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Ultrafiltration and Microfiltration Solutions for the Biosciences

Water filtration, purification and treatment

What is called “filtration” is the process of removing medium-sized suspended particles from water. To name just a few of the elements that filtration eliminates, we find: sand, silts, rust particles, hemp scraps, etc.

To filter water, it must be circulated in a filtering body: a sieve, membranes or a brush for example, in which water can pass freely, but which blocks the particles in suspension, previously mentioned.

Filtration using screen filter

Water enters the system from the left side (for example) and exits from the right side. In between, it passed through the sieve that can be seen through the transparent bowl (in full in the image below). The water has passed, the impurities have remained in the filter.

The valve that we see under the bowl allows the filter to be drained: by passing the water against the current, we clean the screen, the stored impurities are then discharged from below.

Water filtration using the brush filter

in a brush filter, the water flows against the current through a steel brush. Unwanted elements suspended in water are then captured by the fibers, as in sieve filters. In addition, the gas microbubbles naturally present in water are also captured by the brush, and gather there. to form larger ones.

When these bubbles are large enough, they rise thanks to Archimedes’ push to the top of the filter, where there is a degasser. When the pressure is high enough there, it automatically ejects the accumulated gases. As for the screen filter, a purge system is provided.

Membrane filtration

this process consists in circulating the water to be treated in a multitude of fibers, which are called “membranes”. These can be likened to optical fibers, with a small internal diameter, the inside of which is lined with microscopic pores, which let through only the water and the essential minerals it contains.

These membranes have a filtration threshold of 0.02 µm. As such, we can consider that membrane ultrafiltration is a purification process, as it is precise. Viruses, bacteria and various pollutions of small or very small size will be filtered in this system.

It should be noted however that a coarser pre-filtration is necessary upstream of the membrane filter, which is not not designed to block oversized particles.

Purification & potabilization of water

“We call “purification” the process or processes which allow the elimination of various pollutants of small or very small size: viruses, bacteria, heavy metals, drug residues, pesticides, nitrates … and also some radioactive elements.”

To purify water different processes and systems exist:

Activated carbon

Activated Carbon

certain so-called “active” coals have numerous microscopic cavities. When contaminated water is brought into contact with these coals, the various harmful elements that it contains will be absorbed in these cavities.

In addition, the negative ions present in the water will be electrically attracted by the positive ions present on the coals. This purification is very precise, since it eliminates unwanted particles up to 0.02 microns.

Ultra Violets

Ultraviolet purification destroys bacteria, viruses, fungi and algae. It consists in applying an ultraviolet radiation on a portion of transparent tube, this radiation kills, or at least neutralizes the micro-organisms.

Again, this is a purely physical process that does not add anything to, or take anything away from, the water. It should be noted, however, that an electrical connection is necessary to use the ultraviolet purification.

Membrane filtration

This process consists in circulating the water to be treated in a multitude of fibers, which are called “membranes”. These can be likened to optical fibers, with a small internal diameter, the inside of which is lined with microscopic pores, which let through only the water and the essential minerals it contains.

These membranes have a filtration threshold of 0.02 µm. As such, we can consider that membrane ultrafiltration is a purification process, as it is precise.

In fact, viruses, bacteria and various small and even very small pollutions will be filtered in this system. It should be noted, however, that a coarser pre-filtration is necessary upstream of the membrane filter, which is not designed to block particles of too large a size.

Reverse osmosis

Reverse osmosis, like filtration processes, involves passing the liquid through a filter body, in this case it is a semi-permeable membrane. However, in the case of reverse osmosis, the membrane has extremely small pores, on the order of a thousandth of a micron, which allows almost only the molecules of water to pass through.

Reverse osmosis filtration procedure

Nitrates, pesticides, bacteria, microbes, asbestos, herbicides, limescale, mercury, lead etc. cannot cross this membrane. But this filtration cannot be done alone, it is necessary to force the passage of water in the body by applying a strong pressure to it, without which the molecules of water themselves do not cross the membrane.

Treatment of limestone and tartar

Limestone, also called “tartar”, is formed from calcium and magnesium naturally present in water. The most commonly heard form of limestone is of course encrusting limestone. In fact, under “normal” conditions of temperature and pressure, this limestone is deposited in the pipes and plumbing elements. We then have high pressure losses, even the complete cut off of water circulation, energy losses, we can have mechanisms that break or can no longer rotate, leaks etc.

This is particularly true in pipes where the water is hot, in heating circuits for example, in water heaters, coffee makers etc. In addition to these mechanical consequences, tartar is an ideal habitat for bacteria that live in pipes, and it can cause irritation of the skin, hair and eyes.Fortunately, to fight tartar, different solutions exist. On the market there are, among other things, magnetic systems, softeners, and systems using galvanic electrolysis by sacrificial anodes. You will find below a table presenting these different solutions.

Corrosion treatment

Corrosion: Corrosion comes from a chemical reaction between water, the gases present in water and the metal of the pipes. This reaction destroys the piping inside. We can then have water leaks, flow losses, and the proper functioning of the mechanisms (valves, valves etc.) becomes impossible.

To completely prevent corrosion, you should have no gas, no metal, or no water. It is therefore impossible not to have corrosion, unless using 100% plastic piping, or not to circulate water there. (Gases are always present in the water).

On the other hand, even if it is impossible not to have corrosion, it is possible to protect the piping: by using sacrificial anodes, in zinc for example. Since their electrochemical potential is lower than that of the materials used for plumbing, they degrade slowly, instead of piping.

The efficiency of this process can be increased by galvanic electrolysis: by circulating water at sufficient speed in a dielectric material, the charges of the suspended elements are disturbed, which can then coagulate. Under these conditions, it is easier to remove suspended metals.

By itself, you could almost consider this solution as “chemical”, since zinc ions are added to the water, however, this element is quite healthy. Zinc ions are found in plum pies, for example.

The use of a degasser, if possible associated with a hydrodynamic reactor, also makes it possible to greatly reduce the gas content, and therefore the phenomenon of corrosion.