Baltic Breakfast: Sewage sludge - a resource and a problem 

17 April 2024.
Sewage sludge - the residual product of municipal wastewater treatment plants - has been seen as both a valuable resource and a problematic disposal issue.
Wastewater treatment plants collect various residual streams from society - everything from toilet waste, bathing, dishwashing and clothes-washing water to storm water runoff. Society's use of various chemicals as well as valuable phosphorus and nitrogen are ultimately found in the sludge.
Phosphorus is a finite resource that need to be protected. Today, phosphate rock is mined to produce mineral fertilisers for use in agriculture. The total use of fertilisers in agriculture - manure and mineral fertilisers - must become more efficient in order to reduce the risk of nitrogen and phosphorus leakage and thus the risk of freshwater and marine eutrophication. Returning more of the sludge phosphorus to agriculture increases the circulation of nutrients and reduces dependence on imported mineral fertiliser. But society is striving after "pure" phosphorus and not a sludge fraction containing contaminants. Are there proven technologies to recycle phosphorus from wastewater and sludge? And are these being implemented? What are the obstacles involved?
If phosphorus cannot be easily extracted is it reasonable to apply sludge to arable land as a fertilizer? What has Sweden’s REVAQ sludge certification program done to ensure safety? What happens to pollutants, including microplastics, spread on agricultural land? Can they be transported to surrounding waters and our oceans or do they accumulate in the soil?
Listen to a seminar where we discuss both the extraction of phosphorus from sludge and what happens to pollutants in sludge when they are spread on arable land!
Participants:
Arno Rosemarin, Senior Research Fellow at Stockholm Environment Institute
Geert Cornelis, Researcher at the Department of Soil and Environment; Soil chemistry, Swedish University of Agricultural Sciences
Moderator: Gun Rudquist, Head of Policy at Stockholm University Baltic Sea Centre.

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