Abstract
Thiosalts are products of incomplete oxidation of certain types of sulphide minerals and can form in metallurgical processes, tailings facilities, and wasterock piles. When present in wastewater, thiosalts are known to either cause or contribute to aquatic toxicity. Since aquatic toxicity is often a complex issue where multiple water quality parameters and/or constituents can be involved in rendering effluent toxic in standard LC50 Daphnia magna and rainbow trout tests, it is important to first clearly establish the role of thiosalts in effluent toxicity and explore mitigation that would not require treatment prior to implementing a new water treatment system. If/when thiosalts role is established, on-site pilot programs need to be performed to support the decision on which treatment method is to be used because this decision if often site-specific, and also to establish the engineering design basis. One of the main challenges in establishing both toxicity thresholds and treatment efficiency is the ability to measure thiosalts quickly and reliably on fresh samples of feed and treated effluent directly on site. Shipping samples to commercial labs is not a viable option. This presentation will provide an overview of a thiosalts mitigation program including: 1) establishment of thiosalts concentration thresholds causing toxicity, 2) development of reliable field measurement of thiosalts, and 3) highlight of results of two pilot programs to support treatment method selection.