Floating bed biology
The floating bed biology ( English moving bed biofilm reactor ), also called fluidized bed biology or fluidized bed biology , is a method of biological wastewater treatment in which the microorganisms involved in the degradation processes grow in a biofilm that is immobilized on an artificial carrier. It is one of the biological biofilm processes in wastewater treatment. In contrast to fixed bed biologies, the carrier is not fixed or firmly anchored, but moves freely in the reactor.
(Engl. The support materials or packing carrier ) are often small, a few centimeters tall, cylindrical or spherical plastic bodies used, mostly of polyethylene exist. These are often provided with inner bars, hairs or protuberances in order to increase the potential settlement area. Both white new material and black packing made of recycled material are used. New material is suitable for drinking water, while recycled material tends to settle faster. The materials offered are not comparable or classifiable with regard to their relevant surfaces and structures.
An important factor in the biological fluidized bed process is sufficient and frequent contact between waste water constituents and the microorganism embedded in the biofilm . The necessary mixing of the carrier media in the reactor can be achieved in aerobic processes through the necessary ventilation. In anaerobic processes, the packing can be swirled in the bioreactor by pumping water or by submerged, slowly rotating agitators .
The quality and thickness of the biofilm that ultimately forms on the carrier material is not only influenced by the shear forces that prevail in the bioreactor , but also by the composition and pollution of the wastewater (substrate). The more the wastewater is contaminated with biodegradable ingredients, the stronger and faster the growth . With the relatively frequent use of floating bed biology for the purification of heavily polluted waste water from the waste paper processing industry, only a few days are observed to reach the existence phase of the biofilm or the desired degradation rate. The biofilm thickness can then be several centimeters.
The transport of the oxygen and the dissolved waste water constituents (substrate) to the microorganisms embedded in the biofilm and the removal of the metabolic products from the biofilm takes place by diffusion . Depending on the oxygen concentration, the composition of the biofilm and the substrate, this usually takes place up to a biofilm depth of around 100 to 500 micrometers . Problems with decreasing degradation capacity are often justified by the fact that the biofilms on the carriers become too thick and the effective area of the carrier material decreases. Another disadvantage of floating bed biologies is the relatively high energy requirement for mixing.
The advantages include dispensing with sludge recirculation (compared to conventional processes with suspended biomass, activated sludge processes ), high process stability against impact loads and malfunctions, and the possibility of establishing slowly growing microorganisms on the carrier that specialize in poorly degrading compounds.
Individual evidence
- ↑ Biological and advanced wastewater treatment. 4th edition, VCH, 1997, ISBN 3-433-01462-0 (Chapter 4, ATV manual).
- ^ S. Wuert, P. Bishop, P. Wilderer: Biofilms in Wastewater Treatment: An Interdisciplinary Approach. Iwa Publishing, 2008, ISBN 978-1843390077