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Removal of heavy metal ions from wastewater is of prime importance for a clean environment and human health. Different reported methods were devoted to heavy metal ions removal from various wastewater sources. These methods could be classified into adsorption-, membrane-, chemical-, electric-, and photocatalytic-based treatments. This paper comprehensively and critically reviews and discusses these methods in terms of used agents/adsorbents, removal efficiency, operating conditions, and the pros and cons of each method. Besides, the key findings of the previous studies reported in the literature are summarized. Generally, it is noticed that most of the recent studies have focused on adsorption techniques. The major obstacles of the adsorption methods are the ability to remove different ion types concurrently, high retention time, and cycling stability of adsorbents. Even though the chemical and membrane methods are practical, the large-volume sludge formation and post-treatment requirements are vital issues that need to be solved for chemical techniques. Fouling and scaling inhibition could lead to further improvement in membrane separation. However, pre-treatment and periodic cleaning of membranes incur additional costs. Electrical-based methods were also reported to be efficient; however, industrial-scale separation is needed in addition to tackling the issue of large-volume sludge formation. Electric- and photocatalytic-based methods are still less mature. More attention should be drawn to using real wastewaters rather than synthetic ones when investigating heavy metals removal. Future research studies should focus on eco-friendly, cost-effective, and sustainable materials and methods.

The 2018 edition of the United Nations World Water Development Report stated that nearly 6 billion peoples will suffer from clean water scarcity by 2050. This is the result of increasing demand for water, reduction of water resources, and increasing pollution of water, driven by dramatic population and economic growth. It is suggested that this number may be an underestimation, and scarcity of clean water by 2050 may be worse as the effects of the three drivers of water scarcity, as well as of unequal growth, accessibility and needs, are underrated. While the report promotes the spontaneous adoption of nature-based-solutions within an unconstrained population and economic expansion, there is an urgent need to regulate demography and economy, while enforcing clear rules to limit pollution, preserve aquifers and save water, equally applying everywhere. The aim of this paper is to highlight the inter-linkage in between population and economic growth and water demand, resources and pollution, that ultimately drive water scarcity, and the relevance of these aspects in local, rather than global, perspective, with a view to stimulating debate.

Recent advances in wastewater treatment processes have resulted in high removal efficiencies for various hazardous pollutants. Nevertheless, some technologies are more suitable for targeting specific contaminants than others. We comprehensively reviewed the recent advances in removing hazardous pollutants from industrial wastewater through membrane technologies, adsorption, Fenton-based processes, advanced oxidation processes (AOP), and hybrid systems such as electrically-enhanced membrane bioreactors (eMBRs), and integrated eMBR-adsorption system. Each technology’s key features are compared, and recent modifications to the conventional treatment approaches and limitations of advanced treatment systems are highlighted. The removal of emerging contaminants such as pharmaceuticals from wastewater is also discussed.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), known as the most detected per- and polyfluoroalkyl substances (PFAS) in various environmental compartments, have been associated with plastic pollution and endocrine dysfunction. Over the past 180 years (1839–2019), numerous emerging contaminants have been identified, with PFOA and PFOS receiving considerable attention based on scientific evidence and publications. Between 2018 and 2019, PFOA and PFOS experienced a relatively high increase rate of 18.8% and 13.6%, respectively. While developed countries have made progress in establishing stringent guidelines, developing and underdeveloped countries often lack regulations and mechanisms to address emerging PFAS. Furthermore, advancements in PFAS removal technologies are needed to improve their efficacy and feasibility. The establishment of regulatory compliances, along with exposure assessment and risk characterization, is essential for providing precautionary advice on water source protection, water supply security, health risks, treatment efficiency, and contamination forecasting. However, a more comprehensive approach and database for evaluating exposure and risks are still imperative to effectively combat PFAS contamination in drinking water. Therefore, this review aims to enhance environmental monitoring and management practices in response to the global crisis of PFAS contamination. The analysis of Needs, Approaches, Benefits, and Challenges (NABC) is grounded in the current trends of PFAS in the environment and human exposure through drinking water.

The chemical regeneration process has been extensively applied to reactivate biochar, supporting its reusability and leading to significant operating cost reduction. However, no recent review discusses the effectiveness of biochar chemical regeneration. Thus, this article comprehensively reviews the chemical regeneration of biochar contaminated with organic and inorganic pollutants. Performance of the chemical regeneration depends on adsorption mechanism, functional groups, adsorbent pore structure, and changes in active adsorbent sites. Secondary contamination is one of the challenges facing the sustainable adaptation of the chemical regeneration process in the industry. The paper discusses these challenges and draws a roadmap for future research to support sustainable wastewater treatment by biochar.

Water is of fundamental importance for life on earth. The synthesis and structure of cell constituents and transport of nutrients into the cells as well as body metabolism depend on water. The contaminations present in water disturb the spontaneity of the mechanism and result in long/short-term diseases. The probable contaminations and their possible routes are discussed in the present review. Continued research efforts result in some processes/technologies to remove the contaminations from water. The review includes concepts and potentialities of the technologies in a comprehensible form. It also includes some meaningful hybrid technologies and promising awaited technologies in coming years.

In recent years, rapid development in the industrial sector has offered console to the people but at the same time, generates numerous amounts of effluent composed of toxic elements like nitrogen, phosphorus, hydrocarbons, and heavy metals that influences the environment and mankind hazardously. While the technological advancements are made in industrial effluent treatment, there arising stretch in the techniques directing on hybrid system that are effective in resource recovery from effluent in an economical, less time consuming and viable manner. The key objective of this article is to study, propose and deliberate the process and products obtained from different industries and the quantity of effluents produced, and the most advanced and ultra-modern theoretical and scientific improvements in treatment methods to remove those dissolved matter and toxic substances and also the challenges and perspectives in these developments. The findings of this review appraise new eco-friendly technologies, provide intuition into the efficiency in contaminants removal and aids in interpreting degradation mechanism of toxic elements by various treatment assemblages.

Water resources are essential for every development activity, not only in terms of available quantity but also in terms of quality. Population growth and urbanisation are increasing the number of users and uses of water, making water resources scarcer and more polluted. Changes in rainfall patterns threaten to worsen these effects in many areas. Water scarcity, due to physical lack or pollution, has become one of the most pressing issues globally, a matter of human, economic and environmental insecurity. Wastewater, whose value had not been appreciated until recently, is increasingly recognised as a potential ‘new’ source of clean water for potable and non-potable uses, resulting in social, environmental and economic benefits. This paper discusses the potential of recycled wastewater (also known as reused water) to become a significant source of safe water for drinking purposes and improved sanitation in support of the Sustainable Development Goals.

Antibiotics are widely used in animal husbandry, and various types of antibiotic resistance genes (ARGs) are frequently detected in livestock waste around the world. Conventional livestock waste treatment processes do not completely remove ARGs, resulting in their release to soil and water environments. Various exposure routes of these ARGs to humans, including inhalation and ingestion of antibiotic-resistant bacteria (ARB) that harbor them, may be contributing to the rise in resistant clinical infections that are increasingly difficult to treat with antibiotics. In this review, we assess the occurrence and variability of ARGs in livestock wastes and their potential propagation pathways to human pathogens. We also review the mechanisms and environmental factors that influence the dissemination of ARGs through these pathways, and evaluate the ARG removal efficiency of common livestock waste management approaches. Challenges and research needs for assessing and mitigating the risk of antibiotic resistance dissemination from livestock waste are also presented.

Groundwater quality appraisal is one of the most crucial tasks to ensure safe drinking water sources. Concurrently, a water quality index (WQI) requires some water quality parameters. Conventionally, WQI computation consumes time and is often found with various errors during subindex calculation. To this end, 8 artificial intelligence algorithms, e.g., multilinear regression (MLR), random forest (RF), M5P tree (M5P), random subspace (RSS), additive regression (AR), artificial neural network (ANN), support vector regression (SVR), and locally weighted linear regression (LWLR), were employed to generate WQI prediction in Illizi region, southeast Algeria. Using the best subset regression, 12 different input combinations were developed and the strategy of work was based on two scenarios. The first scenario aims to reduce the time consumption in WQI computation, where all parameters were used as inputs. The second scenario intends to show the water quality variation in the critical cases when the necessary analyses are unavailable, whereas all inputs were reduced based on sensitivity analysis. The models were appraised using several statistical metrics including correlation coefficient (R), mean absolute error (MAE), root mean square error (RMSE), relative absolute error (RAE), and root relative square error (RRSE). The results reveal that TDS and TH are the key drivers influencing WQI in the study area. The comparison of performance evaluation metric shows that the MLR model has the higher accuracy compared to other models in the first scenario in terms of 1, 1.4572*10–08, 2.1418*10–08, 1.2573*10–10%, and 3.1708*10–08% for R, MAE, RMSE, RAE, and RRSE, respectively. The second scenario was executed with less error rate by using the RF model with 0.9984, 1.9942, 3.2488, 4.693, and 5.9642 for R, MAE, RMSE, RAE, and RRSE, respectively. The outcomes of this paper would be of interest to water planners in terms of WQI for improving sustainable management plans of groundwater resources.