Existing Treatment Process

Advanced treatment – going beyond traditional water treatment to produce a purified water that is safe for human consumption. But what makes it ‘advanced’, and what is ‘purified water’?

Before advanced treatment can occur, the water must be treated to a secondary level. Current treatment at the Pismo Beach wastewater treatment plant includes physically-driven and biologically-driven processes. The first step in the treatment process is a bar screen that physically separates solids and large debris from the flow. Then, the water flows to two oxidation ditches where it is stirred and air is introduced by mechanical aerators. In the ditches, there is aerobic microbiology that uses the oxygen introduced by the aerators to consume organic material and convert the nitrogen from ammonia to other forms that can be biologically removed from the water.

Oxidation Ditch

Then, the flow goes to two secondary clarifiers that use gravity to separate most of the remaining solid compounds out of the water.

 

Secondary Clarifier
Secondary Clarifiers

After solid settling and removal, the secondary treatment process is complete. At this point, the water has been treated to a non-potable level and can be disinfected and discharged to the ocean.

The treatment train at the South San Luis Obispo County Sanitation District (SSLOCSD) WWTP also treats to a secondary level. However, SSLOCSD’s treatment process looks a little different then Pismo Beach’s WWTP. The first step of treatment is bar screen that physically separates solids and large debris from the flow. Then, the water flows to the primary clarifier which uses gravity to separate solid compounds out of the water.

Primary Clarifier

Next, the water flowing out of the primary clarifier goes to the fixed film reactor. The fixed film reactor is a large circular basin filled with a network of plastic media. Microorganisms grow on the plastic media. As the wastewater runs through the media, the microorganisms absorb the dissolved organic matter in the water as their food supply.

Fixed Film Reactor

After the water leaves the fixed film reactor, it then goes to the secondary clarifier. The secondary clarifier does the same thing as the primary clarifier. The secondary clarifier uses gravity to separate out any remaining solids or new solids that may have formed during the fixed film reactor stage of treatment. At this point, the water has been treated to a non-potable level and can be disinfected and discharged to the ocean.

Secondary Clarifier