The SYVAB company has extended the plant with a fluidized bed for post denitrification. The method was chosen mainly for two reasons. First, the relatively low investment cost and second, the flexibility in the process to adjust the discharged nitrogen according to the circumstances in the recipient. Start-up took place in April 1997 with an adaption period of four weeks. From mid September the same year the plant has been in full denitrifying operation. The average nitrate-nitrogen reduction rate has been 90% with 1.9 mg NO3–N in the outlet. Methanol is used as external carbon source. At the present purification rate the cost for total nitrogen reduction is 18 SEK (2.25 USD)/kg N.
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