What is the Collection System?
The City of Toledo wastewater collection system is the system of pipes and pumps that convey wastewater from homes, businesses, schools and factories to the wastewater treatment plant. Wastewater is considered to be any water that has been used for cleaning, sanitary purposes, food processing and conveying waste. In short, any water that has been used for some purpose and has become “dirty”. The collection system components include five sewer lift stations, approximately 113,000 linear feet of sewer collection pipe, 7,600 linear feet of force-main piping, and 575 manholes.
Toledo’s collection system is comprised of a network of sewer pipes and pumps. The majority of the wastewater flow is gravity; meaning that the wastewater flows downhill until it either reaches the wastewater plant or a pump station. Wastewater that flows to a pump station is then pumped to another pump station or the plant. Pipes that convey flow by gravity are called gravity mains and pipes that convey pumped wastewater are called force mains. Wastewater flows from a residence in a small pipe called a lateral. The lateral is connected to a larger pipe called a sewer main. Sometimes the sewer main is connected to a larger sewer main. These mains are all gravity mains and eventually empty into a pump station or the wastewater treatment plant. Wastewater travels from the pump station via force mains to the plant or to another pump station and then to the plant. If you looked at a map of the sewer system you would see a system much like a river system with small streams joining larger streams, those streams joining even larger streams and rivers and eventually ending at a lake or the ocean.
The wastewater collection system’s piping ranges in size from 4-inch to 18-inch, consisting of various materials including vitrified clay, terracotta, asbestos concrete, ductile iron and poly vinyl chloride (PVC). Due to the age of some materials in various stages of fatigue, ground water and surface water is often entering the collection system, causing higher than average flows at the WWTP beyond the capacity the facility is built for, thereby causing potential for the plant facility to bypass untreated wastewater to local waterways. This unwanted groundwater and surface water is known as “Inflow & Infiltration” and is often referred to as “I/I”.