Jeff Neemann

Use of Ozone for Disinfection and Taste and Odor Control at Proposed Membrane Facility

Zone 7 of Alameda County Flood Control and Water Conservation District, in coordination with Black & Veatch, conducted a 9-month pilot study to determine preliminary design parameters for a new water treatment plant (WTP). The pilot study was performed to verify the performance of membrane filters and to establish preliminary design parameters for the submerged membrane process, followed by ozonation and biological granular activated carbon filtration. The pilot testing was conducted using water from the Patterson Pass WTP reservoir. The process included coagulation with either ferric chloride or polyaluminum chloride, flocculation, sedimentation, membrane filtration, ozonation, and filtration using biological granular activated carbon (BAC). The goals of the study were as follows: 1. Determine the potential effectiveness of ozone and BAC for removing geosmin and MIB. 2. Determine the impacts of different levels of pathogen inactivation, i.e., 0.5-log Giardia and 2-log virus inactivation. 3. Monitor the formation of bromate under various conditions of ozone oxidation for different levels of pathogen inactivation as well as for taste and odor control, and evaluate bromate mitigation strategies, if necessary. The results of the study showed that the use of ozone achieved 2.0-log virus inactivation and 0.5-log Giardia inactivation. It also decreased the disinfection by-product formation and effectively controlled geosmin and removed a significant fraction of the MIB during a taste and odor event. Because the raw water bromide concentrations were low, bromate formation remained below the regulated level of 0.010 mg/L. However, in one instance, bromate mitigation was utilized by applying sulfuric acid to lower the pH to less than 7.1, which reduced bromate formation to less than 0.010 mg/L.

Synergistic Evaluation of Ozone and UV at the Coquitlam Source for Enhanced DBP Control and Cryptosporidium Inactivation

A study was performed for the GVRD to select the ozone dose that results in a higher UVT (UV Transmittance) and reduced DBP formation potential, at the most economical life cycle costs of ozone and UV treatment. The GVRD treats its Coquitlam source with ozone, to meet Giardia and virus inactivation requirements. Currently, the Coquitlam Facility does not meet Cryptosporidium inactivation requirements (3-log). Because the ozone dosage required for Cryptosporidium inactivation is cost prohibitive, UV treatment was selected to provide for adequate log inactivation. Based on pilot and full-scale test results, a model was developed to predict the ozone treated water UVT, which was applied to historical water quality data to evaluate life cycle costs of ozone and UV treatment. In addition, the dosage necessary for control of DBPs, the change in ozone decay rate with increases in pH, and the impact of three quenching chemicals on treated water UVT were evaluated.

Disinfecting the Coquitlam Water Supply: Ozone and UV Disinfection

The Greater Vancouver Water District (GVWD) is upgrading its unfiltered Coquitlam water treatment system to meet the updated Health Canada guidelines for providing 3-log reduction or inactivation of Cryptosporidium and Giardia. The existing Coquitlam system, which is designed for peak flows of 1200 ML/d (317 mgd), includes an ozonation facility providing 3 log Giardia inactivation, and a chlorination/corrosion control facility. To meet Health Canada guidelines, a UV disinfection facility will be constructed, which will provide 3-log inactivation of Cryptosporidium and Giardia, and the ozone dosage will be increased to reduce THM and HAA precursors as well as improve UV transmittance. This paper will focus on the conceptual design of the Coquitlam system and the preliminary bench-scale studies that were completed for GVWD as part of the predesign phase of the project.

Pipeline Contactor Design and Retrofit Fundamentals

Utilities with existing air system and aging ozone generating equipment are considering replacing generators capable of producing 1 to 2% ozone in air with those capable of producing ozone at 12% in oxygen. However, higher ozone weight percentage results in lower gas flow, issues with gas flow control, poorer mixing in the transfer cell of a conventional contactor, and oversized ozone destruct blowers, thereby requiring redesign of several subsystems within the ozone process. This document describes three retrofit experiences with installing (1) high concentration ozone generating equipment on a system formerly designed for air, (2) a sidestream injection system in an existing pipeline, and (3) a new pipeline contactor.