Wastewater accounting systems in non-pressure pipelines. Waste water flow meter and other metering devices

A.G. Popov, Ph.D., director of RANET ENERGO LLC

Business payments for dumping Wastewater getting bigger every year. Therefore, for the energy services of many enterprises, the task of organizing commercial accounting of waste and storm water is becoming increasingly important.

And, if during the installation and operation of metering units for energy carriers (thermal energy, steam, etc.) it has become customary for enterprises to comply with metrological requirements, to conduct periodic verification of metering devices, then during the construction and operation of metering units for wastewater, these requirements are often neglected.

Wastewater is discharged through non-pressure (gravity-flowing) pipelines or collected at sewage pumping stations and pumped through pressure pipelines.

AT this material Let us consider the features of the organization of wastewater accounting in non-pressure pipelines.

LLC "RANET ENERGO" began to design wastewater metering units and install flow meters since 1991, has accumulated considerable experience in performing such work at enterprises of various profiles (CHP; Vodokanals; large chemical and metallurgical plants, railway transport, etc. ) in different regions and climatic zones (including permafrost regions).

Such works are carried out in several stages: inspection of the object; development and approval of the project of the metering unit; construction of a measuring well; flow rate measurements; supply and installation of equipment; commissioning and commissioning.

The task of the survey is to determine the possibility and expediency of organizing accounting; choose the construction site of the metering unit and the type of metering device (flow meter); determine the scope of work in the construction of the metering unit.

What does the possibility and expediency of organizing accounting mean in this case?

Some enterprises discharge water so little that its level in the pipeline is several mm. At other facilities, wastewater outlets pass through dense urban areas (under buildings, roads).

In such cases, based on the results of the examination, a reasoned conclusion is issued on the absence of technical feasibility or inexpediency of building a metering unit.

When choosing the type of flow meter, we are not tied to a specific manufacturer or type of meter. The choice is determined by the features of the object. Domestic flow meters ECHO-R-02, foreign ISCO 4250, etc. are used.

Wastewater metering units are usually installed in measuring wells on existing sewer networks. Existing control wells are often used as measuring wells. In most cases, these are wrong decisions. Wells are placed in places where the direction or slope of pipelines changes. Therefore, when installing flowmeters in such wells, the requirements for the straightness of the measuring sections are violated.

In addition, the trays in the wells connecting the inlet and outlet pipes are not strictly circular. High humidity and dirt in such wells also do not contribute to the normal operation of the devices.

Therefore, it is necessary to build special measuring wells (chambers).

A serious problem in organizing wastewater metering in non-pressure pipelines is backwater and silting in pipelines. In the presence of constant backwater or siltation in the measuring section, it is difficult to speak of correct flow measurements.

Possible causes of backwater:

1. blockage - accumulation of deposits, debris in the pipeline;

2. pipeline collapse;

3. counterslope;

4. backwater from the side of the city collector (when the subscriber's pipeline is inserted below the water level in the city collector).

If the pipeline is clogged, the backwater is removed as a result of cleaning.

In other cases, as a rule, it is necessary to re-lay or repair the pipeline.

Silting of pipelines can occur as a result of:

1. partial destruction of pipes (soil begins to wash out);

2. small building slope;

3. sewage inflows of large amounts of sand, sand, etc.

The elimination of these causes is also usually associated with significant capital expenditures for the transfer or repair of pipes, putting the settling tanks in order.

However, if the company decides to organize wastewater accounting, it is necessary to carry out work to put wastewater outlets in order.

Let's give examples from practice. When carrying out work on organizing wastewater accounting at three outlets of the Torzhok Carriage Works, measuring wells were built, pipelines were cleaned of contamination, immediately after that, flow rates were measured, then flow meters were mounted and put into operation. However, according to the readings of the flow meters, the wastewater consumption was clearly overestimated.

An analysis of the situation showed that over the past 2 weeks after the cleaning of the pipelines, a sediment several cm thick appeared on the bottom of the pipes under the flow meters. The water level rose and the flow meters began to give overestimated water flow rates.

The pipelines were re-cleaned, but a few days later the sediment formed again. It turned out that the actual building slope on the outlets is noticeably less than the value of 0.007 set by SNiP, which led to rapid clogging of pipelines.

In such conditions, regardless of the choice of the type of device, it is impossible, in our opinion, to organize commercial accounting.

Some enterprises go to significant costs in the construction of wastewater metering units. For example, in Orenburg, Strela Production Association has 2 outlets DN 1000 mm. During the survey, it was found that in those places where it is necessary to build metering units (on the border of the balance sheet), there is a backwater in the pipelines as a result of partial collapse and clogging of pipes. The company replaced pipes and leveled the measuring sections, which made it possible to organize commercial accounting of wastewater.

Another problem arises already during the operation of metering units. This is a problem of imbalance when comparing enterprise data on water consumption and sanitation. For some reason, if an imbalance is detected, the enterprise, first of all, sees the reason for this in the wrong readings of the wastewater meter.

In fact, in our experience, the causes of imbalance are different:

1. unaccounted tie-ins (outlets) to wastewater metering stations;

2. ingress of ground and surface water into wastewater;

3. use of water supplied to the enterprise for technological needs;

4. incorrect calculation of the balance (for example, the water meter takes into account the incoming cold water, but reset is not taken into account hot water from the DHW system);

5. incorrect readings of water consumption meters;

6. incorrect readings of wastewater meters.

Item 6 belongs to the topic of this article, so we will consider this position in more detail.

Incorrect readings of the flow meter may result from deviations from metrological requirements (lack of straight sections, backwaters, pipeline deflections, pipe pollution) when choosing a location and building a metering unit. This is written above. Moreover, in these cases, the measurement error can be expressed not in units, but in tens of percent.

Another source of measurement error is the subjective factor when measuring the inner diameter of the pipeline, the flow rate. Indeed, it is difficult to accurately measure the inner diameter of a reinforced concrete pipeline, the inner surface of which has been severely worn over the years. Therefore, it is necessary to carry out measurements at the survey stage with special care, to comply with the requirements of the main regulatory document “Recommendations. GSI. Waste fluid flow in non-pressure pipelines. Measurement technique. MI-2220".

As you know, flow meters for pressure pipelines undergo metrological certification together with measuring sections. There are no such requirements for flowmeters for non-pressure pipelines. Therefore, enterprises operating such flowmeters, at the end of the calibration period for devices, send them for verification, and the measuring sections remain without control. Over the years, sediment appears in the pipelines, the walls of the pipes wear out, as a result, the characteristics of the measuring sections change significantly.

In our opinion, before periodic verification of flowmeters, it is necessary to carry out control measurements of parameters (internal diameter, level and flow rate) in the measuring sections. And if these parameters change, make appropriate adjustments to the settings of the flowmeters during periodic verification.

It is also necessary to periodically clean the measuring sections from deposits.

In general, it seems to us that wastewater accounting should be equated with energy accounting.

| free download Commercial accounting of wastewater - problems and features, Popov A.G.,

The amount of wastewater discharged by enterprises is the main indicator for calculation with specialized services. In particular, with Vodokanal. Which cleans and transports wastewater. And the amount of storm water is the only parameter for controlling emissions into the environment. It would seem that commercial accounting of wastewater is simply necessary for enterprises. After all, this is the only tool of control over this area. But enterprises are trying to do without the arrangement of wastewater metering stations.

Commercial accounting of wastewater: why is it necessary?

First, to save Money. Knowing about the excessive consumption of wastewater discharged, the company will look for ways to reduce their amount.

Secondly, to comply with the requirements of environmental organizations.

But the implementation of wastewater accounting is a technically complex solution and requires significant material costs. Moreover, enterprises are still skeptical about this kind of accounting. The main reasons for this:

• waste water is not an energy carrier;
• there is not enough control in the field of wastewater accounting.

No corresponding technical documentation, relevant specialists. But this state of affairs will not last long. Vodokanals are increasingly drawing the attention of enterprises to the need to equip wastewater metering units. Soon environmental organizations will acquire specialists and relevant documentation. It is possible that wastewater accounting will become mandatory.

How is wastewater accounting organized?

There are many examples where the readings of wastewater flow meters have enabled enterprises to take energy-saving measures and significantly reduce the amount of wastewater discharged. Despite the fact that the organization of commercial accounting is a technically complex and expensive task, enterprises go for it. Subsequently, the money resources will be returned in the form of saved funds for payment.

Basic requirements for installing wastewater metering units:

1. Organization of nodes on existing underground utilities.

2. Use of a non-pressure pipeline as a measuring section.

Reconstruction of the pipeline or its section is necessary in the following cases:

• small slope of the pipeline;
• backwater from the side of the collector;
• formation of soil sediment in the pipeline;
• lack of straight sections;
• inaccessibility of the pipeline (it passes under the road, embankment or building);
• little wastewater flow.

Types of wastewater meters

Modern flowmeters are suitable for pressure and non-pressure wastewater systems. The main types of devices:

• ultrasonic, magnetic-induction and vortex;
• portable and portable;
• electromagnetic, lever-pendulum and ring mechanical.

They differ in technical characteristics and principle of operation. When choosing, you need to consider the scope. Consider the features of some devices.

Ultrasonic metering device

Used in the following areas:

• open channels;
• gravity systems;
• sewer systems;
• non-pressure pipelines;
• treatment facilities for industrial enterprises.

Application area:

• commercial accounting of effluents;
• monitoring the filling of the sewer network;
• control over industrial discharges;
• analysis of the supply part of wastewater.

The method of operation is “area-velocity” (simultaneously measure the flow level and speed).

Main technical parameters:

• autonomous power supply from the network; the ability to take measurements remotely;
• amount of memory, but limited access to settings;
• measurement error - 0.1%;
• service life - 10 years;
• every 1-4 years an inspection is required;
• Russian-language interface and the ability to save readings on external media.

The price of a wastewater meter of this type is quite high. But the subsequent material and time costs convince of its greatest efficiency.

Lever-pendulum metering devices

Scope - sewer drains. The principle of operation is "area-velocity". By using this appliance heavily contaminated liquids can be measured.

Structural parts of the flowmeter:

• lever with spherical float (level transducer);
• suspension axis, on which the angle sensor is attached (determines the angle of deviation of the level transducer in relation to the horizon);
• rotary blade (speed converter);
• suspension axle with angle sensor for the turning blade.

The readings of this device are not affected by silt deposits and other factors.

Electromagnetic meter

Characterized by minimal electrical conductivity and measures the volume of wastewater, drinking water. Flowmeter Advantages:

• measurement stability, vibration resistance;
• ease of installation and management;
• no pressure loss, high reliability.

The permissible drain temperature for the operation of the device is 80 degrees. The principle of operation is based on the law of magnetic induction:

• a liquid passes through the magnetic coil, initiating the current;
• the current level is proportional to the wastewater velocity.

The electromagnetic flowmeter is the best value for money. To choose the right model, it is better to invite a specialist.

According to the legislation of the Russian Federation on energy consumption, wastewater accounting should be kept by organizations, owners of private houses and other housing and communal services. Controlling the amount of drains helps to reduce water costs and consumption charges.

When choosing a water meter for sewerage, do not forget to consider that the waste contains chemical compounds. Thus, a wastewater volume meter for efficient operation in an aggressive environment must have high technical parameters.

It looks like a flow meter (waste water meter)

Types and principle of operation

Exist different kinds meters for controlling the volume of wastewater intended for use in pressure and non-pressure sewer systems. According to the type of device and operation of devices, the following types of mechanisms are distinguished:

1. lever pendulum;
2. vortex;
3. ultrasonic;
4. electromagnetic.

Each type of water meter for calculating wastewater discharges differs in technical properties, mechanism of operation and scope. Consider the listed types of devices for accounting for wastewater in non-pressure pipelines and open systems, as well as installation instructions. This information will help you choose and install a do-it-yourself wastewater meter.

Electromagnetic devices

These are flowmeters with minimal electrical conductivity, which are used to determine the volume of water (effluents) in 2 directions. Their work is based on the interaction of an artificially created electromagnetic field with a moving fluid flow. In this case, the liquid must be electrically conductive. The electromotive force, which is directly proportional to the flow velocity, is converted into a digital signal. These are the counters.

The principle of operation of an electromagnetic wastewater meter

This type of flowmeter is widely used in industry. The main advantages are the absence of vibrations and pressure losses, ease of installation and maintenance, ease of control. High reliability and stability of measurements allow you to take the most accurate readings on the flow of sewage water.

Lever pendulum water meters

This water volume meter is used to measure the amount of wastewater discharged for metering in closed and open channels. The basis for determining the amount of liquid waste using this meter is taking into account 2 main parameters - this is the liquid level and the average flow rate.

The mechanism of action is based on the operation of a lever-float device, which shows changes in the level of water flow. The wastewater metering unit shows the amount of clean liquid and water with the presence of impurities.

Ultrasonic water meters

The wide application of the ultrasonic wastewater meter allows it to measure the level of waste liquids in the following types of systems:

• non-pressure pipes;
• industrial treatment facilities;
• autonomous sewers;
• gravity channels;
• open systems.

Water consumption is measured by passing it through ultrasonic vibrations and analyzing the acoustic data. To obtain indicators, the parameters of the area and flow velocity are used. Thus, ultrasonic wastewater meters allow for the following types of observations:

• tracking the process of filling the sewer;
• waste control;
• inflow analysis;
• sewer monitoring;
• commercial accounting of waste water.

The main advantages of ultrasonic flowmeters are the remote removal of measurements and their storage on the carrier, as well as the ability to account for wastewater in non-pressure pipelines, and limited access to adjusting settings.

Vortex devices

The principle of measuring indicators using a vortex flowmeter is based on measuring the frequency of pressure fluctuations. In general, these are universal instruments suitable for measuring the flow of liquids and gases. Exceptions are pipes with small and large diameters, as well as media with a wide temperature difference and high pressure.

Vortex flowmeter

Among the vortex devices for measuring wastewater flow parameters, there are several manufacturers that have proven themselves to be the most reliable and professional. These include devices of domestic brands Rise, Irvis, Amis and other firms.

Now consider the advantages and disadvantages of this type of water meters.

Vortex meters - average options measuring devices according to technical parameters, calculated on the volumes of liquid consumption industrial scale. They work in conditions up to 500 C and 30 MPa. This is one of the most suitable types of water meter for large enterprises.

Installation of metering devices

1. For accurate liquid flow measurement, the wastewater meter must have a filled measuring tube and the correct flow profile.
2. Installation of wastewater metering devices implies following the instructions of the instructions that are attached when purchasing it.
3. Following the requirements for the dimensions of straight sections at the inlet and outlet of the device, as well as instructions for the correct position of the device on the pipeline.
4. In case of vibration on the piping structure, it is necessary to choose the right place for the installation of the meter, since it should be where the magnitude of transverse vibrations relative to the measuring device will be minimal.
5. It is important to ensure that there is enough free space around the flow meter for easy maintenance when needed.

So, as you understand, the installation of wastewater meters requires special knowledge and skills, therefore, to perform quality installation contact the professionals.

Flow Profile

Manufacturers overview

• Takeoff. Russian meters are distinguished by their versatility, accuracy of results, high data stability, ease of use of devices, and durability.

• Danfoss. This is a joint production of Denmark and Russia. Flow meters of this brand are valued for the quality of devices, components and high accuracy of indicators.

• Dnieper. The company offers a wide range of sewerage meters, different in type of work and technical characteristics.
• Techno-T. The manufacturer offers meters for measurements on industrial enterprises for the technological and commercial purpose of flow control. Devices provide high informativeness, reliability, safety of operation.
• ZENNER. Leading manufacturing company measuring instruments. Large assortment, high parameters specifications, measurement accuracy.
• Signature. It produces wastewater meters Echo R-02 based on imported components with high technical parameters. The warranty period is 6 years.
• ZV Engineering. Produces STREAM meters with a mechanical method of calculation "area-velocity" in contact with liquid.

Installing water meters is already a common practice for property owners. This helps keep costs down as you only pay for the liquid you use.

In a private house, it is very important to install flow meters for sewers. They take into account only those wastes that go into the pipeline.

Photo: meters for accounting for wastewater consumption

AT country house there is a large consumption of water, which is used for watering plants, changing fluid in pools, fountains. It is also necessary for organizing watering places for pets.

Water is needed for household needs: washing carpets, cars, coverings around the house. It turns out that a very large flow of liquid occurs per day in private possessions, but only an insignificant part descends into sewer system. You have to pay for the entire volume.

To properly control the flow of water, you need to install wastewater meters. With their help, you can significantly reduce the costs associated with paying bills for sewerage.

Varieties

A modern sewer meter must be built to withstand chemicals and other aggressive particles.

Flowmeters are made from materials that are resistant to heavily polluted effluents.

Regardless of the type, each of them ensures the accuracy of measurements. The main types include:

• ultrasonic meters. They are products that are used to measure the depth of flows with straight-through elements. Measurements are made using sensors located in the device. Their installation takes place without serious installation work in the collector. To receive data from an ultrasonic meter, various types of communication are used: modem, cable, wireless;
• electromagnetic meters. Their work is due to the passage through them of a liquid with a magnetic field. Therefore, the liquid used must be conductive;
• lever-pendulum counters. They can be used to account for water in closed and open channels. The spherical float measures the level of waste, while the pivoting vane helps determine the speed of the fluid.

Stationary devices are listed above, if necessary, send them for repair, install portable products. They temporarily perform the function of measuring the liquid.

During the day, they run on battery power, at night they are put on recharging. With the help of an adapter, you can ensure the smooth operation of devices.

Ultrasonic

The main area of ​​application for flowmeters is the measurement of waste in a gravity pipeline or open ditch. The sensors of the device show high accuracy in measuring the flow rate of the liquid.

There are the following advantages of counters:

• measurements in pipelines of any diameter, including the largest with an indicator of 350 cm;
• extensive device memory;
• a variety of power supply methods: from the mains or batteries;
• long service life and minimum error in the issuance of data.

In turn, ultrasonic meters are divided into mortise and overhead. The latest flowmeters are best used for large diameter products.

The disadvantages of such devices include:

• complicated service. When using mortise sensors, it is necessary to carry out regular cleaning, and for overhead sensors, replacement of the acoustic gel is required;
• regular cleaning of the sensors after use in highly polluted drains.

electromagnetic

Not the last place among the counters is occupied by this type of product. They are chosen due to the following advantages:

• installation is easy, and maintenance is not difficult;
• devices are resistant to vibrations that occur inside the pipeline;
• are highly reliable and stable when taking readings.

Basically, their installation is carried out on pressure and gravity networks, provided that the operating pressure is below 40 bar.

Among the shortcomings of the products are the following factors:

• decrease in measurement accuracy with significant electromagnetic interference;
• different cost of the device, which completely depends on the diameter of the conduit;
• during measurements, it can give an error from 0.25 to 2%.

Lever-pendulum

These devices control the flow rate and liquid level in open channels or pipes. The lever helps to determine how much they have been filled.

Since it is equipped with a float, it will lower or rise as the flow changes. As a result, the position of the lever changes, and the liquid level is determined by the angle of its inclination.

The flow rate is determined in the same way, only a turning area is used as a meter. The speed of waste movement is determined from its angle.

A distinctive feature of lever-pendulum meters is high accuracy data during the passage of heavily polluted effluents.

Types according to the principle of action

The movement of wastewater occurs with the help of pumping equipment and free-flow - by gravity, when installing a pipe installation with a slope.

When using the first option, there are no problems with obtaining data. Therefore, any meters are used that are similar in type to devices for measuring water flow.

Effluents moving through a free-flow pipeline are more difficult to take into account. Since their movement is very slow and occurs under the influence of gravitational forces.

In such cases, various devices are used:

• performing only measurements related to the liquid level;
• capturing data on waste rate and level.

When choosing flow meters, one should take into account the estimated flow rate of wastewater, the planned speed of their flow and the amount of pollution in them.

Wastewater flow measurement

With the invention of modern equipment, new measurements have become possible that give data on the level of waste. The most popular acoustic or non-contact.

Equipment of this kind is produced in Russia and is widely used due to its low cost.

The flow is determined by measuring the water level, which is then recalculated according to a special "level-flow" formula, using graduated tables.

The level is known by obtaining data on the time during which the ultrasonic signal traveled from the primary transducer to the flow surface.

Important! Since speed is not explicitly measured, this can lead to inaccurate results.

• the ability to take into account flows containing aggressive substances;
• performance of work even with a small amount of effluents.

Among the shortcomings, the following points are distinguished:

• for correct measurements, the requirements regarding the mandatory length of straight sections must be observed. They must contain up to the primary converter 20 filling levels of the conduit, and after it - 10;
• creation of special conditions between the primary converter and the surface of the studied surface. The gaseous medium should not be vapor and foamy, as this affects the accuracy of the results and the quality of the signal penetration;
• the entire measuring area must be sloped;
• if the water flow stops or moves in the opposite direction, then the equipment takes this as a liquid flow;
• installation of equipment is associated with the installation of an additional structure - a well;
• the error is 3%.

Wastewater flow and velocity measurement

The data is taken using a two-channel Doppler method. To carry out measurements, primary level and speed transducers are mounted on the bottom of the conduit.

The results are obtained as follows:

• speed - using the Doppler method, penetration into the stream of an ultrasonic signal, which begins to be reflected. The sensor captures these changes and determines how fast the suspended particles are moving;
• level. It can be recognized hydrostatically (by applying pressure to the sensitive membrane with a column of water) or using an ultrasonic sensor.

The advantages of this method include:

• the ability to measure the flow in any direction;
• easy installation that does not require the installation of additional structures;
• versatility of use, can be used in pipes of any shape and with different sections.

Among the shortcomings, only frequent cleaning of the sensors can be noted. It is carried out only after measurements carried out in heavily polluted waters. The error can be from 1 to 5%.

How to Install a Wastewater Flow Meter

Proper installation of equipment is associated with compliance with the following rules:

• the cross section of the device must be filled with liquid;
• installation of the meter in the highest sections or low zones of the sewer pipeline should be avoided;
• The instrument must be on a straight line. Let's allow the angle of deviation horizontally, but not more than 25 degrees;

• when using non-pressure pipes, the flow meter should be located at the lowest point of the straight section of the sewer system.

When installing meters, it is better to turn to professionals, as incorrect actions lead to incorrect measurements.

As a result, this may not lead to cost savings, but rather provoke additional costs. When buying a flow meter, you can count on component parts in the form of blocks.

What problems can arise with the use of the device

When operating the device, the user may encounter reasons that affect its correctness.

The main problems include:

The appearance of backwater

They occur due to the following factors:

• the formation of blockages in the pipeline that arose due to the accumulation of large debris;
• as a result of the destruction of individual zones of the sewer line;
• if there is a slope in the opposite direction from the fluid flow;
• when inserting the device below the level of the wastewater surface in the collector.

Blockages in the system are eliminated; for other reasons, repair work is necessary.

Silting

• occurs when sand enters the pipes;
• non-compliance with the required;
• when soil enters through a damaged section of the pipeline.>

In order for the results obtained to be true, it is necessary to check the system for operability and, in case of malfunctions, eliminate them.

Prices for sewer meters

Overview of manufacturers

Depending on the tasks assigned to the meter, manufacturers produce various products for accurate measurements.

The most famous devices include the following flow meters:

• CJSC "Dnepr". Issues counters various modifications, which differ from each other in the principle of operation:
• Dnepr-7 01.011.1. It is used for pressure pipeline and operates on the principle of "area-velocity". The permissible diameter of products is from 20 to 1600 mm. The device can give an error in the region of 2%. Overhead sensors are used to operate the device;
• Dnepr-7 03.011.1. Mounted on non-pressure pipes. It can be used for products with a diameter of 100 to 1600 mm. The error is - 2%, the type of sensors used - overhead;
• Dnepr-7 03.071.1. The scope is open trays or gravity systems. The diameter of the measured products ranges from 200 to 1600 mm.

The received information is displayed on a USB drive, screen or computer.

• CJSC "Rise". The model with the designation RSL is used for a non-pressure pipeline and belongs to the "area" type of measurement. It can be applied practically on any products, the diameter of which is up to 4000 mm. Acoustic vertical sensors are used for operation, the device gives an error of 4%;

• Danfoss. Joint production of Russia and Denmark. Danfoss sewer meters are valued for high quality the products and parts themselves, measurement accuracy.

The cost of products is rather big, but it quickly pays off due to the correct calculation of the liquid used. Products have a long service life, while flow meters of many manufacturers need to be changed after 2-3 years.

• CJSC "TECHNO-T". Model Stream for non-pressure pipelines, used for products with a diameter of 10 to 3000 mm. Mechanical submersible sensors are used for operation, the error is 2%.

Should include installation of counters. Drainage systems should be taken seriously.

Important! The consumption of water leaving the sewer requires careful accounting, especially in large enterprises. This allows you to save money on bills, so the purchased equipment pays off quickly.

Video: installation of a water metering unit