May Tour History
Eighteen people attended the May 29th tour of Fort Wayne's wastewater treatment plant on Dwenger Avenue. This plant has been steadily expanded over the last ten years to accommodate combined sewage and regional economic development. The combined sewage is increasingly being diverted to the treatment plant instead of flowing into rivers. Current overall capacity is 72 million gallons/day, soon to be 85 million. Extra digesters were built, equivalent to 120 million gallons/day, to allow long-term maintenance of digesters and clearing of sediments throughout City Utilities' sewer system. Two ponds across the river can provide hundreds of millions of gallons of wastewater storage during major storm events.
Solids larger than a quarter inch are removed from wastewater entering the plant by passing through screens resembling a bank of massively robust bicycle chains. These cycle upwards to carry away and dump large solids including animal fats (which tend to solidify) via conveyor into a dumpster. Pumps then lift the wastewater four stories to provide gravity flow through much of the remainder of the facility. Water falls from the pumps in a centrifugal motion to expel grit (sand, glass, small stones, egg shells, etc.) and then injected with ferric chloride to begin precipitating out phosphates.
Huge volumes of water collect in wide outdoor primary sedimentation tanks, circa 12 feet deep. Many oils, particularly vegetable oils, rise and are skimmed off the top, eventually deposited into oversize fabric sleeves and then a dumpster. Many suspended solids settle into sludge which is then mechanically scraped to wells from which it can be drawn away horizontally underground. The tanks periodically require draining and massive manual cleaning, plus maintenance.
The sludge is moved to similar looking but smaller tanks with lids called anaerobic digesters. These are heated by an adjacent boiler house. Methane was flared off until recently, but a cleaning and processing facility now allows adding the methane to the natural gas fueling the boilers. R.O.I. for the methane project will be about 10 years.
Digested sludge is moved under the river to 55 acre basins where it composts and dries for 3 years. The dried compost is evaluated and blended, then mixed with plant compost, to form biosolids for home, garden, and farm uses.
The water from the primary sedimentation tanks flows to elongated secondary treatment ponds while being mixed with regulated amounts of flows from other secondary ponds in various stages of microbiological decay. Those microorganisms then consume organic materials in the wastewater as it flows slowly down the length of the secondary ponds, which are agitated. The water then moves through elongated and aerated secondary clarification ponds. A substantial laboratory monitors the type and relative numbers of microorganisms in order to regulate the systems of ponds. While complicated and sensitive (to factors as simple as too much vegetable oil in the waste stream), this relatively new biological system is key to meeting EPA treatment standards.
Water allowed to flow from the secondary clarification ponds is passed through elongated horizontal centrifuges on its way to disinfection using sodium hypochlorite (whose facility and tanks were of great interest for some of us). The solids from the centrifuges are sent to digesters.
The disinfected water is transferred under the river to tertiary treatment where all of it is highly aerated and then snaked through a winding channel totaling 40 acres of surface area. The water dechlorinates and some solids settle out for nearly a day while moving through the system. After assuring at least 7 ppm dissolved oxygen, the water is discharged into the Maumee River. Fear of political backlash prevents it from being recycled into drinking water.
The FWEC also toured the computerized central control room for the entire facility including ponds across the river. Operators monitor sensors and cameras.
The facility had newly designed tool boards to minimize time lost retrieving tools from elsewhere in the sprawling plant. These were of great interest because some members were designing boards for their facility.
The FWEC sends a sincere thanks to City Utilities and especially our very dedicated tour guide, Tom Mann.