No abstract

Anion exchange resins (AERs) were compared with aluminum-based coagulants for reducing disinfection by-product (DBP) precursor concentrations from a source water collected in northeast Ohio, USA. Three AERs (IRA-910, IRA-958, and MIEX) were evaluated to determine which resin would remove the most natural organic matter (NOM) and moieties responsible for DBP formation. All the AERs were found to be highly proficient at NOM removal specifically the moieties that absorb UV254 (i.e., chromophores) over 75 min of contact time; however, MIEX removed NOM at a faster rate than IRA-910 and IRA-958 resins. Enhanced coagulation was effective at removing approximately 35% of the NOM and 40–60% of the chromophores and fluorophores (i.e., excitation–emission matrix pairs A and C). DBP formation was determined as a function of pH for the different NOM removal processes. MIEX treatment resulted in significant reduction in DBP concentrations when compared to chlorinating the raw source water. MIEX generally out-performed enhanced coagulation for reducing DBP formation. However, alum was found to remove more NOM and resulted in less DBPs compared to aluminum chlorohydrate. This could impact water utilities trying to balance the health effects due to DBP exposure verses chemical/sludge management costs.

No abstract

Three copper-based algaecide products were investigated for use in a drinking water source to address cyanobacteria growth. Bench-scale experiments were used to determine the optimal dose of each product given Lake Rockwell’s indigenous population and reservoir-specific characteristics. The optimal dose of Cutrine Ultra was determined to be a quarter dose (corresponding to 0.125 mg/L Cu) as it decreased 55% of the cyanobacteria population with limited release of microcystin and minimal rebound in the cyanobacteria population. The optimal dose for EarthTec was determined to be a half dose (i.e., 0.5 mg/L). The full dose was optimal for SeClear (1 mg/L Cu). The optimal doses had extracellular microcystin levels of 0.99 ± 0.09 µg/L (quarter dose Cutrine Ultra), 3.69 ± 0.43 µg/L (half dose EarthTec) and 0.92 ± 0.26 µg/L (full dose SeClear) by day 2. EarthTec and Cutrine Ultra facilitated a similar overall response, and the cyanobacteria population was predominately suppressed in the initial 2 days following treatment and then increased between 7 and 14 days after treatment (i.e., rebound). Both the suppression within the first 2 days and the rebound between 7 and 14 days after treatment were a function of dose (e.g., lower dose, larger increase in rebound). Although SeClear suppressed the cyanobacteria population during the initial 2 days after treatment (42,000 ± 3240 cells/mL at the baseline to 4822 ± 841), the cyanobacteria population rebounded significantly (p < 0.05) between 2 and 7 days after treatment.