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Treatment Process
Water treatment diagram Steps for Wastewater Treatment
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 through the physical processes of sedimentation and flotation. Raw sewage flows into primary treatment devices referred to as sedimentation tanks or primary clarifiers, where heavier material will settle out and the lighter constituents will float to the surface. A range of between 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, including dissolved solids, are usually be biochemically treated in additional 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.

Learn more about the treatment process.