Algae and Algal Toxin Control in Well Water (What to Know)

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Algae and algae toxins aren’t just an aesthetic water quality issue – they can also have dangerous health effects.

Here, we’ve shared everything you should know about algae and algae toxins in well water supplies.

๐Ÿ“Œ Key Takeaways:

  • Algae is a plant-like bacteria that contaminates natural water sources. Some types of algae have health effects.
  • Algae commonly grow in well water that’s exposed to direct sunlight or warm temperatures, alkaline water, or wells that are unused for long periods.
  • Conventional drinking water filters won’t remove algae from water. You need a dedicated disinfection system, like a UV purifier or a chlorine injection system.

๐Ÿงซ What Is Algae In Well Water?

Algae is a type of bacteria that commonly occurs in lakes, rivers, springs, and streams.

There are four common types of algae in natural water sources:

  • Chlorophyta, or green algae
  • Rhodophyta, or red algae
  • Diatoms or bacillariophyta, or brown algae
  • Cyanobacteria, or blue-green algae

Blue-green algae is the most dangerous type of algae in drinking water because it produces harmful algal blooms (HABs), which, in turn, produce toxins (cyanotoxins). Microcystin and cylindrospermopsin are the two most common toxins produced by algae bacteria in well water supplies.

Municipal water suppliers must reduce algae down to safe levels in public drinking water, but private wells are the responsibility of the well owner to test and treat. So, if your well water contains algae, it’s your job to remove it.

Algae in well water

๐Ÿ“ฅ How Does Algae Enter A Well Water Supply?

Algae is most likely to grow in a well that’s exposed to warm temperatures, has access to sunlight, or is unused for a long period of time.

Well water is also more prone to phosphorus and nitrogen contamination, and the presence of these two contaminants encourage algae buildup and growth. If your well is located in a region of heavy agricultural activity, your water will likely contain nitrogen and phosphorous from fertilizer runoff.

Some of the signs that your water contains algae include:

  • Musty, moldy, or mildew-tasting or smelling water
  • Biofilm accumulation on your fixtures and faucets

Your well is also more likely to have algae growth if your area is affected by local algal bloom contamination. Contact your local water authority for more information.

๐Ÿฉบ Potential Effects Of Algae In Well Water

Not all algae in drinking water is harmful to health, but some types of algae may produce dangerous microcystins.

Here are some of the potential short-term health effects of ingesting harmful algal blooms in well water:

  • Abdominal pain
  • Diarrhea
  • Headache
  • Tiredness
  • Vomiting
  • Numbness
  • Fever
  • Muscle weakness
  • Tingling
  • Dizziness

In the long term, prolonged exposure to algal blooms in tap water may result in kidney and liver damage.

Feeling sick after drinking water

๐Ÿงช How To Test For Algae In Well Water

When you think of algae, you might imagine the green, slimy stuff that floats on the surface of some ponds. But the reality is that algae produce harmful toxins that are invisible and have no smell or color – so your water might contain high concentration of algal blooms, and you’d be none the wiser.

So, the only way to know for certain whether or not your well water contains algae is to conduct a water test.

We recommend buying a certified laboratory test for the most accurate and comprehensive test results.

Water testing with tap score

The laboratory will test your water for you. You just have to take several samples of your water and send them to the lab in the provided containers, then wait for your results to be delivered (usually via email).

How often should you test your well for algae?

  • If your well is less than 60 feet deep, test your water annually
  • If your well was constructed before 1979, test your water annually
  • Test your water at any point if E. coli is detected, the water appears cloudy or has a blueish-green hue, or the ground surrounding the well is highly permeable

โš—๏ธ How To Remove Algae From Well Water

Shock chlorination is the best way to quickly and thoroughly eliminate algae in your well’s drinking water supply.

Chlorine bleach also kills bacteria and viruses, so it’s a good solution if your well has become contaminated by a range of microorganisms.

Check your state regulations before shock chlorinating your well. In most states, the well owner can do this themselves, but you might prefer to hire an expert to do it for you.

Here’s a short overview of how to shock chlorinate your well water to eliminate algal blooms:

  1. Clear debris from around the well cap and make sure the area is clean, dry, and obstacle-free.
  2. Disconnect or switch off your well’s electrical connections.
  3. Gather your materials. You’ll need a 5-gallon bucket, some household bleach, a hose, and a funnel.
  4. Disconnect or engage the bypass valves to divert water around your water treatment systems.
  5. Dilute the bleach solution in standing water in the bucket, then pour it into your well.
  6. Attach a garden hose to the wellโ€™s hose bib, point the nozzle into the well, and switch it on. Leave it running for 15 minutes.
  7. Switch on a faucet in your home and wait until you can smell chlorinated water.
  8. Let the chlorine bleach sit in the well for 6-12 hours.
  9. Open your outside faucets and flush the water until you can no longer smell chlorine. Do the same with all the faucets in your home.

Because chlorination takes time, and drinking high levels of bleach in water isn’t safe, you’ll need to use bottled water for drinking and cooking during the process.

How much chlorine bleach you need depends on the diameter of the well casing and the water depth:

Amount of Bleach Required According to Well Casing Diameter

Well Casing Diameter10 feet20 feet30 feet40 feet50 feet100 feet
2 inches3/4 tbsp1-1/2 tbsp2-1/4 tbsp3 tbsp3-3/4 tbsp7-1/2 tbsp
4 inches3-1/4 tbsp6-1/2 tbsp9-3/4 tbsp13 tbsp1 cup2 cups
6 inches1/2 cup1 cup1-1/2 cups2 cups2-1/2 cups5 cups
8 inches3/4 cup1-1/2 cups2-1/4 cups3 cups3-3/4 cups7-1/2 cups
10 inches1-1/4 cups2-1/2 cups3-3/4 cups5 cups6-1/4 cups12-1/2 cups
24 inches7 cups14 cups1-1/4 gal1-3/4 gal2-1/4 gal4-1/2 gal
36 inches1 gal2 gal3 gal4 gal5 gal10 gal

Amount of Bleach Required According to Well Diameter

Well Diameter10 feet20 feet30 feet40 feet50 feet
0.5 foot1/2 cup1 cup1-1/2 cups2 cups2-1/2 cups
1 foot1-3/4 cups3-1/2 cups5-1/4 cups7 cups8-3/4 cups
2 feet7 cups14 cups1-1/4 gal1-3/4 gal2-1/4 gal
3 feet1 gal2 gal3 gal4 gal5 gal
4 feet1-3/4 gal3-1/2 gal5-1/4 gal7 gal8-3/4 gal
5 feet2-3/4 gal5-1/2 gal8-1/4 gal11 gal13-3/4 gal

After you’ve shock chlorinated your well, wait 7-10 days, then retest your water for algal blooms.

๐Ÿ‘จโ€๐Ÿ”ง Looking for a more detailed overview of the well shock chlorination process? Check out our guide on how to shock chlorinate a well.

Man shocking a water well

๐Ÿšฐ Long-Term Treatment Methods For Algae In Well Water

Here are our recommended methods for long-term removal of algae in well water.

UV Purifiers

A UV purifier treats water with ultraviolet light, which works to instantly kill microorganisms including algae by damaging their DNA.

You can install a UV purification system at the main water line after it enters your home. If you have any other well water treatment systems, install the UV system downstream of these systems.

UV is a highly effective and chemical-free method of killing algae and preventing further algae growth, and provides instant results without the need for extended contact time with the water – but it only works on clear (non-turbid) water.

So, if your water contains suspended particles, tannins, iron, or any contaminants that affect your water’s clarity, you’ll need to remove these with a whole house water filter upstream of the UV system, so that the UV process can work effectively.

๐Ÿ‘จโ€๐Ÿ”ง Related: Exploring the Top UV Water Purifier Systems of March 2024

Chlorine Injection Systems

Chlorine injection is another long-term treatment method that will stop algae growth in your well supply.

If you have continued problems with algae, a chlorine injection system will protect your water supply for years on end.

This system injects chlorine into your water supply, which kills microorganisms like bacteria and algae. It’s a bit like municipal water disinfection, except on a smaller scale.

The advantage of chlorination compared to UV purification is that the chlorine lingers in your water, protecting it from recontamination on its journey through your plumbing system, and preventing regrowth in your well water tank.

However, chlorine injection systems need more maintenance because you have to top up the chlorine, and not everyone wants to add even small amounts of toxic chemicals to their water.

Pouring chlorine to Springwell chemical injection system

๐Ÿšฑ How To Prevent Algae In Well Water Tanks

Algae in your well water might end up accumulating in your water tank.

Here are the best ways to eliminate algae growth in well water storage tanks:

  • Disinfect the tank with bleach. You can manually disinfect your tank with around one-quarter teaspoon of bleach per 1 gallon of water in the tank. 5.25% hypochlorite bleach works best.
  • Use an opaque water storage tank. Algae need sunlight to reproduce, so make sure your water storage tank has no transparent parts that allow light into the tank.

๐Ÿ“ค How To Remove Algae From Water Filters

Got a whole house water filter system that has been contaminated with algae growth?

You’ll need to take the system apart and remove the filter cartridges from the housing, then thoroughly wash the housings with warm water and dishwashing detergent.

Rinse the filter cartridges under running water (don’t use soap or detergent). If you think the algae has already done its damage, replace the cartridges with new ones.

Make sure to address the algae in your well water to prevent recontamination of your whole house water filter.

Algae growth in water filter cartridges

๐Ÿ”š Final Word

Algae in drinking water is dangerous, so if you have any reason to believe that your well water may be contaminated with algae spores, act accordingly.

Test your water for algae, and install a suitable water treatment solution to kill or eliminate harmful algae blooms.

Remember that a conventional water filter system won’t work to filter out water – and, in fact, the algae could end up contaminating the filter media. You need a dedicated disinfection method, such as a UV purification system or a chlorine injection system.

โ” FAQ

Is it OK to drink water with green algae?

No, it’s not OK to drink water with green algae. Depending on how much algae you consume, you might experience side effects including headaches, vomiting, diarrhea, and fever. Remove algae from water before drinking or switch to another water source.

What happens if I drink water with algae?

If you drink water with algae, you might experience no symptoms, or you might experience gastrointestinal effects, like vomiting and diarrhea, depending on the type of algae you ingest and how much water you drink.

Will boiling well water remove algae?

No, boiling your well water won’t remove algae toxins. It’ll just cause some of the water to evaporate, so you’ll have the same amount of algae in a smaller volume of water. The only way to kill algae is by using a method of water disinfection. After that, boiling your water for cooking and other purposes is safe.

What’s the safe amount of algae in well water?

According to EPA regulations, the safe amount of Microcystins & Cylindrospermopsin (which are produced by blue-green algae) for children is 0.3 parts per billion and 0.7 parts per billion (PPB), and 1.6 PPB and 3 PPB for adults. Well water isn’t regulated by the EPA, so it’s your responsibility as the well owner to reduce algae concentrations to within these safe limits.

Can you filter toxic algae out of water?

No, you can’t filter toxic algae out of water with a conventional water filter. You need to use a method of water disinfection, which kills microorganisms like toxic algae. Shock chlorination is a good treatment if you have a major algae problem. For long-term treatment, use a chlorine injection system or a UV filter.

Is it safe to shower in algae contaminated well water?

Yes, it’s safe to shower and bathe in well water that’s contaminated with algae. Just be careful not to swallow any of the water. You can also use algae contaminated water to wash your dishes and do your laundry.

  • Jennifer Byrd
    Water Treatment Specialist

    For 20+ years, Jennifer has championed clean water. From navigating operations to leading sales, she's tackled diverse industry challenges. Now, at Redbird Water, she crafts personalized solutions for homes, businesses, and factories. A past Chamber President and industry advocate, Jennifer leverages her expertise in cutting-edge filtration and custom design to transform water concerns into crystal-clear solutions.

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