Predicting Residual Adsorbable Organic Halides Concentrations in Industrial Wastewater Using Typical Wastewater Parameters

Hannah Milh,Steven De Laet,Raf Dewil,Bert Bastiaens,Kwinten Van Eyck,Deirdre Cabooter,Dirk Leysen

doi:10.3390/w12061653

Abstract

The aim of this study was to predict the residual adsorbable organic halides (AOX) concentration in an industrial wastewater using conventional, easy-to-measure wastewater parameters. In a pilot test unit, the wastewater was subjected to ozonation at various intensities, resulting in an AOX-removal and hence varying AOX concentrations. In first instance, the parameters used for modeling were selected using Pearson and Spearman correlations. Secondly, multiple linear regression (MLR) was used as a modeling tool to predict both the soluble and total AOX concentration in wastewater samples. To prevent overfitting, a 10-fold cross-validation was carried out. It was found that both the soluble and the total AOX concentration can be predicted using typical wastewater parameters. The measured parameters were pH, chloride concentration, Water-Soluble Organic Carbon concentration (WSOC), UV-VIS spectrum, turbidity, and Solids Removable by Filtration (SRF). Out of these parameters, the following parameters were found to be significant for prediction of the total AOX concentration: turbidity; SRF; UV-VIS absorbance at 200; 227, and 250 nm; and pH. UV-VIS absorbance at 200 and 227 nm and turbidity of the wastewater were found to contribute significantly to the final model. For the soluble AOX concentration, the significant parameters were turbidity; SRF; absorbance at 200, 227, and 250 nm; pH, and chloride concentration. Here, UV-VIS absorbance at 200 and 227 nm were found to contribute significantly to the final model. The obtained final models had an adjusted R2 of 0.921 and 0.916 for the total and soluble AOX, respectively. As a result of the obtained models, both AOX concentrations can be predicted using parameters that are easier to determine. This allows for a significant reduction in wastewater sampling and analysis time and offers the opportunity to optimize the ozone dosing in the wastewater treatment process in the future.

Highlights

Adsorbable organic halides (AOX) are organic compounds containing halogen atoms (Cl, Br, and I) [1,2]
A possible solution, which enables the removal of the particulate AOX before it ends up in the wastewater influent, is the installation of an ozonation unit
A pilot ozonation unit was placed on the plant site and ozonation was performed on effluent from the coagulation-flocculation step

Summary

Introduction

Adsorbable organic halides (AOX) are organic compounds containing halogen atoms (Cl, Br, and I) [1,2]. AOX are mainly formed in industrial processes using chlorine or chlorinated chemicals, such as bleaching. The production of AOX is a major problem arising in the paper and pulp industries [3]. Because AOX are unwanted side products of industrial processes, they usually end up in the resulting wastewater. AOX can have carcinogenic or mutagenic properties and should, be removed from wastewater [4].

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