Treatment Process
Health & Safety
| Treatment Process
| Testing | Regulation
| Water Quality
There are several processes that wastewater must go
through before it becomes recycled water. The major treatment processes
are as follows:
Primary Treatment—This process
is designed to remove organic and inorganic solids by the physical processes
of sedimentation and flotation. Raw sewage flows into primary treatment
devices referred to as sedimentation tanks or primary clarifiers, where
the material that is denser than water will settle out and the material
that is less dense than water will float to the surface. Approximately
40-60% of the suspended solids and 25-35% of the biochemical oxygen demand
(BOD) are removed from the waste stream. The solids that remain in suspension
as well as dissolved solids will usually be biochemically treated in subsequent
processes for physical separation and removal.
Secondary Treatment—The effluent
from primary treatment contains extremely fine organic and inorganic solids.
Secondary treatment consists of unique biological systems designed to
remove BOD, suspended solids and some dissolved solids through a biological
conversion of these materials to a settleable form. The biomass is then
separated from the product water (secondary effluent) in a secondary or
final clarifier. Secondary treatment systems typically remove 80-95% of
suspended solids and BOD.
Tertiary Treatment—This is the
polishing process that filters the treated water through fine sand or
other granular material to remove fine suspended solids. The water is
then chlorinated for disinfection.
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