The Conservation Conversation: The Problem With Nitrogen, Part 1

A few weeks ago, several local news outlets ran stories telling us that a sewage treatment plant had been allowed to increase its dumping of nitrogen into Little Neck Bay.  

The reporting was mostly accurate, but not as complete as one might have wished. At least one paper incorrectly wrote that the discharge was going into Little Bay, which is between Fort Totten and the Throggs Neck Bridge.

The facility in question is the Belgrave Sewage Treatment Plant, which serves a number of communities in Great Neck. Ironically, the plant itself can only be reached from Little Neck; it is accessible from the area north of the Little Neck Long Island Rail Road station, where it lies immediately behind a residential area along 255th Street. 

The discharge pipe from the plant starts out at ground level and runs north through the Udalls Cove salt marsh until it reaches the shore of Udalls Cove itself, just opposite Douglaston's Memorial Field. There the pipeline enters a concrete structure that somebody decorated many years ago with large painted sunflowers. The pipeline takes two 90-degree bends and continues underwater to the discharge point several hundred yards north near the mouth of Udalls Cove.

In my subsequent columns, I'll provide some more information about why and to what extent the Belgrave Sewage Treatment Plant is supposed to reduce its nitrogen discharges and how it is doing in that effort. But, in this first column, I'll focus on the pollutant in question - nitrogen.   

So, here's the interesting thing about nitrogen: until relatively recently, it wasn't really considered to be a water pollutant at all. Consequently, during most of the 20th century, sewage treatment plants weren't designed or equipped to remove nitrogen. 

In 1972, the landmark federal Clean Water Act established national policy that all waters of the United States should be clean enough to support fishing and swimming. Between the U.S. Environmental Protection Agency and state agencies, such as the New York State Department of Environmental Conservation, maximum discharge limits were set for all sorts of pollutants in sewage including bacteria, oil, and other chemicals that can enter the sewage system from industries and roadways.  

Limits were also set for "biological oxygen demand," or BOD. This relates to the total amount of organic matter in the effluent, which, when it decomposes, depletes the oxygen dissolved in the water of the rivers, bays and harbors into which the sewage treatment plants discharge. 

For most of the past 40 years, there was no limit on nitrogen discharges from sewage treatment plants because it wasn't considered necessary. There was plenty of nitrogen coming out of the plants - after all, human bodily waste is loaded with nitrogen. But the nitrogen itself didn't pose any threat to people swimming in the receiving waters nor to the plants or animals living there. 

What was not appreciated, however, is that nitrogen is indirectly harmful to the aquatic environment. Here's how: nitrogen is a "nutrient" for green plants. Stated more simply, it is fertilizer. Look at any bag of fertilizer you buy for your suburban lawn or your house plants and you'll see that nitrogen and phosphorus are the primary ingredients. Nitrogen makes green plants grow, whether those plants live on the land or in the water.

When sewage treatment plants add lots of nitrogen to the receiving water, algae, which are tiny green plants, grow more rapidly. These "algal blooms" can contribute to green tides, brown tides and red tides, depending on the color of the algae (though they all photosynthesize, they aren't all actually green in overall color).  

Next, all those extra algae start to die off. They drift downward from the surface of the water, where they live in order to get sunshine, and they start to decompose just like the grass clippings or autumn leaves you pile into a compost heap. Decomposition is a form of "oxidation" in which the organic carbon from the formerly living organism mixes with oxygen to form carbon dioxide. On land, the oxygen comes from the air. In an aquatic setting, decomposition uses oxygen that is dissolved in the water itself.

And therein lies the problem with nitrogen: too much nitrogen means too many living algae, which means too many dead algae, which means too many decomposing algae, which means too much oxygen being drawn out of the water, which means too little oxygen left for the animals that depend on it. That includes fish and crabs and clams and oysters and worms and lobsters and snails and countless other aquatic animals, all of which need oxygen to live, just the same as we do. 

More in my next column about this condition, which is known as hypoxia and is a major problem in the Long Island Sound.