TOXICITY REDUCTION OF ONTARIO-HYDRO RADIOACTIVE LIQUID WASTE

The radioactive liquid waste (RLW) system in Ontario Hydro's pressuris ed heavy water reactors collects drainage from a variety of sources ra nging fmn flea drains to laundry waste. RLW effluent was intermittentl y toxic to rainbow trout and Daphnia magna during the first phase of O ntario's Municipal Industrial strategy for Abatement (MISA) Program, a pparently a a result of the interaction of a variety of known nd unkno wn organic and inorganic compounds. Accordingly, we employed a treatme nt-based approach to reducing its toxicity, supplemented by chemical a nalysis. TWO series of toxicity reduction tests were conducted The fir st series explored the potential for sorption of the possible toxicant s, while the second series incorporated a wider variety of treatments. Of the 24 samples in the first test series, 17 were toxic (D. magna m ortality greater than or equal to 50%). Of the toxic samples, only 7 o f 17 were still toxic after passage through an activated carbon column , but 5 of 6 samples tested remained toxic after passage through a mal l chelating rain column. In the second series, it lust one of the trea tments war effective in reducing toxicity of ill samples which were in itially toxic (16 of 24 ampler), bur no one treatment war effective fo r all toxic samples. Three treatment (UV/H2O2 photo-oxidation with pri or pH adjustment, or passage through a column of either a non-function alized (N-F) ruin or a mixture of N-F resin and a weak base (W-B) anio n exchange rain), were effective in reducing the toxicity of more than 50% of the toxic sampler; yet roughly 25% of there samples remained t oxic after treatment O-2 sparging, UV/H2O2 photo-oxidation without pri or pH adjustment, md passage through I column of the W-B Resin were la s effective, or more than 50% of the samples remained toxic after trea tment. Filtering war not effective, a all of the treated ampler (9/9) retained their toxicity. There was no obvious correspondence between t oxicity and the concentrations of metals (Cu, Zn Fe, Al and Cd) nor we re my simple relationships apparent between toxicity and Total Organic Carbon or NH3, concentrations. At stations where radioactive liquid w astes am segregated, toxicity was also segregated, suggesting that we may be able to address the problem It source through a combination of Best Management Practices and smaller rule treatment facilities.