This paper summarizes the findings of our studies on mercury stabilization using sulfide. Primary stabilization variables such as stabilization pH and sulfide/mercury molar ratio were tested. Mercury stabilization effectiveness was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) and the constant pH leaching tests. The influence of interfering ions on mercury immobilization was also tested. The experimental results indicate that the sulfide-induced treatment technology is an effective way to minimize mercury leaching. It was found that the most effective mercury stabilization occurs at pH 6 combined with a sulfide/mercury molar ratio of 1. The combined use of increased dosage of sulfide and ferrous ions ([S]/[Hg]=2 and [Fe]/[Hg]=3 at pH=6) can significantly reduce interferences by chloride and/or phosphate during sulfide-induced mercury immobilization. The sulfide-treated waste stabilization efficiency reached 98%, even with exposure of the wastes to high pH leachants.

A fragment constant model for prediction of K OC was developed and evaluated with a diverse database of 592 chemicals belonging to 17 classes. The range of experimental K OC covered 7.65 log-units. The 592 chemicals were randomly divided into a training set and a testing set for model development and validation. A general model was then established using the entire database having 74 fragment constants and 24 structural factors. Statistically, the regression model accounted for as much as 96.96% of the variation in the measured log K OC . The mean residual between the experimental and predicted K OC values was 0.366 log-units. In more than 74% of the chemicals studied the residual values were less than 0.5 log-units. The robustness of the regression model, with respect to either specific individual chemicals or particular compound classes, was evaluated through use of jackknife tests. The experimental results confirmed the ability of the fragment model to predict K OC for a wide variety of untested chemicals.

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Because of their small size, Cryptosporidium oocysts cannot be easily filtered from water. This study evaluated the use of surrogates for measuring the microbial treatment performance of two point‐of‐use devices incorporating filtration with electrostatic charge interaction mechanisms. Both systems were challenged with Cryptosporidium oocysts (4‐6 μm), Bacillus subtilis (B. subtilis) spores (~1.2 μm), polystyrene latex (PSL) beads (~ 3 μm), Escherichia coli, and MS2 bacteriophage. The target biological contaminants were more effectively removed than the PSL beads, and the smaller B. subtilis spores mimicked Cryptosporidium oocyst removal more closely than the ~ 3‐μm PSL beads. Thus, surface charge appears to be an important factor for microorganism attachment, and B. subtilis spores should be considered a more appropriate surrogate than PSL beads for evaluating Cryptosporidium movement through charged media. For noncharged devices, PSL beads may still be useful as a surrogate for Cryptosporidium.

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