Byung-Uk Bae

Improved brine recycling during nitrate removal using ion exchange

Ion exchange technology is currently the best for removing nitrate from drinking water. However, problems related to the disposal of spent brine from regeneration of exhausted resins must be overcome so that ion exchange can be applied more widely and economically, especially in small communities. For this purpose, a novel spent brine recycling system using combined biological denitrification and sulfate reduction processes was developed for more efficient reuse of brine. A granular activated carbon (GAC) adsorption column was introduced as an additional step to prevent contamination of resins by bio-polymers and dissolved organics present in the bio-reactor effluent. Two upflow sludge blanket reactors (USBRs) were operated in series for 166 days to provide denitrification and sulfate reduction. The denitrification reactor provided a nitrate removal efficiency of 96% at a nitrate-N loading rate of 5.4 g NO3(-)-N/l d. The sulfate reduction efficiency of the sulfate reduction reactor remained approximately 62% at a sulfate loading rate of 1.8 g SO4(2-)/l d. Five ion exchange columns containing A520E resins were repeatedly operated in up to 25 cycles of service and regeneration using five kinds of brine: one virgin 3% NaCl and four differently recycled spent brines. Throughput decreased remarkably when the biologically recycled brine was not treated with the GAC column, probably due to the presence of bio-polymers and dissolved organic compounds. The sulfate reduction reactor placed after the denitrification step increased the bicarbonate concentration, which could be used as a co-regenerant with chloride. The inclusion of the sulfate reduction reactor into the conventional brine recycling system allowed more efficient reuse of brine, resulting in both reduced salt consumption and brine discharge.

Influence of applied voltage on the performance of bioelectrochemical anaerobic digestion of sewage sludge and planktonic microbial communities at ambient temperature.

The influence of applied voltage on the bioelectrochemical anaerobic digestion of sewage sludge was studied at ambient temperature (25±2°C). The stability of the bioelectrochemical anaerobic digestion was considerably good in terms of pH, alkalinity and VFAs at 0.3V and 0.5V, but VFA accumulation occurred at 0.7V. The specific methane production rate (370mLCH4/L.d) was the highest at 0.3V, but the methane content (80.6%) in biogas and the methane yield (350mLCH4/gCODr) were higher at 0.5V, significantly better than those of 0.7V. The VS removal efficiency was 64-66% at 0.3V and 0.5V, but only 31% at 0.7V. The dominant species of planktonic microbial communities was Cloacamonas at 0.3V and 0.5V, but the percentage of hydrolytic bacteria species such as Saprospiraceae, Fimbriimonas, and Ottowia pentelensis was much higher at 0.7V. The optimal applied voltage for bioelectrochemical anaerobic digestion was 0.3-0.5V according to digestion performance and planktonic microbial communities.

Re-activation characteristics of preserved anaerobic granular sludges

Abstract Re-activation characteristics of anaerobic granular sludges starved for 10 months were studied. Specific biomass activities were monitored and both scanning and transmission electron microscopies were used to investigate the microbial and the morphological changes in granular sludges during storage. In order to investigate the re-activating capability of granular sludges starved for 10 months, the recovery of microbial activity was observed in a reactor re-feeding test as well as in a serum bottle test (SBT). Specific biomass activity tests indicated that the room temperature was preferred to the refrigerated conditions in maintaining the methanogenic activity. The specific biomass activity after 10 months of storage decreased by more than 30% of the initial. The re-activating test showed that granular sludge was quickly re-activated by re-feeding the substrate. With 10 months old granular sludge a 11·2 kg COD/m3.day loading rate was achieved within 12 days after the onset of refeeding. The overall performance of the reactor with granular sludges stored at room temperature was more stable than that at 4°C.

Preservation characteristics of anaerobic granular sludge

SummaryThe preservation characteristics of granular sludges were investigated in terms of storing age and environmental condition. As a preservative index, physicochemical, microbiological, and morphological parameters were measured in order to quantify the change in granular sludge. Results from this research indicated that, as the anaerobic granular sludge had an outstanding preservation characteristic, UASB system could be effectively applied to the industries operating seasonally or intermittently.

Effect of Pre-ozonation on the Trans-membrane Pressure of Ceramic Membrane

Abstract : The performance of a domestic ceramic membrane with pore size of 0.1 µm was evaluated to produce drinking water. A pilot-scale ceramic membrane filtration plant with a capacity of 1 m 3 /d was operated at the filtration flux of 3.0 m 3 /m 2 ․d to investigate the effect of both backwash interval and pre-ozonation on TMP (trans-membrane pressure) increasing rate. The TMP increased with increasing the backwash interval. However, the application of pre-ozonation reduced the TMP increasing rate remarkably. When 1 mg/L of ozone was dosed with contact time of 5 min, TMP increasing rate at the backwash interval of 1 hr was reduced by 30%. This result indicated that pre-ozonation was very effective in reducing membrane fouling. There was almost no change in TMP increasing rate when the ozone contact time was maintained in the range of 5 to 15 min. Increasing ozone concentration up to 3 mg/L showed beneficial effect on TMP increasing rate. Key Words : Drinking Water, Ceramic Membrane, Trans Membrane Pressure (TMP), Pre-ozonation, Ozone Dose and Contact Time

Performance of an inner tube-type gas-solid separator device in a UASB reactor

Abstract In this study, a 3.3 m pilot-scale UASB reactor was operated to investigate the performance of an inner tube (IT)-type gas-solid separator (GSS) device, as well as the effects of the superficial gas velocity on the hydrodynamic characteristics of an upflow bioreactor. The sludge hold-up efficiency of the IT-type GSS device increased gradually as the superficial gas production rate increased. When the superficial gas velocity was 0.26 m/h, the UASB reactor excluding the settling compartment was described as a non-ideal plug flow with a dead space of about 20%. However, when the superficial gas velocity increased to 0.67 m/h, the overall flow pattern was close to a completely stirred tank reactor (CSTR), without significant difference in flow pattern in the settler.

A Pilot Scale Biostimulation Study for In-situ Remediation of Organic Pollutants and PAHs contained in Coastal Sediment

연안오염퇴적물에 함유된 유기물질과 PAHs의 현장정화를 위한 생물활성촉진제의 효능을 파일럿 규모의 현장실험을 통하여 1년간평가하였다. 실험 해역의 수온은 계절적인 요인으로 인해 16.5℃에서 21℃까지 변화가 있었으나, 파일럿 반응조의 오염퇴적물의 pH는 8.4-8.5로서 비교적 일정하였다. 파일럿 실험종료 후 바탕시험구와 초산, 황산이온, 질산이온을...

Direct measurement of cake fouling potentials by powdered activated carbon during microfiltration of surface water

AbstractPowdered activated carbon (PAC) addition is one of the promising options to improve the natural organic matter removal efficiency in microfiltration system. However, there have been controversial research results with impacts of PAC addition on membrane fouling. Direct observation technique through membranes was applied in this study to quantitatively analyze membrane fouling by PAC. Particle deposition rates and fouling potential were measured at various PAC concentrations. Membrane filtration tests revealed that the formation of PAC cake layers on the membrane surfaces could increase membrane permeate flux due to the increased porosity of the cake layers. Increased concentrations of PAC in feed water could increase the thickness of cake layers, yet no significant decline of permeate flux was observed. The proposed direct observation technique, which showed good agreement with filtration resistance measurement, could be applied for the monitoring of activated carbon deposition on membrane surface...