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• Zwitterionic hydrogel nanolayer was synthesized by interfacial polymerization. • Zwitterionic monomer modulated the hydrogel layer structure and membrane characters. • Zwitterionic hydrogel hindered the adhesion of biomacromolecules and killed microbes. • The growth of biofilm on zwitterionic hydrogel nanolayer surface was inhibited. Ultralow-pressurized ultrafiltration membrane process with low energy consumption is promising in surface water purification. However, membrane fouling and low selectivity are significant barriers for the wide application of this process. Herein, an ultrathin zwitterionic hydrogel nanolayer was in-situ grown on polysulfone ultrafiltration membrane surface through interfacially-initiated free radical polymerization. The hydrogel-modified membrane possessed improved biological fouling resistance during the dynamic filtration process (bovine serum albumin, Escherichia coli and Staphylococcus aureus), comparing with commercial polysulfone membrane. The enhanced biofouling resistance ability of zwitterionic hydrogel nanolayer was derived from the foulant repulsion of hydration shell and the bactericidal effect of quaternary ammonium, according to the results of foulant-membrane interaction energy analyses and antibacterial performances. In surface water treatment, the zwitterionic hydrogel layer inhibited biofouling and resulted in the formation of a loose and thin biofilm. In addition, the hydrogel-modified membrane possessed 22% improvement in dissolved organic carbon (DOC) removal and 134% increasement in stable water flux, compared to commercial polysulfone membrane. The in-situ grown zwitterionic hydrogel nanolayer on membrane surface offers a prospectively alternative for biofouling control in ultralow-pressurized membrane process. [Display omitted] [ABSTRACT FROM AUTHOR]

• A solar evaporation system is designed to concentrate liquid digestate. • Liquid digestate concentration efficiency can reach up to 43.33%. • The recovery of ammonia nitrogen and soluble salts can reach 78.39% and 84.19%. • The cost of 100 ton/d liquid digestate concentration is 1.08 USD/ton. • CO 2 mitigation of 2.40 × 105 tons and carbon credits of 3.48 × 106 USD can be achieved. The safe and efficient treatment and resource recovery of the large amount of liquid digestate (LD) produced by biogas plants has become an important factor limiting the development of the biogas industry. In this study, a solar evaporation system was developed based on low cost, high efficiency, and high nutrient recovery of LD concentration. The effects of different parameters, including solar radiation, LD flowrate, and daily treatment capacity, on the concentration efficiency, nutrient recovery, and thermal efficiency were investigated. Economic and enviroeconomic analyses were conducted to comprehensively assess the feasibility and environmental benefits of the system for large-scale biogas plants. The results showed that the higher the solar radiation, the higher the air temperature and its saturation vapor pressure, which led to an increase in the concentration efficiency of LD. The LD concentration efficiency can reach up to 43.33% when the average daily solar radiation was 773.08 W/m2. High solar radiation also contributed to high LD temperature, leading to an increase in the percentage of free ammonia (NH 3) in the LD, which was not conducive to the recovery of ammonia nitrogen (NH 3 N). By increasing the LD flow rate, the heat and mass exchange between air and LD in the spray chamber was enhanced, resulting in higher concentration efficiency. The variation of LD flow rate and daily treatment capacity had little effect on nutrient recovery. The recovery of NH 3 N and soluble salts in the concentrated phase could be as high as 78.39% and 84.19%, respectively, when the initial pH of LD was 5, the air flow rate was 0.03 m3/s, and the LD flow rate was 6 L/min. In addition, the economic analysis indicated that the concentration cost of the system in treating a daily LD production of 100 tons was 1.08 USD/ton. The solar evaporation system can reduce CO 2 emissions by 2.40 × 105 tons and earn carbon credits of 3.48 × 106 USD over its lifetime. This study provides a new direction and reference for LD concentration. [Display omitted] [ABSTRACT FROM AUTHOR]

l Reactive Zeolite@MnO x (s) filter was dynamically formed in presence of chlorine. l Mn(III)/(IV) oxide nanosheet catalyst was dynamically in situ-growing and assembled. l Mn(III)/(IV) species transformation was responsible for accelerated Mn2+ oxidation. l Less chlorine was needed byiZeolite@MnO x (s) filter for Mn2+ removal in real water. Manganese contamination is ubiquitous in ground water. Water eutrophication also exaggerates manganese release and contamination in surface water. However, conventional manganese(II) removal process through sand filter is low-efficiency and long-term ripening. Manganese exceeding standard is still a bottleneck issue for drinking water plants. To provide a quick-setup and low-cost means, we invented an accelerated catalytic oxidation filtration process through porous zeolite filter with dynamically coating of manganese oxide nanocatalysts. In dynamic filtration process, the addition of chlorine less than redox stoichiometric consumption can efficiently remove dissolved manganese(II) from contaminated tap water, ground water and Songhua river water. Characterization results showed that a continuous manganese(III)/(IV) oxide nanosheet catalyst was dynamically in situ -growing and assembled into 3D porous superstructure in the reactive Zeolite@MnO x (s) filter. Active Mn(III) species on the edges of MnO x (s) nanosheets were dynamically generated and transferred into stable Mn(IV) species on the layer-structured surface. The cycling transformation of manganese(III)/(IV) species was responsible for the accelerated catalytic oxidation of dissolved manganese(II) by chlorine. Without process changes in drinking water plant, the porous Zeolite@MnO x (s) media could be feasibly integrated onto the existing sand filtration tanks for emergence handling of manganese(II) contamination. This novel reactive Zeolite@MnO x (s) filter with higher hydraulic conductivity provides a high-efficiency, scalable and low-cost technique for the manganese(II) removal from various of water environments. [Display omitted] [ABSTRACT FROM AUTHOR]

Low cost, green, regenerable catalyst for persulfate activation is the popularly concerned topic for the degradation of persistent organic micropollutants in drinking water. In this work, natural montmorillonite (MMT) saturated with Fe(III) ions was used to activate peroxymonosulfate (PMS) for the degradation of atrazine in raw drinking water. Results showed that the adsorption of atrazine was quickly completed within 1 min and the percentage degradation was finally increased up to 94.1% in 60 min. The d 001 -spacing of MMT was enlarged to 2.91 nm at the most by Fe(III) saturation. Atrazine was adsorbed into the nanoscale interlayer of Fe(III)-saturated montmorillonite (Fe-MMT), where the Fe(III)/Fe(II) cycle was sustainably realized through the accelerated transformation of electrons between Fe(III) and PMS. Meanwhile, the in-situ generated Fe(II) accelerated the decomposition of PMS to further proceed the degradation of atrazine through the oxidation of HO• and SO 4 •- radicals. This nanoconfined effect of PMS activation by Fe(III) was further confirmed through the degradation of various micropollutants in the backgrounds of river water. The selective catalytic oxidation of micropollutants through PMS activation was attributed to the 2D mesoporous structure of Fe-MMT, inhibiting the interlayer adsorption of larger molecular backgrounds (humic acids etc.). Fe(III)-saturated montmorillonite (Fe-MMT) provided a feasible and scalable method of PMS activation by Fe(III) for the degradation of micropollutants in drinking water. Mechanisms of atrazine degradation through PMS activation by Fe-MMT. Image 1 • Fe(III)-saturated montmorillonite (Fe-MMT) was used to catalyze the PMS activation. • Fe(III)/Fe(II) cycle was realized in the nanoconfined interlayer of Fe-MMT. • Micropollutants were degraded through the oxidation of HO.• and SO 4 •- radicals. • Selective catalytic oxidation of micropollutants performed well in river water. [ABSTRACT FROM AUTHOR]

Increasing attention has been focused on the removal of micropollutants from contaminated drinking source water. However, low rejection efficiency and membrane fouling still inhibit further application of nanofiltration membrane in this field. Interesting results were found that the residual hydrolyzed-aluminum nanoparticles from supernatant after coagulation and sedimentation strongly improved the nanofiltration performance for micropollutant removal. A simulated raw water containing humic acids, micropollutants and kaolinite clay was employed to investigate the factors of water matrix affecting the nanoparticle-enhanced nanofiltration for micropollutant removal. Results of experiments showed that these hydrolyzed-aluminum nanoparticles easily induced the aggregation of bisphenol-A (BPA) and humic acids in the supernatant. The enhancement of BPA removal was mainly attributed to the repelling interaction between the Al-BPA-DOC complexity and in situ -modified membrane surface during nanofiltration. 'This in situ surface modification by the hydrolyzed-aluminum nanoparticles improved membrane hydrophilicity, roughness and positively-charging capacity. For the treatment of River Songhua water spiked with micropollutant, the percentage removal of BPA was improved to be 88.5%, much more than the case of single nanofiltration without coagulation (60.7%). Meanwhile, the membrane fouling was reduced by 2.13 times than the case of single nanofiltration without the dynamically deposited-layer of nanoparticles. This in situ modification of nanofiltration membrane by hydrolyzed-aluminum nanoparticles achieved excellent removal efficiency for micropollutants from River Songhua water background. Image 1 • Micropollutant removal by nanofiltration was enhanced by hydrolyzed-aluminum nanoparticles. • Loosely hydrophilic deposition on membrane surface alleviated membrane fouling. • Aluminum-deposited membrane achieved excellent performance in background of river water. [ABSTRACT FROM AUTHOR]

• PCA improved SMX removal in Fe(III)/PAA system under truly neutral pH conditions. • PCA enhanced the catalytic activity of Fe(III) on PAA under neutral pH conditions. • CH 3 C(O)OO-Fe(III)-PCA was proposed as the primary reactive specie for SMX removal. • PCA/Fe(III)/PAA system had strong anti-interference ability to water constituents. • PCA/Fe(III)/PAA system exhibited high SMX removal efficiency in nature waters. The practical application of the Fe-catalyzed peracetic acid (PAA) processes is seriously restricted due to the need for narrow pH working range and poor anti-interference capacity. This study demonstrates that protocatechuic acid (PCA), a natural and eco-environmental phenolic acid, significantly enhanced the removal of sulfonamide antibiotics in Fe(III)/PAA process under actually neutral pH conditions (6.0–8.0) by complexing Fe(III). With sulfamethoxazole (SMX) as the model contaminant, the pseudo-first-order rate constant of SMX elimination in PCA/Fe(III)/PAA process was 63.5 times higher than that in Fe(III)/PAA process at pH 7.0, surpassing most of the previously reported strategies-enhanced Fe-catalyzed PAA processes (i.e., picolinic acid and hydroxylamine etc.). Excluding the primary contribution of reactive species commonly found in Fe-catalyzed PAA processes (e.g., •OH, R-O•, Fe(IV)/Fe(V) and 1O 2) to SMX removal, the Fe(III)-peroxy complex intermediate (CH 3 C(O)OO-Fe(III)-PCA) was proposed as the primary reactive species in PCA/Fe(III)/PAA process. DFT theoretical calculations indicate that CH 3 C(O)OO-Fe(III)-PCA exhibited stronger oxidation potential than CH 3 C(O)OO-Fe(III), thereby enhancing SMX removal. Four potential removal pathways of SMX were proposed and the toxicity of reaction solution decreased with the removal of SMX. Furthermore, PCA/Fe(III)/PAA process exhibited strong anti-interference capacity to common natural anions (HCO 3 −, Cl−and NO 3 −) and humic acid. More importantly, the PCA/Fe(III)/PAA process demonstrated high efficiency for SMX elimination in actual samples, even at a trace Fe(III) dosage (i.e., 5 μM). Overall, this study provided a highly-efficient and eco-environmental strategy to remove sulfonamide antibiotics in Fe(III)/PAA process under actually neutral pH conditions and to strengthen its anti-interference capacity, underscoring its potential application in water treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

Understanding the influences of cations on membrane fouling was important to improve the performance of membrane filtration system, however, opposite conclusions were made in different studies. Meanwhile, although the influences of cation concentration have been studied extensively, few attentions have been paid to the cation valence. To clarify it, the effects of typical cations on membrane fouling and cleaning, as well as the related mechanisms were investigated systemically in this study. K+ and Ca2+ were chosen as the representative cations, and humic acid (HA) was chosen as the membrane foulants. The results demonstrated Ca2+ promoted the formation of reversible fouling, meanwhile higher removal efficiency of HA could also be achieved with the assistance of filtration cake containing HA + Ca2+. However, K+ led to the formation of more recalcitrant irreversible fouling. By comparing the concentration of cations in feed and permeate, analyzing the influence of cations on size of HA flocs, and the detailed SEM, AFM and TEM observation, it could be found that different mechanisms dominated the interaction between cations and HA. The bridging effect induced by Ca2+ attributed to the extension of HA molecules, while the electrostatic shielding effect induced by K+ led to the compression of them. Moreover, the different characteristics of hydrated Ca2+ and K+ also contributed to the different structures of foulant layers formed by HA + Ca2+ and HA + K+. Given the abundance of K+ and Ca2+ in natural water, results of this study can provide valuable advice for practical membrane filtration process. Image 1 • K+ makes the HA pollution layer more compact by electrostatic shielding. • HAs aggregation driving by HA-Ca2+ complexation contributes to pollutant removal. • The hydration force of cations is a key factor for membrane fouling. [ABSTRACT FROM AUTHOR]

The novel H 2 O 2 –MnO 2 system was developed to achieve highly efficient membrane cleaning for both fouled PVDF and PES membranes in this study. Compared with conventional chemical cleaning process in which the whole membrane module had to be soaked in highly concentrated solution of chemical reagent for long period of time, the H 2 O 2 –MnO 2 cleaning process conducting for only 5 min in 0.5 wt% H 2 O 2 solution could achieve more than 95% recovery of permeate flux and almost total removal of the irreversible foulants. More importantly, the permeate flux and filtration efficiency of the membrane could be still kept stable after 6 runs of consecutive fouling and cleaning. Based on the systematic microscopic analyses, Electron Spin Resonance (ESR), Fourier Transform Infrared Spectroscopy (FTIR), as well as the quenching experiments with different free radical scavengers, the outstanding performance of H 2 O 2 –MnO 2 system was attributed to the generation of both free radicals and abundant oxygen simultaneously, leading to the physico-chemical membrane cleaning. Conclusively, the newly developed H 2 O 2 –MnO 2 system demonstrated noteworthy advantages on efficient membrane cleaning, and exhibited highly potential for the wide application in practical water treatment process. Image 1 • H 2 O 2 –MnO 2 system is utilized to clean membrane for the first time. • Efficient and nondestructive physico-chemical cleaning are achieved. • Free radicals and oxygen are generated synchronously for membrane cleaning. [ABSTRACT FROM AUTHOR]

• A novel system was designed to improve the efficiency of contaminant removals. • Multiple-stratified environments were artificially formed in a single system. • The microbial communities were tailored to control nitrogen transformation path. • Complementary of functional genes supported stability of nitrogen transformations. A pilot-scale upgraded gravity-driven submerged membrane (GDSM) reactor was constructed to enhance nitrogen removal. It was artificially formed multiple stratified environments (dissolved oxygen (DO) and substrate supply (TOC, TN, COD, NH 4 +-N, NO 2 −-N, and NO 3 −-N)) by embedding moving water baffles to control water-flow process in bulk liquid with slow-flowing liquid state. Significant diversity and relative abundance of microorganisms associated with nitrogen transformation paths (i.e., ammonia-oxidizing archaea, ammonia-oxidizing bacteria, nitrite oxidizing bacteria, and denitrifying bacteria) were tailored to distribute on different spatial and temporal regions, and performed their dominant functions. The process simultaneously integrated diverse and effective nitrogen transformation paths (i.e., nitrification, partial nitrification, denitrification, anammox, and dissimilatory nitrate reduction) to achieve high nitrogen removal, with NH 4 +-N, TN, and COD eliminated by 94.68 ± 2.55%, 55.16 ± 5.53%, and 80.17 ± 6.75%, respectively. Gene expressions involved in the nitrogen transformations were estimated by qPCR to explore the shifts of dominant nitrogen transforming bioreactions in multiple stratified environments. Pearson correlation coefficients supported that the functional genes had more stable and active ability by complementing each other. As a result, an endogenous integration of diverse nitrogen transformation paths was achieved in a single system by artificially tailoring the distributions of microbial communities and gene expressions with enhanced nitrogen removal. Image, graphical abstract [ABSTRACT FROM AUTHOR]