The treatment plant began operations in September 1980. Costing $17 million, the plant presently treats in excess of five million gallons of wastewater per day and is designed for an average daily flow of nine million gallons. This capacity is sufficient to serve a residential population of 48,500 and allow for additional industrial expansion. The plant was constructed with 75 percent federal funding and 25 percent state and local funds.
Many components of the previous treatment plant were incorporated into the new facility. Providing clean water for the West Bend area at the lowest cost.
The wastewater treatment plant uses a combination of processes to achieve the required degree of treatment. Physical, chemical, and biological systems remove impurities from the wastewater producing an effluent, which is 99+ percent pure water. Wastes (sludge) removed from the water are concentrated, stabilized, and removed to a landfill or used as fertilizer on farm fields.
Wastewater from homes and industry enters the treatment plant via a 54-inch pipe nearly 23 feet below the ground. Large debris is removed from the wastewater in the first treatment stop by two automatic bar screens. Small, heavy solids such as sand and coffee grounds are settled and removed in two grit chambers following the bar screens.
The wastewater is then pumped to the far north end of the plant by five large pumps with a total capacity of 26,000 gallons per minute.Two large settling tanks, called primary clarifiers, settle by gravity and remove about 60 percent of the suspended organic particles (sludge). The addition of chemicals prior to the clarifiers also provides removal of the nutrient phosphorus in the settled sludge.
The wastewater is pumped to the top of the trickling filter. These two large towers, which are the most visible elements of the treatment plant, contain a honeycomb of plastic covered with a slime of microorganisms (bugs). As the wastewater passes over these bugs, they feed on the suspended and dissolved organic wastes, converting them to oxygen and water. The microorganisms continuously grow and eventually are washed out of the towers. A pair of secondary clarifiers settle and remove these slimes.
The wastewater makes the remainder of the trip through the plant by gravity. After the secondary clarifiers, the wastewater flows to the nitrification aeration basins. In this process, air (oxygen) is injected into the wastewater; microorganisms use the oxygen to remove the remaining organic wastes and convert the ammonia to a stable form of nitrogen. Four final clarifiers settle the microorganisms, some of which are returned to the aeration basins while the rest are removed.
The wastewater is very clean by this point. To remove the remaining small particles the wastewater flows through a filter of sand and coal. Following filtration, hypo-chloride is added to disinfect the water by killing any disease-causing bacteria. The water is again aerated, if necessary, to raise the oxygen level prior to discharge to the Milwaukee River. When discharged, the water contains less than five parts per million of organic waste and solids.
The sludges removed from the clarifiers are combined and thickened prior to digestion. The four anaerobic (without oxygen) digesters are covered tanks where the sludge is heated and mixed. Microorganisms growing in this environment convert the unstable organic wastes to methane gas. The gas is used as fuel to heat the digesters. The stabilized sludge is converted by a semidry cake by processing on vacuum filters and trucked to a landfill or hauled as liquid for spreading on agricultural land for fertilization.
Residents of the West Bend area can be proud of this fine wastewater treatment facility. The high quality of discharged effluent is evidence of the positive action that has been taken to restore and maintain the chemical, physical, and biological integrity of the waters of the Milwaukee River – action that is part of a national commitment to clean water.