Application of heterogeneous catalytic ozonation process for treatment of high toxic effluent from a pesticide manufacturing plant

Mina Ghahrchi,Fariba Gohari,Edris Bazrafshan,Yousef Dadban Shahamat,Behruz Adamiyat Badan

doi:10.34172/ehem.2020.10

Abstract

Background: The discharge of untreated wastewater containing toxic and resistant compounds into the environment is a serious threat for ecosystems. Therefore, this study was conducted to evaluate the treatment of poison production factory wastewater using heterogeneous catalytic ozonation process (COP). Methods: Magnetic carbon nanocomposite was used as a catalyst at concentrations of 1, 2, and 4 g/L. Its effect on improving the treatment process was evaluated at reaction time of 30, 60, 90, and 120 minutes. At the end of each experiment, parameters including total organic carbon (TOC), chemical oxygen demand (COD), biological oxygen demand (BOD5 ), pH, electrical conductivity (EC), and turbidity were measured. Results: It was revealed that in single ozonation process (SOP), the maximum removal efficiencies of TOC, COD, and BOD5 were achieved at reaction time of 120 minutes as 56%, 40%, and 11.7%, respectively. By adding the catalyst to the wastewater, the treatment process was improved, so that the maximum removal efficiencies of COD (91%), TOC (73%), and BOD5 (74%) were obtained at catalyst concentration of 4 g/L. Under this condition, BOD5 /COD ratio increased from 0.22 to 0.64. Also, the results of analysis of ozone consumption per each mg of reduced COD showed that its amount sharply decreased from 2.1 mgO3 / mg COD removal in the SOP, to 0.34 mgO3 /mg COD removal in the COP. The results of kinetic reaction analysis also revealed that the rate constant increased from 0.007 to 0.02 min-1. Conclusion: According to the results, it can be concluded that the COP at a catalyst concentration of 4 g/L, by decomposing resistant compounds and increasing the biodegradability, can be used as a suitable pretreatment method for biological processes.

Highlights

Nowadays, with increasing resistant compounds in industrial wastewater, more stringent environmental regulations, inefficiency of conventional treatment methods for removal of such pollutants to achieve desirable standards are among the main problems of wastewater treatment industry, which require more research for finding new and effective methods to remove the pollutants [1].Pesticide manufacturing industry is categorized as one of the industries, which its wastewater contains resistant and recalcitrant compounds, such as confidor, paraquat, glyphosate, and abamectin
In this study, the wastewater containing various pesticides, such as confidor, paraquat, glyphosites, and abamectin was treated under the single ozonation process (SOP) and catalytic ozonation process (COP)
In the COP, the effect of different concentrations of catalysts (1, 2, and 4 g/L) on the treatment process improvement was investigated by measuring the amounts of chemical oxygen demand (COD), total organic carbon (TOC), BOD5, pH, electrical conductivity (EC), turbidity, and ozone consumption

Summary

Introduction

With increasing resistant compounds in industrial wastewater, more stringent environmental regulations, inefficiency of conventional treatment methods for removal of such pollutants to achieve desirable standards are among the main problems of wastewater treatment industry, which require more research for finding new and effective methods to remove the pollutants [1].Pesticide manufacturing industry is categorized as one of the industries, which its wastewater contains resistant and recalcitrant compounds, such as confidor, paraquat, glyphosate, and abamectin. Hachami et al investigated electrochemical oxidation of methidathion as an organophosphorus pesticide by SnO2 and borondoped diamond (BDD) anodes They reported that COD removal efficiencies under conditions of 2% NaCl, 60 mA/ cm current density, and 120 minutes reaction time, using SnO2 and BDD electrodes, were 73% and 85%, respectively [10]. Results: It was revealed that in single ozonation process (SOP), the maximum removal efficiencies of TOC, COD, and BOD5 were achieved at reaction time of 120 minutes as 56%, 40%, and 11.7%, respectively. Conclusion: According to the results, it can be concluded that the COP at a catalyst concentration of 4 g/L, by decomposing resistant compounds and increasing the biodegradability, can be used as a suitable pretreatment method for biological processes.

Methods

Results

Discussion

Conclusion