What filters will help clean water from iron?

A safe amount of iron in water is in the range of 0.1-0.3 mg / l, but in practice its content can be 10 times higher. In this regard, questions arise: how to purify water from iron, is such purification mandatory and how to determine the composition of water?

Iron in water can be in various forms:

• divalent (soluble);
• trivalent (insoluble);
• organic: soluble (polyphosphates), bacterial and insoluble (colloidal).

To choose the right clean system, you need to know not only the level of iron, but also its shape.

How to determine the concentration of iron in water?

In a centralized water supply system in a city, the reason for the increase in iron is always steel water pipes. Simply put, rust from a pipeline mixes with water, but does not dissolve. The easiest way to detect the presence of rust (ferric iron) is to let the water settle in any transparent container. If after a few hours a reddish precipitate forms at the bottom, it is time to take safety measures and purify the ferric iron from the water.

Tip

A rusty coating on the washbasin, bathtub or toilet bowl is a clear indication that rust from pipes gets into your faucet. With these "symptoms", you need to proceed from diagnosis to resolving the problem.

From artesian wells, water enters the house with dissolved iron (divalent). An increase in its level can be determined visually - the water becomes a little yellowish. But color change does not always occur. In this case, a weak solution of potassium permanganate will help. If the pink solution is added to water with a high iron content, its color will change to yellowish-brown.

Colloidal iron may be present if the fence is taken from a shallow well where surface water enters. In this case, the settled water will be unclear, a suspension of molecules of such iron does not settle to the bottom. If a film forms on the surface of the water, there are iron bacteria in the water.

If the tap water has the above characteristics or a metallic taste, you need to choose a cleaning system. To do this with maximum efficiency, it is necessary to take the water sample to the laboratory. Having the results of the research on hand, it is possible to choose the deferrization system correctly.

Cleaning methods

There are two types of methods for removing iron and its compounds from water - reagent and non-reagent. If reagent filters are used, it is necessary to monitor their replenishment.

Filtering can be performed in the following way:

• aeration
• ion cleaning;
• membrane, including osmotic cleaning;
• ultrafiltration;
• sedimentary filtration;
• mechanical cleaning.

It should be noted that a universal method that cleans all types of contaminants does not exist. That is why it is so important to determine what type of pollution is present.

Mechanical cleaning

Mechanical filtration systems (mechanical cartridge filters) have proven themselves. They are suitable if you need to clean the water from large fractions of insoluble iron (rust). To remove oxides, propylene cartridges and cartridges with fine granulite are used.

They are mainly used in apartments and houses with a centralized water supply, since it is impossible to purify water from a well using this method.Rather, mechanical filters are also used in cottages, but with preliminary oxidation (aeration) of metal compounds.

The method of mechanical cleaning with macro filters (the size of the detained particles is more than 15 microns) is used to pretreat the water. Cartridges with 5 μm cells are installed for fine filtration.

Tip

Prefiltration or a coarse filter delays coarse fractions, so that fine-mesh cartridges last much longer.

Ion filtration

Water purification using ion exchange is a reagent method that allows you to selectively change the ionic composition of water. If the task is to remove iron, then catalytic resins with various fractional additives are used as ion exchangers in the filters. They replace metal ions with sodium ions.

The reagent medium loses its ability over time, but can be restored. For this, use citric acid or table salt (solution). The advantage of this method is that iron removal does not entail the precipitation of hardness salts and removes not only rust, but also metals dissolved in water, including manganese. The disadvantages include the fact that catalytic resins are restored under the influence of a salt solution only partially, and after 2-3 years they completely exhaust their resource.

Aeration

In the water supplied from an artesian well, there are various metal compounds, including divalent iron in a dissolved state. Since it is impossible to purify water from a well qualitatively without preliminary oxidation of ferrous iron, the method of aeration, i.e. saturation of water with oxygen, is used. As a result of this, the metal passes from a dissolved state to an insoluble oxide, and after that it can be removed using a mechanical or other filter.

Aeration can be carried out both by pressure and non-pressure methods.

1. In case of pressureless aeration, water is fed into an oxidizing tank, in which spraying and showering takes place. Showering is done using nozzles or an injector. Oxides accumulate at the bottom of the aeration tank, and it must be periodically cleaned - from two to five times a year, depending on the degree of water pollution.
2. Pressure aeration is carried out in a static mixer or aeration column. They are a contact chamber into which water is supplied (about two-thirds filled), and air is supplied through the tube to the mid-column / mixer level. Thus, bubbling of saturated air mixture by bubbles and oxidation of ferrous iron occurs. In addition, an additional (secondary) aeration occurs in the column at the border of water and air, increasing the quality of cleaning.

Reverse osmosis

The reverse osmosis treatment system is the most advanced fine filter with pre-treatment. Using reverse osmosis membranes, high-quality filtration of drinking water from all impurities occurs. A prefilter integrated in the system traps insoluble metal particles with a fraction of more than 0.5 microns and inorganic iron dissolved in water.

The main cleaning step is carried out by a membrane with pores of 0.0001 μm in size, under the influence of the pressure difference. As a result, pure water molecules are separated from water of increased density (saturated with organic compounds of iron and other pollutants), which merges into the drainage system. The disadvantage of the reverse osmosis filter can be called only its low performance. However, this degree of purification is needed only for drinking water and water for cooking, and reverse osmosis can easily cope with such a volume.

Backfill filter with backfill system

Backfill filtration refers to sedimentary and reagent methods. It is necessary for water treatment of water from wells when the aeration method is not suitable for technical reasons or is insufficient.As a filtering medium (backfill), branded materials Birm, Manganese Greensand, MTM, Pyrolox are used. Filling reduces the time required for oxidation by hundreds of times.

Automatic cottage deironer is arranged as follows.

• The filter housing - the cylinder - is filled with filter medium.
• An automatic machine with a timer and a flowmeter is installed in the upper part of the case. Its function is to change the direction of water after a given time during filtration and regeneration.
• Inside the container, a water pipe passes through the entire backfill layer.
• The flexible tube connects the reagent tank.

During the filtration cycle, water passes through the backfill, rises upward through the riser pipe and leaves the treatment system. When the regeneration cycle begins, water is supplied to the water tube from above. She loosens the filter bed and leaches the iron compounds settled there. After that, the machine will perform a reagent treatment of the filter medium, which restores its chemical activity.

What to choose?

To choose the right filtration system, as mentioned above, you need to do a water analysis in the laboratory. This will be much cheaper than selecting a filter by trial and error, and will also help establish the optimal filtering system. The installation of filters also depends on the purpose for which water is needed.

Fine filters are unnecessary when it comes to preparing water for domestic (washing, shower) or technical needs. But for drinking water, their presence is mandatory - depending on the results of laboratory tests.