Ithaca Area Wastewater Treatment Facility

Home > Departments > Department of Public Works > Water & Sewer Division > Ithaca Area Wastewater Treatment Facility

The Ithaca Area Wastewater Treatment Facility (IAWWTF) SIMON WHEELER / © 2008The Ithaca Journal, used by permission. is an Intermunicipal Agency, a successful example of cooperation between multiple municipalities. The IAWWTF is owned by three municipalities (The City of Ithaca, and the Towns of Ithaca and Dryden). Representatives of these communities worked together over a fourteen-year planning and construction period, to create a facility critical to public health and protective of the environment for current and future generations. This treatment plant has been serving its owners' communities since October 1987.

After water is used in homes, institutions, and businesses, it is delivered as wastewater to the sanitary sewer system. There are approximately eighty miles of sanitary sewer mains located underground throughout the City of Ithaca, with additional amounts in the other areas served. The service area has separate sanitary and stormwater collection systems.

Wastewater flows through the sanitary sewer mains primarily by gravity. In addition, there are a small number of pump stations that help deliver wastewater to the IAWWTF for treatment.

The IAWWTF is designed to remove nutrients, solids, and waterborne pathogens from wastewater and to recycle clean water into Cayuga Lake. We treat approximately 6.5 to 7 million gallons of raw sewage each day, although there are noticeable seasonal variations tied to school schedules. In addition, volumes increase at times of rain fall and snow melt and can approach a flow rate of 30 to 35 million gallons per day for short duration. The vast increase is due to the infiltration and inflow of other water into the sewer. This primarily results from: old sewers with cracks or leaky joints, illegally connected house footing drains, sump pumps or roof drains, or leaky manhole covers.

The IAWWTF is fully licensed by the Environmental Protection Agency (EPA) and the New York State Department of Environmental Conservation (NYSDEC). The laboratory at the plant is certified by the New York State Department of Health (NYSDOH) and the National Environmental Laboratory Approval Program (NELAP).

Learn more:

Latest News & Events


New Trucked Waste Receiving Building

Construction of a new trucked waste receiving building is scheduled for completion in the summer of 2014. It is larger than the previous structure to accommodate tractor trailers or two smaller trucks simultaneously. Tankage was expanded by 50% and new equipment for better rock removal and odor control were added. A food scrap dump station was added to increase the diversity of organic waste that we can receive for conversion to biogas fuel in our digesters.  


Energy Performance Upgrade

The IAWWTF is more than half way through a multi-year, $8 million, energy performance upgrade. Completed improvements include:

  • Weather-sealing existing buildings

  • Installation of energy efficient lighting fixtures and bulbs

  • Installation of 7.5 kW photovoltaic solar panels on a roof.

  • Improvements to the air handling HVAC equipment.

  • Two aging 100 kilowatt co-generators have been replaced by four state-of-the-art 65 kilowatt micro-turbines.

  • One of our hot water boilers has been replaced with two smaller, more efficient units.

  • The anaerobic digesters received more efficient mixers and a new methane storage bubble has been installed.

  • New aeration blowers, dissolved oxygen control system and air diffusion equipment will be installed during spring and summer 2014.

  • The guaranteed result of these improvements will be long term cost savings. These savings will be the result of decreasing our energy consumption and increasing our renewable energy production (generated primarily from increased bio-gas production along with some solar electric). Before this upgrade, we produced bio-gas that generated 25-30% of the plant's energy needs. The contract guarantees that we will generate at least 60% of our energy needs.  We have already exceeded this benchmark! 


Water Quality Monitoring and Current Weather Data

IAWWTF staff have created a new website to present recent data showing the results of the ongoing plant upgrade; summer water quality data with a focus on phosphorus for the south end of Cayuga Lake (from our PISCES monitoring station); and near-real-time weather readings from a new state-of-the-art weather station located at the plant. Check it all out at:


Safe Medication Disposal

The IAWWTF is proud to be the founding member of the Coalition for Safe Medication Disposal (CSMD).  To date, we have collected more than 3.5 tons of medications for safe disposal.

In addition to twice a year, one day collection events, there are now nine permanent drop-boxes for disposal of unwanted household medications:

  • Tompkins County Sheriff, Public Safety Building, 779 Warren Rd, Ithaca (24 / 7 / 365)

  • Ithaca Police Dept., 120 East Clinton St, Ithaca (M-F 7:30 AM - 3:00 PM)

  • Tompkins County Dept of Probation (Human Services Bldg.), 320 West State St, Ithaca (By appointment, call 274-5380)

  • Cayuga Heights Police Dept., 836 Hanshaw Rd, Ithaca (M-F 9:00 AM - 4:30 PM, except holidays)

  • Groton Police Dept., 108 East Cortland St, Groton (M, W, F 8:00 AM - 4:00 PM, or by appointment)

  • Trumansburg Police Dept., 5 Elm St, Trumansburg (M-F 10:00 AM - 2:00 PM, or by appointment)

  • Cornell University Police Dept., G2 Barton Hall, between Statler Drive & Garden Ave, Ithaca  (24 / 7 / 365)

  • Dryden Police Dept., 16 South St, Dryden (M-F 9:00 AM - 3:00 PM, or by appointment)

  • TC3 (Tompkins Cortland Community College) Campus Police, 170 North St. (main bldg, suite 118), Dryden (When the campus is open: M-Sa 7:00 AM - 10:00 PM, Su 10:00 AM - 6:00 PM)  

 For more information, go to:

The work of the CSMD is not only helping our local community, it is having a nationwide impact.  We produced a series of how-to videos (produced by Park Productions at Ithaca College).  The videos, an inventory spreadsheet and other documents created by the CSMD are available to a nationwide audience at:

If you have any questions about safe medication disposal please contact: Ed Gottlieb


Sewage Pollution Right to Know Act

On May 1, 2013, reporting requirements for the “Sewage Pollution Right to Know Act” go into effect. This Act, signed into law last year by Governor Cuomo changes the requirements for reporting partially or untreated sewage discharges, also known as bypasses, from publicly owned treatment works and from publicly owned sewer systems. 

The law requires the Department of Public Works Water & Sewer Division to notify the New York Department of Environmental Conservation (NYDEC), Tompkins County Health Department, Mayor of the City of Ithaca, Supervisor of the Town of Ithaca, and the general public within four hours after discovery of a sewer bypass. 

Please note that notification does not indicate immediate cause for alarm or concern.  Sewage backups, main breaks, and construction releases of small amounts of sewage are not uncommon in any public utility and generally are not a cause for concern.  As of yet, the NYDEC has not set any minimum thresholds for reporting.

The main mechanism for the general public to find additional information about reported discharges is through the NYDEC’s new “Sewage Discharge Reports” website

Please feel free to contact the Water & Sewer Division at 272-1717 should you have any questions about the new reporting requirements.





IAWWTF staff have assisted local faculty and students for many years by providing information on the wastewater treatment process as well as samples to be used for research. Contact the plant at (607) 273-8381 for more information. A release form must be signed before any samples can be provided. A PDF version of this form is available for download here




Plant tours are available for free as a public service. Arrangements must be made in advance by calling the plant at (607) 273-8381. Group size is generally limited to a maximum of 25. It is easiest for us to accommodate tours that start between 8 AM-1 PM on Tuesdays, Wednesdays, or Thursdays. Children as young as ten can be taught about basic plant processes. For reasons of safety, all children must have adequate adult supervision. Infants should not be brought to the plant.

Tours typically take an hour and fifteen minutes to an hour and a half. They can be given as a general overview or can be tailored to meet the special interests of your group.  A typical tour spends forty-five minutes in the plant's control room and laboratory with the remainder spent walking around the plant, both inside and out.  Please do not wear flip-flops, sandals, or high heels and be sure to bring clothing suitable for the weather.

We look forward to helping you and your group better understand what is involved in cleaning municipal and industrial wastewater. 

If you can’t make it to the plant for a tour, a video tour is available in 5 parts below:




Wastewater Treatment


The IAWWTF went into service in October 1987. Prior to 1987 the major portion of the wastewater plant was located in what is now the Sciencenter. Along with wastewater from City of Ithaca, the Town of Ithaca and the Town of Dryden, the IAWWTF also treats peak flows diverted from the Cayuga Heights Wastewater Treatment Plant and trucked wastes including: septage, landfill leachate, municipal sludge, alkaline hydrolysis liquid waste from the College of Veterinary Medicine, whey and other dairy processing wastes. Wastewater from well drilling and hydraulic fracturing (fracking) operations is not treated at our facility. The IAWWTF discharges into Cayuga Lake through a half-mile long, 48-inch diameter line that reduces to 36 inches for the last 240 feet. The effluent is diffused into the lake through 6-inch riser pipes, located 10 feet apart along the last 240 feet of the line.

Cayuga Lake is part of the Great Lakes Basin (Oswego-Seneca-Oneida Drainage Basin). The Great Lakes Water Quality Initiative sets the effluent limits for the IAWWTF. The State Department of Environmental Conservation (DEC), the Environmental Protection Agency (EPA), the New York State Department of Health (NYS DOH), and the National Environmental Laboratory Program (NELAP) are responsible for regulating different aspects of the operations at the IAWWTF. 

The IAWWTF was designed to remove phosphorus, biological oxygen demand, & solids. The plant also removes most non-conventional pollutants as well. A federally mandated industrial pretreatment program prevents non-conventional pollutants from entering the wastewater system in amounts greater than the plant can treat.

Wastewater treatment incorporates: preliminary screening, primary clarification, biological treatment, chemical phosphorus removal, chlorination for disinfection and de-chlorination. Anaerobic digestion is used to stabilize biosolids, which are then dewatered and land-filled. The anaerobic digestion process produces biogas (65-70 % methane) that is purified and then burned to generate electricity and hot water.

Operational Parameters

Flow: The design capacity of the plant is 13.1 million gallons per day (MGD), monthly average.  The average flow of sewage treated daily at the IAWWTF is approximately 6.5 MGD. Peak flows in excess of 30 MGD have been recorded.

Phosphorus: Phosphorus is a nutrient that, in combination with other nutrients, promotes vigorous plant growth.  Phosphorus is the limiting nutrient in Cayuga Lake. To avoid eutrophication, the amount of phosphorus going to the lake needs to be minimized. The average load of total phosphorus to the IAWWTF is more than 200 pounds per day (Lb/day). From this the primary and secondary systems remove 170-180 Lb/day. The tertiary system removes 75-80 percent of the remaining phosphorus.

The IAWWTF currently discharges an average of less than 10 Lb/day of phosphorus; well below the allowed limit of 40 Lb/day. At this level, the IAWWTF is contributing approximately 10-15 percent of the phosphorus load to the south end of Cayuga Lake. Non-point sources, such as farm runoff, are the largest contributor of phosphorus to the Lake.

BOD: The biochemical oxygen demand (BOD) is a standard measure of the amount of conventional contaminants in wastewater. Basically, the microbes present consume oxygen dissolved in the water in proportion to the amount of organic and chemical food present. The design capacity of the IAWWTF is 15,100 Lb of BOD/day in any one month and 11,300 lb/day in any one year. The average amount received is 7,200 Lb/day. The BOD is removed during treatment with an efficiency of 92 to 97 percent, well above the required 85 percent. The maximum allowed BOD in the effluent is 30 milligrams per Liter (mg/L). The average BOD of the treated water released into Cayuga Lake is approximately 11 mg/L.

Solids: Solids are composed of biodegradable and non-biodegradable matter. The non-biodegradable portion is composed of soil, sand, salts and organic matter resistant to biodegradation such as lignin and cellulose.

The solids are removed during treatment with 97 percent efficiency, far surpassing the required 85 percent removal.  The allowed limit for solids in the effluent is 30 mg/L. The typical average concentration of solids in the effluent is 3.3 mg/L.

The total average daily load of suspended solids to Cayuga Lake from the IAWWTF effluent is 178 Lb/day.  As a comparison, the 1997 average suspended solids load from Six Mile Creek was 94,600 Lb/day.

We are required to reduce the amount of volatile solids by at least 37 percent. The IAWWTF accomplishes 57 percent volatiles reduction (a 43 percent overall destruction of solids).


IAWWTF Process Summary


IAWWTF Process Schematic


Large solids are removed by the bar screens in the preliminary treatment step. The removed solids are land-filled.

Primary settling tanks are where most of the solids are removed. Those heavier than water settle out and those lighter float. Approximately 30% of the incoming organic load is removed here. 

Settled solids are degritted in the cyclones and then dewatered in the thickeners before going to the digester. 

The activated sludge process is where the clarified primary wastewater is fed to aerobic microorganisms under constant aeration. The microorganisms in the aeration tanks agglomerate to and assimilate organics in the wastewater. The clumps of microbes and food that are formed are called floc particles.

The secondary clarifiers are where the floc is removed by gravity settling. To keep a constant, healthy ratio between the amounts of biomass (organisms) in the aeration tanks and the amount of incoming organic loading (their food), much of the activated sludge that settles in the secondary clarifiers is returned to the aeration tanks. The excess activated sludge is removed (wasted) to the thickeners for further treatment.

Tertiary treatment went on-line in the middle of 2006. Using three additives: polymer, ferric chloride, and engineered sand (added as a ballast) additional suspended solids are made to clump together in larger particles that are heavy enough to settle and be removed. This system is optimized for phosphorus removal, removing roughly 80% of the remaining dissolved phosphorous. It also removes about half of the other remaining conventional pollutants. Waste sludge from this system is sent to the thickeners.

Excess water is removed from all the waste sludges (which come from the primary settling tanks, the secondary clarifiers, and the tertiary clarifier) in the thickeners. The thickened sludge is then pumped to the primary digester. There anaerobic digestion occurs which further reduces the total biomass. The biomass is digested for approximately 28 days at 98° F, and overflows to the secondary digester. After further stabilization there, the sludge is dewatered using a chemical polymer and a belt press. The dried cake (@20-26% solids) is transported to a landfill for disposal (six to twelve thousand dry Lb/day).

During anaerobic digestion, a biogas rich in methane is generated. The biogas produced before the energy upgrade was utilized to generate 25-30% of the total energy (heat & electricity combined) requirements of the IAWWTF. As different aspects of the energy performance upgrade are completed, the total energy requirements of the plant will decrease while the amount of energy produced from biogas will increase. The guaranteed result of these improvements is that the plant will generate sixty percent of its energy requirements using this renewable fuel.

The final step of cleaning wastewater is disinfection for pathogen removal. Chlorine bleach (sodium hypochlorite) is added to the effluent water for this purpose. After mixing with the effluent for enough contact time to provide good pathogen destruction, the remaining residual chlorine is removed using sulfur dioxide gas. The clean effluent is then discharged into Cayuga Lake.


Documents & Links