By Donella Meadows
–February 20, 1997–
“Biosolids” is what they call it now. It used to be called “sludge.” By any name, it comes out of a sewage treatment plant, and here in the countryside it can cause raging battles.
Wastewater treatment managers, who have tons and tons of the stuff to get rid of, like to spread it on forests or fields. “This option is not only good for the environment, but also cost-effective for the municipality generating the biosolids,” writes David Brennan of the New Hampshire Water Pollution Control Association. He offers a model ordinance that towns can adopt to be sure their sludge-spreading (oops, biosolids distribution) is done safely.
In a recent issue of the Dover NH Foster’s Daily Democrat Brennan’s enthusiasm is countered by a furious objection from Helane Shields of Alton. “Land has been contaminated and rendered useless. Surface and well waters have been polluted. Livestock, pets, fish, birds and wildlife have been killed. People have suffered great losses and lawsuits are pending around the country…. The people of New Hampshire have no way to protect themselves other than to ban sludge dumping town by town.”
So who’s right, the sludge spreaders or the sludge opponents? Well, actually, both.
Biosolids come from those big round tanks in sewage treatment plants, where automatic stirrers and aerators keep the liquid in constant motion. The tanks are full of bacteria that break down organic matter and slurp up nutrients, generating bacterial population explosions. After everything is digested and allowed to settle, the clearish water decanted off the top is chlorinated and released, or perhaps sent to further chemical treatment. The muck that settles to the bottom is the sludge — are the biosolids — whatever.
Sludge is dead bacteria and other organic material, mostly harmless. But if households or industry pour heavy metals (lead, mercury, arsenic, cadmium) down the drain, they will end up in the sludge. If anyone dumps hazardous chemicals into the system, they may survive bacterial breakdown and accumulate in sludge. Disease organisms (cholera, salmonella, dysentery) might be in there too.
So there’s a debate about where to put this stuff. The number one rule of the debate is, Sludge Happens. It has to go somewhere. You don’t get to say “not here” without saying where, or personally agreeing to stop producing it.
You can dump it into a landfill or the ocean. That was the preferred (cheapest) solution for decades, until landfills started leaching, and underwater sludge-heaps began to wash up on shore. Now those depositories are mostly outlawed.
You can burn it in an incinerator and capture some of its energy as electricity or steam (preferably both). The flames will destroy disease-causing bugs and most hazardous chemicals. However, the heat vaporizes heavy metals and sends them out the smokestack, to settle into soil, food, water and lungs. And if there’s any chlorine in the sludge, reactions in the burning chamber may produce dioxins and other nasty pollutants.
You can spread it on land. As long as there’s not too much of it, plants love sludge. Land-spreading is by far the best solution. It recycles nutrients back into life. It improves soils. It replaces manufactured fertilizers, reducing fossil fuel use and water and air pollution. The sale of sludge as fertilizer can even earn income for the sewage treatment district.
The trouble with land application is, if the sludge contains heavy metals or toxic chemicals, they will build up in soils or wash off into waters. If the sludge contains disease organisms, they could be spread back into the population.
As David Brennan tried to say in the Daily Democrat, many communities calmly, steadily, avoid these problems — but not all, which is why sludge opponents like Helane Shields get exercised.
No sludge-disposal method is safe if the biosolids contain heavy metals and toxic chemicals. So industry and households should not be allowed to flush away paints, pesticides, solvents, metals and other nasties. Collection systems are needed for hazardous wastes and stiff fines for noncompliance. Many municipalities have and enforce such laws, even whole countries, such as Denmark.
Next, just to be sure, constant testing is needed. Hanover, New Hampshire, tests before land-spreading and rarely finds heavy metals, except for an occasional “copper spike.” (Someone using algicide in a hot tub?) As long as these spikes are rare and detected, a little high-copper sludge can be diluted with a lot of no-copper sludge, to make a safe fertilizer.
After testing should come composting. Sludge, high in nitrogen, is just what’s needed to help break down high-carbon wastes such as sawdust, leaves, or shredded paper. The composting process heats the mixture up, destroying pathogens. The product is odorless and safe and valuable. For decades the city of Milwaukee has marketed bags of “Milorganite” fertilizer, made of composted sludge and beer-brewing waste.
Composting has to be done right, under a roof, with frequent aeration, controlled runoff, proper ingredients, and meticulous testing. “You have to be very careful, just like making a cake,” says Bill Hochstin, facilities manager at Dartmouth College, who has helped design a new composting plant, which will process biosolids, yard waste, used paper towels, and food scraps from college dining halls.
The problem comes from those who are not careful. Testing and composting are much more expensive than dumping. Tidy profits can be made trucking raw biosolids of unknown content to states, towns, or farms that ask no questions. Campaign contributions flow to keep standards low and regulations lax.
Biosolids could be a boon, not a problem, a source of public income, not public battle, if they were well-regulated and handled by honest, competent local or state governments. And to shut down the business of hauling the nastiest stuff to the most dishonest or incompetent places, we need tough federal standards.
Which brings us, as almost every topic does, to campaign reform.
Copyright Sustainability Institute 1997