A critical review of environmental and public health impacts from the activities of evaporation ponds

Photothermal self-floating aerogels based on chitosan functionalized with polydopamine and carbon nanotubes for removal of arsenic from wastewater

Although wastewater disposal in evaporation ponds may be a cost-effective strategy for wastewater management, it overlooks water recycling and can possibly pose significant threats to the surrounding environment. The development of photothermal materials with functional groups capable of adsorbing toxic contaminants offers a promising opportunity for detoxification and potentially solar-driven recycling of wastewater disposed in evaporation ponds. In this study, ultralight aerogels based on chitosan (Ch), a natural biodegradable polymer, functionalized with mussel-inspired polydopamine (PDA) and carbon nanotubes (CNT) were fabricated through a facile approach and examined for the removal of arsenic from water. Three aerogels, namely chitosan, CNT/Ch, and PDA@CNT/Ch were fabricated and characterized using SEM, FTIR, TGA, XPS, and BET surface area analysis. Adsorption isotherms, thermodynamics, and kinetics were systematically investigated, revealing the feasibility of the fabricated aerogels for arsenic removal from aqueous solutions. The UV-Vis and photothermal analysis indicated excellent light-absorption and light-to-heat conversion performance of the functionalized aerogels. Arsenic adsorption by aerogels occurred rapidly and reached equilibrium within 30 to 60 min and was well-fitted by pseudo second-order kinetics model. The Langmuir model well described the adsorption isotherm, and the maximum adsorption capacities were found to be 31.5, 36.6, and 38.7 mg/g at neutral pH for chitosan, CNT/Ch, and PDA@CNT/Ch, respectively. The adsorption mechanism was studied by FTIR and XPS analysis and the adsorption pathway was evaluated using intraparticle diffusion model. This study broadens the scope of utilizing aerogels for the detoxification and potential recycling of wastewater from diverse sources and effluents disposed in evaporation ponds.

The Future of Municipal Wastewater Reuse Concentrate Management: Drivers, Challenges, and Opportunities

Water reuse is rapidly becoming an integral feature of resilient water systems, where municipal wastewater undergoes advanced treatment, typically involving a sequence of ultrafiltration (UF), reverse osmosis (RO), and an advanced oxidation process (AOP). When RO is used, a concentrated waste stream is produced that is elevated in not only total dissolved solids but also metals, nutrients, and micropollutants that have passed through conventional wastewater treatment. Management of this RO concentrate─dubbed municipal wastewater reuse concentrate (MWRC)─will be critical to address, especially as water reuse practices become more widespread. Building on existing brine management practices, this review explores MWRC management options by identifying infrastructural needs and opportunities for multi-beneficial disposal. To safeguard environmental systems from the potential hazards of MWRC, disposal, monitoring, and regulatory techniques are discussed to promote the safety and affordability of implementing MWRC management. Furthermore, opportunities for resource recovery and valorization are differentiated, while economic techniques to revamp cost-benefit analysis for MWRC management are examined. The goal of this critical review is to create a common foundation for researchers, practitioners, and regulators by providing an interdisciplinary set of tools and frameworks to address the impending challenges and emerging opportunities of MWRC management.

Leachate management in medium- and small-sized sanitary landfills: a Greek case study

The sustainable management of landfill leachates remains a matter of important concern in many countries. We used as case study a medium-sized Greek landfill, and we initially investigated the performance of the existing secondary leachate treatment system. The activated sludge process removed chemical oxygen demand (COD), biochemical oxygen demand (BOD), NH4-N, and PO4-P by 55%, 84%, 94%, and 14%, respectively, but the effluents did not meet the legislation requirements for discharge or reuse. Afterwards, different management options of these effluents (co-treatment with sewage in the centralized treatment plant, onsite tertiary treatment with reverse osmosis, granular activated carbon (GAC), ozonation, photo-Fenton, or constructed wetlands) were evaluated regarding their operational costs and environmental footprint. The use of constructed wetlands presented the lower operational cost, energy requirements, and greenhouse gas (GHG) emissions, not exceeding 21.5 kg CO2eq/day. On the other hand, the power consumption and the GHG emissions of the other on-site technologies ranged from 0.37 kWh/m3 and 5.56 kg CO2eq/day (use of GAC) to 39.19 kWh/m3 and 588.6 kg CO2eq/day (use of ozonation), respectively. The co-treatment of the leachates with municipal wastewater required 0.6 kWh/m3 and emitted 30.18 kg CO2eq/day. For achieving zero-discharge of the treated leachates, a system consisting of constructed wetlands and evaporation ponds in series was designed.

Effect of TiO2 on Pd/La2O3-CeO2-Al2O3 Systems during Catalytic Oxidation of Methane in the Presence of H2O and SO2

New results on the effect of TiO2 on Pd/La2O3-CeO2-Al2O3 systems for catalytic oxidation of methane in the presence of H2O and SO2 have been received. Low-temperature N2-adsorption, XRD, SEM, HRTEM, XPS, EPR and FTIR techniques were used to characterize the catalyst. The presence of Ce3+ on the catalytic surface and in the volume near the lantana was revealed by EPR and XPS. After aging, the following changes are observed: (i) agglomeration of the Pd-clusters (from 8 nm to 12 nm); (ii) transformation of part of the TiO2 from anatase to larger particles of rutile; and (iii)-the increase in PdO/Pd-ratio above its optimum. The modification by Ti of the La2O3-CeO2-Al2O3 system leads to higher resistance towards the presence of SO2 most likely due to the prevailing formation of unstable surface sulfites instead of thermally stable sulfates. Based on kinetic model calculations, the reaction pathway over the Pd/La2O3-CeO2-TiO2-Al2O3 catalyst follows the Mars-van Krevelen mechanism. For evaluation of the possible practical application of the obtained material, a sample of Pd/La2O3-CeO2-TiO2-Al2O3, supported on rolled aluminum-containing stainless steel (Aluchrom VDM®), was prepared and tested. Methane oxidation in an industrial-scale monolithic reactor was simulated using a two-dimensional heterogeneous reactor model.

Groundwater Quality and Health: Making the Invisible Visible

Linking groundwater quality to health will make the invisible groundwater visible, but there are knowledge gaps to understand the linkage which requires cross-disciplinary convergent research. The substances in groundwater that are critical to health can be classified into five types according to the sources and characteristics: geogenic substances, biogenic elements, anthropogenic contaminants, emerging contaminants, and pathogens. The most intriguing questions are related to quantitative assessment of human health and ecological risks of exposure to the critical substances via natural or induced artificial groundwater discharge: What is the list of critical substances released from discharging groundwater, and what are the pathways of the receptors' exposure to the critical substances? How to quantify the flux of critical substances during groundwater discharge? What procedures can we follow to assess human health and ecological risks of groundwater discharge? Answering these questions is fundamental for humans to deal with the challenges of water security and health risks related to groundwater quality. This perspective provides recent progresses, knowledge gaps, and future trends in understanding the linkage between groundwater quality and health.

Evaluation of oral and dermal health risk exposures of contaminants in groundwater resources for nine age groups in two densely populated districts, Nigeria

Human health and the sustainability of the socioeconomic system are directly related to water quality. As anthropogenic activity becomes more intense, pollutants, particularly potentially harmful elements (PHEs), penetrate water systems and degrade water quality. The purpose of this study was to evaluate the safety of using groundwater for domestic and drinking purposes through oral and dermal exposure routes, as well as the potential health risks posed to humans in the Nnewi and Awka regions of Nigeria. The research involved the application of a combination of the National Sanitation Foundation Water Quality Index (NSFWQI), HERisk code, and hierarchical dendrograms. Additionally, we utilized the regulatory guidelines established by the World Health Organization and the Standard Organization of Nigeria to compare the elemental compositions of the samples. The physicochemical parameters and NSFWQI evaluation revealed that the majority of the samples were PHE-polluted. Based on the HERisk code, it was discovered that in both the Nnewi and Awka regions, risk levels are higher for people aged 1 to <11 and >65 than for people aged 16 to <65. Overall, it was shown that all age categories appeared to be more vulnerable to risks due to the consumption than absorption of PHEs, with Cd > Pb > Cu > Fe for Nnewi and Pb > Cd > Cu > Fe for water samples from Awka. Summarily, groups of middle age are less susceptible to possible health issues than children and elderly individuals. Hierarchical dendrograms and correlation analysis showed the spatio-temporal implications of the drinking groundwater quality and human health risks in the area. This research could help local government agencies make informed decisions on how to effectively safeguard the groundwater environment while also utilizing the groundwater resources sustainably.

The Differential Antagonistic Ability of Curcumin against Cytotoxicity and Genotoxicity Induced by Distinct Heavy Metals

Widespread heavy metal pollution has aroused severe health risks worldwide. Curcumin has been reported to play a wide-spectrum protective role for various heavy metals. However, the specificity and difference in the antagonistic ability of curcumin against distinct types of heavy metals are still largely unknown. Here, using cadmium (Cd), arsenic (As), lead (Pb), and nickel (Ni) as the typical heavy metals, we systematically compared the detoxification efficiency of curcumin on the cytotoxicity and genotoxicity elicited by different heavy metals under the same experimental conditions. Curcumin was proved to have a significant discrepant antagonistic capacity when counteracting the adverse effect of different heavy metals. Stronger protective effects of curcumin emerged when antagonizing the toxicity of Cd and As, rather than Pb and Ni. Curcumin exhibits a better detoxification ability against heavy metal-induced genotoxicity than cytotoxicity. Mechanistically, inhibiting the oxidative stress elicited by heavy metals and reducing the bioaccumulation of metal ions both contributed to the detoxification of curcumin against all the tested heavy metals. Our results illustrated that curcumin shows prominent detoxification specificity against different types of heavy metals and toxic endpoints, which provides a new clue for the better and targeted application of curcumin in heavy metal detoxification.

A review on multi-synergistic transition metal oxide systems towards arsenic treatment: Near molecular analysis of surface-complexation (synchrotron studies/modeling tools)

The science and interface chemistry between the arsenic (As) anions and the different adsorbent systems have been gaining interest in recent years in environmental remediation applications. Metal-oxides and the corresponding hybrid systems have shown promising performance as novel adsorbents in various treatment technologies. The abundance, surface chemistry, high surface area (active-centres), various synthesis and functionalization methodologies, and good recyclability make these metal oxide-based nanomaterials as potential remediating agents for As oxyanions. This work critically reviews eight different platforms focused on the arsenic contamination issue, where the first classification describes the origin of arsenic contamination and presents geographical and demo-graphical considerations. The following section briefs the state-of-the-art remediation techniques for arsenic treatment with a comparative evaluation. An emphasized discussion has been provided regarding the adsorption and classification of various metal oxide adsorbents. In the next classification, various multi-synergism abilities like Redox activity, Surface functional groups, Surface area/morphology, Heterogeneous catalysis, Reactive oxygen species, Photo-catalytic/electro-catalytic reactions, and Electrosorption are detailed. The classification of various characterization tools for accessing the arsenic remediation qualitatively and quantitatively are given in the fifth chapter. The first-of-its-kind dedicated analysis has been given on the surface complexation aspects of the arsenic speciation onto various metal adsorbent systems using synchrotron results, surface-complexation modeling, and molecular simulation (e.g., DFT) in the sixth chapter. The current sensing applications of these novel nano-material systems for arsenic determination using colorimetric and electrochemical-based analytical tools and a note about the economic parameters, i.e., regeneration aspects of various adsorbent systems/the sustainable applications of the treated sludge materials, are provided in the final sections. This work makes a critical analysis of 'Environmental Nanotechnology' towards 'Arsenic Treatment'.