Ecological Engineering Systems for Nutrient Reduction and Recovery from Agricultural Wastewater Sources

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Nutrient migration from agricultural catchments to surface water bodies and to groundwater aquifers present a significant threat to public health and to the environment as well as representing high economic costs in terms of drinking water treatment and loss of recreational potential. A report published by the International Joint Commission (IJC, 2014) states that agricultural runoff can contribute significant nutrient loads to watercourses and stipulates that agricultural operations are one of the major contributors of phosphorus loads responsible for the recent severity of algal blooms in Lake Erie. The report describes agricultural systems having evolved from being net phosphorus sinks to where there is now net phosphorus being exported from most farms. Heightened levels of phosphorus have been recorded in lakes and rivers across Canada and have resulted in the development of cyanobacterial blooms, which result in toxins being released into surface water bodies. This research program addresses N and P reduction and recovery from agricultural wastewaters and consists of four inter-related objectives. The first objective is to develop a technology to capture and recover dissolved P as a component to constructed wetland technology. The hypothesis is that the use of a source of slow-release cations (i.e. Ca2+, Mg2+, Fe2+/3+, Al3+) coupled with either a sedimentation pond or filtration media and periodic desludging/removal followed by land application can close the loop on P in agricultural drainage basins. Technology development will evolve from lab to pilot to field scale. The second objective is to characterize N and P loading and fractioning (total, particulate, dissolved, N cycling) at cooperator sites in Eastern Ontario with fully instrumented constructed wetland systems representing typical agricultural wastewaters: cropping system drainage, beef production runoff and dairy production washwaters. The third objective is to study N/P attenuation mechanisms and model removal rates in the constructed wetland systems treating agricultural wastewaters. The final objective is to apply, validate and adapt the P capture technology at the existing cooperator sites. The three field sites are fully instrumented for flow (v-notch weirs with depth loggers, pump runtime loggers) and water quality sampling (solar powered composite samplers, groundwater piezometers, zero-tension lysimeters). All water quality analytical work will be conducted at the University of Ottawa's environmental engineering laboratories following Standard Methods. HQP training is central to the research program, with 2 Ph.D, 6 M.A.Sc., and several M.Eng and Undergraduate students implicated in the development of the P-recovery technology, wetland characterization and modelling activities. Strong collaboration with government and industry provides a strong platform for technology transfer.