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): Yunlong Luo, Pierre Le-Clech, Rita K. Henderson Membrane photobioreactor (MPBR) technology is an emerging algae-based wastewater treatment system. Given the limitations due to the general use of conventional analytical approaches in previous research, this study aims to provide a more comprehensive assessment of MPBR performance through advanced characterisation techniques. New performance parameters are also proposed, encompassing five important aspects of MPBR system efficiency (i.e. biomass concentration, composition, production, nutrient uptake and harvesting potential). Under initial standard operating conditions, performance parameters, such as cell count/MLSS ratio, cell viability, proportion of bacteria and biomass yield coefficient, were found to offer new insights into the operation of MPBR. These parameters were then used, for the first time, to systematically investigate MPBRs operated under different hydraulic retention times (HRTs) and solids retention times (SRTs). Applying shorter HRT and SRT was observed to increase cell viability and productivity (up to 0.25 × 10 7  cells/mL·d), as anticipated due to the higher nutrient loading. It was noted that the faster growing algal cells featured lower requirement for nutrients. On the other hand, extending HRT and SRT resulted in a more heterogeneous culture (lower cell count/MLSS ratio and higher proportion of bacteria), achieving a higher degree of autoflocculation and greater NO 3 -N and PO 4 -P removals of up to 79% and 78% respectively. The results demonstrate the trade-off between applying different HRTs and SRTs and the importance of fully characterising system performance to critically assess the advantages and limitations of chosen operating conditions. Graphical abstract

Description: Publication date: 1 July 2018 Source: Water Research, Volume 138 Author(s): Xiangrui Wang, Wenhong Fan, Zhaomin Dong, Dingyuan Liang, Tingting Zhou It is now widely accepted that coating on the nano-surface would critically dictate the uptake and cytotoxicity of engineering nanomaterials. However, the influence of natural organic matter (NOM) on the surface is quite limited to humic substances, while the diversity of NOM is neglected. In the present study, we tried to investigate the change of surface in the coexistence of bovine serum albumin (BSA) and humic acid (HA). The isothermal titration calorimetric measurements show that HA can combine with BSA in both freshwater or seawater, however, the patterns are different. In freshwater, HA lowered the adsorption of BSA on PVP-capped AgNPs through complexation with BSA, which prevented the contact of sulfur in BSA with PVP-AgNPs. Then in seawater, BSA retained its sulfur availability to bind with PVP-AgNPs. Furthermore, the toxicity of PVP-AgNPs incubated in the BSA/HA solution was evaluated by measuring the level of reactive oxygen species generated by Escherichia coli . The results indicated that, in seawater, the adsorbed BSA promoted the toxicity of PVP-AgNPs in the presence of Ca 2+ and Mg 2+ , but the presence of HA limited this effect. Graphical abstract

Description: Publication date: 1 July 2018 Source: Water Research, Volume 138 Author(s): Rezvan Hatami 1- A major challenge when assessing the impacts of human activities on the globe's natural resources is to account for the impacts of land use versus natural spatiotemporal variation in system dynamics. Current freshwater assessments are unable to resolve spatiotemporal confounding through study designs or statistical analyses. Observational studies typically fail to consider the period-by-location interaction in the absence of an impact. 2- Here, I address the problem of spatiotemporal confounding using causal modelling based on spatiotemporal data to infer causal effects of wastewater on biotic ecosystems. A combination of statistical analysis and causation theory was used to address confounding bias. Benthic macroinvertebrate and environmental variable data were collected from locations upstream and downstream of a wastewater treatment plant discharge point in south-eastern Australia over 1.5 years. The composite hypotheses based on the theoretical relationships among these variables were summarised in a causal diagram. Model building and testing was conducted using Structural Equation Modelling (SEM). Distance-based redundancy analysis (dbRDA) was used for model building and hypothesis testing. 3- The results indicated that the causal effects of effluent on macroinvertebrate communities could be inferred using causal modelling. The macroinvertebrate communities responded to water quality degradation with a clear shift in community composition after the discharge point and this change varied seasonally. Chlorophyll a , total organic carbon, zinc, conductivity, temperature, and its interaction with conductivity, were important determinants of the macroinvertebrate community composition. Causal models also explained the spatiotemporal variations in environmental variables. The consistency of data with the structure of the causal diagram was confirmed with global Fisher's C-test. 4- Causal modelling has been shown to be a useful tool in environmental impact studies. In this study, the usefulness of causal modelling was attributed to its proficiency in combining all of the elements necessary for an efficient risk assessment through dealing with spatial and temporal confounding, facilitating communication between scientists and resource managers, and supporting management decision making. 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

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Wei Wang, Yaobin Lu, Haiping Luo, Guangli Liu, Renduo Zhang, Song Jin High electrical energy is required for the electro-Fenton process to remove pharmaceuticals and personal care products (PPCPs) in wastewater. The aim of this study was to develop a novel and more cost-effective process, specifically a microbial electro-Fenton cell (MeFC), for treating PPCPs in wastewater. Acetylene black was selected as the catalyst for H 2 O 2 electrogeneration and Fe-Mn binary oxide for hydroxyl radical production. In addition to lowering energy needs, the MeFC produced a maximum power density of 112 ± 11 mW/m 2 with 1 g/L acetate as a representative substrate and 10 mg/L carbamazepine (CBZ) as a typical PPCP. Comparing with electro-Fenton process, the CBZ removal in the MeFC was 38% higher within 24 h operation (90% vs. 62%). Furthermore, the CBZ removal rate in the MeFC was 10–100 times faster than that in other biological treatment processes. Such enhanced degradation of CBZ in the MeFC was attributed to the synergistic reactions between radical oxidation of CBZ and biodegradation of degradative intermediates. The MeFC provides a promising method to remove PPCPs from wastewater coupling with efficient removal of other biodegradable organics. Graphical abstract

Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Changyin Zhu, Fengxiao Zhu, Dionysios D. Dionysiou, Dongmei Zhou, Guodong Fang, Juan Gao Alcohols such as ethanol (EtOH) and tert- butanol (TBA) are frequently used as quenching agents to identify the primary radical species in the persulfate (PS)-based oxidation processes. However, the contribution of alcohol radicals (ARs) to contaminant degradation in this process has rarely been assessed. In this study, trichloroacetic acid (TCA), phenol, and carbon tetrachloride were selected as probes to test the role of ARs in the thermally activated PS system. It was found that the degradation rates of these compounds were largely depended on their reactivities with ARs and the concentration of dissolved oxygen in the reaction system. In the PS/alcohol system, TCA was degraded efficiently under anaerobic conditions, while it was hardly degraded in the presence of oxygen. The results of electron paramagnetic resonance, reducing radical quenching studies, and the analysis of PS consumption suggested that ARs were the dominant reactive species contributing to TCA degradation in the PS/EtOH system under anaerobic conditions. Further studies indicated that ARs could significantly degrade CCl 4 through dechlorination but not phenol. CCl 4 was also degraded efficiently by ARs when oxygen in the reaction solution was completely consumed by ARs. This study highlights the important role of alcohol radicals in the degradation of contaminants during quenching studies in PS-activated processes. 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): Mashor Housh, Ziv Ohar Modern Water Distribution Systems (WDSs) are often controlled by Supervisory Control and Data Acquisition (SCADA) systems and Programmable Logic Controllers (PLCs) which manage their operation and maintain a reliable water supply. As such, and with the cyber layer becoming a central component of WDS operations, these systems are at a greater risk of being subjected to cyberattacks. This paper offers a model-based methodology based on a detailed hydraulic understanding of WDSs combined with an anomaly detection algorithm for the identification of complex cyberattacks that cannot be fully identified by hydraulically based rules alone. The results show that the proposed algorithm is capable of achieving the best-known performance when tested on the data published in the BATtle of the Attack Detection ALgorithms (BATADAL) competition ( http://www.batadal.net ).