Sewage Flow Meter-FAQ 

1. What is sewage treatment?

Wastewater treatment is an essential process for dealing with water pollution. It focuses on the treatment of domestic as well as industrial wastewater by physical, biological, and chemical methods to separate solid pollutants from the water and to reduce organic pollutants and eutrophic substances (mainly nitrogen and phosphorus compounds) in the water, thereby reducing pollution of the environment from the wastewater. The aim is to produce environmentally safe liquid waste streams (or treated effluent) and solid waste (or sludge treatment) suitable for treatment or reuse (often as fertilizer on farms), and the effluent can even be reused for drinking after multiple purifications to meet the standards for potable water.

In a sense, sewage treatment is also defined as wastewater treatment, including industrial wastewater purification. In most municipalities, a proportion of industrial wastewater containing organic pollutants and eutrophic substances is treated secondarily in wastewater treatment plants to reduce organic pollutant emissions.

2. What is the primary source of sewage?

Sewage mainly originates from domestic production and industrial facilities and includes domestic wastewater generated by toilets, kitchens, bathrooms, etc. In some areas, it also has industrial, medical, and agricultural effluents.

Today, there is the widespread use of separate treatment facilities for black and grey water from domestic sewage in developed and some developing countries. The treated greywater is generally re-collected to irrigate agricultural land and flush toilets.

Urban Runoff Sewage

Urban runoff wastewater includes both stormwater runoff and urban runoff. Sewer systems that treat both sewage and stormwater are generally referred to as combined sewer systems. Integrated sewer systems have been widespread use since the first urban sewer systems were established in the late 19th and early 20th centuries.

Initially, combined sewers were designed to allow wastewater to enter treatment facilities during droughts and allow excess water to be discharged directly into rivers, streams, or lakes without treatment during heavy rainfall. In practice, however, stormwater can mix with untreated sewage. For this reason, modern designs do not encourage the use of combined sewers and the gradual repair of existing integrated sewer systems to diverted sewer systems.

Industrial wastewater

Industrial wastewater treatment is an important measure. It recovers and treats industrial wastewater before it is discharged into the sewers. In this way, it reduces the pollutant content of industrial sewage and makes it less prone to odor. This technology is widely used in highly regulated developed countries. However, industrial wastewater is discharged directly into sewers or into the sea, lakes, rivers, etc. (known as receiving waters) without secondary treatment in many developing countries.

3. What is the treatment method for the sewage

There are many methods of treating sewage, which can generally be categorized as physical, chemical, biological, etc.

Sewage treatment plants: Some people survey more than 100 large treatment plants, there are more severe problems, such as insufficient funds, high costs, low efficiency, and other significant issues. The general efficiency is less than 70%, and the common is only 40%.

Sewage treatment cost energy consumption situation is high energy consumption, low efficiency.

In 2013 urban domestic sewage discharge has been the primary source of urban water pollution in China. Domestic sewage treatment is the current, and future urban water conservation and environmental protection work are the highest priority. This requires us to deal with the construction of domestic sewage facilities as an important element of urban infrastructure to grasp and is a matter of urgency.

With the development of science and technology, the direct use of sewage has become possible, using sewage source heat pump systems to use urban raw sewage.

The so-called raw sewage is the city’s direct discharge of untreated domestic and industrial wastewater. The current utilization stage is that raw sewage enters directly into the sewage source heat pump system for heat exchange, which cools and heats the interior of urban buildings while consuming a small amount of electricity. However, there are several technical difficulties to overcome in the reuse of sewage water: blockages, corrosion, and heat exchange efficiency.

A sewage source heat pump system consists of two parts: the sewage heat exchanger and the pump. The raw urban sewage enters directly into the sewage heat exchanger for heat exchange, and the heat exchanged is transferred to the room by the heat pump inside the sewage source heat pump.

The advantages of reusing raw urban sewage are energy saving, environmental protection, and no pollution.

3.1 How to treat sewage water in industrial processes?  

A method of treating industrial wastewater belongs to the field of wastewater treatment technology. It leads the sewage to the collection tank, adjust the pH of the last compartment of the collection tank, use the primary dissolved gas pump to lift to the direct pressure dissolved gas tank while inhaling air and coagulation decolorant, the primary saturated dissolved gas water in the immediate pressure dissolved gas tank is released abruptly to the prior air floatation tank to form the primary treated water; the direct treated water overflows into the buffer tank, and then in the pH control with the secondary dissolved gas pump to lift the primary treated water to the secondary pressure dissolved gas tank. The air and coagulation decolorizing agent are inhaled, and the secondary saturated dissolved air water in the secondary pressure dissolved air tank is suddenly released into the secondary air flotation tank to form secondary treated water and is discharged after overflowing to the sedimentation tank; the floating mud in the primary and secondary air flotation tanks is put into the floating mud tank, filtered into filter cake, and the filtrate is led back to the collection tank. The removal rates of CODcr, decolorization rate, S.S., and BOD5 of the industrial wastewater treated by this method are 80-90%, 95%, over 90%, and 75-80%, respectively, in line with GB8978-1996 Class, I water discharge standards. Biogas power generation is a new technology that integrates environmental protection and energy saving in extensive energy use. It uses the biogas produced by the anaerobic fermentation of industrial wastewater to drive the biogas generator set to generate electricity and can make full use of the waste heat from the generator set for biogas production so that the comprehensive thermal efficiency reaches about 80%, which is much higher than the general 30-40% efficiency of power generation. The economic benefits to the user are significant as an excellent way to treat industrial wastewater.

3.2  How do we treat sewage water for living sewage water?

3.2.1. Rural domestic sewage treatment methods

Domestic sewage → septic tank → anaerobic tank → artificial wetland (planted with plantain, water onion, calamus, and other plants with a well-developed root system, moisture-loving, and strong absorption capacity).

The method of “filtering” and then discharging is mainly applicable to rural decentralized domestic sewage treatment. The running cost is zero after completion, with a service life of more than ten years.

3.2.2. Urban domestic sewage treatment methods

Urban domestic sewage will be transported to the rural areas around the city, using the vast land to purify urban domestic wastewater. This will be an excellent way to eliminate the problem once and for all and kill many birds with one stone.

Take the example of a large and medium-sized city supplying 100W cubic meters of tap water for daily use.

The cost of an ordinary sewage treatment facility is 1000 yuan/cube. The construction cost is 1 billion and the annual operating cost is 100W cubic meters/day x 365 x 0.5 RMB/m3 = 180 million.Using the soil purification method, the construction cost is 1,000 yuan/cubic metre, and the annual operating cost is 100W cubic metre/day x 365 x 0.1 yuan/cubic metre = 0.4 billion. At the same time, it saves 360 million cubic meters of water resources for agricultural use, saves about 10,000 tons of fertilizer/year, and reduces the number of pesticides by 5 tons/year, so the overall benefits are considerable.

3.2.3. New technology of domestic sewage treatment: decentralized treatment

Domestic wastewater’s decentralized biological integrated treatment system is a new, economic, and environmentally friendly treatment system. The system has the advantages of low investment in equipment, low operating costs, and easy installation. It uses bio-enhanced technology to efficiently degrade pollutants so that domestic wastewater can be treated locally and nearby, and water resources can be recycled. As an effective supplement to the traditional sewage treatment plant, the system is gradually being widely used in urban residential communities, hotels, tourist attractions, new rural communities, and other areas.

Decentralized sewage treatment technology has a small footprint of equipment, no need to lay pipe networks, equipment integration, and other features, so the infrastructure costs and civil construction costs in the overall investment accounted for a relatively small, only about 30%. In comparison, about 70% of the investment is mainly used to purchase and install sewage treatment equipment.

4. What is a sewage flowmeter?

The sewage flow meter consists of a water level flow sensor (probe), an upper unit (terminal), and a communication cable. It is an instrument used to measure the volumetric flow of various types of sewage in pipes and channels.

5. How many sewage flowmeters are there in the market?

5.1. Electromagnetic flowmeter measuring principle

This method can be used if the sewage does not contaminate or adhere to the electrodes, but it should be used with caution.

5.2 . Doppler ultrasonic flowmeter measuring principle

This principle is suitable when the sewage contains a high level of sediment or air bubbles and the sewage is flowing in a full pipe.

Because if using electromagnetic flowmeter, the first few years will run well. After a few years, the reading will gradually become smaller, because the sewage is dirtier, which contains a large amount of sticky dirt,  it will stick to the electrode on the ground in the long-term operation, which results in electrode sensitivity being reduced, electromagnetic flowmeter will not work correctly.

If the use of external clamping ultrasonic principle, but also because of the tube wall sound conductivity is not good, the inner wall sticky dirt, sensor immersion in water pollution coupling agent and other reasons to affect the measurement effect.

The above problems can be effectively solved by using the insertion type Doppler principle. When the installation location is underground or submerged, please use an insertion type sensor with protection class IP68. If the pipe wall is cast iron, cement pipe, PVC pipe, corrugated pipe, etc., you can add optional holding hoops to ensure stable and reliable installation and operation.

5.3. Insertion type time difference type ultrasonic flowmeter measuring principle

When the sewage is relatively straightforward, without too many impurities or bubbles and other dirt, and is in an entire tube state of flow, suitable for the use of this principle.

5.4. Open channel measuring principle

An integrated level and flow rate sensor is used to measure both level and flow rate using the area and flow rate method. The accumulator then calculates the flow rate based on the cross-sectional shape, flow rate, and level information. Suppose the sewage flows through an open ditch. In that case, a suitable weir can be constructed and the level measured with an ultrasonic level meter, which is then converted into sewage flow by the accumulator.

6. What is the application of sewage flowmeter

Sewage flowmeter can be widely used for municipal water supply, steel, petroleum, chemical, electric power, industry, water conservancy, water resources, and other liquid volume flow measurement sectors, especially suitable for channels, small river flow measurement, and environmental protection treatment of sewage measurement.

Sewage flow measurement technology and instrumentation are used in the following areas.

6.1 Production processes

Flow meters are one of the significant categories of process automation instruments and devices. It is widely used in metallurgy, electric power, coal, chemical, petroleum, transportation, construction, light textile, food, medicine, agriculture, environmental protection, etc.  The application of sewage flowmeter can promote the development of industrial and agricultural production, save energy, and improve product quality as well as economic efficiency.

There are two main functions in process automation instruments  for flowmeter :

One is a detection instrument for process automation control systems and

Another is a total meter for measuring material quantities.

6.2 Energy measurement

Energy is divided into primary energy (coal, crude oil, coal bed methane, LPG, and natural gas), secondary energy (electricity, coke, artificial gas, refined petroleum, LPG, steam), and energy-carrying substances (compressed air, oxygen, nitrogen, hydrogen, water). Energy metering is essential for scientific energy management, energy-saving, and consumption reduction, and improving economic efficiency. Flow meters are an integral part of energy metering instruments. Water, artificial gas, natural gas, steam, and oil are all familiar energy sources that use many flow meters, which are indispensable tools for energy management and economic accounting.

6.3 Environmental engineering

The emission of flue gases, waste liquids, and sewage seriously pollutes the atmosphere and water resources and poses a severe threat to the human living environment. The country has made sustainable development a national policy, and environmental protection will be the biggest issue of the 21st century. In order to control water pollution, government management must be strengthened, and the basis of leadership is quantitative control of the amount of pollution.

China is a country where coal is the primary energy source, and millions of chimneys across the country are constantly emitting smoke into the atmosphere. Flue gas emission control is an important project to eradicate pollution, and each chimney must be installed with flue gas analysis instruments and flow meters to form a continuous casket emission monitoring system. However, flue gas flow is difficult because of the chimney’s large size and irregular shape, the variable gas composition, the wide range of flow rates, dirt, dust, corrosion, high temperatures, and the absence of straight pipe sections.

6.4 Transport

There are five modes of transport: rail, road, air, water, and pipeline transport. Although pipeline transport has been in existence for a long time, it is not commonly used. However, with the prominence of environmental issues, the characteristics of pipeline transport have attracted attention. Pipeline transport must be equipped with flow meters, which are the eyes of control, distribution, and scheduling and a necessary tool for safety monitoring and economic accounting.

6.5 Biotechnology

The 21st century will usher in the century of life sciences, biotechnology as the characteristics of the industry will gain rapid development. Many substances need to be monitored and measured in biotechnology, such as blood and urine. However, the instruments are complicated to develop and come in a wide variety.

6.6 Scientific experiments

Scientific experiments need not only a large number of flow meters and extremely complicated varieties. Although, according to statistics, a large part of the more than 100 flow meters are used for scientific research, they are not produced in large quantities and sold in the market. Many scientific research institutions and large enterprises have set up special teams to develop dedicated flow meters.

6.7 Seawater and lakes

These areas are open flow channels and generally require flow velocities to be measured and then flow rates to be derived. The physical principles and fluid mechanics underlying flow meters and flowmeters are common, but the instrumentation principles and structures and the conditions of use are very different.

7. What is the feature of the sewage flowmeter?

Sewage flowmeter is simple structure, solid and reliable, long service life.

No moving parts and resistance parts in the measuring tube, no pressure loss, no blockage

Reliable measurement, strong anti-interference ability.

It is small volume and lightweight.

It is easy installation and low maintenance.

A wide measuring range is not affected by changes in fluid temperature, density, pressure, viscosity, conductivity, etc., can be installed in the old pipeline on the open hole transformation. Construction and installation are simple, a small amount of work.

The general electromagnetic flowmeter cost and installation costs are low, especially suitable for measuring large and medium diameter pipeline flow.

Advanced processing technology, solid-state packaging, long life so that the instrument has good measurement accuracy and stability.

8. What is the technical parameter of a sewage flowmeter?

Flow rate measurement range: (0.001-10) m/s

Instrument accuracy: 1.0 grade

Working pressure: ≤1.6MPa

Medium temperature：0-80℃

Power consumption：﹤15VA

Protection grade： IP68

 9. What is the development of sewage flowmeter?

The development of flow measurement can be traced back to ancient hydraulic engineering and urban water supply systems. In the time of Julius Caesar in ancient Rome, orifice plates were used to measure the amount of drinking water for the inhabitants. Ancient Egypt used the weir method to measure the flow of the Nile around 1000 B.C. The famous Dujiangyan water conservancy project in China used the water level at the mouth of the Baobao to observe the size of the water, etc. In the 17th century, Torricelli laid the theoretical foundation for differential pressure flow meters, a milestone in flow measurement. Since then, the 18th and 19th-century flow measurement of many instruments began to take shape, such as weir, tracer method, Pitot tube, venturi, volume, turbine and target flowmeter, etc. Due to the process industry, in the 20th century, flowmeter has the rapid growth in demand for flow measurement in urban utilities. Before prompting the rapid development of instruments, microelectronics and computer technology significantly promoted flow measurement development. The rapid growth of microelectronics and computer technology has extensively promoted the renewal of the flowmeter.  So far, it is said to have hundreds of flowmeters to the market, the field use of many complex problems can be expected to be solved.

China was relatively late in developing modern flow measurement technology, and the flow instruments were imported from abroad at the beginning.

Flow and pressure, temperature are the three major test parameters. For a specific fluid, as long as we know these three parameters can calculate the energy it has, the measurement of energy conversion must be detected in these three parameters. Energy conversion is the basis for all production processes and scientific experiments, and therefore flow is as widely used as pressure and temperature instruments.

10. What is the installation requirement of a sewage flowmeter?  

1) Environment selection

It should be as far away as possible from equipment with strong electromagnetic fields, such as large motors, large transformers, large frequency converters, etc. The installation site should not have strong vibration, the pipeline is fixed firmly, and the ambient temperature does not change much (to prevent changes in the solid and liquid phases). The installation conditions need to be easy for installation and maintenance.

2) Location selection

The installation location must ensure that the pipeline is always filled with the measured liquid.

Choose a place where the liquid flow pulse is small and should be away from pumps and valves, elbows, and other local resistance parts.

When measuring two-phase (solid, liquid, and gas, liquid) liquids, the place where phase separation is not easily caused should be selected.

The inner diameter or circumference of the pipe is easy to measure, and the ellipticity should be small.

3) Length of a straight pipe section

The length of the straight pipe section on the upstream side of the sensor installation pipeline should be greater than or equal to 10D, and the downstream side should be not less than 5D (D is the diameter of the channel to be measured).

4) Flow control valves and regulating valves

A flow control valve should be installed in the measured pipeline on the upstream side of the sensor, and the flow adjustment valve should be installed on the downstream side of the sensor.

When measuring the flow, the flow control valve should generally be in a fully open state.