Use of the electrolytic respirometer to measure biodegradation in natural waters

The electrolytic respirometer was used to study the biodegradation of anionic, cationic and nonionic surfactants at ppm levels in Ohio River water. Below saturation or toxic concentrations, rates of oxygen consumption for all surfactants tested were directly proportional to surfactant concentration. Respiration data were fit by iterative techniques to a non-linear mathematical model to generate estimates of the rate constants for and extent of biodegradation. Estimates of biodegradability obtained from respiratory studies agreed well with estimates obtained in carbon dioxide evolution screening studies where surfactant was used as the sole carbon source by a sewage inoculum. The data indicate that the electrolytic respirometer can be used to measure biodegradation of complex organics in natural waters when specific analytical methods or radiolabelled materials are unavailable.