Wastewater Treatment Process

The wastewater treatment plant receives its flow from the City of Warsaw, Town of Winona Lake, Town of Leesburg, and two mobile home parks. There is one combined sewer overflow at the intersection of Market Street and Columbia Street. The plant is permitted to treat 3.9 million gallons per day. There are two basic processes, the liquid and solid handling. 

Liquids Process Flow

  • The flow enters the plant from three main pumping stations. The flow passes through a flow meter, sampler and a fine screen to remove any large debris.
  • The flow is then divided into two oxidation ditches, each oxidation ditch contains 1.49 million gallons. The oxidation ditches provide the biological treatment of the water. Microorganisms work to remove the solids, biological oxygen demand, and ammonia.
  • The flow is then sent to a secondary clarifier. The microorganisms settle to the bottom of the clarifier and are pumped back to the oxidation ditch. The clean water flows out of the tank and goes to disinfection.
  • Disinfection is accomplished by UV lights. Disinfection is only required from April 1st thru October 31st.
  • After disinfection is post aeration. Oxygen is added to the water through floating aerators. We have a minimum Dissolved Oxygen level that we must meet per our permit.
  • Finally a sample is taken for the lab for testing. We must test 5 days per week.
Wastewater Employee Training

Solids Process Flow

  • Solids handling includes thickening, digestion, dewatering and storage.
  • The waste activated sludge (WAS) is diverted to a gravity belt thickener.
    The thickened sludge is then pumped to a digester.
  • The sludge is aerated and remains in the digester for 3 weeks. The sludge is then pumped to a gravity belt press.
  • The press removes excess water and produces what is called a cake.
  • The cake is stored in a building until it is loaded out. The cake is either land applied on farm ground or taken to the landfill if farm ground is not available.
Wastewater Line

Pre-Treatment Operations

Publicly-owned treatment works (POTWs) collect wastewater from homes, commercial buildings, and industrial facilities and transport it via a series of pipes, known as the collection system, to the treatment plant. Generally, POTWs are designed to treat domestic sewage only, creating the need for a pretreatment operations program. 

The typical POTW treatment process consists of primary and secondary treatment, along with some form of solids handling. Primary treatment operations include screening and settling, whereas secondary treatment removes organic contaminants using microorganisms to consume biodegradable organics. 

Limitations of POTWs

As noted, POTWs are not designed to treat toxins in industrial waste. As such, discharges from both industrial and commercial sources can cause serious problems. The National Pretreatment Program, published in Title 40 Code of Federal Regulations (CFR) Part 403, provides the regulatory basis to require non-domestic discharges to comply with pretreatment standards to ensure that goals are attained. The objectives of the National Pretreatment Program are to: 

  • Improve opportunities to recycle and reclaim municipal and industrial wastewaters and sludges
  • Prevent the introduction of pollutants into POTWs, which will interfere with the operation of a POTW, including the interference with its use or disposal of municipal sludge
  • Prevent the introduction of pollutants into POTWs, which will pass through the treatment works or otherwise be incompatible with such work


The Wastewater Treatment Utility maintenance personnel are responsible for the regular upkeep of sewer and stormwater infrastructure throughout Warsaw. In addition to accepting all of the wastewater from the municipal residents, the Wastewater Treatment Utility is also responsible for the handling of the town of Leesburg’s waste. 

With over 50,000 feet of either sanitary, storm, or combined sanitary and storm pipelines, the maintenance personnel perform vital operations to help ensure the proper functioning of Warsaw’s sanitary system. Regularly cleaning pipelines, performing pipe locates prior to construction, maintenance of over 40 lift stations, and the repair and replacement of infrastructure are just a few of the many hats that the Wastewater Treatment Utility personnel wear. 

Employee working with manhole

Lab Operations

The Warsaw Wastewater Laboratory's primary task is to test the influent and effluent water and report the results to the Indiana Department of Environmental Management (IDEM) in order to demonstrate that the utility is removing pollution before discharging to public waters. 

Additionally, tests are performed on treatment process controls for the plant while also testing for the Stormwater Program. Tests are performed on all biosolids that are applied to farm fields in the area. The Tippecanoe River and Walnut Creek are also monitored above and below outfalls for pollutants. 

The Warsaw Wastewater Laboratory has earned the Laboratory Excellence Award yearly since 2003 and has passed all Discharge Monitoring Report Quality Analysis evaluations as required by the State of Indiana since 2004.