In this biological nitrate removal study, the performance of the bacterial strain Acidovorax avenae subsp. avenae LMG 17238 using different carbon sources such as ethanol, methanol, sodium acetate, glucose and poly (epsilon-caprolactone) was investigated. Additionally the parameters such as an increase of nitrate concentration, carbon source amount (C/N) and dilution of a synthetic medium were studied. In laboratory conditions LMG 17238 and a mixed bacterial culture (soil suspension, wastewater treatment and macro algae Gracilaria verrucosa) have been immobilized as a comparative study to determine their efficiency in the biological denitrification of drinking water. For the continuous system as a carbon source, G. verrucosa was studied in fixed-bed columns. Various variables such as hydraulic retention time (HRT), mass amount of the substrate, and the initial nitrate concentration were investigated. A comparative study was achieved by using biodegradable poly(c-caprolactone) as a carbon source using a mixed bacterial culture (LMG 17238 and G. verrucosa) in a fixed-bed column. Also Monod type equations were used to model the denitrification kinetics. The study proves that, LMG 17238 can be successfully used with different carbon sources. G. verrucosa can be considered as a promising alternative to poly(c-caprolactone) with a maximum denitrification rate of 13.83 and 0.94 mg NO3-N/L d respectively. (C) 2011 Elsevier B.V. All rights reserved.