Chemical Engineering

Many sources of water, especially in areas of intensive agriculture, contain intolerable levels of nitrate concentrations. Applications of biofilms for denitrification purposes has been recommended in the waste- water and drinking water industries. Normally, denitrification refers to the biological process by which microorganisms oxidize a carbon source to CO2 while reducing NO3 to N2 in a 2-3 step biological process. Problems of environmental contamination due to the use of organic carbon sources lead to the suggestions to use H2 in denitrifying biofilm systems. Application of electrochemistry in conjunction with biofilm for denitrification is a relatively recent development. Microorganisms can use the electrolytically produced H2 to reduce NO3 to N2. The research presented in this thesis addresses the application of electrochemical principles to enhance the biological denitrification process. As hydroxide is produced in the denitrification process, there is an inevitable increase in pH. Biofilm activity at various pH was studied under the experimental conditions; biological activity was observed even at pH as high as 13, though loss in biological activity was observed at pH 12 and above. The possibility of a direct electrochemical reduction of nitrate along with the biological denitrification was explored and verified to gain a valuable insight into the mechanism of this process. Microsensors for specific ions (NO3 ' NH4+, pH) and H2 were developed and used for the measurement of the respectiv