As industry continues to develop, the amount of various recalcitrant substances that cannot be removed by conventional wastewater treatment has increased in modern society. The SCFs (Soluble Cutting Fluids) used in metalworking processes contain many chemical substances, such as mineral oils, anticorrosive agents, extreme-pressure additives and stabilizers, as well as high concentrations of organics. Recently, electrolysis has been expected to become an alternative to conventional processes and to be useful in various wastewater treatments. Electrolysis is a highly adaptable industrial wastewater treatment method, having a high efficiency, short processing time, and simple equipment composition, regardless of the biodegradable nature of the contaminants. The effects of operating time, current density, and electrolyte on COD removal of waste SCFs have been studied using the stainless steel (SUS316) electrode in a batch type reactor. The results were as follows. ① Without electrolytes, when the current density was adjusted to 40 A/m2, 60 A/m2, and 80 A/m2, the removal efficiencies of the COD were 25.0%, 37.7%, and 49.1% after 60 min, respectively. ② In the comparison between NaCl (5 ~ 10 mM) addition and non-addition, the removal efficiency with NaCl was higher than for without after 60 min for all current densities. ③ In the comparison between Na2SO4 (5 ~ 10 mM) addition and nonaddition, the removal efficiency with Na2SO4 showed no significant difference to that with NaCl at all current densities.

An electrochemical treatment has great efficiency for the removal of non-biodegradable material and it has high applicability in wastewater treatment due to its short operating time. The purpose of this study using an electrochemical process is to provide fundamental data on the cutting fluid treatment, which has difficulties in the treatment of nonbiodegradable material. The results are as follows. Experimental data in relation to applied voltage and concentration of NaCl are outlined. With no addition of NaCl, and an applied voltage of 5 V, 10 V, or 15 V for 60 mins, the removal rates of CODMn were 29.87%, 55.32%, and 67.27% for each voltage. The removal rates of CODCr were 39.51%, 70.73%, and 85.37%, respectively. The removal rates of CODMn and CODCr increased with increasing applied voltage. These experimental results showed that the removal rate of COD with varying concentrations of NaCl (0 mM, 5 mM, 10 mM) increased increasing NaCl concentration.