BIODEGRADATION OF AN INHIBITORY NONGROWTH SUBSTRATE (NITROGLYCERIN) IN BATCH REACTORS

Biodegradation of nitroglycerin (NG), an inhibitory, nongrowth substrate present in a multicomponent munition wastewater, was investigated in a pilot-scale batch reactor operated with both aerobic and anoxic cycles. A mixed culture was initially acclimated by gradual introduction of NG into influent and subsequently exposed to actual NG-laden production wastewater. System performance revealed that NG was amenable to aerobic biodegradation without adverse impact on removal efficiencies of other pollutants. Temporal NG concentration profiles indicated that an influent concentration of approximately 200 mg/L of NG was reduced to below detection limits in less than 5 h of aeration with no appreciable (<4%) biosorption. Failure of NG-acclimated cultures to utilize NG as a sole carbon source in bench-scale reactors suggested that NG behaved as a nongrowth substrate and its degradation possibly occurred by cometabolism. Ethyl acetate present in the waste stream was an adequate growth substrate in terms of both biological and physicochemical properties. High concentrations of NO3-N, produced as a result of aerobic degradation of NG and other nitrogenous compounds of the waste, were treated in an anoxic phase. Approximately 95 mg/L of NO3-N was denitrified to below detection limits in 5 h of anoxia without the addition of external carbon sources. Two SBR cycle schemes with different static-fill times exhibited significant differences in treatment efficiencies.