Evaluation of methods for the recovery, chemical and toxicological characterization of trace organics
"Organic contaminants are generated in substantial quantities by the activities of man and through natural processes, and are present in natural runoff, industrial wastes, and agricultural discharges; synthetic organic chemicals, many of which are refractory and reach surface and subsurface water, are of particular significance. Earlier studies have generally emphasized the organoleptic and esthetic problems caused by trace organics, although their acute and long-term toxic potential has also been recognized. The overall objective of this investigation was the analytical and toxicological characterization of trace organics recovered concomitantly from Missouri waters of varied character by large-scale solvent extraction (SEM) and carbon adsorption (CAM) methods. The specific objectives included the evaluation of solvent extraction contactors, recovery of trace organics from selected sites, development of a subacute toxicity bioassay procedure, and chemical characterization. Three solvent extraction units, a high speed mixer, perforated column and packed column, were built and evaluated under laboratory and field conditions; the first 2 contactors were reasonably efficient in recovering trace organics and relatively inexpensive to build, and the high speed mixer was selected for the large-scale unit. The modified CAM (high flow) system was composed of 2 parallel banks consisting of either 2 activated carbon filters in series or a pressure sand filter followed by 2 carbon filters. The yield of organics from 3 water sources, a lake and 2 rivers, was generally greater for the solvent chloroform extract (SCE), however, the SEM and CAM possessed different selectivities. Increased turbidity usually caused a decrease in the quantity of extracts obtained by the SEM and CAM, and the CAM recovery was 30 percent higher for a treated water than for the corresponding raw river water. Carbon chloroform (CCE) and carbon alcohol (CAE) extracts previously recovered from a large spring, and CCE, CAE, and SCE obtained from the lake were selectively characterized by gel permeation, gas-liquid and ion-exchange chromatography; nuclear magnetic resonance; elemental analysis; and trace element analysis by disperse electron scattering, neutron activation, and emission spectroscopy. Gel permeation was effective in separating the CCE and CAE materials and establishing their molecular size distribution; the lake CCE and CAE were characterized by a varied distribution and molecules of large size (up to 50,000 Å), while the treated river water CCE and CAE reflected mostly low molecular weight compounds (1 to 20 A) and a uniform distribution. Significant amounts of trace metals were found in CCE, CAE and SCE, indicating the likely presence of organometallic compounds in the extracts. The toxicity studies were designed to measure the harmful effects of trace organics on white rats in vivo by voluntary oral ingestion of individual and composite extracts at concentration levels similar to those found in natural waters, and in vitro by enzymatic investigation using rat tissue homogenates. The composite lake and spring CCE+CAE at doses of 1 and 2 mg/day caused serious physiological distress to the animals, including cyanosis, rusty tail and loss of hair, and the subsurface composite also induced histological damage to the liver and kidneys; exposure to the lake SCE caused damage to the liver and kidneys. A test protocol has been developed for the comprehensive investigation of the chemical and toxicological characteristics of organic contaminants. The inability of activated carbon treatment to quantitatively remove these materials from finished water makes their evaluation a primary concern to the water works industry"--Abstract, pages ii-iv.
Missouri University of Science and Technology
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