Attempts to increase the efficiency of nitrate reduction process in biological municipal sewage treatment “MEANDER”

In this work the attempts to increase the efficiency of nitrate reduction in denitrifyingbacteria cells were made. The experiments were carried out in biological municipal sewage treatment plant “MEANDER”. Two different tests were used. One procedure was based on theprolongation of the sedimentation time in order to decrease the level of inhibiting O2 in thesewage (it is respiration by aerobic microorganisms). The level of NO3 was increased in thistest compared to 6 h “standard” alternate sedimentation/aeration, but the speed of nitratereduction was not so satisfactory. The other procedure involved attempts to increase the numberof denitrifying bacteria in the sedimented chamber. The denitrifying bacteria originated from rowsewage-sludge or from a prepared in advance culture of Pseudomonas stutzeri. Pseudomonasaerogenes and Bacillus sp. The effects in both tests show the increase in speed of nitratereduction, particulaiy after 24 h from the addition of the culture prepared in advance. However,the disadvantage of the second way was introducing additional NO3 together with the bacteria.