Optimizing booster chlorination in water distribution networks: a water quality index approach

Abstract

The optimization of chlorine dosage and the number of booster locations is an important aspect of water quality management in distribution networks. Booster chlorination helps to maintain uniformity and adequacy of free residual chlorine concentration, essential for safeguarding against microbiological contamination. Higher chlorine dosages increase free residual chlorine concentration but generate harmful by-products, in addition to taste and odor complaints. It is possible to address these microbial, chemical, and aesthetic water quality issues through free residual chlorine concentration. Estimating a water quality index (WQI) based on regulatory chlorine thresholds for microbial, chemical, and aesthetics criteria can help engineers make intelligent decisions. An innovative scheme for maintaining adequate residual chlorine with optimal chlorine dosages and numbers of booster locations was established based on a proposed WQI. The City of Kelowna (BC, Canada) water distribution network served to demonstrate the application of the proposed scheme. Temporal free residual chlorine concentration predicted with EPANET software was used to estimate the WQI, later coupled with an optimization scheme. Preliminary temporal and spatial analyses identified critical zones (relatively poor water quality) in the distribution network. The model may also prove useful for small or rural communities where free residual chlorine is considered as the only water quality criterion.

Assessment of water quality in distribution networks through the lens of disinfection by-product rules

“…One of the common practices is to select specific usage-related parameters and convert these to a unitless measure, called a water quality index (WQI (Boyacioglu, 2007;Dunnette, 1979;Espejo et al, 2012;Hurley et al, 2012;Islam et al, 2011;Liou et al, 2004;Pesce and Wunderlin, 2000;Swamee and Tyagi, 2007). Most of the formulations have fixed parameters, which makes the WQI rigid and not suitable for DBBP rules.…”

“…Most of the formulations have fixed parameters, which makes the WQI rigid and not suitable for DBBP rules. CCME WQI was determined to be the most accepted WQI as it is flexible enough to include any parameter, simplistic, and reflects regulatory violations (Islam et al, 2013). However, it has …”

“…some redundancy in factor consideration and has been modified in one of our previous studies (Islam et al, 2013). The CCME WQI is a popular index consisting of 3 factors (CCME, 2001):…”

“…If one parameter fails C = 1, otherwise C = 0. Frequency and amplitude, V 2 : Islam et al (2013) have combined frequency and amplitude. Another modification is done by combining the relative weights for the normalized sum of excursions (nse):…”

“…It has been applied to source water and needs to be applied for DNs (Khan et al 2003). Previously, there was some limitation in the CCME WQI formulation and some modifications were made to overcome this (Islam et al, 2013). However, the index is too generic and requires further modification to make it suitable for DBP rules.…”