, Charlotte Arnal, Natalie H. Aneck-Hahn, Patrick Balaguer, Auguste Bruchet, Beate I. Escher, Mar Esperanza, Marina Grimaldi, Gaela Leroy, Marco Scheurer, Rita Schlichting, Merijn Schriks, Armelle Hebert The aquatic environment can contain numerous micropollutants and there are concerns about endocrine activity in environmental waters and the potential impacts on human and ecosystem health. In this study a complementary chemical analysis and in vitro bioassay approach was applied to evaluate endocrine activity in treated wastewater, surface water and drinking water samples from six countries (Germany, Australia, France, South Africa, the Netherlands and Spain). The bioassay test battery included assays indicative of seven endocrine pathways, while 58 different chemicals, including pesticides, pharmaceuticals and industrial compounds, were analysed by targeted chemical analysis. Endocrine activity was below the limit of quantification for most water samples, with only two of six treated wastewater samples and two of six surface water samples exhibiting estrogenic, glucocorticoid, progestagenic and/or anti-mineralocorticoid activity above the limit of quantification. Based on available effect-based trigger values (EBT) for estrogenic and glucocorticoid activity, some of the wastewater and surface water samples were found to exceed the EBT, suggesting these environmental waters may pose a potential risk to ecosystem health. In contrast, the lack of bioassay activity and low detected chemical concentrations in the drinking water samples do not suggest a risk to human endocrine health, with all samples below the relevant EBTs. Graphical abstract

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Fen Wang, Charles S. Wong, Da Chen, Xingwen Lu, Fei Wang, Eddy Y. Zeng Occurrence of microplastics (MPs) in the environment has attracted great attention as it has become a global concern. This review aims to systematically demonstrate the role of marine microplastic as a novel medium for environmental partitioning of chemicals in the ocean, which can cause toxic effects in the ecological environment. This review assimilated and analyzed available data published between 1972 and 2017 on the interaction between MPs and selected chemicals. Firstly, the review analyzes the occurrence of chemicals in MPs and outlines their distribution patterns. Then possible mechanisms of the interaction between MPs and organic chemicals and potential controlling factors were critically studied. Finally, the hazards of MPs and affiliated organic chemicals to marine organisms were shortly summarized. 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): 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): Elena Villar-Navarro, Rosa M. Baena-Nogueras, Maria Paniw, José A. Perales, Pablo A. Lara-Martín Microalgae biotechnology is a promising tool for many applications, including the elimination of nutrients and other contaminants from wastewater. In this work, we measured the removal efficiency of two wastewater treatment processes: an activated-sludge based conventional process and another based on microalgae biotechnology using high-rate algae ponds (HRAPs). The latter was tested using two different configurations. In the first one, HRAPs were placed after an UASB reactor and used as a tertiary treatment to remove nutrients. In the second, the UASB reactor was disconnected so the HRAPs were directly fed with pretreated wastewater. Additional treatment was performed using dissolved air flotation (DAF). The performances of both configurations (UASB-HRAP and HRAP-DAF) were compared to that of the conventional line including primary and secondary biological treatments and operating in parallel within the same wastewater treatment plant (WWTP). Sixty-four out of 81 target PhACs were detected in the influent of the WWTP, at an average concentration of 223 μg L −1 , whereas 55 and 54 were measured in the conventional (14 μg L −1 ) and non-conventional (17 μg L −1 ) effluents. Average removal efficiencies were similar (94 vs. 92%) for both treatment lines when comparing total PhACs concentrations. The compositional patterns of the resulting effluents, however, were not, suggesting the occurrence of differential removal mechanisms depending on the chemicals and wastewater treatments considered. Highly consumed compounds such as ibuprofen and acetaminophen were predominant in the non-conventional effluent (>1 μg L −1 ), denoting lower removal than in the conventional line. On the other hand, elimination of diclofenac and some specific antibiotics and diuretics (e.g., hydrochlorothiazide) was between 15 and 50% higher using HRAPs. Overall, the efficiency of the microalgae technology removing PhACs was found to be comparable to that used in conventional WWTPs. This, combined with a higher efficiency removing nutrients, shows the potential of HRAP technology for wastewater treatment as an alternative (or addition as tertiary treatment) to more conventional approaches based on activated sludge. Graphical abstract

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Kam W. Tang, Sabine Flury, Dominic Vachon, César Ordóñez, Daniel F. McGinnis Chaoborus spp. (phantom midge) are prevalent in eutrophic inland waters. In Lake Soppen, Switzerland, C. flavicans larvae diurnally migrate between the methane-rich, oxygen-depleted hypolimnion and sediments, and the methane-poor, oxygen-rich epilimnion. Using a combination of experiments and system modelling, this study demonstrated that the larvae's burrowing activities in and out of the sediment perturbed the sediment and re-introduced sequestered phosphorus into the overlying water at a rate of 0.022 μg P ind −1 d −1 , thereby exacerbating internal nutrient loading in the water column. Fluxes of sediment methane and other reduced solutes enhanced by the larval bioturbation would consume oxygen and sustain the hypoxic/anoxic condition below the thermocline. In addition to increasing diffusive fluxes, migrating larvae also directly transported methane in their gas vesicles from the deep water and release it in the surface water at a rate of 0.99 nmol CH 4 ind −1 d −1 , potentially contributing to methane emission to air. As nutrient pollution and climate warming persist or worsen in the coming decades, proliferation of Chaoborus could intensify this positive feedback loop and delay lake recovery. Graphical abstract