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DISCUSSION <br />Based on the results of the Preliminary Toxicity Investigation <br />conducted in 1992, it has been demonstrated that outfall 011 <br />effluent toxicity may have been primarily due to high Total <br />Dissolved Solids (TDS) content comprised mainly of sodium bi- <br />carbonate. Those cations and anions that are identified as <br />"solids" (Na, K, Ca, Mg, C1, SO4 and HCO~), and their presence at <br />concentrations as determined by analytical analyses, also suggests <br />that sodium and bi-carbonate exists in the effluent at high <br />concentrations. <br />In addition to that above, results of the Toxicity Identification <br />Evaluation conducted in August, 1995, showed that effluent 011 <br />toxicity to Ceriodaphnia dubia was reduced in some of the tests. <br />Furthermore, the following test observations may be indicative of <br />TDS toxicity due to sodium bi-carbonate. (Refer to Table 1.): <br />* pH adjustment Test - Toxicity is reduced by lowering the <br />effluent pH. Adjustment to pH 11 did not significantly reduce <br />toxicity, indicating that toxicity due to some heavy metals, <br />solids such as calcium and magnesium sulfates, was not <br />present. No precipitate was observed at pH 11. <br />* Filtration Test - Survival was not increased significantly <br />with filtration at normal pH or pH 3. <br />* Aeration Test - No significant increase in survival was <br />observed following aeration of 100$ effluent and aerated <br />effluent adjusted to pH 3. This suggests that volatile and <br />semi-volatile organics are unlikely to be present at toxic <br />levels. <br />* Analytical Analyses - Effluent alkalinity was 1940 mg/L. TDS <br />was calculated at 3,227 mg/L. Effluent conductivity was 3400. <br />* EDTA & Sodium Thiosulfate Titration - Effluent toxicity was <br />not reduced by EDTA chelation and Oxidant/Reduction tests. <br />Toxicity due to heavy metals or easily oxidized toxicants were <br />not indicated. <br />* Solid Phase Extraction - C1B filtration does not significantly <br />decrease toxicity in relation to other pH adjustment tests. <br />Toxic organics are unlikely. <br />6 <br />COMMERCIALTESTING & ENGINEERING CO. <br />F~66 L~~ <br />OApinal Watermarkeo For Vour Protenlon ,,. - <br />