Groundbreaking papers in Water Research 1967-2006. A dynamic model of the clarification-thickening process.
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History, 20th Century↗
Biomedical subjects
Hang-Sik Shin
Publications and source records attributed to Hang-Sik Shin.
Conversion of food waste into hydrogen by thermophilic acidogenesis.
Conversion of food waste into hydrogen by thermophilic acidogenesis was investigated as a function of organic loading rate (OLR), hydraulic retention time (HRT) and pH in a continuous stirred tank reactor. In order to identify hydrogen-producing microorganisms, denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR)--amplified V3 region of 16S rDNA analysis was conducted at each tested pH. The conversion of food waste into hydrogen was strongly influenced by the operational conditions. The hydrogen production was increased as OLR increased up to 8 gVSl(-1) d(-1), but drastically decreased at 10 gVSl(-1) d(-1). The yield of hydrogen was decreased from 2.2 to 1.0 mol-H2/mol-hexose consumed as HRT decreased from 5 to 2 days. More carbohydrates in the food waste were decomposed at longer HRT, 76-90%, at HRT of 2-5 days. The hydrogen production peaked at pH 5.5+/-0.1 and significantly decreased at pH 5.0+/-0.1. The biogas produced was composed of hydrogen and carbon dioxide, but no methane was detected at all tested conditions. The hydrogen contents in the gas produced were more than 55% (v/v) and not sensitive to all tested conditions. The optimum operational condition for continuous hydrogen production from the food waste was obtained at 8 gVSl(-1)d(-1), 5 days HRT and pH 5.5+/-0.1 where the hydrogen production rate, content, yield and the efficiency of carbohydrate decomposition were 1.01 H2/l-d, 60.5% (v/v), 2.2 mol-H2/mol-hexose consumed and 90%, respectively. The hydrogen production was related with the concentration of total organic acids (TOA) which was strongly dependent on that of butyrate indicating that the reaction was mainly butyrate fermentation. The hydrogen-producing microorganism of Thermoanaerobacterium thermosaccharolyticum that involved in acetate/butyrate fermentation, was detected with strong intensity at all tested pHs by denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR)--amplified V3 region of 16S rDNA analysis and sensitive to the tested pHs. The experimental results indicated that effective hydrogen production from the food waste could be obtained continuously by thermophilic acidogenesis at proper operational condition.
Acids↗
A laboratory and pilot study of thermally enhanced soil vapor extraction method for the removal of semi-volatile organic contaminants.
Laboratory and field pilot study was conducted to evaluate the effectiveness of thermally enhanced soil vapor extraction (SVE) system for the removal of semi-volatile organic contaminants (SVOCs) from soils. Several parametric studies were conducted to evaluate the effect of temperature and air flow rate on the removal of SVOCs. Column studies near ambient temperature show very little efficiency for SVOCs removal. The removal rates of SVOCs are highly dependent on temperature. Moving fronts in the effluent concentrations of contaminants are observed, according to the order of volatility of contaminant. This result is attributed to continuous changes in the liquid composition toward less volatile fractions, thus increasing the mole fraction of the less volatile fractions remaining in the liquid mixture. It is also found that increased air flow rate results in high removal rate of contaminants. However, too high air flow rate brings about the mass transfer limitation on the volatilization of the contaminants. Results from steady-state column studies show that mass transfer limitation is reduced at high temperature, possibly due to the increase in the diffusivity of contaminant in the liquid and gas phase. A field pilot study of a hot air injection method for the remediation of diesel-contaminated soil has shown advantages over the conventional SVE. Within 30 days of test operation, TPH concentrations at unsaturated soils were dramatically reduced, corresponding to more than 95% removal. However, temperature profiles and the removal rates of SVOCs near groundwater level indicate that moisture content would be a limiting factor in the real application of hot air injection.
Air Movements↗
Comparative performance between temperature-phased and conventional mesophilic two-phased processes in terms of anaerobically produced bioenergy from food waste.
Comparative evaluation of bioenergy production from food waste was carried out with both a temperature-phased and a conventional mesophilic two-phased process at different organic loading rates (OLRs). No methane was detected in the temperature-phased thermophilic-acidogenic fermenter at all the OLRs tested. However, a significant amount of methane content was detected in the conventional two-phased mesophilic-acidogenic fermenter, with increments depending on the organic loading rate [from 17% at 3 g VS L(-1) day(-1) to 25% at 8 g VS L(-1) day(-1) (VS, volatile solid)]. Acetate and butyrate were the main volatile fatty acids (VFAs) in the temperature-phased thermophilic-acidogenic fermenter; conversely propionate was a major VFA in the conventional two-phased mesophilic-acidogenic fermenter. Through the chemical oxygen demand (COD) balance of both temperature-phased and conventional mesophilic two-phased processes, the fraction of the feed-COD converted to the hydrogen-COD in the thermophilic-acidogenic fermenter within the former process was estimated from 7.9 to 9.3%, with a peak at ORL of 6 g VS L(-1) day(-1), whereas it was quantified from 0.3 to 0.9% in the mesophilic-acidogenic fermenter within the latter one. Moreover, the fraction of the feed-COD converted to the methane-COD in the mesophilic-acidogenic fermenter within the conventional two-phased process ranged from 5.4 to 7.9%. On the other hand, conversion of the feed-COD to the methane-COD in the mesophilic-methanogenic fermenter of both temperature-phased and conventional mesophilic two-phased processes ranged from 66.2 to 72.3% and from 63.5 to 70.5%, respectively, with decrements related to the increase of organic loading rate.
Bioelectric Energy Sources↗
Analysis and application of ADM1 for anaerobic methane production.
An anaerobic model for the serum bottle test was developed and analyzed with sensitivities of stoichiometric and kinetic parameters to the components in order to establish a basis for appropriate application of the model. Anaerobic glucose degradation in a serum bottle was selected as an example. The anaerobic model was developed based on the anaerobic digestion model no. 1 (ADM1), which had five processes with 17 kinetic and stoichiometric parameters. Sensitivity analysis showed that the yield of product on the substrate (f) has high sensitivities to model components, and that the methane concentration was the most sensitive component. Important parameters including yield of product on the substrate (f), yield of biomass on the substrate (Y), and half-saturation values (K) were estimated using genetic algorithms, which optimized the parameters with experimental results. The Monod maximum specific uptake rate (k) was, however, so strongly associated with the concentration of biomass, that values could not be estimated individually. Simulation with estimated parameters showed good agreement with experimental results in the case of methane production. However, there were some differences in acetate and propionate concentrations.
Algorithms↗
Enhanced ammonia nitrogen removal using consistent biological regeneration and ammonium exchange of zeolite in modified SBR process.
The modified zeo-SBR is recommended for a new nitrogen removal process that has a special function of consistent ammonium exchange and bioregeneration of zeolite-floc. Three sets of sequencing batch reactors, control, zeo-SBR, and modified zeo-SBR were tested to assess nitrogen removal efficiency. The control reactor consisted of anoxic-fill, aeration-mixing, settling, and decanting/idle phases, meaning that nitrogen removal efficiency was dependent on the decanting volume in a cycle. The zeo-SBR reactor was operated in the same way as the control reactor, except for daily addition of powdered zeolite in the SBR reactor. The operating order sequences in the zeo-SBR were changed in the modified zeo-SBR. Anoxic-fill phase was followed by aeration-mixing phase in the zeo-SBR, while aeration-mixing phase was followed by anoxic-fill phase in the modified zeo-SBR to carry NH4(+)-N over to the next operational cycle and to reduce total nitrogen concentration in the effluent. In the modified zeo-SBR, nitrification and biological regeneration occurred during the initial aeration-mixing phase, while denitrification and ammonium adsorption occurred in the following anoxic-fill phase. The changed operational sequence in the modified zeo-SBR to adapt the ammonium adsorption and biological regeneration of the zeolite-floc could enhance nitrogen removal efficiency. As a result of the continuous operation, the nitrogen removal efficiencies of the control and zeo-SBR were in 68.5-70.9%, based on the 33% of decanting volume for a cycle. The zeo-SBR showed a consistent ammonium exchange and bio-regeneration in the anoxic-fill and aeration-mixing phases, respectively. Meanwhile, the effluent total nitrogen of the modified zeo-SBR showed 50-60 mg N/L through ammonium adsorption of the zeolite-floc when the influent ammonium concentration was 315 mg N/L, indicating the T-N removal efficiency was enhanced over 10% in the same HRT and SRT conditions as those of control and zeo-SBR reactors. The ammonium adsorption capacity was found to be 6-7 mg NH4(+)-N/g FSS that is equivalent to 40 mg NH4(+)-N/L of ammonium nitrogen removal.
Adsorption↗
Performance of an innovative two-stage process converting food waste to hydrogen and methane.
This study was conducted to evaluate the performance of an innovative two-stage process, BIOCELL, that was developed to produce hydrogen (H2) and methane (CH4) from food waste on the basis of phase separation, reactor rotation mode, and sequential batch technique. The BIOCELL process consisted of four leaching-bed reactors for H2 recovery and post-treatment and a UASB reactor for CH4 recovery. The leaching-bed reactors were operated in a rotation mode with a 2-day interval between degradation stages. The sequential batch technique was useful to optimize environmental conditions during H2 fermentation. The BIOCELL process demonstrated that, at the high volatile solids (VS) loading rate of 11.9 kg/m3 x day, it could remove 72.5% of VS and convert VS(removed) to H2 (28.2%) and CH4 (69.9%) on a chemical oxygen demand (COD) basis in 8 days. H2 gas production rate was 3.63 m3/m3 x day, while CH4 gas production rate was 1.75 m3/m3 x day. The yield values of H2 and CH4 were 0.31 and 0.21 m3/kg VS(added), respectively. Moreover, the output from the post-treatment could be used as a soil amendment. The BIOCELL process proved to be stable, reliable, and effective in resource recovery as well as waste stabilization.
Bioelectric Energy Sources↗
Kinetics of LCFA inhibition on acetoclastic methanogenesis, propionate degradation and beta-oxidation.
Kinetics of long-chain fatty acids (LCFAs) inhibition on acetoclastic methanogenesis, propionate degradation and beta-oxidation were studied with granular sludge under mesophilic batch conditions. Mathematical expressions used for reaction rates were as shown below: [formula: see text]. The simulated results revealed that the methane production rates from acetate decreased with an increase in both concentration and the number of double bonds of LCFAs. The concentrations of oleate (C18:1), linoleate (C18:2), palmitate (C16:0), and stearate (C18:0) were 0.54 mM, 0.11 mM 1.62 mM, and 2.58 mM, respectively, at which the methane production rates from acetate dropped 10%, and 3.10 mM, 0.72 mM, 5.71 mM, and 5.37 mM, respectively, at which the rates dropped 50%. The inhibitory effects of LCFAs on propionate degradation showed a similar tendency with acetoclastic methanogenesis; however, were less severe. The concentrations of oleate, linoleate, palmitate, and stearate were 1.02 mM, 0.18 mM, 2.34 mM, and 1.92 mM, respectively, at which the propionate degradation rates dropped 10%, and 4.38 mM, 1.17 mM, 5.88 mM, and 5.18 mM, respectively, at which the rates dropped 50%. The observed maximum beta-oxidation rates of oleate, linoleate, palmitate, and stearate were 0.21 mmol (gVSS)(-1) d(-1), 0.09 mmol (gVSS)(-1) d(-1), 0.12 mmol (gVSS)(-1) d(-1), and 0.08 mmol (gVSS)(-1) d(-1), respectively. The lag-phase times in beta-oxidation were also dependent on LCFA concentrations. The concentrations of oleate, linoleate, palmitate, and stearate, at which the lag-phase times became 5 days, were 5.93 mM, 2.24 mM, 4.02 mM, and 2.81 mM, respectively.
Fatty Acids↗
Leaching behavior of lead from ultrasonically treated MSWI fly ash.
This study was conducted to evaluate the effect of ultrasound widely used for extraction of contaminants and for synthesis of complexes, on extraction and stabilization of heavy metals in MSWI fly ash. Ten grams of fly ash was treated at 10 of liquid--solid (L/S) ratio with and without ultrasonic irradiation of 20 kHz. The extractability of Pb from fly ash was enhanced by ultrasound at the acidic condition. At neutral and alkaline conditions, however, ultrasound did not affect the enhancement of extractability. The results of the maximum availability leaching test (MALT) of the residues treated under various pH conditions with or without ultrasound indicated that the stability of Pb in the fly ash residues was enhanced after ultrasonic irradiation irrespective of treated pH conditions. However, there was a critical point on the enhancement of lead stability in the residues even though the extraction efficiency of Pb decreased gradually with increasing ultrasonic intensity during fly ash treatment. Ultrasonic irradiation was effective for phosphate stabilization of Pb in fly ash. Irrespective of leaching tests, less amount of Pb was leached out from the phosphate stabilized residues treated with ultrasound than without ultrasound. The extraction efficiency of Pb from fly ash decreased with increasing treatment time but the fractions available for leaching at MALT increased with increasing treatment time. Conclusively, although the effect of ultrasound on the extraction of Pb from fly ash highly depends on the pH condition of solvent, the stability of lead in the fly ash residues can be enhanced with ultrasonic irradiation.
Carbon↗
Characteristics and fates of soluble microbial products in ceramic membrane bioreactor at various sludge retention times.
The formation and fate of soluble microbial products (SMP) in membrane bioreactor (MBR) was investigated at various sludge retention times (SRT) for 170 days. The SMP concentration was estimated by feeding glucose, which could be completely degraded, and by measuring the dissolved organic carbon (DOC) of the effluent from MBR. Under the conditions of SRT of 20 days, influent DOC of 112 mg/l and HRT of 6 h, the produced SMP was 4.7 mg DOC/l of which 57% was removed or retained by the membrane. DOC of MBR supernatant increased during 100 days and then gradually decreased. Specific UV absorbance showed that the accumulated compounds had a portion of larger, more aromatic, more hydrophobic and double-bond-rich organics, which originated from the decayed biomass. Molecular weight distributions of SMP in MBR supernatant showed that the acclimated microorganisms in a long SRT could decompose high molecular weight organics, it caused the shift of molecular weight distributions of SMP to a lower range. During the operation period, enumeration of active cells in the MBR showed that microbial inhibitions by accumulated SMP was not observed.
Bacteria↗
The role of DPB at anoxic stage in a novel package type BNR process with batch settler.
In this research, package type BNR process was developed to remove nutrients as well as suspended solids from domestic sewage. The effect of HRT reduction of settler on the removal of pollutants as well as the role of DPBs at anoxic reactor were investigated. The proposed package system was composed of sludge denitrification tank, anaerobic, anoxic, oxic, and batch settler. This system could remove nitrogen and phosphorus effectively at low COD/N ratio and also remove SS more effectively than other ordinary BNR system having the conventional settlers. The removal efficiency of total nitrogen (T-N) in optimal condition was about 75.1% under the TCOD/TKN ratio as low as 5.7. The average concentration of the effluent TCOD, ortho-P, NH4+-N, NO3- -N and SS in the package type BNR system of 2 h settler retention time were 15.6. 1.38, 1.4, 10.3 and 3.9 mg/L, respectively. In anoxic state, denitrifying dephosphatation, that is uptaking phosphate by using nitrate-nitrogen as an electron acceptor was observed. The removed NO3- -N concentration by denitrifying dephosphatation was 1.62 mg NO3- -N/mg PO4(3-)-P.
Bacteria, Anaerobic↗
The optimisation of food waste addition as a co-substrate in anaerobic digestion of sewage sludge.
Food waste has been regarded as the main source of various environmental pollution in Korea due to the high volatile solids (VS) and moisture content caused by the features of dietary habits. The feasibility of food waste as a co-substrate in anaerobic digestion of sewage sludge was investigated in mesophilic and thermophilic conditions using batch tests. Cumulative methane production, dissolved organic carbon (DOC) and volatile fatty acids (VFA) were monitored to find the optimal mixing ratios of food waste and sewage sludge for the enhanced performance of co-digestion. It was observed that adequately mixed food waste led to the enhanced methane production both at mesophilic and thermophilic conditions. However, a conventional linear regression conducted for the optimisation of co-substrate mixing ratios was not accurate in describing exact methane production trends of co-digestion because of the different biodegradability of substrates. Therefore, a remodified Gompertz equation showing nonlinear relationship between variables was developed to find exact information with the same experimental data obtained at 2g VS/l generally used in biochemical methane potential (BMP) tests. Based on an influential parameter, methane production rate (MPR), the optimal mixing ratios of food waste were 39.3% and 50.1% in mesophilic and thermophilic conditions, respectively. To confirm the application of the remodified Gompertz equation, secondary batch tests were conducted with the substrate concentrations of 1-4g VS/l. In overall range tested, the confident mixing ratios of food waste was adjusted to 30-40% and 40% in mesophilic and thermophilic conditions, respectively. The most significant factor for enhanced performance was the improved organic carbon content provided by additional food waste.
Bacteria, Anaerobic↗
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.
Adsorption↗
Enhanced acidogenic fermentation of food waste in a continuous-flow reactor.
This study was performed to improve acidogenic fermentation of food waste in a continuous-flow reactor. The fermentation of food waste is affected by the fermentation constraints such as the biodegradability of substrate, the degrading capability of microorganisms and the environmental conditions. The key factors were, therefore, examined to control the fermentation constraints, such as the effect of seed inoculation and the effect of adjusting dilution rate. Acidogenic fermentation of food waste employing rumen microorganisms resulted in the enhanced efficiency (71.2%) as compared with that (59.8%) employing mesophilic acidogens. In addition, the fermentation efficiency increased from 71.2 to 82.0% by adjusting dilution rate from 3.0 to 1.0 d(-1) depending on the state of the fermentation. The main component of the acidified product was shifted from butyric to acetic acid. This meant that the increase of the fermentation efficiency was mainly caused by the enhanced degradation of vegetables and meats. The control of the fermentation constraints was, therefore, very effective in improving the fermentation efficiency of food waste.
Bacteria↗
Continuous feed, on-site composting of kitchen garbage.
Kitchen garbage generated at a school cafeteria was treated and stabilised in a controlled on-site composting unit for volume reduction and on-site utilisation of processed garbage. The on-site composter was fed with the garbage on a daily basis during the two-months experimental period. Compost was not removed from the unit but was entirely reused as a bulking agent in order to minimise the need for additional bulking agent and compost handling. Performance of the composter tinder this condition was investigated. Most of the easily degradable organic matter (EDM) in the garbage was biodegraded rapidly, and the final product had a low content of EDM. Lipids, total sugar, and hemi-cellulose were degraded 96%, 81%, and 66% respectively. Free air space (FAS) was higher than 0.5 all the time, so accumulation of dry matter in the unit was not significant in reducing reaction efficiency. Other reaction parameters such as pH and MC were kept within a suitable range; however, it was advisable to maintain MC at over 46%. As a result, this method of operation was able to stabilise the garbage with low sawdust demand and little compost production.
Biodegradation, Environmental↗
Behaviors of intercellular materials and nutrients in biological nutrient removal process supplied with domestic wastewater and food waste.
A four-stage biological nutrient removal (BNR) process was operated to investigate the effect of anaerobically fermented leachate of food waste (AFLFW) as an external carbon source on nutrient removal from domestic wastewater having a low carbon-to-nitrogen ratio. The BNR system that was supplemented with AFLFW showed a good performance at a sludge retention time (SRT) of 30 days, despite low temperature. With this wastewater, average removal efficiencies of soluble chemical oxygen demand (COD), total nitrogen (T-N), and total phosphorus (T-P) were 88 to 93%, 70 to 74%, and 63 to 68%, respectively. In this study, several kinds of poly-hydroxyalkanoates (PHAs) were observed in cells. These included 24% poly-3-hydroxybutyrate (PHB), 41% poly-3-hydroxyvalerate (PHV), 18% poly-3-hydroxyhexanoate (PHH), 10% poly-3-hydroxyoctanoate (PHO), 5% poly-3-hydroxydecanoate (PHD). and 2% poly-3-hydroxydodecanoate (PHDD), indicating that microorganisms could store various PHAs through the different metabolic pathways. However, breakdown of the enhanced biological phosphorus removal (EBPR) mechanism was observed when SRT increased from 30 to 50 days for the enhancement of nitrification. To study the effect of SRT on EBPR, a sequencing batch reactor (SBR) system that was supplied with glucose was operated at various SRTs of 5, 10, and 15 days. Nitrification and denitrification efficiencies increased as SRT increased. However, the content of intracellular materials such as PHAs, glycogen. and poly-P in cells decreased. From these results, it was concluded that SRT should be carefully controlled to increase nitrification activity and to maintain biological phosphorus removal activity in the BNR process.
Bacteria↗