Minsoo Maeng

Effects of rainfall characteristics on corrosion indices in Korean river basins

AbstractCorrosion indices have been widely used to assess water quality in countries such as the USA, Japan, France, and The Netherlands since Langelier first introduced this concept in 1936. The most commonly used corrosion indices are the Langelier saturation index (LSI), the Ryznar stability index (RSI), and the aggressiveness index (AI). Here, the changes in LSI, RSI, and AI due to corrosion factors such as pH, Ca hardness, and alkalinity were characterized according to the rainfall during the rainy season at four river basins in Korea. The results of a sensitivity analysis of corrosion indices with varying corrosion factors showed that pH had the greatest effect with a value of 0.1, which indicates that pH affects corrosion more than any other corrosion factor. By comparing the monthly pattern of corrosion factors at each river, it was found that pH and alkalinity decreased during the rainy season, whereas Ca hardness showed only subtle changes across the year. In addition, when comparing the relatio...

Development of a hybrid treatment system for combined sewer overflows using a hydrocyclone and a dissolved air flotation system

AbstractCombined sewer overflows (CSOs) contain a mixture of untreated, contaminated sanitary, and storm water. CSOs include both precipitated and suspended matters. In this study, a novel system is proposed to treat CSOs using a combined hydrocyclone and dissolved air flotation (DAF) system for removal of both precipitated and suspended matter. The optimum operating conditions were determined by changing the internal flow rate and the split ratio (Rf) in the hydrocyclone and by changing the angle of the nozzle to determine the floc size, flow rate, and recycle ratio in the DAF system. The types of organic matter contained in prepared synthetic water samples are categorized as soluble CODcr (SCOD) and particulated CODcr (PCOD) in the characterization of the removal rate of the precipitated and suspended matter. The suspended solids (SS) were classified by their specific gravity to determine the removal rate of both precipitated and suspended matter. In a pretreatment process, the system employed a cationi...

Formation characteristics of carbonaceous and nitrogenous disinfection by-products depending on residual organic compounds by CGS and DAF

Allogenic organic matter (AOM) composed of extracellular and intracellular organic matter (EOM and IOM) is a major precursor of halogenated carbonaceous and nitrogenous disinfection by-products (C-DBPs and N-DBPs) upon chlorination. The EOM and IOM extracted from Microcystis aeruginosa were analyzed based on bulk parameters and organic fractions with different molecular weight by liquid chromatography with organic carbon detection (LC-OCD). It investigated the efficiency of a conventional gravity system (CGS) and dissolved air flotation (DAF) in the removal of organic precursors, together with measurement of the formation of four major trihalomethanes (THMs) and haloacetonitriles (HANs) in treated water upon chlorination. The results showed that EOM accounted for 59% of building blocks and humic substances, whereas for IOM, 54% were low molecular weight (LMW) neutrals. Both CGS and DAF showed 57–59% removal of dissolved organic carbon (DOC) from EOM and IOM. Regarding DON removal, DAF was found to be more effective, i.e., 8% higher than CGS for EOM. Moreover, the removal of LMW acids and neutrals (not easy to remove and are major precursors of DBPs) from EOM and IOM by DAF was higher than from CGS. The amounts of DBPs measured in all the samples treated for interchlorination were much lower than in the samples for prechlorination. Although the precursors of EOM had a higher concentration than in IOM, THMs and HANs were detected for IOM at a higher concentration, which might be attributed to higher amounts of aromatic, aliphatic moisture and protein compounds in the IOM. Comparatively, DAF showed lower THM and HAN values than CGS water, particularly for IOM. Also, DAF showed a sharp decrease in THMs and an insignificant increase in HANs according to time.