Nematode biomass production from sewage sludge as a novel method for circular economy

Sludge generated in urban wastewater treatment plants is a huge environmental and economic challenge of sustainability. Sludge recovery is an environmental necessity and is a requirement for wastewater treatment plants. Predators have been proposed as a biological solution and simultaneously obtaining by-product of interest. Nematodes are predators that are found naturally in sludge but have never been proposed for sludge reduction. In this work, Caenorhabditis elegans, a nematode broadly used for biomedical studies, was used to grow on urban sludge, reaching a remarkable average population up to 92,668 nematodes/mL, 50.6% of sludge was converted into nematode biomass and up to 21.0% of organic matter removed. To demonstrate the viability of this nematode to grow and reduce urban sludges, different experiments in solid and liquid culture media were performed. The physio-chemical composition of the different types of sludges generated in the urban wastewater treatment plants was determined. The total lipids (4.52%, w/w) and fatty acid profiles obtained in the nematode biomass were determined. This work presents a new method to valorise urban sludge and opens the possibility to obtain by-products with high added value.

Automated summary

This study discovered that Caenorhabditis elegans can grow on urban sludge and convert it into nematode biomass while removing organic matter. By conducting different experiments, the feasibility of using nematodes to reduce urban sludges was demonstrated. This work presents a new method for valorizing urban sludge and obtaining by-products with high added value.