TREATMENT OF VEGETABLE WASH-WATER
TO PERMIT WATER RECYCLING
RICHARD G. ZYTNER AND KEITH WARRINER, UNIVERSITY OF GUELPH
Published January 2016
WHY DID WE DO THIS RESEARCH?
Standard approaches for treating wastewater derived from
fruit and vegetable processing operations require a high level
of expertise, have a large footprint and are commercially
unfeasible to most processors. The focus of the current project
was to identify affordable and commercially viable technologies
for treating wastewater. The types of fruit and vegetables are
diverse and as a result, wastewater characteristics also differ.
For example, processing root crops produces wastewater with
significantly different characteristics compared to leafy greens,
which also presents different challenges in treating the washwater to a standard where it can be disposed of or returned
back into processing. The objective of the current project was
to characterize different wastewaters and then provide the
appropriate treatment options.
WHAT DID WE DO?
Wash-water was collected from 13 different growers/processors (root crops, leafy greens and fruit) in Southwestern Ontario. All
samples were characterized for a suite of 20 water quality parameters, and then subjected to six different treatment technologies
(chemical or physical) to identify which treatment process worked best for different wastewater types.
WHAT DID WE FIND?
Wastewater characteristics were found to be dependent on the produce type and processing operations. The soils loading in spent
root crop water freshly harvested was higher than that of leafy greens, although variation did exist with respect to chemical oxygen
demand. With leafy greens, the solids content was low but colloidal (suspended evenly throughout the water with no settling) in
nature so there were challenges in removing the suspended solids. By knowing the water characteristics it is possible to identify
which crop wash-waters could benefit from chemical coagulants or more advanced technologies such as air flotation, centrifugation,
filtration or electro-coagulation.
WHAT ARE THE IMPLICATIONS FOR DECISION MAKERS?
Wastewater derived from fruit and vegetable processing operations has a diverse range of characteristics with respect to
concentration and types of solids encountered. Consequently no ‘one size fits all’ treatment technology exists and various
options have to be considered based on wastewater type. Nevertheless, this project provides information that allows producers
to identify the most appropriate technology to enhance the quality of wash-water and permit recycling.
The information is directly relevant to fruit and vegetable growers and processors, water treatment technology providers and
government policy makers. In order to use water resources more efficiently and protect the environment within a sustainable
system, a coordinated approach by all relevant parties is needed.
TO CONTACT THE RESEARCHER, EMAIL [email protected].
VISIT OUR REPORT LIBRARY AT WWW.CWN-RCE.CA