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Nutrient and contaminant removal

Managing solution discharge

The most common method of dealing with salinity buildup in the nutrient solution is occasional discharge of the solution. If nutrient solution is going to be discharged, management of the released wastewater must be taken into consideration. Often, especially with increasingly stringent controls on effluent water quality, this water will need to be filtered. This is mainly because effluent water produced by greenhouses and nurseries tends to contain nutrient concentrations far higher than that of the water of the surrounding environment. The most problematic of these nutrients are nitrogen and phosphorus which, if not controlled, can lead to increased algal growth in surface waters. These algal blooms deplete oxygen in the water, killing off fish and other organisms (a condition referred to as “eutrophication”). In addition, effluent water will likely contain traces of pesticides/herbicides and may contain toxic by-products produced by certain chemical pathogen control methods. Pesticides in the concentrations found in greenhouse water can be harmful to a variety of aquatic organisms (Kabashima et al., 2003). As such, effluent should undergo some sort of treatment to remove these compounds in order to meet regulatory guidelines and maximize environmental responsibility.

Even if effluent water is being released to holding ponds for eventual recirculation, the water may still need to be treated before entering the pond. Without nutrient removal, the amounts of nitrogen and phosphorus in the effluent water can lead to algal blooms in the holding pond, which will increase water pH and require recirculated water to be filtered and acidified before it can be re-used (Headley et al., 2001). As well, chemicals should be removed before water is recirculated to prevent accumulation to toxic levels.

The flow chart below provides a breakdown of methods available for removing nutrients and other contaminants from water prior to disposal (click for more information).

Link Link Bioreactors Fluidized bed reactor Crop Application Constructed Wetlands Vegetated Buffers

For Na, Cl and SO4 removal from recirculated greenhouse irrigation water, please visit:

This work was supported in part by the Canadian Ornamental Horticulture Research and Innovation Cluster and Canadian Ornamental Horticulture Alliance

For more infomation please contact Dr. Zheng (yzheng@uoguelph.ca)

link to CESRF website