Low Water Hardness Research Articles

The effects of hardness, alkalinity and pH of test water on the toxicity of copper to rainbow trout ( Salmo gairdneri)

1. 1. Rainbow trout were used to determine the effects of water alkalinity and hardness on the incipient lethal concentration (ILC) of copper. 2. 2. At low water hardness (12 ppm) the ILC of copper was not affected by a five-fold change in medium alkalinity (10–50 ppm); however in hardwater (98 ppm) the same change in alkalinity caused the ILC to increase by 1.8 times. 3. 3. The ILC for copper increased as hardness increased regardless of alkalinity. 4. 4. At pHs of less than 5.4 the toxicity of various combinations of copper and hydrogen ion were antagonistic but at pH 5.4 there appeared to be some synergism between pH and Cu toxicity.

BACTERIOLOGICAL EVALUATION OF QUATERNARY AMMONIUM COMPOUNDS ALONE AND IN DETERGENT FORMULATIONS

Using Escherichia coli as test organism, three quaternary detergent-sanitizers and their constituent QACs were evaluated by modified glass slide and Weber and Black methods at 5°, 20°, and 45°C in artificial hard and distilled waters. QAC activity was reduced by low temperature and water hardness, the latter exerting the greater effect. Each detergent product was more effective than its constituent QAC component alone. Reasons for the earlier endpoints obtained with glass slide method are discussed.