Grantee Research Project Results

2014 Progress Report: Fluoride, DBP Precursors, and Particles: Simultaneous Removal with Aluminum Salts a Solution for Small Drinking Water Systems

EPA Grant Number: R835176
Title: Fluoride, DBP Precursors, and Particles: Simultaneous Removal with Aluminum Salts a Solution for Small Drinking Water Systems
Investigators: Lawler, Desmond , Katz, Lynn
Institution: The University of Texas at Austin
EPA Project Officer: Page, Angela
Project Period: December 1, 2011 through November 30, 2014 (Extended to June 19, 2016)
Project Period Covered by this Report: December 1, 2013 through November 30,2014
Project Amount: $499,357
RFA: Research and Demonstration of Innovative Drinking Water Treatment Technologies in Small Systems (2011) RFA Text | Recipients Lists
Research Category: Drinking Water , Water

Objective:

The goals of this project are to (1) develop a treatment system for the simultaneous removal of fluoride, natural organic matter (NOM), and particles from natural waters that are used as drinking water sources, and (2) demonstrate the efficacy of the system through small-scale pilot testing of a continuous flow system using a real drinking water source. Because NOM is the precursor of many disinfection by-products (DBPs), this treatment system also will reduce DBP formation. The system will be specifically designed for small water systems (SWS) with limited capital and personnel resources available. The treatment system will exploit the favorable interactions of all three contaminants with aluminum (oxy)hydroxides.

Progress Summary:

We proposed a three-phase study: Mechanistic studies, Laboratory-scale demonstration, and Pilot-Scale demonstration. Research during this year focused on laboratory-scale demonstrations within Phase II and the first pilot-scale demonstration for Phase III. Laboratory-scale experiments highlighted the impact of fluoride on aqueous aluminum residuals and demonstrated that the presence of aluminum-fluoride complexes could significantly reduce precipitation and increase aqueous aluminum concentrations in the effluent. In some cases, the aluminum concentrations exceeded EPA secondary drinking water standards. The results also demonstrated that at low alum doses (20 mg/L), the presence of organics in dual fluoride/organic ligand systems led to reduced aqueous aluminum concentrations compared to single ligand fluoride systems. It is likely that these results are due to the impact of the organics on aluminum hydroxide floc characteristics. Finally, a pilot-scale system was assembled and tested at the Mackenzie Municipal Water Authority. Raw water from Lake Mackenzie was treated in our pilot plant that consisted of rapid mixing, flocculation and sedimentation. Fluoride and natural organic matter removal occurred in the pilot study. While increased alum doses led to increased fluoride and dissolved organic carbon, removals were lower than observed in the laboratory studies. This was in part due to higher pH values observed in the field as well as higher dissolved organic carbon levels present in the water during field testing.

Future Activities:

Our primary focus in the final year of the project will be directed toward completing an additional pilot study at Manitou Springs, CO. The raw water at Manitou Springs, CO contains lower total organic carbon levels, which will allow us to validate the importance of pH on fluoride and NOM removal during alum coagulation. In addition, the success of alum coagulation processes for fluoride removal in small water systems requires a better understanding of the impact of ligands on fluoride removal and aluminum hydroxide precipitation. Additional mechanistic and laboratory-scale experiments will be used to evaluate the impact of fluoride and organic ligands on floc characteristics and aqueous aluminum residuals.

Journal Articles:

No journal articles submitted with this report: View all 14 publications for this project

Supplemental Keywords:

fluoride removal, alum coagulation, NOM removal;

Progress and Final Reports:

Original Abstract

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.