WWTP Process Descriptions

Click here for a map of the process flow diagram.

Preliminary Treatment

The initial treatment process for most systems, it consists of automatic bar screens to remove large debris and rags and aerated grit tanks for sand/grit removal.

Primary Treatment

A physical treatment technology, it consists of 5 large tanks in which a portion of the wastewater’s contaminants are allowed to settle out and be removed from the wastewater.

Secondary Treatment

The heart of any treatment system, the aerated biological nutrient removal system uses helpful microbial organisms to remove and breakdown the contaminants and nutrients in the wastewater. Supplying diffused air in portions of the system and not in others allows the system to select differing microorganisms to remove different contaminants.

Final Settling Tanks

Large circular settling tanks allow the aerated solids from the secondary treatment system to separate from the water. A portion of the solids are returned to the secondary treatment system as seed organisms, the rest is removed. Clean water exits the tanks for further treatment.

Solids Handling

Settled solids from the primary treatment system and the final settling tanks is collected, thickened to remove excess water, (which is retreated in the system) and removed to offsite locations for disposal.

Disinfection and Dechlorination

A strong bleach solution (sodium hypochlorite) is used to kill any remaining organisms in the water from the final settling tanks. A second chemical (sodium bisulfite) is then used to neutralize the bleach prior to the now completely clean water’s discharge to the Norwalk River.