Treatment Process

Raw wastewater from throughout the Town enters the plant through three large interceptors. Septic waste (collected from Southington residences only) is discharged in with the raw wastewater.

Flow goes through aerated grit chamber, which removes rocks, sand and other inorganic debris that can interfere with the operation of our pumps.

Next, rags and other floating debris are macerated. Flow then pumped from wet well to Primary Clarifiers.


These tanks are the first step in the process. Gravity causes organics to settle. This step will remove about 35% of the solids and demand from the wastewater.

2.primary sett

Next, the wastewater is distributed across a bed of stones, called a trickling filter. Here, bacteria found naturally in the wastewater are cultivated on the stones. This bacteria feeds on the colloidal solids (the ones that won't settle out in the Primary Clarifier), thus further purifying the water.


Next is another set of clarifiers, which settle out the solids created by the trickling filter bacteria. This amount of treatment is known as secondary treatment, which removes about 80% of the solids and demand.

Next, the flow goes into the nitrification reactors. Although the bacteria cultivated in these tanks will further remove solids from the water, the main purpose of this process is to biologically convert ammonia, which is harmful to river life, to nitrate, which is not. This is done by utilizing nitrifying bacteria, also found naturally in wastewater.


This water is then sent to the final clarifiers. clar

The purified water is disinfected by Ultraviolet radiation,


and then discharged to the Quinnipiac River.


Solids which have settled out in the primary, intermediate and final clarifiers are pumped to an anaerobic digester. This tank is heated to 98 degrees F, where bacteria are again used to further break down the biosolids. Methane gas, a by-product of the digestion process, is used to heat the digester and plant buildings, saving thousands of dollars in fuel oil costs.

Finally, these solids are pressed dry and trucked to a disposal site, currently the Hartford MDC Plant.