Background

Envron Environmental has utilized Ozone treatment systems for odor control applications in commercial hog barns, (air and manure) poultry barns, mushroom composting facilities, vehicle odor control and residential odor remediation applications. Envron's design and production capabilities include using applied scientific research through our Chemical Engineering and Analytical Chemistry capabilities and practical experience through our Ozone system engineering capabilities.

Greenwood Mushroom Farm

Envron has co-operated with the Canadian Mushroom Growers Association on a project at Greenwood Mushroom farm to control odors from three Greenwood composting bunkers. Equipment was sized for Greenwood based on a previous study by Envron and verified by the B.C. Ministry of Agriculture for a mushroom composting facility located in Surrey.

The Greenwood odor control equipment is integrated into the composting bunkers using a ventilation system. When compost is present in the bunker, the Ozone system is started. The ventilation system draws air from the bunker and Ozone is pumped into the exhaust through a mixing/retention system.

The mixing/retention system is designed to provide maximum mixing of the compost exhaust and Ozone so that both gas trains are thoroughly entrained. The Ozone/exhaust mixture must pass through a three-phase mixing/destruct process.

This mixing/destruct process includes mixing of the Ozone/compost exhaust through a fan/blower system prior to further mixing in a destruct tank where the air is slowed significantly. From the initial destruct tank, the air is routed through a manifold into a second destruct tank where the mixture is then exhausted to atmosphere.

Results

A study was engaged by the Canadian Mushroom Growers Association using a local firm. Based on the results of the study and Envron's installation that was tested by the B.C. Ministry of Agriculture in Surrey, B.C. and based on on-site observation of the system, the system is accomplishing the objective of odor control of the compost bunkers. When the Ozone system is not engaged, the full composting odor is noticed coming through the stack. When the Ozone system is engaged, the stack has a noticeable Ozone smell.

This is exactly the situation that was encountered at the Surrey, B.C. mushroom composting facility when we worked with the B.C. Ministry of Agriculture and the University of British Columbia to quantify odor control using Ozone and mushroom compost. There was a residual Ozone smell coming from the destruct stack when tests were conducted. The results of that study with the odor panel showed that the untreated samples required dilution rates of between 1701-3043, which is typical of odorous substances. The Ozone treated samples dilution rates were between 209-264, which is typical of non-odorous substances. As well, the treated samples actually smelled like Ozone which has an almost antiseptic or sanitary smell.

It is this residual Ozone smell at the Greenwood site that gives us assurance that the Ozone system is accomplishing its objective. When Envron initially designed the system, the objective was to provide a quantified amount of mixing time at maximum exhaust flow levels and to achieve a residual concentration of Ozone. The residual Ozone concentration indicates that the entrainment of the gases is complete and that not all the Ozone has been used up in the mixing/destruct process. This indicates that the Ozone will continue to travel with the exhaust flow and provide further oxidation as the dilution of the gases continues, further reducing any odors on the company property.