Toxicity reduction evaluations (TREs) typically build upon the results of TIEs in that the TRE focuses on reducing concentrations of the toxicant of interest. This may be through source control that optimizes usage concentrations, switching to an effective but less toxic alternative, optimizing current treatment processes to more thoroughly treat the toxicant of interest, or adding additional treatment technologies to reduce toxicant concentrations. The ideal treatment should be robust, cost-effective, and have limited downside in terms of environmental hazards or human health risks. In some cases, TREs may be implemented in the absence of a TIE, where broad classes of treatments are applied to see which ones eliminate toxicity, and then the most effective is applied. However, this is seldom the most cost-effective solution in that the treatment is not optimized for the actual toxicantt. For example, activated carbon removes both metals and organics; however, if the actual toxicant is a metal, there are more cost-effective methods for treatment than carbon, because the carbon has relatively poor affinity for metals and needs frequent replacement due to break- through.
In most cases, Nautilus has worked with engineers and plant operators to optimize the treatment/source control options with respect to the particular toxicant and site in question. Often the most efficacious solution is simply application of good housekeeping practices to target emissions of the contaminant of interest.
In the larger picture, an effective TRE may be a combination of source control, treatment, and even education of the public (if the sources are diffuse throughout a given service area). Nautilus is available to advise on such programs, as well as to design monitoring programs to evaluate the effectiveness of any TREs implemented. Such monitoring programs are often an integral part of TREs in that they provide a basis for adaptive management and optimization of the TRE over time.