Little Rock, AR Projects

Evaluation of Lake Maumelle and Winona Water Quality

Ozark Point and Wilson Water Treatment Plant Performance Evaluations

Pilot Plant Studies of GAC & Alternative Disinfectants

H2O’C was commissioned to conduct a progressive series of full-scale and pilot-plant studies to evaluate the causes of and assess methods for controlling increasing levels of DBP’s in the Little Rock distribution system.

I. Source Water

1. Evaluation of Source Water Quality: Review of Historical Data
2. Enhancement of USGS Analytical Program: Metalimnetic Peak, Zooplankton
3. Characterization of Organic Matter in Lake Winona and Lake Maumelle
4. Seasonal Variations in Source Water Quality
5. Effect of Release of Fish Hatchery Water: Organics and nutrient enrichment.

II. LRMWW In-House Laboratory Capability

1. Purchase and Use of Epifluorescent Microscope, Gas Chromatograph, TOC Analyzer
2. Training of Laboratory Staff in Biological and Chemical Methodologies
3. Establishment of Plant and Distribution System Monitoring Program for TOC &THM
4. Analytical Methodology for Pilot Plant Operations

III. Pilot Plant Modifications, Operations

1. Design and Installation of Filter Media
2. Construction of New Manometer Board
3. Connection of Wilson Plant Settled Water
4. Re-Piping of Ozonated Water Return Line
5. Establishment of Pilot Plant Sampling Protocol
6. Calculation of Chemical Dosages, Feed Rates and Storage Requirements for Continuous Pilot Plant Operation.
7. Addition of GAC Post-Adsorbers: 10, 20 minute EBCT

IV. Pilot Plant Studies

1. Filtration Studies: Comparison of Ozark Point, Wilson, Multi-Media and GAC-Capped Filters with respect to turbidity, aluminum, bacteria, TOC, and head loss development.
2. Observation of Mud-Ball Formation in Filter Beds
3. Pilot Plant Studies: Conventional and Enhanced Coagulation with Alum; Conventional and Enhanced Coagulation with Iron (Ferric Sulfate)

V. Evaluation of Ozark Point and Wilson Plant Performance

1. Wilson Plant: Distribution of Coagulant, Modification of Distribution Weirs
2. Wilson Plant: Settling of Alum Floc in Flocculation Basins
3. Wilson Plant: Sedimentation Basin Effectiveness
4. Wilson Plant: Evaluation of Passage of aluminum through Filters, Control for Reduction of aluminum in Filter Effluents
5. Wilson Plant: Diurnal Variations in pH, alkalinity, chlorine in Settled and Filtered water. Effect of UV-catalyzed reduction of chlorine on night-time chlorine concentrations, pH and alkalinity; corrosion of filter boxes.
6. Effect of Backwash Water Return on TOC of Water in Sedimentation Basins.
7. Evaluation of Ozark Point Plant Performance Characteristics.
8. Evaluation of Chemical Feed Data: Alum, KMnO4, PAC, and Polyphosphate Feed.

VI. TTHM and HAA Formation in LRMWW Water System

1. Location of TTHM Formation Within System
2. Effect of Water Temperature on TTHM Formation
3. Effect of pH on Removal of Organic Matter
4. Rate of Formation of TTHM
5. Seasonality of TTHM Formation in Wilson and Ozark Point Treatment Plants
6. Long-Term, Intensive Monitoring of TTHM in Distribution System
7. Review of Historical Data on Distribution System TTHM
8. Evaluation of Data on Haloacetic Acids in LRMWW Water System

VII. Evaluation of Techniques for Controlling D/DBP: Bench-Scale and Pilot Studies

1. Source Water TOC Control
2. Powdered Activated Carbon, Potassium Permanganate
3. Chlorine Dioxide
4. Chloramine
5. GAC Post-Adsorbers and GAC-Capped Filter

VIII. Detailed Recommendations for System Modification and Control

References

Mr. Gary Hum
Little Rock Municipal Water
10901 Rocky Valley Drive
Little Rock, AR 72212
501-377-1256

Relevance

• Seasonal evaluation of organic matter in Little Rock’s lake water sources
• Full-scale evaluation of performance of Ozark Point and Wilson Water Treatment Plants
• Pilot plant studies of enhanced coagulation; PAC, GAC and KMnO4
• Chlorine dioxide as an alternative disinfectant