Blowers for aeration in wastewater treatment. Types of compressors for VOCs, their interchangeability. Compressor for wastewater treatment plants Blowers used in wastewater treatment plants

Regulating the air supply in aeration tanks at wastewater treatment plants is an opportunity to effectively save electrical energy.

The control object is the cleaning process Wastewater using bacteria contained in activated sludge. Wastewater is supplied to the aeration section, where activated sludge with bacteria is located. To activate bacteria and mix the sludge mixture, air is supplied to the section from turbo blowers. Monitoring of the content of dissolved oxygen in aeration chambers is carried out by laboratory analysis, on the basis of which the air supply to the aeration chamber is regulated by the system shut-off valves in manual mode.

This system is complex in terms of requirements for control algorithms due to the influence of a large number of factors:

Amount of oxygen supplied;

Behavioral ambiguities biological system activated sludge;

Ambient temperatures;

Degrees of concentration of pollutants in wastewater and other structures.

In general, the description of such systems does not fit into traditional models of automatic control theory due to factors whose influence is almost impossible to predict. For example, air density and air compressibility depend significantly on temperature, and therefore air supply control loops must be adjusted depending on environmental conditions.

Continuous monitoring of dissolved oxygen concentration in aeration tanks is the key high-quality cleaning and reducing energy consumption on blowers. The existing equipment at the enterprise (TV-175 turbo blowers) and the method of laboratory measurement of dissolved oxygen concentration are obsolete and create the problem of high instability and excessive consumption of electrical energy

Today, the most advanced is an automatic regulator in combination with an aeration blower for biological wastewater treatment and a continuous oxygen measurement system. The performance of such installations is controlled by means of a diffuser guide vane with adjustable blades or an inlet guide vane with preliminary swirling of the flow, and a combination of the two mentioned systems is also possible. A continuous oxygen measurement system consisting of a primary transducer with a sensor immersed in water, as well as a secondary transducer using modern technology microprocessor signal processing generates a signal in accordance with the concentration of dissolved oxygen, which enters the air injection unit, and then the amount of air entering the aeration chambers automatically changes.

In accordance with the methodology for calculating the specific air consumption per volume of incoming wastewater, the amount of air supplied to the aeration rooms was determined to be 18030 m 3 /h.

Let's calculate the specific air consumption for the volume of incoming wastewater 28000 m 3 /day.

Specific air flow

where: q 0 – specific consumption of air oxygen per 1 mg of total BOD removed.

For complete purification of BOD20, 1.1 is taken.

К 1 – coefficient taking into account the type of aerofek, we take 2.0 for the first stage, 1.95 – for the second stage;

K 2 – coefficient depending on the depth of immersion of the aerator:

2.08 = first stage;

2.92 – second stage

Kt - coefficient taking into account the temperature of wastewater

K t = 1+0.02·(T w -20), where: T w is the average water temperature over the summer period;

K 3 – water quality coefficient, assumed for municipal wastewater to be 0.85.

C a – solubility of air oxygen in water, mg/l;

Tables of air oxygen dissolution in Lex water - BOD 20 in purified waste water, taking into account the decrease in BOD during primary sedimentation. Data on BOD 20 were obtained from information on the qualitative composition of standardly treated wastewater, by the testing laboratory of KZHUP "Unicom": BOD half post. 53.9 mg/l, BOD, pur. 5.1 mg/l.

K t = 1+0.02 · (22.1-20)=1.042

C a = 1+· C t, where: N – immersion depth of aerators, m;

C t – solubility of oxygen in water. (We accept according to table 27, Vasilenko. Water disposal. Course design).

Cal = 1+ 8.83 = 10.12

q airl = 1.1 = 18.75

q airll = 1.1 = 12.16

Daily air consumption based on specific flow rate is determined by the formula:

Q = q air + q average day , m 3 / day,

where: q air - specific air consumption;

q average day - average daily flow rate of wastewater entering treatment, m 3 / day (28,000 m 3 / day).

Q I = 18.75 14000 = 262500 m 3 /day

Q II = 12.16 14000 = 170240 m 3 /day

Let's determine the hourly air flow

Q 4 I = =10938 m 3 /h

Q 4 II = =7093 m 3 /h

The total consumption is

O p = Q 4 I + Q 4 II = 10938 + 7093 = 18031 m 3 / h

Thus, the required amount of air supplied to the aeration chambers will be 18031 m 3 /h.

IN currently The following injection equipment is installed:

1. turbo blower TV-175 with a capacity of 10,000 m 3 /h – 2 pcs.

2. TV-80 turbo blower with a capacity of 6000 m 3 /h – 2 pcs.

3. TV-80 turbo blower with a capacity of 4000 m 3 /h – 2 pcs.

To obtain the calculated specific air flow, it is necessary to turn on at least two blowers: one TV-175 blower with an installed electrical power of 250 kW and one TV-80 blower with an installed electrical power of 160 kW at rated load.

Taking into account the physical and moral wear and tear of the injection equipment, operating since 1983, it is proposed to install a single-stage centrifugal compressor with a multi-blade open turbine-type impeller in combination with an air supply control system using linear servomotors with the following requirements and indicators of technological equipment:

Initial data

To ensure an air supply of 12,000 m 3 /h, it is necessary to turn on two TV-80 blowers with a total power of 320 kW.

The installed electrical power of the existing process equipment is 320 kW - at 12000 m 3 / h

The installed electrical power of the new process equipment is 315 kW - at 16,000 m 3 / h, and at 12,000 m 3 / h - 249 kW.

We determine the annual electrical energy savings when installing new equipment:

E e = (320 - 249) 0.75 24 365 10 -3 = 466 thousand kWh or 130.5 tce

The cost of saved fuel at a price of 1 ton of fuel equivalent = $210 (according to the Department of Energy Efficiency):

C = 130.5 · 210 = $27,405 = 232,942.5 thousand rubles.

Payback period for the event:

where K is capital investment in the event, 2,000,000 thousand rubles;

C – savings from implementing the event, thousand rubles;

T = == 8.6 years.

Note: Clarification of all amounts of capital investments for the implementation of the proposed measures and payback periods is carried out after the development of design and estimate documentation

Aeration systems, which are equipped with industrial and local treatment plants, are designed to artificially enrich wastewater with oxygen, which oxidizes iron compounds and other impurities. For this purpose, a special vacuum equipment, meeting certain standards and requirements. In particular, treatment plants install aeration blowers of various capacities, making the cleaning process efficient and environmentally friendly. The Megatechnika MSK company is ready to supply interested enterprises with equipment with the parameters you need on favorable terms.

Basic requirements influencing the choice of blowers for water aeration

Natural aeration of water is an indispensable condition for the proliferation of aerobic bacteria that purify water; in nature it occurs continuously. However, an intensive, forced aeration system requires much larger volumes of air, for which a rotary or turbine type water aeration blower is used, which meets such parameters as:

• the ability to supply dry air, free of microparticles of lubricant, wear products or other harmful impurities, around the clock;
• maximum quiet operation;
• nominal productivity corresponding to the volume of processed waste;
• resistance to corrosion, temperature changes and precipitation;
• simplicity and simplicity in maintenance, operation, durability, reliability and energy efficiency of the design.

What types of blowers are there for aerating wastewater treatment plants?

There are submersible type blowers, which do not require additional cooling systems, and centrifugal blowers, with multi-stage compression. For small ones treatment facilities We recommend equipment that forces air into the pneumatic system using a screw block. The operating principle of the compression chamber of rotary blowers eliminates the possibility of contact of oils with air, and the compressors themselves are characterized by a particularly low level of noise and vibration, efficiency and compactness, which is important when locating treatment plants near residential areas. For large treatment complexes industrial enterprises Compressors that compress air by moving pistons are more suitable.

We will find the most effective solution for you!

The Moscow company "Megatechnika MSK" offers a wide range of blowers for aeration of wastewater treatment plants or artificial reservoirs, with parameters specified in each specific case. The possibility of changes in equipment performance is also taken into account, which is associated with possible seasonal fluctuations in the volume of wastewater, and, as a consequence, differences in compressed air consumption. At competitive prices, we will equip your enterprise with screw (rotary) or piston blowers from reputable manufacturers that are popular in the global and Russian markets. All you need to do is submit an application online, and our experts will contact you to clarify the details.

Yu.V. Gornev ( CEO Vistaros LLC)

It is a well-known fact that from 60 to 75 percent of the energy consumption of sewage treatment plants (STPs) of cities and large industrial enterprises comes from supplying air to the aeration system. This article discusses the issues of possible savings in energy consumption in the aeration system through the use of energy-efficient elements of the system.

The reserves for saving energy consumption in the WWTP aeration system are enormous; they can be 70% or more. Let's consider the main elements of this system that significantly affect energy consumption. If we omit such issues as the need to maintain air supply pipelines, etc., in good working condition, then these include:

1. Availability of primary settling tanks at WWTPs, which allow reducing the Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) of wastewater at the inlet of aeration tanks. As a rule, primary settling tanks are already present at most large WWTPs.
2. Introduction of the nitrification-denitrification process, which allows increasing the amount of dissolved oxygen in the return activated sludge. This process is increasingly being introduced during the construction and reconstruction of WWTPs.
3. Timely maintenance and replacement of aerators.
4. The use of controlled blowers of optimal power, the introduction of a unified control system for all blowers.
5. The use of specialized controlled valves in the air distribution system for aeration tanks.
6. Introduction of a control system for each valve and all valves based on data from dissolved oxygen sensors installed in aeration basins.
7. Application of air flow meters to stabilize the air distribution process and optimize the minimum dissolved oxygen level setting for the valve control system.
8. Introduction into the control system of additional feedback from the ammonium sensor at the outlet of aeration tanks (used in certain cases).

The first two points (primary settling tanks and the introduction of nitrification-denitrification) relate largely to issues of capital construction at WWTPs and are not discussed in detail in this article. Below we discuss the implementation of modern high-tech modules and systems that make it possible to achieve a significant reduction in electricity consumption at WWTPs. These modules and systems can be implemented both in parallel with the solution of the first two points, and independently of them.

The main consumer of electricity in the aeration air supply system is the blowers. Their right choice is the basis of energy saving. Without this, all other elements of the system will not work desired effect. However, we will not start with blowers, but will follow the order in which it is necessary to select all modules.

Aerators

One of the main characteristics of aerators is the specific oxygen dissolution efficiency, measured as a percentage per meter of immersion depth of the aerators. For modern new aerators this value is 6% and even 9%; for old aerators it can be 2% or lower. The design of aerators and the materials used determine their service life without loss of efficiency, which for modern systems ranges from 6 to 10 years or more. The choice of design, number and location of aerators is carried out according to such parameters as BOD and COD of wastewater at the entrance to the aeration system, the volume of incoming wastewater per unit time and the design of aeration tanks. If we are dealing with the reconstruction of a WWTP with very old aerators that are in poor condition, then, in some cases, only replacing the aerators and installing blowers corresponding to the new aerators will reduce energy consumption by 60-70%!

Blowers

As mentioned above, blowers are the main element that ensures savings in energy consumption. All other elements reduce the need for air supply or reduce resistance to air flow. But if you leave the old uncontrolled blower with low efficiency, there will be no savings. If several uncontrolled blowers are used in an aeration station, then, theoretically, by optimizing other elements of the system and achieving a reduction in air supply requirements, it is possible to decommission and transfer to reserve several blowers from those previously used and, thus, achieve a reduction in energy consumption. You can also try to compensate for daily fluctuations in the aeration system's oxygen demand by simply turning the backup blower on or off.

However, much more effective is the use of a controlled blower, or more precisely, a block of several controlled compressors. This makes it possible to provide air supply in exact accordance with demand, which varies significantly throughout the day, and also varies depending on the season and other factors. The usual constant supply of air from uncontrolled blowers is always excessive and leads to excessive energy consumption, and in some cases to disruption technological process nitrification-denitrification due to excess oxygen in aeration tanks. At the same time, the lack of air supply leads to pollutants in the wastewater outlet of the WWTP exceeding the maximum permissible concentrations (MAC), which is unacceptable.

Precise control of the air supply with constant monitoring of the level of dissolved oxygen in the aeration tanks (and in some cases with constant automatic control of the concentration of ammonium and other pollutants in the effluent at the outlet of the aeration tanks) ensures optimal level energy consumption with guaranteed compliance of treated wastewater with existing standards.

The need to have several blowers in a unit (for example, two large and two small) is due to the fact that the control range of the air compressor is very limited. It ranges, at best, from 35% to 100% power, more often from 45% to 100%. Therefore, one controlled blower cannot always provide optimal air supply, taking into account daily and seasonal changes in demand. Today, the most famous are three types of blowers: rotary, screw and turbo.

Choice the right type Blowers are manufactured mainly according to the following parameters:

- maximum and nominal air supply demand - depends on the parameters of the installed aerators, which in turn are selected based on their efficiency and the need of the entire aeration system for dissolved oxygen, as described above;

— required maximum overpressure at the outlet of the blower - determined by the maximum possible depth of the aeration basin drains, more precisely by the depth of the aerators, as well as pressure losses when air passes through the pipeline and through all elements of the system, such as valves, etc.

As a rule, each controlled blower has its own control unit; it is also important to have a common control unit for all blowers, which ensures optimal operation. In most cases, control is carried out based on the pressure at the outlet of the blower unit.

Controlled air valves

If the system has one blower (or bank of blowers) supplying air to only one aeration basin, then it can be operated without air valves. But, as a rule, at aeration stations, a blower unit supplies air to several aeration tanks. In this case, air valves are required at the inlet of each aeration tank to regulate the distribution of air flow. Additionally, valves can be used on pipes that distribute the air supply to different zones one aeration tank. Previously, manually controlled butterfly valves were used for these purposes. However, to effectively control an aeration system, it is necessary to use remote controlled valves.

Important characteristics of controlled valves include:

1. Linearity of the control characteristic, i.e. the degree of compliance of changes in the position of the valve drive (actuator) with changes in air flow through the valve throughout the entire control range.
2. Error and repeatability of the valve drive working out the specified air flow setting. Determined by the quality of the valve (linearity of the control characteristic), actuator and actuator control system.
3. Pressure drop across the valve in the operating range of opening.

The pressure drop across butterfly valves when partially opened can be quite significant and reach 160-190 mbar, which leads to large additional energy costs.

If the system uses even the highest quality, but universal valves (designed for both water and air), the pressure drop across such valves in the operating opening range (40-70%) is usually 60-90 mbar. Simply replacing such a valve with a specialized air valve VACOMASS elliptic will lead to additional savings of at least 10% in energy! This is due to the fact that the pressure drop across the VACOMASS elliptic over the entire operating range does not exceed 10-12 mbar. An even greater effect can be achieved when using VACOMASS jet valves for which the pressure drop in the operating range does not exceed 5-6 mbar.

Controlled dedicated air valves

VACOMASScompaniesBinder GmbH, Germany.

Often, at the installation site of the controlled valve, the pipeline is narrowed in order to use a valve of the optimal size. Since the contraction and expansion are carried out in the form of a Venturi tube, this does not lead to any significant additional pressure drop in the valve area. At the same time, the smaller diameter valve operates in an optimal opening range, which ensures linear control and minimizes the pressure drop across the valve itself.

Dissolved oxygen sensors and valve control system

BA1 – aeration basin 1; BA2 – aeration basin 2;

PLC – program logic controller;

BV – blower block;

F – air flow meter; P – pressure sensor;

O2 – dissolved oxygen sensor

M – drive (actuator) air valve

CPS – valve control system

SUV – blower control system

The figure shows the most common scheme for controlling the air supply process for several aeration basins. The quality of wastewater treatment in aeration tanks is determined by the presence required quantity dissolved oxygen. Therefore, the main controlled value is usually taken to be the concentration of dissolved oxygen [mg/liter]. One or more dissolved oxygen sensors are installed in each aeration tank. The control system sets a setpoint (established average value) for the oxygen concentration, so that the minimum actual oxygen concentration is guaranteed to ensure a low concentration of harmful substances (for example, ammonium) in the effluent at the outlet of the aeration system - within the maximum permissible concentration. If the incoming volume of wastewater into a particular aeration tank decreases (or its BOD and COD decreases), then the need for oxygen also decreases. Accordingly, the amount of dissolved oxygen in the aeration tank becomes higher than the set point and, based on a signal from the oxygen sensor, the valve control system (VCS) reduces the opening of the corresponding air valve, which leads to a decrease in the air supply to the aeration tank. At the same time, this leads to an increase in pressure P at the outlet of the blower unit. The signal from the pressure sensor is sent to the blower control system (BCS), which reduces the air supply. As a result, the energy consumption of the blowers is reduced.

It should be noted that to solve the problem of energy saving, a well-thought-out optimal setting for a given minimum concentration of dissolved oxygen in the control system is very important.

Equally important is the correct and justified setting of the specified pressure P at the outlet of the blower unit.

Air flow meters

The main task of air flow meters in an aeration system from the point of view of energy saving is to stabilize the air supply process, which makes it possible to lower the dissolved oxygen concentration setting for the control system.

The air supply system from the blower unit to several aeration tanks is quite complex from a control point of view. In it, as in any pneumatic system, there is mutual influence and delay in the processing of control actions and signals from feedback sensors. Therefore, the actual dissolved oxygen concentration constantly fluctuates around the set point (set point). Availability of air flow meters and common system control of all valves can significantly reduce system response time and reduce fluctuations. Which, in turn, allows you to lower the setpoint without fear of exceeding the maximum permissible concentration of ammonium and other harmful substances in the wastewater at the outlet of the WWTP. From the experience of Binder GmbH, introducing data from flow meters into the control system allows additional energy savings of about 10%.

In addition, if the WWTP is undergoing a phased reconstruction of the aeration system, in which they first install aerators, valves, a valve control system and air flow meters while maintaining the old blower, and then move on to selecting new controlled blowers, then data on the actual air flow will help produce optimal choice blowers, which leads to significant savings in their purchase and operation.

A distinctive feature of VACOMASS flowmeters from Binder GmbH is their ability to operate on short straight sections “before” and “after” due to special technological solutions, and also to be installed directly in the VACOMASS valve block.

Ammonium sensor

An ammonium concentration sensor can be installed in the channel at the outlet of the wastewater from the aeration tank system to control the quality of treatment. In addition, the introduction of readings from the ammonium sensor into the control system allows you to further stabilize the system and obtain additional energy savings by further reducing the dissolved oxygen concentration set point.

An example of organizing a control system for air supply to aeration tanks with feedback from a dissolved oxygen sensor (DO) and ammonium (NH4).

Wastewater aeration - saturating the liquid with oxygen, giving life to bacteria that process toxins, organic matter, forming silt. Bubble flows are created by diffusers installed at the bottom of the treatment pond.

Large volumes of compressed air are required for continuous equipment operation, which can be provided by aeration blowers.

equipment requirements

Compressors for treatment facilities are selected based on the following conditions:

1. The first thing you should pay attention to when choosing a compressor is the depth of the reservoir. Every 10 m of liquid column creates a pressure of 1 bar. Accordingly, a blower for treatment facilities must create a working pressure sufficient to pump air to the bottom level. As a rule, the depth of treatment facilities does not exceed 7 meters (0.7 bar - 70 kPa), thus, most models of centrifugal and HRMT blowers produced by Thermomechanika LLC are suitable for aeration.
2. Performance, which is calculated based on the size of the reservoir, the number and characteristics of diffusers. The volume of air required can be from 100 to 50 thousand cubic meters per hour.
3. "purity". The air should not contain impurities of lubricating coolants, which will negatively affect the life of bacteria.
4. Simplicity and reliability. The low pressure compressor will have to work non-stop. For water aeration, machines with direct drive from the motor shaft, without gearboxes and V-belt transmissions. Centrifugal blowers from the Tremomechanika plant have a service life of more than 100 thousand hours of continuous operation.
5. Low noise. Small wastewater treatment plants serving private household settlements and commercial enterprises are becoming increasingly common. Proximity to housing, eliminates the use of equipment exceeding sanitary standards by noise level. The acoustic indicators of vortex and centrifugal blowers of Thermomechanics are in the range of 50-75 dB, which fully complies with the requirements of SanPiN.
6. Economical. Energy consumption directly depends on the efficiency and power of the supercharger motor. Rotary blowers for aeration have a higher efficiency, however, “gluttonous” vortex blowers have advantages in noise, reliability and purity of the pumped air

In order not to overpay for electricity, you need an accurate calculation of a sufficient amount of air per unit of time, knowing which, a blower of a certain capacity is selected.

The use of automatic control systems also allows you to reduce engine operating time and, accordingly, electricity bills.

How to choose

To buy the optimal type and model of blower, to minimize the cost of wastewater aeration, call the sales department of the Thermomechanics plant, or request a call back at a convenient time.

The service engineer will perform preliminary calculations air flow, will suggest the equipment most suitable for a specific situation.

Prices for products are announced at the request of the client, after agreeing on the blower model or technical specifications for the design of the installation.