Modeling DOC Removal Enhanced Coagulation

Abstract

Enhanced coagulation is proposed by the US Environmental Protection Agency as a best available technology to remove dissolved organic carbon (DOC). In this article, an improved model of DOC removal by enhanced coagulation is proposed based on Langmuir isotherm theory. For the purpose of the model, DOC is assumed to comprise three fractions: humic acid, nonpolar, and nonsorbable. The nonsorbable fraction is not removed. Removal of the humic acid fraction is dependent on pH, whereas that of the nonpolar fraction is not. This model, which includes five coefficients, was fitted to data from experiments on various Australian and US waters. It predicted the final DOC for a given metal coagulant and water within a standard deviation of the error of either 5.5% or 0.15 mg/L of DOC over the valid combinations of coagulant dose and pH. Generally at a given pH alum was found to remove more DOC at lower doses than ferric coagulant, whereas at higher doses, ferric coagulant removed more DOC than alum.

Efficacy of Removal of CCL Viruses under Enhanced Coagulation Conditions

“…Enhanced coagulation was identified by the D/DBP Rule as the best available technology to remove DOC. 1 Traditional coagulation processes target turbidity removal, whereas enhanced coagulation targets the removal of turbidity and natural organic matter (NOM) using increased coagulant dose and/or pH adjustment. 2 The Stage 1 DBP Rule requires many systems using surface water or groundwater directly under the influence of surface water to implement enhanced coagulation.…”

Changes in the quality of river water before, during and after a major flood event associated with a La Niña cycle and treatment for drinking purposes

“…mEnCo© modelling software mEnCo© is a modelling software package that was designed to assist WTP operators in managing chemical dosing for DOC removal (van Leeuwen et al, 2003(van Leeuwen et al, , 2005Kastl et al, 2004). Model inputs are four raw water quality parameters, UV measured at 254 nm, colour measured at 456 nm, turbidity and alkalinity which are routinely measured at the WTP laboratory (van Leeuwen et al, 2009).…”

“…For comparison of the characters of organics in these waters before and after alum treatment, three alum doses were selected: (1) the mEnCo predicted dose (EnCD), (2) at 0.75 of the EnCD, and (3) at a very high coagulant dose which more than double the EnCD. The 0.75 EnCD was used to compare removals of organics at a nominal dose rate lower than that considered needed for enhanced coagulation, while the very high coagulant dose was used to ensure differentiation between the coagulable and non-coagulable organics (Kastl et al, 2004) at pH 6.…”

“…The application of the high coagulant dose at controlled pH has no practical relevance other than to enable differentiation of coagulable from non-coagulable DOC and characterization of the organics that are recalcitrant to removal at a specified coagulation pH. The approach of using high coagulant doses for this purpose has been previously reported (Kastl et al, 2004;Chow et al, 1999). For organics remaining in post-treated waters, a range of characterization methods can be used, including those applied in this study, as well as Pyrolysis-GC/MS, resin fractionation and 13 C NMR (Chow et al, 1999;Gadel and Bruchet, 1987;Wong et al, 2002).…”

Investigation of the adsorption characteristics of natural organic matter from typical Chinese surface waters onto alumina using quartz crystal microbalance with dissipation

“…Edwards [1] and Kastl et al [6] established semi-empirical, nonlinear mathematical models that allow prediction of total organic carbon (TOC) removal by coagulation in drinking water treatment. These models require input parameters of coagulant type and dose, coagulation pH, raw water TOC concentrations or UV absorbance at 254 nm.…”