APPLICATION OF RESPIROMETRIC BIODEGRADABILITY TESTING PROTOCOL TO SLIGHTLY SOLUBLE ORGANIC-COMPOUNDS

Electrolytic respirometry was used to measure the biodegradability of six phthalate esters (dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, di-n-octyl phthalate, butyl benzyl phthalate, and bis[2-ethylhexyl]phthalate) and four polynuclear aromatic hydrocarbons (naphthalene, phenanthrene, anthracene, and 1,2-benzanthracene). Mineralization occurred for all compounds except anthracene and 1,2-benzanthracene. Determination of all parameters describing biodegradation (mu, K(S), Y, and b) was possible when a compound was present at a concentration below its solubility limit, but estimates of K(S) could not be made with higher concentrations. A modified parameter estimation routine that considered solubility was unsuccessful. Dissolution appeared to govern the degradation rate of compounds present in amounts exceeding their solubility, suggesting that the physical state of such compounds is an important characteristic governing biodegradation.