Modeling of Mass Transfer and Synthetic Organic Compound Removal in a Membrane Softening Process
The rejection of six synthetic organic compounds (SOCs) from a potable water source was investigated using a nanofiltration membrane softening process. A complete single-stage membrane pilot plant was constructed that utilized a single spiral wound thin film composite polyamide membrane having a molecular weight cutoff of 300. The SOCs were investigated separately in six, one-month increments and were as follows: ethylene dibromide (EDB), dibromochloropropane (DBCP), chlordane, heptachlor, methoxychlor and alachlor. Other monitored solutes were dissolved organic carbon, total dissolved solids, sulfate, sodium, iron, fluoride, alkalinity, calcium and total hardness, trihalomethane formation potential, total organic halide, and the solute indicators color and pH. Of the six socs investigated, chlordane, heptaclor, methoxychlor and alachlor were completely rejected by the membrane. EDB was not rejected and DBCP was partially rejected by the membrane. DBCP mass transfer was determined to be diffusion controlled. soc mass balances indicated that membrane adsorption of the three largest molecular weight (MW) socs had occurred, and SOC rejection increased as MW increased. Rejection of inorganic solutes increased as MW and species charge increased. No effect on solute mass transfer of any solutes resulted from membrane stream velocities varying from 0.19 to 0.52 ft/sec. Field determinations of solute mass transfer coefficients (MTCs) were determined to exhibit a normal distribution with charge and MW. Dimensional analysis (Sherwood number) was used to model solute MTCs where nonelectrolyte MTCs were predicted with a Wilke-Chang diffusion coefficient and ionic MTCs were predicted with a Nernst diffusion coefficient. In addition, a membrane model was developed using the homogeneous solution diffusion model and a completely mixed first order transient response model. The resultant model was evaluated by using a step chloride input into the existing single membrane pilot plant and a three-stage pilot plant. The model was shown to accurately describe each specific stage and the overall system transient response. Actual data and theoretical predictions are presented for single-stage and three-stage membrane softening plants.
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Taylor, James S.
Doctor of Philosophy (Ph.D.)
College of Engineering
Civil and Environmental Engineering
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Dissertations, Academic -- Engineering; Engineering -- Dissertations, Academic
Duranceau, Steven J., "Modeling of Mass Transfer and Synthetic Organic Compound Removal in a Membrane Softening Process" (1990). Retrospective Theses and Dissertations. 3978.