Environmental Science: Water Research & Technology最新文献

The efficient management of municipal sewage sludge (MSS) daily produced worldwide by biological wastewater treatment processes is nowadays of utmost importance. Classic treatment/disposal methods are affected by efficiency and/or safety issues. Innovative thermochemical treatments are gaining momentum as promising alternatives. Pyrolysis of MSS can result in the recovery of precious resources, such as nutrients and organic matter, and their conversion into three valuable fractions, i.e. biochar, bio-oil, and pyrolysis gas. These products are employable in innovative biorefinery pathways towards a wide range of value-added materials. In this review, an integrated biorefinery platform for MSS valorization is presented. After a brief introduction on MSS properties and issues related to its management, a deep focus on the influence that the feedstock and pyrolysis conditions have on the product yields and composition was conducted. Innovative valorization routes for biochar, bio-oil and pyrolysis gas were extensively discussed by highlighting challenges, opportunities, advantages and drawbacks. The characteristics required by these products to be efficiently valorized, as well as the main solution for their enhancement, were described. Additionally, economic considerations on MSS pyrolysis derived from full-scale applications conducted at the European and global level were elaborated. Finally, future perspectives about biochar, bio-oil and pyrolysis gas employment in cutting-edge upcycling routes have been reported.

The rational design of semiconductor photocatalysts with multi-dimensional nanostructures is an effective way to solve the problem of water environmental pollution. Herein, a series of ZnIn₂S₄/MgAl-LDH (ZIS/LDH) composites with core–shell nanostructures were synthesized by in situ growth of 2D ZnIn₂S₄ nanosheets on hexagonal LDH sheets. The obtained ZIS/LDH composite exhibited enhanced photocatalytic performance with 100% degradation efficiency for methyl orange (MO) within 20 min illumination, which was mainly attributed to the heterostructure formed by the excellent interface contact of the nanostructures, thereby inhibiting the recombination of photogenerated charges. Additionally, the as-synthesized photocatalyst shows satisfactory photocatalytic activity in stability tests and removal experiments for various dye pollutants. The present work provides novel insight into the design of heterojunction photocatalysts with multidimensional nanostructures and environmentally friendly applications.

The sewage denitrification process is concerned mainly with the treatment of industrial water with high NH₄⁺–N (>500 mg N L⁻¹). In this work, the denitrification effect of hybrid carrier (a natural polymer gel and an organic synthetic polymer)-embedded anammox bacteria pellets to treat NH₄⁺–N urban sewage wastewater at low temperature through batch and continuous tests was studied. After 99 days of operation in a UASB reactor, the rapid start-up of anammox was realized. The TN volumetric load grew gradually as the influent substrate concentration increased. The final influent water had an NH₄⁺–N load of 300 mg L⁻¹, an HRT of 5 h, a temperature of 32 °C, and NH₄⁺–N and nitrite nitrogen removal efficiencies above 85%. Batch tests for polyvinyl alcohol, polyvinyl alcohol–sodium alginate and polyvinyl alcohol–sodium bicarbonate pellets were performed. The optimized pellets performed exceptionally well in terms of mass transfer, elasticity, and mechanical strength. Embedded carrier materials are enhanced by added sodium alginate, silica powder, CaCO₃ powder and iron powder. A device containing embedded anammox bacteria pellets (EABP) was more resistant to low-temperature stress throughout the process of gradually cooling and lowering NH₄⁺–N than a device containing mature free sludge. In the analysis and strengthening test of EABP at 15 °C, NH₄⁺–N removal increased from 59% to 99%. At an HRT of 10 h, the increase in rate reached 67.8%. Compared to unembedded anammox bacteria pellets, the PS/PN of embedded pellets was lower, and the sludge activity and settleability were improved. Increasing HRT improved the ability of the embedded bacteria to withstand low temperatures, stimulating bacterial strains to produce more EPS. This study can be used to build a test to simulate future engineering applications in protecting the freshwater environment from the potential deleterious effects of pollutants from untreated sewage wastewater under low-temperature conditions and ammonium concentrations.

The management of water quality in distribution systems is a pervasive challenge. A high degree of uncertainty in water demand, reaction rates, and conditions of the pipe networks results in significant discrepancies between expected and observed water quality. In an effort to enhance the prediction of chlorine residual within water distribution systems (WDS), this study utilized full-scale WDS data to investigate the capabilities of a hydraulic model EPANET-Water Network Tool for Resilience (WNTR) coupled with process-based chlorine residual and data-driven models. Calculation and analysis of observed chlorine decay rates over 19 weeks of recorded data from a full-scale WDS (n = 19 512) demonstrated significant non-linearities and complex relationships with operational parameters and water quality. Linear regression was applied as a baseline method to model the relationship between water quality parameters and chlorine residual, but its limitations in capturing complex, non-linear interactions prompted a transition towards more sophisticated neural network architectures. Furthermore, EPANET-WNTR coupled with a first-order chlorine residual model showed poor performance in predicting chlorine residuals at a downstream node over the full range of flow conditions with high-frequency. Utilizing a windowing technique to account for sequences representing significant travel times in the dataset, the shift to neural networks, including convolutional neural networks (CNN) and long short-term memory (LSTM) networks demonstrated a significantly enhanced ability to incorporate temporal information and predict chlorine residual. The models achieved mean absolute errors as low as 0.022 mg L⁻¹ and R² as high as 0.952 using a 4-layer LSTM. This research illustrates the effectiveness of adopting data-driven approaches that can capture the relationships and dynamics of water quality parameters based on previous data, marking a significant advancement in water quality management within WDS.

Shale gas fracturing wastewater (FW) exhibits high total dissolved solids (TDS) content, averaging 13 g L⁻¹, along with an average total suspended solids (TSS) content of 676 mg L⁻¹ and an average chemical oxygen demand (COD) content of 1370 mg L⁻¹. Chemical coagulation processes are effective in removing suspended solids but perform poorly in removing organic contaminants. Consequently, the electrocoagulation (EC) process was employed to enhance the COD removal efficiency from shale gas FW. The EC process performance was assessed by examining various operational parameters such as pretreatment methods, current density levels, pH values, and reaction times. It was found that chemical coagulation achieved a COD removal efficiency of 43.1% at a dosage of 500 mg L⁻¹. Compared to chemical coagulants at the same concentration, the EC process demonstrated a higher COD removal efficiency and was nearly one-fifth of the cost. When the FW samples were treated directly by the EC process, the optimal COD removal efficiency of up to 85% was achieved under the conditions of 70 A m⁻² current density, a pH of 7, and a reaction time of 20 minutes. However, after aeration pretreatment for 30 minutes, the optimum removal efficiency of 88.3% occurred at a current density of 50 A m⁻² and a reaction time of 15 minutes. The pseudo first-order model was found to be more suitable for simulating both COD and DOC removal in the EC process with significant coefficients (R² > 0.89). The results confirmed that the EC process combined with aeration pretreatment is an innovative alternative for real-scale shale gas FW treatment.

Crop irrigation with treated wastewater effluent using drip irrigation has become common as the demand for water supply has increased. Because of the quality characteristics of treated wastewater and the narrow and winding geometry of the drip emitter's structure, it is susceptible to clogging. Emitter clogging reduces flow and increases flow variability between emitters that can lead to water stress on crops, thereby reducing crop yield. Several methods to minimize emitter clogging have been suggested and applied; however many drawbacks are associated with them. The use of UV-LEDs (UV light-emitting diodes) is a non-chemical disinfection method that holds great promise for disinfection and biofouling prevention in irrigation systems. In this research, biofouling formation potential was investigated for 12 weeks, in a large pilot-scale irrigation rig consisting of three parallel pipelines, comparing three disinfection treatments: UV-LED, chlorine, and no treatment. The results indicate that the discharges of UV-LED and chlorine-treated lines were similar. However, analyzing the internal fouling material of the opened drippers revealed the significant advantage of the UV-LED treatment, when both OCT (optical coherence tomography) image processing and EPS (extracellular polymeric substance) secretion within the clogging substances indicated significant biofilm inhibition by UV-LED irradiation as compared to the other alternatives. The present study is a proof-of-concept of a new approach of using UV-LED irradiation for minimizing biofouling formation in emitters fed with treated wastewater. UV-LED technology has great potential to become an attractive and feasible alternative for replacing chlorine as a water disinfection technology, specifically for agriculture use.

Ceramic ultrafiltration membrane filtration has made great progress in water purification. In terms of operational stability, ceramic ultrafiltration membranes have more obvious advantages than polymer membranes. However, membrane fouling is still a key factor hindering the development of ceramic ultrafiltration membranes. In order to alleviate membrane fouling, relevant pretreatment methods have been paid more and more attention. With the in-depth study of the interaction between filtration and coagulation, oxidation, adsorption and other processes, the combination of different technologies to alleviate membrane fouling and improve water purification efficiency has been recognized. It is necessary to make a comprehensive review on the control of ceramic ultrafiltration membrane fouling by different pretreatment methods. In this paper, the latest progress in the mechanism of ceramic ultrafiltration membrane fouling control by different pretreatments is reviewed, and the effects of the combination of various pretreatment methods are discussed. This study can provide a reference for the development of ceramic ultrafiltration membranes in practical applications.

In this paper, biodiesel wastewater was treated by catalytic combustion in the case of catalyst coupling. The effects of reaction temperature, residence time and air flow on the treatment of biodiesel wastewater were investigated using the Fe₂O₃ catalyst, the Pt/Al₂O₃@cordierite catalyst and the Fe₂O₃ catalyst coupled with the Pt-based catalyst. The effects of high-temperature hydrothermal treatment on the two catalysts were evaluated. The catalytic stability was studied in continuous catalytic combustion. Detailed characterization of the two catalysts was carried out. The X-ray fluorescence (XRF), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) characterization demonstrated that the Fe₂O₃ catalyst contained a significant amount of surface active oxygen and Fe₂O₃ existed in an amorphous form within the catalyst. The Fe₂O₃ catalyst could remove 90.6% of sulfur from wastewater, showing excellent desulfurization performance, but it was not resistant to high temperature. After 500 °C hydrothermal treatment, the chemical oxygen demand (COD) removal rate decreased significantly from 97.98% to 69.04% at the reaction temperature of 280 °C. The COD removal rate of the Pt/Al₂O₃@cordierite catalyst was almost 100% at the reaction temperature of 320 °C, with the activity being basically unchanged after high-temperature hydrothermal treatment, but sulfur poisoning occurred. The Fe₂O₃ catalyst coupled with the Pt/Al₂O₃@cordierite catalyst showed excellent catalytic activity and stability, and the optimal reaction temperature and residence time were 320 °C and 0.3 s, respectively. In the continuous treatment of biodiesel wastewater with the COD of 99 465 mg L⁻¹ for 200 h, the COD and sulfur content of the treated wastewater were less than 400 mg L⁻¹ and 1 mg L⁻¹, with the COD removal rate and sulfur removal rate exceeding 99.62% and 81.38%, respectively. In addition, no organic gas or SO₂ was detected in the exhaust gas generated during the reaction, and the removed organic matter was converted into CO₂ and H₂O.

The contribution of individual bacterial strains within a mixed microbial community to the overall turnover of a specific compound is often assessed using qPCR data quantifying strain-specific 16S rRNA or functional genes. Here we compare the results of a qPCR based approach with those of compound specific stable isotope analysis (CSIA), which relies on strain-specific magnitudes of kinetic isotope fractionation associated with the biotransformation of a compound. To this end, we performed tetrachloroethylene (PCE) transformation experiments using a synthetic binary culture containing two different Desulfitobacterium strains (Desulfitobacterium hafniense strain Y51; ε_C,PCE = −5.8‰ and Desulfitobacterium dehalogenans strain PCE1; ε_C,PCE = −19.7‰). Cell abundances were analyzed via qPCR of functional genes and compared to strain-specific PCE turnover derived via carbon isotope fractionation. Repeated spiking of an initially strain Y51 dominated synthetic binary culture with PCE led to a steadily increasing contribution of strain PCE1 to PCE turnover (ε_C,initial = −5.6 ± 0.6‰ to ε_C,final = −18.0 ± 0.6‰) which was not or only weakly reflected in the changes of the cell abundances. The CSIA data further indicate that strain-specific PCE turnover varied by more than 75% at similar cell abundances of the two strains. Thus, the CSIA approach provided new and unexpected insights into the evolution of the metabolic activity of the single strains within a synthetic binary culture and indicates that strain-specific substrate turnover appears to be controlled by physiological and enzymatic properties of the strains rather than their cell abundance.

Harmful algal blooms (HABs) are an emerging threat to ecosystems, drinking water safety, and the recreational industry. As an environmental challenge intertwined with climate change and excessive nutrient discharge, HAB events occur more frequently and irregularly. This dilemma calls for fast-response treatment strategies. This study developed an electrochemical ozonation (ECO) process, which uses Ni–Sb–SnO₂ anodes to produce locally concentrated ozone (O₃) and hydroxyl radicals (·OH) to achieve ∼100% inactivation of cyanobacteria (indicated by chlorophyll-a degradation) and removal of microcystins within 120 seconds. More importantly, the proof-of-concept evolved into a full-scale boat-mounted completely mixed flow reactor for the treatment of HAB-impacted lake water. The single-pass treatment at a capacity of 544 m³ d⁻¹ achieved 62% chlorophyll-a removal with an energy consumption of <1 Wh L⁻¹. Byproducts (e.g., chlorate, bromate, trihalomethanes, and haloacetic acids) in the treated lake water were below the regulatory limits for drinking water. The whole effluent toxicity tests suggest that ECO treatment at 10 mA cm⁻² posed certain chronic toxicity to the model crustacean invertebrate (Ceriodaphnia dubia). However, the treatment at 7 mA cm⁻² (identified as the optimum condition) did not increase toxicity to model invertebrate and fish (Pimephales promelas) species. This study is a successful example of leveraging fundamental innovations in electrocatalysis to solve real-world problems.