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).
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 (firstname.lastname@example.org)