As you probably already know – good water is the backbone of any successful hydroponic system. If harmful anaerobic bacteria sneak into your nutrient solution, they can wreak havoc on your plants, clog your system, and spawn a variety of root diseases and rot. Reverse osmosis (RO) systems are a popular way to purify water, but do they actually remove bacteria from water? Let’s break it down!
How Reverse Osmosis Works
At its core, an RO system forces water through something called a semi-permeable membrane with incredibly tiny pores — about 0.0001 microns. That’s small enough to block most contaminants, including dissolved salts, heavy metals, and organic compounds. A typical RO setup includes pre-filters, the membrane, and post-filters to ensure the cleanest possible output.
The Problem with Bacteria in Water
Bacteria is almost everywhere on earth. But bacteria in hydroponic systems is bad news, especially anaerobic types. Pathogens can contaminate your reservoir, leading to plant diseases and biofilm buildup in tubing. Even if bacteria don’t directly attack your crops, they can clog emitters and disrupt nutrient absorption.
Can RO Remove Bacteria?
Yes. The RO membrane’s pore size is much smaller than bacteria, which typically range from 0.2 to 2 microns. That means an RO system can physically filter out bacteria and prevent it from passing through. However, there’s a catch: RO doesn’t kill bacteria, and if the system isn’t maintained properly, by periodically changing filters and cleaning cartridges, it can actually become a breeding ground for microbial growth.
The Limitations of RO for Bacteria Removal
- Bacteria Can Grow on the Membrane: If your filters aren’t changed and the system isn’t cleaned on a regular basis, bacteria can multiply on the membrane and possibly bypass it. Eeewww
- Leaks and Cracks Allow Contamination: A tiny tear in the membrane or a poorly sealed connection can let bacteria slip through.
- RO Doesn’t Kill Bacteria: Unlike UV sterilization or chlorination, RO only removes bacteria; it doesn’t disinfect water. Might be a good idea to put an inline UV sterilizer after the filter!
How to Make RO Water Even Safer
If you want to practically guarantee bacteria-free water, consider adding one of these methods alongside your RO system:
- UV Purification: A UV sterilizer installed after the RO system kills bacteria that might have survived or grown in the system.
- Ozonation: Injecting ozone into your water destroys bacteria and prevents biofilm formation. And it will oxidize anything else too… So be careful.
- Hydrogen Peroxide or Chlorine Dosing: A controlled dose of these disinfectants can prevent bacterial growth in your storage tanks. But it’s probably not a good idea for hydroponics.
Best Practices for Keeping Your RO System Clean
- Replace filters on schedule. Pre-filters should be swapped every 6–12 months, and the membrane every 2–3 years, depending on usage. This is the easiest and most straightforward recommendation.
- Sanitize the system regularly. Use food-grade hydrogen peroxide or a dedicated RO system cleaner, which are usually relegated to commercial applications, to flush out bacteria.
- Monitor water quality. If you really need to make sure it’s as clean as possible. Using a TDS meter won’t be enough, you’ll need to run periodic bacterial tests to ensure your system is working as expected.
Conclusion
Reverse osmosis is a powerful filtration method that removes bacteria, but doesn’t kill it. If you’re relying on RO for your hydroponic setup, stay on top of maintenance and consider adding a sterilization step to ensure bacteria-free water. Clean water means healthy plants, efficient nutrient absorption, and fewer system headaches. Stay sharp, stay clean, and keep those roots thriving!
What do you think? Let me know in the comments below.