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Organophosphate pesticides (OPs) are highly toxic; their presence in surface waters is a matter of great concern. To the best of our knowledge, OPs in wastewater from agrochemical manufacturing facilities (AMFs) and influents and effluents from agrochemical wastewater treatment plants (AWWTPs) have not been previously investigated. Therefore, we investigated the presence of 8 OPs (5 of which are regulated under the Water Environment Conservation Act (WECA)) in 15 AMFs and 13 AWWTPs detected through surface water monitoring and proposed measures for effectively regulating these OPs in AWWTPs. Five OPs (chlorpyrifos, diazinon, dichlorvos, EPN, and fenitrothion) were detected in the AMF and AWWTP influents; three (methyldemeton, parathion, and phenthoate) were not. Of the five detected OPs, chlorpyrifos, dichlorvos, and fenitrothion are not currently regulated via effluent limitations for WWTPs under WECA; thus, additional regulations are required. The most effective process configuration for the removal of these OPs was biological treatment through activated sludge processes, followed by activated carbon adsorption. In the system, 100% OP removal from the AWWTP influents was observed. This treatment technology can be implemented in AWWTPs to minimize the presence of OPs in surface waters, thereby protecting human health and aquatic life. [ABSTRACT FROM AUTHOR]

An integrated system based on a heterogeneous catalytic wet hydrogen peroxide oxidation (CWHPO) and subsequent rotating biological contactors (RBCs) has been modeled for the treatment of agrochemical wastewater. One dimensional pseudo-homogeneous model was proposed for the CWHPO step. The reaction rate for TOC removal (k 1 ) was 0.087 1/min. In the case of the RBCs, two different approaches were considered: the pseudo-homogeneous model was based on Kornegy and Clark equations and it is restricted to only one substrate limitation, TOC, for the microbial growth. The microbial growth was modeled by a Monod type equation. The uptake rate and saturation coefficient values were P = 0.94 g/dm 2 d and Ks = 0.53 g/dm 3 . The integrated non-pseudo-homogeneous model considers a two-phase bioreactor in which all the biochemical processes occur in the solid biofilm phase. In this model, processes such as biofilm growth and diffusion of nutrients into biofilm were taken into account. The microbial growth was modeled using a double Monod equation with substrate limitation by TOC and total nitrogen (TN). Both approaches were able to describe the CWHPO-RBCs performance at different operating conditions with an estimated growth rate (μ MAX ) of 3.62 1/d. The calculated TOC removal was in good agreement with the experimental results. The two-phase model was also able to predict the TN removal of the system. The modeling of the coupling CWHPO/RBCs process could be a useful guide in order to achieve a cost-effective process leading to optimum C/N composition of the treated effluent and resulting in better overall removal efficiency. [ABSTRACT FROM AUTHOR]

Highlights: [•] Agrochemical wastewater treatment by catalytic peroxide oxidation and biological system. [•] Oxidation reduced significantly the total organic carbon and increased its biodegradability. [•] Remarkable performance and stability of the rotating biological contactors. [•] Treated effluent fulfilled the mandatory values of the regional law. [ABSTRACT FROM AUTHOR]

The Ce-doped bismuth oxide have been fascinated significantly due to the potential applications in ecological decontamination by photodegradation of the dye pollutants and agrochemical wastewater in to ecofriendly byproducts. Ceria (CO), Bismuth oxide (BO) and Ce-modified bismuth oxide (CBO) nanocrystalline materials were synthesized and thoroughly characterized by XPS, powder XRD, SEM-EDS, FT-IR, Raman, UV–Visible diffuse reflectance (UV–vis-DRS), photocurrent measurements, electrochemical impedence spectroscopy and photoluminescence (PL) spectral analysis. The band gap energy of Bi 2 O 3 was reduced from 3.35 to 2.64 eV, the transformation of the monoclinic (α-Bi 2 O 3) phase to the tetragonal (β-Bi 2 O 3) phase and increase in BET surface area was observed upon Ce4+ doping into BO. Low fluorescence intensity, lesser arc radius of the Nyquist plots, high photocurrent response of CBO specifies a reduction in the rate of recombination of photogenerated electron and hole pair. The photocatalytic activity of BO, CO and CBO were examined for photodegradation of methylene blue (MB), cotton blue (CB) and agrochemical industrial wastewater (ACIWW) under visible light treatment. CBO exhibited greater degradation of MB, CB and ACIWW whereas pristine BO was less active in the degradation of pollutants. The greater photocatalytic activity of CBO is ascribed to stronger absorption of visible-light energy because of the higher surface area and shrinking of band gap energy as well as the easy production of •OH radicals during the photocatalytic reaction evidencing from scavenger studies. Even after five cycles of photodegradation of MB, CB and ACIWW, the photocatalyst CBO is found to be consistent in photocatalytic activity and powder XRD pattern as compared to pure CBO material. [Display omitted].Synthesis and characterization of pure Bi 2 O 3 material and CeO 2 -Bi 2 O 3 composite material for photodegradation of methylene blue, cotton blue dyes and agrochemical wastewater under visible-light-driven process. • Preparation of new pure Bi 2 O 3 and CeO 2 –Bi 2 O 3 composite nanomaterials by wet-impregnation technique and systematically characterized. • Photodegradation of organic dye pollutants such as methylene blue and cotton blue under visible light irradiation. • Photodegradation of Agrochemical wastewater was investigated and identified with LC-MS data. • Mechanistic studies confirmed that the active species are hydroxy radials via various scavengers studies. [ABSTRACT FROM AUTHOR]