Description: Publication date: 1 August 2018 Source: Water Research, Volume 139 Author(s): Li Ling, Zhaobing Li, Jingyun Fang, Chii Shang The Co(II)/peroxymonosulfate (Co(II)/PMS) process, producing sulfate radicals (SO 4 •- ), effectively removes organic pollutants in water, while producing a significant amount of bromate (BrO 3 − ) in the presence of bromide (Br − ). This paper investigates the ammonia (NH 3 ) addition, chlorine-ammonia (Cl 2 -NH 3 ) and ammonia-chlorine (NH 3 -Cl 2 ) pretreatment strategies in controlling BrO 3 − formation in 20 min in the Co(II)/PMS process at pH 4.0. The addition of NH 3 retarded the BrO 3 − formation, but only at a reduction level of about 9.5% for NH 3 concentration of 50 μM, and was mainly attributed to the protonation of NH 3 at pH 4 (99.99% as NH 4 + , did not react with HOBr). Both the Cl 2 -NH 3 and NH 3 -Cl 2 pretreatment strategies at HOCl and NH 3 dosages of 15 and 50 μM, respectively, reduced 95% or more of the overall BrO 3 − formation and retarded the BrO 3 − formation, with the NH 3 -Cl 2 pretreatment strategy outperforming Cl 2 -NH 3 . The reduction of the BrO 3 − formation was mainly attributed to the formation of monochloramine (NH 2 Cl) in both pretreatment strategies. NH 2 Cl effectively outcompetes SO 4 •- to react with HOBr and forms NHBrCl, with the apparent reaction rate constant between NH 2 Cl and HOBr more than 100 times faster than that between SO 4 •- and HOBr. However, the oxidation/degradation of NHBrCl in the Co(II)/PMS process reforms HOBr, and, although less in quantity, is oxidized to BrO 3 − at higher Co(II) and Br − concentrations. Thus, the NH 3 -Cl 2 and Cl 2 -NH 3 pretreatment strategies inhibit the BrO 3 − formation more significantly at lower Co(II) and Br − concentrations. In all cases, the generation of SO 4 •- in 20 min was not affected by the implementation of the three BrO 3 − pretreatment strategies. Graphical abstract

Description: Publication date: 1 July 2018 Source: Water Research, Volume 138 Author(s): Jun Gu, Qin Yang, Yu Liu The conventional biological processes for municipal wastewater are facing the challenges of high energy consumption and production of excessive sludge. To address these two emerging issues, this study demonstrated the feasibility to integrate mainstream anammox into an A-2B process for municipal wastewater treatment towards energy-efficient operation with reduced sludge production. In the proposed A-2B process, an anaerobic fixed bed reactor (AFBR) served as A-stage for COD capture, an anammox moving bed biofilm reactor (MBBR) was employed as B2-stage, which received effluent containing nitrite from a sequencing batch reactor (SBR) at B1-stage. The results showed that under the operation conditions studied, 58% of influent COD was converted methane gas at A-stage, and 87% total inorganic nitrogen (TIN) removal was achieved with the effluent TIN concentration of 6.5 mg/L. Moreover, it was shown that at least 75% of sludge reduction was obtained due to the COD capture at A-stage. The high-throughput sequencing analysis further revealed that Candidatus Kuenenia was the dominant genus responsible for the observed anammox at B2-stage MBBR. This study clearly demonstrated a novel process configuration for sustaining mainstream anammox for municipal wastewater reclamation towards energy-efficient operation with minimized sludge production. Graphical abstract

Description: Publication date: 1 July 2018 Source: Water Research, Volume 138 Author(s): Daniel Hering, Angel Borja, J.Iwan Jones, Didier Pont, Pieter Boets, Agnes Bouchez, Kat Bruce, Stina Drakare, Bernd Hänfling, Maria Kahlert, Florian Leese, Kristian Meissner, Patricia Mergen, Yorick Reyjol, Pedro Segurado, Alfried Vogler, Martyn Kelly Assessment of ecological status for the European Water Framework Directive (WFD) is based on “Biological Quality Elements” (BQEs), namely phytoplankton, benthic flora, benthic invertebrates and fish. Morphological identification of these organisms is a time-consuming and expensive procedure. Here, we assess the options for complementing and, perhaps, replacing morphological identification with procedures using eDNA, metabarcoding or similar approaches. We rate the applicability of DNA-based identification for the individual BQEs and water categories (rivers, lakes, transitional and coastal waters) against eleven criteria, summarised under the headlines representativeness (for example suitability of current sampling methods for DNA-based identification, errors from DNA-based species detection), sensitivity (for example capability to detect sensitive taxa, unassigned reads), precision of DNA-based identification (knowledge about uncertainty), comparability with conventional approaches (for example sensitivity of metrics to differences in DNA-based identification), cost effectiveness and environmental impact. Overall, suitability of DNA-based identification is particularly high for fish, as eDNA is a well-suited sampling approach which can replace expensive and potentially harmful methods such as gill-netting, trawling or electrofishing. Furthermore, there are attempts to replace absolute by relative abundance in metric calculations. For invertebrates and phytobenthos, the main challenges include the modification of indices and completing barcode libraries. For phytoplankton, the barcode libraries are even more problematic, due to the high taxonomic diversity in plankton samples. If current assessment concepts are kept, DNA-based identification is least appropriate for macrophytes (rivers, lakes) and angiosperms/macroalgae (transitional and coastal waters), which are surveyed rather than sampled. We discuss general implications of implementing DNA-based identification into standard ecological assessment, in particular considering any adaptations to the WFD that may be required to facilitate the transition to molecular data. 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): 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): 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 August 2018 Source: Water Research, Volume 139 Author(s): Fuhar Dixit, Benoit Barbeau, Madjid Mohseni Microcystins are the most commonly occurring cyanotoxins, and have been extensively studied across the globe. In the present study, a strongly basic anion exchange resin was employed to investigate the removal of Microcystin-LR (MCLR), one of the most toxic microcystin variants. Factors influencing the uptake behavior included the MCLR and resin concentrations, resin dosage, and natural organic matter (NOM) characteristics, specifically, the charge density and molecular weight distribution of source water NOM. Equivalent background concentration (EBC) was employed to evaluate the competitive uptake between NOM and MCLR. The experimental data were compared with different mathematical and physical models and pore diffusion was determined as the rate-limiting step. The resin dose/solute concentration ratio played a key role in the MCLR uptake process and MCLR removal was attributed primarily to electrostatic attractions. Charge density and molecular weight distribution of the background NOM fractions played a major role in MCLR removal at lower resin dosages (200 mg/L ∼ 1 mL/L and below), where a competitive uptake was observed due to the limited exchange sites. Further, evidences of pore blockage and site reduction were also observed in the presence of humics and larger molecular weight organic fractions, where a four-fold reduction in the MCLR uptake was observed. Comparable results were obtained for laboratory studies on synthetic laboratory water and surface water under similar conditions. Given their excellent performance and low cost, anion exchange resins are expected to present promising potentials for applications involving the removal of removal of algal toxins and NOM from surface waters. 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 August 2018 Source: Water Research, Volume 139 Author(s): Zhe Kong, Lu Li, Rei Kurihara, Kengo Kubota, Yu-You Li The complete methanogenic degradation of N , N -dimethylformamide (DMF) was achieved in this study. Initially, DMF was found to be feebly degradable by a lab-scale submerged anaerobic membrane bioreactor (SAnMBR) using normal anaerobic digestion sludge (ADS) even after 120-day's culturing. However, aerobic DMF-degrading activated sludge (AS) was rapidly cultivated in a continuous aeration reactor (CAR). A specially designed anaerobic co-cultured sludge (ACS) made by artificially mixing AS with ADS was successfully domesticated by a long term repeated batch experiment. The results demonstrated that ACS could effectively degrade over 5000 mg L −1 DMF for methane recovery. The metabolic pathway and stoichiometric equation of DMF methanogenic degradation were also revealed and verified in detail. It was confirmed that under the anaerobic condition, with the help of enzyme, DMF converts into dimethylamine and formic acid, and the intermediates are effectively fermented through methylotrophic/hydrogenotrophic methanogenesis. Analysis of the microbial community suggested that some facultatively anaerobic bacteria played the key roles in methanogenic degradation due to their DMF-hydrolyzing ability. By co-culturing two sources of inoculum under the anaerobic condition, the symbiosis of facultatively anaerobic DMF-hydrolyzing bacteria and methylotrophic/hydrogenotrophic methanogens makes methanogenic degradation of DMF available. This study also provides a novel sludge cultivation method for anaerobic treatment of degradation-resistant organics. Graphical abstract