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Restful, relaxing, and peaceful are common words to describe a walk by a pond. A small reminder of the simpler things in life, ponds can bring a sense of calm where you leave the stresses of the day behind for a moment of respite. These comforting terms in describing a pond are thrown out the window when walking by a pond that is overgrown and overrun with algae.

Algae-laden pond water has been cited as a source causing illness when used as an irrigation spray. This water should be used cautiously due to potential risks of using pond water. Additionally, the comforting terms to describe a peaceful walk by the pond are replaced with typically negative terms of dirty and stinky.

Algae is not all bad. It serves a role in a pond ecosystem providing food for given species. However, there are obvious benefits in controlling or inhibiting extreme growth in ponds.

Chlorine dioxide is well documented for treating water and water systems, but can chlorine dioxide be an effective treatment solution for filtering algae-laden pond water? Dr. Greg Simpson with PureLine created an experiment to observe the filterability of pond water with algae when treated with chlorine dioxide.

Can Chlorine Dioxide Improve the Filterability of Algae-Laden Pond Water?

One group wanted to drain a pond that had a significant growth of algae. The water is shown in the photo below, left. 

A 60 mL plastic syringe equipped with a 0.45 μm cellulose acetate filter was filled with sample and an attempt was made to push this green algae-contaminated water through the filter. Only < 2 mL could be filtered. This was attempted twice.  A photo of the filter is shown below.

Pond Experiment

Experimental Setup

A 4-Liter beaker was used to hold the sample, while two ORP probes were inserted into the sample after calibration. ORP measurements were taken every minute during the treatment. 

The ORP data was read and stored by an eController, which is shown in the photo right.

Separately, a standard solution of chlorine dioxide (Pure3000) was measured to have a chlorine dioxide concentration of 2269 ppm.  An Eppendorf pipette was used to add chlorine dioxide solutions in 1-mL increments every 5 – 10 minutes. 

Pond Experiment

Experimental Results

The plot of the data from only one ORP probe is shown (showing both would have been redundant, as they track.)

Note that the ORP drops rapidly, but, with the addition of chlorine dioxide, there is a spike in the ORP as the chlorine dioxide is mixed and reacts (note the initial red arrow in the graph).

Every mL of chlorine dioxide solution adds 0.57 ppm of chlorine dioxide to the solution.  At several point throughout this experiment, [chlorine dioxide] was tested with the Kemio chlorine dioxide test kit, which uses disposable sensors. 

The timeline of events is also shown in the table below.

Pond Experiment Graph
Pond Experiment Graph 2

Although a point was never reached during this experiment where there was a sustainable chlorine dioxide residual, the goal of this research was to determine if chlorine dioxide helped filterability.

At the end of the experiment, the solution was again filtered using a 0.45 μm cellulose acetate filter.  This time, 44 mL of the treated solution was able to be pushed through the membrane and is shown in the photo to the right.  The left filter is shown for comparison.

Pond Experiment

Pictures were taken at several times of the large beaker.  These are shown below at times: as received, 10:30, 11:31, and 12:35 (end), respectively.

Pond Experiment

The above pictures represent treatment concentrations of 0, 1.71, 9.12, 19.38 ppm chlorine dioxide, respectively.

In addition, very little solution of untreated pond water could be pushed through a 0.45 μm filter initially, while 44 mLs of the last solution in the above photo could be pushed through a 0.45 μm filter.


Chlorine dioxide increases the filterability of pond water with a high algae concentration.


If you are curious to learn more on how to apply chlorine dioxide as a solution for your algae-laden pond, fill out the contact form below and a PureLine representative would be glad to discuss your pond needs!

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