What is Wastewater Treatment? Ever since the first community
decided that sewers were needed, waterways have been used as the
preferred location for disposal of sewage. However, as
settlements grew, wastes inevitably overwhelmed the ability of
the waterways to assimilate the decomposing organic matter,
oxygen levels dropped and fish began to disappear. Sewage, or
wastewater treatment, evolved to remove organic matter from the
waste stream prior to discharge so that healthy oxygen levels
could be maintained. Two waste streams discharge from a
wastewater treatment plant: the liquid stream that we call
effluent, and the semi-solid slurry that we call sludge. Before
discharge, the wastewater passes through a variety of steps to
separate, filter, disinfect and "digest" both organic and
inorganic components in the waste stream. These steps are
divided up into stages, with preliminary treatment providing
only screening but no treatment, primary providing some and
secondary and tertiary providing the most advanced le