Wastewater treatment plant, a blend of science and safety
The ultramodern Regional Wastewater Plant serves Whiteville, Brunswick, Bolton and more
March 16, 2017 | Jefferson Weaver
Newlyn McCullen and his staff at the Whiteville Wastewater Plant spend every day caring for millions of small “pets” – none of which can be seen with the naked eye.
The sewage treatment plant relies on aerobic bacteria (single-celled organisms) that eat organic material in wastewater, breaking the waste down in drain water so it can be cleaned and released into White Marsh.
“It’s an involved process,” McCullen said.
Everything that goes down a toilet, shower or sink in the city or the towns of Bolton and Brunswick eventually ends up in the aeration ponds at the sewer plant. Hundreds of thousands of gallons of wastewater are held in the open tanks. Once the sewage gets there, the aerobic bacteria – which are activated by air pumped into the system – eat waste products.
“Some inorganic materials, like sand, dirt, and metals, settle to the bottom of the tanks,” McCullen explained. “Those are materials the bacteria can’t eat.”
The treated water then goes into a clarifying system, which uses a series of filters to catch fine particles that don’t settle. The sludge produced from the process is periodically cleaned out of the ponds and used as land-applied fertilizer.
From the clarifier, the water goes into a chlorination chamber.
“Before we can release the water,” McCullen said, “we have to eliminate any bacteria that escaped the earlier stages. We want to keep them inside and working – we don’t want to overwhelm the waterways with our bacteria. The chlorine kills any that get through.”
A calcium phosphate solution is then pumped into the clean, chlorinated wastewater to destroy the chlorine.
“Chlorine is poisonous on its own,” McCullen said. “We use the chlorine to take out any leftover bacteria, then remove the chlorine from the water so it can be released.”
The result is water that is actually cleaner than the swamp it drains into, McCullen said – but not so clean that it damages the ecosystem. The pool around the outflow drains is a vibrant habitat for small fish, reptiles, amphibians and aquatic mammals.
“I would have no hesitations about swimming in there,” McCullen said, gesturing to the outfall drainage, “except for the snakes.”
The system has come a long way from the days of open cesspools in town, and so-called “honey wagons” that carried the contents of residential bedpans and chamber pots to the edge of Soles Swamp (for a fee).
Wastewater treatment is one of the city’s largest expenditures, and like most municipalities, is maintained through its own utility fund, produced by sewer bill payments. State law requires that municipal water and sewer systems be self-supporting.
Whiteville’s plant underwent a major revocation starting in 2008, using a combination of state and local grants as well as loans. The city was already treating sewage from Brunswick, but through a regional agreement, began providing wastewater service to the town of Bolton as well as along the future U.S. 74-76 industrial corridor.
All those extra customers, McCullen said, meant even more attention has to be paid to the wastewater coming into the plant.
“A lot of people think that biodegradable means you can send it down the sewer,” he said. “That isn’t the case. Thosehandi-wipes that everyone uses will break down, but it can take five or six years. Still a lot of people flush them down the toilet.
“A lot of things will block up your pipes at home, and never make it here,” he explained. “But if they do make it here, the problems are just as bad.”
Cooking grease is a major problem, McCullen said.
“Cooking oil doesn’t belong down the drain,” he said.
Oil, fats and grease tend to congeal on the sides of sewer pipes, creating a “wall” that reduces the diameter of the pipe – and leads to backups and sewer spills.
“Those oils that make it to the plant can do the same thing here,” he explained. “They build up and reduce our capacity, which shortens the life of the plant.”
Other common problems, McCullen said, are petroleum products and chemicals.
“We don’t want anything coming in here that can kill the bacteria,” he explained. “Pesticides, herbicides, poisons, petroleum products – those can create a dangerous situation for the equipment as well as the system. Don’t pour them down the drain, or into the storm sewers. Anything that can hurt you, can hurt the treatment plant and the wastewater system.”
Many people don’t realize that the key to the treatment process is not chemicals or machinery, but living, breathing organisms, McCullen explained.
“They’re like every other creature,” he said. “They get old and stop working as hard, and we have to make room for the new ones that are creating more bacteria and processing the organic material.”
A big part of the work for the humans at the plant is in the lab -- monitoring the life cycles of the bacteria, as well as maintaining proper chemical balances and checking for dangerous chemicals. The city also checks waterways above and below the plant to provide comparison samples to ensure cleanliness.
Surprisingly, the plant doesn’t have a strong odor of either wastewater or chlorine, like some old-fashioned treatment plants. The aerobic amoeba that break down the organic material in the wastewater also help eliminate some of the odor. Workers also make their way out on catwalks across the ponds several times a day, taking samples and maintaining equipment.
Maintaining the health of the microbes helps keep the sanitary sewer system functioning, McCullen said.
“Without the aerobic activity, we have no wastewater treatment,” he said. “Nobody likes to think about that.”