Evaluation of Water Acidification Products

Researchers at the University of Arkansas compared citric acid, copper sulphate and sodium bisulphate as treatments for water contaminated with bacteria, yeasts and moulds, and found that none made highly contaminated water safe. Brookee Dean, Jennifer Hughes, Tyler Clark and Susan Watkins published their results in the latest issue of the University's Avian Advice.
calendar icon 11 November 2008
clock icon 6 minute read

Senior author, Dr Susan Watkins


Acidification products are often used as water line cleaners in poultry houses. However, recent field observations indicate that utilizing acids in water systems which are heavily contaminated with microbes could be more harmful than helpful in water sanitation programs.

The following lab test was conducted to evaluate the effects of different types of acidification products on general microbial levels in 'dirty' water. In addition, the goal was to determine if acid products might vary in their ability to reduce microbial content in water at different pH levels.

Materials and Methods

In this test, four water acidification products (acidified copper sulphate, citric acid (food grade), citric acid (Russell), and sodium bisulphate) were evaluated for their ability to reduce aerobic bacterial, yeast and mould counts in dirty water. Stock solutions of acidified copper sulphate or sodium bisulphate were prepared by mixing 453.6g with 2 gallons of water. Citric acid stock solutions were made by combining 453.6g of food grade or Russell citric acid with half a gallon of water. Each acidification product was tested at pH values of 4 and 6, resulting in a total of 9 treatments (including controls).

Water used in this test was obtained from an open cattle stock water trough during warm weather and contained visible algae growth. The water was blended to ensure consistency and then 50ml samples of the water were transferred to eighteen small beakers, two beakers per treatment. Prior to adding the test products to each beaker, initial aerobic bacterial, yeast and mould counts were determined using Petrifilm™. Products were added the appropriate beakers to achieve pH values of 4 and 6.

Beakers were held at room temperature uncovered and retested at 2 and 24 hours post-treatment. Counts were converted to log10 values and statistically analyzed.

Results and Discussion

The initial aerobic bacterial counts before treatments were very high and almost identical for all treatments (Table 1). Consistently high counts were found in control samples at both 2 and 24 hours post treatment.

Counts from citric acid (Russell), citric acid (food grade) and sodium bisulphate pH 6 were not significantly different from control at either sampling time.

While a small (<1 log), but significant (P<0.05) decrease was observed in counts from sodium bisulphate pH 4 at 2 hours post-treatment, no differences from control were found in this treatment at 24 hours.

Only the acidified copper sulphate treatments (both pH 4 and 6) gave a significant (P<0.05) reduction of 2 logs or 99% at 2 hours and 24 hours post-treatment.

It is important to point out that log counts of greater than 4.0 mean that there are over 100,000 cfu/ml were still present in the water after treatment and that water system cleaning is strongly recommended when aerobic bacterial counts are 10,000 cfu/ml or higher.

Table 1. Effect of Common Acidifiers on Aerobic Bacterial Counts from Dirty Water
Product pH Aerobic Bacterial Counts (Log10)
Pre-Treatment Counts Post-Treatment
2 Hours
24 Hours
Control (Dirty Water) 7.94 6.68 6.62c 6.47b
Acidified Copper Sulphate 4 6.71 4.22a 4.15a
Acidified Copper Sulphate 6 6.62 4.49a 4.42a
Citric Acid (Food Grade) 4 6.88 6.75c 6.35b
Citric Acid (Food Grade) 6 6.60 6.52c 6.38b
Citric Acid (Russell) 4 6.71 6.48c 6.27b
Citric Acid (Russell) 6 6.71 6.71c 6.57b
Sodium Bisulphate 4 6.74 5.87b 6.17b
Sodium Bisulphate 6 6.69 6.52c 6.44b
SEM .14 .18 .15
P Value .9470 .0001 .0001
a,b,c Means in a column with different letters were different (P<0.05).

Both yeast and mould counts from control samples increased slightly over the course of the trial (Table 2 and 3). This increase in counts may reflect that long-known fact that growth of the majority of yeast and mould species is favoured by acid pH values (Frazier, 1967).

No significant difference from control was found in yeast or mould counts from any treatment at 2 hours posttreatment. Only the acidified copper sulphate pH 4 treatment showed a small (<1 log) but significant (P<0.05) decrease in both yeast and mould counts at 24 hours post-treatment.

While mould counts from acidified copper sulphate pH 6 and citric acid (food grade) pH 6 were significantly (P<0.05) reduced compared to control, these differences were less than 0.25 log.

Table 2. Effect of Common Acidifiers on Yeast Counts from Dirty Water
Product pH Yeast Counts (Log10)
Pre-Treatment Counts Post-Treatment
2 Hours
24 Hours
Control (Dirty Water) 7.94 4.37 4.66 4.66b
Acidified Copper Sulphate 4 4.34 4.17 4.03a
Acidified Copper Sulphate 6 4.34 4.31 4.57b
Citric Acid (Food Grade) 4 4.58 4.35 4.66b
Citric Acid (Food Grade) 6 4.37 4.24 4.49b
Citric Acid (Russell) 4 4.39 4.09 4.67b
Citric Acid (Russell) 6 4.29 4.52 4.60b
Sodium Bisulphate 4 4.37 4.25 4.48b
Sodium Bisulphate 6 4.30 4.50 4.57b
SEM .33 .22 .06
P Value .9995 .0929 .0013
a,b Means in a column with different letters were different (P<0.05).

Table 3. Effect of Common Acidifiers on Mould Counts from Dirty Water
Product pH Mould Counts (Log10)
Pre-Treatment Counts Post-Treatment
2 Hours
24 Hours
Control (Dirty Water) 7.95 3.16 3.69 3.53cd
Acidified Copper Sulphate 4 3.12 3.13 2.73a
Acidified Copper Sulphate 6 3.19 3.35 3.30b
Citric Acid (Food Grade) 4 3.34 3.42 3.48c
Citric Acid (Food Grade) 6 3.19 3.07 3.30b
Citric Acid (Russell) 4 3.15 3.08 3.65d
Citric Acid (Russell) 6 3.25 3.45 3.59cd
Sodium Bisulphate 4 3.37 2.85 3.48c
Sodium Bisulphate 6 3.30 3.47 3.65d
SEM .37 .22 .049
P Value .9998 .3371 .0001
a,b,c,d Means in a column with different letters were different (P<0.05).


Drinking water quality continues to be an area of concern for poultry growers. Recently a company swabbed different areas of a drinker system including stand pipes, inside nipple drinkers and water hoses. They were shocked to find E. coli, Pseudomonas aeruginosa, Staphylococcus and Klebsiella penumoniae. This confirms the fact that water systems can become breeding grounds for various disease organisms.

Protecting the water system by cleaning with appropriate disinfectants and then establishing a daily water sanitation program is an excellent insurance program against water-borne diseases.

The results of this test further confirm that using acidifiers even at a pH of 4 are not enough to thoroughly kill all microbes when a water system is heavily loaded with microbial growth. Utilizing the wrong products to clean systems -- particularly on farms with a disease history -- can be a waste of time and money.


Frazier, W. C. 1967. Food Microbiology, 2nd Ed. McGraw-Hill Book Co., New York.

November 2008
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