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A comprehensive survey of plant pathogen populations (measured by DNA Multiscans) in irrigation water leachate and/or runoff from the range of Ontario flower and vegetable greenhouses and container nurseries was conducted to help assess the level of risk involved in operations switching to recirculating systems. The ability of several bioremediation technologies to remove plant pathogens from recycled irrigation water (e.g. constructed wetlands, woodchip biofilters) was evaluated as well as the effectiveness of current plant pathogen disinfection systems.
A biweekly sampling program to determine the water quality of greenhouse process water (feed, leach and collection pond water) was conducted at 7 vegetable and 8 flower greenhouse operations. As well, a water use and management paper survey across a wider range of operations was conducted to determine the quantity of water being used for irrigation and the degree to which unused irrigation water (leach) is being captured and reused, and issues surrounding water use/reuse management. A total of 9 vegetable growers completed surveys (3 tomato, 2 cucumber, 3 pepper, and 1 tomato and pepper operations), and 27 flower operators were surveyed, with approximately even representation from the five major production categories (cut recirculating, cut open, potted plant recirculating, potted plant open, and cut flowers grown in soil).
Five technologies were evaluated for their effectiveness at removing nutrients, non-nutrient components, and plant pathogens from irrigation runoff or leachate: a full scale constructed wetland system recently installed at a container nursery, and four pilot scale systems constructed at flower greenhouse: two denitrification woodchip bioreactors combined with phosphorus removal units, Phytolinks™ (floating wetlands), IrrigroTM irrigation system, and an engineered hollow fibre filter system (Zeeweed)Evaluation of innovative water treatment technologies for reuse of nutrient solutions in the horticulture industry
An in-field evaluation of the ability of 12 established denitrification woodchip bioreactors and constructed wetlands to remove plant pathogens and/or human enteric pathogen indicator organisms from horticultural and agricultural wastewaters and runoff was conducted. Removal effectiveness was correlated with parameters affecting performance (e.g. media, residence time, temperature, oxygen, pH, depth). The information supports the design of on-site systems that will consistently remove plant and enteric pathogens as well as nutrients from agricultural runoff and wastewaters in order to facilitate its reuse and/or protect surface and ground water resources from contamination
This study was an extension of the WRAMI project for second season to include early spring and late fall monitoring (cool temperatures) at the edge of field sites, modified hydraulic retention times and/or nutrient characteristics of waste streams to the bioreactors at the greenhouse sites, and the performance of a newly constructed wetland system treating recycled leachate water from a greenhouse, where the most significant water treatment requirements occur over the winter period. Removal effectiveness was correlated with parameters affecting performance (e.g. design, media, residence time/flow rate, temperature, oxygen, depth) in order to support the design of on- and off-site systems that will consistently remove plant and enteric pathogens as well as nutrients from agricultural runoff and wastewaters.
Field studies of stormwater pond dynamics in response to storm events at horticultural operations were carried out to determine the critical points at which farmers must manage their collection ponds to protect the environment. For most horticultural greenhouse operations, stormwater ponds essentially collect rainwater from the greenhouse roofs, and may collect subsurface drainage water from adjacent land or the greenhouse production facility. Continuous as well as strategic monitoring was carried out at three floriculture greenhouse sites over the 2014 season, collecting information on volumes, overflows, meteorological data, and composition of pond water and stormwater overflows. This project is the first phase in developing Best Management Practices for producers to size, design, and monitor their stormwater management systems to adapt to changes in size, intensity, frequency, and variability of growing season storm events predicted by current climate change models. The development of a coherent management and sampling strategy is of value to farmers, who are looking at whether their ponds are designed and operating properly, and are seeking to comply with environmental ministry requirements.
Rapid and standard 3M Petrifilm methods were compared (Aerobic Plate Count for bacteria (AC), Rapid Yeast and Mold (RYM), and E.coli and Total Coliform (Ec/TC)), as well as diluents and incubation times and temperatures. Other methods tested included LaMotte BioPaddles, Biosan SaniCheck YM, ColiTag and AgDia strips to select the ‘best’ method for on-site monitoring. Periodically, samples were submitted for DNA Multiscan analysis for plant pathogens to obtain correlations between this method and the 3M TY&M method being used as an ‘indicator’ test for the presence and level of fungal plant pathogen populations. A 2 year data base of water quality over different production systems, seasons and treatment systems was developed. Grower protocols for sampling and monitoring methods were developed and refined in cooperation with growers and their designated personnel. Training of owner/growers and/or designated personnel was carried out at each participating operation. The in-house data generated was compared to the on-going monitoring program in order to assess the practicality of the methods in-house and get feedback from the individual cooperators.
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