Finite fraction method for tracking desinfection by-product precursors in water treatment
Department of Civil and Environmental Engineering
Doctor of Philosophy
Marhaba, Taha F.
Hsieh, Hsin Neng
Luo, Robert G.
Schuring, John R.
Drinking water --Purification.
Dissolved Organic Matter (DOM) has been the subject of recent regulatory activities and agenda. Among them are the Infonnation Collection Rule (ICR), the Disinfectants/Disinfection By-Product Rule (D/DBPR) and the Interim Enhanced Surface Water Treatment Rule (ESWTR). Both the latter two have provisions to limit the formation of disinfection by-products (DBP) by controlling reactivity and removal of DOM or both. Brief regulatory review of these rules was given.
Although the topic of DBP formation potential and DBP precursor removal have been studied by many researchers since Rooks (1974), the efficacy of methods that have been developed to date has been handicapped by the notion that DBP precursors can be, and have been, represented by the surrogate parameter TOC, which is aggregate in nature. To contribute to the current knowledge concerning DBP precursors and their formation potential, the objectives of this research were to develop a rapid method for the identification of DBP precursors, establish a DBP formation potential database and correlations, and develop computer codes to be used as a toolkit to facilitate the investigation of DBP precursors and formation potential.
In this research, finite fraction method (FEM) was used to isolate and fractionate DOM from locations within three water treatment plants (WTP) which draw water from two different sourcewaters in north and central New Jersey. A resin adsorption method was used to fractionate and isolate six fractions. Operationally, these fractions were termed: hydrophobic acid, hydrophobic neutral, hydrophobic base, hydrophilic acid, hydrophilic neutral and hydrophilic base. Fraction mass balance confirmed the effectiveness of the method.
Each fraction was subjected to a 7-day chlorine disinfection by-product (DBP) formation potential test at standard condition of pH 7 and temperature of 25 dog. C. Results showed that all fractions are DBP precursors and that each fraction has different reactivity levels to the formation of the three classes of DBPs which are trihalomethanes (THMs), haloacetonitriles (HANs) and haloacetic acids (HAM). The hydrophilic acid and hydrophobic neutral fractions were found to be the most problematic precursors to the formation of THM and HAA DBPs, respectively.
Spectral Fluorescent Signature (SFS) is a process of subjecting each reasonably finite component (or fraction) of DOM to fluorescence scanning to produce unique spectral fluorescent characteristic of signature (hence the term SFS). SES method was investigated and developed to rapidly identify the various fractions of DOM. It was found that (1) each fl-action fluoresces uniquely in certain region of the 3-D spectrum, (2) the fraction identification was a function of the fluorescent intensity, the slope of fluorescence peak and the area under the peak spectrum. In fact, it was found that the product of the spectral slope and the spectral area establishes a shape factor (SF) that is unique to give the fraction an identifiable digital signature.
Computer codes were developed using graphical user interface (GUI) features to facilitate rapid identification of DUP precursors and computation of the corresponding formation potential by iterative method in searching the databases. Method validation was conducted. Good correlations were achieved.
The variation of each DBP precursor throughout the treatment train of the water treatment plant was also examined to provide insight into the effectiveness of the unit operation with regard to the removal of the precursor. For most precursors, coagulation and sedimentation units appeared to be most effective in the removal. For the problematic precursors however, such unit processes did not seem to be as effective.
njit-etd2000-089 (355 pages ~ 17,407 KB pdf)
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Created May 11, 2007