Effects of total suspended solids, particle size, and effluent temperature on the kinetics of peracetic acid decomposition in municipal wastewater

Removal of hydrocarbons and heavy metals from petroleum water by modern green nanotechnology methods

Considered heavy metals, such as As(III), Bi(II), Cd(II), Cr(VI), Mn(II), Mo(II), Ni(II), Pb(II), Sb(III), Se(-II), Zn(II), and contaminating chemical compounds (monocyclic aromatic hydrocarbons such as phenolic or polycyclic derivatives) in wastewater (petrochemical industries: oil and gas production plants) are currently a major concern in environmental toxicology due to their toxic effects on aquatic and terrestrial life. In order to maintain biodiversity, hydrosphere ecosystems, and people, it is crucial to remove these heavy metals and polluting chemical compounds from the watery environment. In this study, different Nanoparticles (α-Fe₂O₃, CuO, and ZnO) were synthesized by green synthesis method using Portulaca oleracea leaf extract and characterized by UV-Vis spectrophotometers, FTIR spectroscopy, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) techniques in order to investigate morphology, composition, and crystalline structure of NPs, these were then used as adsorbent for the removal of As(III), Bi(II), Cd(II), Cr(VI), Mn(II), Mo(II), Ni(II), Pb(II), Sb(III), Se(-II), and Zn(II) from wastewater, and removal efficiencies of were obtained 100% under optimal conditions.

Review of Clay-Based Nanocomposites as Adsorbents for the Removal of Heavy Metals

Due to rapid industrialization, urbanization, and surge in modern human activities, water contamination is a major threat to humanity globally. Contaminants ranging from organic compounds, dyes, to inorganic heavy metals have been of major concern in recent years. This necessitates the development of affordable water remediation technologies to improve water quality. There is a growing interest in nanotechnology recently because of its application in eco-friendly, cost-effective, and durable material production. This study presents a review of recent nanocomposite technologies based on clay, applied in the removal of heavy metals from wastewater, and highlights the shortcomings of existing methods. Recently published reports, articles, and papers on clay-based nanocomposites for the removal of heavy metals have been reviewed. Currently, the most common methods utilized in the removal of heavy metals are reverse osmosis, electrodialysis, ion exchange, and activated carbon. These methods, however, suffer major shortcomings such as inefficiency when trace amounts of contaminant are involved, uneconomical costs of operation and maintenance, and production of contaminated sludge. The abundance of clay on the Earth’s surface and the ease of modification to improve adsorption capabilities have made it a viable candidate for the synthesis of nanocomposites. Organoclay nanocomposites such as polyacrylamide-bentonite, polyaniline-montmorillonite, and β-cyclodextrin-bentonite have been synthesized for the selective removal of various heavy metals such as Cu2+, Co2+, among others. Bacterial clay nanocomposites such as E. coli kaolinite nanocomposites have also been successfully synthesized and applied in the removal of heavy metals. Low-cost nanocomposites of clay using biopolymers like chitosan and cellulose are especially in demand due to the cumulative abundance of these materials in the environment. A comparative analysis of different synthetic processes to efficiently remove heavy metal contaminants with clay-based nanocomposite adsorbents is made.

Examining the antimicrobial efficacy of granulated tetraacetylethylenediamine derived peracetic acid and commercial peracetic acid in urban wastewaters

The ever-increasing need for access to safe water has meant that alternative water sources and innovative water reclamation approaches are often required to meet the global water demand. As a result, many wastewater treatment facilities have faced regulatory pressure to seek alternative disinfection methods that ensure public health safety, while adhering to regulations that set limits on carcinogenic disinfection by-products (DBPs). Peracetic acid (PAA) is an emerging wastewater disinfectant in the United States that has been widely used in other industries such as food sanitization and does not produce carcinogenic DBPs. However, several factors such as transport, storage, and physical and chemical effects have stymied its widespread use in wastewater markets. Therefore, the purpose of this study was to examine the antimicrobial efficacy of an on-site generated PAA compared against a commercially available PAA. Antimicrobial efficacy was assessed using standard fecal contamination indicators (i.e., total coliforms and Escherichia coli) in six urban wastewater treatment facilities ranging in size and treatment processes. Overall, few statistical differences were found between the antimicrobial efficacies of on-site generated PAA and commercially available PAA; however, before becoming more widely utilized, the on-site PAA should be tested against emerging fecal contamination indicators (e.g., human norovirus and enterovirus) and be assessed in terms of economic and sustainability impacts. PRACTITIONER POINTS: Alternative Ct approaches should be considered when using disinfectants like PAA. On-site generated PAA can achieve the same level of disinfection as commercial PAA. On-site generation of PAA may help further its use as a wastewater disinfectant.

Implications of COD analysis use in the peracetic acid-based wastewater treatment

Peracetic acid (PAA) stands out as a safe and environmental-friendly oxidant and disinfectant which has been effectively used in wastewater treatment. Chemical oxygen demand (COD) is a very popular analysis in wastewater treatment; however, the interference of residual PAA on the COD measurement is still unknown. In this context, this study investigated the implications of applying the COD analysis in PAA-based treatment. Each 1 mg·L^-1 of PAA increased the COD concentration around 13.5 mg O₂·L^-1. Residual PAA and hydrogen peroxide (H₂O₂) were efficiently neutralized by sodium metabisulfite (SMBS) at the optimal SMBS/PAA ratio of 10.2:1 in a wide pH range (5 to 9). The effect of PAA addition on the COD concentration was evaluated in different water matrices (potassium hydrogen phthalate and wastewater solutions). The COD results with the SMBS addition at optimal SMBS/PAA ratio were lower than the ones without it. It may happen due to the neutralization of residual H₂O₂/PAA and the complexity of the water matrices which can interfere in the COD results. This study discussed the impact of the residual H₂O₂/PAA neutralization before the COD analysis, and this investigation can be used as a practical guideline for the correct COD measurement in PAA-based treatment.

Peracetic Acid-Ruthenium(III) Oxidation Process for the Degradation of Micropollutants in Water

This paper presents an advanced oxidation process (AOP) of peracetic acid (PAA) and ruthenium(III) (Ru(III)) to oxidize micropollutants in water. Studies of PAA-Ru(III) oxidation of sulfamethoxazole (SMX), a sulfonamide antibiotic, in 0.5-20.0 mM phosphate solution at different pH values (5.0-9.0) showed an optimum pH of 7.0 with a complete transformation of SMX in 2.0 min. At pH 7.0, other metal ions (i.e., Fe(II), Fe(III), Mn(II), Mn(III), Co(II), Cu(II), and Ni(II)) in 10 mM phosphate could activate PAA to oxidize SMX only up to 20%. The PAA-Ru(III) oxidation process was also unaffected by the presence of chloride and carbonate ions in solution. Electron paramagnetic resonance (EPR) measurements and quenching experiments showed the dominant involvement of the acetyl(per)oxyl radicals (i.e., CH₃C(O)O^• and CH₃C(O)OO^•) for degrading SMX in the PAA-Ru(III) oxidation process. The transformation pathways of SMX by PAA-Ru(III) were proposed based on the identified intermediates. Tests with other pharmaceuticals demonstrated that the PAA-Ru(III) oxidation system could remove efficiently a wide range of pharmaceuticals (9 compounds) in the presence of phosphate ions in 2.0 min at neutral pH. The knowledge gained herein on the effective role of Ru(III) to activate PAA to oxidize micropollutants may aid in developing Ru(III)-containing catalysts for PAA-based AOPs.

Wastewater disinfection: long-term laboratory and full-scale studies on performic acid in comparison with peracetic acid and chlorine

Chemical disinfection of municipal wastewater to preserve the microbiological quality of discharges has traditionally relied on chlorine, and more recently on peracetic acid (PAA). A more recent option is performic acid (PFA). This work uses laboratory and full-scale studies over a span of 15 years and five wastewater treatment plants (WWTPs) in Italy, to compare the efficacy of these three disinfectants and identify the differences among peracids in a context where both can be an alternative to chlorine. The investigations focused on treatment effectiveness and bacterial inactivation kinetics using E. coli and the more resistant enterococci, as well as on PFA and PAA decomposition as the residuals may affect the downstream microenvironment. Furthermore, the potential for the two peracids to oxidize organic substances and create troublesome byproducts was also studied. Chlorine, applied as hypochlorite ("HYP") and here essentially functioning as chloramines, was used as a baseline comparison for the two peracids. Appropriate statistical tests were applied to the data from different WWTPs to account for potential interferences and compounding effects of the different matrices. Average doses of 0.8, 2.9 and 1.4 mg/L and contact times of 18, 21 and 31 min, respectively for PFA, chlorine and PAA guaranteed with a high level of assurance the 5000 CFU/100 mL E. coli limit; the order of effectiveness was PFA > HYP > PAA, refined as PFA > HYP ≈ PAA against E. coli and PFA ≈ HYP > PAA with enterococci. Similar bacterial reductions for the peracids were found at higher disinfectant doses used for the kinetic tests. PFA decayed more quickly than PAA. The first-order decay constants were 0.031 and 0.007 min^-1, respectively, suggesting that disinfection residuals when PFA is used may be less of a concern than with PAA. This faster decomposition did not affect the PFA oxidation power on estrone, which was as weak as that of PAA.