Research on the Electrolytically-aided Denitrification on the Four-stage Rotating Biological Contactor

Favourable solution may be use of electric current flow phenomenon on rotating biological contactor. In some branches of industry such as: metal etching, production of fertilizers and explosives manufacturing wastewater with high concentrations of nitrates V, and low concentrations of organic compounds is produced [19]. Denitrification process of such type of wastewater requires adding an external source of electron donor, such as hydrogen gas. Its low solubility and no need for secondary removal of its excess are its advantages. Sakakibara et al [11, 12] proposed a bio-electrochemical reactor, in which the denitrifying biological membrane is immobilized on cathode. On its surface, as a result of water electrolysis, the hydrogen gas is formed which is used to reduce nitrates. The review of the literature shows there is little effective technological and technical solutions enabling the removal of nitrogen compounds in rotating biological contactors. Therefore, studies were undertaken on a combination of electrochemical processes, occurring during flow of electric current in the wastewater environment with biological processes, occurring in the rotating biological contactor. Subject of this study is research into synthetic wastewater treatment on the four-stage rotating electrobiological contactor (REBC) in two runs. Run I was made with the COD/TN ratio equal to 12, run II - with the COD/TN ratio equal to 6. In both runs were used contactor I, under conventional conditions (lack of current flow), and contactor IT which worked in conditions of current flow with density of 14 mA/m(2). In contactor II disks made of stainless steel with immobilized biological film served as a cathode, whereas an electrode made of aluminum- as an anode. Research has shown that process of removal nitrogen compounds was more effective in system with current flow, then efficiency of nitrification process was equal to 92,79% (run I) and 95,4% (run 2), and efficiency of denitrification process was equal to 58,91% (run 1) and 50,95% (run 2). More effective removal of nitrogen compounds in the denitrification process was obtained as a result of the simultaneous use as an energy source, hydrogen gas produced by electrolysis of water and organic matter contained in the treated wastewater.