Evaluation of disinfection by-product (DBP) formation and fingerprint in a swimming pool in Bitlis/Turkey: a case study

Abstract

In this study, water quality parameters and disinfection by products (DBPs) were monitored and correlations between them were statistically investigated in a swimming pool in the province of Bitlis in Turkey. Risk assessment was then performed for trihalomethanes (THMs) and haloacetic acids (HAAs) in the context of public health. According to results, the carbonaceous organics (maximum total organic carbon (TOC): 3.89 mg/L) and nitrogenous (maximum total nitrogen (TN): 6.84 mg/L) substances came from swimmers as the precursor compounds for the formation of DBPs. Pool water free chlorine concentration varied depending on the manual dosage (between 0 to 2.2 mg/L) and sometimes exceeded the Turkish limits (1-1.5 mg/L). This situation increased DBPs formation. Bromide concentration detected in pool water can reach up to 15-fold the value in groundwater. This provides the basis for formation of brominated DBPs which are more carcinogenic than chlorinated species. The THM4 (mean: 85.4 µg/L) and bromoform (mean: 70.2 µg/L) concentrations were higher than those obtained in most countries. Low nitrogenous compounds limited the haloacetonitrile (HAN) production (mean: 3.52 µg/L). Significant differences were detected between HAA5 and HAA9 concentrations (mean: 181 and 219 µg/L respectively) and this difference came from high amounts of brominated HAA species. Other DBPs that cannot be detected on species basis varied and constituted mean 53.5% of adsorbable organic halogens (AOX). This situation creates uncertainty in terms of health hazards. According to Pearson correlations, there were significant correlations between AOX formation and TOC, TN, conductivity, total chlorine, nitrate and temperature. This indicates that DBPs formation was mainly influenced by the precursors in the water and the physical conditions in the pool. Therefore these parameters are the fingerprint of DBP formation in the studied pool water and negative or positive changes in these parameters directly affect DBP generation. It is very important to keep them under constant control in pool water. According to the risk assessment results, HAA concentration in the pool was found to have the potential to pose a risk to public health. The study provides fingerprinting information for DBP formation under uncontrolled pool conditions.