Final Report Reducing Taste and Odor and Other Algae-Related Problems for Surface Water Supplies in Arid Environments Prepared by Milton Sommerfeld Department of Plant Biology Arizona State University, Tempe, AZ Paul Westerhoff Department of Civil and Environmental Engineering Arizona Stae University, Tempe, AZ Larry Baker Baker Consulting St. Paul, MN Contributors: Qiang Hu, Mario Esparza-Soto, Darlene Bruce, My-Linh Nguyen, Thomas Dempster, Kirsten Hintze, Samanth Dawson, Mari Rodriguez, Michelle Cummings, Marisa Masles, and Dave Lowry Arizona State University, Tempe, AZ August 2002 ACKNOWLEDGEMENTS This project was financially supported by the City of Phoenix, AZ. Field, laboratory and analytical activities were performed by a series of talented post-doctoral researchers (Mario Esparza-Soto, Qiang Hu, Darlene Bruce), analytical technicians (Marisa Marsles, David Lowry), Ph.D. graduate students (Tom Dempster, My-Linh Nguyen, Kirsten Hintze), Master graduate students (Samanth Dawson, Mari Rodriguez-Hernandez, Michelle Cummings), and undergraduate students. ii ACRONYMS ADEQ - Arizona Department of Environmental Quality CAP - Central Arizona Project CAWCD - Central Arizona Water Conservatin District Cfs - Cubic feet per second COP - City of Phoenix DOC- dissolved organic carbon DBP - disinfection byproduct FPA - GAC - granulated activated carbon GC/MS - gas chromatography/mass spectroscopy HAA- haloacetic acids HPA - MCL - Maximum Contaminant Limit MWD - Metropolitan Water District of Southern California MIB - 2- methylisoborneol MPI - Malcolm Pirnie Inc. NAWQA - National Water Quality Assessment program (USGS) PAC- powdered activated carbon SPME - Solid Phase Micro-Extraction SRP - Salt River Project T&O - taste and odor T&OCS - Taste and Odor control Study THM - trihalomethane USEPA - U.S. Environmental Protection Agency USGS - United States Geological Survey UV - ultraviolet WTP - Water Treatment Plant iii TABLE OF CONTENTS SECTION PAGE EXECUTIVE SUMMARY ................................................................................................................ 1 SECTION 1: PROJECT OBJECTIVES........................................................................................ 13 SECTION 2: MONITORING PROGRAM (TASK 1)..................................................................... 16 SECTION 3: FIELD SCALE EXPERIMENTS TO EVALUATE T&O CONTROL MEASURES (TASK 2) ................................................................................................................. 73 SECTION 4: ASSESSMENT OF IN-PLANT CONTROLS (TASK 3) .......................................... 95 SECTION 5: CONTROLLED LABORATORY EXPERIMENTS (TASK 4) ................................ 115 SECTION 6: STUDIES OF DOC SOURCE, CHARACTERIZATION, AND TREATABILITY (TASK 5) ............................................................................................................... 187 SECTION 7: MIDCOURSE EVALUATION (TASK 6) ................................................................ 209 SECTION 8: IMPLEMENTATION CONTROLS (TASK 7)......................................................... 257 SECTION 9: SUMMARY AND RECOMMENDATIONS ............................................................ 282 APPENDIX A: BASELINE DATA TABLES................................................................................. 295 iv EXECUTIVE SUMMARY The goal of this project was to develop a comprehensive management strategy to reduce algae- related water quality problems for drinking water supplies in arid environments. Algae can cause problems in water supply lakes, water distribution canals, and water treatment plants. The primary focus was the taste and odor problem. However, because algae also produce dissolved organic carbon (DOC), which reacts to form disinfection by-products (DBPs) and contribute other in-plant operational problems, these issues will also be addressed. This final report includes a summary of findings related to research and field-scale activities aimed at algae-related problems. Specific sections include: · Summary of research report (Tasks 1 through 5) · Implementation report and Overview of Guidance Manual (Tasks 6 through 8) · Summary of Research Products · Future Research Needs · Recommendations for T&O Control and regional T&O management RESEARCH REPORT (TASKS 1 THROUGH 5) The research aspect of this project included five tasks. The major findings of each task will be summarized. The five tasks included: · Task 1 – Monitoring program · Task 2 – Field scale experiments to evaluate T&O control measures · Task 3 – Assessment of in-plant controls · Task 4 – Controlled laboratory experiments · Task 5 – Studies of DOC source, characterization, and treatability Task 1 – Monitoring Program The initially selected set of 20 baseline monitoring sites proved to be well-selected, with only a few additional sites added to the monthly monitoring program in order to obtain a comprehensive evaluation of the raw water system for the City of Phoenix. The hydraulic operation of this system is complex and dynamic. During the period of study, precipitation and watershed runoff was below average, and therefore represented a “drought” condition. Results differing from those encountered and reported here may occur during wetter years in the watershed. The work conducted during this task has lead to an improved understanding of the factors leading to T&O production in arid region surface water systems. MIB and Geosmin concentrations exhibited seasonal patterns (highest in summer and fall) and 1 significant spatial variability. MIB data are shown in Figure E.1 as contour plots with respect to concentration (ng/L). MIB was the dominant T&O compound observed in the watershed and finished drinking water systems. Geosmin occurred at lower concentrations. MIB and Geosmin spatial and temporal trends followed predictable patterns with regards to water temperature and nutrient conditions. The highest MIB concentrations (>50 ng/L) were found in the reservoir epilimnion and downstream points of the canal systems. The algae species responsible for T&O compound production ("culprit" algae) represented only a very small percentage of the total algae numbers or biomass. Intensive monitoring indicated “hot spots” for MIB production. For example, plankton in the open water of Saguaro Lake appeared to be the source of MIB, rather than pockets of benthic algae in shallower portions of the lake. In contrast, periphytic algae attached to the concrete- lined canal walls at two locations was a major source of caused MIB production in Arizona Canal. Task 2 – Field Scale Experiments to Evaluate T&O Control Measures Due to access limitations to reservoirs and non-site specific T&O spatial occurrence in the reservoirs, field-scale experiments were focused on MIB and Geosmin production in the canals. Experiments focused on (1) mechanical canal brushing of canal walls, (2) chemical liquid copper application to the canals, and (3) polymeric biocides fixed to canal walls. Mechanical brushing removed over 80% of the periphyton biomass from the canal walls and essentially lead to zero net MIB production along the length of the treated canal section. Copper addition lead to a gradual decrease in biomass, but a more rapid decrease of in-canal MIB production. In the weeks after both mechanical brushing and copper treatment biomass regrowth occurred, followed by MIB production. The treatments appear effective for two to three weeks. A combination of first mechanical brushing followed one week later by copper treatment would be a recommended course of action for MIB control in reaches of canals identified to produce T&O compounds. Task 3 – Assessment of In-plant Controls An assessment of each City of Phoenix WTP was conducted. No in-plant production of MIB or Geosmin was documented at any of the City of Phoenix WTPs which all practice periodic prechlorination, although reports of such production have been noted at City of Tempe and Chandler which do not prechlorinate. Conventional WTPs offer limited potential to control MIB and Geosmin present in the raw/influent water. The COP therefore has four options to minimize MIB and Geosmin in the finished water: 1. Minimize raw water T&O levels through upstream controls (e.g., canal treatments) 2. Optimize PAC brand selection, feed rates, and feed capability 3. Allow filters to operate in a biological mode 4. Upgrade treatment processes to include advanced oxidation processes or nanofiltration/reverse osmosis membranes. 2 Task 4 – Controlled Laboratory Experiments Experiments were conducted in the laboratory to (1) screen parameters important for implementation at field- or full-scale and (2) gain insights into a biological process or mechanism. Powder activated carbon (PAC) tests demonstrated PACs ability to remove MIB and Geosmin from surface waters in Arizona. Performance of PAC brands varied and was lower in surface water than distilled water. Kinetics tests for MIB adsorption requires at least one hour of contact time. Ozone and advanced oxidation processes that produce hydroxyl radicals can oxidize MIB and Geosmin, and are more effective than chlorine dioxide; chlorine did not oxidize MIB or Geosmin. Two biocide coatings fo the canal walls were evaluated. Copper biocides can kill MIB-producing algae, but organically-complexed copper products should be avoided since they react with free chlorine to form organic chloramines. Inorganically complexed copper products are recommended. Coating concrete canal walls with biocides or photo-reactive paints