Abstract
A novel method for removing nitrate in waste water which uses wood chips as a reduction agent and growth support mechanism for denitrification bacteria is studied in this report. A higher denitrification rate was obtained when a portion of the wood chips packed in a column were exposed to air than when all of the wood chips were entirely immersed in solution. Cherry tree chips were more effective than cedar chips, as almost a 100% denitirification rate was maintained for at least 69 days at an inlet concentration of 20mg-N/L and HRT of 20 hr. The denitrification rate decreased significantly when the initial nitrate concentration was increased from 21mg-N/L to 46 mg-N/L. It was possible to use wood chips exclusively as a supply source of organic compounds. An excess amount of organic compounds which is discharged from the reactor can be reduced by passing the solution through a column packed with activated carbon. Cedar chips prepared from a fresh log shortly after cutting were used as a supporting material for denitirification bacteria. A satisfactorily high degree of denitirifation was obtained at HRT of 0.76 hr by adding ethanol as a reduction agent for nitrate.
