Sewage drains: types, accounting and disposal

07-05-2018
Outdoor sewage

Sewage drains are an unavoidable by-product of any production. And not only production: the village house near Zhmerinka, the Admiralty in Petersburg and Buckingham Palace in London are united by the fact that they, yes, produce wastewater.

Have you ever wondered where these drains go then? This article, in fact, is dedicated to the story of how to dispose of them.

Laying sewer.

Classification

Wastewater is classified by a number of signs. The method of disposal depends on their origin and composition. What options are possible?

Origin

  • Industrial effluent. They often contain toxic or corrosive substances. Depending on the composition, they can be disposed of directly in production or merged into the general urban sewage system.
  • Domestic wastewater most dangerous in terms of biological contamination: organic matter is a breeding ground for countless types of bacteria. They are disposed of by municipal sewage treatment plants.

To clarify: where there is no central sewage, wastewater is either periodically discharged to wastewater treatment plants by sewage transport or disposed of on-site after the separation of solid fractions.

  • Surface wastewater (rain and melt water) are discharged through the storm sewer system. As a rule, rain sewage and drains discharge water into any local water body without prior purification: their degree of contamination is not higher than that of rain water that flows naturally into the same water body.
The contents of the stormwater is dumped into the pond or on the relief without cleaning.

Composition

If the composition of domestic wastewater is more or less constant, then in the case of industrial effluents it is more and more difficult.

It is worth highlighting:

  • Mineral water;
  • Organic contaminated drains;
  • Mixed pollution.

In addition, the cleaning method is largely determined by the degree of contamination: the amount of impurities at 200 mg / l and at 30,000 mg / l obviously require a fundamentally different approach.

Severely polluted effluent.

Of course, it influences the choice of cleaning method and the content of toxic substances, acids, alkalis, the presence of specific odors.

We present an approximate composition of wastewater for a factory for the primary processing of wool for the production of fabrics.

Description Content, mg / l
Dense residue 33500
Of them - insoluble mist 28,000
Ammonium Nitrogen 210
Fat 7800

This is far from the worst possible option; however, drains with such a composition, obviously, cannot simply be dumped onto a relief or into a body of water.

Accounting

In the case of domestic wastewater, their quantity with the minimum error is equal to the water consumption, which can be easily taken into account by water meters. As a rule, the owner of a private house is billed a total bill - for water consumption and drainage services.

The cost of wastewater services is determined by the indications of a water meter.

With enterprises, everything is much more complicated. In addition to the fact that many of them use their own water intakes, the volume of wastewater often correlates non-linearly with the amount of water consumed. At least due to the fact that the water used in some technological processes for cooling slightly less than completely turns into steam.

At the same time, those enterprises whose wastewater composition makes it possible to dispose of them through a common sewage system create a serious burden on municipal wastewater treatment plants. It is logical to keep records of sewage with special devices. How are they arranged?

Non-pressure systems

In the gravity sewer, the sewage meter is a device for measuring the instantaneous level of liquid in a pipe of known cross-section. Knowing the level at any given moment, it is easy to calculate the average consumption per unit of time.

Several physical mechanisms can be used to measure the level of wastewater:

Scheme Description
Ultrasound The liquid level affects the acoustic characteristics of the pipe: the speed of propagation of oscillations in water and in air varies. Logging the lag will give a reliable picture of the current fluid level.
Electromagnetic Contaminated high-salt liquid is an electrolyte capable of interacting with the electromagnetic field of the instrument. According to his changes can be judged on the flow of waste.
Leverage Technologically, this method of measurement is the simplest: the liquid level is measured by the position of the float connected by a rocker arm with the measuring part of the device.
Ultrasonic flow meter.

Curiously: the result of measurements performed by any of the above methods will be reliable only with a perfectly clean pipe. The accumulation of solid fractions, silting and any other obstacles in the path of the liquid will cause the device to show overestimated values.

Pressure systems

How can a meter work on pressure sewage?

Just as a measuring instrument on any water supply main.

What does a pump do to pump sewage?

  1. Crushes coarse fractions;
  2. It creates excess pressure in the pipe.

Bernoulli's law will help us further: static pressure in a fluid flow is inversely proportional to its speed.

A clear demonstration of the action of the law of Bernoulli.

It is enough to pass the drains through a tube of variable diameter - and by the change in pressure in it it will be possible to estimate the flow velocity. At a known speed and cross section, the calculation of the fluid flow is a matter of a minute.

Cleaning

How are drains of different composition cleaned?

City Wastewater Treatment Plant

First, we will get acquainted with the stages of cleaning domestic wastewater discharged into the city sewer.

  1. Wastewater passes through coarse filters - grates, sieves and sand traps. Screened coarse fractions are transported to landfills of municipal solid waste or are disposed of together with precipitates that are discharged later. Sand can be used for road works.
  2. Fat traps collect fat from the surface.
  3. The next stage is a sump. In a few days of being in it drains, all suspensions precipitate and are collected from the bottom by scrapers; light pollution is driven to the bunker by a float.
Pools - sumps on wastewater treatment plants.
  1. Liquid waste undergoes biological treatment. Simply put, the organic matter remaining in the water is devoured by anaerobic (methane-consuming in the life process) and aerobic (oxygen-consuming) bacteria. In the latter case, the water is forcedly aerated.
  2. The so-called physico-chemical treatment allows removing solutions of potentially hazardous substances from water. There are a lot of ways; The most promising at the moment is filtration through a molecular membrane that allows molecules of a strictly defined size to pass through.
  3. The last stage is disinfection. The goal is to destroy colonies of pathogenic bacteria that can lead to outbreaks of epidemics among people, domestic and wild animals. Tools - UV irradiation of water and chlorine treatment.

Industrial effluent

For the treatment of industrial wastewater, in addition to those already listed, several more solutions can be used.

  • Aggressive substances are often neutralized by the corresponding reagents. So, for waste with a high content of acids, caustic soda can be used as a neutralizing additive.
  • Thermal utilization of waste containing hydrocarbons involves spraying and burning them in furnaces and burners. Water evaporates, and potentially dangerous components decompose to carbon dioxide and water.
The work of the flare for the incineration of liquid waste.
  • Toxic suspensions can be separated from the waste by centrifugation: they settle on the walls of a drum rotating at high speed.

Autonomous sewage

How is sewage treatment in a private house?

The most effective solution is a compact station for biological treatment of sewage effluents using aerobic decomposition. It allows you to achieve a degree of purification of 95-98%.

In the photo - the station of deep biological treatment Oasis.

The principle of operation seems familiar to us:

  1. In the two chambers of the settling tanks mechanical waste separation is carried out.
  2. Purified from sludge and light fractions wastewater enters the aeration tank, where the air supplied by the compressor stimulates the multiplication of a colony of aerobic bacteria. Part of organic matter is oxidized, part is devoured by bacteria.
  3. Purified water is used for irrigation or simply dumped onto the relief.

The price of a deep cleaning station, however, is not to be liked by every cottage owner. Hence the popularity of hand-made sewer septic tanks.

Instructions for their construction is quite simple:

  1. Wastewater is directed to a settling tank (or several consecutive bulls). For several days they are there, separating into light, heavy fractions and relatively pure water.
  2. Then, the water collected from the middle of the tank of the settler is sent to the soil after-treatment - absorbed into the soil below the surface level.

The septic tanks need to be cleaned periodically, but it is required only once every one or two years.

Scheme of a two-chamber septic tank.

Conclusion

Of course, a small article does not claim to cover all possible methods of cleaning liquid waste. As usual, the reader can find additional information in the video in this article. Successes!