Sunil Kommineni, Kristen Amante, Bhavana Karnik, Milton Sommerfeld, and Thomas Dempster

OBJECTIVES:

The objectives of the study were to (1) gather and analyze existing information on the types of algae that are found in water treatment plants (WTPs), (2) identify treatment plant operational and water quality issues triggered by algae growth, (3) develop case studies of treatment plants that are controlling or mitigating algae using different strategies, and (4) develop utility guidance and recommendations for sampling, characterization, and operational and design strategies for mitigating algal growth.

BACKGROUND:

Until now, there has been a lot of research done on controlling algae growth in source waters. However, the strategies to control algal growth within the WTPs were developed mostly by the in-house experts of utilities and operators of treatment plants. Some utilities are more successful in controlling algal growth compared to other utilities that are trying to reach an optimal strategy through trial-and-error methodology. The goal of this study was to review and document the existing strategies and lessons learned with respect to algal control by various utilities. This research focused on the types of algae found in treatment plants and strategies to control algal growth.

HIGHLIGHTS:

National survey findings revealed that most of the utilities struggle with algal control strategies. The utilities rely on the water treatment processes to address the algal issues. The survey findings, case studies, and algae characterization will enable utilities to identify algae in their respective water treatment plants and provide guidance in selecting optimal chemical addition strategies and suggested operational and design techniques to control algal growth. The algae characterization identified algal speciation that can vary based on physical location and demographic location of the water; however, there are a common algal species of particular taxa that are always present in WTPs with algal issues.

APPROACH:

A literature review was performed to gather and analyze (1) existing information on types of algae found in water treatment plants and (2) research on strategies used to mitigate these algae. A nationwide utility survey was conducted to identify current strategies used for controlling algae within specific treatment trains. Case studies were developed on treatment plants that are controlling or mitigating algae using different strategies. Algae characterization was conducted at selected plants across the United States, at each part of their treatment train to identify strategies to mitigate specific algae types. Based on the information collected in this study, recommendations and guidance for utilities were developed to include (1) sampling and analysis to address algal issues within the water treatment plant, (2) optimal control strategies that are demonstrated to work for other water utilities, and (3) best practices for operation and maintenance to reduce algal issues in treatment plants.

RESULTS/FINDINGS:

The literature review summarized the current state-of-knowledge with respect to algae occurrence, characterization, and control strategies. The algae characterization showed the main algae types detected were blue-green algae (Cyanobacteria), green algae (Chlorophyceae), and golden algae (Chrysophyceae). Case studies for the utilities were conducted to document different strategies to address algal issues and their success in mitigation. Algae characterization revealed that the presence of a particular potential problematic organism does not necessarily indicate that an episode is eminent. Identifying the types of algae that are found within water treatment plants has enabled in assessing the effectiveness of control strategies that are being implemented. Algae can be controlled to some extent by designing covered sedimentation basins and filters, adding algaecide coatings on walls, and applying algaecides like copper sulfate and potassium permanganate. Operational strategies that aid in algae control include scrubbing walls, cleaning with a power hose, and pre-oxidation using strong oxidants like chlorine.

IMPACT:

The results of this research will be directly relevant and applicable to water utilities as this study developed guidance and support information to assist water utilities in controlling algal growth within the water treatment plants.

MULTIMEDIA:

The companion CD-ROM contains a TAXA-photomicrograph library for algae enumeration.

RESEARCH PARTNERS:

• U.S. Environmental Protection Agency

• Veolia Water Indianapolis

PARTICIPANTS:

Seventy-six North American utilities participated in this project.