Autotrophic Denitrification by Thiobacillus Denitrificans with Thiosulphate as Sole Energy Source. Pilot Scale Experiments at Low Temperature

In order to achieve the biological removal of nitrate of groundwater, the denitrification properties of an environmental strain of Thiobacillus denitrificans were studied at a pilot scale. This strain was previously described and showed good denitrification abilities at low temperatures. Its mean nitrate removal velocity was twice as great at 10°C, than at 20°C. A pilot plant in fixed bed conditions, filled with a pouzzolane / Neutralg® mixture was used for this purpose. The feed solution was tap water to which only nitrate and thiosulphate were added; the temperature was 10°C. An optimum volumetric nitrate loading rate of 1.5 kg N-NO3 −. m−3 d−1 was determined for which 100 % denitrification yield was reached. The maximum volumetric nitrate loading rate of the plant was evaluated. The influence of the operating conditions such as residence time and nitrate concentrations were investigated as well as the efficiency of the plant by studying molar ratios between the removed and released products.