Largest membrane

ZENON Selected to Supply World's Largest Membrane Bioreactor

Order valued at $30 million

OAKVILLE, Ontario, March 16, 2005 - ZENON Environmental Inc. announced the company has been selected to supply King County in the State of Washington with the largest membrane bioreactor in the world. The ZeeWeed MBR (membrane bioreactor) will treat an average day flow of approximately 144,000 cubic meters of municipal sewage or 38 million gallons per day (MGD) with peak flows up to 204,000 cubic meters or 54 MGD, serving over 100,000 households. In addition, the company received an order for a second smaller plant, which results in a total order value to ZENON of $30 million.

Design of the greenfield plants is currently underway with construction expected to begin in 2006 and completion scheduled for 2010 for the larger Brightwater plant and 2007 for the smaller Carnation plant. ZENON expects to receive the final purchase order by the end of May 2005.

The new Brightwater Wastewater Treatment Plant will be the first membrane plant owned by King County, as the existing two sewage treatment plants do not use membrane technology.

"We selected ZENON's membrane bioreactor system for our new plant because of its performance in providing consistently higher water quality," said Ron Sims, King County Executive. "As we are planning to discharge the treated wastewater into Puget Sound, protecting our marine life as well as our communities was a primary concern. We are confident that the ZeeWeed MBR technology will help us to preserve our surrounding environment."

According to Andrew Benedek, ZENON Chairman and CEO, this order demonstrates the competitiveness of membrane bioreactor systems and their ability to treat wastewater for plants of any size. Once completed, the Brightwater Wastewater Treatment Plant will represent a new benchmark in the industry and become a significant reference site for the company.

King County's Wastewater Treatment Division serves 18 cities, 16 local sewer agencies and more than 1.4 million residents in King, Snohomish and Pierce counties.

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.