Melted water and precipitation absorb chemical compounds and various solid waste from the surface of the earth. It is not permissible to dump into natural water sources pollution from industrial enterprises and highways accumulating in storm drains of large cities. Surface wastewater treatment plants free contaminated resources from sand, debris and oil products. Drinking sources should be protected from the discharge of toxic waste. Making wastewater safe for humans and the environment and preparing it for reuse with a rational attitude to natural resources is the task of local storm sewer treatment facilities.
Application area
Waste water is discharged into the wastewater system from industrial enterprises, gas stations, industrial sites and warehouses. Before this, the pouring line must be free from contamination at the local treatment facilities to a state that meets the sanitary standards of the Russian Federation.
Arrangement of city streets involves the collection and disposal of storm water from impurities. There are two types of VOCs used in the private sector: some for domestic wastewater and others for storm water. This is due to different requirements and appropriateness of the application. Rainwater drainage does not require biological treatment, like household waste.
Preparation of modern local sewerage systems is carried out in accordance with new requirements. Rainwater treatment technology is based on biochemical processes. The main selection criteria are determined by the conditions of its application and the nature of the contamination. Additional factors:
- laying depth;
- concentration of compounds;
- performance;
- SNiP requirements for the quality of discharged water.
At the heart of the reception of storm drains is a plumbing pipe system that collects contaminated water from storm water inlets - storm drains. Most often these are trays with gutters, which are laid along the road surfaces. Through them, the water rushes by gravity to the collector - distributor. Door pallets have become a type of storm water inlets, the task of which is to collect dirt from the feet of pedestrians. They are installed near the doors of the building or at the gates.
At the first stage of the drainage system, sand traps are designed to protect the treatment plant from mechanical clogging by stones, soil or debris. Mechanical sedimentation tanks do not allow clogging of the pipeline and manifold assemblies.
Types and sizes of systems
There are two categories of stormwater collection structures:
- closed, from sewage outlets through a pipeline in the ground;
- open, using ground gutters and ditches.
The cleaning system is a horizontal tank made of concrete, metal or fiberglass. The size of structures is influenced by:
- the area of the site from which rainwater is collected;
- the amount of precipitation in the region;
- place of discharge of clarified water.
Sometimes the composition of contaminants, depending on the type of object, requires additional cleaning.
The principle of operation of structures
Local cleaning devices (VOCs) are made in the form of modular units - oil sand catchers. The tanks receiving the drains have maintenance hatches.Modular devices remove garbage, hard-to-settle suspended particles of silt and sand, which are mechanical impurities with a density of 1500 kg / m3, and oil waste in the form of films on the surface of effluents, emulsions and residual conglomerates.
Factory modules have quality certificates and conclusions from the sanitary and epidemiological supervision. Designed to work for 10 years.
Cylinders made of low-pressure polyethylene are used, which make up the body of the device, which are durable and resistant to aggressive external conditions. The oil-sand trap performs complex wastewater treatment in several stages:
- In the sump, large particles fall out under the influence of gravity.
- In a thin-layer module, suspended solids that precipitate and drops of the primary emulsion that collect on hydrophobic plates are separated.
- The task of a sorption fibrous filter is in capturing oil products that have not lingered in a thin-layer module.
- A coalescent module made of polypropylene attracts residues of fuels and lubricants, repelling water.
Cleaning is completed in a filter with a carbon sorbent, which makes it possible to catch all types of oil products.
VOC design
On the territories of industrial facilities and gas stations, melt and rainwater accumulate in tanks, then they are pumped out and taken out of the limits for discharge into the ground or water bodies.
The design of local treatment facilities begins with determining the volume of precipitation and the uniformity of their receipt. The choice of modules is influenced by the composition of impurities in the effluent, the depth of soil freezing and the level of soil water. An error in design can lead in the future to flooding of the site and destruction of the soil structure. The presence of underground utilities in this area is taken into account.
A storm sewerage scheme is being drawn up: the location of channels and troughs for draining sediments, pipelines for redirecting effluents to treatment modules. If the system is designed according to the principle of gravity, without the installation of pumping equipment, installation should be carried out with an angle of inclination, depending on the diameter of the pipes.
In accordance with SNiP, in the design of rainwater treatment facilities, a sanitary protection zone (SPZ) is taken into account for the arrangement of the sewage system. It is designed to protect the pipeline from damage, as hazardous wastewater can get into drinking water sources and to the surface of the earth. The distance to the sources should be at least 50 m, and the security zone on both sides of the sewer pipeline should be 5 m each.
In private buildings, they began to install flow-through septic tanks. They are made from several connected sedimentation tanks and a drainage section, or they are purchased as a finished product.
Manufacturing plants offer the design and manufacture of devices for indoor and outdoor sewerage, connecting fittings and pipes, water purification systems from iron.
How to determine performance
To calculate the volume of a structure, use the data:
- the level of precipitation in 20 minutes, depending on the region (determined by SNiP 2.04.03-85);
- the area of the terrain or the projection of the roof when calculating a point rainfall.
The calculation involves the surface absorption coefficient depending on the type of surface: for asphalt pavement - 0.95; for concrete - 0.85.
Installation of systems
Installation of storm sewers is carried out in accordance with the project. If there is a need to insulate the pipeline, the depth of the trench should take into account the sand cushion (20 cm) and the thickness of the insulation made of insulating materials.
Foreign objects are removed from the trench: stones, roots. A pit is being prepared for treatment devices - it can be a local block-modular installation made of plastic or a structure made of concrete. A pipeline is laid in the pit and trenches, a cleaning device is installed and the system is connected using fittings.
Inspection wells are provided every 10 m in areas with a flat surface and at every turn. A sand trap is installed in front of the pipeline at the outlet of the collector. After joining, the joints are sealed. Before backfilling the trench, the system is tested: several buckets of water are poured out. If there are no leaks, the trench is closed.
In areas of uneven terrain, there are problems with connecting to a common highway, since there is no necessary pressure for gravity. In these cases, it is envisaged to install wells to extinguish the sewage pressure.
If there are no drains, to prevent leakage under the house, gutters are installed to collect rainfall, covered with gratings and connected to the storm sewer system.
The rain shower is not connected to the general sewage system, since it contains chemical compounds that are unsuitable for biochemical water purification. In the private sector, this is also not recommended, so as not to overload the sewer system. They try to fulfill VOC in a private house in accordance with environmental safety requirements.
