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Protecting Long Island Sound by Upgrading Sewage Treatment Plants

A Total Maximum Daily Load (TMDL) is basically a cleanup plan mandated by the federal Clean Water Act. The TMDL sets a pollution budget that establishes the maximum amount of pollution a water body can naturally absorb and still meet its water quality standards and be healthy. The Clean Water Act requires TMDLS for all water bodies that do not meet water quality standards. Long Island Sound (LIS) is one of these.

The TMDL sets limits on nutrient and sediment pollution which degrade water quality. A TMDL divides the pollution budget into "wasteload allocations" and "load allocations". Wasteload allocations are for facilities with discharge permits like wastewater treatment plants. Load allocations cover unregulated sources such as storm water runoff.

With more than 8 million people living in the LIS watershed, bringing pollution under control is a huge task.

Depleted fish populations in the Sound in summer months have become a major area of concern. Low concentrations of dissolved oxygen (DO), known as hypoxia, in the bottom waters of the Sound during the summer months can kill or drive away many bottom dwelling organisms.

Nitrogen has been identified as the primary pollutant causing hypoxia rendering much of LIS_s bottom waters unhealthy each summer. Nitrogen fuels the growth of algae, which eventually decays, consuming oxygen in the process. There is enough nitrogen added by human activity to cause a severe hypoxia problem each summer, often with oxygen levels falling well below state standards. Because of this, CT and NY are required by federal law to reduce nitrogen through the implementation of the TMDL.

The New York State Department of Environmental Conservation, the Connecticut Department of Environmental Protection, and the federal Environmental Protection Agency (EPA) have been investigating LIS water quality problems since 1985 through the National Estuary Program Long Island Sound Study.

The TMDL for the Sound was developed by CT and NY and approved by the EPA in 2001. The TMDL is being implemented in phases. Phases 1 and 2 have already been completed. Phase 3, which forms the substance of the TMDL, is underway and must be implemented by 2014; planning for phases 4 and 5 is to be completed in the next few years.

The TMDL identified nearly 48 thousand tons per year (ttpy) of nitrogen coming from point sources (primarily sewage treatment plants), and nonpoint sources (like storm water runoff) within CT and NY as the baseline condition delivered to the Sound. The TMDL requires CT and NY to remove nearly 24 ttpy of nitrogen from the baseline level by 2014.

A Waste Load Allocation is the portion of a receiving water's TMDL that is allocated to one of its existing or future point sources of pollution. CT and NY have identified Sewage Treatment Plants (STPs) as the primary point source of nitrogen in the LIS drainage basin. Therefore, all the STPs located within the Sound's drainage basin in these two states were allocated a certain portion of the TMDL of nitrogen. Individual nitrogen waste load amounts were allocated to each STP.

Nitrogen in sewage is primarily in the form of ammonia, even at a standard secondary level of treatment. With added aeration of sewage, the ammonia is naturally converted by bacteria to nitrite and finally nitrates. Nitrate also stimulates plant growth. To remove the nitrate, treatment plants must establish low oxygen conditions where anaerobic bacteria thrive and convert the nitrate to nitrogen gas, effectively removing it from the waste stream. To meet the TMDL requirement, STPs will need to modify, upgrade, or build whole new treatment systems to remove the nitrogen.

The Big Bucks- Be Prepared!

The bill to remove nitrogen from STPs in CT and NY will be in the range of $1 -2 billion over the 15-year management period ending in 2014. CT_S share is expected to be in the $700- 900 million range with the balance coming from NY. The estimate for upgrading the LIS sewage treatment plants is $240 million. Funding, as a combination of low-interest loans and grants, will come from federally funded state revolving funds, possible state bond acts and municipalities. Westchester County will receive $55 million of stimulus funding to upgrade its LIS sewage treatment plants. $27,500,000 of the $55 million must be matched with other funds.

Are there other sources contributing nitrogen into the Sound?

Yes. In addition to the point and nonpoint source reduction requirements for CT and NY specified in the TMDL, large loads of nitrogen come from northern states (MA, VT, NH) and via the atmosphere from stack and mobile emissions of oxides of nitrogen throughout the eastern half of the U.S. The TMDL sets up a schedule for EPA in conjunction with contributing states to develop final Phase 4 and 5 plans for nitrogen sources from out-of-state and from the atmosphere. The Long Island Sound Study is currently working with the northern states. Their outcome will not affect nitrogen control plans in CT and NY.

Text amended and abbreviated from the writings of the CT Department of Environmental Protection Water Management Bureau and Chesapeake Bay Journal.