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C oagulation is the process of adding chem icals to water to

m ake dissolved and suspended particles bind together,

form ing larger particles that will settle out of the water as a

sludge. C oagulation is a safe and effective m ethod of

water treatm ent, com m only used in m unicipal drinking

water treatm ent. It is suitable for treating the organic-rich

water often found in Prairie surface water sources, such as

dugouts.

C oagulation can be a sim ple and inexpensive way to

im prove the quality of farm water. This m ay have benefits

for:

household use (including im proved operation of

com m ercial treatm ent system s);

m ixing of farm chem icals;

livestock watering; or

food processing.

C oagulation can im prove the quality of water by:

reducing the dissolved organic carbon (D O C )

concentration by approxim ately 60% . This im proves

taste and odour, m akes the water safer for chlorination,

and m akes the w ater easier to treat for dom estic

purposes. DO C rem oval also im proves water quality

for agricultural uses, such as livestock w atering;

reducing the num ber of suspended particles in the

water, which m akes the water easier to treat for other

purposes such as dom estic use and provides a high

quality of water for farm chem ical spraying;

reducing colour by over 80% , which m akes the water

m ore aesthetically appealing;

reducing the dissolved phosphate concentrations by

approxim ately 90% , which helps reduce algae bloom s,

including toxic blue-green algae; and

rem oving iron and m anganese which im proves the

taste, elim inates stains on laundry and fixtures, andelim inates coatings on pipes.

C oagulation can be used to treat water from rivers, lakes or

reservoirs. C oagulation can be perform ed directly in a

dugout, in a coagulation cell, or with a com m ercial

coagulation system . A coagulation cell is a sm all,

ENH-91-2000-04-rev1

Agriculture andAgri-Food Canada

Agriculture etAgroalimentaire Canada

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Typical Benefits of Coagulation

0

20

40

60

80

100

DOC Colour Phosphate Turbidity

PercentofCompoundR

emaining

Before

After

constructed reservoir that is used to store and treat water

about twice per year; it is sized to allow use of all the

treated water. A com m ercial coagulation system uses a

tank for treating water on a daily basis.

D ugout coagulationis recom m ended as a tem porary

solution to water quality problem s in dugouts. Because

poor quality surface runoff flows into the dugout, repeated

applications are required. The large volum e of dugouts

m eans high chem ical costs, usually ranging between $200

and $800 per treatm ent. If the dugout is not carefully

m anaged, repeated treatm ents could cause elevated

chem ical residuals.

A coagulation cell has an inverted pyram id shape. C ells

for household water supplies are designed to hold

approxim ately 250,000 litres or 55,000 gallons (equivalent

to about six m onths of dom estic water needs). O f course,

larger cells can be built for other agricultural uses.

A bank is built around the cell to prevent contam ination

from any surface runoff. A n unlined coagulation cell

without plum bing will cost about $1,500. A lined cell

com plete w ith plum bing will cost about $6,000. H ousehold

water cells are treated once in the spring and once in the

fall at a cost of under $100 per treatm ent.

The com m ercial coagulation system uses a batch

coagulation process. W ater is treated every three hours

until the storage tank is full. This system costs about

$6,000 and is easy to operate, but requires the use of

special chem icals

Alum inum sulphate and ferric chloride are the prim ary

coagulant chem icals used for drinking water treatm ent.

Powdered activated carbon (PAC ), a coagulation aid, can

be used in coagulation cells to enhance rem oval of organic

com pounds that cause taste and odor problem s.

Polyalum inum chloride (or other polym erized chem icals) are

used for specific applications such as those required by

com m ercial coagulation system s.

Each coagulant chem ical has strengths and weaknesses.

The m ost im portant considerations in choosing a chem ical

are the treatm ent m ethod, desired water quality and the

expected water use.

See C hem icals for O n-Farm C oagulationpublication for

further details.

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W hen treating a dugout or a cell, the following steps m ust

be taken:

1. C alculate the volum e of water to be treated.

2. C om plete a beaker test on a one litre sam ple to

determ ine the chem ical dosage.

3. C alculate the total am ount of coagulation chem ical to

be used.

4. M ix the w ater adequately.

5. Add the chem ical and continue m ixing the w ater for a

sufficient tim e.

6. M onitor the pH and alkalinity to prevent overdosing.

7. Stop m ixing and allow the water to settle.

W hen using a com m ercial coagulation system , follow the

operation and m aintenance procedures recom m ended by

the m anufacturer. Treated water should be tested at least

twice per year.

See H ow to C oagulate Your D ugout or C ellpublication

for further details.

A sm all volum e of sludge is produced after coagulation

treatm ent. In a dugout, the sludge can be left at the bottom

of the dugout.

In a coagulation cell, the sludge should be rem oved

annually. Fall is the best tim e to rem ove sludge. The

sludge can be safely applied on an adjacent field or

pasture. Studies have shown no crop yield reduction or

detectable residues in the crop following heavy sludge

application rates.

C onditions that lim it the effectiveness of coagulationtreatm ent, or deteriorate water quality after treatm ent include

the following:

anim al, fish or other aquatic activity in a coagulated

dugout or cell;

presence of an algae bloom ;

inadequate or excessive dosage;

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inadequate or excessive alkalinity; and

very poor raw water quality.

By itself, coagulation treatm ent does not m ake water safe for

drinking. It is a treatm ent process that is very effective when

m anaged properly, and used in conjunction with otherprocesses w hen higher quality water is desired.

W ater quality affects the agri-food sector in num erous ways.

Poor water quality can:

im pact livestock production, pesticide application, and

dom estic use;

affect anim al health and weight gain;

cause w atering system s to fail;

reduce herbicide perform ance and plug spray nozzles;

or

stain fixtures and cause taste and odour problem s.

C oagulation is one of m any treatm ent options available to

im prove surface w ater quality. Biological treatm ent system s

and filtration are other options. These various treatm ent

options, along with additional com ponents, can provide

water to m eet the specific requirem ents of the agriculture

and agri-food sector.

C oagulation is best suited to treating surface water for

livestock consum ption, chem ical m ixing and dom estic use.

D ugout coagulation has proven very effective to rem ediate

old dugouts, or dugouts affected by flooding. Farm ers who

AUTHO REDBY: L. Braul, PFRA

FUN DING : Strategic support and funding for this project has been provided by the C anada-Saskatchew an Agri-Food Innovation Fund

(AFIF) and C anada-Saskatchew an Agriculture G reen Plan Agreem ent.

END O RSEM ENT: This report should not be taken as an endorsem ent by PFRA or Agriculture and A gri-Food C anada of any of the products or

services m entioned herein.

require good quality surface water for m ixing with herbicides

com m only use dugout coagulation as a treatm ent m ethod.

C oagulation has also been used experim entally, to supply

higher quality water for cattle and hogs. It m ay also be

useful for applications such as food processing and drip

irrigation.

C oagulation cells, as well as the com m ercial system , are

valued for supplying im proved water quality for dom estic

use. In som e cases, such as chem ical m ixing, it m ay be the

only treatm ent process required. In other cases, such as

food processing, it m ay proceed other treatm ent processes.

For further inform ation on rural Prairie water quality and

treatm ent technology:

read the other publications in PFRAsWaterQuality

Mattersseries;

visit the PFRA website at www.agr.gc.ca/pfra;

get a copy of Rural Prairie W ater Q uality: Searching

for Solutions for O n-Farm U sersavailable from PFRA

read Prairie W ater N ew s, available from PFRA, or on

the Internet at www.quantum lynx.com /water; or

contact your local Prairie Farm

Rehabilitation Administration Office

(PFRA is a branch of Agriculture and Agri-Food

C anada).

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