Effects of electric voltage and sodium chloride level on electrolysis of swine wastewater

The effects of electric voltage and NaCl concentration on the removal of pollutants in swine wastewater were investigated to determine the optimum operation conditions for a designed electrolysis process. An up-flow electrolytic reactor was fabricated from Plexiglas, and one titanium anode coated with iridium oxide (IrO2) and two stainless steel cathodes were installed in it. The anode surface area was 80 cm2/L and the hydraulic retention time (HRT) was 6 h. The results indicated that the pollutant removal was highly proportional to the electric voltage and removal could be enhanced by adding NaCl. The removal efficiencies of NH4-N, soluble nitrogen (NH4-N plus NOx-N), soluble total organic carbon (STOC), and color were proportional to the NaCl level up to 0.05% NaCl level, beyond which no further enhancement in removal was observed. However, such a tendency was not observed in the case of PO4-P removal. The obtained results indicate that 7 V and 0.05% (8.56 mM) NaCl level would be the optimum conditions for the designed electrolysis process. Under these conditions, the average removal efficiencies of NH4-N, soluble nitrogen, PO4-P, STOC, and color were 99%, 94%, 59%, 64%, and 93%, respectively.