Advantage Good Agricultural
4.2 Water Treatment
poor quality water is used without being treated first or water quality is not
maintained during use (such as with dump tanks), contaminants can be passed to
livestock, poultry and food. Improperly treated water can also be a source of
This Good Agricultural Practice applies to:
with poor water quality.
What needs to
To protect the safety of food, livestock or poultry, treat water
as required to maintain its quality or use an alternative source.
If needed, an example
of a written practice for continuous chlorination water treatment can be found
in the Training and Support Tools section (refer to Sample D).
to do it
Choose the Right Method of Water Treatment
Make sure the
type of water treatment chosen is the right one for the particular situation.
Consult water quality professionals for more information on water treatment options.
number of water treatment methods are available and can be used alone or in combination
with several other treatment processes.
Physical water treatment
- Filtration is the process of treating water contaminated
with substances such as dirt or organic matter. For example, sand filters will
remove large particles from the water. Granular activated carbon (GAC) filters,
commonly known as charcoal filters, will filter particulate matter from the water
and will also adsorb (soak up) dissolved organic matter and other contaminants.
Membrane filtration is the most effective method for removing parasites such as
Giardia and Cryptosporidium.
- Ultraviolet (UV) light is
a non-chemical method for killing micro-organisms such as bacteria, viruses (not
retroviruses and rotaviruses), spores and cysts.
Ask your chemical or water treatment supplier for approved
water treatment aids, or refer to:
Listing of Accepted Construction Materials, Packaging Materials and Non-Food Chemical
Products" (Canadian Food Inspection Agency)
- Coagulating water is the process of adding chemicals to water
to make dissolved or suspended particles bind together and settle out. This process
reduces the level of organic compounds, dissolved phosphorus, colour, iron and
- Chlorination is the process of adding
chlorine to water to kill bacteria and viruses but not parasites such as Giardia
and Cryptosporidium. Two types of water chlorination-shock chlorination and continuous
chlorination-are used in water treatment. Shock chlorination (used for treatment
of wells) is the process of flushing a well and water system with a chlorine solution.
Continuous chlorination (used for treating dump tank water) is a process of adding
chlorine to water continuously to maintain a certain level of free chlorine in
the water at all times.
- Ozonation is the process of adding
ozone to water to kill bacteria, viruses, parasites, mould and yeast spores. Ozone
completely breaks down in water.
- Hydrogen peroxide is
a chemical added to water to kill bacteria, viruses and fungi. It is not as effective
Biological water treatment
Biological water treatment is ideally suited to treat water that is highly
coloured and has high dissolved organic carbon (DOC) and nutrient levels. It uses
a natural ecosystem that removes colour and dissolved organic matter, but not
Monitor and Maintain Water Quality
At pre-determined frequencies, water should be tested to ensure quality:
- Treating with shock chlorination
Two to five days after shock
treatment, sample the water for total coliform and E. coli to confirm that water
is safe to use. Continue to regularly monitor your water source for quality.
with continuous chlorination
A continuous chlorination method (e.g. dump tank)
must be regularly monitored at pre-determined intervals for free chlorine and
pH levels (e.g. testing water hourly). The recommended chlorine and pH levels
for a produce dump tank are 100 to 150 ppm and 6.0 to 7.5, respectively.
An alternative method to regular monitoring of chlorine levels is using an oxidative
reduction potential system.
- All other water treatments
a water sample and test for coliform bacteria and E. coli after the treatment
method or system has been used or installed to ensure it is working effectively.
Records to keep
- Water Treatment Record.
We have provided a record
template for your use in the Training and Support Tools section. A printable
version is also available. Or keep your own record that includes:
- Date and/or time of treatment
- Chemical used, including amount
- Monitoring result (e.g. chlorine level, pH)
or initial of worker performing treatment/testing
- Lab water
quality test results
Contact Centre: 1-877-424-1300
Ontario Ministry of the Environment Public
Information Centre: 1-800-565-4923
Ontario Ministry of Health and Long-Term
Care INFOline: 1-866-532-3161
Did you know?
itself can also present a source of contamination if it is incorrectly performed.
For example, if the chemical residue that remains in the treated water is over
a certain limit, it becomes a food safety hazard.
If you need an audit
prepared for the auditor to review:
- Water Treatment Records
water quality test results
Laws and regulations that apply
are few laws that impact on food safety regulating the treatment of water to be
used in agricultural production. Generally, these requirements are laid out in
laws regarding the processing of meat, fish and other food products, which are
outside the scope of this document.
The Safe Drinking Water Act,
2002 and Regulations, including the Ontario Drinking Water Quality Standards,
O. Reg. 169/03, set out requirements for water treatment. Approved
disinfection methods are listed in "Procedure for Disinfection of Drinking
Water in Ontario," 2nd Revision, June 14, 2006, adopted by reference by Ontario
Reg. 170/03 under the Safe Drinking Water Act. Check with your local
health inspector for recommended or required water treatment procedures.
Did you know?
In the fall of 1998, over 500 people across the United
States and Canada became sick from eating contaminated chopped, uncooked parsley.
The source of contamination was traced to a lack of water treatment to maintain
water quality in a hydrocooler on the farm. The municipal water that supplied
the hydrocooler was used to immediately chill the parsley after harvest; however,
the water was recycled and no water treatment aid was added to maintain the water
quality. Because the water was recirculated and untreated, pathogenic bacteria
that may have been on some of the parsley were now washed off into the water and
survived in the absence of a sanitizer (e.g. chlorine). The recirculation of the
now-contaminated water caused many more loads of parsley to become contaminated.
to 5.1 Cleaning and Sanitizing