Jae-Hwan Ahn

Separation of fine particles at different frequencies and HRTs using acoustic standing waves

The objective of this study was to evaluate the separation of fine particles using several frequencies and hydraulic retention times (HRTs) in an acoustic standing wave reactor without any separate cooling devices. The acoustic standing wave reactor consisted of sufficient space (over 100u2005mm) between the transducer and reflector, resulting in a slight increase in temperature. However, the increase in temperature did not affect the formation of standing waves and particle aggregations in our experiments. The results indicated that the turbidity removal efficiencies of fine kaolin particles, when using frequencies of 580u2005kHz, 1, and 2u2005MHz, increased with longer standing wave operation time. Especially, the turbidity removal efficiencies for 1 and 2u2005MHz were higher than that for 580u2005kHz because the wavelength (λ) of the 580u2005kHz wave was longer than that of the 1 and 2u2005MHz waves. Furthermore, the turbidity removal efficiency of kaolin in a continuous reactor improved with increasing hydraulic retention times (HRTs), and the reactor was more effective with 1 and 2u2005MHz used in parallel instead of 1 and 2u2005MHz used individually under the same HRT conditions with the entrance length (EL) having no adverse effect.

Concentration Characteristics of Runoff Pollutants using Statistical Techniques during a Storm: the Case Research of Driveway Site in Korea

This research was conducted to investigate the magnitude and nature of the emission of runoff pollutants with the goal of quantifying stormwater pollutant concentrations from driveways site. A statistical summary for concentration characteristics of driveway runoff is provided based on the various analysis techniques. Runoff water qualities in temporal variation were generally higher in wet season than in dry season with a high degree of variability. The 95 % confidence intervals of washed-off pollutant concentration are ranged to 82.4-141.4 mgL -1 for TSS, 53.3-87.6 mgL -1 for Turbidity, 19.0-38.7 mgL -1 for BOD, 34.0-59.2 mgL -1 for COD, 16.4-27.4 mgL -1 for DOC, 4.3-5.6 mgL -1 for TN and 0.25-0.34 mgL -1 for TP, showing the high values based on the surface or lake quality standards in Korea. The first flush effect is mostly occurred within initial 30 min of storm duration. Concentrations of water quality constituents in urban stormwater are often expressed in probabilistic terms using statistics such as the mean and standard deviation and selected quintiles. Three probability distributions, weibull in TSS and Turbidity, lognormal in BOD and COD and gamma in DOC, TN and TP were fitted and the goodness-of-fit was assessed using the Anderson-Darling test. The correlation matrix of all water quality variables shows significant relationships between all parameters (P<0.001) and the correlation of between TSS and Turbidity showed relatively strong positive relationship (r=0.825). This research presents the concentration changes and characteristics during storm occurrence. The new concept explaining the relationship among the emission effects of runoff pollutants are suggested using statistical techniques.