Basic steps of wastewater treatment

Sedimentation is a primary wastewater treatment step. In order to remove settle able materials, wastewater is temporarily stored in sizable sedimentation tanks. Lighter solids rise to the top with gravity whereas heavier solids sink to the bottom. To ensure that more debris is removed from wastewater, this secondary treatment process uses sand filters, contact filters, or trickling filters. Trickling filters are often the best of the three for treating small batches of sewage. The basic steps for treating wastewater are as follows:

Step 1: Pumping and Screening

A screening device filters out debris from the incoming wastewater, including rags, pieces of wood, plastic, and grease. The stuff that is taken out is cleaned, compressed, and dumped in a landfill. The following stage, grit removal, is reached after the effluent has been screened.

Step 2: Grit Elimination

Sand and gravel, two examples of heavy yet fine particles, are taken out of the wastewater treatment in this stage. Additionally, a landfill is used to get rid of this stuff.

Stage 3: Initial Settling

The material is removed using huge circular tanks referred to as clarifiers, where it will settle but more slowly than in stage two. The wastewater leaves the tank from the top as the settled material, known as primary sludge, is pumped off the bottom. Grease and other floatable particles are scraped off the top and transported to digesters with the settled material. To eliminate phosphorus, chemicals are also applied in this step.

Step 4: Aeration and Activated Sludge

The majority of the wastewater’s treatment is done in this step. The contaminants are converted into cell tissue, water, and nitrogen by microorganisms through a process known as biological degradation. This step’s biological activity is remarkably comparable to that found at the bottom of lakes andrivers, but in these areas the degradation takes years to accomplish.

Step 5: Second Settling

The treated wastewater can now be separated from the biological matter from the aeration tanks in large circular tanks known as secondary clarifiers, producing an effluent that is over 90% treated. In step four, the biology is continually pushed back to the aeration tanks from the bottom of the clarifiers.

Step 6: Filtration

The clarified effluent is polished during this phase by filtering it through polyester media with pores that are 10 microns in size. After being regularly backwashed, the plant’s head receives the material that has been trapped on the disc filters’ surface for treatment.

Step 7: Cleansing

Following the filtration process, UV disinfection is employed to ensure that the treated wastewater is almost completely free of bacteria. Remaining germs are eliminated by the ultraviolet treatment procedure to levels that comply with our discharge permit.

Step 8: Intake of Oxygen

If necessary, dissolved oxygen is added to the treated water, which is now in a highly stable state of excellent quality, to bring it up to permit levels. The treated water then enters the Oconomowoc River by way of the effluent outfall after this stage. The DNR has strict standards that must be met by the water that is dumped into the river. Removal of pollutants is kept at 98% or above.


Therefore, sedimentation of solid debris inside the water is a crucial step in the treatment of wastewater. After the major contaminants in the water have been removed, this is done. Water and pollutants are separated from waste water by passing it through a number of tanks and filters.

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