Managing wash water to protect your farm stream

From ONvegetables in The Grower, February 2014

By Deanna Nemeth, Nutrient Management Program Lead (Horticulture)/ OMAF and MRA

Fruit and vegetable producers have been looking for low cost methods to manage wash waters. When you are washing fruit and vegetables, the physical characteristics of the washwater varies depending on your operation. Characteristics can range from potable water used to rinse fruit and vegetables prior to packaging; to washwater high in soil sediments from rinsing soil from root vegetables or peel from scrubbing vegetable before packaging and marketing. Both the liquid and solid waste streams must be managed to protect water quality in and around the farm.

Low cost management options for separating the solid and liquid from wash water include the use of aerated ponds or facultative ponds to settle solids out, constructed wetlands, screens or fiber filters to remove sediment, and settling basins. Separated solids can be composted in properly turned and aerated windrows or solids can be transferred to an anaerobic treatment system for use in biogas production. A low cost option for managing separated solids can be land application and incorporation into the soil under the Nutrient Management Act.

Separated liquid wash-water can be land applied by irrigation onto farm land; however, food safety consideration before irrigating onto fresh market crops is important. Irrigation water quality standards for pathogens are Escherichia coli: 100 bacteria per 100 mL water, and Total coliforms: 1, 000 bacteria per 100 mL water, according to Environment Canada, 2002, Canadian Water Quality Guidelines for the Protection of Agricultural Water Uses. Keeping water test records are good agriculture practices and an important part of an on-farm food safety planning. For more information on irrigation standards, see OMAF and MRA Factsheet, Improving On-Farm Food Safety Through Good Irrigation Practices, Order no. 10-1037.

It is important to understand that it is an offence under the Ontario Water Resource Act to have wastewater discharge negatively impact surface or groundwater. Wastewaters, although not high in any particular contaminant, can still negatively impact stream water quality if the water is has high suspended solids or biological oxygen demand (BOD). The higher the biological oxygen demand of the material the less oxygen that is available in the water for fish and other organisms to survive.

Ensuring waste materials are managed is part of a good business plan and will help protect water quality around your farm.

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