The role of micro-aeration-based processes for the valorisation of polluted sludge to value-added chemicals

Industrial and municipal biological wastewater treatment plants (WWTP) generate vast amounts of sludge (SS) as a by-product.

The total annual production of sludge currently surpasses 13 million tonnes of dry solids (DS) in the EU, even excluding sludge production from industrial on-site WWTP.

Sewage sludge (SS) mainly contains non-toxic organic matter that can be converted to value-added compounds such as carboxylic acids, alcohols, and energy carriers.

Furthermore, macronutrients such as nitrogen and phosphorus and micronutrients (e.g., potassium and iron) that are essential for crop growth are present as well, making sludge an interesting organic fertiliser.

However, mainly depending on the composition of the wastewater and the pollutant’s biodegradability, SS typically contains various potential hazardous contaminants (OMP) such as adsorbable halogenated organic compounds (e.g., PFAS, AOX), phenols, sulfates, aromatics, active pharmaceutical ingredients (APIs) (e.g., antibiotics, endocrine disruptors), pathogens (viruses, bacteria, etc.), microplastics and heavy metals (HM).

It is clear that there is an urgent need for technological strategies that tackle both the increasing presence of contaminants in sludge and allow efficient resource recovery from sludge.

However, current alternative sludge management strategies fall short to properly respond to the growing demands of a sustainable society and unfortunately, a significant amount of sludge is incinerated or (even worse) landfilled.OXYCON will therefore explore the use of micro-aeration as an innovative technique to simultaneously (i) degrade selected OMP, (ii) remove HMs, and (iii) enhance carboxylic acid production as biobased chemical building block during (subsequent) anaerobic fermentation of the treated sludge.

The potential of air will be researched via two different techniques: air-assisted ultrasonication and micro-aeration-based anaerobic fermentation.