|
Wastewater
treatment uses microbes to decompose organic matter in sewage.
If too much untreated sewage or other organic matter is added to
a lake or stream, dissolved oxygen levels will drop too low to
support sensitive species of fish and other aquatic life.
Wastewater treatment systems are designed to digest much of the
organic matter before the wastewater is released so that this
will not occur. There are not any more easy method for treatment systems.
They use physical, chemical, and
biological processes:
- Primary waste water
treatment physically removes large solids using grates,
screens, and settling tanks.
- Secondary
wastewater treatment promotes growth of bacteria and
other microbes that break down the organic wastes. These
biodegradation processes also take place in streams, lakes,
and oceans, but the purification systems in nature can
easily be overloaded with input of too much organic waste.
Secondary treatment prevents this type of pollution by
degrading most of the organic matter before the water is
released into the environment.
- Tertiary wastewater
treatment is used only where it is needed to protect the
receiving waters from excess nutrients. In tertiary
treatment, the concentrations of phosphorus or nitrogen are
reduced through biological or chemical processes.
- Disinfection
kills disease-causing organisms, most commonly through
chlorination.
Sludge,
the collection of solids that are removed during wastewater
treatment, requires processing to reduce odor and water content.
Depending on the disposal method, the sludge also may undergo
treatment to decompose organic matter or kill disease-causing
organisms |