Removing nitrate with a methylotrophic fluidized bed: technology and operating performance

A flow diagram is presented of a pilot plant used to study the removal of nitrate from water in a biological fluidized bed of sand, with added methanol as a source of carbon. The process provided long-term stable operation even at low temperatures and with high volumetric loadings and short retention periods. At 3.5C, a nitrate removal efficiency of 9 kg per m3.d was achieved. When the influent contained 75 mg nitrate per litre, complete removal of nitrate was achieved at an empty bed contact time of 15 minutes. Provided that there was a slight excess of methanol (1-2 mg per litre), no nitrite was detected in the effluent, and surplus methanol was easily removed during subsequent water-treatment processes. The pilot-scale results have been used to establish design data for a full-scale plant at De Blankaart, Belgium. There are 62 references. (see also following abstract).