Recovery of Wastewater from the Treatment of Organic Waste to Irrigate a Short-rotation Willow Plantation

Wastewater from Rocher-Percé RCM’s composting site monopolizes some of the processing capacity of the municipal wastewater treatment plant (WWTP), reducing the RCM’s capacity to treat residential and industrial wastewater. This application is for a pilot project to use some of this excess wastewater to irrigate a willow plantation near the compost site. The proposed site is a vacant lot on a former landfill located one kilometer from the composting site. The area of the site will be 4 hectares to begin with. A drip irrigation system will deliver wastewater that has been pumping from the storage basin and filtered. Wastewater over and above the pilot project’s processing capacity will continue to be channeled to the WWTP for treatment. An aeration sewage system will be set up in the collection basin to promote volatilization of ammonia nitrogen, reducing the wastewater’s nitrogen load. Risk monitoring (of nitrogen in nitrate form, for example) will be carried out by measuring levels over time using piezometers installed around and inside the pilot plot. Although the irrigation system will be automated, startup will be operated by staff to avoid days of heavy rain. Filters and other measures will be installed to prevent or reduce the risk of clogging caused by water stagnation and breakage caused by winter frost when the system is off. The applicant plans to plant the willows in the summer of 2017 and follow up for 18 months. If the result is positive and conditions of use acceptable (area required, operating methods needed to manage the water), an expansion will be planned to manage all the water generated by the composting and the dehydration of septic sludge, by using it for irrigation. This pilot project is consistent with the territory’s waste management plan and fits especially well with the supplementary regional objectives of "reducing economic impacts of waste management" and "reducing environmental impacts of waste management". A willow tree has a highly-developed root system allowing it to absorb large amounts of water while degrading waterborne pollutants by biological and physico-chemical means. A willow’s absorption capacity is increased and renewed when it is grown in short rotations (frequent harvests). The willow stems are harvested every two to four years to provide biomass for use in other applications such as heating. By the end of the pilot project, about 6 000 m3 of wastewater will have been treated and the quality of the willow-treated water will have reached regulatory standards. Greenhouse gas emissions will have dropped from ten to five tonnes of CO2 equivalent due to reduced truck transportation to the WWTP. The pilot project will create knowledge about the treatment of other types of waste and the use of willow biomass for other purposes, such as providing energy to heat buildings. (Project description from original funding application)