• Clean Technology
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• v.28 no.1
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• pp.63-78
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• 2022

Electronics industrial wastewater treatment facilities release organic wastewaters containing high concentrations of organic pollutants and more than 20 toxic non-biodegradable pollutants. One of the major challenges of the fourth industrial revolution era for the electronics industry is how to treat electronics industrial wastewater efficiently. Therefore, it is necessary to develop an electronics industrial wastewater modeling technique that can evaluate the removal efficiency of organic pollutants, such as chemical oxygen demand (COD), total nitrogen (TN), total phosphorous (TP), and tetramethylammonium hydroxide (TMAH), by digital twinning an electronics industrial organic wastewater treatment facility in a cyber physical system (CPS). In this study, an electronics industrial wastewater activated sludge model (e-ASM) was developed based on the theoretical reaction rates for the removal mechanisms of electronics industrial wastewater considering the growth and decay of micro-organisms. The developed e-ASM can model complex biological removal mechanisms, such as the inhibition of nitrification micro-organisms by non-biodegradable organic pollutants including TMAH, as well as the oxidation, nitrification, and denitrification processes. The proposed e-ASM can be implemented as a Water Digital Twin for real electronics industrial wastewater treatment systems and be utilized for process modeling, effluent quality prediction, process selection, and design efficiency across varying influent characteristics on a CPS.

• Korean Journal of Environmental Biology
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• v.40 no.3
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• pp.267-274
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• 2022

Excess nitrogen (N) flowing from livestock manure to water systems poses a serious threat to the natural environment. Thus, livestock wastewater management has recently drawn attention to this related field. This study first attempted to obtain the optimal conditions for the further volatilization of NH₃ gas generated from pig wastewater by adjusting the amount of injected magnesia (MgO). At 0.8 wt.% of MgO (by pig wastewater weight), the volatility rate of NH₃ increased to 75.5% after a day of aeration compared to untreated samples (pig wastewater itself). This phenomenon was attributed to increases in the pH of pig wastewater as MgO dissolved in it, increasing the volatilization efficiency of NH₃. The initial pH of pig wastewater was 8.4, and the pH was 9.2 when MgO was added up to 0.8 wt.%. Second, the residual ammonia nitrogen (NH₄⁺-N) in pig wastewater was removed by precipitation in the form of struvite (NH₄MgPO₄·6H₂O) by adjusting the pH after adding MgO and H₃PO₄. Struvite produced in the pig wastewater was identified by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analysis. White precipitates began to form at pH 6, and the higher the pH, the lower the concentration of NH₄⁺-N in pig wastewater. Of the total 86.1% of NH₄⁺-N removed, 62.4% was achieved at pH 6, which was the highest removal rate. Furthermore, how struvite changes with pH was investigated. Under conditions of pH 11 or higher, the synthesized struvite was completely decomposed. The yield of struvite in the precipitate was determined to be between 68% and 84% through a variety of analyses.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.5
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• pp.837-847
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• 2000

For the treatment of wastewaters generated from beer industry and petrochemical company with high organic and nitrogen contents, laboratory scale of A/O Pure-Oxygen Biofilm (POB) process was developed and studied by means of the comparative economic analysis with extended aeration process. When the wastewater of beer company was initially treated by the A/O POB process in the ranges of 70 to 150 mg TOC/L diluted with tap water, higher than 92% of TOC removal was accomplished in the all ranges. In case of petrochemical wastewater, the initial TOC removal was as low as 52%, though, it increased to 86% after 32 days of operation and also the TKN removal marked 71% after 27 days. Continuous high removal rates were monitored in both the TOC and TKN parameters during the experimental period. Due to the cost for PSA (Pressure Swing Adsorption) setting and biomass supporting media installation, the initial construction cost of A/O POB process was 2.9 times higher than that of extended aeration process. However, the advantages such as low sludge production, no need for sludge recycling and low energy consumption allow the A/O POB process to have 2.5 times lower operation and maintenance costs. Consequently, in the long term of operation, it is likely that A/O POB process would show higher performance as well as cost effectiveness compared to extended aeration process.

• Applied Biological Chemistry
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• v.37 no.4
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• pp.303-309
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• 1994

To develop the treatment process of swine wastewater using Rhodopseudomonas palustris KK14 with high utilizable ability of organic acids, some operating conditions were investigated and optimized in flask-scale and laboratory-scale reactors. The optimal operating conditions in photosynthetic bacteria (PSB) reactor of semi-continuous type were obtained at HRT 6 day, 5% (v/v/day) seeding rate of PSB sludge and 10% (v/v/day) returning rate of PSB return sludge. Under the above operating condition, COD level of the wastewater (initial COD: 10 g/l) was reduced to about 1.7 g/l after 4 days treatment and MLSS was held constant at $4{\sim}5\;g$ per liter. In laboratory-scale process consisted of 5.2 l anaearobic digestion reactor and 15 l PSB reactor, the total removal rates of COD and BOD were increased to 95% and 96% by the continuous operation for 5.36 days, respectively, showing $3kg\;COD/m^3/day$ COD loading rate and 1.1 Kg COD/Kg MLSS/day sludge loading rate in PSB reactor. The offensive odor was considerably removed through the treatment process of swine wastewater.

• Proceedings of KOSOMES biannual meeting
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• 2007.11a
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• pp.97-102
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• 2007

The piggery wastewater is the major source of the water pollution problem in the rural area. The treatment alternatives for piggery wastewater are limited by the characteristics of both high organic and nitrogen(N) content. In order to investigate an efficient N removal system, the thermophilic aerobic digestion process was examined. The experiment was investigated organic and nitrogen removal efficiency at various HRTs and air supply volume. The results of semi-continuous experiment indicated that a higher removal of the soluble portion of COD was achieved with the longer HRTs. However, the inert portion of COD in piggery wastewater was not much changed by thermophilic aerobic digestion. In addition, with the higher HRT of 3 days, up to 79% of NH4-N removal efficiency was achieved. Lower the HRTs, a decrease of NH4-N removal was founds. The gas samples from the lab reactor were analyzed along with the N content in influent and effluent. The N2O formation in our system indicates a novel aerobic deammonification process occurred during the thermophilic aerobic digestion. Both N02 and N03 were not presented in the effluent of thermophilic aerobic digester. With the HRT of 3 days, 36.4% of influent N(or 57.5% removal N) was aerobically converted to N2O gas. The ammonium conversion to N2O gas significantly decrease to 4.5% at low HRT of .05 day..

• Analytical Science and Technology
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• v.16 no.5
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• pp.399-406
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• 2003

This study was conducted to find out the analysis condition of selenium(Se) in oil refinery wastewater with a high concentration of Se using the atomic absorption spectrometry with hydride generation system (HG-AAS). From various experiments that reduced Se(VI) to Se(IV), the optimum pretreatment condition was determined to be a sample volume of 10 mL, HCl 10 mL, with a 30 min heating time in a water bath. In oil refinery wastewater, as the concentration of organics and constitution became higher, the recovery rates of Se decreased. Therefore, three acid digestion methods ($HNO_3/HClO_4$ digestion, $KMnO_4$ digestion, and microwave acid digestion) were tested on the recovery rates of Se in reference to the digestion of organics, petroleum and oxidation from organic Se(org.), Se(IV) to Se(VI). The experiment results showed that the average recovery rate of Se was the highest in microwave acid digestion, although all of the digestions were more than 90%. In consequence, the pretreatment procedure of microwave digestion followed by HCl addition was the most suitable for selenium analysis in oil refinery wastewater by using HG-AAS.

• Applied Chemistry for Engineering
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• v.30 no.4
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• pp.466-471
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• 2019

1,4-dioxane and dichloromethane are classified as carcinogenic groups in the International Agency for Research on Cancer (IARC). They are frequently released at high concentrations in an industrial wastewater effluent. The acute toxicity (24 h) of Daphnia magna for 7.53 mg/L of 1,4-dioxane in the industrial effluent was evaluated as 1.1 TU (toxic unit) and showed TU close to the effluent quality standard. Mixed substances of 1,4-dioxane and dichloromethane in the industrial effluent showed relatively high TU as compared to that of a single substance. Half maximal effective concentration (24 h $EC_{50}$) values of 1,4-dioxane and dichloromethane for the synthetic wastewater prepared in laboratory were 1,744 (0.06 TU) and 170 mg/L (0.6 TU), respectively and the toxicity was low. Nevertheless the toxicological evaluation of the mixture showed that TU values increased to 0.02, 0.04 and 0.10, respectively as 1, 5 and 10 ppm of dichloromethane was added to 100 ppm of 1,4-dioxane. And the synergistic effect was observed between two substances. But the TU value of synthetic wastewater was below 5%, lower than that of industrial effluent at the similar concentration.

• KSBB Journal
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• v.14 no.2
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• pp.136-140
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• 1999

Characteristics of organic acid degradation by isolated yeast strain was investigated. Optimum initial pH was 5. Increase in cell mass was proportional to the decrease in organic acid degradation. Also no accumulation of byproduct was observed during degradation. Acetic acid degraded fast, followed by butyric acid and propionic acid in order. No significant substrate inhibition was observed up to 12 g/L of acetic acid 7 g/L of propionic acid, respectively. However, inhibition of butyric acid was significant above 4 g/L. Cell mass yield was 0.2-0.4 g cell/g acids and decreased at high decreased at high organic acid concentration. 95% of organic acid (7.5 g/L), corresponding to 13,000 ppm, was degraded in 30-40 hours.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.676-679
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• 2003

Long time over 6 month was required to form granuler sludge, which is critically necessary for UASB reactor. By feeding both high molecular cationic polymer and anionic silica sol to conventional digestion sludge, granular sludge was obtained within 5 minutes. Succession adaptation was performed for granular sludge for 30 days. $80{\sim}90%$ COD removal efficiency was shown with granular sludge, which was comparable with that of typical UASB granular sludge.

• Journal of Korean Society of Water and Wastewater
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• v.12 no.2
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• pp.67-75
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• 1998

The purpose of this study is to develop a system for treating industrial wastewater with high carbonaceous and nitrogenous materials. To investigate the potential of using this system, a number of experiments are conducted for about 7 months with the varieties of COD and $NH_3-N$ concentrations, and hydraulic retention time. In the system, 1,500mg/L of COD is remover over 95% in a retention time as low as 9 hours, and the $NH_3-N$ removal efficience is nearly 100% with 90mg/L of $NH_3-N$ in the influent. These results illustrate that the system can effectively be used to treat industrial wastewater containing high concentration of COD and $NH_3-N$.