Eulsaeng Cho

Dye/water separation through supported liquid membrane extraction

The separation of synthetic dye Rhodamine 6G (R6G) and water was investigated using blended organic liquids in a supported liquid membrane (SLM) extraction system. Liquid membrane (LM) components include octyl alcohol (OcOH) as the dye extractant and a polysiloxane liquid as the stabilizing agent. Initial permeation results revealed the suitability of poly (phenyl methyl) siloxane (PPMS) over poly (octyl methyl) siloxane as the blending agent. The most acceptable condition for dye extraction was determined at feed solution pH congruent with 1, wherein highest distribution coefficient, K(D) (OcOH/H(2)O)=18, was attained. Though permeability decreased at optimal blending condition of 1:1 (w/w) OcOH/PPMS, SLM longevity was exhibited with>98% LM retention after 15 h operation in contrast to pure OcOH SLM system (>60% LM loss). Equilibrium experiments reveal that dye extraction followed Langmuir adsorption principle. The dye transport was elucidated using mass transfer analysis wherein it showed a decrease in overall coefficient (k(o)) at increasing feed concentrations. This was a direct consequence of K(D) decline, which becomes more apparent at higher concentrations when SLM saturation point is approached. At varied hydrodynamic conditions, improved k(o) values were observed up to Re(omega)=10,000 when minimal variation in film resistance is attained. Beyond this condition, k(o) becomes independent from stirring rate effect nonetheless SLM stability is compromised due to shear-induced LM losses.

Two-step pilot-scale biofilter system for the abatement of food waste composting emission

A pilot-scale two-step biofilter system was evaluated in treating food waste composting emission for 220 days. Wood chips were packed at the bottom section while mixture of rock wool and earthworm compost (6% w/v) was packed at the top section. Inlet ammonia concentration was found to be dominant and intermittent. The overall ammonia removal of over 98% was achieved, 70% of which was removed in the wood chip section. The highest ammonia elimination capacity was determined to be 39.43 g-NH3/m3/h at 99.5% removal efficiency. From biodegradation kinetic analysis, the maximum removal rate, V m, of the wood chip section was determined to be 200 g-NH3/m3/h and the saturation constant, K s, 180 mg/m3. For the rock wool-earthworm cast mixture section, the V m was 87 g-NH3/m3/h and K s was 87 mg/m3. Complete removal of hydrogen sulfide and most trace compounds were achieved by the biofilter. Highest hydrogen sulfide elimination rate was 0.22 g-H2S/m3/h. The biofilter was optimized from 24 to 16 s EBRT with resulting low average pressure drops of 16 and 29 mm H2O/m, respectively.

Disinfection performances of stored acidic and neutral electrolyzed waters generated from brine solution

The feasibility of storing two electrolyzed waters (EW), acidic (AEW) and neutral (NEW), were elucidated through Escherichia coli O157:H7 and Salmonella typhii inactivation experiments. Free chlorine (FC) loss, pH and oxidation-reduction potentials were monitored for 30 days. Initial activities of fresh EWs were determined at 5 mg Cl2·min/L for 8 Log10 inactivations of both strains. However, stored EWs exhibited activity declines which were associated to FC losses. All FC loss rates were first-order; AEWs underwent two phases of decays while NEWs had single decay rate constants. Two FC loss mechanisms were identified: chlorine (Cl2) volatilization and hypochlorous acid (HOCl) decomposition, wherein Cl2 volatilization occurred at a faster rate. Chlorine volatilization was primarily influenced by storage condition as indicated by intensive FC losses on EWs stored in open vessels. Under the same storage conditions (open or closed), Cl2-rich AEW experienced higher FC losses which indicated the higher stability of HOCl-rich NEW. Overall, FC losses could be minimized if (1) samples are stored in closed vessels and (2) Cl2 is not the main chlorine component. NEW in closed vessel is the most feasible system for EW storage; its initial activity (8 Log10 inactivation) was preserved for up to 17 days.

Removal of odorous compounds emitted from a food-waste composting facility in Korea using a pilot-scale scrubber.

ABSTRACT Monitoring and control of odorous compound emissions have been enforced by the Korean government since 2005. One of the point sources for these emissions was from food waste composting facilities. In this study, a pilot-scale scrubber installed in a composting facility was evaluated for its performance in the removal of malodorous compounds. The exhaust stream contained ammonia and methylamine as the major odorants detected by the threshold odor test and various instrumental techniques (GC-FID, FPD, MS and HPLC/UV). For the scrubber operation, the column was randomly packed with polypropylene Hi-Rex 200, while aqueous sulfuric acid was selected as the scrubbing solution. To achieve 95% removal, the scrubber must be operated by using H2SO4 solution with pH at < 6.5, liquid to gas ratio > 4.5, gas loading rate < 1750 m3/m3-hr and contact time < 0.94 s. The scrubber performance was further evaluated by determining the mass transfer coefficients and then monitoring for 355 days of operation. The pilot-scale scrubber maintained > 95% ammonia and methylamine removal efficiencies despite the fluctuations in the inlet (from composting facility exhaust stream) concentration. The optimum operating conditions and scrubber performance indicators determined in this study provides a basis for the design of a plant-scale scrubber for treatment of composting facility gas emissions.