COST OF PROJECT DEVELOPMENT

To determine the base (initial) cost of design and estimate documentation and survey work, Region LLC uses a time-tested method: drawing up estimates for design and survey work using reference price reference books. The estimated cost of design and survey work is a reasonable initial cost of work, which is specified in the process of clarifying the scope of work and negotiations. The estimate for design and survey work compiled according to reference price reference books can serve as a justification for the price during the tender procedure in accordance with Federal Laws No. 44 and No. 223.

STARTING TO COOPERATE WITH US YOU SAVE

HOW WE DESIGN

1. Customer's idea
2. Preparation of pre-design solutions and variable design
3. Development of a feasibility study (FS)
4. Protecting the main decisions before the customer, choosing the best option
5. Preparation of a detailed technical assignment for: project development, engineering surveys, inspection
6. Development of working documentation
7. Approvals
8. Author's supervision
9. The embodied idea of ​​the customer

LICENSES AND CERTIFICATES OF REGION LLC

Region LLC is a member of voluntary quality certification in accordance with GOST R ISO 9001-2015. Registration No. SMK.RTS.RU.03121.17

WE WORK ON LICENSED SOFTWARE

This article describes the technological parameters of the biological treatment in aeration tanks. The peculiarities of the technological scheme are described: high concentration of sludge mixture, high coefficient of activated sludge recirculation. To eliminate the disadvantages inherent in the aeration tanks-displacers, structural changes were made to the aeration tanks: a new aeration system was installed, a longitudinal recycle of the sludge mixture in the aerotanks was arranged using airlifts.

Photo 1. Ciliates Epistylis plicatilis

Photo 2. Colony of rotifers

Photo 3. Rotifer in a layer of silt

Control over the process of biological treatment in aerotanks is carried out in physicochemical and hydrobiological laboratories using modern methods of analysis using video cameras and computers to accumulate information about the state of the biocenosis and all its changes.

As a result of the reconstruction, high results of wastewater treatment were achieved. The concentration of organic pollutants after biological treatment does not exceed 3 mg / dm3. The total concentration of mineral nitrogen does not exceed 10 mg / dm 3, the purification efficiency for heavy metals is 94-96%, for oil products - 92-96%. The results achieved (in terms of the quality of treatment and energy efficiency indicators) allow us to conclude that it is advisable to use the biological treatment process in aeration tanks with low loads to achieve high quality treatment at low costs for the reconstruction of biological treatment facilities. The renovation costs pay off within two to three years.

In the shop of NIOSV of JSC "Minudobreniya", wastewater treatment is carried out in two cities near Moscow - Yegoryevsk and Voskresensk. The volume of wastewater is on average 60-80 thousand m 3 / day. The nature of the incoming pollution is household. Wastewater has a concentration of suspended solids in the range of 150-180 mg / dm 3, for BOD-5 - up to 160 mg / dm 3, for COD - 250-350 mg / dm 3. The treatment facilities are designed according to the classical biological treatment scheme. The resulting sediment, after special treatment, is used in full for the reclamation of an industrial landfill. The structures built 40 years ago have been reconstructed many times. In the last decade, the reconstruction of biological treatment in aerotanks has been completed in order to improve the quality of wastewater treatment and the energy efficiency of the treatment process.

Traditional biological treatment schemes (using microorganisms in suspension in aerotanks with their subsequent sedimentation in secondary sedimentation tanks) do not provide effective and reliable wastewater treatment up to strict established norms of permissible discharge. Especially great difficulties arise when reaching the permissible discharge norms for fishery water bodies.

To solve the problem of deep purification of wastewater from organic and biogenic compounds, several fundamental technological processes have been developed in world practice: SBR technology (with variable-action reactors); the technology of sequential alternation of aerobic, anoxic and anaerobic biological treatment zones in the aeration tank; biomass concentration technology by combining suspended and attached forms of microorganisms in reactors; technology for concentrating the biomass of suspended forms of microorganisms with their subsequent retention by special membranes.

The concentration of organic pollutants after biological treatment does not exceed 3 mg / dm3. The total concentration of mineral nitrogen does not exceed 10 mg / dm 3, the cleaning efficiency for heavy metals is 94-96%, for oil products - 92-96%

SBR technology assumes sequential carrying out in one reactor in a periodic mode, during its operation, alternating aerobic and anaerobic processes. This technology is very expensive and requires a very complex system of actuators to execute the commands of the process control system. The cyclic-variable oxygen conditions of the life of microorganisms in such a reactor, due to the adaptation factor, inhibit the rate of biochemical reactions and increase the time required for the reaction to proceed. This increases the size of the reactor.

The technology of sequential alternation of anaerobic, anoxic and aerobic zones during reconstruction reduces the productivity of biological treatment by 30-40%. The multivariate system of recycle of activated sludge and effluent from different processing zones significantly complicates the control over the technological process and its controllability. The number of actuators installed in inaccessible places is increasing, and the volume of pumped activated sludge is significantly increased.

The technology of biomass concentration using suspended forms of microorganisms attached to inert carriers is associated with the costs of purchasing carriers, installing these carriers in bioreactors and significant difficulties in the repair of aeration systems. The appearance of biofilm from inert carriers in the sludge mixture requires an increase in the settling time of the sludge mixture, that is, an increase in the size of the settling tanks. The technology for concentrating the biomass of suspended forms of microorganisms in a reactor (with subsequent separation on polymer membranes) is associated with the expense of funds for reagents for membrane regeneration and with the complexity of operation.

However, it is necessary to reconstruct the existing biological treatment facilities with an increase in the efficiency of treatment to reduce the discharge of organic pollutants and biogenic elements into water bodies. This is possible when using propellant aeration tanks in the extended aeration mode.

The process of wastewater treatment in an aeration tank can be represented as follows. When clarified effluent enters the aeration tank, the effluent is mixed with the return sludge pops. Sorption of undissolved and colloidal impurities, which come with clarified wastewater, occurs on the surface of zoogles, which make up the cotton of the silt. Situated on the surface of zoogles, which are covered with polysaccharide helium, bacteria, in the presence of oxygen, release enzymes to oxidize impurities. Part of the dissolved impurities enters the body of bacteria, where they are oxidized with the help of enzymes. In the case of oxidation of contaminants by bacterial enzymes, it is possible to use both oxygen dissolved in the sludge mixture and nitrates. The compounds obtained as a result of enzymatic oxidation are used by bacteria for reproduction, that is, growth in numbers.

The development of bacteria in the aerotank can be conditionally divided into three phases. The first is the logarithmic growth phase. In this phase, there is an increase in the number and mass of bacteria by the amount of contaminants contained in the incoming wastewater, minus the mass used by the bacteria themselves to obtain energy for life.

In the second phase (developed biocenosis of activated sludge), there is a rapid development of predatory microorganisms that use the mass of bacteria and the remaining pollution as food and for subsequent reproduction. Depletion of reserves of easily oxidized organic matter transforms the activated sludge biocenosis into the phase of endogenous respiration or autotrophic oxidation. In this phase, the source of energy for the life and reproduction of microorganisms is the mass of microorganisms of the activated sludge itself. The number of bacteria sharply decreases, the number of predatory microorganisms is determined by the rate of self-oxidation of microorganisms in the sludge.

In the third phase, the oxidation of inorganic nitrogen compounds resulting from the oxidation begins - a nitrification reaction takes place using a large amount of oxygen from the sludge mixture. In the phase of endogenous respiration of microorganisms, the following processes take place: the formation of large dense cotton sludge from zooglya bacteria, filamentous bacteria, fungi, actinomycetes; the process of oxidation of organic matter continues - the matter of organisms of the activated sludge biocenosis; oxidation of inorganic forms of nitrogen in the presence of oxygen occurs - nitrification, reduction in the presence of nitrates - denitrification.

The biocenosis of activated sludge in corridor aerotanks operating under low loads, with deep nitrification and denitrification, is characterized by a large species diversity (over 30 species of protozoa), however, without a numerical predominance of any species

To carry out these opposite reactions in relation to oxygen, it is necessary to create conditions for each of them. This is only possible by creating different zones: anaerobic, aerobic and anoxidic. Sludge cotton can be considered as a spherical or ellipsoidal formation with zones inside it, where dissolved oxygen from the sludge mixture does not enter, even with a significant oxygen concentration (4-6 mg / dm 3) in waste water.

To carry out the process of cleaning wastewater from incoming pollution, it is necessary to deeply oxidize the organic matter contained in the clarified water, deeply oxidize the substance of activated sludge bacteria. The resulting nitrogen-containing substances are oxidized to nitrates and reduced to gaseous nitrogen. To increase the speed of the reduction (denitrification) reaction, it is necessary to increase the anoxic and anaerobic zones in the aeration tank.

The increase is carried out in two ways:

• due to an increase in the number of sludge pops, which leads to an increase in sludge concentration up to 5-6 mg / dm 3;
• due to an increase in the size of sludge flocks, which leads to a decrease in the BOD load to 35-50 mg per gram of dry matter per day, maintaining microorganisms in the phase of endogenous respiration.

At the same time, low BOD loads on the aeration tank allow deep oxidation of organic matter up to 3.5 mg / dm 3, almost up to theoretically achievable 2.5 mg / dm 3. On the basis of the above theoretical provisions in the aeration tanks of the NiOPSV workshop, an operating mode was organized with the following values ​​of technological parameters: BOD load - 35-50 mg per gram of BOD dry matter per day; aeration time - 8-12 hours; sludge dose - 5-6 g / dm 3; dissolved oxygen concentration - 4-6 mg / dm 3; recirculation coefficient - 0.8-1.0; electrode potential within -200 ...- 250 mV; sludge index - 90-130; ash content of sludge - 35-40%; specific air consumption for aeration - 6-7 m 3 per 1 m 3 of effluent; specific power consumption for aeration - 0.35-0.4 kWh per 1000 m 3.

At the same time, it is necessary to note the disadvantages of corridor aeration tanks:

• uneven load on activated sludge along the length of the structures, which worsens its technological performance;
• lack of dissolved oxygen at the beginning of the first corridor and excess in the second half of the second corridor.

To eliminate these disadvantages, a longitudinal recycle of the sludge mixture was arranged in the aeration tanks. The diagram is shown in Fig. 1. The recirculation unit is made in the form of a water-air pump-airlift, which pumps the sludge mixture from the end of the second corridor to the beginning of the first. The value of the recycling ratio is 2.1-2.5. As a result of a longer stay of activated sludge in aerobic conditions and acceleration of biomass turnover: the oxidizing capacity of activated sludge biomass increases due to an increase in the level of enzymatic activity; macroturbulence in the aerotank increases - the size of stagnant zones decreases; the specific load on activated sludge is reduced; the oxygen regime of the structure is improved, without reducing the average path length of the treated wastewater, which eliminates the "slip" of unoxidized contaminants.

This made it possible to achieve the following: increase the mineralization of activated sludge and reduce the amount of excess activated sludge to a minimum value; to increase the stability of the biocenosis of activated sludge when discharges of hard-to-oxidize industrial effluents enter, the state of sludge was monitored using the bioestimation method; stabilize the oxygen regime in the sludge mixture during the repair of the blowers.

The biocenosis of activated sludge of corridor aerotanks operating under low loads, with deep nitrification and denitrification, is characterized by a large species diversity (over 30 species of protozoa) without a numerical predominance of any species. The number of filamentous bacteria, small colorless flagellates, small forms of naked and shell amoebas is insignificant. Of the ciliates, gastric and attached forms predominate.

Photo 1 shows a colony of Epistylis plicatilis. The presence of predators has a positive effect on the degree of water purification from organic pollution due to the intensification of biological processes in the bacterial environment due to the entry into it of substances released from microfauna fragments during their destruction in aerotanks in the phase of endogenous respiration. Active silt always contains rotifers (photo 2-3), sucking ciliates, predatory mushrooms, various worms, tardigrades.

For BOD5, a value of 3 mg / dm 3 was reached, which corresponds to the maximum permissible discharge (MPD) for fishery water bodies (Fig. 2). The COD value is 30 mg / dm 3. For mineral nitrogen - 10 mg / dm 3 (Fig. 3), which corresponds to the recommendations of the Helsinki Commission (Helcom) for cities with a population of more than 100 thousand inhabitants. The efficiency of cleaning for iron was 90-92%, of cleaning for heavy metals - 94-96%, efficiency for oil products - 92-96%.

When aeration tanks operate at low loads with a longitudinal recycle coefficient of 2-3:

• high quality of wastewater treatment is achieved, in accordance with the recommendations of Helcom without increasing the cost of electricity during operation;
• high quality cleaning does not require large expenditures of raw materials;
• the process is easy to maintain and control;
• reconstruction of corridor aeration tanks into aeration tanks operating in extended aeration mode requires minimal costs (for the reconstruction of the aeration system, increasing the productivity of pumps for return sludge, installation of airlifts for longitudinal recycle);
• the costs of paying to the budget for the discharge of pollution with treated wastewater are reduced;
• the amount of excess activated sludge is significantly reduced - the costs of its dehydration and disposal are reduced;
• the technological process is not complicated (no costs are required for complex control devices, executive regulating mechanisms, the requirements for the qualifications of service personnel are not increased).

Such reconstruction is a real way to improve the quality of treatment of most wastewater treatment plants of regional significance. The costs of further improving the quality of nitrogen and phosphorus purification (until the established MPD standards for fishery water bodies are reached) are too high, for example, for the budget of a settlement with a population of less than 250-300 thousand people.

1. Belyaeva N.A., Gunther L.I. On the characterization of activated sludge biocenoses in highly loaded aeration tanks and aeration tanks with a long period of aeration // Biological Sciences, No. 7/1969.
2. Zhmur N.S. Process control and control of the result of wastewater treatment. - M .: Luch, 1997.
3. Zhmur N.S. Methodical guidelines for hydrobiological and bacteriological control of the biological treatment process at facilities with aeration tanks. - M .: LLC "Aquareos", 1996.
4. Nikitina O.G. Bioestimation: control and regulation of the processes of biological purification and self-purification of water. Abstract of the thesis. for a job. uch. Art. Doctor of Biological Sciences - M., 2012.
5. G.V. Kapitonova Methodical recommendations for the hydrobiological control of wastewater treatment with activated sludge. - M., 2012.

font size

SEWERAGE - OUTDOOR NETWORKS AND STRUCTURES - SNiP 2-04-03-85 (approved by the Decree of the State Construction Committee of the USSR from 21-05-85 71) (revised from 20-05-86) ... Actual in 2018

Aeration plants for complete oxidation (aeration tanks with extended aeration)

6.166. Aeration plants for complete oxidation should be used for biological wastewater treatment.

Before supplying wastewater to the installation, it is necessary to provide for the retention of large mechanical impurities.

6.167. The duration of aeration in aeration tanks for complete oxidation should be determined by the formula (48), while it should be taken:

р - average oxidation rate according to BOD_full - 6 mg / (g x h);

a_i - sludge dose - 3 - 4 g / l;

s - ash content of sludge - 0.35.

The specific air consumption should be determined by the formula (61), while it should be taken:

q_O - specific oxygen consumption, mg / mg of removed BOD_full, - 1.25;

K_1, K_2, K_T, K_3, C_a - according to the data given in clause 6.157.

6.168. The duration of the wastewater stay in the sedimentation zone at the maximum inflow should be at least 1.5 hours.

6.169. The amount of excess activated sludge should be taken as 0.35 kg per 1 kg of BOD_full. Removal of excess sludge is allowed to be provided both from the settling tank and from the aeration tank when the sludge dose reaches 5 - 6 g / l.

The moisture content of the sludge removed from the settling tank is 98%, from the aeration tank 99.4%.

6.170. The load on the sludge pads should be taken as for sediments fermented in mesophilic conditions.

Aerobic biological treatment of large volumes of water is carried out in aeration tanks - rectangular in terms of reinforced concrete structures with activated sludge freely floating in the volume of treated water, the bio-population of which uses wastewater pollution for its life.

Aerotanks can be classified according to the following criteria:

1. according to the flow structure - aeration tanks-displacers, aeration tanks-mixers and aeration tanks with a dispersed inlet of waste fluid (intermediate type) Figure 51;

Figure 51 - Schemes of aeration tanks
a - aeration tank-displacer; b - aeration mixer; c - intermediate type aeration tank;
1 - waste water; 2- return activated sludge; 3- aerotank; 4 - silt
mixture.

2. by the method of activated sludge regeneration - aerotanks with separate or combined sludge regenerators;
3. by load on activated sludge - high-load (for incomplete cleaning), normal and low-load (with extended aeration);
4. by the number of stages - one-, two-, and multi-stage;
5. according to the mode of input of wastewater - flowing, semi-flowing, with a variable working level, contact;
6. by the type of aeration - pneumatic, mechanical, combined hydrodynamic or pneumomechanical;
7. by design features - rectangular, round, combined, mine, filter tanks, flotation tanks, etc.

Aeration tanks are used in an extremely wide range of wastewater flow rates from several hundred to millions of cubic meters per day.

In mixing aeration tanks, water and sludge are introduced evenly along the long walls of the aerotank corridor. Complete mixing of waste water with a sludge mixture in them ensures the equalization of sludge concentrations and rates of the biochemical oxidation process. The load of contaminants on the sludge and the rate of oxidation of contaminants are practically unchanged along the length of the structure. They are most suitable for purification of concentrated (BODp up to 1000 mg / l) industrial wastewater with significant fluctuations in their consumption and concentration of contaminants. In aeration tanks, water and sludge are supplied to the beginning of the structure, and the mixture is removed at the end of it. The aeration tank has 3-4 corridors. Theoretically, the flow regime is piston without longitudinal mixing. In practice, there is significant longitudinal mixing. The load of contaminants on the sludge and the rate of oxidation vary from the highest values ​​at the beginning of the structure to the lowest at its end. Such structures are used in the event that a sufficiently easy adaptation of the activated sludge is ensured. In aeration tanks with a dispersed water supply along its length, unit loads on sludge decrease and become more uniform. Such facilities are used for the treatment of mixtures of industrial and municipal wastewater.

The operation of the aeration tank is inextricably linked with the normal operation of the secondary clarifier, from which the return activated sludge is continuously pumped into the aeration tank. Instead of a secondary clarifier, a skimmer can be used to separate sludge from water.

The main technological schemes for cleaning in aeration tanks are shown in Figure 52.

Figure 52 - Basic technological schemes for wastewater treatment in aeration tanks
a - one-stage aerotank without regeneration; b - one-stage aerotank with regeneration; c - two-stage aeration tank without regeneration; d - two-stage aeration tank with regeneration; 1 - waste water supply; 2 - azrotenc; 3 - release of sludge mixture; 4 - secondary sedimentation tank; 5 - outlet of purified water; 6 - release of exfoliated activated sludge; 7 - sludge pumping station; 8 - supply of returnable activated sludge; 9 - release of excess activated sludge; 10 - regenerator; 11 - discharge of waste water after the first stage of treatment; 12 - second stage aeration tank; 13 - second stage regenerator.

In a one-stage scheme without a regenerator, it is impossible to intensify the wastewater treatment process. In the presence of a regenerator, oxidation processes end in it and the sludge acquires its original properties. The two-stage scheme is used when the initial concentration of organic pollutants in the water is high, as well as in the presence of substances in the water, the oxidation rate of which is sharply different. At the first stage of treatment, the BOD of wastewater is reduced by 50-70%.

To ensure the normal course of the biological oxidation process, air must be continuously supplied to the aerotank. Aeration must provide a large contact surface between air, waste water and sludge, which is a prerequisite for effective cleaning.

The aeration system is a complex of structures and special equipment that supplies oxygen to the liquid, maintains the sludge in suspension and constantly mixes waste water with sludge. For most types of aeration tanks, the aeration system provides the simultaneous performance of these functions. According to the method of dispersing air in water, in practice, three aeration systems are used: pneumatic, mechanical and combined.

With mechanical aeration, mixing is carried out by mechanical devices (agitators, turbines, shields, etc.), which provide crushing of the air jets drawn directly from the atmosphere by the rotating parts of the aerator (rotor).

Pneumatic aeration, in which air is pumped into the aeration tank under pressure, is divided into three types depending on the size of the air bubbles: fine-bubble (1-4 mm), medium-bubble (5-10 mm), large-bubble (more than 10 mm). devices for air in a fine-bubble aeration system, diffusers made of ceramics are used. Plastics, fabrics in the form of filter plates, tubes, domes. To obtain medium-bubble aeration, perforated pipes, slotted and other devices are used. Large bubble aeration is created by open pipes, nozzles, etc.

A modern aerotank is a technologically flexible structure, which is a corridor-type reinforced concrete tank equipped with an aeration system. The working depth of the aeration tanks is from 3 to 6 m, the ratio of the width of the corridor to the working depth is from 1: 1 to 2: 1. For aeration tanks and regenerators, the number of sections must be at least two; with a productivity of up to 50 thousand m3 / day, 4-6 sections are assigned, with a higher productivity of 8-10 sections, all of them are working. Each section consists of 2-4 corridors.

Did not find an answer to your question? Look at here

The benefits of wax candles: creating a favorable aura Passionate candle what to do with it

Protect for good trade: how to do it yourself?

Is it possible to make a love spell while fasting