Domestic sewage is a major threat to receiving waters throughout the world. In Canada, a high proportion of the population (81%) is served by municipal wastewater treatment facilities. Nevertheless, discharges from wastewater treatment plants, stormwater sewers and combined sewers have caused adverse impacts on some lakes, rivers and coastal waters. The most publicly recognized impacts are shellfish harvesting restrictions and beach closures resulting from microbial contamination. Habitat degradation and contamination also occur and these, in turn, have altered the abundance and diversity of aquatic organisms. Our findings on the effects of municipal wastewater discharge suggest that there is a need to review sewage treatment requirements in Canada. Further research is also required on the interactive and cumulative responses to habitat degradation and to long-term exposure to persistent and bioaccumula-tive pollutants. Finally, an integrated approach to wastewater management is needed that addresses loadings from treatment plants, stormwater sewers, combined sewer overflows and other wastewater sources.

No abstract

No abstract

Carbofuran is an insecticide widely used in North America. Its relatively short halflife in the environment has been a major factor in its increased use and substitution for insecticides known to persist in the environment for long periods of time and accumulate in animal tissues. The relatively high water solubility of carbofuran coupled with its relatively low adsorption on soils and sediments permits natural surface waters to become a repository for excessive amounts of the insecticide escaping treated areas or being accidentally introduced hito aquatic environments. Carbofuran's persistence is directly related to the pH of the water. The compound is stable in acid waters, but subject to increasing chemical hydrolysis as the water becomes more alkaline. Microbial populations in water, sediments, and flooded soils also reduce the persistence of carbofuran. Carbofuran is very toxic to fish. Generally, fish LC 50 S for carbofuran are below 1 mg/l. While accidental spraying of carbofuran poses a threat to the aquatic environment, a more serious threat is the carbofuran in runoff water from fields or orchards immediately after treatment. Localized fish kills have been reported in such instances.

No abstract