Design Parameters for Single-Species Toxicity Tests

4 Design Parameters for Single-Species Toxicity Tests 

Besides the complexity of the biological system and the length of the test, there are more practical aspects to toxicity tests. In aquatic test systems the tests may be classified as static, static renewal, recirculating, or flow-through. 

The next step in complexity is static renewal. In this exposure scheme, a toxicant solution is replaced after a specified time period by a new test solution. This method has the advantage of replacing the toxicant solution so that metabolic wastes can be removed, and toxicant and oxygen concentrations 

A recirculating methodology is an attempt to maintain the water quality of the test solution without altering the toxicant concentration. A filter may be used to remove waste products or some form of aeration may be used to maintain dissolved oxygen concentration at a specified level. The advantage of this system is the maintenance of the water quality of the test solution. Disadvantages include an increase in complexity, an uncertainty that the methods of water treatment do not alter the toxicant concentration, and the increased likelihood of mechanical failure. 

---