Delegates at the October '98 Western Canada Water & Wastewater Association conference heard expert presentations on one of the industry's most pressing issues ­ Cryptosporidium. The following are abstracts of four of these papers:

Since the Cryptosporidium outbreak in Milwaukee in the spring of 1993, things have changed for every water utility in North America, not least of all for the Milwaukee Water Works itself. Three major capital improvement projects are underway or have been completed. The raw water intake for the City's southernmost treatment plant has been moved an additional mile out into Lake Michigan. Forty rapid sand filters have been retrofitted with dual media. Ozone, generated from liquid oxygen, will soon be the primary disinfectant. Many plant improvements are also in progress, including changing from gaseous to liquid chlorine, and upgrading all chemical feed systems.

The data collected, and the flow of that data to interested parties, have improved. These daily log sheets are available in real time on the City computer network. Perhaps of most importance, a working group of Water Works, Health Department, Engineering, Regulators, and Sewerage District personnel was formed. Issues related to drinking water and public health are discussed at monthly meetings. An increased understanding of each group's strengths and personalities has lead to an enhanced ability to deal with both routine and high-pressure situations in a proactive way.

C. Lewis, City of Milwaukee, Water Works, Milwaukee, Wisconsin

Giardia lambia cysts.

A study was commissioned by the City of Camrose to identify water treatment plant improvements required to address CT, Giardia and Cryptosporidium treatment objectives. The study included a review of Giardia and Cryptosporidium potential, filtration performance and disinfection system effectiveness. A tracer study, an on-line particle monitoring program and a year long Giardia/Cryptosporidium sampling program were initiated as part of the study.

Preliminary findings indicated a risk of Giardia and Cryptosporidium contamination without ongoing process optimization and vigilant operation. Giardia and Cryptosporidium oocyst concentrations as high as 540 cysts/100L and 790 oocysts/100L respectively have been measured in the raw water source. Despite these high levels, the plant did perform well. Turbidity values in compliance with the 1997 AEP (Alberta Environmental Protection) Draft Guidelines and low particle counts were achieved. Microscopic analysis of Giardia cysts indicate more than 2.5 log reduction of Giardia cysts was achieved by the treatment plant.

The disinfection system was assessed to be marginally adequate as an additional barrier against Giardia, but incapable of providing inactivation of Cryptosporidium oocysts. Measures for enhancing disinfection system and particle removal effectiveness have been identified as a result of the preliminary work. This paper reviewed the study work undertaken, the findings and planned follow-up as a result of the proactive measures taken by Camrose to address the latest water quality objectives.

G. Drachenberg and S. Suthaker, Associated Engineering Alberta Ltd.; G. Finch, University of Alberta; E. Hargesheimer, City of Calgary

This paper discussed the implementation of on-line particle counting at Edmonton's two water treatment plants. In the last several years, the use of on-line particle counters has become more common in the water treatment industry. Though there are no established guidelines or limits regarding the use of particle counters, their increased sensitivity allows the performance of the plant to be monitored more accurately.

The implementation of particle counting involved several stages: the decision to purchase, the selection, the installation and the operation. After almost a year of trials with different units, over 30 particle counters were installed at the two plants and integrated with the plant SCADA system. In addition to placing particle counters on the effluent for each filter, they were placed at each stage in the operation.

After summarizing the implementation of particle counting, the authors presented some of the data that has been collected over the last year. This included figures showing particle count data from different stages within the plant and the operational interim guidelines that were developed. On-line particle counting has been successfully implemented at Edmonton's water treatment plants. Though it took over a year from beginning to end, informed decision-making contributed to the successful outcome.

S. Thomas, R. Shariff, T. Lee, R. Welz and L. Gammie, Aqualta

Cryptosporidium parvum oocysts.

Recent outbreaks of cryptosporidiosis in several cities in North America have sparked an increased level of interest in this coccidian protozoan. In 1996, boil water advisories were issued for the BC cities of Cranbrook and Kelowna that were affected by this disease. During the spring and summer of 1997, Reid Crowther and Partners Ltd. completed assessments of the risk of exposure to Cryptosporidium for the Greater Vancouver Regional District (GVRD) and the Greater Nanaimo Regional District (GNRD) watersheds.

The projects were designed to help the districts assess the risks posed by this parasite, to identify appropriate removal/inactivation goals and to determine whether treatment facilities should be designed for Cryptosporidium removal/inactivation.

Each watershed was assessed for factors known to increase their exposure to Cryptosporidium and comparisons were then drawn to previous outbreaks of cryptosporidiosis in Canada, the US and the UK. This process included:

• Reviewing reported data on past outbreaks of cryptosporidiosis worldwide and identifying risk factors that may have contributed to these outbreaks.
• Reviewing "reach watershed" and identifying potential areas of exposure.
• Reviewing current watershed management practices.
• Identifying which, and to what degree, risk factors were prevalent in the studied watersheds.
• Analyzing available Giardia and Cryptosporidium sampling data.
• Providing an overview of regulatory issues related to Cryptosporidium.
• Developing appropriate inactivation/removal goals.

The final reports concluded that improvements to watershed management practices could help to reduce risk; however, the risk of an outbreak of cryptosporidiosis in both the GVRD and the GNRD's service areas was low. It was determined that specific inactivation/removal goals for Cryptosporidium were not warranted at this time.

A. Gartner, Reid Crowther & Partners

Photos courtesy Dr. G.R. Finch