Feasibility of intermittent biological treatment for hazardous wastes

During an investigation and evaluation of a former hazardous waste facility, groundwater underlying the site was found to be highly contaminated by a variety of hazardous organic substances. An intermittently biological treatment process coupled with activated carbon adsorption was identified as a promising on‐site alternative. Because the operating constraints and degree of treatment achieved by biological processes subjected to very infrequent operation were unknown, a pilot study was initiated to assess the technical feasibility of the proposed process. Based on the findings of the experimental study, intermittent biological treatment can achieve significant removal of waste pollutants. The rate of COD removal was found to be adversely affected by decreases in operation frequency and decreased operating temperatures. However, all biodegradable COD was removed within a react period of 24 hrs., despite lag periods as long as three weeks between operation. Addition of powdered activated carbon was tested under one operating scenario and is hypothesized to be advantageous in reducing aeration times for conditions of low temperature and extended lag periods.