Making a sand filter

Making a sand filter

Making a sand filter in practical terms in today’s water treatment units, filtration is a process during which sedimented particles or small clots that have not settled in the stages of coagulation and hardening are separated.

Filtration is one of the most basic methods for purifying water.

What is a sand filter?

Sand filters are tanks that are built and used under atmospheric pressure. This filter has cylindrical tanks that are made vertically or horizontally. The material of the sand filter body can be steel or galvanized sheet with epoxy coating or fiberglass.

Steps of water filtration

to split

When the suspended particles are uniformly in contact with the filter bed and the ratio between the diameter of the suspended particles and the material of the sand filter bed is known, the separation increases with the decrease in the diameter of the filter bed particles, and the larger the suspended particles are, the greater the separation and removal efficiency is. .

settle down

The important point in making a sand filter is that the sand filter can also remove particles smaller than the bed size. Removal of suspended particles smaller than the size of the particles is done by coagulation and sedimentation operations. In such a way that the suspended particles settle in the spaces between the particles of the bed and due to the gelatinous properties and stickiness of the other suspended substances, they also stick to themselves and thus cause the removal of suspended substances.


In the case of particles that are very small, they can be separated and removed from water by the process of penetration.

Biological activity

Some bacteria and microorganisms are active in the empty space between the sand filter bed. These microorganisms absorb the organic substances in the water while the water passes through the sand filter and turn them into harmless substances that form a layer on the filter bed.

Electrolytic action

Ionization theory can be true in water purification by filters. In this way, with the filter bed and suspended substances and water impurities, they have opposite electrical charges that when they are placed together, they neutralize each other, and this causes the creation of a particle that is stopped inside the filter bed and thus The arrangement of suspended substances and impurities is removed.

Making a sand filter
Making a sand filter

Types of water filters

smooth sand

The slow sand filter is used to purify water with a maximum turbidity of 30 NTU. But with waters with turbidity of 10 NTU, they have a longer life. Filtered water with a slow sand filter does not need special treatment.

In the slow sand filter, most of the filtration operations are performed by the first layer of bed sand. The removal of suspended matter and organisms is mostly done in the first layer. A slow sand filter requires a lot of land due to the low water flow rate. So Making a sand filter, the use of a slow sand filter is used in places where land is abundant and its price is low.

Sharp sand filter

The sharp sand filter is used for water filtration in water treatment plants. You can filter turbid waters from filter and filter sand 5 NTU or finally 10 NTU used. They use one or more layers of substrate in steep sand filter. At Making a sand filter A layer of anthracite or activated carbon can also be used to remove the color and taste of water. The water coming out of the quick sand filter should be directed to the disinfection and chlorination unit.

Sand filter under pressure

These types of filters are mostly used in small water treatment plants. Making a sand filter Under pressure, they are made in two categories, vertical and horizontal. The material of the body of pressure flat sand filters is iron with anti-corrosion coating or fiberglass.

فیلتر های شنی به شکل استوانه ای در دو حالت عمودی و افقی مورد استفاده قرار می گیرند و کاربرد آنها بیشتر در تصفیه خانه های کوچک می باشد. At In the construction of sand filters, a necessary space for the expansion of the silica bed during backwashing of the filter should be provided in these types of filters.

Types of sand filters

These filters are divided into two categories, metal sand filter and FRP based on the body material.

Metal sand filter

The material of the metal sand filter body is ST37 steel It is coated with epoxy and anti-corrosion. The inside and outside of the filter is covered with epoxy coating.

FRP sand filter

Making a sand filter Composite materials can be used, known as fiberglass sand filter or FRP. Inner cover of FRP sand filter made of PE in one piece without seams and food grate and the outer cover is made of composite materials with woven fibers of fiberglass.

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