Since 2021, national standards of South Korea for industrial wastewater discharge to surface water have changed from chemical oxygen demand to total organic carbon for the organic matter. Conventional organic matter parameters (e.g., biochemical oxygen demand, chemical oxygen demand and total organic carbon) are limited means of understanding the behavior of dissolved organic matter in industrial wastewater treatment processes. Thus, the current study used advanced dissolved organic matter characterization tools (e.g., fluorescence excitation emission matrix and size exclusion chromatography-organic carbon detection) to scrutinize industrial wastewater characteristics from three full-scale industrial wastewater treatment plants (IWTPs). The tools were conducive to tracking industrial wastewater sources of total organic carbon, influencing the overall performance of IWTPs, and proposing alternative processes to lower total organic carbon concentration in the effluent. The results of this study suggest that the diagnosis of IWTPs based on dissolved organic matter characteristics could be a useful tool for providing more insight into total organic carbon management.

@en

From 2022, industrial wastewater discharge regulations in South Korea will replace chemical oxygen demand (COD_Mn) with total organic carbon (TOC). A shift from COD_Mn to TOC is a pioneering change in protecting water bodies from organic contaminants. However, several industries are struggling to meet these TOC requirements even though their effluents met the COD_Mn limits. Effluent COD_Mn/TOC ratios (1.28 ± 0.64) found in our study were lower than the COD_Mn/TOC coefficients (1.33–1.80) suggested by the Ministry of Environment in South Korea. Aliphatic and particulate organic matter contents in effluents likely influenced the COD_Mn/TOC ratio. Regardless of the industrial category, dissolved organic carbon often consists of low molecular weight neutrals, hydrophobic organic carbon, and protein-like substances in raw and treated industrial wastewaters. The present study also revealed that TOC and COD_Mn represented different organic matter fractions in the paper mill and oil refinery wastewater, whereas the industrial park wastewater showed similar dissolved organic matter characteristics. Specifically, COD_Mn was effective in the determination of humic content in paper mill wastewater but was underestimated in oil refinery wastewater. Additionally, only paper mill effluents exceeded the TOC requirements (4 of 6 samples) and required an additional post-treatment process owing to higher organic loads.

@en

Natural organic matter (NOM) occurs throughout the hydrologic cycle, varying in both amount and character. In this paper, a description of NOM in surface and drinking water, in groundwater and in seawater is presented. Water samples representing these environments were collected and characterized using multiple NOM characterization techniques, including fluorescence excitation emission matrices (F-EEM) and size exclusion liquid chromatography with organic carbon detection (LC-OCD). The results show that the raw surface water as well as the treated water comprises mainly (>70%) of humic substances. The biopolymers, which are more readily biodegradable, contribute up to 2% of the NOM in the raw water but this is completely removed after treatment. For sea water samples, humic substances represent about 50% of the dissolved organic carbon concentration (DOC), while the fraction with size bigger than 20 kDa (biopolymers) represents about 7%. During soil passage, there was preferential removal of non-humic substances (i.e., biopolymers) from wastewater effluent-impacted surface water while the specific ultraviolet absorbance (SUVA), which reflects the aromatic characteristics of organics in a sample, showed an increasing trend along the depth of the soil column. This is a consequence of the removal of non-humic substances (biopolymers) which results in an increase in aromaticity.@en