In hydroponics, filtering and cleaning primarily refers to getting rid of unwanted compounds, rather than mechanical filtering and cleaning (to protect the pump from various plant debris and various fine dust and dirt). The task of such cleaning is much more complicated than mechanical although mechanical also cannot be ignored. At the pump, a mechanical filter, such as a synthetic sponge needs to be installed on the inlet pipe and a strainer is even placed on the mains for the feed solution. Filtration is necessary in some cases of central water supply, as well as for well water or other natural source. When growing, it is necessary to protect the plant from various chemical pollutants and pathogens. Before using water for plant nutrition, water must undergo a complete analysis – mineral composition, pesticides and herbicides, residual hydrocarbons, pathogens, microorganisms. There are various laboratories for agricultural needs.
But it should be noted that before applying various types of filtration you need to make sure that it is really needed since there are such curious cases when calcium is filtered from water which is then separately introduced with plant nutrition.
If there is still a need for filtration then there are not many options for the types of filtration for enclosed spaces and each one has some drawbacks. Ions dissolved in water, as if stuck between the molecules and can not be released from them. In a small installation, for a room, only one type of filter can remove dissolved substances from water – an osmotic filter. Such a filter will give from 90% to 99% purity of water, depending on the filter.
It plays an important role in plant nutrition, and for hydroponics this phenomenon is even more important. Princeton University defines osmosis as the diffusion of molecules through a semipermeable membrane from a place from a higher concentration to a place with a lower concentration until the concentrations on both sides of the membrane equalize.
It may seem that the definition is difficult to understand. Here concentration is the concentration of water. And it is clear that if there is a lot of dissolved substances on one side of the membrane, then there is less water (dissolved substances take its place), and then the water will go from this side with a high concentration of water to the side where it is less, until it decreases and equilibrium of concentrations .
The phenomenon that causes water to flow through the membrane is called osmotic pressure, and it is important to remember that water on both sides of a semipermeable membrane always tends to equilibrium to the same concentration. The membrane retains the dissolved compounds, while water or other solvent passes. In plants or animals, cell walls play the same role as a semipermeable membrane. Even in medicine, the power of osmotic pressure is taken into account. Osmosis allows you to raise water along the trunk of a sequoia with its height up to 100 meters and this phenomenon is fundamental for the transport of nutrient solution inside the plant.
- Reverse osmosis filter
There is another phenomenon – reverse osmosis, or reverse osmosis water purification. In this case, everything works the other way around: water is supplied to the membrane under pressure. Water passes through the membrane regardless of the principle of osmosis, and the effectiveness of such a system directly depends on how high-quality the membrane is and also depends on pressure (more means better). Thus, a conventional filter gave water for washing; for a home, the reverse osmosis method for drinking water in a kitchen works under a pressure of 4-5 bar. To purify water in which 1100 mg/l of various substances are dissolved, 13 bar is necessary, and purification of water from the sea is at all 55 bar.
- Reverse osmosis filtration
This method of water purification could be considered excellent, however there is a significant drawback: each liter of purified water means from 2 to 4 liters of lost water. Such waste water can be used in the yard in the private sector. Or she just spills into the sewers. In addition, the membranes are fragile and deteriorate from phosphorus, from the high chlorine content, and calcium and magnesium, which make up the hardness of the water, accumulate and pollute the membrane. Most reverse osmosis systems are equipped with an additional filter to remove dust particles, equipped with a carbon filter for chlorine, and even sometimes with a water softener. And even with these shortcomings, it happens that osmotic filtration is the only acceptable option for obtaining suitable water for hydroponics.
Note that pure water filtered by osmotic systems is not suitable for hydroponics, since it does not have the necessary buffering properties, and even small additions of minerals will cause the pH to jump significantly. Purified water actively reacts which negatively affects the roots of plants.