If you store drinking water, chances are you’ve had to deal with algal blooms, especially in mid-summer. The presence of microflora in your water manifests in all sorts of ways – everything from a light green tinge creeping through a previously-clear tank to a thick scum of drifting tendrils that resembles damp, verdant cotton wool.

Humans are hardwired to hate the taste of algae, so no matter the extent of the bloom, you’ll know if you’ve drawn contaminated water from your tank. Even a light taint will render your water undrinkable.

Fortunately, algal blooms are easy to control. Here’s how.

What Causes Algae Blooms in Water Tanks

Whether the bloom affecting your water supply is light or heavy, it will be produced by cyanobacteria or blue-green algae. These blooms can appear due to a few reasons:

• Sunlight exposure: More sunlight means more light for photosynthesis, providing better conditions for algae to grow and flourish.
• Nutrients: Algae also thrive when they can access nutrients in the water, which may be introduced via rainwater and organic contamination.
• Stagnant water: Algae can take hold fairly easily in water without any natural circulation.

In a light bloom, tiny, free-floating organisms encounter just enough nutrients and sunlight to enable them to grow and multiply.

In a heavy bloom, they get so much light and food that the population begins to explode. Many then die, using up the oxygen in the water and tainting it with the smell of decay.

Is Algae in a Water Tank Dangerous?

Aside from just looking unpleasant, the presence of algae in water tanks can pose some risks, especially if it’s intended to be drinking water. Drinking contaminated water can cause various health issues including gastrointestinal problems and allergic reactions and may even trigger longer-term health concerns.

If large algal blooms are left to multiply, this growth can also cause damage to the water tank itself, compromising its functionality and longevity, and potentially corrupting future storage abilities.

For these reasons, it’s important that you deal with algae contamination when it arises and take preventative measures to prevent the growth of algae in the first place.

How to Stop Algae Blooms in Water Tanks

Algae are ever-present. Unless you plan on irradiating your tank and filling it with distilled water, your store will host its own population of cyanobacteria. But that doesn’t make blooms inevitable!

Prevent Sunlight Exposure

Your first line of defence is to prevent light from reaching the water. Without sunlight, the algae won’t be able to photosynthesise and therefore multiply.

Of course, keeping light out of a plastic tank may be easier said than done, but choosing a modern, UV-resistant XLPE tank will go a long way towards excluding those rays.

If that’s not an option, try painting or shading the outside of the tank.

For more information on the effect of sunlight on tanks, see our guide on how to reduce the impact of UV rays on poly storage tanks.

Use Chemicals

Secondly, you can use chemicals to manage algae. The easiest and cheapest way to treat your stored water is simply to dose it with household bleach. You only need a tiny concentration, about one teaspoon for every 20 litres of water.

If you prefer, you can treat your water as you would a swimming pool, adding four parts chlorine for every million parts water (4ppm).

If using chemicals, make sure to adhere to strict dosing requirements and safety measures, especially if you are managing portable water.

How to Get Rid of Algae in Water Tanks Long Term

If you’re managing an older, well-established installation and you’re experiencing recurrent problems with algae, conventional advice would be to carry out a scrupulous regular drain-and-scrub-down and to fit a multi-stage filtration system.

Filters can certainly be helpful in removing the taste of purifying chemicals, but they can be an expensive retrofit!

Ultimately, for most water stores, the simple solutions set out above are more practical and effective enough.

Managing Industrial Water Storage Tanks

If you’re looking to replace your industrial water storage tank and need some advice on where to start, please get in touch with our team at 01264 243116.

Our fleet of industrial storage tanks provides the ideal solution to liquid management on a large scale.