Oxygen levels required to decompose this waste is called biological oxygen demand .a large amount of biological oxygen demand is required to decompose industrial wastes and because of their profit maximization motive the opt dispose in water to reduce cost of treatment. The wastes when directed to water bodies always have catastrophic effects on marine and human life.
The second type of pollutant is excessive nutrition. This is common in agricultural where agricultural runoffs and non biodegradable detergents contaminate water. This facilitates growth of phytoplankton. The autophication process results in large dissolved oxygen from photosynthesis during the day and over utilization of oxygen for respiratory purposes during the night. This causes deficiency of oxygen in water leading to massive death of aquatic animals.
Suspended solids are also another type of pollution in this 21st century. This is prevalent where land has been disturbed by plowing or excavation. Ground up wood fibers can also be classified in this category of suspended solid pollution.
There are over 65000 industrial chemicals in use in the modern world .3-5 new chemical s enter the market every day .the major classes of chemicals which are harmful and find their way through to water sources are ammonia, petroleum hydrocarbons, pesticides, and detergents.(Heath A.G,1995)
Another type of water pollution is microbiological pollution. This is natural form of pollution caused by microorganisms. They include e bacteria, viruses and protozoa. They are the major cause of illness in human being and animals. (Canter w. L and knot 1985)
Human activities have negative impact and contribute greatly in water pollution. Industrial waste form the largest percentage of water pollution .nuclear waste produced from industrial, medical and scientific process that use radioactive materials can be very harmful when they find they way to water