Anaerobic treatment is now becoming a popular treatment method for industrial wastewater, because of its e?ectiveness in treating high strength wastewater and because of its economic advantages. Developed in the Netherlands in the late seventies (1976-1980) by Prof. Gatze Lettinga - Wageningen University, UASB (Upflow Anaerobic Sludge Bed) reactor was originally used for treating wastewater from sugar refining, breweries and beverage industry, distilleries and fermentation industry, food industry, pulp and paper industry.
Anaerobic processes in the UASB Reactor
As it is showed in the figure, water is distributed from the bottom of the reactor and moves upward through a bed of sludge. The most important elements of the machine are the water distribution system, the gas-solids separator and the water outlet system.
There are 4 phases of anaerobic digestion in an UASB reactor:
- Hydrolysis: where enzymes excreted by fermentative bacteria convert complex, heavy, undissolved materials (proteins, carbohydrates, fats) into less complex, lighter, materials (aminoacids, sugars, alcohols...).
- Acidogenesis: where dissolved compounds are converted into simple compounds, (volatile fatty-acids, alcohols, lactic acid, CO2, H2, NH3, H2S ) and new cell-matter.
- Acetogenesis: where digestion products are converted into acetate, H2, CO2 and new cell-matter.
- Methanogenesis: where acetate, hydrogen plus carbonate, formate or methanol are converted into CH4, CO2 and new cell-matter.