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(SAN DIEGO) May 11, 2005 – LAWFUEL – The Law News Network – DLA Piper…

(SAN DIEGO) May 11, 2005 – LAWFUEL – The Law News Network – DLA Piper Rudnick Gray Cary US LLP successfully represented Oakville, Ontario-based Zenon Environmental Inc. (TSX: ZEN and ZEN.NV.A; OTC: ZNEVF and ZNEAF) in a patent dispute before the United States District Court for the Southern District of California in San Diego. On May 5, the court ruled that United States Patent No. 6,620,319 (the ‘319 patent), the subject of a patent infringement suit brought by ZENON against U.S. Filter, continues to be presumed valid.

On October 8, 2003 ZENON filed a patent infringement action against U.S. Filter complaining of infringement of three ZENON owned patents relating to water treatment, most importantly, the ‘319 patent relating to membrane module construction. In the course of these proceedings, U.S. Filter among other things, alleged the invalidity of the ‘319 patent, which, if successful, would have affected other patents in the same patent family. The parties recently agreed to a bench trial on the issue of the validity of the ‘319 patent. The trial was conducted in San Diego on April 27-28, 2005. A ruling from the court was delivered on May 5, 2005 in which the court ruled in favor of ZENON strongly refuting all of defendant U.S. Filter’s contentions.

ZENON CEO Andrew Benedek stated that “The decision clears perhaps the single most significant hurdle in our path toward proving our claims and our request for an injunction to stop infringement by U.S. Filter. We respect the intellectual property rights of others and expect our principles to be reciprocated. We have a responsibility to our shareholders to press forward and prevent continued misappropriation of our rights. Furthermore, the court’s decision is extremely clear and well reasoned.”

While the infringement of the ‘319 patent is no longer an immediate issue due to an adverse ruling made in November of 2004 (which ZENON will appeal), ZENON filed a further patent infringement action against U.S. Filter on January 11, 2005, on its United States Patent No. 6,682,652 (the ‘652 patent) which is part of the same family as the ‘319 patent. The ‘652 patent is now the primary focus of ZENON’s infringement action and the merits of that case are greatly strengthened on the basis of this ruling. A full trial on the ‘652 patent is expected in 2006.

ZENON is gratified and vindicated by the decision and continues to be confident that issues of infringement will ultimately be resolved in its favor.

About ZENON
ZENON is a world leader in providing advanced membrane products and services for water purification, wastewater treatment and water reuse to municipalities and industries worldwide.

In 2004, Corporate Knights, a business publication addressing corporate responsibility, ranked ZENON Environmental Canada’s top Corporate Citizen, for the second time. Canada’s Top 100 Employers ranked ZENON in their top 100 list for the last five years. An S&P/TSX Composite company, ZENON Environmental Inc. trades on the Toronto Stock Exchange under the symbols ZEN and ZEN.NV.A; and on the OTC under the symbols ZNEVF and ZNEAF. Additional information is available at ZENON’s web site www.ZENON.com.

About DLA Piper Rudnick Gray Cary US LLP
DLA Piper Rudnick Gray Cary US LLP is a business law firm of 1,350 lawyers in offices throughout the U.S., whose core practices are real estate, corporate and securities, litigation, intellectual property and government affairs. Worldwide, DLA Piper Rudnick Gray Cary has 2,800 lawyers in 20 offices in 18 countries, including the United Kingdom, mainland Europe and Asia, offering leading practices in commercial, corporate and finance, human resources, litigation, real estate, regulatory and legislative, and technology, media and communications.

With more than 400 intellectual property lawyers globally and 220 IP lawyers in the U.S., our group is among the largest in the world and one of the five largest IP practices in the U.S., according to the 2004 survey by Managing Intellectual Property magazine. The U.S. patent litigation team, which includes more than 80 lawyers, has handled more than 150 cases in U.S. District Courts and the ITC over the past three years. More than 50 of the firm’s lawyers have advanced scientific degrees and more than 60 attorneys are admitted to practice before the U.S. Patent and Trade Office, allowing DLA Piper to offer clients with specific technologies comprehensive patent enforcement, IP counsel and defense services.

More information about DLA Piper is available at www.dlapiper.com.

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ZENON ENVIRONMENTAL INC. CONTACTS:
Andrew Benedek, Chairman and CEO, 905.465.3030
Nazeli Clausen, Corporate Communications and Investor Relations, 905.465.3030 (Ext. 3055)

DLA PIPER CONTACTS:
John Allcock, Co-Chair, Technology, Media and Communication practice group, DLA Piper, 619.699.2828 John Kinton, Attorney, DLA Piper, 619.699.2718 Patrick Bustamante, Media Contact, DLA Piper, 650.833.2388 Dan Cahill, Media Contact, GreenTarget, .415.552.3999

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