Purpose: This study evaluated the dynamic impact of FC and organic load on the generation of haloacetic acids (HAAs) and trihalomethanes (THMs) in simulated wash water with water quality changes.
Methods: Lettuce juice (60 ml) was sequentially added into sodium hypochlorite solution (initial FC~80 mg/l, pH 6.7-6.8) with free chlorine periodically replenished when the FC concentration dropped below 2.0 mg/l. Water samples were collected 1 min after each lettuce juice addition with gentle agitation to measure water qualities including FC concentration, oxidation-reduction potential (ORP), pH, chemical oxygen demand (COD), and determine HAAs and THMs. HAAs and THMs’ concentrations were quantified by Gas Chromatography/Electron Capture Detection and Capillary Column Gas Chromatography/Mass Spectrometry using US-Environmental Protection Agency (EPA) methods. Data (four replicates) were analyzed using the 2-factor model and Pearson product-moment correlation test of SPSS.
Results: Results indicate that 88-2103 μg/l of total HAAs and 20.79-859.47 μg/l of total THMs were detected during dynamic water quality variances. These concentrations exceed US-EPA and European Union drinking water standards. Monobromoacetic acid (19.5 to 1348.9 μg/l), tribromoacetic acid (6.7 to 529.7 μg/l), chlorodibromoacetic acid (36.5 to 89.2 μg/l), and trichloroacetic acid (2.3 to 148.6 μg/l) are the major HAAs components. Chloroform (Trichloromethane, 20.12 to 858.0 μg/l) is the primary THMs present. A significant (P < 0.001) correlation of HAAs with COD, and THMs with FC was observed.
Significance: Optimizing wash water sanitizing systems to limit organic matters and maintain minimal effective FC concentration is critical. Results are important in produce safety, environmental and occupational health risks for produce washers, and regulatory agencies charged with setting limits for compounds of concern.