Assessment on the removal of organic chemicals from raw and drinking water at a Llobregat river water works plant using GAC

Abstract

A screening study was conducted on samples from a Llobregat river water works plant (WWP) in order to establish a better treatment for the removal of organic pollutants. The Llobregat river is a polluted river supplying water to Barcelona (Spain) and its surroundings with a population of approximately 3.2 million. A broad spectrum and high levels of organic chemicals were found in river water, including hydrocarbons, pesticides, surfactants, plasticizers and trihalomethanes. Despite a variety of treatment processes employed in the studied plant, a satisfactory removal of organic compounds from water is not guaranteed. Given that, improvement in water quality is achieved with the implementation of filtration with Granular Activated Carbon (GAC). Seven control column tests (CCT) with analytical GAC were conducted in series with their seven respective large column adsorbers to determine the performance of each GAC. Organic compounds from samples of raw and drinking water were collected by passing approximately 1000 l of water through a column of analytical GAC (representing monthly averages). Selected target compounds previously identified in raw and drinking water (trihalomethanes: bromoform; pesticides: terbutylazine and molinate; surfactants: polyethoxylated nonylphenols; plasticizers: diethyl phthalate and tri- n-butyl phosphate; halogenated compounds: trichlorobenzenes, 2-chloro pyridine; miscellaneous compounds: 2-ethyl hexanol, trimethyl-cyclohexenone, bromo-trimethyl-benzenes, bromo-polyethoxylated nonylphenols) were studied to predict the behavior of seven different commercial GACs. These pollutants were efficiently removed by using GAC bituminous coal based. The determination of organic compounds was carried out by using Soxhlet extraction and high-resolution gas chromatography with low resolution mass spectrometry (HRGC/LRMS) analysis.