[Wayne Brown is seen standing inside in a large greenhouse. He speaks to the camera to introduce himself and the topic of the video. As the video continues, footage of woodchip biofilters and their construction process is shown, and Brown’s voiceover accompanies the footage]
WAYNE BROWN >> Hi, I'm Wayne Brown, Greenhouse Floriculture Specialist with the Ontario Government. Today, in this video, we’re going to look at management of post-production water using a woodchip biofilter. Woodchip biofilters remove nitrogen and phosphorus in recycled irrigation water through filtration and microbial activity.
The water treated through this system can be reused in the greenhouse or discharged as part of your Environmental Compliance Approval issued under the Ontario Water Resources Act. Biofilters can remove plant pathogens, 30 to 60% of the phosphorus, and up to 99% of the nitrogen from the water being treated.
The wood chip biofilter is usually placed between the greenhouse and the storage pond or cistern. It consists of a lined pit filled with woodchips and covered with a layer of pea-gravel. The liner selection depends on the soil permeability and the quality of the water being treated.
[Footage is shown of a large pit that will be converted into a biofilter]
WAYNE BROWN >> Sizing the biofilter depends on two criteria: the water volume to be managed and how long the water remains in the filter. Both of these factors are important to allow the microorganisms to effectively remove the nutrients and pathogens.
In the greenhouse post-production water is collected. It is distributed by gravity flow to the surface of the biofilter using a perforated PVC network.
[An animated diagram of a biofilter system removing phosphorus and nitrogen is shown]
WAYNE BROWN >> As water flows down through the gravel layer some of the phosphorus is removed. The wood chips become saturated creating a low oxygen environment. Under this condition, the microorganisms consume the nitrate-nitrogen in the water using the woodchips as a food source.
This biological process is called denitrification. This means that more nitrogen is removed with warmer temperatures and the longer the water remains in the biofilter.
[Still images are shown of a biofilter being lined with perforated pipe and filled with wood chips]
WAYNE BROWN >> At the bottom of the biofilter, water is collected in a large perforated pipe and is continually forced up and out of the filter as new water is added at the surface. The water leaving the biofilter is often low in oxygen due to the filter’s biological processes.
An aerator can be used to reintroduce oxygen into the storage pond or cistern. If the woodchips remain constantly saturated with water, the biofilter can be effective for at least five to ten years. It is a simple system with low maintenance costs for recycling water.
[Wayne Brown is seen standing in the original location in the greenhouse, speaking to the camera]
WAYNE BROWN >> For further information on woodchip biofilters, please visit our website or give us a call.
[TITLE: www.ontario.ca/greenhousecrops ; Call: 1-877-424-1300]