The digester at Hamilton’s wastewater treatment plant (pictured above) breaks semisolid waste down into methane gas. Whatever sludge remains after this treatment is then pressed dry and landfilled in Pennsylvania. Photo by Diccon Hyatt.

There’s an old saying that goes something along the lines of “filth rolls downhill.” And if you live in Hamilton Township and you follow it downhill far enough, you will eventually end up, as all sewage does, at the lowest point in town, where the wastewater treatment plant, built in 1938, sits on the banks of Crosswicks Creek next to Interstate 195.

The Hamilton Township Department of Water Pollution Control has made headlines recently for being caught in the crossfire of a political dispute between Hamilton and Robbinsville (see the story online at for details on that.)

But however the conflict is resolved, the department’s 58 men and women will keep at their thankless jobs. And if they didn’t, it wouldn’t be long before every home and business in the township became uninhabitable.

Keeping the system running smoothly requires a high degree of know-how from the plant operators who in some cases have been doing their jobs for decades. But the director of the plant, engineer Carrie Feuer, is looking for a new generation of workers to step in as some of the old hands near retirement. Many of the more experienced employees, she says, were hired during a nationwide expansion of wastewater treatment plants in the 1970s and 1980s that happened when the federal Environmental Protection Agency gave grants to municipalities all over the country to improve their sewer systems. As those experts finish their careers they will take with them irreplaceable knowledge.

With an eye to the future, WPC employees like Kelly D. Geiger, regulatory compliance officer, have been visiting area schools to drum up interest in wastewater careers. Geiger, and plant superintendent Fritz Rasweiler recently gave U.S. 1 a tour of the facilities on a hot and drizzly August afternoon to show how it all worked.

The sewage of Hamilton arrives at the plant in a six-foot-diameter pipe, and it leaves in two ways: solid sludge in dump trucks headed for Pennsylvania, where it is landfilled, and in clean water that flowing into Crosswicks Creek, which flows in turn to the Delaware River.

How Stuff Works

It is something of a modern miracle that sewage from your toilet eventually goes back into the drinking water supply of Delaware Valley communities. (Try not to think about what happens upstream.) Before modern sewer systems were constructed beginning in the 1800s, Americans everywhere, including Hamilton, relied on crude and ineffective methods of disposing of household waste. Individual households used “privy vaults” and cesspools. A privy vault was a covered tub beneath the privy that would discharge waste into a nearby cesspool. Cesspools had to be cleaned out regularly or else they overflowed. Even in a well maintained cesspit, waste would leach into the drinking water supply. Aside from being disgusting, this led to outbreaks of deadly disease. For instance, a cholera outbreak killed scores of people in Mercer County in 1832.

Dan Sutton at the control panel in the Operator’s Tower at the wastewater treatment plant in Hamilton. Photo by Diccon Hyatt.

The reason that no longer happens is that all wastewater goes through the treatment plant at Hamilton or others just like it in other communities. The output of the plant is tested regularly and is strictly monitored by various regulatory agencies including the Environmental Protection Agency, the state Department of Environmental Protection, and the Delaware River Basin Commission.

These agencies started cracking down on water pollution after the federal government passed laws such as the Clean Water Act and the Clean Drinking Water Act in the 1970s and 1980s (an important period in the history of sewage treatment.) Before sewage treatment plants were modernized to comply with these laws, the Delaware River was a putrid, stinking mess.

The treatment plant uses physics, engineering, and biology to turn toilet water into something that can eventually become tapwater.

Before wastewater enters the plant, it travels through a series of pipes that collect it from homes and businesses throughout the township, and part of Robbinsville. It mostly flows by gravity, but 28 pump stations scattered throughout town help it over various obstacles. It eventually collects in a 72-inch pipe that feeds into the plant.

The Department of Water Pollution control maintains this entire network and keeps it free from clogs that come up now and then, blasting out blockages with a massive vacuum truck. The biggest culprit in sewer problems is grease dumped into the sewer by restaurants or home cooks who don’t know any better. Geiger said that if there was one thing she hoped people would learn from the article, it would be not to dump cooking oil down the drain, as it can clog up public sewer lines and lead to sewage backups at home.

In most places, residents are on their own when dealing with sewer problems that arise between their homes and the sewer system. But Hamilton Township is unusual in that the DWPC will actually go into the homes of residents and deal with sewer backups. They get hundreds of calls every year, and Geiger says it’s almost unheard of to go a day without one.

After wastewater enters the plant, the first step is to remove large objects. This is done with a screen that collects trash and junk, coffee grounds, gravel and the like. This is where workers sometimes encounter unusual items. Recent discoveries include traffic cones, an eight-foot, length of hose, and jewelry, Rasweiler says. Sometimes people will call the plant to ask workers to look out for a lost cell phone. (It’s unlikely that someone can rescue it. If you flush your phone down the toilet, forget about it, it’s gone.)

Next it goes into a big tank where solids settle to the bottom. Every half hour, these solids are pumped out of the bottom of the tank and into a “digester.” This mix the consistency of pudding. Just like it sounds, the digester is similar in function to a human stomach. It’s even kept at approximately body temperature. Anaerobic bacteria break down organic compounds and produces methane gas, removing 80 percent of the solids in the process. The gas (which to a civilian smells like farts) is used to fuel the boilers that keep the digester at the proper temperature. This process is so efficient that the plant rarely has to use natural gas from PSEG.

A little methane escapes the top of the digester, however, creating an unpleasant odor for anyone standing on top of it taking a picture, but otherwise the grounds don’t smell like one’s worst fears for how a sewer plant would smell.

“Just because it’s a crap plant it doesn’t have to look like crap or smell like crap,” Rasweiler says. “Don’t write that!” says Geiger, rephrasing it more diplomatically: They want to be good neighbors to the homes nearby.

What comes out of the digester is squeezed dry and put onto trucks. One truck a day of this sludge goes to Pennsylvania where it is dumped in a landfill never to be seen again. (Some communities sell the sludge for fertilizer and there is an ongoing debate in the sludge community about whether or not this is a good or safe practice. Hamilton, however, does not.)

That’s the end of the journey for the solid waste. The liquids from the first tank go through several more steps before finally leaving the plant. First, they go through a “clarifier” where giant rotating arms sweep through the water. Any clumps of solids that didn’t get scooped up in the first tank settle to the bottom of this one or float to the surface as scum, which is skimmed off.

Next it heads to one of the more visually impressive rooms. It’s a huge hall in which giant discs rotate, partly dipped in water. The discs are covered with bugs, some of them microscopic (amoebas, etc.) and others large enough to be picked up, such as slugs. These bugs eat pollutants left over from the first two steps. As the organisms grow and multiply, they accumulate on the discs and eventually must be removed or else the shaft that the discs are on could break under the weight. One of the unsung jobs at the wastewater plant is to kill snails that get too big.

After a trip through a final clarifier, the water is treated with sodium hydrocholrite to kill any disease-causing microorganisms. Lastly, a treatment of sodium bisulfate neutralizes the chlorine before it goes into the creek, because chlorine would kill fish just as well as it would germs.

Filling the Pipeline

The entire process is managed from a control room full of computers and video monitors where operators can open valves, turn machines on and off, and keep a lookout for anything going wrong. There are always two operators there at all times. Most of the operators have licenses issued by the state Department of Environmental Protection, which can be earned by taking online courses. The highest licenses, needed to reach higher ranks, require years of management experience to qualify for. Licensing carries over to other jurisdictions, so a license earned in Hamilton will allow someone to operate a plant nearly anywhere in the world.

There are jobs for high school and college graduates alike. Laborers start out mowing lawns but can work their way up to management positions. “It’s not rocket science, but you have to have a good amount of common sense,” Feuer said. “You have to look and you have to listen to see if a machine is making a sound that it shouldn’t … You have to use all your senses. It’s by feel, it’s not just by the book.”

The plant is unionized, with workers being represented by several different unions. Although working at the plant may not carry the allure of a tech sector job for recent graduates, it does come with old fashioned perks like pensions, training, benefits, and job stability. Workers who start there tend to stay for a long time. Geiger has been on the job for 26 years.

At higher levels, there are lab jobs for someone with a biology degree, an environmental degree, and engineering jobs. Feuer, for example, is a licensed civil engineer.

Feuer hopes to keep the pipeline (so to speak) of personnel full so that the plant will be adequately staffed in the future. She says working in pollution control brings satisfaction beyond the good pay and benefits.

“My gratification out of this line of work is helping others and helping the environment,” she says.

Facebook Comments