Treatability and toxicity of nonylphenol compounds in anaerobic batch reactors

Bozkurt, Hande
Nonylphenol (NP) and its ethoxylates are used in formulation of pesticides and detergents, production of personal care products and many industrial sectors such as textile, metal plating, plastic, paper and energy. They are also used in the formulation of household cleaning agents. Industrial uses in the production line make up 55% of the total use; whereas industrial and domestic cleaning processes constitute 30 and 15%, respectively. Since they are widely used in industry and households, NP compounds enter the environment mainly by industrial and municipal wastewater treatment plant effluents. NP is considered strongly toxic and has adverse effects even with short term exposures. Moreover, with its similarities to natural hormones, NP and its ethoxylates are considered as endocrine disrupter compounds. In studies conducted with human cells, chicken embryo, trout and mice eostrogen receptors, positive responses were observed. Due to their lipophilic and hydrophobic characteristics they accumulate in cells, tissues and organic materials such as sludge. For these reasons, fate of NP and its v ethoxylates in wastewater treatment plants and in sludge treatment processes gained importance. Nonylphenol polyethoxylates (NPnEO) are degraded in microbial media and lose their ethoxylates to nonylphenol diethoxylate (NP2EO), nonylphenol monoethoxylate (NP1EO) and NP. Moreover, nonyl phenoxycarboxylic acids (NPnEC) can be formed during some of these reactions. Because the first degradation reactions are fast, concerns and studies are focused mainly on NP2EO, NP1EO, NP, NP1EC and NP2EC. Even though these general degradation information is available, studies on sludge are very rare. In this study, treatability and toxicity of NP2EO in anaerobic batch reactors is investigated. First, with the use of Anaerobic Toxicity Assay (ATA) test, toxic doses of NP2EO which was added to the reactor as the parent component, were determined. Moreover, the degradation of these chemicals were studied in larger scale batch anaerobic digesters. The aim of this part was to observe the degradation patterns and products. Throughout the study the fate of NP and its ethoxylates was followed in aqueous and solid phases by the use of Gas Chromatography / Mass Spectrometry system (GC/MS). ATA tests showed that NP2EO was not toxic to anaerobic microorganisms at the doses investigated in this study. It was rather stimulating and caused an increase in methane production in the reactors. On the other hand the spiked NP2EO’s at 0.5 and 2.5 mg/L concentration were completely degraded in the larger scale batch reactors. At the same time, an increase in the concentrations of NP and NP1EO was observed which supported the fact that NP2EO was degraded into NP1EO and NP under anaerobic conditions. Abiotic degradation was not observed.
Citation Formats
H. Bozkurt, “Treatability and toxicity of nonylphenol compounds in anaerobic batch reactors,” M.S. - Master of Science, Middle East Technical University, 2011.