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Reverse osmosis (RO) is one of the most fundamental membrane technology because it has higher salt rejections, which suffers from the issue of membrane fouling, as the membrane is inevitably exposed to foulants during the filtration process. For different fouling mechanisms of RO membrane, physical and chemical cleaning are widely used in the control of RO membrane fouling. The present study investigated the performance and water flux recovery using osmotic cleaning to clean the typical inorganic and organic foulants on RO membrane for textile printing and dyeing wastewater treatment. The effects of operation conditions (i.e., the concentration of cleaning solution, the filtrating time and cleaning time, and the flow rate of cleaning solution) on relative water flux recovery were examined. The results show that a highly water flux recovery (98.3% for cleaning of inorganic fouling and 99.6% for cleaning of organic fouling) was achieved under optimal operation of the concentration and flow rate of cleaning solution and the filtrating and cleaning time. Moreover, the experiment of repeated "filtrating-cleaning" cycles indicated that the osmotic cleaning has highly performance of recoverability of water flux (over 95.0%) can be extended in a relatively long time. The experimental results and changes on SEM and AFM images of RO membrane confirmed the successful development and application of osmotic cleaning for inorganic and organic fouling of RO membrane., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

In this work, heterogeneous catalytic ozonation for the treatment of bio-treated saccharin sodium production wastewater (BSSW) was comprehensively investigated with pilot- and full-scale systems, with special emphasis on the effects of Cu 2+ in the original wastewater on catalyst activity. The results of semi-batch and continuous experiments show that heterogeneous catalytic ozonation was effective in removing organic compounds from high-salinity wastewater and that Cu 2+ in the original wastewater had a substantial effect on the performance of the process. The retention of 0.15 mM Cu 2+ in BSSW increased the chemical oxygen demand (COD) removal by 31% in semi-batch reactor with heterogeneous catalytic ozonation. The stable COD removal efficiencies ranged from 74% to 66.4% for a 9-month operation, indicating that Cu 2+ with an appropriate concentration in the original BSSW not only improved the COD removal efficiencies but also inhibited catalyst deactivation; catalyst deactivation was mainly caused by the deposition of inorganic salts on the catalyst surface. Cu 2+ combined with some anions to inhibit the formation and deposition of inorganic salts that could easily cause deactivation. The deposited copper salts were readily eliminated, especially during backflushing operations. Moreover, in a full-scale study, heterogeneous catalytic ozonation with 0.15 mM Cu 2+ in BSSW exhibited stable COD removal efficiencies (51%-83%) after over 3 years of operation. This study offers a new idea for using the inherent properties of wastewater to perform advanced treatments on high-salinity industrial wastewater through heterogeneous catalytic ozonation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Electrocoagulation (EC) using iron (Fe), zinc (Zn) and aluminum (Al) electrodes was comparatively applied in the treatment of selenium (Se) in flour production (FP) wastewater. It was indicated that EC treatment with Fe anode obtained highest removal efficiency (79.1%) for Se in the 90 min treatment in the comparative study, which could be attributed to the superior adsorption capacity of in-situ generated iron flocs. Removal of Se resulted from electrodeposition and adsorption to in-situ generated flocs in EC treatment, and the operational conditions significantly influenced the Se removal performance in this work. The results showed the acidic condition and higher current density favored EC treatment on Se removal, EC removed up to 97.8% of Se at pH 4 under 15 mA cm -2 , whereas it obtained 83.5% and 50.4% of removal efficiency at pH 7 and 10, respectively. There was competitive adsorption in the process of selenium removal, as the in-situ generated flocs effectively removed 35.6% of humic acid-like (HA-like) substance in FP wastewater after 90 min treatment. The FTIR results showed that HA-like substance mainly contained the protein water hydrogen bond, carboxylate COO antisymmetric stretching and other functional groups. Through the analysis of existence of Se in flocs and wastewater, it can be found that approximately 2.8%-3.92% of Se was removed by electrodeposition process. This study illustrated the Se removal mechanism and provided constructive suggestion for food manufacturing to the metal removal and utilization of advanced treatment., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Low pressure reverse osmosis (LPRO) has been increasingly used in advanced treatment of pulp and paper wastewater (PPWW) for the purpose of water reuse. However, membrane fouling is a major problem encountered by full-scale RO systems due to the organic and inorganic contents of the feedwater. Electrocoagulation (EC) as an effective treatment for foulants removal can be applied in pre-filtration. Therefore, the LPRO membrane fouling mechanism and the membrane fouling control performance by EC treatment were investigated in this study. EC pretreatment could reduce the membrane fouling and improve the membrane flux by 31%, by effectively removing and/or decomposing the organic pollutants in PPWW. Fluorescent spectrometry analyses of the feedwater and the permeate revealed that humic acid-like and fulvic acid-like organics in PPWW were the major foulants for the LPRO membranes. Fourier transformation infrared spectrometry results confirmed that the organic foulants contained benzoic rings and carboxylic groups, which were typical for organic substances. EC effectively removed organic pollutants containing functional groups such as carboxylic acid COH out-of-plane bending, olefin (trans), and NH 3 + symmetrical angle-changing. Moreover, the extended Derjaguin-Landau-Verwey-Overbeek model suggested that the membrane filtered 30-min EC-treated PPWW had the strong repulsion force to foulants due to the higher cohesion energy (12.1 mJ/m 2 ) and the lower critical load, which theoretically explained the reason of EC pretreatment on membrane fouling control., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The effects of polyaluminum chloride (PACl) hydrolysis prior to coagulation on both the coagulation zone and coagulation performance of a kaolin suspension were investigated by a novel jar test named the "reversed coagulation test". The tests showed that PACl hydrolysis prior to coagulation decreased the performance of charge neutralization coagulation in the case of short-time slow mixing (10min; G=15sec -1 ) and increased the optimal dosage for charge neutralization and sweep coagulation. Moreover, the hydrolysis time had insignificant effects on the size and zeta potential of PACl precipitates and the residual turbidity of the raw water. However, PACl hydrolysis prior to coagulation and the size of PACl precipitates had a negligible effect on the performance of sweep coagulation. The results imply that, in practice, preparing a PACl solution with deionized water, rather than tap water or the outlet water from a wastewater treatment unit, can significantly save PACl consumption and improve the performance of charge neutralization coagulation, while preparing the PACl solution with tap or outlet water would not affect the performance of sweep coagulation. In addition, the optimal rapid mixing intensity appears to be determined by a balance between the degree of coagulant hydrolysis before contacting the primary particles and the average size of flocs in the rapid mixing period. These results provide new insights into the role of PACl hydrolysis and will be useful for improving coagulation efficiency., (Copyright © 2016. Published by Elsevier B.V.)

A submerged internal circulating membrane coagulation reactor (MCR) was used to treat surface water to produce drinking water. Polyaluminum chloride (PACl) was used as coagulant, and a hydrophilic polyvinylidene fluoride (PVDF) submerged hollow fiber microfiltration membrane was employed. The influences of trans-membrane pressure (TMP), zeta potential (ZP) of the suspended particles in raw water, and KMnO 4 dosing on water flux and the removal of turbidity and organic matter were systematically investigated. Continuous bench-scale experiments showed that the permeate quality of the MCR satisfied the requirement for a centralized water supply, according to the Standards for Drinking Water Quality of China (GB 5749-2006), as evaluated by turbidity (<1 NTU) and total organic carbon (TOC) (<5mg/L) measurements. Besides water flux, the removal of turbidity, TOC and dissolved organic carbon (DOC) in the raw water also increased with increasing TMP in the range of 0.01-0.05MPa. High ZP induced by PACl, such as 5-9mV, led to an increase in the number of fine and total particles in the MCR, and consequently caused serious membrane fouling and high permeate turbidity. However, the removal of TOC and DOC increased with increasing ZP. A slightly positive ZP, such as 1-2mV, corresponding to charge neutralization coagulation, was favorable for membrane fouling control. Moreover, dosing with KMnO 4 could further improve the removal of turbidity and DOC, thereby mitigating membrane fouling. The results are helpful for the application of the MCR in producing drinking water and also beneficial to the research and application of other coagulation and membrane separation hybrid processes., (Copyright © 2016. Published by Elsevier B.V.)

The effect of acidification and heat treatment of raw red mud (RM) and fly ash (FA) on the sorption of phosphate was studied in parallel experiments. The result shows that a higher efficiency of phosphate removal was acquired by the activated samples than by the raw ones. The sample prepared by using the RM stirred with 0.25 M HCl for 2h (RM0.25), as well as another sample prepared by heating the RM at 700 degrees C for 2h (RM700), registered the maximum removal of phosphate (99% removal of phosphate). This occurred when they were used in the phosphate sorption studies conducted at pH 7.0 and 25 degrees C with the initial PO(4)(3-) concentration of 155 mg P/l. The FA samples treated in the same way described above can achieve 7.0 and 8.2 mg P/l phosphate removal for FA0.25 and FA700 respectively, corresponding to 45.2% and 52.9% removal. The activated materials performed higher phosphate removal over broader pH range compared with the raw ones. The influences of various factors, such as initial pH and initial phosphate concentration on the sorption capacity were also studied in batch equilibration technique. Solution pH significantly influenced the sorption. Each sample achieved the maximal removal of phosphate at pH 7.0. The amount of phosphate removal increased with the solute concentration. The Freundlich and Langmuir models were used to simulate the sorption equilibrium. The results indicate that the Langmuir model has a better correlation with the experimental data than the Freundlich model.

A novel lanthanum manganese oxide (La0.96Mn0.96O3, LMO) was synthesized for advanced phosphate removal to alleviate water eutrophication process. The adsorbent had a specific surface area of 18.51 m2/g with pH at point of zero charge of 6.6; exhibited excellent phosphate adsorption capacity of 168.4 mg/g; performed well in a wide pH range from 3 to 10. The phosphate removal was not interfered by coexisting ions. The adsorbent remained 94.8% of its initial adsorption efficiency after reused for four times. Phosphate adsorption process conformed to pseudo-second-order model (R2=0.992) and Langmuir model (R2=0.935). Ligand exchange and electrostatic interaction played important roles in phosphate removal. In addition, the actual sewage secondary effluent was used to further verify the phosphate removal performance of LMO. For practical water treatment, the LMO showed high phosphate removal efficiency of 83.4% and low residual P of 0.1 mg/L. LMO is a potential candidate for low-concentration phosphate removal in real water environment. [ABSTRACT FROM AUTHOR]

A hybrid process of enhanced coagulation at a high dosage of polyaluminum chloride and flat-sheet cross-flow ultrafiltration was used for the advanced treatment of the effluent from a biological treatment process of deinking wastewater in a paper mill. The experimental results obtained by a small-scale continuous laboratory experimental device showed that the absorption resistance was significantly lower than the membrane intrinsic resistance, the concentration polarization resistance, the pore blocking resistance, and the cake layer resistance and so it can be ignored. With increasing polyaluminum chloride dosage from 0 to 2,000 mgL-1, the total membrane filtration resistance decreased and the membrane flux increased, but the concentration polarization resistance increased. With the increase in cross flow velocity, the total membrane filtration resistance, the pore blocking resistance, the layer resistance, and the concentration polarization resistance all decreased, and consequently, the membrane flux increased. With regard to the concentration polarization resistance, the cross flow velocity had a more significant effect than the trans-membrane pressure. But the trans-membrane pressure had a more significant effect on the layer resistance, the pore blocking resistance, and the total membrane filtration resistance than the cross flow velocity. The filtration resistance at the polyaluminium chloride dosage of <1,000 mgL-1 could be ranked as follows: the membrane intrinsic resistance > the pore blocking resistance > the layer resistance > the concentration polarization resistance> the absorption resistance. But it was the membrane intrinsic resistance > the concentration polarization resistance > the pore blocking resistance > the layer resistance > the absorption resistance at the dosage of ≥1,000 mgL-1. The results are helpful for the membrane fouling control and can promote the application of flat-sheet cross-flow membrane process, resultantly improving the reclaim and reuse of deinking wastewater, and reducing the emission of contaminants in deinking wastewater. Fouling characteristic and control strategy for the cross-flow flat-sheet ultrafiltration membrane (The dotted line means that the fouling control method is not so significant as the others.). Image 1020 • Deinking wastewater was treated by an enhanced coagulation and flat-sheet UF hybrid process. • Appropriate PACl dosage and cross-flow velocity can mitigate membrane fouling. • R g increased with PACl dosage, different in variation trend from R f and R c. • PACl dosage affected the order of filtration resistances. • A strategy for the membrane fouling control was developed. [ABSTRACT FROM AUTHOR]

A highly crystalline phase g-C 3 N 4 , namely poly (heptazine imide) (PHI) was synthesized using molten salts. A high-performance ultrafiltration membrane was prepared by blending PHI nanosheets with Poly(m -phenylene isophthalamide) (PMIA) to obtain casting solution, and further prepared by phase conversion method. Hybrid PMIA membranes were prepared by incorporating 0.02–0.10 wt% of PHI, which were further characterized by SEM, AFM, XRD, FTIR, XPS, TGA and surface zeta potential. The hydrophilicity, water flux, and rejection of bovine serum albumin (BSA) of the membrane significantly increased. For instance, the water permeability of M4 (264.6 Lm−2h−1bar−1) was about 2.3 times that of bare PMIA membrane (113.6 Lm−2h−1bar−1), while maintaining a BSA rejection of 94.7 % for a 1000 mgL−1 BSA feed solution. Moreover, the M4 membrane showed excellent antifouling performance with a flux recovery rate of up to 88.7 % and lower irreversible fouling of 11.3 %. This study may provide reference for the modulation of highly crystalline g-C 3 N 4 structure and its application in membrane fabrication for water treatment. [Display omitted] • PHI nanosheets were successfully synthesized by a simple molten salt method. • PHI/PMIA membranes were prepared using phase inversion method. • The addition of PHI enhances the hydrophilicity and thermal stability of the composite membrane. • M4 membrane exhibited the flux recovery ratio of 88.7 %. [ABSTRACT FROM AUTHOR]

Constructed wetland is an effective method to remove N and P from reclaimed water, but the treatment effect is restricted by low temperature in winter. In this study, a vertical flow constructed wetland based on Iron [Fe (0)]-carbon micro-electrolysis (IC-ME) (IC-CW) was developed for advanced treatment of reclaimed water. The performance of IC-ME carrier on simultaneous N and P removal under different operational conditions and cold temperature was investigated. Studies have shown that when the HRT is 48 h and the influent C/N ratio is 2.5, the removal efficiencies of TN and TP reach to 88.6% and 92.2%. When operating under low temperature conditions (water temperature at 9.6–18.6 °C and ambient temperature at −14.2 to 8.4 °C), the effluent quality is slightly lower than that at normal temperature, with the TN and TP removal efficiencies of 72.7% and 89.2%. The functional microorganisms in IC-CW were analyzed and the results showed that aerobic bacteria and anaerobic bacteria coexist in the IC-CW, and there are both aerobic nitrification and anaerobic denitrification processes in the IC-CW. In addition, there are more functional denitrifying characteristic microorganisms such as Denitratiosoma attached on the IC-ME carrier (2.18%) than that on the ceramsite (0.92%). The developed IC-CW presented significant potential in the practical application for advanced treatment of reclaimed water. [Display omitted] • A vertical flow constructed wetland based on Fe/C micro-electrolysis was developed. • HRT and C/N ratio were optimized for high TN (88.6%) and TP (92.2%) removal. • High TN (72.7%) and TP (89.2%) removal were achieved under low water temperature. • Fe/C micro-electrolysis effectively improved nitrogen and phosphorus removal efficiency. [ABSTRACT FROM AUTHOR]