How to Clean and Reuse Water in a Hydroponic System?

Cleaning and reusing your hydroponic water is a great way to lower your water usage and run a more efficient grow room.

A smart hydroponic system can help reduce our water consumption, protecting the environment and our pockets by reducing costs.

However, reusing hydroponic water does have its challenges. Old water can carry bacteria, viruses and diseases that can be passed from one crop to another. Therefore, it is very important to disinfect and clean the water before it is reused to minimize the risk of infection and damage to plants.

Ⅰ. Disinfection method of smart hydroponic system

1. Pasteurization (= pasteurization)

Pasteurization is a process that uses heat to kill bacteria. It's really common in the dairy industry, to sterilize milk; but pasteurization can also be used to clean and sterilize a variety of other liquids, including water for hydroponic culture.

Pasteurization involves rapidly heating water. This is accomplished with heat exchangers, which are designed to exchange temperatures between two fluids or gases. Without going into too much detail, a heat exchanger uses a fluid or gas to heat/cool water in a hydroponic system.

One of the great benefits of pasteurization is that there is no need to pre-filter your water. It also helps reduce the buildup of minerals and other biological agents in the water. Unfortunately, these agents can build up in the heat exchangers used to pasteurize the water, meaning they need to be cleaned regularly to keep working efficiently.

2. Ozone disinfection (ozonation)

Ozonation involves injecting water with ozone (O₃), a natural gas that is abundant in the ozone layer and is produced by the sun's ultraviolet radiation. It can also be artificially produced for disinfection and hydroponics.

Ozonation requires an ozone generator to generate ozone gas in the culture chamber. There are two types of ozone generators, both of which work by splitting O₂ molecules into individual oxygen atoms. These atoms quickly combine with O₂ molecules to create ozone (O₃), which is then injected into the water to kill any pollutants.

Ozonation has many benefits. This is by far one of the most effective ways of sanitizing water, reacting quickly to any contaminants. It's also environmentally friendly, and using ozone in your grow room can help keep diseases and pests (including spiders and mites) off your plants. However, ozonation is an expensive process. Ozone is also highly corrosive and can damage equipment in your system if not used properly.

3. UV disinfection

UV disinfection is another very effective method to clean and recycle the hydroponic water of the smart hydroponic system. It's completely chemical-free, making it an attractive fungicide for growers looking to keep it as natural as possible.

UV water disinfection works by passing water through a radiation chamber containing high pressure UV lamps. The ultraviolet light from the lamp penetrates molecules in the water (such as bacteria and other harmful pathogens), damaging their DNA. At higher doses, UV disinfection can also remove chlorine from water (a process known as photolysis). UV radiation is commonly used to disinfect drinking water, such as the Catskill-Delaware Water UV Disinfection Facility in New York, USA, for drinking water disinfection in New York City.

UV water disinfection is very cost-effective compared to pasteurization and ozonation. It is also completely natural and produces no dangerous by-products. The main disadvantage of UV disinfection is that it cannot neutralize dissolved organics, chemical pollutants or inorganic compounds in water. This means it cannot remove normal doses of heavy metals, salts or chlorine (photolysis requires high doses of UV light).

Ⅱ. How to choose the water disinfection method for smart hydroponic system?

All of the water purification methods we have mentioned in this article have different benefits. However, they all have their limitations. Which method of disinfection to choose depends on your personal preference, your budget, the availability of the required equipment in your area, and the size of your grow.

If you want to keep costs down, UV radiation is probably the way to go. Ozone generators and pasteurizers are expensive pieces of equipment. They also come with maintenance costs, which will add to the total cost of your entire operation. UV chambers, on the other hand, are less expensive for both a one-time purchase and long-term operation, making them ideal for growers on a budget.

UV and ozone disinfection are also better suited for larger operations. Hot pasteurization is much more expensive and more suitable for small growers with big budgets. Ozonation also provides the best results for the simple reason that ozone is a strong disinfectant. Remember, it is highly corrosive and needs to be handled with care.