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The City of Syracuse and Onondaga County own and operate sanitary, stormwater and combined sewer collection systems in the Syracuse area. The sanitary sewers and combined sewers are connected to collection and treatment systems owned and operated by Onondaga County. The City’s sewer system was largely built between 1875 and 1950. This system originally was designed to discharge into area streams and drainage ditches.
As part of an effort to modernize this system, the Syracuse Sewage Treatment Plant was transferred to Onondaga County in 1955 (along with the storm drains in the city) after which the plant was upgraded (1959-1960) and renamed the Metropolitan Syracuse Wastewater Treatment Plant (Metro). Since 1960 Metro has been upgraded repeatedly; in 1979, 1981 and over the last five years (2003-2008). In addition to upgrades to Metro, the overall wastewater system is being upgraded to reduce the number of discharge points to the county's surface water bodies (lakes & streams), and to reduce the amount of untreated wastewater being discharged (see below). This has been undertaken to meet the consent agreement between Onondaga County and several litigants due to the counties violation of the Clean Water Act. A summary of the agreement can reviewed at the Atlantic States Legal Foundation website. The original 1998 consent agreement and the recently amended consent agreement are included here as well ( 1998 ACJ) and ( 2009 amendment). The recent amendments were negotiated to allow the county to try a less centralized approach to reducing combined sewer overflow, as described in the counties press release ( Onondaga county press release).
In addition to the cities sewer system, there are three County drainage districts that include portions of the City including the Harbor Brook Drainage District, the Meadowbrook Drainage District and the Bear Trap/Ley Creek Drainage District. As an example, the Harbor Brook Pump Station can contribute up to 30 million gallons per day to Metro. In addition, the Ley Creek, Westside, and Liverpool pump stations convey wastewater to Metro. Total flows into the system are generally around 60 to 80 million gallons per day. However, flows to the plant can exceed 126 million gallons per day, which is the maximum amount of water that can be treated by Metro.
Combined Sewer Overflows
The reason flow to the plant can vary by more than fifty percent is a result of the combined sewer collection systems that exist in Syracuse. This problem is a common problem of older sewer systems where collection between the sanitary sewers (domestic waste water) and stormwater sewers (water from storm drains) have been allowed, over time, to overlap. This result requires the treatment of both sources of water, and during periods of precipitation greater amounts of water for treatment. These combined systems can lead to excess water for treatment during periods of rain and runoff as illustrated to the left. This affect is referred to as CSO's, combined sewer overflow, and are the result of combined sewer collection systems. Currently, Onondaga County is actively working to reduce the number of sources of discharge from the Metro sewer system, and is working on several fronts to reduce/abate the overflow as outlined on the Onondaga County website.
The wastewater at Metro is treated in three stages before it is disinfected and discharged to Onondaga Lake. The treatment stages are referred to as primary, secondary, and tertiary treatment.
Primary Treatment: In the first stage of treatment solid materials are separated from the wastewater, through a screening process, a sand/gravel settlement process, and a final low energy settlement (primary clarifier) process. At this final stage, oil and grease is also skimmed from the surface of the wastewater.
Secondary Treatment: The next stage of wastewater treatment involves the use of aeration tanks where aerobic bacteria are provided oxygen and consume the dissolved organic waste. Upon leaving the aeration tanks, the bacteria and associated materials are allowed to settleout in secondary clarifiers. At this point greater than 98% of the waste has been removed from the wastewater.
Tertiary Treatment: Upon leaving the secondary clarifiers the wastewater is pumped to the new tertiary treatment facility at Metro (since 2004). This new facility is a new state-of-the-art process for year-round removal of ammonia and phosphorus. The facility utilizes a biological aerated filter (BAF) to remove ammonia (nitrogen) through the growth of oxidizing nitrogen bacteria on polystyrene beads. The wastewater is then sent on to a high rate flocculate settling system (HRFS) to remove phosphorus, by adding an iron oxide compound and other flocculating compounds to the waste water. Fine sand (microsand) is then added to the water and the phosphorus floc is settled out with the sand. Upon leaving the HRFS the wastewater is then disinfected utilizing ultraviolet (UV) radiation (during warm weather months). UV radiation is utilized as an alternative to chlorination of the water, as chlorination residue in the water discharged to Onondaga Lake is harmful to the lake's ecology. UV radiation sterilizes the bacteria and does not produce a harmful residue.
Upon completing disinfection, the water is discharged to Onondaga Lake. A more complete description of the wastewater treatment process is available on the Onondaga County website.
The completed improvements for Metro, and those slated for completion in the near future, are part of the effort to significantly reduce the amount of untreated wastewater, ammonia and phosphorous discharged into Onondaga Lake. The previously cited consent agreement established specific criteria for reducing the amount of untreated wastewater, ammonia and phosphorous discharged into Onondaga Lake.
For more on the affect of wastewater on Onondaga Lake, consider taking a course in the ETG program at OCC. Review some of the courses available at
Note: We appreciate the use of these images from Metro's Webpages on the Onondaga County website
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