Abstract
Efforts to control of unwanted disinfection by-products (DBPs) can be hindered by the relatively low-frequency data that is generated from DBP monitoring for regulatory purposes. Differential UV absorbance (DUVA) has the potential to overcome some of these difficulties as a relatively simple and low-cost technique for the estimation of regulated DBPs (i.e., trihalomethanes, THMs, and haloacetic acids, HAAs). DUVA is based on the principle that differences in UV absorbance at specific wavelengths before and after chlorination can be correlated to DBP occurrence. This project sought to assess a lab-based protocol for the determination of a site-specific linear calibration curve for in situ real-time estimations of DBPs from DUVA measurement in water treatment plants (WTPs). A field spectrophotometer probe capable of high frequency scans within the UV light wavelength spectra with light paths of 100 mm was used. Models were developed to estimate DBP levels, at a scale representative of DUVA and DBP levels that actually occur in the WTP under study. Results showed that level of uncertainty on DBP levels estimation is relatively low (23% for HAAs and 32% for THMs). Although DBP estimations through DUVA are not of regulatory value, they can be used for real-time estimation of DBP levels to better inform operational decision making in water treatment plants and management of DBPs in distribution systems.
Highlights
Disinfection process, mainly with chlorine, to prevent microbiological contamination of water can lead to the formation of hazardous disinfection by-products (DBPs) due to the reaction of chlorine with natural organic matter (NOM) present in the water [1]
Even if R2 values of large-scale models are quite stronger (Table 4), these models were developed on a range of DBP levels that is not thought to be representative of water treatment plants (WTPs) levels like similar previous studies [22,24,25,34,36]. It highlights that it might me inadequate to develop models on range of DBP levels deliberately large. These results show that even if models present a very high R2 factor, they would not be as efficient to estimate DBP levels as if they were developed at a limited scale representative of Differential UV absorbance (DUVA) and DBP
A lab-based protocol was developed for the determination of a site-specific linear calibration curve for in situ real-time estimation of DBP occurrences using DUVA
Summary
Disinfection process, mainly with chlorine, to prevent microbiological contamination of water can lead to the formation of hazardous disinfection by-products (DBPs) due to the reaction of chlorine with natural organic matter (NOM) present in the water [1]. DBPs constitute an important concern for water systems, especially systems supplied by surface waters. Source water generally presents a level higher of NOM than groundwater [4,7]. Trihalomethanes (THMs) and haloacetic acids (HAAs) are the most commonly observed chlorinated DBPs in drinking water [2,8,9]. Their occurrence is regulated in several countries, including USA and Canada. In the United States, USEPA established THMs and HAAs guidelines at 80 μg/L and 60 μg/L respectively [10]
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