How it Works: The Northport Sewage Treatment Plant

Editor's Note: There has been much debate as of late regarding whether the Northport sewer treatment plant will get itself in compliance with nitrogen standards issued by the New York State Department of Environmental Conservation by 2014.

What many don't know, however, is how the plant itself actually works. Northport Patch contributor Justin Izzo got a tour of the facility Friday, April 29 from Manaer Erica Reinhard,

The Plant, From Start to Finish
The first stop on a recent tour led by plant manager Erica Reinhard is the laboratory, where the plant workers test discharge for pH levels, temperatures, and the levels of two types of coliforms (total and fecal).

“The testing we do here in house is for process control, to make sure the plant is working every day,” said Reinhard. “When we send the samples out, it’s basically verifying our work. It’s like quality control in a factory. Our quality control is our lab. This is how we find out how the waste water is doing. The coliforms are taken after disinfection, and then we see what the result is.”

The statistics garnered through testing illustrate that close monitoring is beneficial. The most recent coliform tests produced very low numbers for each type, with 13 for total coliforms and 2 for fecal coliforms.

These numbers are well below the plant’s limits, illustrating that the plant is running smoothly to the workers.

When the wastewater first comes in to the plant, it passes through an influence structure. Surprisingly, the sewage doesn't smell. That’s because the structure is pumped with air, creating an aerated drip chamber so there is no volatile scent.

Not only does the aerated drip chamber get rid of the foul scent that raw sewage produces, it also pushes some of the denser particles, such as sand, to the bottom of the chamber, filtering them out early in the process. Other particles, such as fecal matter, remain.

Once the sewage passes through the influence structure, it passes through a machine that cuts up any solids that passes through on its way to an influent chamber, where the sewage is pumped into an equalization tank. In this tank, the speed through which the sewage flows through the plant is regulated.

The equalization tank has a depth of fifteen feet. On this day, the level is at 5.81 feet. In days of excessive rainfall, the tank can get close to the fifteen-foot level. But it’s usually pumped faster before it can overflow.

“You can see marks on the wall where it’s gone up,” Reinhard pointed out. “You get a big heavy rain event, and yeah, you can have a lot of infiltration.”

The system can overflow, however, during times of heavy rainfall. Reinhard said that this is mainly due to people in the Village who illegally hook up to the sewer system.

“They’re not supposed to be putting any water in the system,” she said. “That’s illegal. You can’t do that. But people do it anyway. That accounts for a lot of extra water, instead of just sanitary sewer, which is what we’re supposed to have.”

Before we move on to the next part of the process, Reinhard shows two places where the sludge in the stream is filtered out from the process and placed into a box as a suspended solid. Again, surprisingly, there is no smell. “It’s not supposed to smell,” said Reinhard. “This is an aerated digester (with air). If it was an anaerobic digester, which means without air, then you would have the odor of hydrogen sulfide.”

The remaining sewage, as well as sludge that is taken out later in the process called return-activated sludge, are mixed into two separate aeration tanks. It’s in these tanks where the nitrogen is taken out of the equation, by pumping as little oxygen into the boxes as possible. The tanks take in a lot of ammonia at first, but by the time the sewage goes through, that ammonia becomes nitrite.

“What happens in the aeration tanks out here is all the bacteria have a field day,” said Reinhard. “Our job is to keep the bacteria happy. There’s a lot of ammonia in the water. We take the ammonia and we turn it into nitrate. Down below, there are two pumps that take the water and shove it back up here in the anoxic zone. Through carbon in the waste bin, which facilitates the reaction, the incoming water goes into the anoxic zone. You take the nitrate and it gets turned into nitrite. When it gets turned into nitrite, and goes back into here, it goes into the atmosphere. And that’s how we get rid of nitrate. It’s a chemical process. You go from ammonia to nitrate to nitrite, and then it’s gone.”

The current process gets rid of a significant portion of the nitrogen, but some inevitably sneaks through. “There‘s no process that will ever [get rid of all of the nitrogen],” said Reinhardt. “We get rid of as much as we can. Right now we’re taking this particular process about as far as it can. We’re certainly within our limits at the moment. Down the road, they’re looking to expand the plant, which costs a lot of money, to meet the requirements that are coming up.”

Also in the anoxic tank, on the bottom, are swine bubble diffusers, which provide organisms within the tank with the oxygen needed to survive. Enough is pumped in to allow them to survive, but finding the specific amount needed is tricky. “If you give them too much, they can actually burn up,” said Reinhardt. “If you give them too little, they’ll die in a place above septic. We have to monitor the dissolved oxygen constantly.”

Once the sewage travels through these tanks, it passes through drains as a substance called “mixed liquor”. Mixed liquor from the west anoxic tank travels east, and mixed liquor from the east anoxic tank travels west, through pipes to an area called a rectangular clarifier. Here, the mixed liquor crawls through the clarifier at a pace so slow that it doesn’t appear to be moving. After two and a half hours, the leftover sludge falls to the bottom. There, machines called flights scrape it into a pit, where it gets converted into the return activated sludge that goes back and gets mixed in with the incoming waste treatment.

Wheels at the front of the clarifier raise or lower telescopic sludge valves in the clarifiers, depending on what the plant workers intend to do with the sludge. “When we want to get rid of sludge, we raise this up, add polymer, and then we turn on the sludge pumps and take it out of the waste bins,” said Reinhard.

Once the sewage passes through the cycle, it moves out of the plant. On its way out, it passes through an ultraviolet disinfection area, where 36 UV lamps sterilize any last coliforms or other disinfectants. This process used to be done with chlorine, but due to health concerns, it was switched to UV, a process that makes this process less customizable.

“There’s more flexibility with chlorine,” said Reinhard. “You can regulate it with what’s going on. With UV, it’s either on or off, there is no intensity level. It’s like a carpenter having a variety of hammers. You don’t want to drive a finish nail with a sledgehammer. This is like a sledgehammer. The only way you could up the level would be to add more UV banks somehow, but you’d have to re-engineer the effluent outpour.”

Usually, the sewage is able to flow out through gravity. But during times of high tides, it’s unable to. When this happens, the plant uses two pumps to force the water out.

In the basement of the plant’s office are two power panels and two generators that supply the power to make everything work. The newer power panel and generator were installed when Phase 1 of the plant upgrade was completed in 2004. The old generator still runs, as does part of the old power panel.

Also in the basement are blowers supplying air to the system. There are two of them, but only one runs at a time. Two separate blowers, located in a shed near the equalization tank, supply air to that tank. Again, only one of them runs at a time.

“It’s not necessary to run both blowers at the same time,” said Reinhard. “I don’t like to put too much air on the incoming sewage because it goes right into the anoxic zones. If I put a lot of air in, I’m destroying my anoxic zones. You don’t want to put a lot of air in. You just want to put enough air in to keep things from smelling.”

The entire process is controlled by Reinhard from a computer at her desk. With it, she can control which blowers are on or off, as well as manually control the speed they are blowing at. She can also operate the pumps in the equalization tank manually if necessary.

A Job That Always Needs to be Done, No Matter the Conditions

To many, it may seem puzzling that the lab would do its own testing when it could simply have the outside lab test for them. Reinhard, however, said that the plant employees felt it was their obligation to the public to make sure the plant was always in top shape.

“Contrary to popular belief, we give a damn,” she said. “For a lot of people, it’s just a job. For us, it’s a career.”

Reinhard, who's in the final weeks of her own 33-year career at the plant, understands why people might be upset over the delay getting the plant into shape for the proposed nitrogen emission limits. But she took exception to people who question the commitment of her and her workers.

"This plant never shuts down," she said. "Rain or shine, winter or summer. Seven days a week, holidays. You name it, we’re here. I’m not saying we’re saints or anything, but we do do this for a living, and so does everyone else who works in a treatment plant.”

For Reinhard, her passions run deep. Before she managed the plant, her father managed it for three decades. That's why she's willing to tell anyone who's willing to listen about how it works.

“I never get tired of explaining it, because most people don’t care,” she said. “It’s very important. I’ve always thought, and my dad always thought, that we are professionals in protecting that harbor the best we can with what we have. A lot of people talk about it. We do it for a living."

“Most people don’t have a clue, and they don’t want to know,” she added. “That’s why I have no problem explaining the whole process to you. I’ll talk people’s ear off about this. Because the more people know, the more money will come into this place to make it better.”