urban lifestyle and industrial processes produce large amounts of waste water that require treatment before being released into the environment
sewage and agricultural waste require removal of organic matter and harmful microbes
industrial waste water may require removal of organic matter and harmful chemicals
sewage treatment:
screening and grit removal removes large insoluble molecules
sedimentation occurs in a settlement tank, which has a slop
the water is allowed to stand still while heavier solids sink to the bottom creating sewage sludge and the lighter matter (called the effluent) floats to the topc
aerobic biological treatment of effluent occurs where pair is pumped into water to encourage the breakdown of organic matter and other microbes by aerobic bacteria
anaerobic digestion is used to breakdown the sewage sludge at the bottom of the settlement tank. Methane gas is produced
when there are toxic substances within waste water, it is important to include additional phases of treatment such as suing membranes, additional chemicals and UV radiation
sewage water treatment is a longer process than freshwater treatment and desalination, but uses less energy than the desalination of salt water