Conventional wastewater treatment plants (WWTPs) do not fully remove micropollutants. Enhanced treatment of sewage effluents is being considered or implemented in some countries to minimize the discharge of problematic micropollutants from WWTPs. Representative enhanced sewage treatment technologies for micropollutant removal were reviewed, including their current status of research and development. Advanced oxidation processes (AOPs) such as ozonation and UV/H2O2 and adsorption processes using powdered (PAC) and granular activated carbon (GAC) were mainly discussed with focusing on process principles for the micropollutant removal, effect of process operation and water matrix factors, and technical and economic feasibility. Pilot- and full-scale studies have shown that ozonation, PAC, and GAC can achieve significant elimination of various micropollutants at economically feasible costs(0.16-0.29 €/m3). Considering the current status of domestic WWTPs, ozonation and PAC were found to be the most feasible options for the enhanced sewage effluent treatment. Although ozonation and PAC are all mature technologies, a range of technical aspects should be considered for their successful application, such as energy consumption, CO2 emission, byproduct or waste generation, and ease of system construction/operation/maintenance. More feasibility studies considering domestic wastewater characteristics and WWTP conditions are required to apply ozonation or PAC/GAC adsorption process to enhance sewage effluent treatment in Korea.

The salt water generated from the salting process of kimchi production is difficult to treat biologically due to very high content of salt. When salt water is treated and discharged, it cannot satisfy the criteria for effluent water quality in clean areas, while resources such as the salt to be recycled and the industrial water are wasted. Therefore, in order to recycle salt water and improve the economy of kimchi production process, a basic study was conducted on the treatment using electrochemical oxidation of organic acids and organic matters existing in large volumes of salt water. The electrochemical treatment of organic matters has advantages over conventional methods such as active carbon absorption process, chemical oxidation, and biological treatment because the response speed is faster and it does not require expensive, harmful oxidizing agents. In this study, the electrochemical oxidation characteristics according to current density and pH were evaluated with acetic, lactic, and formic acids existing in large volumes of salt water. Acetic acid was refractory to electrochemical oxidation regardless of current density, while lactic acid showed high removal efficiency even at low amount of current. Furthermore, formic acid showed the highest current efficiency for the first 20 minutes and its removal rate increased together with the amount of current. In the experiments with the initial pH set to 4, 7, and 10, the removal rate of organic acids tended to be higher at lower pH values. Because NaCl was used as the electrolyte, HOCl was produced at pH 4 and OCl− increased at pH7. The germicidal power of HOCl is about 40-80 times higher than that of OCl−. For this reason, the generation of HOCl with excellent oxidizing power increased at pH 4 and the highest removal rate was achieved. Furthermore, as salt water contains various organic matters, an experiment on organic acid compounds was conducted to see the effects they have on electrochemical oxidation. As a result, it was found that lactic acid and formic acid could be used for simultaneous treatment even when they coexisted, whereas acetic acid is refractory to electrochemical oxidation. Furthermore, lactic acid showed the highest electrochemical treatment efficiency, followed by formic acid, and acetic acid.