Pathogens and heat
Pathogens
Sewage and wastes from animals and animal processing industries can contain very high numbers of bacteria and viruses. Some of these organisms can cause illnesses, including hepatitis and gastroenteritis.
It is important to prevent these organisms entering waters in levels that would threaten beneficial uses. A variety of disinfection techniques is available to reduce pathogen levels. EPA Publication 730 - Guidelines for Environmental Management – Disinfection of Treated Wastewater (Adobe PDF file, 198KB), provides direction on sound disinfection practices.
Heat
Thermal power stations and numerous industries use large amounts of water for in-plant cooling processes.
These cooling waters absorb great quantities of heat which can cause increased temperatures in waters to which they are discharged.
High temperatures are lethal to fish and other aquatic organisms and lesser temperature increases may impair the growth and reproduction of sensitive organisms.
Elevated water temperatures stimulate the growth of nuisance plants and algae. This and other effects can lead to decreased levels of dissolved oxygen which can threaten other aquatic life.