Due to its very reactive nature, chlorine dioxide is rapidly (in a few hours) reduced to chlorite, which is persistent also as a biocide but 16 times less toxic to fish, according to MATC. Therefore, it is much more likely that fish will be exposed to chlorite than to chlorine dioxide in natural waters. Presently accepted, the Maximum-Permitted-Concentration of total residual chlorine (TRC) in waste-water discharging into receiving waters is 0.6 mg/l. If this requirement will not be exceeded, it is unlikely that fish would be exposed to lethal or even to sublethal concentrations of chlorine dioxide or chlorite. Furthermore, chlorine dioxide does not generate toxic nitrogenous (chloramines) or carcinogenic organic residuals (trihalomethanes). All these properties make chlorine dioxide a more promising biocide than chlorine.

No abstract

No abstract

In this study the effect of crude oil on intestinal bacterial populations of the mollusk Viviparus contactus was investigated. The addition of crude oil into an environment of mollusks induced no clear changes in the saprophytic, amylolytic, and total coliform bacterial counts in the digestive tract of the mollusk. After 10 days of contamination, the saprophytic, amylolytic, and total coliform bacterial numbers were of the same order of magnitude as the initial numbers. Significant numbers of indigenous hydrocarbon-degrading bacteria were observed in the intestinal tracts of mollusks before contamination with crude oil. Introduction of crude oil into the mollusk environment resulted in an increase of 2 orders of magnitude in the number of hydrocarbon-degrading bacteria in the digestive tract. Therefore, measuring the hydrocarbon-degrading bacterial populations in the digestive tracts of hydrobionts can be considered an important component of contaminated-site assessment studies.

No abstract