Jessica Schladebeck

Delta Democrat-Times

GREENVILLE – The Mighty Mississippi may be muddy, but it isn’t dirty.

And Greenville, among cities up and down the meandering river, is working to keep it that way.

Greenville’s Waste Water Treatment Plant comprises a sprawling network of pipes, above and below ground, and a series of tanks that filter, separate and chemically treat Greenville’s sewage before discharging the largely purified water into the river.

“We’re fortunate to have the largest discharge stream in the country, and that’s the Mississippi River,” said Greenville Public Works Director Brad Jones, who oversees the treatment plant.

The plant treats, on average, up to 10 million gallons of wastewater a day, said plant manager Brenda Gales.

The process begins with a technique known as extraction.

Four intake pipes bring sewage, be it from toilets, showers or sinks, to the plant from all across Greenville, said assistant facility operator James Parks.

The wastewater is then funneled into a so-called raw-sewage distribution box, where it is separated into one of four large pods.

“The first step in cleaning the water is the bar screen,” he said.

The bar screen, a large claw-like piece of equipment, reaches into the water and filters out larger debris from the sitting water, which then makes its way to aeration tanks, where it is forced through a pocket of compressed air.

Aeration brings water and air into close contact to remove dissolved gases, including carbon dioxide, and to oxidize dissolved metals, such as iron, and remove volatile organic chemicals.

The microbial world, not unlike the human world, has its good guys and its bad guys. The treatment plant takes advantage of that.

Once wastewater is aerated, it is mixed with what is known as activated sludge.

“The word activated is used because the sludge contains many active bacteria that can feed on the waste and other harmful bacteria in the water,” Parks said.

It’s biological warfare, of a good sort.

“Adding oxygen to the water increases the bacteria so that it eventually destroys itself,” facility chemist Aldrick McMiller said. “It’s creating bacteria killing bacteria.”

The wastewater, in its elaborate travels through the plant, then flows into one of the facility’s several clarifier tanks, each of which are 90 feet in diameter and roughly 15 feet deep. Each can hold more than 2 million gallons of water, Parks said.

There, the wastewater sits for several hours as the sludge sinks to the bottom, and the water is then disinfected with chlorine.

At that point, Jones said, the wastewater can safely be discharged into the river, even as the sludge is returned to the aeration system to react with newly arriving, untreated wastewater.

The separated, screened, aerated and otherwise treated effluent is then pumped underground five miles to where it is discharged near Warfield Point Park.

The process, from start to finish, has taken 18 hours, and the water entering the river is 95 percent pure, McMiller said.

“We help nature re-acclimate the water,” he said. “If this process was done naturally, it would take hundreds of years. We’re just helping it along. Nature still has to take care of that remaining 5 percent, though.”

That will take some 27 years, during which time Mother Nature plays her role, and, eventually, that water, once sewage, will be returned to the tap, McMiller said: “That’s something a lot of people are grossed out by, but what they don’t understand is almost all water is used water.”

Before the water is discharged, it is tested on-site.

“We check the pH levels and the oxygen content of the water regularly,” McMiller said. “We also monitor for nitrogen and phosphorus.”

“We want to see what’s going on with the water we discharge” so that if, or when, the federal Environmental Protection Agency sets new standard, the facility will be prepared to adapt, Gales said.

“For example, if sometime down the line, the EPA puts a smaller number on how many parts nitrogen your water can be, we’d have to revamp our entire process. We want to be prepared for that,” he said.

The National Pollutant Discharge Elimination System permit program was established in 1972 under the federal Clean Water Act to regulate discharges into U.S. waterways.

Greenville’s Waste Water Treatment Plant, which operates 24/7, must by law have an operator on-site at all hours; Gales oversees a staff of 12 people.

The operators and assistant operators alternate on eight- to 12-hour shifts, during which they are responsible for overseeing the treatment process and equipment, she said.

Gales began at the plant in 1985 as an operating assistant.

Now, as facility manager, she is responsible for complying with federal and state regulations, the latter those of the Mississippi Department of Environmental Quality.

Plants are certified according to their capacity and complexity; the higher the certification, the more wastewater a treatment plant is authorized to handle.

The Greenville facility is a Class 4 facility, the highest category, which requires it to have on staff at least one Class 4-certified employee.

“We offer a lot of training and education opportunities for our workers so that everyone is well-rounded and knowledgeable,” Gales said.

“This also offers our workers a lot of opportunity for promotion. We’re proud of that.”

The Greenville wastewater-treatment plant opened in 1973, a year after the National Pollutant Discharge Elimination System permit program was created.

Before that, Greenville, like any number of cities across the country, discharged untreated sewage into waterways.

“That’s just how things were then,” Jones said. “The facility and the regulations set out by NPDES have prevented Lake Ferguson from becoming the biggest standing septic lake in the country.”

Since it went online, the Greenville treatment plant has undergone several major renovations to meet ever-changing standards set by the EPA.

In the late ‘90s, the aeration system was replaced to employ finer bubbles, resulting in better performance and cutting electricity costs. In 2001, the mechanical aspects of the clarifiers were replaced.

Additionally, “smaller pieces of equipment are being replaced all the time,” Jones said.

A continuously operating facility at some point wears out.

The facility, closing on 50 years of nonstop operation, will have to be retired at some point, he said.

Until then, however, the facility and its employees will continue working around the clock to ensure that only virtually pure water is discharged into the currents of the Mississippi River.