Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 372289
Title The effect of operating conditions on aquatic worms eating waste sludge
Author(s) Hendrickx, T.L.G.; Temmink, H.; Elissen, H.J.H.; Buisman, C.J.N.
Source Water Research 43 (2009)4. - ISSN 0043-1354 - p. 943 - 950.
Department(s) Environmental Technology
Publication type Refereed Article in a scientific journal
Publication year 2009
Keyword(s) afvalwaterbehandeling - licht - temperatuur - opgelost zuurstof - ammoniak - lumbricidae - slibzuivering - aquatische wormen - waste water treatment - light - temperature - dissolved oxygen - ammonia - lumbricidae - sludge treatment - aquatic worms - lumbriculus-variegatus muller - benthic invertebrates - water treatment - toxicity - oligochaete - sediments - metabolism - reduction - exposure
Categories Waste Water Treatment
Abstract Several techniques are available for dealing with the waste sludge produced in biological waste water treatment. A biological approach uses aquatic worms to consume and partially digest the waste sludge. In our concept for a worm reactor, the worms (Lumbriculus variegatus) are immobilised in a carrier material. For correct sizing and operation of such a worm reactor, the effect of changes in dissolved oxygen (DO) concentration, ammonia concentration, temperature and light exposure were studied in sequencing batch experiments. DO concentration had an effect on both sludge consumption rate and sludge reduction efficiency. Sludge consumption rate was four times higher at DO concentrations above 8.1 mg/L, when compared to DO concentrations below 2.5 mg/L. Sludge reduction was 36 and 77% at these respective DO concentrations. The effect is most likely the result of a difference in gut residence time. An increase in unionised ammonia concentration drastically decreased the consumption rate. Ammonia is released by the worms at a rate of 0.02 mg N/mg TSS digested; therefore, replacing the effluent in the worm reactor is required to maintain a low ammonia concentration. The highest sludge consumption rates were measured at a temperature around 15 °C, whilst the highest TSS reduction was achieved at 10 °C. Not exposing the worms to light did not affect consumption or digestion rates. High temperatures (above 25 °C) as well as low DO concentrations (below 1 mg/L) in the worm reactor should be avoided as these lead to significant decreases in the number of worms. The main challenges for applying the worm reactor at a larger scale are the supply of oxygen to the worms and maintaining a low ammonia concentration in the worm reactor. Applying a worm reactor at a waste water treatment plant was estimated to increase the oxygen consumption and the ammonia load by 15¿20% and 5% respectively.
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