The idea to recycle hydroponic water is a great one especially when you are thinking about sustainable development. However, recycling comes with its challenges.
Thus, we will be discussing the how to recycle hydroponic water and the factors you need to take care of while recycling.
There are different ways to recycle hydroponic water like pasteurization, ozonation, and UV disinfection. But the key is you clean and sterilizes the water before reuse so that the risk of infection and damage to plants can be minimized.
So, let’s begin with the exact methods on how to recycle hydroponic water.
Different Methods To Recycle Hydroponic Water
Pasteurization is a common method that is used to clean up everyday food items as well. It is done by constantly heating the water and thus killing the bacteria. The process is pretty obvious in the dairy industry to disinfect milk.
Similarly, hydroponic water can also be pasteurized to kill bacteria and reduce mineral build-up.
Removing the bacteria from hydroponic water further ensures the optimal growth of plants with purified water along with preventing the environment from harmful effects.
Great way to pasteurization hydroponic water is by using best exchanger.
The heat exchangers are generally made to exchange the temperatures between two gases or fluids.
The use of heating or cooling agent is done by heat exchangers to heat or cool the water in hydroponics technique. All in all, you need two heat exchangers to transfer the solution in between.
Steps to pasteurize hydroponic water:
- The first step is to monitor the current ph level of running hydroponic water. Then, you need to run that water through 50-70 micron filters while reducing the ph to around 4-4.5.
- Transfer the resultant solution to the heat exchanger to get pumped.
- The water is preheated via a heat exchanger while also recovering the heat from the sterilized solution.
- Pump this sterilized solution into the second heat exchanger while leaving the first one.
- Heat the nutrient solution up to 203˚F and expose it in high temperature for at least 40 seconds.
- Transfer this sterilized solution to get cooled in the first heat exchanger.
2. Ozonation or Ozone Sterilization
When the hydroponic grow room is infused with ozone gas, it is called as Ozonation. Ozone (O3) is a natural gas that is found in high concentrations of the ozone layer as well. The process is also known as the O3 disinfectant system.
Ozone proves to be highly effective for water treatment to prevent pests and plant diseases. The direct contact of plants with oxygen is also helpful for their optimal growth.
It is one of the effective solutions if you are also experiencing problems in plants such as mold, mildew, plant odor, virus, bacteria, and fungi. The technique is also used to control algae and organic matter build-up in water.
Also, Ozonation is the most used sterilizing method on how to recycle hydroponic water.
What are the ultimate benefits of ozone sterilization?
Besides disinfecting the water, it offers immense benefits to the plants. The very first advantage is that it acts as a sanitizer for a nutrient solution in the hydroponics system. The next thing it does is to eliminate algae, pathogens, and microbes.
The oxygen level is being increased in the plants for effective growth. It further results in increased crop yields.
With ozone sterilization, you will save bucks on chemical fertilizers.
The last benefit is that it deodorizes the air in the hydroponics grow room.
Materials required for hydroponic water ozone sterilization:
You can either use Corona Discharge Ozonator or Ultraviolet ozonators. These are two broad categories of ozone generators used for the purpose. You go with Mammoth Ozone generator which is best ozone generator that you can buy. The very process aims to split oxygen molecules into individual atoms of oxygen.
Installation of the venturi injector is there on the bypass of an irrigation pump to suck the ozone gas from the ozone generator. This kind of system is generally found in Corona Discharge ozone generators.
Defining the process of ozone sterilization via Corona Discharge Ozone Generators
During the transfer of nutrient solution to the crop, a small proportion of this nutrient solution is diverted back into the mixing tank through the bypass. This bypass is what we have discussed earlier that also consists of a venturi and control valve.
The output pressurized flow creates a suction action through the venturi. The outlet of the ozone generator is connected with the air inlet of the venturi. This connection helps in removing the ozone gas from the ozone generator and injecting it further into the passing flow.
The process continues to sanitize the hydroponic water tank.
Defining the process of ozone sterilization via UV generators
UV sterilization is done to inactivate the growth of pathogens and microorganisms via UV light. The process is continued while the water is present in the UV chamber with long contact time.
The UV light disinfects this water by sterilizing all the contaminants. It will also prevent the replication of these contaminants. The ozone layer will further destroy these contaminants by their sheer breakage.
Lastly, the ozone is dissolved back with oxygen while resulting in the beneficial growth of plants.
Steps for Ozonation of hydroponic water:
- As usual, you first need to filter the hydroponic water with a 50-70 micron filter.
- Check ph level and adjust it between 4-4.5.
- Use an ozone generator to pump this hydroponic water into.
- Lastly, the level of nutrient solution will ultimately determine the requirement of ozone and period of sterilization.
3. UV Disinfection
UV Disinfection is another effective technique for cleaning and sterilization of hydroponic water. It is cost-saving as well. This chemical-free method generally works by passing the water via a radiation chamber that further holds high-pressure UV lamps.
What it does is penetrate through the water molecules to get rid of harmful bacteria and pathogens. The method is also used to sterilize drinking water by removing its chlorine content.
The underlying principle of flowing UV rays helps to destroy harmful bacteria and pathogens in water and further destroy its DNA. The technique is pretty natural without any involvement of dangerous byproducts.
However, the high doses of UV rays are generally preferred to remove chlorine or other heavy metals.
But how do you calculate UV dose?
UV Dose can be expressed in mJ/cm2 or mWs/cm2. The accepted UV dosage for most of the standards is said to be 30mJ/cm2. The longer the hydroponic water remains in contact with the chamber, the higher the UV dose.
So, you can calculate UV dose based on two amounts i.e. Intensity and Time (Contact Time). The intensity is measured by the quantity of UV light per unit area. Then, there is a contact time of hydroponic water with the chamber.
Furthermore, a list of factors can affect UV dose including the presence of iron, hardness, UV transmittance, turbidity, and tannins.
Materials required for UV disinfection:
You are required to have a stainless steel radiation chamber containing a high-power UV lamp.
The hydroponic water gets passed through this radiation chamber while receiving a lethal dose of UV rays. These UV rays are known to destroy the DNA of harmful bacteria, microbes, and pathogens.
Steps for UV disinfection :
Now, we are going to ascertain the exact steps to know how to recycle hydroponic water. Before knowing the steps, we’d like to mention that UV radiation comes with three types depending upon the wavelengths.
UV-C disinfection is said to be the most ideal among these three types. They consist of the highest energy and shortest wavelength of around 254 nanometers.
- Pour the hydroponic water into a UV radiation chamber containing a high-power UV lamp.
- Let it pass through the radiation chamber.
- The hydroponic water is being disinfected through the quartz tube in the UV radiation chamber.
- All this process is controlled by a computer for the process that gets blocked in case of a low UV dosage.
How to Choose the Right Method?
It may be pretty complicated for you to discuss the best technique after discussing all the methods. All the processes have their own merits and demerits. Thus, it boils down to personal preference while choosing the ideal method.
However, the process of UV disinfection is most cost-effective as compared to Ozonation and pasteurization. It is dependent upon your budget to choose the best recycling method.
Then, the factor of equipment availability comes in between to choose the best technique. So, UV radiation chambers are cheaper to buy with economical maintenance costs.
However, Ozonation and pasteurization are suitable for large operations.
Important Things Keep In Mind
Having recycled the hydroponic water, you should maintain it carefully for prolonged use. Given below is a list of factors that you need to take into account while using recycled hydroponic water.
So, maintaining a hydroponic reservoir should be an afterthought of recycling.
1. Maintain the ideal temperature of nutrient solution
The temperature that is too hot or too cold is not ideal for the nutrient solution. The required temperature for nutrient solution should be kept between 65-75 degrees. The oxygen levels go very deep while the temperature gets too hot.
On the other hand, low temperatures will slow down the growth of plants. So, you can do many things to cool down the temperature of the nutrient solution.
You can buy a chiller, paint your reservoir with white color, place it in the shade, increase the overall reservoir size, and top off the solution, etc. There are more chances of temperature fluctuation in small reservoirs than larger ones.
So, the reservoirs around 75-gallons capacity are good to go for. Top off solution means to add the cooler nutrient solution itself. You can also bury this hydroponic reservoir in the ground or make your cooling coil.
The cooling coil can be designed to avoid the expensive purchase of water chillers.
Aquarium heaters are preferred to warm off the nutrient solution.
2. Change or Recycle Hydroponic Water
You should change or recycle the hydroponic water based upon your personal preference. You must change the nutrient solution weekly or bi-weekly. If you are already following the recycle schedule properly and using the EC meter, you can wait for a week or two longer.
EC meters are helpful to determine the amount of fertilizer in hydroponic water. However, they can’t tell you the specific amount of each nutrient. And, topping off for too long may not be ideal as plants don’t take nutrients at the same rate.
It may lead to the build-up of certain minerals. Therefore, you must clean the hydroponic reservoir frequently.
3. Proper Aeration
Aeration is required to maintain adequate oxygen levels for the submerged roots of hydroponic plants. The ideal requirement of air is said to be 1 liter per minute for each gallon of nutrient solution. So, the 100 LPM air pump is needed for 100 gallons of water.
However, you should not focus on excessive aeration as it may prove to be counterproductive. Too much aeration causes bubbles which further leads to the diffuser or air stone to create friction. And, high friction is also not good for the optimal growth of hydroponic plants.
Oxygenating the hydroponics nutrient solution also protects it from becoming anaerobic. The oxygenation rate of ½ to ¼ is ideally required for the DWC system. It would be fine of the surface of the nutrient solution is broken with bubbles.
You can use growing media such as perlite; grow stones or coco coir chips for aeration. Or, you can vigorously circulate the nutrient solution to increase its amount of dissolved oxygen.
However, using a hydroponic air pump is one of the effective methods made specifically to enhance aeration in hydroponic growing.
4. Clean your hydroponics system
You must maintain the cleanliness of the hydroponic system to prolong its recycled water. You can call it as doing sanitization of your hydroponics system. Dead plant matter, spilled water, and air intake filters are all part of this maintenance.
It is often recommended to use 35% of hydrogen peroxide (food-grade) after diluting it to the 3% solution. You can mix 11 parts of clean water to this 35% hydrogen peroxide diluted solution. You should use gloves as a safety precaution as exposure to hydrogen peroxide can lead to skin burns.
Start by cleaning at the top of the hydroponics system. Carefully clean electrical areas. Don’t forget to clean the filters as pests love to stay there. In case of no filter specifically in the DWC system, you must clean the floating debris in the nutrient solution.
5. Regular EC and PH checks
It is equally important to adjust the levels of nutrients in the nutrient solution. And, the key measurements for the purpose are said to be PH and EC levels. You can do both the calculations with meters.
Acidity in a hydroponic nutrient solution is measured by PH whereas EC is the measurement of salt levels in a hydroponics system. However, you can also buy dual meters to measure the EC and PH levels in a single device.
Ideal EC for hydroponics system: 1.2 – 2.0
Ideal PH for hydroponics system: 5.5 – 6.5
You can adjust the PH level by adding a base or acid solution. Raise the PH level by adding a base solution and vice-versa.
You can lower EC levels by dilution with fresh water.
6. Check Equipment
It is never a bad idea to regularly check your hydroponics system equipment. Take care of aerators, broken pumps, connectors, and other kinds of equipment in hydroponics. It is great if you keep backups.
Most of the time, things break at inconvenient times, you must create equipment backup.
So, this is how to recycle hydroponic water in different ways. The selection of method is wholly dependent upon your personal choice, budget, and other factors mentioned above. However, UV disinfection is said to be the most cost-effective way than Ozonation and pasteurization. On the other hand, both pasteurization and Ozonation are suitable for large hydroponics.
Proper maintenance after recycling is another important concept we have mentioned above. You must note down all the factors for the cleanliness of the hydroponic system. Keeping your nutrient solution healthy is equally important as recycling the hydroponic water.