• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.669-678
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• 1994

The BOD removal characteristics of submerged biofilters filled with three kinds of filter media respectively were experimentally examined with constant temperature, pH value and variable BOD loading and recirculation ratio. Obtained results are as follows; 1. The BOD removal ratio decreases with the increasing $BOD_5$ volumetric loading rate, and the loading rate for the BOD removal over 90% is lower thean $1.6kg{\cdot}BOD_5/m^3{\cdot}d$ for the plastic media of Netring and cubic wire meshes. This is a much large value than $0.3{\sim}0.8kg{\cdot}BOD_5/m^3{\cdot}d$ for conventional activated sludge process. The required submerged biofilter volume is found to be much samller than that of conventional activated sludge process. 2. The decreasing order of BOD removal is Netring (random plastic media), cubic wire meshes (plastic module), and then gravel (stone media). This is mainly due to the media characteristics such as void ratio, specific surface area and media shapes. 3. The $BOD_5$ removal rate increases with the recircuration ration, but the rate of increases becomes samaller as the recirculation ratio increases over 20. When $BOD_5$ loading is $1.8kg{\cdot}BOD_5/m^3{\cdot}d$, the required recirculation rationto obtain 90% $BOD_5$ removal is about 20 for Netring and it was about 30 for cubic wire meshes. 4. Reynold's Number increases with recirculation ratio, and the Reynold's Numbers corresponding to the recircuration ratio of 10~50 are less than 52, showing laminar up flows in the filter. The settled and effluent sludges increase with increase of Reynol's Number, and there are the definite Reynold's Numbers at which the settling sludge concentrations become nearly constant respectively in each filters. 5. In this submerged biofilter system, small volume of sludge hopper can be substituted for a separated settling tank.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.629-637
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• 2000

A two-phase anaerobic reactor with a submerged microfiltration system was tested for its ability to produce methane energy from organic wastewater. A membrane separation system with periodic backwashing with compressed air was submerged in the acidogenic reactor. The cartridge type of microfiltration (MF) membrane with pore size of $0.5{\mu}m$ (mixed esters of cellulose) was tested. An AUBF (Anaerobic Upflow Sludge Bed Filter: 1/2 packed with plastic media) was used for the methanogenic reactor. Soluble starch was used as a substrate. The COD removal was investigated for various organic loading with synthetic wastewater of 5,000 mg starch/L. When the hydraulic retention time (HRT) of the acidogenic reactor was changed from 10 to 4.5 days, the organic loading rate (OLR) varied from 0.5 to $1.0kg\;COD/m^3-day$. When the HRT of the methanogenic reactor was changed from 2.8 to 0.5 days, the OLR varied from 0.8 to $5.8kg\;COD/m^3-day$. The acid conversion rate of the acidogenic reactor was over 80% in the 4~5 days of HRT. The overall COD removal efficiency of the methanogenic reactor showed over 95% (effluent COD was below 300 mg/L) under the highly fluctuating organic loading condition. A two-phase anaerobic reactor showed an excellent acid conversion rate from organic wastewater due to the higher biomass concentration than the conventional system. A methanogenic reactor combined with sludge bed and filter, showed an efficient COD and SS removal.

• Journal of The Korean Society of Grassland and Forage Science
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• v.17 no.2
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• pp.187-198
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• 1997

This experiment was conducted to evaluate effects of wilting and additives on fermetation characteristics, quality and aerobic stability of silage of rye(Seca1e cereale L.) harvested at the early heading stage. Harvested rye was wilted or mixed with beet pulp and then treated with formic acid or lactic acid bacteria(LAB) inoculant. Treatments were consisted of direct cut(DC), wilted(WT), beet pulp added(BP), direct cut and formate applied(DF), wilted and formate applied(WF), beet pulp and formate applied(BF), direct cut and LAB inoculated(DL), beet pulp added and LAB inoculated(BL), and wilted and LAB inoculated(WL) silages. Afler 70 days of ensiling period, the silages were opened and exposed to air for 7 days, and the silages of opening day(0 day) were compared with the silages exposed to air for 7 days(7 day). 1. LAB inoculated rye silages(DL, WL, BL) lowered pH values effectively eom the third day of ensiling and showed most stable pattern of pH changes during the initial fermentation process. Direct cut and formate applied(DF), beet pulp and formate applied(BF) and beet pulp added(BP) silages were also effective in lowering pH from the seventh day thai direct cut treatment(DC). 2. pH was low below 3.7 in all treatments of 0 day. After 7-day period of aerobic exposure, DL and WL showed considerable increases in pH from 3.5 and 3.4 to 8.3 and 6.4, respectively. 3. Direct cut rye silages(DF, DC, DL) and beet pulp and formate treatment(BF) produced effluent of 121.2, 85.9, 80.3 and 34.2 mlkg, respectively and these were greater than others(P<0.01). Beet pulp retained 1.61 I/kg of effluent at the application rate of 50 kg/t in comparing BP with DC, and formate application increased the amount of effluent in comparing DF and BF with DC and BP, respectively(P<0.01). 4. Beet pulp and LAB treatment(B1) was highest in content of lactate as 3.1% and formate treated silages(DF, WF, BF) showed lower content of lactate and total acid than others. LAB inoculated(D1, WL, BL) and wilted (WT) silages were graded to be good quality as a second group by the Flieg's score. Formate applied silages (DF, WF, BF) were graded as a foum group lower than DC by one. 5. Residual content of WSC of rye silage was higher in BP, BF, DL and BL than direct cut treatment(M3) (P< 0.01). Formate application had a tendency to increase the content of residual content of WSC. 6. For the ratio of NH3-N to Total N, wilted and LAB inoculated(W1) and direct cut and LAB inoculated(D1) silages were lowest on 0 day as 8.9 and 9.3% respectively. But after 7-day period of aerobic exposure, WL and DL showed largest increase of the ratio of $NH_3-N$ to Total N from 0 day(P<0.01). 7. On 0 day wilted(WT), beet pulp and formate treatment(BF), and beet pulp and LAB treatment(B1) were lower than direct cut treatment(DC) for NDF and ADF concentrations consistently. Formate applied silages (DF, WF, BF) made little change in ADF and NDF concentrations during 7 day period of aerobic exposure. DL and WL showed a large increase in ADF and NDF concentrations under aerobic condition(P<0.01). 8. IVDMD values of wilted(WT), beet pulp added(BP), wilted and LAB inoculated(W1) and beet pulp added and LAB inoculated(B1) silages were higher than direct-cut treatmentPC) as 84.7, 84.7, 84.4 and 83.0%, respectively on 0 day. But during 7-day period of aerobic exposure, a great decreae in IVDMD of WL was showed(P<0.01). The experimental results indicate that wilted silage(WT) could be recommended as the most effective treatment for reducing efluent and increasing quality and feed value of rye silage without deteriorating aerobic stability more than direct cut treatment(DC). Additionally, under unfavorable weather condition beet pulp added and LAB inoculated treatment(T3L) might be the possible alternative for successful ensiling of forage rye.

• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.3
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• pp.75-86
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• 2003

In the near future, the capacity of conventional anaerobic digester is thought to be insufficient because of the increase of the total solids from expansion of intercepting sewer, sewage quantity and direct input of night soil from near apartment districts. The objectives of this study was to investigate the improvement of digestion efficiency using microbial agent(Bio-dh). The system was a pilot-scale, two-staged, anaerobic sludge digestion system. The first-stage digester was heated and mixed. The agitation velocity of the first-stage digester was 120rpm. The second-stage digester was neither heated nor mixed. The Digestion temperature was kept at $35{\pm}1^{\circ}C$ The detention time of digester was 19 days. The dosage of sewage sludge and microbial agent were $0.65m^3/day$ and $0.5{\ell}/day$, respectively. The experiments was run for 25days. Three times a week, $COD_{Mn}$ and SS of effluent, TS, VS, and biogas production rate were measured. Temperature, pH, and alkalinity were measured daily. The results were as follows ; Without microbial agent, digestion efficiencies ranged 46.0%~50.9%(mean=48.6%), with microbial agent(Bio-dh), digestion efficiencies ranged 52.8%~57.3%(mean=54.2%). Consequently, microbial agent(Bio-dh) increased the sludge digestion efficiency about 12%. Also, Without microbial agent, the mean concentration of $COD_{Mn}$ and SS of second-stage digester effluent were 1,639mg/L, 4,888mg/L respectively. With microbial agent, the mean concentration of $COD_{Mn}$ and SS of second-stage digester effluent were 859mg/L, 2,405mg/L respectively. Consequently, microbial agent(Bio-dh) increased the removal efficiency of $COD_{Mn}$ and SS about 47.6% and 50.8%, respectively.

• Resources Recycling
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• v.31 no.4
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• pp.56-65
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• 2022

Copper is one of the non-ferrous metals used in the electrical/electronic manufacturing industries due to its superior properties particularly the high conductivity and less resistivity. The effluent generated from the surface finishing process of these industries contains higher copper content which gets discharged in to water bodies directly or indirectly. This causes severe environmental pollution and also results in loss of an important valuable metal. To overcome this issue, continuous R & D activities are going on across the globe in adsorption area with the purpose of finding an efficient, low cost and ecofriendly adsorbent. In view of the above, present investigation was made to compare the performance of a plant root (Datura root powder) as a bio-adsorbent to that of the synthetic one (Tulsion T-42) for copper adsorption from such effluent. Experiments were carried out in batch studies to optimize parameters such as adsorbent dose, contact time, pH, feed concentration, etc. Results of the batch experiments indicate that 0.2 g of Datura root powder and 0.1 g of Tulsion T-42 showed 95% copper adsorption from an initial feed/solution of 100 ppm Cu at pH 4 in contact time of 15 and 30 min, respectively. Adsorption data for both the adsorbents were fitted well to the Freundlich isotherm. Experimental results were also validated with the kinetic model, which showed that the adsorption of copper followed pseudo-second order rate expression for the both adsorbents. Overall result demonstrates that the bio-adsorbent tested has a potential applicability for metal recovery from the waste solutions/effluents of metal finishing units. In view of the requirements of commercial viability and minimal environmental damage there from, Datura root powder being an effective material for metal uptake, may prove to be a feasible adsorbent for copper recovery after the necessary scale-up studies.

• KSBB Journal
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• v.23 no.4
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• pp.317-322
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• 2008

The Biochemical Oxygen Demand(BOD) is one of important parameters for the most widely used method of organic pollution in wastewater and wastewater treatment effluent. As the conventional BOD test needs 5-day long incubation period, it is thus incompatible with real time control of wastewater treatment plant. To resolve this problem, in the present study an on-line Dissolved Oxygen(DO) monitoring system was used to observe the transient change of dissolved oxygen concentration in livestock wastewater. The system was composed of BOD sensor, amplifier and computer. It was observed that the concentration of the microorganism in the livestock wastewater was relatively constant during the growth period of initial one hour, which allowed the assumption of the constant Oxygen Uptake Rate(OUR) within one hour of measurement. It was thus concluded that the present scheme provided a protocol for automatic measurement of BOD in livestock wastewater, which can be applicable to optimal control of livestock wastewater treatment plant.

• Korean Journal of Environmental Agriculture
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• v.21 no.4
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• pp.274-278
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• 2002

Nitrate removal rate in three wetland cells was examined. The acreage of each cell was 150 $m^2$. They were a part of a stream water treatment demonstration system which was composed of two ponds and six wetland cells. Earth works far the pond-wetland system were finished from April 2000 to May 2000 and reeds were planted in the three cells in May 2001. Waters of Sinyang Stream flowing into Kohung Esturiane Lake located southern coastal area of Korean Peninsula were pumped into a primary pont Effluents from a secondary pond were funneled into the three cells. Volumes and water quality of inflow and outflow were analyzed from July 2001 through December 2001. Inflow and outflow averaged 20 $m^3/d$ and 19.3 $m^3/d$, respectively. Hydraulic retention time was 1.5 days. Average influent and effluent nitrate concentration was 2.30 mg/L, 1.75 mg/L, respectively. Nitrate removal rate in the three cells averaged 80.9 $mg/m^2/day$. Seasonal changes of nitrate retention rates were closely related to those of wetland temperatures. Full growth of reeds within a few years can develope litter-soil substrates beneficial to the denitrification of nitrate, which may lead to increases of the nitrate retention rates.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.4
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• pp.37-44
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• 2003

In order to evaluate the contribution of MMSTP operation to the improvement of marine water quality of Mokpo harbour and to estimate the change of pollution loads flowing into Mokpo harbour after the operation of Mokpo Municipal Sewage Treatment Plant (MMSTP), the pollution loads flowing into Mokpo harbour from land in dry weather were surveyed and estimated on the bases of the seasonal flow rates and the seasonal water qualities of streams and effluents located around Mokpo harbour from summer, 1997 to spring, 1998 before the operation of MMSTP, and the pollution loads of the inflow and the effluent of MMSTP were also surveyed and estimated from winter, 1998 to spring, 1999 after the operation of MMSTP. The treatment rates of MMSTP were shown to be about 49% in COD, 76% in TSS, 79% in VSS, 3% in T-N, 7% in DIP, 29% In T-P and -32% in DIN. The change rates of pollution loads flowing into the inner harbour of Mokpo due to the operation of MMSTP were shown to be about 56% in COD, 78% in TSS, 84% in VSS, 45% in DIN, 22% in T-N, 34% in T-P and -14% in DIP The contribution rates of MMSTP operation to the reduction of total pollution loads flowing into the entire Mokpo harbour were found to be about 3% in COD, 3% in TSS, 5% in VSS, 1% in DIP, 3% in T-P and -1% in DIN.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.1
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• pp.1-6
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• 2006

Biological nutrient removal(BNR) process used in this study, which was packed with EPS(expanded polystylene) media, has more many advantages in aspect of reducing hydraulic retention time(HRT) of the process and having less effect of temperature in the winter season than commercial process in the present. Bench-scale study was performed using domestic wastewater. In the results, it was observed that the T-N removal efficiencies in HRT 6 hr and HRT 4 hr were 55% and 51%, respectively, showing the small reduction (about 4%) of T-N removal efficiency according to shortening of HRT. In comparison of T-N removal characteristic in summer and winter seasons, it showed that T-N removal efficiencies in summer and winter seasons were 65% and 54%, respectively, showing the 11% lower T-N removal efficiency in winter season than in summer season due to deterioration of nitrification in winter season. In the studies of influent loading rate and C/N ratio, the process showed stable effluent quality under the condition of broad influent loading rate and C/N ratio. Therefore, it is anticipated that the developed process in this study could be applicable to small wastewater treatment plant in nutrient removal.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.6
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• pp.563-580
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• 2010

In 2009 the Korea Ministry of Environment announced 'A Comprehensive Plan for the Improvement of Sewer Service in Rural Area' aiming at reduction of the sewer service gap between urban and rural areas as well as improvement in the residential environment of the rural area. According to the plan, the sewer system supply rate for the rural area is expected to reach up to 75% until 2015 with the budget of 4.7 trillion won (Korean currency). It is not certain, however, that the increase in the sewer system supply rate will accompany improvement of water quality in receiving water because several veiled problems that can occur in small-scale sewer treatment plants are poorly addressed in the plan. In this study, those issues for the small-scale sewer treatment plants and their solutions were discussed based on a case study in which we investigated 19 treatment facilities at two rural regions in Gyeonggi province. This study also included strategies useful for the plan. From the results of investigation, some problems, e.g., high hourly variations but low in flowrates and low mass loading were commonly identified. Although operation parameters in sewer treatment plants require to be modified depending on the mass loading, most of the plants were operated with the initial design parameters which causes the decrease of removal efficiency. In the intensive diagnosis, we arranged and applied solutions (e.g., flow equalization, air on/off time control, etc) to the two selected plants and found out improvement of effluent water quality, especially organic matters (COD and SS) and T-N with better denitrification performance.