Advice Articles

How To Prevent Algae Growth In Water Storage Tanks

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.

And, as you’ll know if you’ve drawn contaminated water from your tank, humans are hardwired to hate the taste of algae. Even a light taint will render your water undrinkable.

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

What makes a bloom?

Whether the bloom affecting your supply is light or heavy, it was produced by cyanobacteria, or blue-green algae.

In a light bloom, these tiny, free-floating organisms encountered just enough nutrients and sunlight to enable them to grow and multiply. In a heavy bloom, they got so much light and food that they began a population explosion. Many die, using up the oxygen in the water and tainting it with the smell of decay.

What’s the easiest way to control a bloom?

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!

Your first line of defence is to prevent light from reaching the water. Without sunlight, your algae won’t be able to photosynthesize, so they can’t 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.

Secondly, chemicals! 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).

What are the long-term options?

Imagine you’re managing an older, well-established installation and you’re experiencing recurrent problems with algae. The 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! For most water stores, the simple solutions set out above are practical.

If you’re looking to replace your industrial storage tank but aren’t sure where to start, get in touch with our team on 01264 243116.