Environmental Science: Water Research & Technology最新文献

In the biodesulfurisation process harmful sulfide is converted to sulfur by sulfide oxidising bacteria (SOB), using oxygen as terminal electron acceptor. Surprisingly, in this process sulfide is already removed before oxygen is consumed. Therefore, sulfide and/or charge is being shuttled between sulfide removal and terminal electron transfer. Previously, it was thought that the bacteria themselves were the exclusive "electron shuttlers". Patterns in sulfide concentration and oxygen reduction potential (ORP) during anaerobic sulfide removal tests in batch confirmed that SOB remove sulfide in two steps, of which the second lowered the ORP. However, we found that aside from biomass also biosulfur and certain solutes are involved in electron shuttling. Gradual removal of sulfide by interactions between sulfide, solutes, and biosulfur caused an increase in ORP, even after all sulfide was removed. The amplitude and rate of ORP increase rose with increasing sulfide removal capacity of the process solution. We hypothesise that organic thiol/disulfide redox couples are involved in electron shuttling.

This study evaluates the batch seeding of granular activated carbon (GAC) with sludge inocula and raw sewage to accelerate its transformation into biological activated carbon (BAC) and achieve rapid steady-state condition, fostering the development of microbial community and simultaneous degradation of residual organics, nitrogen, and emerging contaminants (ECs) from secondary effluents. After 7 days of seeding, pathogens dominated the surface of GAC while heterotrophs, nitrifiers, and denitrifiers were scarce. However, a sustained aerobic condition in the column shifted the community towards these beneficial microbes, enabling rapid biofilm development and attainment of steady-state conditions in the removal of dissolved organic carbon (DOC). Notably, two columns loaded with seeded GAC at food-to-microorganism (F/M) ratios of 0.8 and 0.4 reached steady-state after 4801 (50 days) and 7202 (75 days)-bed volumes (BVs), respectively, while the control required 19 206 (200 days) BVs. The seeded systems showed a higher reduction in the DOC, decreasing from 6.4 to 2 mg L⁻¹ (∼68%), meeting the USEPA DOC recommendation for drinking water. Other studies reported <50% reduction in the DOC after operating for 200 days. Additionally, NH₄-N and NO₃-N were lowered from 1.6 to 0.5 mg L⁻¹ and 5.2 to 2.6 mg L⁻¹, respectively. At a contact time of 15 min, 12 out of 17 ECs showed >70% removal, while the remaining 5 ECs showed >60% removal. A fluorescence–PARAFAC model was used to investigate the DOC removal mechanism by the BAC filters. These filters effectively reduced the total coliforms by >1.5 log₁₀ and strengthened the relationship between the functional enzymes, key metabolic pathways, and contaminant removal. Extracellular polymeric substances (EPS) from BAC were characterized to provide mechanistic insights into the enhanced attenuation of ECs.

Water pollution is a significant environmental concern that necessitates the development of effective treatment techniques to mitigate the adverse impacts of water pollution on human health and ecosystems. To effectively tackle the water pollution caused by dyes, pharmaceuticals and other organic pollutants, researchers are continuously developing new technologies for wastewater treatment. This review offers a complete understanding of the fundamental principles of Photoelectrocatalytic (PEC) degradation, design strategies for photocatalysts and reactors, mechanism for the formation of reactive species, and mechanism for the degradation of target pollutants. The strategies for enhancing the performance of photoelectrocatalyts, such as doping, heterojunction formation, and morphology control, are discussed. Additionally, this review addresses the toxicity assessment of treated effluents and discusses the current challenges, including inferior material stability, limited visible-light absorption, and impediments in large-scale implementation. Finally, the factors influencing the PEC degradation of dyes and pharmaceuticals are discussed. This review will provide a roadmap for environmental researchers working in water sustainability departments to effectively design and develop new photoelectrodes and photoelectrocatalytic reactors (PECRs) to efficiently tackle water pollution.

To improve the performance of sludge pressure filtration and achieve deep dewatering, this study compared the effects of three biochar skeleton materials derived from different sources—anaerobic sludge biochar, surplus sludge biochar, and rice husk biochar—on sludge conditioning. The enhancement mechanisms were systematically investigated by analyzing changes in particle size distribution, zeta potential, and the contents of polysaccharides and proteins in extracellular polymeric substances (EPS). Experimental results showed that the addition of biochar skeletons significantly improved sludge dewatering efficiency, with anaerobic sludge biochar reducing the sludge cake moisture content to 63.98% ± 0.54% at a dosage of 50% (on a dry sludge basis). Mechanism analysis indicated that biochar skeletons neutralized surface charges, increased particle size, and adsorbed hydrophilic EPS components to promote floc formation. These effects further facilitated the construction of mechanically stable skeleton structures and stratified drainage channels, which helped maintain sludge cake permeability under high pressure, enhance filtration performance, and ultimately achieve deep dewatering. This study provides important theoretical foundations and engineering support for the development of novel sludge conditioners and the optimization of deep dewatering processes.

This study assessed the effectiveness of microfiltration (MF) as pretreatment combined with nanofiltration (NF) for tertiary treatment of secondary wastewater effluent (SWE) from a facultative lagoon system. The SWE was found to have turbidity levels which require pretreatment, and microfiltration was chosen in this study for its ability to remove particles to 1 micron, its low-cost and the ease of operation and maintenance. Three commercially available NF membranes (NF90, NF245, and NF270) were evaluated using a bench-scale system operated in recycle mode, in which a fixed batch volume of SWE obtained from Tuba City, Arizona, was continuously recirculated through each membrane module. The NF90 membrane demonstrated the highest rejection of organic and inorganic compounds and consistently maintained a 96% reduction in total dissolved solids throughout 7 days of operation. In contrast, the NF245 and NF270 membranes showed decreasing performance over time due to fouling. All membranes successfully removed more than 95% of contaminants of emerging concern. Characterization of the membranes indicated changes in hydrophobicity and surface charge for NF245 and NF270 after SWE filtering, while the properties of the NF90 membrane surface remained relatively unchanged. The treated effluents from NF245 and NF270 met Arizona's Class A+ reclaimed water standards for non-potable reuse. This study illustrates the potential of MF–NF treatment to upgrade facultative lagoon effluents to satisfy water reuse standards and to offer a sustainable solution for small communities experiencing water scarcity.

Disinfection of water by chlorine is of paramount importance to public health, while higher than regulated concentrations are toxicologically dangerous and must be controlled with great accuracy in real-time. In the present study, we introduce an ultra-green fluorimetric sensor based on carbon dots (C-dots), synthesized for the first time from waste mango endocarp, for the quantification of free chlorine. The biogenic C-dots synthesized show strong blue fluorescence that is selectively quenched by hypochlorite by an oxidation-mediated process. The structural and surface characteristics of the synthesized C-dots were extensively characterized using UV-vis spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and dynamic light scattering analysis (DLS) to measure size and zeta potential. To render monitoring field-deployable, the system is applied using a low-cost, Arduino-powered portable device with a UV source and RGB sensor for real-time, reagent-free chlorine detection in pool water. The method has a wide range of linearity (0.01–100 ppm), good detection limit (3.0 ppb), and selectivity. The method's sustainability was confirmed through ComplexMoGAPI, BAGI, and RGB 12 tools. The present work synergistically combines food waste valorization, nanotechnology, and embedded systems into a smart, sustainable platform for water quality management.

Livestock and poultry wastewater is one of the main sources of antibiotic pollution, but compared with the high concentration of COD, turbidity and other pollution indicators, the changes of trace pollutant antibiotics are often ignored in the treatment of livestock and poultry wastewater. There are few studies on the removal efficiency of antibiotics and whether there is a change in substance structure during coagulation and precipitation as a commonly used livestock and poultry wastewater treatment process. The optimal removal conditions of tetracycline (TC) by flocculants FeCl₃, AlCl₃ and PAC were obtained by simulating the turbidity of actual livestock and poultry wastewater and providing a flocculant formation environment. Comparative analysis showed that FeCl₃ coagulant had the best adsorption efficiency for TC. The flocs formed by FeCl₃ coagulant adsorbed tetracycline to form dense particles, and the flocs of AlCl₃ and PAC coagulant formed a stacked network after adsorption. It is worth noting that the optimal efficiency may be caused by the change of reaction environment which is caused by the concentration ratio of coagulant aid (NaHCO₃) and coagulant, and TC is degraded by chemical reactions. In addition, not only adsorption in the process of removal of tetracycline by coagulation and precipitation, but also the morphological structure of tetracycline was changed which may be due to the oxidation of high-valence metal ions or the presence of hydroxyl metal ions and Cl⁻. This study found that in the traditional coagulation process with the main goal of removing turbidity and organic matter, the unexpected synergistic removal efficiency of trace antibiotic tetracycline is of great value. It can achieve the ‘multiple’ pollution control effect without changing the core process of the existing water treatment plant, which provides a scientific basis for reducing the environmental emission of antibiotics at low cost.

Effective wastewater treatment is critical for public health and environmental protection. In regional communities, where resources are limited, there is a need for sustainable and low-cost wastewater treatment solutions. Commonly used waste stabilisation ponds, have large land requirements, inconsistent treatment performance and high rates of evaporative water loss. High rate algal ponds (HRAPs) offer a smaller area footprint and consequentially reduced capital expenditure, enhanced treatment performance and a low maintenance alternative. HRAPs are commonly operated as continuously stirred tank reactors, at shallow depth (0.2–0.5 m) mixed by a paddlewheel. Effective wastewater treatment is then achieved by a consortium of naturally occurring, harmless microalgae and bacteria. However, there is a need to further improve their operation and the quality of the treated effluent to enhance water reuse opportunities and alleviate water insecurity concerns in rural communities. Here we uniquely propose two different operational strategies for HRAPs as the next step forward for this treatment technology. The two strategies require operation as sequencing batch reactors, which enables independent management, of hydraulic retention time and solids retention time, providing additional operational management strategies. Significantly, this offers the potential to develop influent feeding and mixing strategies to develop biofilm like assemblages of photogranules or to selectively enrich and maintain filamentous algal populations. The increased density of either photogranules or filamentous algae will enable efficient biosolids separation yielding an effluent low in suspended solids. The biomass separation may also be achieved within the HRAP avoiding the need to construct and manage additional infrastructure. The enhanced treated effluent quality increases opportunities for added value beneficial water reuse in climate change related water stressed communities. Future research is needed to validate this approach and the optimum operating conditions to achieve treatment and efficient in situ biomass separation.

Phosphorus (P) is an essential nutrient for the biological function of both animals and plants, as well as a main constituent of industrial products, including crop fertilizers, detergents, chemicals, pharmaceuticals, food and feed, and construction materials. In recent years, the imbalance between P mining and its excessive, inefficient use has led to resource depletion, runoff and water contamination. P contamination predominantly comes from agricultural, industrial, and domestic waste worldwide. The overabundance of P in water bodies has exacerbated eutrophication and related health problems, affecting aquatic life and posing risks to humans. To address global concerns about the depletion of phosphate rock (PR) reserves and alleviate associated environmental and health hazards, various physical, chemical, and biological methods are currently employed to remove and recover P from wastewater. Among these, adsorption, chemical precipitation, membrane filtration, the use of microorganisms, ion exchange, and crystallization are considered the most widely employed techniques. These conventional methods present several drawbacks, including strict control of operation, limited sensitivity to phosphate ions (PO₄³⁻) at low concentrations, high chemical and energy consumption, poor mechanical and chemical stability, limited scalability, and high costs. Recently, biopolymers, primarily polysaccharide-based technologies, have emerged as sustainable, eco-friendly, low-cost, and innovative alternatives for removing and recovering P from aqueous environments, addressing the prevailing challenges and gaps associated with conventional methods. Polysaccharides and their derivatives exhibit enhanced P removal efficiency, renewability, scalability, high mechanical and chemical strength, and non-toxicity. Although polysaccharides have been widely investigated for wastewater treatment, their involvement and mechanisms in P removal and recovery have not been systematically analyzed. Therefore, this study consolidates recent findings on polysaccharide-based materials, namely cellulose, chitosan, starch, and alginate, for the effective removal and recovery of P, filling an unaddressed area in the literature. The current review also provides a synopsis of current trends and future advancements in polysaccharide-based technologies for the removal and recovery of P. Furthermore, this review serves as a guide to the development of practical and sustainable waste and resource management systems for P, subsequently contributing to the circular bioeconomy.