P-nitrosodimethylaniline (RNO)-based evaluation of enhanced oxidative potential during electrochemical treatment of high-salinity wastewater.

The electrochemical bleaching of p-nitrosodimethylaniline (RNO) was investigated in order to apply its reactions to evaluating electrochemical oxidation. The bleaching rate of RNO during electrochemical treatment was accelerated by the presence of chloride ions. The initial bleaching rate of RNO was found to be accelerated during the electrolysis of NH4Cl, suggesting that electrochemically generated chloramines are sufficiently strong oxidants to convert RNO. A method of evaluating direct or indirect oxidative potential for electrochemical treatment was proposed, provided that the initial bleaching rate of RNO is consistent with low concentrations of RNO. The saline wastewater of Japanese pickle production processes (brown mustard and Japanese radish) was electrochemically treated. The ammonium ion (18 and 8 mg L(-1)) was almost completely removed after 1 h of treatment in the presence of NaCl (3%). The removal rate of total organic carbon (TOC) exceeded 90% for 7mgL(-1) and 60% for 352mgL(-1), indicating that electrochemical treatment is useful in removing ammonium ions and organic substances from high-salinity wastewater.