Evaluation of toxicity test procedure for screening treatability potential of waste in soil

Abstract

SynopsisA toxicity procedure has been developed and proposed for use in establishing acceptable initial loading rates and detoxification potentials for hazardous industrial waste when combined with soil. The procedure involves conducting toxicity screening and toxicity reduction experiments using selected waste-soil combinations. These experiments employ a bacterial bioluminescence assay (Microtox TM) to determine acute toxicity of organic contaminants contained in the water soluble fraction (WSF) of waste-soil mixtures. Toxicity screening test results are used to establish a range of loading rates acceptable for use in subsequent waste-soil treatability studies. Toxicity reduction experimental results are used to determine soil detoxification potentials over time for soluble toxic organics contained in the waste-soil loading combination selected. A major factor in determining acceptability of any test procedure is whether or not different investigators can achieve reproducible and comparable results. This paper describes the proposed procedure and reports results from toxicity experiments conducted concurrently by two laboratories using aliquots from the same soil and waste samples. Comparability of results was reported to be a function of the similarity ofwaste sample aliquots used in the toxicity experiments. Toxicity screening results for uniform technical grade creosote aliquots were highly comparable between the two laboratories, while results for highly variable creosote wood preserving waste (WPC) aliquots were much less comparable. Toxicity reduction experimental results for the WPC waste also indicated significant variation between laboratories for initial (Day 0) samples; however, the same patterns of detoxification over time were observed by each laboratory with toxicity results a t the end of the experimental period (Day 42) being similar.

Hydrocarbon Biodegradation and Oil Spill Bioremediation

“…The contaminated soil is dug out and spread out in a 15-to 20-cm-thick layer. Although toxicity to microorganisms is rarely a problem in the case of hydrocarbon spills, if necessary, the contaminated soil can be "diluted" with uncontaminated soil to overcome any inhibitory effects of excessive contaminant concentrations (Matthews and Hastings, 1987). Bioremediation measures are the same as the ones described in the landtreatment of oily sludge, but since the aim is to restore the contaminated site to its "original condition," the cleanup goals are usually more ambitious.…”

“…Bioremediation accelerated both the transient increase and the ultimate disappearance of toxicity. The Microtox assay has been used also to determine treatability, i.e., a need to dilute the soil prior to bioremediation when high concentrations of toxic residues interfered with biodegradation activity (Matthews and Hastings, 1987).…”

Loss of organic chemicals in soil: Pure compound treatability studies

“…The Microtox® (Microbics Corp., Carlsbad, CA) system is a relatively simple, rapid, and inexpensive test used to screen and predict the treatability potential of waste in soil. It has been evaluated and found to be satisfactory for this purpose (Matthews and Bulich, 1986;Matthews and Hastings, 1987). Thus, in this study, the Microtox® system was used to determine the relative toxicity of the chemicals and to establish the nontoxic chemical application concentrations (loading rates) used in the experiments.…”

“…Acceptable (noninhibitory) microcosm chemical loading rates were determined with a protocol that had been proposed as part of land treatment demonstration procedures for industrial wastes (Matthews and Bulich, 1986;Matthews and Hastings, 1987). This protocol combines the leaching potential of the waste and the toxicity of the le"achate to arrive at a noninhibitory loading.…”

Microbial Toxicity in Soil Medium

“…Although the measurement of enzyme activities in soils is an effective, rapid, and cost-efficient way of measuring toxicity, the authors have recommended that dehydrogenase activity be used in conjunction with the measurement of soil respiration and enumeration of microbial cells. Matthews and Hastings (1987) used the bacterial bioluminescence (Microtox) test procedure to measure the toxicity of organic contaminants contained in the watersoluble fraction of waste-soil mixtures. Extracted samples were used to determine the toxicity of chemicals to the organism.…”