• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.719-725
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• 2005

Anaerobic fill time and feeding pattern in SBR operation were investigated to find way of minimizing poor nitrogen removal efficiency in BNR process without external carbon addition. The three types of the modified SBR operations that were CO-SBR, IA-SBR, and SF-SBR were tested by lab-scale and pilot-scale SBR processes($2\;m^3/day$). In addition, practical equation for biological nitrogen removal was suggested and the equation considered the effect of ratio of fill volume over whole SBR volume and the ratio of step-feed in SBR. The denitrification efficiency of the SF-SBR was best among the three SBRs and followed by IA-SBR, and CO-SBR. The efficiency was 95%, 61%, and 19%, respectively. Looking at the change of sludge floc density by the length of anaerobic fill time, the density of sludge floc at 1 hour and 2 hours of anaerobic fill time were greater than 3 hours of one. The floc size distributions were $100{\sim}300\;{\mu}m$ and $200{\sim}400\;{\mu}m$ with respect to anaerobic fill time 2 hours and 3 hours, respectively.

• Journal of Korean Society of Water and Wastewater
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• v.11 no.1
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• pp.33-41
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• 1997

An attempt was made to enhance anaerobic treatment efficiency by adopting the anaerobic sequencing batch reactor(ASBR) process at a thermophilic temperature. Operational characteristics of the ASBR process were studied using laboratory scale reactors and concentrated organic wastewater composed of soluble starch and essential nutrients. Effects of fill to react ratio (F/R) were examined in the Phase I experiment, where the equivalent hydraulic retention time(HRT) was maintained at 5 days with the influent COD of 10g/L. A continuous stirred tank reactor(CSTR) was operated in parallel as a reference. Treatment efficiency was higher for the ASBRs because of continuous accumulation of volatile suspended solids(VSS) compared to the CSTR. However, the rate of gas production and organic removal per unit VSS in the ASBRs was much lower than the CSTR. This was caused by reduced methane fermentation due to accumulation of volatile acids(VA), especially for the case of low F/R, during the fill period. When the F/R was high, maximum VA was low and the VA decreased in short period. Consequently, more stable operation was possible with higher F/R. Effects of hydraulic loading rate on the efficiency was studied in the Phase II experiment, where the organic loading rate was elevated to 3333mg/L-d with the F/R of 0.12. Reduction of organic removal along with rapid increase of VA was observed and the stability of reaction was seriously impaired, when the influent COD was doubled. However, operation of the ASBR was quite stable, when the hydraulic loading rate was doubled and a cycle time was adjusted to 12 hour. It is essential to avoid rapid accumulation of VA during the fill period in order to maintain operational stability of the ASBR.

• Journal of Korean Society on Water Environment
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• v.28 no.6
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• pp.917-922
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• 2012

In order to improve applicability of a microbial fuel cell the laboratory-scaled study has been performed by adopting an air-cathode MFC system with high concentrated anaerobic slugies in this study. The concentrations of microbes are grouped into three types, Type A (TS 1.7%), Type B (TS 1.1%) and Type C (TS 0.51%). The open circuit voltage $(V_{oc})$ characteristics showed that the medium microbes concentration of 1.10% (Type B) kept a constant voltage of 1.0 V for 150 hours, which showed the longest time among three types (Type A and Type C). The discharge charge curves for a closed circuit with $500 \Omega$ also showed that Type B generated a stable discharge voltage of 0.8 V for a longer time as in the open circuit voltage case. This could be explained by the relatively large amount of the attached microbes. Under the $V_{oc}$condition the COD removal efficiency of Type B was found to be low for a long time, but those of Type A and C were found to be high for a short period of time. Therefore, the suspended microbes could decrease the coulombic efficiency. It was concluded that the high $V_{oc}$ was caused by low COD and the $V_{oc}$ became low after the COD removal. The COD reduction resulted in an unstable and low working voltage. From the polarization characteristics Type A was found to show the highest power density of $193\;mW/m^2$ with a fill factor of 0.127 due to the relatively high remaining COD even after the MFC reaction.