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): 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): 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): David B. Miklos, Christian Remy, Martin Jekel, Karl G. Linden, Jörg E. Drewes, Uwe Hübner This study provides an overview of established processes as well as recent progress in emerging technologies for advanced oxidation processes (AOPs). In addition to a discussion of major reaction mechanisms and formation of by-products, data on energy efficiency were collected in an extensive analysis of studies reported in the peer-reviewed literature enabling a critical comparison of various established and emerging AOPs based on electrical energy per order (E EO ) values. Despite strong variations within reviewed E EO values, significant differences could be observed between three groups of AOPs: (1) O 3 (often considered as AOP-like process), O 3 /H 2 O 2 , O 3 /UV, UV/H 2 O 2 , UV/persulfate, UV/chlorine, and electron beam represent median E EO values of 〈1 kWh/m 3 , while median energy consumption by (2) photo-Fenton, plasma, and electrolytic AOPs were significantly higher (E EO values in the range of 1–100 kWh/m 3 ). (3) UV-based photocatalysis, ultrasound, and microwave-based AOPs are characterized by median values of >100 kWh/m 3 and were therefore considered as not (yet) energy efficient AOPs. Specific evaluation of 147 data points for the UV/H 2 O 2 process revealed strong effects of operational conditions on reported E EO values. Besides water type and quality, a major influence was observed for process capacity (lab-vs. pilot-vs. full-scale applications) and, in case of UV-based processes, of the lamp type. However, due to the contribution of other factors, correlation of E EO values with specific water quality parameters such as UV absorbance and dissolved organic carbon were not substantial. Also, correlations between E EO and compound reactivity with OH-radicals were not significant (photolytically active compounds were not considered). Based on these findings, recommendations regarding the use of the E EO concept, including the upscaling of laboratory results, were derived. Graphical abstract

Description: Publication date: 1 July 2018 Source: Water Research, Volume 138 Author(s): Dries Seuntjens, Mofei Han, Frederiek-Maarten Kerckhof, Nico Boon, Ahmed Al-Omari, Imre Takacs, Francis Meerburg, Chaïm De Mulder, Bernhard Wett, Charles Bott, Sudhir Murthy, Jose Maria Carvajal Arroyo, Haydée De Clippeleir, Siegfried E. Vlaeminck Even though nitrification/denitrification is a robust technology to remove nitrogen from sewage, economic incentives drive its future replacement by shortcut nitrogen removal processes. The latter necessitates high potential activity ratios of ammonia oxidizing to nitrite oxidizing bacteria (rAOB/rNOB). The goal of this study was to identify which wastewater and process parameters can govern this in reality. Two sewage treatment plants (STP) were chosen based on their inverse rAOB/rNOB values (at 20 °C): 0.6 for Blue Plains (BP, Washington DC, US) and 1.6 for Nieuwveer (NV, Breda, NL). Disproportional and dissimilar relationships between AOB or NOB relative abundances and respective activities pointed towards differences in community and growth/activity limiting parameters. The AOB communities showed to be particularly different. Temperature had no discriminatory effect on the nitrifiers' activities, with similar Arrhenius temperature dependences (Θ AOB  = 1.10, Θ NOB  = 1.06–1.07). To uncouple the temperature effect from potential limitations like inorganic carbon, phosphorus and nitrogen, an add-on mechanistic methodology based on kinetic modelling was developed. Results suggest that BP's AOB activity was limited by the concentration of inorganic carbon (not by residual N and P), while NOB experienced less limitation from this. For NV, the sludge-specific nitrogen loading rate seemed to be the most prevalent factor limiting AOB and NOB activities. Altogether, this study shows that bottom-up mechanistic modelling can identify parameters that influence the nitrification performance. Increasing inorganic carbon in BP could invert its rAOB/rNOB value, facilitating its transition to shortcut nitrogen removal. Graphical abstract

Description: Publication date: 1 July 2018 Source: Water Research, Volume 138 Author(s): Taku Matsushita, Ayako Morimoto, Taisuke Kuriyama, Eisuke Matsumoto, Yoshihiko Matsui, Nobutaka Shirasaki, Takashi Kondo, Hirokazu Takanashi, Takashi Kameya Removal efficiencies of 28 pesticide transformation products (TPs) and 15 parent pesticides during steps in drinking water treatment (coagulation–sedimentation, activated carbon adsorption, and ozonation) were estimated via laboratory-scale batch experiments, and the mechanisms underlying the removal at each step were elucidated via regression analyses. The removal via powdered activated carbon (PAC) treatment was correlated positively with the log K ow at pH 7. The adjusted coefficient of determination ( r 2 ) increased when the energy level of the highest occupied molecular orbital (HOMO) was added as an explanatory variable, the suggestion being that adsorption onto PAC particles was largely governed by hydrophobic interactions. The residual error could be partly explained by π-π electron donor–acceptor interactions between the graphene surface of the PAC particles and the adsorbates. The removal via ozonation correlated positively with the energy level of the HOMO, probably because compounds with relatively high energy level HOMOs could more easily transfer an electron to the lowest unoccupied molecular orbital of ozone. Overall, the TPs tended to be more difficult to remove via PAC adsorption and ozonation than their parent pesticides. However, the TPs that were difficult to remove via PAC adsorption did not induce strong mutagenicity after chlorination, and the TPs that were associated with strong mutagenicity after chlorination could be removed via PAC adsorption. Therefore, PAC adsorption is hypothesized to be an effective method of treating drinking water to reduce the possibility of post-chlorination mutagenicity associated with both TPs and their parent pesticides. Graphical abstract

Description: Publication date: 1 July 2018 Source: Water Research, Volume 138 Author(s): Andrii Butkovskyi, Ann-Hélène Faber, Yue Wang, Katja Grolle, Roberta Hofman-Caris, Harry Bruning, Annemarie P. Van Wezel, Huub H.M. Rijnaarts Ozonation, sorption to granular activated carbon and aerobic degradation were compared as potential treatment methods for removal of dissolved organic carbon (DOC) fractions and selected organic compounds from shale gas flowback water after pre-treatment in dissolved air flotation unit. Flowback water was characterised by high chemical oxygen demand and DOC. Low molecular weight (LMW) acids and neutral compounds were the most abundant organic fractions, corresponding to 47% and 35% of DOC respectively. Ozonation did not change distribution of organic carbon fractions and concentrations of detected individual organic compounds significantly. Sorption to activated carbon targeted removal of individual organic compounds with molecular weight >115 Da, whereas LMW compounds remained largely unaffected. Aerobic degradation was responsible for removal of LMW compounds and partial ammonium removal, whereas formation of intermediates with molecular weight of 200–350 Da was observed. Combination of aerobic degradation for LMW organics removal with adsorption to activated carbon for removal of non-biodegradable organics is proposed to be implemented between pre-treatment (dissolved air floatation) and desalination (thermal or membrane desalination) steps. Graphical abstract

Description: Publication date: 1 July 2018 Source: Water Research, Volume 138 Author(s): Yang Zhou, Jin Jiang, Yuan Gao, Su-Yan Pang, Jun Ma, Jiebin Duan, Qin Guo, Juan Li, Yue Yang Recently, in situ chemical oxidation (ISCO) using peroxymonosulfate (PMS) for environmental decontamination has received increasing interest. In this study, oxidation kinetics and products of four steroid estrogens (i.e., estrone, 17β-estradiol, estriol, and 17α-ethinylestradiol) by PMS under various conditions were investigated. PMS could fairly degrade steroid estrogens over the pH range of 7–10, and the degradation rate increased with the increase of solution pH. This pH-dependence was well described by parallel reactions between individual acid-base species of steroid estrogens (E and E − ) and PMS (HSO 5 − and SO 5 2− ), where specific second-order rate constants for E − with HSO 5 − and SO 5 2− were in the range of 2.11–5.58 M −1 s −1 and 0.77–1.25 M −1 s −1 , respectively. Identification of oxidation products by liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometer showed that PMS readily oxidized the phenolic group of steroid estrogens, leading to the generation of hydroxylated and ring-opening products. The presence of bromide and chloride ions (Br − and Cl − ) at environmentally relevant levels could greatly accelerate the degradation of steroid estrogens by PMS with the formation of halogenated aromatic products. This effect was quantitatively estimated by a kinetic model, where the formation of free bromine and chorine and their rapid electrophilic substitution with steroid estrogens were taken into consideration. Eco-toxicity of transformation products of 17α-ethinylestradiol by PMS treatment in the absence and presence of bromide and chloride was estimated by quantitative structure–activity relationship analysis using ECOSAR. These findings advance the understanding of ISCO using PMS. Graphical abstract

Description: Publication date: 1 July 2018 Source: Water Research, Volume 138 Author(s): Anu Mikkonen, Kati Yläranta, Marja Tiirola, Lara Ambrosio Leal Dutra, Pauliina Salmi, Martin Romantschuk, Shelley Copley, Jukka Ikäheimo, Aki Sinkkonen The xenobiotic priority pollutant pentachlorophenol has been used as a timber preservative in a polychlorophenol bulk synthesis product containing also tetrachlorophenol and trichlorophenol. Highly soluble chlorophenol salts have leaked into groundwater, causing severe contamination of large aquifers. Natural attenuation of higher-chlorinated phenols (HCPs: pentachlorophenol + tetrachlorophenol) at historically polluted sites has been inefficient, but a 4-year full scale in situ biostimulation of a chlorophenol-contaminated aquifer by circulation and re-infiltration of aerated groundwater was remarkably successful: pentachlorophenol decreased from 400 μg L −1 to 〈1 μg L −1 and tetrachlorophenols from 4000 μg L −1 to 〈10 μg L −1 . The pcpB gene, the gene encoding pentachlorophenol hydroxylase - the first and rate-limiting enzyme in the only fully characterised aerobic HCP degradation pathway - was present in up to 10% of the indigenous bacteria already 4 months after the start of aeration. The novel quantitative PCR assay detected the pcpB gene in situ also in the chlorophenol plume of another historically polluted aquifer with no remediation history. Hotspot groundwater HCPs from this site were degraded efficiently during a 3-week microcosm incubation with one-time aeration but no other additives: from 5400 μg L −1 to 1200 μg L −1 and to 200 μg L −1 in lightly and fully aerated microcosms, respectively, coupled with up to 2400% enrichment of the pcpB gene. Accumulation of lower-chlorinated metabolites was observed in neither in situ remediation nor microcosms, supporting the assumption that HCP removal was due to the aerobic degradation pathway where the first step limits the mineralisation rate. Our results demonstrate that bacteria capable of aerobic mineralisation of xenobiotic pentachlorophenol and tetrachlorophenol can be present at long-term polluted groundwater sites, making bioremediation by simple aeration a viable and economically attractive alternative. Graphical abstract