No abstract

A parallel factor (PARAFAC) analysis approach was used to study the character and composition of dissolved organic matter (DOM) in a multicoagulant (two aluminum-based coagulants) full scale drinking water treatment plant. A three year, long-term assessment was conducted based on deconstruction of the excitation-emission matrices (EEM) of over 1000 water samples collected before and after parallel coagulation treatment basins. Two humic moieties and a protein-like group were identified in the raw and treated waters. Apportionment of fluorophores was established using a novel approach based on the overall fluorescence intensity (OFI) of PARAFAC components. Uncorrected matrix correlation (UMC) revealed minimal changes of the fluorescence moieties after treatment (UMC > 0.98), and a comparable effect of both coagulants on the structure (UMC > 0.99) and distribution of these groups. Coagulation increased the proportion of the protein-like fluorophore and preferentially removed a humic-like group irrespective of the coagulant. Preference for this moiety was supported by a coagulant-affinity factor derived from the association between PARAFAC components after treatment. The suitability of a PARAFAC-based approach for coagulant evaluation/selection was demonstrated when compared to a dissolved organic carbon (DOC)-based criterion. This paper contributes to the understanding of the behavior of PARAFAC components in water treatment processes and presents several approaches for the future monitoring and control of coagulation at full scale treatment facilities.

A comparative study of two coagulants, aluminum sulfate (Alum) and aluminum chlorohydrate (ACH), used in parallel in a full scale water treatment plant (WTP) in Ohio from October 2009 to December 2012, was conducted to determine disinfection by-product (DBP) formation potential removal based on both dissolved organic matter (DOM) and fluorescence-derived metrics. Water quality parameters and fluorescence intensity of water samples collected before and after coagulation were measured three times per week and fluorescence matrices were analyzed using parallel factor (PARAFAC) analysis, while DBP formation potential was measured in a weekly basis in pre-and post-coagulation water samples. This study revealed that Alum consistently removed more trihalomethane (THM) formation potential per mg/L of dissolved organic carbon (DOC) than ACH. ACH treated waters averaged approximately 33% more THM formation potential when normalized to DOC. Similarly, haloacetic acid (HAA) formation potential averaged 10% higher in ACH treated waters. From the fluorescence analysis, PARAFAC components C1 and C2 (humic-like fluorophores groups) removal were 23% and 16% higher, respectively, with Alum when compared to ACH. Monte Carlo simulations, based on neural network models developed from the field data, were performed to compare DBP formation across a wide range of conditions. At similar pH, the model results showed that ACH coagulated water had 13% and 20% higher THM and HAA formation potential, respectively, when compared with Alum. The observations from this study reveal that a coagulant's preferential removal of DBP precursors has an impact on DBP formation despite similar DOC removal.

Surface water presents many challenges for water treatment, including stricter regulation of disinfection byproducts (DBPs) mandated by the US Environmental Protection Agency's Stage 2 Disinfectants/Disinfection Byproducts Rule (D/DBPR). Crucial to utilities being in compliance with the Stage 2 D/DBPR is the ability to obtain real‐time DBP formation potential and to monitor dissolved organic carbon removal as changes are made to the treatment train.