Sludge reduction by aquatic worms in wastewater treatment : with emphasis on the potential application of Lumbriculus variegatus

Abstract

In wastewater treatment plants (WWTPs), large amounts of biological waste sludge are produced. In the Netherlands, the application of this sludge in agriculture or disposal in landfills is no longer allowed, mainly because of its high heavy metal content. The sludge therefore generally is incinerated. Sludge processing costs are estimated to be half of the total wastewater treatment costs. This thesis focuses on the application of aquatic worms to reduce the amount and volume of the excess sludge. Several worm species, belonging to the Aeolosomatidae, Tubificidae (including Naidinae) or Lumbriculidae have specific characteristics that could make them suitable for such an applicatio