The city of Hamilton continues to grapple with what to do over the long term with the 40,000 tonnes of wet sewage sludge produced each year at the Woodward Ave Sewage Treatment Plant (STP).
Sludge is generated as a result of contributions from you and me and every other Hamiltonian who flushes a local toilet. Add to the toilet flushing the fact that many local industries also discharge their wastewater into our sewer system, and you end up with a big, messy problem with no easy solutions. The sludge generated at our centralized sewage treatment plant is laced with everything from pharmaceutical drugs and pathogens to heavy metals and other toxic contaminants discharged from local industry.
This creates problems for final disposal of the sludge; whether you spread it on farm fields or burn it in an incinerator, contaminants found in the sludge can get out into the environment.
In the case of land application, the more contaminated the sludge is, the more limited your options are for final disposal. The Ontario Ministry of the Environment regulates the land application of sludge through requirements in the provincial Environmental Protection Act and the Nutrient Management
Act. Levels of heavy metals in the sludge, such as mercury, lead and cadmium, drive regulatory decisions regarding how much and how frequently a given municipality’s sludge can be spread on farm fields.
Visit
www.ene.gov.on.ca/environment/en/subject/biosolids/ for detailed information on the province’s regulatory framework.
In the case of incineration and other thermal destruction technologies, Ontario’s Green Energy Act includes sewage sludge in the definition of ‘biomass’, which is categorized as renewable, green fuel.
This has led to a fast-tracking of the approvals for facilities that are proposed to generate energy-from-waste using sewage sludge as a fuel. The problem, however, is that sewage sludge is simply not a good source of energy as it exhibits a very low BTU value (BTU or ‘British Thermal Unit’ is the measurement of heat created by burning any material). Even with the best pollution control technologies, thermal destruction of sewage sludge results in the emission of contaminants including heavy metals and cancer-causing dioxins into our air.
City Council is currently divided over how to manage Hamilton’s sludge over the long term. The majority of councillors support incineration as the preferred long-term management solution. Yet to be determined is whether the city should build its own incinerator or whether a partnership should be
struck with Liberty Energy, the US-based company that has already secured approval to build a large (500,000 tonnes per year) gasification plant on Strathearne Avenue in our industrial core. Other councillors believe that Hamilton’s current practice of land-applying our sludge should continue as this is the most cost-effective option. Further, they argue, the quality of our sludge continues to improve through municipal efforts to eliminate contaminants, making Hamilton eligible to spread more sludge
more frequently on the fields of willing farmers.
Environment Hamilton continues to weigh in on the debate over the management of Hamilton’s sludge.
Right from the start, we have opposed the plans for Liberty Energy’s sludge gasification plant . We are concerned about the size of the Liberty facility and the fact that it is to be built down on Strathearne Avenue in an already compromised airshed. Hamilton’s industrial core can’t tolerate another source of air contaminants, even if that facility demonstrates that it will be in compliance with provincial air regulations. Ontario regulates air emissions on a facility-by-facility basis, without taking into consideration the cumulative effects of exposure to air contaminants. While this might work well in a
one-industry town, it’s not an adequate approach in an industrialized city like Hamilton. The air quality monitoring done as part of the approvals for the Liberty plant confirm that the facility will contribute substantially higher levels of pollutants than the smaller sludge incinerator being proposed by the city (see bar graphs). Further, the company plans to import sludge from municipalities as far as 70 km away, generating increased truck traffic in order to bring sludge to a facility that will discharge more contaminants into our compromised airshed. It’s worth noting that, at this point, the company has not yet succeeded in securing even one contract with another municipality.
But EH is also concerned about the implications of spreading sewage sludge on farm fields. While the province has rules in place to regulate this practice, the reality is that land application of sludge does result in contaminants getting into the environment and, some argue, into the crops grown on
those fields. We continue to push for the municipality to take measures to improve the quality of the industrial discharges making their way to the Woodward Avenue STP. On a positive note, our Public Works Department has reported that the quality of Woodward sludge has improved over the past 3
years, with testing confirming that levels of heavy metals in the sludge are decreasing. This is the result of a ramped up effort by the city to enforce its sewer use by-law. We applaud the city’s progress to date and encourage Public Works to continue with this effort.
We also believe the city could be doing other things with sewage sludge after proper conditioning.
Other municipalities are exploring a broader range of beneficial uses for their biosolids. This can include using biosolids to condition soil used to landscape brownfield sites, as a fertilizer in the forestry industry, or in other land reclamation activities. Utilizing the nutrients available in sewage sludge would seem to be a far more prudent practice than attempting to extract limited energy through thermal destruction of sludge via incineration or gasification. The soundness of this approach will become more obvious
as we approach ‘peak phosphorus’. The planet’s phosphorus reserves are running out, with estimates
that the planet will reach peak phosphorus in the next 30 to 40 years. When we reach this point, we will be actively searching for sources of phosphorus to fertilize our agricultural fields. It would seem prudent to invest some energy now into determining how to clean up our sewage sludge to the point
that the nutrients can be used safely. Some day we will be calling our cleaned up, conditioned sewage sludge ‘black gold’.
What can you do to help?
-Don’t ever flush expired pharmaceutical drugs down the toilet.
-Return expired pills to your local pharmacy or to one of the city’s municipal recycling centres where they will be accepted at no cost for proper disposal.
-Ensure that your household cleaners and personal care products are eco-friendly.
-Anything you flush down the toilet or drain out of a sink or bathtub ends up at the sewage treatment
plant.
-Using eco-friendly household cleaners, shampoos and soaps ensures that you are not contributing to the sludge contamination problem.
-Never dump old paint, varsol or other household chemicals down the drain. Use these items carefully – choose the most eco-friendly options out there. -And be sure to carefully collect up any liquid waste resulting from the use of these products and take to a municipal hazardous waste depot for proper disposal.
