The wastewater treatment complex is located in a building made of lightweight metal structures and has an automated process control system, a dewatering and sludge disposal system, a heating, ventilation, and lighting system. Dividing the wastewater treatment complex into independent technological lines makes it possible to ensure the purification of the entire volume of incoming wastewater to regulatory requirements in the event that up to 25% of the equipment - one or more lines - is taken out for repair (according to the requirements of SNiP 2.04.03-85). In addition, this allows emptying and preventive inspection of containers without stopping the treatment facilities. Wastewater goes through the following stages: mechanical treatment (pressure electrocoagulators, primary settling tanks with thin-layer modules), biological treatment unit (bioreactors with an anaerobic treatment zone, bioreactors with an aerobic treatment zone), coagulation and sedimentation of sludge in secondary settling tanks, post-treatment (electromagnetic filters, mechanical filters) and sorption purification), sludge treatment by mechanical dewatering. Wastewater from the plant enters a stabilizer tank located near the wastewater treatment plant building. Then, from the homogenizing reservoir, the wastewater is supplied by submersible pumps through a pressure pipeline to the treatment facilities and into electrocoagulators.
The electrocoagulator is designed for reagent-free coagulation of pollutants during water purification. Electrocoagulation is a reagent-free method of water purification that provides effective removal of organics, iron and other associated contaminants (there is a decrease in BOD, COD) due to anodic oxidation and cathodic reduction with the formation of water-insoluble compounds that precipitate in settling tanks.
Electrical processing combines chemical and electrochemical coagulation and destruction under the influence of direct current.
The process of electrolytic water purification proceeds through the stages:
-electrochemical interaction of substances on the surface of the electrodes and the redox processes occurring during this process;
-conversion of substances into insoluble compounds and formation of dispersed phases in water. In addition, sorption of ions and molecules of dissolved impurities, as well as impurities emulsified in water, occurs on the surface of aluminum hydroxides, which have significant sorption capacity, especially at the time of formation.
The anode metal is ionized under the influence of direct current and passes into the purified water. Aluminum hydroxides formed in water coagulate the dispersed system.
The electrocoagulator is a block of aluminum alloy electrodes placed in a closed housing and connected to a current rectifier. The electrocoagulator is compact and easy to use.
Membrane sensors are installed on the water inlet pipeline to the electrocoagulator to determine the pH of incoming wastewater, connected to digital dosing pumps with a pH control function. Neutralization of wastewater occurs automatically up to MPC standards. Neutralization is carried out with solutions of hydrochloric acid or caustic soda, stored in plastic containers.
From the electrocoagulator, the treated wastewater is fed into a primary settling tank with a thin-layer module. The foam formed in the electrocoagulator is extinguished by a defoamer, from where the coagulated foam enters the sludge pit through sludge pipelines.
Primary settling tanks are made of polymer material and are located in a single block of biological treatment tanks in housings identical to technological bioreactor tanks; they are used to sediment undissolved and partially colloidal contaminants, predominantly of organic origin. During the settling process, suspended particles settle. Sedimentation is the simplest, least energy-intensive and most economical method of separating mechanical impurities from wastewater with a density different from the density of water. The relative simplicity of settling facilities determines their widespread use at various stages of wastewater treatment and treatment of resulting sludge. Smaller suspended particles and colloidal contaminants are separated as wastewater passes through thin-layer modules installed in settling tanks. Their separation ability, especially when separating finely dispersed impurities, is many times higher. The feasibility of using thin-layer sedimentation tanks is based on the fact that reducing the flow height while maintaining the same speed of movement proportionally reduces the settling time. Dividing the flow height into smaller sections simultaneously increases the settling area and reduces the specific load of suspended matter on it. The settling effect is 40-60% with a settling duration of 1.5-2 hours. Due to hydrostatic pressure, the sludge from the conical part of the settling tanks flows through the pipeline into the sludge pit.
Primary settling tanks for mechanical wastewater treatment are a preliminary stage before biological treatment. With mechanical wastewater treatment, the effect of reducing suspended solids is 40 - 60%, which also leads to a decrease in the BOD value by 20 - 40%.
Next, the wastewater from the primary settling tanks flows by gravity into the bioreactor.
Each bioreactor, operating in parallel, consists of 4-6 (depending on the parameters of the water being treated) cone-shaped communicating tanks, separated by vertical overflow partitions and made of polymer material. Process tanks are equipped with an automated sludge discharge system.
The treated wastewater first enters the anaerobic zone of the bioreactor, in which the destruction of difficult-to-oxidize organic matter occurs on a biocarrier with immobilized and free-floating microorganisms. Then the wastewater is purified in the aerobic zone of the bioreactor (aeration tanks). In addition, nitrification and sulfate reduction processes occur in the anaerobic zone of the bioreactor, as a result of which ammonium compounds are oxidized to nitrates, and sulfates to elemental sulfur.
In aeration tanks-bioreactors, a mixture of activated sludge and purified waste liquid moves slowly. The mixture of waste liquid with activated sludge is aerated throughout the aeration tanks through a system of air supply pipes and micro-bubble titanium aerators to oxidize organic matter and saturate the water with oxygen necessary for the life support of microorganisms and the removal of gaseous decomposition products. Air supply is carried out using blower compressors. The compressors are equipped with the basic accessories necessary for trouble-free operation. The operation of the compressors is fully automated. In the event of an unexpected shutdown of the working compressor, the backup unit is automatically switched on.
In order to intensify the operation of treatment facilities, an aeration system was used using pneumatic aerators made of sintered titanium powders. The main advantage of porous metal aerators compared to filter plates and tubular aerators is lower specific resistance (3-4 times) with a smaller pore size (hence, smaller bubble size - up to 150 microns), which makes it possible to reduce the air supply by 30- 50%, thereby reducing specific energy consumption for aeration without compromising the quality of cleaning. Each bioreactor tank is divided into two sections by partitions. Each section contains cassettes with biocarrier BPS-140-60.
An important distinctive feature of the facilities (WWTP) is the use of biotechnologies with activated sludge immobilized on an inert biocarrier (loading). The biocarrier has a spatial spiral design and is made of polymer materials, the advantages of which are low specific gravity, chemical resistance, and high specific surface area. Thanks to its rough structure, the load retains biofilm well, which is not removed from the structure during large influxes of wastewater and other unfavorable conditions. This makes it possible to create and maintain stable high concentrations of destructor microorganisms in bioreactors, and increases the system’s resistance to uneven supply of wastewater for treatment and heterogeneity of its qualitative composition.
Methods for intensifying the operation of an aeration tank, the use of biocarriers to form an immobilized form of microorganisms on them, as well as the use of thin-layer blocks in settling tanks are certified and protected by a patent.
As a result of biological purification, clear, non-rotting water containing dissolved oxygen and nitrates is obtained. Biological treatment facilities ensure a reduction in pollution indicators for suspended solids and BOD.
For more complete removal of phosphorus compounds and sedimentation of sludge, a solution of aluminum polyoxychloride coagulant is supplied in the secondary settling tank. To prepare the coagulant solution, a unit for preparing and dosing reagents is provided, consisting of plastic tanks for preparing and storing the coagulant solution and dosing pumps for supplying the solution. Water for preparing the coagulant solution is delivered to the tanks through a purified water pipeline. The coagulant solution is supplied to the bioreactor before the secondary settling tank.
Purified water flows by gravity into secondary settling tanks with thin-layer modules. In the secondary settling tank, waste sludge settles. After the secondary settling tank, the purified wastewater flows by gravity into intermediate tanks, from where it is supplied by a submersible pump to the post-treatment unit for mechanical, electromagnetic and sorption filters operating in automatic mode.
The mechanical cleaning filter system consists of:
- columns made of fiberglass or stainless steel;
- distribution (drainage and distribution) system;
- loadings (quartz sand);
- gravel substrate;
- automatic control unit.
During filter operation, the filter material becomes contaminated. To wash the filter material from contaminants and restore its properties, automatic washing is carried out.
The wash water is returned through the pipeline to the stabilizer tank together with the filtrate. After washing is completed, the filter automatically switches to operating mode.
After being purified using electromagnetic filters, the wastewater flows by gravity to sorption purification filters. Sorption purification filters are similar in design and operating principle to mechanical purification filters, only activated carbon is used as a filter media in sorption purification filters.
Treated wastewater passes through a flow meter and is sent to the outlet.
During the process of settling wastewater in settling tanks, large masses of sediment are formed that are capable of rotting, so the sediment must be subjected to further processing. A belt filter press is used to dewater sludge after primary, secondary settling tanks and a bioreactor.
Sludge from the primary and secondary settling tanks and the bioreactor flows through the sludge pipeline due to hydrostatic pressure into the sludge pit. From the pit, the sludge is fed by a submersible pump to the sludge dewatering unit (belt filter press with thickener).
Together with the sediment, a solution of the flocculant “VPK-402” is supplied to the thickener, the solution of which is stored in a plastic container and supplied by a dosing pump. After disinfection, the dewatered and disinfected sludge is unloaded onto a sealed dump trailer and transported to the solid waste landfill. Dewatered sludge belongs to the fourth hazard class. In the event of a filter press failure, it is possible to remove raw sludge by sewerage trucks for further processing.