Aquatic worms eat sludge: Mass balances and processing of worm faeces

• Published in: Journal of hazardous materials Vol. 177; no. 1; pp. 633 - 638
• Main Authors: Hendrickx, T.L.G., Temmink, H., Elissen, H.J.H., Buisman, C.J.N.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15-05-2010; Elsevier
• Subjects: Animals; Applied sciences; Aquatic worm reactor; Biodegradation, Environmental; Biological sludge; Biomass; Bioreactors; Chemical engineering; Dewatering; Exact sciences and technology; Faeces; Feces - chemistry; Food; General purification processes; Liquid-liquid and fluid-solid mechanical separations; Lumbriculus variegatus; Mass balance; Methanisation; Nutrients; Oligochaeta - metabolism; Pollution; Reactors; Reduction; Settling; Sewage; Sewerage works: sewers, sewage treatment plants, outfalls; Sludge; Waste Management - methods; Wastes; Wastewaters; Water Purification - methods; Water treatment and pollution; Worms; Aquatic worm reactor; Mass balance; Lumbriculus variegatus; Dewatering; Methanisation; Biological sludge; Metabolite; Waste treatment; Reuse; Phosphorus; Biomass; Nitrogen; Dehydration; Sedimentation; Anaerobic digestion; Sewage treatment plant; Heavy metal; Biological treatment; Reactor; Degradation product; Material balance; Thickening; Handling
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2009.12.079

Reduction of the amount of waste sludge from waste water treatment plants (WWTPs) can be achieved with the aquatic worm
Lumbriculus variegatus in a new reactor concept. In addition to reducing the amount of waste sludge, further processing of produced worm faeces and released nutrients should also be considered. This study gives the mass balances for sludge consumed by
L. variegatus, showing the fate of the consumed organic material, nutrients and heavy metals associated with the sludge. A distinction is made between conversion into worm biomass, release as dissolved metabolites and what remains in the worm faeces. The results showed that 39% of the nitrogen and 12% of the phosphorus in the sludge digested by the worms are used in the formation of new worm biomass, which has potential for reuse. Experiments showed that settling of the worm faeces leads to a factor 2.5 higher solids concentration, compared to settling of waste sludge. This could lead to a 67% reduction of the volumetric load on thickening equipment. The worm reactor is expected to be most interesting for smaller WWTPs where a decrease on the volumetric load on sludge handling operations will have most impact.