Toxicity Testing of Solidified Waste Leachates with Microbiotests
Abstract : Solidification is a process for treating contaminated wastes that reduces or entirely prevents the release of hazardous waste compounds into the environment. This process aims to make materials either not harmful nor toxic at all or at least less hazardous than the raw waste. The most widely used basic materials for solidification are cement, lime, fly ash, and blast-furnace slag. No toxicity data are available for these materials. This contribution describes the partial results of an experimental study dealing with the toxicity testing of 2 types of cement, fly ash, and blast furnace slag. Samples of the test materials were solidified and then pulverized by crushing. The specimens were leached before and after solidification by a 2-step procedure according to the CEN standard. Deionized water acidified to pH 3.5 was used as the leaching solution. All the leachates were tested for toxicity using microbiotests with crustaceans (Thamnotoxkit F™), algae (Algaltoxkit F™) and bacteria (Toxi-ChromoPad™). The heavy metals in the solid materials and leachates were measured. The study demonstrates the short- and long-term leachability of metals from some materials commonly used for solidification with the corresponding toxicity of the leachates; it also indicates the toxicity levels of the raw materials. The results of the leaching tests followed by ecotoxicological analyses provide information on the stability of the solidified waste and on the significance of the solidification technology for the protection of the environment.