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DISCUSSION cont ~ d <br />Sodium, Calcium, Magnesium and Potassium all may contribute to <br />total dissolved solids (TDS) in an effluent. If the dissolved <br />solids were present in solution with bicarbonates, reaction with a <br />strong acid such as Sulfuric Acid would result in a solution of <br />metal sulfates that are not particularly toxic to C. dubia. <br />However, if the bicarbonates were to react with an acid such as <br />hydrochloric acid, metal chlorides may be present and extremely <br />toxic to C. dubia. Thus TDS or Sodium toxicity in the form of <br />bicarbonates may explain why the pH 3 adjustment test did not <br />remove toxicity while past titration with Sulfuric Acid did. In <br />addition, NaOH was used to raise the effluent pH in the pH 11 <br />adjustment test. It may be possible that this sodium may have <br />added to the effluent toxicity thus explaining the 20% increase in <br />mortality in the pH 11 test. <br />Further testing will be required to confirm or negate these test <br />results and their indication of TDS or Sodium toxicity in Somerset <br />• effluent. If future tests designed to identify TDS toxicity in <br />Somerset effluent are not positive, Phase I Toxicity Identification <br />Evaluation tests should continue in an effort to identify or <br />exclude any other possible toxicants. <br />-6- <br />COMMER CIAL TESTING & EN GIN EE RING CO. <br />~a n o~ Wdlerm arkeC FOi 100 ~rOlecLOn ~~~ <br />