Horizontal sand trap, like any other, is intended for the treatment of wastewater from mineral impurities. It is important to note here that a separate process for the allocation of mineral and organic impurities is relevant due to the fact that in this case the operating conditions of those facilities that are engaged in further water purification and removal of sediments are facilitated.
General description of the device
The principle of operation of such equipment is quite simple. It is based on the fact that mineral particles, which are pollutants, move with water. Those particles whose specific gravity is greater than the specific gravity of water precipitate to the bottom. Sand traps are usually designed for a speed of water at which only the largest particles of the mineral type fall out.
Speaking in numbers, then horizontal sand traps and any other types are designed to retain sand with a particle size of 0.25 mm or more. It was experimentally proven that for the optimal operation of such a device, the horizontal water flow velocity should be at least 0.15 and not more than 0.3 m / s. If you exceed the maximum speed, then the sand simply will not have time to settle in the sand trap. If the speed is too low, then organic matter will be precipitated along with mineral impurities, which is undesirable.
To date, horizontal sand traps of two types are used - with rectilinear or with circular motion of water. There are also vertical views in which fluid moves up. The latter type is a screw device, the use of which is carried out rotational-translational movement of the liquid.
The main details of the horizontal device
To date, the most widely used sand traps are of the horizontal type. This equipment consists of such basic working elements as the working part, in which the flow of water moves, and the second part is sedimentary, designed to collect and store precipitated sand until it is removed.
The calculation of the horizontal sand trap is a set of formulas that allows you to calculate all the necessary parameters. For example, the flow rate is Q = 130,000 m 3 / day. In order to determine the flow rate of wastewater per second, the following formula is used:
q sec = 130,000 ÷ (24 * 3600) = 1.5 m 3 / s
For a complete calculation of the installation uses a large number of various calculations.
Instrument Design Features
If we talk about the design of the horizontal sand trap, then this is a rectangular tank with a sedimentary part at the beginning. The design and modification of the sand trap greatly affects the movement of fluid inside the device. However, despite the change in the flow, the speed should always remain such that only sand is deposited, and the remaining contaminants pass further.
As for the horizontal sand trap with a circular motion of water, it is more complicated in design than with a rectilinear movement of water. But at the same time it takes up much less space, and is also more convenient to use. The sump in this unit is made in the form of a round gutter. The gutter itself is located exactly in the middle of the sand trap, and wastewater is supplied from one side.
Rectilinear designs
As for the horizontal sand trap with a rectilinear movement of water, this is the most simple design of those used. In this case, structurally, the sand trap will consist of two separate parts. The first part is the passage, where waste water flows, and the second part is a sump for collecting sand. Most often, with this design of the unit, the sump is installed as close as possible to the beginning of the sand trap. This is justified by the fact that the maximum performance when cleaning the liquid is observed at the very beginning.
In order to remove sludge from the sump, grabbers, hydraulic elevators, sand pumps can be used. It is worth adding that sand is not toxic and after passing through special procedures it can very well be used to sprinkle paths, when planting forests, etc.
Aggregate Design
If you look at the scheme of the horizontal sand trap, you can easily understand that it has a rectangular section. The design of such equipment is based on what kind of particle size must be delayed. It is worth adding here that, in addition to mineral pollution, organic substances are also retained, whose hydraulic fineness coincides with the fineness of sand.
When considering the sand trap drawing, you can see that such a device has a wide entrance and a rather narrow exit. A rain collection bin is usually located below, under the bottom of the sand trap itself. However, in some cases, it may well be located above and above it.
Here it is worth saying that there is a maximum time that wastewater can be inside the sand trap. This indicator is thirty seconds. Due to a similar time limit when designing sand traps, they are always calculated based on peak indicators of the flow rate of the waste fluid. Given all these parameters, you can easily calculate the desired surface area of the device.
Based on the surface area, as well as the length of the sand trap, you can easily calculate the width of the tank. In order to constantly maintain the same speed of movement of water when using a horizontal type sand trap, the pipeline is equipped with drain holes.
Additional Features
In addition to the parts listed above, any device has mechanisms that are responsible for supplying the mineral phase to the hopper for collecting sludge. All these devices are divided into two types: chain and cart. They can be seen in some drawings of the horizontal sand trap.
If we talk about the first type of device, then it is an endless chain that moves along the bottom of the hopper in the direction opposite to the direction of water movement. The return movement of the chain is already carried out above the sand trap. Sand is removed using scrapers.
As for the second type, these are small carts that move along two or one rail rail in the bottom of the unit. Sand is removed from the hopper using a scraper that attaches to the bottom of the cart.
Other sand removal methods
In addition to the methods described above, a hydromechanical method of purifying water can be used. It is usually used in sand traps of horizontal radial or tangential type with rotational and tangential movement of wastewater. Most often, such devices are only used to extract small amounts of sediment.
With this design, sand will be removed using a pipeline that is laid along the bottom of the sand trap and also has injection holes. Similar holes are directed towards the hopper. In this case, the sediment, that is, sand, will liquefy somewhat, entering a semi-liquid phase. With this movement, the substance will also entrain the upper layers of the precipitated mineral phase. In order to get rid of additional moisture in the sand, it is removed from the hopper using a screw type conveyor.
Devices with aeration
There are also horizontal devices with aeration of tangential type. These are sand traps with the same design as the previous ones, but additionally having aerators, and the cell size is from 3 to 5 millimeters.
Due to the aeration process, the sediment is characterized by lower humidity, and it also contains fewer substances whose density is less than the density of sand. These advantages have arisen due to the fact that the wastewater stream performs both translational and rotational motion.
You can purchase horizontal sand traps "EcoTech" in Moscow. The company manufactures such devices in Russia.