Wonderful sludge eating worms unravelled

Wastewater Treatment, Nutrient Factory

In order to address the limiting factors of hydrolysis and increase the overall value of wastewaters, the EnzyFOR project was commenced. EnzyFOR stands for the Enhanced Enzymatic Anaerobic Fermentation of Organic Residues. The main aim of EnzyFOR is to increase the valorisation of waste streams, such as agricultural and domestic waste by the utilization of enzymes to produce volatile fatty acids (VFA’s) from the complex organic substrates present in the wastewater.

VFA’s are important precursors for bio-chemical processes of which biogas is the least valuable in terms of market price and environmental effects. As a means to investigate methods for improving the extent and rate of hydrolysis, the efficient sludge degrading aquatic worms, T.Tubifex were designated as research target. The research sets out to find worm-based enzymes for the improvement of sludge hydrolysis.

- Steef de Valk (TU Delft)
- Ahmad Khadem (WUR)
- Merle de Kreuk (TU Delft)
- Jules van Lier (TU Delft)


The aquatic worms, T. Tubifex degrades activated sludge efficiently. Solids reduction of 40% can be reached in 3 to 4 days as opposed to anaerobic digestion that needs about 30 days to reach similar solids reduction. Additionally, upon anaerobic digestion of the predated sludge solids, a total of 50 – 60% solids can be removed. This indicates that the solids reduction system can be improved by at least 10%.

Aquatic worms predominantly consume the protein fraction in the sludge. Intestinal bacteria and the aquatic worms degrade the protein in synergy. About 60% of the protein degrading activity is associated with the aquatic worms. Sludge predation results in a small increase in protein degrading enzymes. It remains unknown as to who (the worms or the intestinal bacteria) produces these enzymes as predation results in a bacterial community that is related to protein degradation.

Start of Research
January 2012

End of Research
January 2016


- TU Delft
- Delfluent Services B.V.
- Tauw B.V.
- Royal Cosun







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