Municipal wastewater treatment serves to remove contaminants and prevent them from being discharged into waterways causing contamination with eutrophication problems and other associated environmental impacts.
A certain portion of the contaminants is literally removed and degraded by the process used, but a large portion of the nutrients such as nitrogen and phosphorus, organic matter, metals and several emerging contaminants are simply transferred to the sewage sludge, called biosolids, or “human manure”.
The volume of these biosolids is immense and their fertilizing value is very precious, especially in this tense geopolitical period where we do not want to depend on chemical fertilizers imported from autocratic and warlike countries and where the increasing cost of these fertilizers is greatly affecting profitability. of our agricultural producers who are already under multiple pressures.
Biosolids potentially offer a green alternative to chemical fertilizers.
Recent Radio-Canada reports on Green Week and to Survey pointed out that some biosolids that appear to be imported from the United States were contaminated with PFAS, also called Forever Chemicals. These PFAS are ubiquitous and we detect traces of them everywhere. It should be understood that the more worrying results on PFAS concentrations concern only two samples of biosolids of unconfirmed origin and that several preliminary results that we have in my laboratory for biosolids from Quebec municipalities are very low, comparable or more lower than the background noise levels observed in farmyard manure or commercially available compost from garden centres.
Sufficient local production
I think it is justified to prohibit the use and import of foreign biosolids, we produce enough of it here and it seems to be of better quality and with levels of contaminants such as PFAS which seem much lower and safer. It would be very unfortunate to prohibit the agricultural recovery of Quebec municipal biosolids, our farmers need these fertilizers and the alternative would be an environmental disaster. The biosolids recovered in our soils build soil organic matter which thus acts as a carbon sink and the biosolids replace chemical fertilizers which have a huge environmental footprint. Conversely, biosolids that will not be recovered will likely need to be incinerated (using hydrocarbons to burn organic matter – with a huge carbon footprint).
Landfilling biosolids is not a viable solution with all the associated environmental impacts, risks of contaminating the water table and space availability issues in our landfill sites.
I understand the concern of the agricultural community for whom the health of the soil is essential, the solution to make it possible to valorize Quebec’s biosolids is to properly analyze the products generated in different municipalities to reassure both those who should spread these biosolids on their soils and the cities that produce them and that don’t want to cause environmental problems. We can therefore very well check the concentrations in biosolids before their recovery and thus avoid the risk of contaminating our soils by establishing PFAS thresholds not to be exceeded (this is precisely the objective of an ongoing project, carried out jointly by the Quebec Ministry of the Environment and Professor Sauvé).
The various levels of government should also ban the use of the extended family of PFAS to prevent these products from ending up in our soils, water, air and food. The most contaminated biosolids are usually because there is a plant that produces PFAS or uses PFAS and the wastewater from that plant contaminates all of the biosolids generated in that city. Contrary to the United States, we have few of these types of processes in Quebec and we can believe that the majority of our biosolids are safe, we simply have to analyze the various sources to identify the problematic cases that we could have we.
The formula is a bit worn, but don’t throw the baby out with the bathwater!