Sewage treatment plants are used to treat industrial, surface and wastewater. According to the standards prescribed in the legislation of the Russian Federation, before dumping sewage or polluted water into rain or city sewers, a number of special measures are necessary. Their ultimate goal is to bring the quality of the purified liquid to the established levels.
Application area
Local treatment facilities for storm drains are used in industrial plants, various industrial sites, gas stations, warehouses, etc., in settlements in places with residential buildings. In addition, such systems are also used on roads to pump water from their surface. Depending on the type of wastewater pollution, different requirements are imposed on their quality of treatment. The highest degree of contamination of effluents is considered to be oil products and various suspended solids.
No one doubts that the treatment facilities for storm water are very important. This is especially true for areas where wells are located, since these systems not only process water in a special way and make it safe for the environment, but also prepare it for reuse.
The selection of such systems is determined by several factors:
- depth of pipelines;
- the concentration in the water of any pollutants at the entrance to the system itself;
- the performance of treatment facilities;
- the established degree of purification, which meets the standards for the discharge of such waters into the city sewer or any other water body.
Types and size of systems
Conventionally, storm water treatment plants can be divided into two categories:
- Closed systems. This means that water through pipes and traps enters directly into the storm water inlet and is discharged through pipes to places where either discharge or storage occurs.
- Open systems. In this case, water accumulates and flows down the surface of the channels and troughs to the places of its discharge.
Such systems of treatment facilities are most often produced in the form of horizontal tanks using various materials, such as concrete, fiberglass, low pressure polyethylene or metal. As for their size, they directly depend on the area from which run-offs run, as well as on the weather conditions of a particular region, places of discharge of treated water and the type of facility itself.
A combination of a gas trap and a sand trap is usually installed. Their sizes can be very different and for the convenience of their installation and delivery they are often placed in one housing. If the effluent is discharged into open water bodies, then in addition to the oil and gas separators, coal additional treatment units are also used, i.e., sorption filters.
Systems and their passport
Block-modular treatment facilities for storm drains are performed in the form of a special installation - a sand-oil catcher. Through the hatches made in these tanks, they are maintained. Passing through modular purifiers, surface waters get rid of oil products and various kinds of mechanical impurities. The first of the above types of pollution includes conglomerate sediment, film, primary and secondary emulsions, and the second includes hard-to-sediment particles, silt and sand with a density of more than 1500 kg / m, as well as debris that floats on the surface.
It should be noted that factory production systems always have a passport for storm water treatment plants, certificates of conformity and sanitary and epidemiological conclusions. In addition, the manufacturer must guarantee the tightness of the housing. Usually it is 10 years.
What is a sand trap and how does it work
This product is a cylinder, often made of low pressure polyethylene. This gives it extraordinary strength, resistance to adverse environmental conditions and the ability to easily tolerate the influence of various aggressive environments.
The operation of a sand-oil catcher consists of five degrees of wastewater treatment:
- Sedimentation tank. At this stage, the primary rejection of large particles occurs, which under the influence of gravity fall to the bottom.
- Thin layer module. It separates suspended solids, as well as their oil conglomerates, into a precipitate, and a primary emulsion floats to the surface, merging into droplets and collecting on hydrophobic plates.
- Sorption filter. Its task is to capture particles of oil products that do not fall on hydrophobic plates located on a thin-layer module. The sorption fibrous filler, which is located in the filter housing, is housed in a high capacity and has significant selectivity to heavy, medium and light oil products.
- Coalescent module. It contributes to the separation of particles of oil products that float to the surface, the size of which is more than 0.2 mm.
- Charcoal filter aftertreatment. It is filled with a special sorbent selective to all petroleum products.
Design
As you know, in the territories of enterprises and stand-alone gas stations there is a constant accumulation of rain and melt water, which must be removed and dumped outside the ground or in any body of water.
To determine which treatment facilities are needed, you need to know the following data:
- uniformity and volume of wastewater;
- composition of impurities and effluents;
- groundwater and land parameters.
Designing sewage treatment plants for production sites requires, first of all, to determine which group this facility belongs to. There is a specially developed classification of the VODGEO Research Institute, dividing them into two groups. The first includes surfaces and enterprises, drains from which are similar in composition to the waters of residential areas. This means that they contain toxic and other specific elements.
The second group includes those territories of enterprises from which surface runoff with similar harmful impurities can occur. After that, the type of the technological scheme itself is chosen , and at the end, calculations are made and suitable sewage treatment plants are determined.
Necessary calculations
The calculations differ from each other depending on the specific selection of components. When using a flow diagram without the use of an averager, the structure is selected by determining the flow rate of storm drains. To do this, you need to know the statistical characteristics of rain in a particular village, as well as the SNiP coefficient that determines the surface of the water. When the calculation of storm water treatment plants is ready, finally choose the appropriate model of the system.
Performance
It is worth noting that the efficiency of the structures is very important, since untreated melt and storm water can be extremely dangerous for buildings and structures, as well as for the entire territory of the enterprise. Harmful chemical impurities contained in wastewater can damage the waterproofing, and this is fraught with the destruction of foundations and underground utilities. Moisture, accumulating on structural elements, contributes to the appearance of fungus, which in turn can cause irreparable harm to them. Therefore, the efficiency and productivity of storm water treatment plants is very important not only due to the fact that environmental authorities require this, but, by and large, based on practical considerations.
Installation of systems
There is a certain order in which the treatment facilities are installed. First of all, with the help of technology or manually tear out several trenches and pits of the required size. Sometimes, if necessary, their bottom is concreted. After that, all the treatment components are installed in previously prepared places accordingly, and then the structural elements are insulated and waterproofed. The last stage of work is backfilling the soil.
It is worth noting that the successful design of treatment facilities largely depends on the correctness of the necessary analyzes, studies and calculations, since even a small error can contribute to the flooding of the site and damage to the treatment system itself.