Wastewater and its classification

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

The sewage disposal system and all facilities used for these purposes are part of engineering devices, the purpose of which is to improve the city, residential or industrial complex. If we describe a liquid of this type, then it can be characterized as follows. This is water that was used for some purpose, after which its properties were significantly deteriorated, and it became unsuitable for further use.

General description of the concept

Most often, those liquid flows that have had their initial properties changed become wastewater. Most often, such changes occur due to the fact that a variety of impurities get into the composition. In addition, this class also includes those waters that are removed from cities and towns with the help of sewers or flow down from any industrial enterprise.

If we consider the type and composition of wastewater, they can be divided into three categories: domestic, industrial, atmospheric.

Description of the household type of liquid

Household wastewater is those streams that have been polluted as a result ofpractical activities and life of people. Most often in the water of this category there is a high content of mineral and organic impurities. If we talk about mineral mixtures, then this is most often ammonium, chlorides, etc. Of the organic substances, the presence of nitrogen-free and nitrogen-containing components is most often observed. Most often, these substances are presented in the form of proteins, fats or carbohydrates. Less often, but still there are impurities in the form of microorganisms or viruses and bacteria that carry a variety of diseases.

Types of industrial effluents

If we talk about wastewater of the industrial category, then the nature of the industrial enterprise that creates these effluents plays an important role here. Depending on this, they can be divided into several groups.

The first group is a liquid containing impurities of inorganic origin. These compounds carry a variety of special toxic substances. These can be effluents from electroplating companies, construction companies, mineral production plants, and others. Waste from these enterprises changes the pH structure of the water. Wastewater with this structure contains heavy metal s alts. These substances are considered toxic in relation to the possible inhabitants of the reservoir where the waste water will descend.

There is a group of waters that contains inorganic compounds that are considered non-toxic. The effluents of such waters create such plants as cement,ore-dressing and others. The waste from this industry is not considered too dangerous for the waters where the water flows.

Another category is industrial wastewater containing organic non-toxic elements. The food industry is characterized by such waste. These can be factories for the production of dairy, meat, microbiological and other products. When such a liquid enters a reservoir, such a parameter as oxidizability increases significantly.

The last group, which is considered the most dangerous, is a liquid containing organic elements with special toxic substances. Waste of this type is characterized, for example, by the oil refining industry. It is also worth adding here those factories that produce sugar or canned food.

Consumption rates

Wastewater treatment methods are also of different types. The presence of several options is due to the fact that for each industry it is necessary to have its own method. A variety of scientific methods are used to develop an appropriate cleansing method. Another important condition is that the enterprise must consume exactly as much water as is necessary for its operation, so as not to create excess contaminated fluid.

Determining the rate of water consumption

The first thing to do in order to choose a wastewater treatment method is to determine the veryliquid consumption rate for a plant, factory, etc. There are two ways to do this: scientific and reasonable calculations, or best practice. There is also the concept of integrated water consumption by an enterprise.

However, the definition of the norm is only suitable for industry, but what to do with atmospheric precipitation, which wash away all the dirt from the street, and then carry it through the sewer and drain it in a certain place? To influence these factors, it is necessary to periodically carry out dry cleaning of the street. However, it’s worth saying right away that this will not solve the problem 100%. In any case, polluted water from roads, which carries particles of organic matter, biogens, oil products, and metal s alts, will enter atmospheric groundwater.

Description of city waters

In practice, such a concept as urban wastewater is often used. This category most often combines domestic and industrial flows. It is worth paying attention to the fact that industrial, domestic and atmospheric water can be discharged separately or together. All-alloy and separate structures have become the most popular wastewater systems. The advantage of using the first category of the system is that it will not be difficult for it to remove any kind of polluted water from the city through sewers. Most often, such networks lead to treatment plants and facilities. As for separate systems, there are several pipeline networks, each of which moves a different type of liquid. For example, on the firstrain and unpolluted water can be transported through the second channel, and water with various harmful impurities can be transported through the second channel.

What criteria influence the selection of a diversion system?

When choosing a network for cleaning, the following parameters must be taken into account: the substances of wastewater contained inside the composition of the liquid, the technical, sanitary, and economic component of the enterprise is evaluated. It is also necessary to provide for the intensification of the activity of the selected object.

In order not to make a mistake with the choice of a drainage system, it is also necessary to determine such a value as the maximum allowable discharge (MPD). This term is understood as the mass of elements contained in water that can be allowed to be removed through the selected system and in the selected mode per unit of time. This is important to ensure the water quality standards at the checkpoint.

Most often, pollution of water bodies, lakes, etc. occurs due to the fact that sewage from industrial enterprises is discharged here. The discharge of contaminated liquid may cause changes in some physical properties, such as temperature, odor, etc. In addition, such places almost immediately become unsuitable for public water supply.

Issue Watch

Of course, there are certain conditions for the release of dirty water into the reservoir. The main criterion is the national economic significance, as well as the nature of use. After the release of contaminated liquid, the quality of water in the reservoir deteriorates significantly. Therefore, release is allowed only ifthis does not affect life in the reservoir too much, and also if it does not harm future fish breeding in this place. In addition, the possibility of further use of this reservoir as a source of water for supplying the population should remain.

Fulfillment of all requirements of this kind is monitored by the sanitary and epidemiological service. Another important point is that the rules for the conservation of water bodies are not uniform. It all depends on the purpose for which the storage will be used in the future. Thus, there is the first group, which includes reservoirs that should remain suitable for centralized and non-centralized water supply to the population. The second type is the preservation of the reservoir for swimming, recreation and sports. Sanitary stations classify all bodies of water into one of these two groups.

Water self-purification process

Today it is known that such a process as self-purification of water in a reservoir is possible. This is understood as the flow of hydrodynamic, chemical, microbiological and hydrobiological reactions, due to which the liquid returns to its original state.

However, in order to achieve this result, it is necessary to comply with certain restrictions on the discharge of wastewater. First, the release of contaminated water should not disrupt the functioning of other facilities. Secondly, the waste liquid must not contain substances or impurities that can clog or even deposit inside the pipes. In the event that the production-type wastewater does not meet these requirements, then it first passescleaning at the station, and only then descends into the reservoir.

Mechanical cleaning process

Mechanical wastewater treatment is used if there are insoluble mineral or organic masses in the water. Most often, this process is a preliminary way to purify the liquid. The use of this method is resorted to before proceeding to the main ones. If you follow this procedure in accordance with all the rules, then you can achieve that the amount of suspended solids will decrease to 92%, and organic - up to 23%.

Mechanical water purification systems include devices such as filters, grilles. Suppose a common thing is a sand trap, which is designed to separate large mineral impurities from a liquid, in this case sand. Here, equipment such as an averager is used. This device is able to regulate the composition and flow of waste water.

Such objects as primary settling tanks are widespread, where heavy mechanical impurities can be separated from the water with the help of gravity, which settle to the bottom of the settling tank. In order to purify the water coming from oil refineries, special oil traps are used. This is a special rectangular tank where oil products are separated from water. Here the principle of the difference in density of these compositions is used.

Biological wastewater treatment

It is worth noting here that the biological purification method requires additional costs, but it is used quite widely. During this procedure, all organic compounds present in the water begin to oxidize. Special microorganisms are used to perform this operation.

Biological wastewater treatment can be carried out both in natural conditions, that is, in the fields of irrigation, filtration, etc., and in special systems, for example, in a biofilter. This creates a favorable environment for the development of special microorganisms, which significantly speed up the purification procedure. However, the creation of such conditions will require additional financial costs.

Chemical and physico-chemical methods

These methods of fluid purification have gained the greatest popularity and importance when working with industrial wastewater. These methods can be used both separately from the others, and in conjunction with mechanical or biological ones. For example, there is a neutralization procedure that is used in cases where it is necessary to purify industrial wastewater from the acids contained in it. Most often, this method is used in order to avoid the development of corrosion inside metal drainage systems. It also helps to avoid disruption of the biochemical processes taking place in the reservoir.

Precipitation

Sewage sludge is a suspension that is separated from a contaminated liquid by mechanical, biological, chemical or physical-chemical treatment.

There are several types of sediment that remain after cleaning. Belonging to a particular species depends on what kind of equipment or method was used toimprove fluid quality. Coarse impurities remaining on the grates are referred to as waste. The heavy impurities that remain in sand traps are sand. Floating impurities remaining in the sedimentation tanks are classified as fatty substances. There are also sediments dried on silt beds. There are quite a few of these types. Discharge of sewage into water bodies should be carried out only after removal of such sediments.