High performance photodegradation resistant PVA@TiO_(2)/carboxyl-PES self-healing reactive ultrafiltration membrane

The occurrence of ultrafiltration(UF)membrane fouling frequently hampers the sustainable advancement of UF technology.Reactive self-cleaning UF membranes can effectively alleviate the problem of membrane fouling.Nevertheless,the self-cleaning process may accelerate membrane aging.Addressing these concerns,we present an innovative design concept for composite self-healing materials based on self-cleaning UF membranes.To begin,TiO_(2)nanoparticles were incorporated into the polymer molecular structure via molecular design,resulting in the synthesis of TiO_(2)/carboxyl-polyether sulfone(PES)hybrid materials.Subsequently,the nonsolvent-induced phase inversion technique was employed to prepare a novel of UF membrane.Lastly,a polyvinyl alcohol(PVA)hydrogel coating was applied to the hybrid UF membrane surface to create PVA@TiO_(2)/carboxyl-PES self-healing reactive UF membranes.By establishing a covalent bond,the TiO_(2)nanoparticles were effectively and uniformly dispersed within the UF membrane,leading to exceptional self-cleaning properties.Furthermore,the water-absorbing and swelling properties of PVA hydrogel,along with its capacity to form hydrogen bonds with water molecules,resulted in UF membranes with improved hydrophilicity and active self-healing abilities.The results demonstrated that the water contact angle of PVA@5%TiO_(2)/carboxyl-PES UF membrane was 43.1°.Following a 1-h exposure to simulated solar exposure,the water flux recovery ratio increased from 48.16%to 81.03%.Moreover,even after undergoing five cycles of 12-h simulated sunlight exposure,the UF membranes exhibited a consistent retention rate of over 97%,thus fully demonstrating their exceptional self-cleaning,antifouling,and selfhealing capabilities.We anticipate that the self-healing reactive UF membrane system will serve as a pioneering and comprehensive solution for the self-cleaning antifouling challenges encountered in UF membranes while also effectively mitigating the aging effects of reactive UF membranes.

Green Synthesis of Magnetic Adsorbent Using Groundwater Treatment Sludge for Tetracycline Adsorption

Groundwater treatment sludge is an industrial waste that is massively produced from groundwater treatment plants.Conventional methods for treatment of this sludge,such as discharge into deep wells or the sea,or disposal at landfills,are not environmentally sustainable.Here,we demonstrate an alternative strategy to recycle the sludge by preparing a magnetic maghemite adsorbent via a one-step hydrothermal method with NaOH solution as the only solvent.With this method,the weakly magnetized sludge,which contained 33.2%iron(Fe)and other impurities(e.g.,silicon(Si),aluminum(Al),and manganese(Mn)),was converted to magnetic adsorbent(MA)with the dissolution of Si/Al oxides(e.g.,quartz and albite)into the liquid fraction.At a NaOH concentration of 2 mol L^-1,approximately 18.1%of the ferrihydrite in the Fe oxides of the sludge was converted into 11.2%maghemite and 6.9%hematite after the hydrothermal treatment.MA2(i.e.,MA produced by a 2 mol L^-1 NaOH concentration)exhibited a good magnetic response of 8.2 emu g^-1(1 emu=10^-3 A m^2),and a desirable surface site concentration of 0.75 mmol g^-1.The synthesized MA2 was used to adsorb the cationic pollutant tetracycline(TC).The adsorption kinetics of TC onto MA2 fitted well with a pseudo-second-order model,and the adsorption isotherms complied well with the Langmuir model.The maximum adsorption capacity of MA2 for TC was 362.3 mg g^-1,and the main mechanism for TC adsorption was cationic exchange.This study is the first to demonstrate the preparation of an MA from recycled sludge without a reductant and/or exogenous Fe source.The prepared adsorbent can be used as a low-cost adsorbent with high capacity for TC sorption in the treatment of TC-containing wastewater.

Recycling of Mud Derived from Backwash Wastewater Coagulation as Magnetic Sodalite Sphere for Zn^(2+) Adsorption

Herein,we reported a method to prepare magnetic sodalite sphere by using the mud from backwash wastewater after polyaluminum chloride(PAC)coagulation.The results showed that approximately 100%of Fe in the wastewater was precipitated as flocculent iron mud(FM)by adding PAC.FM was converted to spherical magnetic sodalite(FMP)with a diameter of 3μm via a facile alkali hydrothermal method without adding Al/Si resources or reductant.The product FMP had the saturated magnetization of 10.9 emu g^(-1) and high Zn^(2+)adsorption capacity of 50.6 mg g^(-1).Without coagulation with PAC,the removal rate of Fe from the wastewater was only 92.7%,and the precipitated mud(RM)was converted to irregular particles(RMP),which had weak magnetic response and low capacity of Zn^(2+)adsorption comparing with FMP.With the method,the Fe in backwash wastewater was effectively recycled,and the generated sludge was converted to well-formed sodalite sphere without generating any secondary waste.

Current status of municipal wastewater treatment plants in North-east China:implications for reforming and upgrading

Climate affects the natural landscape,the economic productivity of societies,and the lifestyles of its inhabitants.It also influences municipal wastewater treatment.Biological processes are widely employed in municipal wastewater treatment plants(WWTPs),and the prolonged cold conditions brought by the winter months each year pose obstacles to meeting the national standards in relatively cold regions.Therefore,both a systematic analysis of existing technical bottlenecks as well as promising novel technologies are urgently needed for these cold regions.Taking North-east China as a case,this review studied and analyzed the main challenges affecting 20 municipal WWTPs.Moreover,we outlined the currently employed strategies and research issues pertaining to low temperature conditions.Low temperatures have been found to reduce the metabolism of microbes by 58%or more,thereby leading to chemical oxygen demand(COD)and NH_(4)^(-)-N levels that have frequently exceeded the national standard during the winter months.Furthermore,the extracellular matrix tends to lead to activated sludge bulking issues.Widely employed strategies to combat these issues include increasing the aeration intensity,reflux volume,and flocculant addition;however,these strategies increase electricity consumption by>42%in the winter months.Internationally,the processes of anaerobic ammonium oxidation(anammox),granular sludge,and aerobic denitrification have become the focus of research for overcoming low temperature.These have inspired us to review and propose directions for the further development of novel technologies suitable for cold regions,thereby overcoming the issues inherent in traditional processes that have failed to meet the presently reformed WWTP requirements.

Effects of surfactants on graphene oxide nanoparticles transport in saturated porous media

Transport behaviors of graphene oxide nanoparticles（GONPs） in saturated porous media were examined as a function of the presence and concentration of anionic surfactant（SDBS）and non-ionic surfactant（Triton X-100） under different ionic strength（IS）. The results showed that the GONPs were retained obviously in the sand columns at both IS of 50 and200 mmol/L, and they were more mobile at lower IS. The presence and concentration of surfactants could enhance the GONP transport, particularly as observed at higher IS. It was interesting to see that the GONP transport was surfactant type dependent, and SDBS was more effective to facilitate GONP transport than Triton X-100 in our experimental conditions. The advection–dispersion–retention numerical modeling followed this trend and depicted the difference quantitatively. Derjaguin–Landau–Verwey–Overbeek（DLVO）interaction calculations also were performed to interpret these effects, indicating that secondary minimum deposition was critical in this study.

Tracking Cryptosporidium in urban wastewater treatment plants in a cold region:Occurrence,species and infectivity

This study investigated the occurrence,species,infectivity and removal efficiency of Cryptosporidium spp.across typical wastewater treatment train.Samples from different process units were collected seasonally and synchronously from four wastewater treatment plants(WWTPs)in Northeastern China.Live Cryptosporidium oocysts were identified in most samples from both influent(97.50%)and effluent(90.00%)wastewaters of the four WWTPs,at an average density of 26.34 and 4.15 oocysts/L,respectively.The overall removal efficiency was 84.25%,and oocysts were mainly removed(62.01%)by the modified secondary sedimentation process.Ten Cryptosporidium species were identified in the effluent samples.C.andersoni,C.bovis,and C.ryanae were the three most prevalent species.Oocyst viability assays indicated no reduction of excystation rate during the primary and secondary wastewater treatments(varied in the range of 63.08%–68.50%),but the excystation rate declined to 52.21%in the effluent after disinfection.Notably,the Cryptosporidium oocysts showed higher infection intensity in the cold season(winter and spring)than that in summer and autumn.The influences of environmental temperature on virulence factors of Cryptosporidium were further examined.It was observed that more extracellular secretory proteins were bound on the oocyst surface and several virulence genes were expressed relatively strongly at low temperatures,both of which could facilitate oocyst adhesion,invasion,and host immune evasion.This research is of considerable interest since it serves as an important step towards more accurate panoramic recognition of Cryptosporidium risk reduction in WWTPs,and especially highlights the potential health risk associated with Cryptosporidium in cold regions/seasons.

Transport of bacterial cell(E,coli)from different recharge water resources in porous media during simulated artificial groundwater recharge

Commonly used recharge water resources for artificial groundwater recharge(AGR)such as secondary effluent(SE),river water and rainfall,are all oligotrophic,with low ionic strengths and different cationic compositions.The dwelling process in recharge pond imposed physiologic stress on Escherichia coli(E.coli)cells,in all three types of investigated recharge water resources and the cultivation of E.coli under varying recharge water conditions,induced changes in cell properties.During adaptation to the recharge water environment,the zeta potential of cells became more negative,the hydrodynamic diameters,extracellular polymeric substances content and surface hydrophobicity decreased,while the cellular outer membrane protein profiles became more diverse.The mobility of cells altered in accordance with changes in these cell properties.The E.coli cells in rainfall recharge water displayed the highest mobility(least retention),followed by cells in river water and finally SE cells,which had the lowest mobility.Simulated column experiments and quantitative modeling confirmed that the cellular properties,driven by the physiologic state of cells in different recharge water matrices and the solution chemistry,exerted synergistic effects on cell transport behavior.The findings of this study contribute to an improved understanding of E.coli transport in actual AGR scenarios and prediction of spreading risk in different recharge water sources.

Effective enrichment of Zn from smelting wastewater via an integrated Fe coagulation and hematite precipitation method

Coagulation is commonly applied to treat Zn-bearing wastewater from smelting industries(smelting wastewater),and thus the Zn-bearing sludge was considerably produced,which should be solidified before safety disposal.Herein,we demonstrated a novel approach to recycle Zn effectively from smelting wastewater via an integrated Fe coagulation and hematite precipitation method.First,smelting wastewater was coagulated by adding ferric chloride to generate Fe/Zn-bearing sludge(sludge for short).Secondly,the sludge was dissolved to generate an acid solution containing 2.2 g/L of Zn and 39.2 g/L of Fe.Thirdly,the Fe/Zn-bearing solution was hydrothermally treated,and 89%of Fe was eliminated to highly purified hematite block,whereas the percentage of Zn lost was below 1.1%.Finally,the hematite precipitates were collected,and the supernatant was hydrothermally treated again with the addition of glucose.When the molar ratio of glucose to Fe in the supernatant was 1.5,over 99.5%of Fe was precipitated in hematite nanoparticles with a diameter of 10-100 nm,and the residual Fe was 21.5 mg/L.The loss of Zn was below 0.4%,and the residual Zn in the solution was 2169 mg/L,290 times of that in the smelting wastewater.The major mechanism for Fe removal was the hydrolysis of ferric nitrate into hematite,which was promoted by nitrate consumption in glucose oxidation.This paper is the first report of an environment-friendly method for enriching Zn without generating any waste.