Wpływ procesu elektrochemicznego na stężenie azotu ogólnego i ortofosforanów w odpływie z reaktora z unieruchomioną błoną biologiczną

Municipal and industrial wastewaters discharged to water reservoirs should be characterized by a low load of nutrients. Nitrogen and phosphorus are responsible for eutrophication, is therefore necessary to find the effective solutions for their removal. The experiment has been carried in order to determine the impact of the electric current density on the course of simultaneous electrocoagulation and hydrogenotrophic denitrification in the rotating electro-biological contactor (REBC).The study was conducted in the laboratory scale, parallely in three anaerobic reactors, in conditions of the flow electric current. In the REBC unit, rotating disks made of stainless steel with immobilized biofilm were the cathode. Hydrogen donor produced on the surface of cathode, in water electrolysis process, was used by denitrifying bacteria for nitrates reduction. As the anode an aluminum electrode mounted in the reactors was used. As a result of the anode electrolytic dissolution releasing Al3+ ions combined with the hydroxyl ions emitted on the cathode, formed metal hydroxides, which functioned as a coagulant in the binding of phosphate ions. In crude wastewaters inflowing to the bioreactors the concentration of orthophosphates was 8.1 mgPO4×dm-3 and total nitrogen 81.36 mg Nog×dm-3 and the concentration of organic compounds was equal 40.52 mg O2×dm-3 . The study showed that regardless the operating parameter of the electrolysis process, effluent concentration of orthophosphate below 1 mg PO4×dm-3 was obtained. However, the lowest concentration were observed at a density 0.05 mA×cm-2 . The efficiency of 97.27% corresponded to the phosphate concentration equal 0.22 mg PO4×dm-3. The increase of electric current density resulted in a higher concentration of orthophosphate in the effluent from the reactors, because of more intensive dissolution of aluminum hydroxide with the increase of wastewater alkalinity and a limited amount of secreted Al3+ ions, as a result of aluminum oxide accumulation on the anode surface. In the same time, electrolytically-aided denitrification process affected the reducing concentration of total nitrogen in the wastewaters with the increase of electric current density, as a result of intensive use a hydrogen donor by denitrifying bacteria. The lowest concentration of total nitrogen in the treated wastewaters was achieved at the highest current density 0.1 mA cm-2 – 16.15 mgNog dm-3 , which corresponded to 80.15% effectiveness. The research has shown that bio-electrochemical reactor may be an alternative solution for reactors with suspended biomass designed for nutrients removal.