Removal of ofloxacin from wastewater by chloride electrolyte electro-oxidation: Analysis of the role of active chlorine and operating costs

Molecular composition and formation mechanism of chlorinated organic compounds in biological waste leachate treated by electrochemical oxidation with a boron-doped diamond anode

The use of electrochemical oxidation with boron-doped diamond (BDD) as an anode has been demonstrated to be an effective means of removing dissolved organic matter (DOM) from biologically treated waste leachate. However, in the presence of chloride ions, undesired chlorine evolution occurs on the anode; this forms chlorinated DOM, mostly of unknown molecular composition. We investigate the molecular composition and formation mechanism of chlorinated DOM during electrochemical oxidation process of biologically treated leachate DOM. At a current density of 8 mA/cm2, after 120 min of electrolysis, 479 unknown chlorinated DOMs were detected in the treated effluent, comprising 21.55% of the total. The unknown species are dominated by oxygen-rich, highly unsaturated structures, and exhibit higher oxidation degrees, lower unsaturation, and lower aromaticity compared to the removed nonchlorinated DOM. An additional 43.63 mg/L of known chlorinated DOM species, predominantly dichloroacetic and trichloroacetic acids, also accumulate in the treated effluent. Introducing hydroxyl radicals (HO•) to the anode surface forms reactive chlorine species including chlorine radical (Cl•), dichlorine radical (Cl2•-), and hypochlorous acid/hypochlorite (HOCl/OCl-); the concentration of HOCl/OCl- reaches 529.2 mg/L. These species react with reduced and aromatic dissolved organic matter via reaction pathways such as chlorine substitution for hydrogen (Cl+H-) and the HOCl addition reaction (HO+Cl+) to generate unknown chlorinated DOM species; the known chlorinated DOM are formed afterward via ring opening and dealkylation pathways. Our results provide a theory for the prevention and control of chlorinated DOM during treatment of chlorine-laden organic wastewater by an electrochemical oxidation system with a boron-doped diamond anode.

Bioaerogels from biomass waste: An alternative sustainable approach for wastewater treatment

The generation of municipal solid waste is projected to increase from 2.1 billion tonnes in 2023 to 3.8 billion tonnes by 2050. In 2020, the direct global cost of managing this waste was approximately USD 252 billion. When considering additional hidden costs-such as those arising from pollution, adverse health effects, and climate change due to inadequate waste disposal-the total cost escalates to USD 361 billion. Without significant improvements in waste management practices, this figure could nearly double by 2050, reaching an estimated USD 640.3 billion annually. Among municipal solid waste, biowaste accounts for roughly 44 % of the global municipal solid waste, translating to about 840 million tonnes annually. They are widely accessible and economical, offering a cost-effective alternative to traditional treatment materials. Transforming biomass waste into carbon-based materials (e.g., bioaerogels) is a sustainable practice that reduces waste and repurposes it for environmental remediation. This approach not only decreases the volume of waste directed to landfills and mitigates harmful greenhouse gas emissions from decomposition but also aligns with the principles of a circular economy. Furthermore, it supports sustainable development goals by addressing issues such as water scarcity and pollution while promoting waste valorization and resource efficiency. The unique properties of bioaerogels-including their porosity, multi-layered structure, and chemical adaptability-make them highly effective for the remediation of different water pollutants from aquatic bodies. This review article comprehensively delves into multifaceted wastewater remediation strategies -based bioaerogels such as coagulation and flocculation, advanced oxidation processes, membrane filtration, catalytic processes, water disinfection, Oil-water separation, biodegradation, and adsorption. Additionally, it examines different mechanisms of interaction such as surface adsorption, electrostatic interaction, van der Waals forces, ion exchange, surface precipitation, complexation, pore-filling, hydrophobic interactions, and π-π stacking. Moreover, it conducts an integrated techno-economic evaluation to assess their feasibility in wastewater treatment. By valorizing biomass waste, a closed-loop system can be established, where waste is transformed into valuable bioaerogels. This approach not only addresses challenges related to effluent pollution but also generates economic, environmental, and social benefits. Ultimately, the review underscores the transformative potential of bioaerogels in wastewater treatment, emphasizing their crucial role in supporting long-term environmental goals and advancing the principles of resource circularity.

Metagenomic insights into plasmid-mediated antimicrobial resistance in poultry slaughterhouse wastewater: antibiotics occurrence and genetic markers

Slaughterhouse wastewater represents important convergence and concentration points for antimicrobial residues, bacteria, and antibiotic resistance genes (ARG), which can promote antimicrobial resistance propagation in different environmental compartments. This study reports the assessment of the metaplasmidome-associated resistome in poultry slaughterhouse wastewater treated by biological processes, employing metagenomic sequencing. Antimicrobial residues from a wastewater treatment plant (WWTP) that treats poultry slaughterhouse influents and effluents were investigated through high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). Residues from the macrolide, sulfonamide, and fluoroquinolone classes were detected, the latter two persisting after the wastewater treatment. The genetic markers 16S rRNA rrs (bacterial community) and uidA (Escherichia coli) were investigated by RT-qPCR and the sul1 and int1 genes by qPCR. After treatment, the 16S rRNA rrs, uidA, sul1, and int1 markers exhibited reductions of 0.67, 1.07, 1.28, and 0.79 genes copies, respectively, with no statistical significance (p > 0.05). The plasmidome-focused metagenomics sequences (MiSeq platform (Illumina®)) revealed more than 100 ARG in the WWTP influent, which can potentially confer resistance to 14 pharmacological classes relevant in the human and veterinary clinical contexts, in which the qnr gene (resistance to fluoroquinolones) was the most prevalent. Only 7.8% of ARG were reduced after wastewater treatment, and the remaining 92.2% were associated with an increase in the prevalence of ARG linked to multidrug efflux pumps, substrate-specific for certain classes of antibiotics, or broad resistance to multiple medications. These data demonstrate that wastewater from poultry slaughterhouses plays a crucial role as an ARG reservoir and in the spread of AMR into the environment.

From wastewater to clean water: Recent advances on the removal of metronidazole, ciprofloxacin, and sulfamethoxazole antibiotics from water through adsorption and advanced oxidation processes (AOPs)

Antibiotics released into water sources pose significant risks to both human health and the environment. This comprehensive review meticulously examines the ecotoxicological impacts of three prevalent antibiotics-ciprofloxacin, metronidazole, and sulfamethoxazole-on the ecosystems. Within this framework, our primary focus revolves around the key remediation technologies: adsorption and advanced oxidation processes (AOPs). In this context, an array of adsorbents is explored, spanning diverse classes such as biomass-derived biosorbents, graphene-based adsorbents, MXene-based adsorbents, silica gels, carbon nanotubes, carbon-based adsorbents, metal-organic frameworks (MOFs), carbon nanofibers, biochar, metal oxides, and nanocomposites. On the flip side, the review meticulously examines the main AOPs widely employed in water treatment. This includes a thorough analysis of ozonation (O3), the photo-Fenton process, UV/hydrogen peroxide (UV/H2O2), TiO2 photocatalysis, ozone/UV (O3/UV), radiation-induced AOPs, and sonolysis. Furthermore, the review provides in-depth insights into equilibrium isotherm and kinetic models as well as prospects and challenges inherent in these cutting-edge processes. By doing so, this review aims to empower readers with a profound understanding, enabling them to determine research gaps and pioneer innovative treatment methodologies for water contaminated with antibiotics.

Toxicological aspect of water treated by chlorine-based advanced oxidation processes: A review

As well established in the literature, residual toxicity is an important parameter for evaluating the sanitary and environmental safety of water treatment processes, and this parameter becomes even more crucial when chlorine-based processes are applied for water treatment. Eliminating initial toxicity or preventing its increase after water treatment remains a huge challenge mainly due to the formation of highly toxic disinfection by-products (DBPs) that stem from the degradation of organic contaminants or the interaction of the chlorine-based oxidants with different matrix components. In this review, we present a comprehensive discussion regarding the toxicological aspects of water treated using chlorine-based advanced oxidation processes (AOPs) and the recent findings related to the factors influencing toxicity, and provide directions for future research in the area. The review begins by shedding light on the advances made in the application of free chlorine AOPs and the findings from studies conducted using electrochemical technologies based on free chlorine generation. We then delve into the insights and contributions brought to the fore regarding the application of NH₂Cl- and ClO₂-based treatment processes. Finally, we broaden our discussion by evaluating the toxicological assays and predictive models employed in the study of residual toxicity and provide an overview of the findings reported to date on this subject matter, while giving useful insights and directions for future research on the topic.

Application of Electrochemical Oxidation for Water and Wastewater Treatment: An Overview

In recent years, the discharge of various emerging pollutants, chemicals, and dyes in water and wastewater has represented one of the prominent human problems. Since water pollution is directly related to human health, highly resistant and emerging compounds in aquatic environments will pose many potential risks to the health of all living beings. Therefore, water pollution is a very acute problem that has constantly increased in recent years with the expansion of various industries. Consequently, choosing efficient and innovative wastewater treatment methods to remove contaminants is crucial. Among advanced oxidation processes, electrochemical oxidation (EO) is the most common and effective method for removing persistent pollutants from municipal and industrial wastewater. However, despite the great progress in using EO to treat real wastewater, there are still many gaps. This is due to the lack of comprehensive information on the operating parameters which affect the process and its operating costs. In this paper, among various scientific articles, the impact of operational parameters on the EO performances, a comparison between different electrochemical reactor configurations, and a report on general mechanisms of electrochemical oxidation of organic pollutants have been reported. Moreover, an evaluation of cost analysis and energy consumption requirements have also been discussed. Finally, the combination process between EO and photocatalysis (PC), called photoelectrocatalysis (PEC), has been discussed and reviewed briefly. This article shows that there is a direct relationship between important operating parameters with the amount of costs and the final removal efficiency of emerging pollutants. Optimal operating conditions can be achieved by paying special attention to reactor design, which can lead to higher efficiency and more efficient treatment. The rapid development of EO for removing emerging pollutants from impacted water and its combination with other green methods can result in more efficient approaches to face the pressing water pollution challenge. PEC proved to be a promising pollutants degradation technology, in which renewable energy sources can be adopted as a primer to perform an environmentally friendly water treatment.

Feasibility study of porous media for treating oily sludge with self-sustaining treatment for active remediation technology

Oil sludge is the primary pollutant produced by the petroleum industry, which is characterized by large quantities, difficult disposal, and high toxicity. Improper treatment of oil sludge will pose a severe threat to the human living environment. Self-sustaining treatment for active remediation (STAR) technology has a specific potential for treating oil sludge, with low energy consumption, short remediation time, and high removal efficiency. Given the low smoldering porosity, poor air permeability, and poor repair effect of oil sludge, this paper considered coarse river sand as the porous medium, built a smoldering reaction device, conducted a comparative study on smoldering experiments of oil sludge with and without river sand, and studied the key factors affecting smoldering of oil sludge. The study shows that the repair effect is greatly improved by adding river sand, increasing the pore, and improving air permeability, and the total petroleum hydrocarbon removal rate reaches more than 98%, which meets the requirements of oil sludge treatment. When the mass ratio of oil sludge to river sand (sludge-sand ratio) is 2:1, the flow velocity is 5.39 cm/s, and the particle size of the medium is 2-4 mm. In addition, the best conditions for smoldering occur. The average peak temperature, average propagation speed, and average removal efficiency are relatively high. The peak temperature occurs in a short time; the heating time is also short, and the heat loss is low. Moreover, the generation of toxic and harmful gases is reduced, and secondary pollution is hindered. The experiment indicates that the porous media play a crucial role in the smoldering combustion of oil sludge.