A system for reconstituting special water qualities for use in chronic toxicity studies

A water treatment system and procedure are described that are designed for preparing large quantities of reconstituted water with specific chemical and physical characteristics for use in chronic toxicity studies with fish and invertebrates. Water treatment units produce high-purity water in large quantities for storage in high-density cross-linked polyethylene tanks, where it is combined with various salts to reconstitute an appropriate experimental water quality that simulates potential environmental conditions for use as the test medium in an intermittent-flow proportional diluter. Several water quality characteristics for the source water and the receiving water, and respective flow rates must be considered when one calculates the chemical constituents that must be added to closely simulate the water in a potential environmental situation. The water treatment system and procedure have been used to produce four differently reconstituted experimental waters that were used in 60- to 90-day early life stage chronic toxicity studies with fish. Of the ten water quality characteristics measured in the experimental waters during the studies, eight had a coefficient of variation of <5%-indicating that the various physiochemical characteristics could be precisely reproduced throughout long-term exposure studies.