Task 1. Biodenitrification of low nitrate solar pond waters using sequencing211 batch reactors. Task 2. Solidification/stabilization of high strength and 211 biodenitrified heavy metal sludges with a Portland cement/flyash system

摘要

Process wastewater and sludges were accumulated on site in solar evaporation211u001eponds during operations at the Department of Energy's Rocky Flats Plant (DOE/RF). 211u001eBecause of the extensive use of nitric acid in the processing of actinide metals, 211u001ethe process wastewater has high concentrations of nitrate. Solar pond waters at 211u001eDOE/RF contain 300-60,000 mg NO(sub 3)(sup (minus))/L. Additionally, the pond 211u001ewaters contain varying concentrations of many other aqueous constituents, 211u001eincluding heavy metals, alkali salts, carbonates, and low level radioactivity. 211u001eSolids, both from chemical precipitation and soil material deposition, are also 211u001epresent. Options for ultimate disposal of the pond waters are currently being 211u001eevaluated and include stabilization and solidification (S/S) by cementation. 211u001eRemoval of nitrates can enhance a wastes amenability to S/S, or can be a unit 211u001eoperation in another treatment scheme. Nitrate removal is also a concern for 211u001eother sources of pollution at DOE/RF, including contaminated groundwater 211u001ecollected by interceptor trench systems. Finally, nitrate pollution is a problem 211u001eat many other DOE facilities where actinide metals were processed. The primary 211u001eobjective of this investigation was to optimize biological denitrification of 211u001esolar pond waters with nitrate concentrations of 300--2,100 mg NO(sub 3)(sup 211u001e(minus))/L to below the drinking water standard of 45 mg NO(sub 3)(sup (minus))/L 211u001e(10 mg N/L). The effect of pH upon process stability and denitrification rate was 211u001edetermined. In addition, the effect Cr(VI) on denitrification and fate of Cr(VI) 211u001ein the presence of denitrifying bacteria was evaluated.