The East Lansing Wastewater Treatment Facility can provide treatment for an average design flow capacity of 18.75 million gallons per day (MGD). Presently, the average Raw Wastewater Flow (influent) is 13.40 MGD. Treatment processes in use at the plant include aerated grit removal, flow equalization, primary clarification, course bubble air diffusers to supply oxygen to the activated biological solids, secondary clarification, disinfection , rapid sand filtration, dechlorination, and post filtration aeration. Liquid Treatment / Solids Removal Preliminary Treatment Wastewater enters the Plant headworks (wetwell) via a 54" influent sewer and passes through two parallel double- drum channel grinders to reduce the size of materials in the influent. The influent is then pumped up to grade level where it flows through an aerated grit removal system. Flow leaving the aerated grit tanks enters a 5.3 million gallon aerated flow equalization basin by gravity. From there the wastewater is pumped to the primary treatment system .
Primary/Secondary / Tertiary
Treatment The Plant flow to the primary and secondary treatment processes is split into two separate treatment trains. The South train (constructed in 1964) consists of Primary tanks 1-4, Aeration tanks 1-7, and Secondary Clarifiers 1-4. The average flow through the South train is 5.0 MGD. The north train (constructed in 1976) consists of Primary tanks 5-10, Aeration tanks 8-17, and Secondary clarifiers 5-7. The Average flow through the North train is 8.4 MGD. Primary biosolids are pumped from the Primary clarifiers to storage for later disposal (see below) Floatable oil, scum and grease is also removed from the Primary Clarifier surfaces and pumped to biosolids storage. The Primary effluent flows into Aeration tanks containing activated biological solids. Ferrous Chloride is added to the activated solids flow prior to entering the Secondary Clarifiers to chemically remove dissolved phosphorus. Waste Activated Biological Solids are removed from the system for treatment and disposal (see below). Sodium Hypochlorite is added to the secondary clarifier effluent to achieve disinfection. Flow from the North and South Secondary Clarifiers is combined and pumped to the Tertiary treatment process which consists of rapid gravity sand filters, dechlorination using a Sodium Bisulfite solution, and post-filtration aeration. The filtered water (Final Effluent) is then discharged to the Red Cedar River. The average Final Effluent flow to the River is 12.9 MGD (approximately 0.5 MGD is returned throughout the Plant for process water). Solids Disposal Grit The grit removed form the aerated grit chambers is processed by two grit washers, deposited in 2 -6 cubic yard containers which are trucked to an off-site land fill as needed. Primary Solids/ Secondary Biological Solids
The biosolids removed from the Primary clarifiers are pumped to underground storage tanks. Waste Activated Secondary Biological Solids are removed and thickened using a Dissolved Air Flotation process. These thickened Biological Solids are then pumped to the underground storage tanks containing the Primary Biosolids. Air is used to mix and combine these two materials. This combined mixture is pumped to a dewatering process utilizing 2-2.5 meter Belt Filter Presses. Prior to entering the dewatering process the blended biosolids (approximately 2%-3% solids) are conditioned with a cationic polymer to coagulate and thicken this material. This dewatered material (approximately 21% solids) is conveyed to a building where it is loaded into 20 cubic yard containers and trucked to a landfill. Once in the landfill the material decomposes anaerobicly with other solid wastes to produce methane gas which is burned on site to produce electricity. Plant / Collection System Improvements As mentioned above, the City of East Lansing first constructed the Treatment Plant on the present site in 1964 with biological secondary treatment as the final treatment step. The capacity of this facility was 8.0 MGD. In 1976, the Plant was expanded to its present capacity of 18.75 MGD. Additional primary and secondary treatment, a new Grit removal system, flow equalization, tertiary filtration after secondary treatment, additional Biosolids storage ,a second Dissolved Air Flotation Unit, a second Multiple Hearth Incinerator, and Ash Storage Lagoons were all added to the treatment process as a result of this expansion. In 1989, the two Vacuum Coil Filters used for biosolids dewatering were replaced with two- 2.5 meter Belt Filter Presses. In 2002, the solids truck hauling system cited above replaced the multiple hearth incinerators for solids disposal. In 2001 and 2002, in addition to the Solids Handling System improvements mentioned above, the Plant is also underwent a comprehensive Instrumentation and Controls System upgrade. This system includes, among other things, continuous monitoring and remote control of Plant processes as well as in-line monitoring of the Plant’s Final Effluent discharge to the Red Cedar River for Dissolved Oxygen, pH, and residual Chlorine. Remote monitoring and control of the CSO Pump Station and Retention Treatment Basin (RTB), and three other Pump Stations located in various parts of the service area was also included in this project. Between 1993 and 2006, the City designed, constructed and put on line Phase A (Tunnel Sewer and Combined Sewer Overflow Pump Station), Phase B (sewer separation in the Wilmarth District in the area of Hagadorn Road and Grand River Avenue) and Phase C (Retention Treatment Basin to provide settling and disinfection) of the City’s Combined Sewer Overflow (CSO) Control Program.