Treatment Technologies for Emerging Organic Contaminants Removal from Wastewater

Bacterial enzymatic degradation of recalcitrant organic pollutants: catabolic pathways and genetic regulations

Contamination of soil and natural water bodies driven by increased organic pollutants remains a universal concern. Naturally, organic pollutants contain carcinogenic and toxic properties threatening all known life forms. The conventional physical and chemical methods employed to remove these organic pollutants ironically produce toxic and non-ecofriendly end-products. Whereas microbial-based degradation of organic pollutants provides an edge, they are usually cost-effective and take an eco-friendly approach towards remediation. Bacterial species, including Pseudomonas, Comamonas, Burkholderia, and Xanthomonas, have the unique genetic makeup to metabolically degrade toxic pollutants, conferring their survival in toxic environments. Several catabolic genes, such as alkB, xylE, catA, and nahAc, that encode enzymes and allow bacteria to degrade organic pollutants have been identified, characterized, and even engineered for better efficacy. Aerobic and anaerobic processes are followed by bacteria to metabolize aliphatic saturated and unsaturated hydrocarbons such as alkanes, cycloalkanes, aldehydes, and ethers. Bacteria use a variety of degrading pathways, including catechol, protocatechuate, gentisate, benzoate, and biphenyl, to remove aromatic organic contaminants such as polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and pesticides from the environment. A better understanding of the principle, mechanisms, and genetics would be beneficial for improving the metabolic efficacy of bacteria to such ends. With a focus on comprehending the mechanisms involved in various catabolic pathways and the genetics of the biotransformation of these xenobiotic compounds, the present review offers insight into the various sources and types of known organic pollutants and their toxic effects on health and the environment.

New Insights in factors affecting ground water quality with focus on health risk assessment and remediation techniques

Groundwater is considered as the primary source of water for the majority of the world's population. The preponderance of the nation's drinking water, as well as agricultural and industrial water, comes from groundwater. Groundwater level is becoming increasingly challenging to replenish due to climate change. Fertilizer application and improper processing of industrial waste are the two major anthropogenic drivers of groundwater pollution. Arsenic and cadmium are two of the principal heavy metal pollutants that have affected groundwater quality by human activity. When people are exposed to both non-carcinogenic and carcinogenic contaminants for an extended period, toxic effects might occur. It can have detrimental health effects from long-term exposure to contaminants, even in low amounts. As a result, metal contamination concentrations and fractions can be used to determine potential health concerns. At the same time, contaminants also need to be removed or converted to harmless products by groundwater remediation. Remediation of groundwater quality can be accomplished in several ways, including natural and artificial means. The purpose of this review is to explore a wide range of factors that affect groundwater quality, including their possible health effects. This communication provides state-of-the-art information about remediation approaches for groundwater contamination including hindrances and perspectives in this area of research. The in-depth information provided in different sections of this communication would expand the scope of interdisciplinary research.

Sustainable Treatment Techniques for Emerging Pollutants—The Case of Personal Hygiene Products

Personal care products (PCPs) enter wastewater primarily through greywater. Treatment plants have not been able to remove this type of contaminant, although PCP abatement techniques have been developed in recent years. The objective of the current study has been to encounter the sustainable technique that keeps the optimal balance between the criteria considered in the comparison. Therefore, a bibliographic review was conducted in scientific databases of the last eight years, demonstrating that co-composting, anaerobic–aerobic sequencing bioreactors and contaminant absorption through the use of carbon nanotubes are the ones with the least environmental impact. Subsequently, the Saaty and Modified Saaty methods were applied, with a comparative criteria of construction costs, maintenance costs, efficiency and the stage of development. The results indicated that the co-composting technique is the best sustainable technique of those studied, with a score of 0.86/1, which means that the criteria analyzed maintain very close values between them. The co-composting technique yields a low environmental impact in eliminating personal care products. This research work constitutes a practical and easy-to-use tool for decision makers, since it allows finding an optimal elimination treatment for PCPs.

Recovery of resources from industrial wastewater employing electrochemical technologies: status, advancements and perspectives

In the last two decades, water use has increased at twice the rate of population growth. The freshwater resources are getting polluted by contaminants like heavy metals, pesticides, hydrocarbons, organic waste, pathogens, fertilizers, and emerging pollutants. Globally more than 80% of the wastewater is released into the environment without proper treatment. Rapid industrialization has a dramatic effect on developing countries leading to significant losses to economic and health well-being in terms of toxicological impacts on humans and the environment through air, water, and soil pollution. This article provides an overview of physical, chemical, and biological processes to remove wastewater contaminants. A physical and/or chemical technique alone appears ineffective for recovering useful resources from wastewater containing complex components. There is a requirement for more processes or processes combined with membrane and biological processes to enhance operational efficiency and quality. More processes or those that are combined with biological and membrane-based processes are required to enhance operational efficiencies and quality. This paper intends to provide an exhaustive review of electrochemical technologies including microbial electrochemical technologies. It provides comprehensive information for the recovery of metals, nutrients, sulfur, hydrogen, and heat from industrial effluents. This article aims to give detailed information into the advancements in electrochemical processes to energy use, improve restoration performance, and achieve commercialization. It also covers bottlenecks and perspectives of this research area.

Effective Disposal of Methylene Blue and Bactericidal Benefits of Using GO-Doped MnO2 Nanorods Synthesized through One-Pot Synthesis

Graphene oxide (GO)-doped MnO2 nanorods loaded with 2, 4, and 6% GO were synthesized via the chemical precipitation route at room temperature. The aim of this work was to determine the catalytic and bactericidal activities of prepared nanocomposites. Structural, optical, and morphological properties as well as elemental composition of samples were investigated with advanced techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-visible (vis) spectroscopy, photoluminescence (PL), energy-dispersive spectrometry (EDS), and high-resolution transmission electron microscopy (HR-TEM). XRD measurements confirmed the monoclinic structure of MnO2. Vibrational mode and rotational mode of functional groups (O-H, C=C, C-O, and Mn-O) were evaluated using FTIR results. Band gap energy and blueshift in the absorption spectra of MnO2 and GO-doped MnO2 were identified with UV-vis spectroscopy. Emission spectra were attained using PL spectroscopy, whereas elemental composition of prepared materials was recorded with scanning electron microscopy (SEM)-EDS. Moreover, HR-TEM micrographs of doped and undoped MnO2 revealed elongated nanorod-like structure. Efficient degradation of methylene blue enhanced the catalytic activity in the presence of a reducing agent (NaBH4); this was attributed to the implantation of GO on MnO2 nanorods. Furthermore, substantial inhibition areas were measured for Escherichia coli (EC) ranging 2.10-2.85 mm and 2.50-3.15 mm at decreased and increased levels for doped MnO2 nanorods and 3.05-4.25 mm and 4.20-5.15 mm for both attentions against SA, respectively. In silico molecular docking studies suggested the inhibition of FabH and DNA gyrase of E. coli and Staphylococcus aureus as a possible mechanism behind the bactericidal activity of MnO2 and MnO2-doped GO nanoparticles (NPs).

Non-conventional water reuse in agriculture: A circular water economy

Due to the growing and diverse demands on water supply, exploitation of non-conventional sources of water has received much attention. Since water consumption for irrigation is the major contributor to total water withdrawal, the utilization of non-conventional sources of water for the purpose of irrigation is critical to assuring the sustainability of water resources. Although numerous studies have been conducted to evaluate and manage non-conventional water sources, little research has reviewed the suitability of available water technologies for improving water quality, so that water reclaimed from non-conventional supplies could be an alternative water resource for irrigation. This article provides a systematic overview of all aspects of regulation, technology and management to enable the innovative technology, thereby promoting and facilitating the reuse of non-conventional water. The study first reviews the requirements for water quantity and quality (i.e., physical, chemical, and biological parameters) for agricultural irrigation. Five candidate sources of non-conventional water were evaluated in terms of quantity and quality, namely rainfall/stormwater runoff, industrial cooling water, hydraulic fracturing wastewater, process wastewater, and domestic sewage. Water quality issues, such as suspended solids, biochemical/chemical oxygen demand, total dissolved solids, total nitrogen, bacteria, and emerging contaminates, were assessed. Available technologies for improving the quality of non-conventional water were comprehensively investigated. The potential risks to plants, human health, and the environment posed by non-conventional water reuse for irrigation are also discussed. Lastly, three priority research directions, including efficient collection of non-conventional water, design of fit-for-purpose treatment, and deployment of energy-efficient processes, were proposed to provide guidance on the potential for future research.

Treatment of wastewater from petroleum industry: current practices and perspectives

Petroleum industry is one of the fastest growing industries, and it significantly contributes to economic growth in developing countries like India. The wastewater from a petroleum industry consist a wide variety of pollutants like petroleum hydrocarbons, mercaptans, oil and grease, phenol, ammonia, sulfide, and other organic compounds. All these compounds are present as very complex form in discharged water of petroleum industry, which are harmful for environment directly or indirectly. Some of the techniques used to treat oily waste/wastewater are membrane technology, photocatalytic degradation, advanced oxidation process, electrochemical catalysis, etc. In this review paper, we aim to discuss past and present scenario of using various treatment technologies for treatment of petroleum industry waste/wastewater. The treatment of petroleum industry wastewater involves physical, chemical, and biological processes. This review also provides scientific literature on knowledge gaps and future research directions to evaluate the effect(s) of various treatment technologies available.

Synthesis and Phase Transformation Studies of Dysprosium-Doped Bi4V2O11 Nanoparticles and Their Application in Visible Light Photocatalytic Degradation of Tetracycline Drug

Recently, Bi₄V₂O₁₁ as an electrolyte material has pulled in considerable consideration because of its remarkable novel applications. In this article, novel, dysprosium-doped (x = 0.2, 0.3, 0.4, and 0.5) Bi₄V₂O₁₁ (Dy/BVO) nanoparticles have been synthesized by sol-gel strategy. The photocatalyst Dy/BVO nanoparticles exhibit higher photocatalytic efficiency than BVO nanoparticles assessed by debasement of tetracycline drug under visible light illumination. Our work focuses on the phase transformation, conducting properties, and mechanisms of the Dy/BVO nanoparticles in relation to execute some methods of processing and manufacturing product in commercial applications. The characterization of Dy/BVO was performed by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, and UV-vis analysis. ac impedance spectroscopy was used to analyze the conducting behavior of synthesized nanoparticles in the temperature range 100-600 °C. The photocatalytic activity revealed that Dy/BVO remarkably enhanced the photocatalytic activity. This is the first report that Dy/BVO can destroy the drug effluent which is coming from the drug industry and also worried about the human health hazards.