When the Sewage Sludge Hits the Farm Fields

by Delores Broten

What can we do with sewage sludge? This is an increasingly troublesome issue, as more towns and cities put in efficient water treatment plants to improve the quality of the water they put back into lakes, rivers and the ocean. Back on land, the result is sewage treatment plant sludge, containing valuable nutrients, the toxics of industrial society, and all our diseases. Burning sludge is a nasty pastime, which releases heavy metals and dioxins into the air, and wastes the organic material which has passed through the human digestive tract.

Increasingly, in the United States, Ontario, and now British Columbia, the answer is to landspread it on farms, forests, mines and other contaminated sites. British Columbia has a new draft Regulation, the Organic Matter Recycling Regulation, ready to roll, perhaps as early as December.

As the sludge spreads across the continent, public reaction is also increasing, with lawsuits in the US and with municipalities in Ontario trying to control the problem through local by-laws. Across the continent, sludge activists trade stories of farmers, neighbours and sewage workers who complain that they "break out in spots," and suffer nausea and headaches, or worse, after exposure to some sludges.

Fortunately, a few scientists are also starting to throw more light on the matter. Last fall a US congressional committee reprimanded the EPA for muzzling critics of the US disposal, whether they were citizens or scientists and the basis for EPA standards may undergo a science re-assessment.

In Europe, a serious second look at the practice of land spreading sludge is already under way. For heavy metals, European standards generally are between 5 and 40 times more strict than American ones for sludge and soil levels. The countries closest to the US in their standards are Britain and Canada. In Sweden farmers have refused to put the sludge on their fields for the last year, causing a real waste disposal problem.

BC's new regulations are par for the course. The regulation covers organic material such as yard and food waste as well as manure and human sludge, dividing the compost and "biosolids" into class A and class B, based on level of contamination and requiring treatment for "pathogen reduction." The regulation specifies conditions for composting facilities and for storage.

Standards for the few heavy metals listed in some cases (for example, copper, which is toxic to cows and sheep) seem to even exceed the US numbers which the Europeans consider disastrously high. European studies suggest that some metals are toxic to plants and critical soil bacteria, such as zinc in relation to clover and bean rhizobium. The EU level for zinc in sludge is 300 ppm; the US allows 1400, and BC's new regulation will allow 1850.

The BC regs contain some inordinately complex tables with standards for resulting heavy metal loading in various water media, (groundwater used for human consumption, or livestock, or irrigation), dependant on the acidity levels in the water.

The pathogen level for landspreading of sludge is 2000 fecal coliform per gram for class A sludge and under 2 million for class B. The sludge sites must "not cause pollution," be 30 metres from wells and adjacent property, or 20 m. from major roads. Sites with class B sludge should not have public access and should be posted with signs warning the public not to eat above ground plants for 18 months and root vegetables for 38 months from the site.

The time lines, however, won't affect heavy metal accumulation, and some plants accumulate heavy metals; spinach, kale and lettuce concentrate cadmium, which in turn is directly toxic to humans.

BC will require no testing for other contaminants in urban sludge, such as industrial chemicals, dioxin, or PCBs. In fact, if sites have had sludge applied, they are exempted from BC's contaminated site definition unless there has been a previous industrial facility on the site.

The Georgia Strait Alliance critiqued the BC draft regulations, repeatedly highlighting the lack of monitoring and enforcement at all stages, and calling for testing for further pollutants such as persistent organic pollutants (POPs), nonylphenol and antibiotics, especially in fish farm waste.

Lloyd Manchester of EarthCare, who was the environmental representative on the committee, says: "Participation on the advisory committee was a frustrating experience. Many of our suggestions were not included in the new regulations. We expressed concerns regarding numerous forms of pathogens that need to be considered including potential viruses. These concerns were never addressed. As well, concerns regarding groundwater/airborne contamination and the ability to monitor land use applications have not been addressed."

Is sludge landspreading recycling, or waste disposal? Maureen Reilly, an Ontario activist who has researched the topic, largely at the request of farmers, says that there are a few main points to consider.

First, the pathogens in sewage sludge don't stay on site. "Some become wind-borne," Reilly quotes an Arizona study, which modelled pathogen transport and found that villages 10 kilometres away would be safe from air-borne contamination. That was the good news. The same study found that people exposed to sludge at a 100 metre distance had a 47 out of 100 chance of becoming sick within 24 hours. Reilly points out that the wetter cooler conditions of Canada will allow for longer survival time for the pathogens.

Sludge also escapes when spread on wet soil and, especially in fields with drain tile, can hit the groundwater within five minutes. The Ontario guidelines say sludge should not be spread in the rain, but, as Reilly points out, trucks coming from the city to the farm are not going to turn around and go back with their load. The new BC regs say groundwater must be one metre below the soil, for landspreading to occur, but they don't specify type or depth of top soil, and in rocky BC, that's a problem.

Reilly notes that treatment only reduces the number of pathogens temporarily; they can regrow. She also contemplates the more delicate nuances of the problem — dozens of bacteria, swimming in warm water which contains the anti-microbial cleansers from domestic and industrial use — create conditions for "survival of the fittest of microbes," those with resistance.

Reilly discusses the fact that in Ontario, the use of free sludge skews agricultural economics. While some farmers are paying for normal fertilizers or using green manures, neighbouring farms are degrading the land and neighbours' health, and enjoying lower cost production.

Is there a solution? Can we recover this valuable resource without poisoning our forests, fields and soils, not to mention ourselves? Reilly hopes so. First of all, some serious source reduction of toxics, so that what goes into the sewage treatment plants is good clean organic matter instead of a myriad of toxics from thousands of small urban industries, household cleansers, oils and solvents. Second, complete in vessel composting so that the bugs have lots of time and conditions to do a thorough job of snacking on each other instead of being let loose into the world.

As for the BC regs, Reilly found them "completely unwieldy" and was unable to pick out land application rates (how much you can dump on the same land in how many years), a feature of all other jurisdictions. The Watershed Sentinel couldn't find any application amount limits for sludge "biosolids" either: perhaps those complex tables of limits to heavy metal pollution in soil and groundwater are supposed to provide de facto application rates?

If so, the question remains, who is going to do the monitoring? After all the regulation does provide a penalty for anyone breaking any part of it — a fine of no more than $50,000.

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[From WS December 2000/January 2001]

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