Development of a Zero-Headspace Aerobic Suspended Growth Bioreactor

摘要

The Department of Defense has over 12,000 sites that are contaminated from pastmilitary activities. Many site contain volatile organic contaminants that may be treated using aboveground or in situ aerobic biotreatment systems. Three oxygen sources for activated sludge were evaluated using 3-L chemostats treating amended groundwater containing over 200 mg/l benzene. The oxygen sources were compared based on percent contaminant removal, reduction of benzene off-gassing, and biomass stability. The fate of hydrogen peroxide in an activated sludge system was evaluated and described using an equation that determines steady-state hydrogen peroxide concentration. The equation is essentially a simple fate model that includes input, output, and both biotic and abiotic terms. The results indicated that peroxide could be used as an alternative oxygen source with no release of benzene into the ambient air; however, this approach was found to be expensive because of the high cost of hydrogen peroxide. Benzene was removed from the groundwater to below detection levels. Pure oxygen sparging was a particularly attractive means of introducing oxygen with minimal stripping of benzene. Biotic reactions dominated hydrogen peroxide fate within an activated sludge system. The reaction between hydrogen peroxide and biomass was second order overall and first order with respect to both reactants. Activated sludge, Hydrogen peroxide, Benzene, Zero-headspace reactor, Biotreatment.