The Henry's law constant is important in the gas-liquid mass transfer process. This study investigates the apparent dimensionless Henry's law constant, also known as the gas-liquid partition coefficient (K'H), of both hydrophilic (methanol, isopropanol and acetone) and hydrophobic (toluene and p-xylene) organic compounds. The K'H in deionized (DI) water, wastewater with a maximum total dissolved organic carbon (DOC) content of 700 mg/L, and DI water mixed with a maximum activated sludge suspended solid (SS) concentration of 40,000 mg/L, are measured by the single equilibrium technique (SET) at 288 K, 293 K, 298 K and 303 K.
Experimental results indicate that the K'H of the three tested volatile organic compounds (VOCs) varies according to three situations. First, the K'H of the hydrophilic compounds in mixed liquor with the maximum suspended solid concentration is higher than that in DI water. The maximum rates of increase of K'H from KH in the SS range between 288 K and 303 K are 27.2% for methanol, 23.5% for isopropanol and 16.1% for acetone.
Second, the K'H values for toluene and p-xylene are lower than those in DI water. Between 288 K and 303 K, the maximum reduce rate of K'H from KH in the SS range are 87.3% for toluene and 93.0% for p-xylene.
Third, the K'H values of all of the test compounds in the wastewater are lower than those in DI water. The maximum rates of decrease of K'H from KH in the DOC concentration range between 288 K and 303 K are 1.2% for methanol, 1.1% for isopropanol, 1.7% for acetone, 14.3% for toluene and 20.1% for p-xylene.
A model is presented to related K'H to wastewater DOC and concentration of SS in the activated sludge, using an organic carbon-water partition coefficient (KOC) and activated sludge-water partition coefficient (KSS) as model parameters. The model is verified, and model parameters for test compounds are estimated.
Temperature variations of K'H can be regressed using van't Hoff's equation. The gas-water phase change enthalpy £GH'gw rises approximately linearly with increasing SS for hydrophobic toluene and p-xylene. K'H variation can be controlled by SS concentration and temperature in activated sludge system.
The temperature effect of KOC and KSS are also observed. KOC and KSS decrease with as the temperature rises from 288 K to 303 K. The VOCs phase change enthalpy and entropy can be calculated using thermodynamic analysis. The partition of VOCs into the organic carbon phase releases energy, and thus prefers low temperatures. Lower temperatures and higher SS concentrations lead to lower K'H for hydrophobic VOCs, while higher SS concentrations result in higher K'H for hydrophilic VOCs.
Organic-rich wastewater or low-biomass mixed liquor can successfully remove hydrophilic VOCs from contaminated air streams by bioscrubber. However, bioreactors scrubbed with high biomass-containing mixed liquor perform better than regular activated sludge concentration in removing hydrophobic VOCs. The experimental results thus support the design and operation of bioscrubber and suspended operable bioreactors.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0703106-105238 |
| Date | 03 July 2006 |
| Creators | Lin, Jun-Hong |
| Contributors | none, none, none, none, none, none, Ming-Shean Chou |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0703106-105238 |
| Rights | unrestricted, Copyright information available at source archive |
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