A. Introduction to A.CCAS process
CCAS process, namely continuous circulating aeration system process (continuous circulating aeration
System) is a continuous influent SBR aeration system. This process is carried out in SBR (sequencing batch reactor)
Reactor, sequencing batch process). SBR process has been successfully developed as early as 19 14, but it is difficult to be popularized and applied in large sewage treatment plants due to complicated manual operation and management, backward monitoring methods and easy blockage of aerators. SBR process is generally considered to be suitable for small sewage treatment plants. Since the 1960s, automatic control technology and monitoring technology have developed rapidly, and a new type of non-clogging microporous aerator has also been successfully developed, which has created conditions for the wide use of intermittent treatment. 65438-0968 The University of New South Wales in Australia cooperated with ABJ Company in the United States to develop the aerobic activated sludge process with continuous water inflow, periodic drainage and prolonged aeration. 1986, the National Environmental Protection Agency officially recognized CCAS as an innovative alternative technology (I/A) and became the most advanced computer-controlled biological phosphorus and nitrogen removal process.
CCAS process has low requirements for sewage pretreatment, and only mechanical grid and grit chamber are set with the spacing of15 mm.. The core of biological treatment is CCAS reaction tank, and the functions of phosphorus removal, nitrogen removal and degradation of organic matter and suspended matter are all completed, and the effluent can meet the standard.
The pretreated sewage continuously enters the pre-reaction tank at the front of the reaction tank, and most of the soluble BOD in the sewage is adsorbed by activated sludge microorganisms, and enters the reaction zone at a low flow rate (0.03-0.05 m/min) from the holes at the lower part of the partition walls of the main reaction zone and the pre-reaction zone. In the main reaction zone, the process of "aeration, idle, sedimentation and decanting" is operated periodically, so that the wastewater can be decarbonized and denitrified in the repetition of "aerobic-anoxic" and dephosphorized in the repetition of "aerobic-anaerobic". The duration of each process and the operation of the corresponding equipment are controlled by the computer according to the pre-programmed adjustable program.
The unique structure and operation mode of CCAS process make it have unique advantages in technology:
(1) During aeration, sewage and sludge are completely mixed, which ensures the removal rate of BOD and COD, and the removal rate is as high as 95%.
(2) The repeated operation modes of "aerobic-anoxic" and "aerobic-anaerobic" strengthen phosphorus absorption and nitrification-denitrification, so that the removal rate of nitrogen and phosphorus reaches over 80% and the effluent index is qualified.
(3) During precipitation, the whole CCAS reaction tank is in a completely ideal precipitation state, and the effluent suspended solids (SS) is extremely low, and the low SS value also ensures the phosphorus removal effect.
The disadvantage of CCAS process is that each pool runs intermittently at the same time, and manual control is almost impossible. Relying on computer control requires high quality of management personnel in the treatment plant and strict requirements on design, training, installation and debugging.
B. Overview of the development of urban sewage treatment plants at home and abroad
Water is an important factor of economic development and social sustainable development. With the continuous expansion of city scale and the increase of population, water pollution has become a major problem. Urban sewage is an important cause of water pollution in rivers and lakes at present, and it is one of the main reasons that restrict the sustainable development of many cities. "Environmental protection" is the basic national policy of China. China's sustainable development strategy and countermeasures in 2000 require that the centralized treatment rate of urban sewage should reach 20%. At present, China is in a period of great development of urban sewage treatment, especially with the implementation of the national strategy of developing the western region, the environmental and ecological protection in the central and western regions has been put on the agenda.
Since the industrial revolution 200 years ago, people have paid more and more attention to the treatment of urban domestic sewage. Urban sewage treatment rate has become an important symbol of a region's civilization or not. In the past 200 years, urban sewage treatment has developed from the initial natural treatment and simple primary treatment to the advanced treatment and reuse of sewage by various advanced technologies. The treatment process has also developed from the traditional activated sludge process and oxidation ditch process to A/O, A2/O, AB and SBR (including CCAS process) to meet different effluent requirements. Compared with foreign developed countries, China's urban sewage treatment started late, and the current urban sewage treatment rate is only 6.7%. While vigorously attracting foreign advanced technology, equipment and experience, we must combine the development of China, especially the local actual situation, and explore an urban sewage treatment system suitable for the actual situation in China.
Combined with the actual situation in China and drawing lessons from foreign advanced technology and experience, the construction of urban sewage treatment plants should meet the following development directions:
(1) province of total investment. As a developing country, China needs huge funds for its economic development, so strictly controlling the total investment is of great benefit to the national economy.
(2) Low operating cost. Operating cost is an important factor for the normal operation of sewage treatment plants, and it is also one of the main indicators to judge the quality of a set of processes.
(3) It occupied a province. China has a large population, and per capita land resources are extremely scarce. Land resources are an important factor in the development and planning of many cities in China.
(4) Effect of nitrogen and phosphorus removal. With the eutrophication of large-scale water environment in China, nitrogen and phosphorus removal from sewage has become an urgent problem. China's latest national integrated wastewater discharge standard (GB8978- 1996) also clearly stipulates that it is applicable to all pollutant discharge units, and very strictly stipulates the phosphate discharge standard and ammonia nitrogen discharge standard. This means that most urban sewage treatment plants should consider the problem of nitrogen and phosphorus removal in the future.
(5) Organic combination of modern advanced technology and environmental protection engineering. The appearance and perfection of modern advanced technology, especially computer technology and automatic control system equipment, has provided strong support for the development of environmental protection engineering. At present, most sewage treatment plants in developed countries abroad adopt advanced computer management and automatic control systems to ensure the normal operation of sewage treatment plants and stable and qualified effluent, but China is still relatively backward in this respect. Computer control and management will also be the development direction of urban sewage treatment plants in China.
Process comparison of several treatment systems
In order to choose the most reliable urban sewage treatment system in technology, the most economical in investment and the most convenient in management, combined with the local actual situation, we investigated and compared the mature experience and development trend of sewage treatment plants at home and abroad.
At present, most urban sewage treatment plants at home and abroad adopt primary treatment and secondary treatment. The primary treatment adopts physical methods, mainly through grid interception, precipitation and other means to remove large suspended solids and sand particles in wastewater. This treatment process is relatively mature at home and abroad, with little difference. The secondary treatment adopts biochemical method, which mainly removes suspended solids, dissolved organic matter, nitrogen, phosphorus and other nutrients from wastewater by means of microbial life movement. At present, there are many ways to deal with this process. To sum up, the representative processes mainly include traditional activated sludge process, oxidation ditch, A/O or A2/O process, SBR and CCAS process. At present, these representative processes have practical applications at home and abroad.
Second, SPR high turbidity sewage treatment technology
Nowadays, natural fresh water resources have been fully developed, and natural disasters are becoming more and more frequent. The shortage of water resources has posed a very serious threat to the economy and citizens' life in many cities around the world. The water shortage crisis has become a reality we are facing. The important way to solve the problem of urban water shortage should be to convert urban sewage into urban water supply source. Urban sewage is available nearby, stable in source and easy to collect, and it is a reliable and stable water supply source. After purification, urban sewage can be mainly used as municipal greening, landscape water and industrial water for reuse.
Urban sewage recycling project includes sewage collection system, sewage purification treatment technology and its system, sewage transmission and distribution system, reuse water application technology and monitoring system. Among them, the sewage purification and regeneration technology and its system are the key, the sewage purification and treatment process should be simple and reliable, the investment and operation costs should be affordable for the city's economic strength, and the treated effluent quality should meet the reuse requirements.
The traditional "primary treatment" and "secondary treatment" water treatment technologies and equipment used for many years have been difficult to meet the purification requirements of high turbidity and high concentration sewage, and the treated effluent can not meet the water quality requirements of urban reclaimed water reuse. Along the traditional process route, we can only further increase the traditional "three-stage treatment" equipment system, which can neither avoid the huge and complex traditional two-stage biochemical treatment system nor avoid the traditional three-stage filtration and adsorption treatment system with very expensive investment and operation costs. These are precisely the taboos to realize sewage reuse. Therefore, the environmental protection market urgently needs new sewage treatment technology and equipment with higher purification efficiency. The treated effluent can meet the existing environmental protection standards and can be reused in cities, and the investment and operating costs should be acceptable to the economic strength of existing cities.
The newly invented "SPR high turbidity sewage purification system" (American invention patent) combines the "primary treatment" and "tertiary treatment" procedures of sewage into one, and puts them into a water tank of the SPR sewage purifier.
, quickly completed in 30 minutes.
. It is allowed to directly inhale high-turbidity sewage with suspended matter (turbidity) as high as 500 mg/L to 5000 mg/L, and the suspended matter (turbidity) of treated effluent is lower than 3 mg/L (degree); It is allowed to directly inhale high-concentration organic sewage with CODcr of 200 mg/L ~ 800 mg/L. After treatment, the CODcr of the effluent can be reduced to below 40 mg/L, which is equivalent to ordinary sewage.
The project investment and operating cost of the secondary sewage treatment plant are lower than that of the conventional secondary treatment, which can achieve the effect of tertiary treatment and realize the recycling of urban sewage.
The SPR sewage treatment system firstly separates the dissolved pollutants from the real solution by chemical methods to form colloidal particles or tiny suspended particles with solid interfaces; Select efficient and economical adsorbents to separate organic pollutants and chromaticity in sewage; Then all kinds of colloidal particles and suspended particles in sewage are condensed into large and dense flocs by microscopic physical adsorption; Then, relying on the principles of fluid mechanics such as cyclone and filtration hydraulics, the floc and water can be quickly separated in the self-designed SPR high turbidity sewage purifier. After the clean water is filtered by the self-formed dense suspended mud layer in the tank, it reaches the tertiary treatment level and the effluent is reused; Sludge is highly concentrated in the concentration chamber and discharged under pressure at regular intervals. Because of its low moisture content and good dewatering performance, sludge can be directly sent to a mechanical dewatering device, and the dewatered mud cake can also be used to make sidewalk tiles, thus avoiding secondary pollution.
The newly invented SPR sewage purification technology has the advantages of simple and reliable process, low investment and operation cost, less land occupation and good purification effect, which will open up a new way for the reuse of urban sewage in the world today. After the reuse of urban sewage, it provides a second fresh water source for the city and an indispensable condition for the sustainable development of the city, and its economic and social benefits are immeasurable.
Unique technical characteristics of SPR sewage treatment system
1. The mixing of municipal domestic sewage and treatment chemicals is mainly under the joint action of the drug suction pipe in front of the pump, the impeller of the sewage pump, the snake-shaped reaction tube and the porcelain ball reaction tank, according to the turbulent speed, mixing time
And the design of hydraulic structure data can be fully mixed, which creates a prerequisite for obtaining the best coagulation purification effect and saving chemicals to the greatest extent. This is impossible for conventional hydraulic structures with primary treatment and secondary treatment in the past.
2. When 2. SPR system is used to treat urban sewage. More than five kinds of sewage treatment agents and their best formula are combined to dissolve organic pollutants and heavy metal ions in sewage through chemical reaction.
However, harmful salts are separated from water and become tiny particles with solid interface (including the function of tertiary treatment of sewage). Among them, an adsorbent with good adsorption effect and low price was selected to adsorb organic pollutants and chromaticity.
. Disinfectant can kill bacteria and Escherichia coli within 30 minutes. Through physical and chemical adsorption of coagulation, suspended solids and various impurities condense into large and dense flocs.
. In this way, the way of using drugs to exert their independent functions and the cross-linking between them are different from the conventional physical and chemical methods. In addition, the combined drug formulation used in the SPR system
It can only play a full role in the SPR sewage purifier and its system with very fine hydraulic parameters design, but can not be used in the conventional hydraulic system.
3. number three. SPR system device can accurately add coagulant and flocculant with the help of atmospheric pressure and flowmeter according to the formula obtained from simulation test.
The medicine will not remain in the purified water due to excessive dosing, and the power consumption is very small.
The internal structure of 4.4. SPR sewage purifier is designed accurately according to coagulation mechanism, and the vortex formed and the appropriate water flow speed of each part make the rubber particles collide the most times.
, and has the best speed environment for coagulation and adsorption. Therefore, a very sufficient condensation effect is obtained in a very small volume. This is also unmatched by traditional hydraulic devices.
5. According to the actual situation of flocculation, the hydrodynamic data inside the SPR sewage purifier are accurately determined, so that a dense suspended mud layer with a thickness of several tens of centimeters is formed in the middle and upper part of the tank.
. All condensed sewage must be filtered by the suspended mud layer before it can flow to the clear water collection area located at the upper part of the water tank. It has successfully played an extremely important role in the advanced treatment of sewage.
This dense suspended mud layer is composed of flocs formed by sludge in sewage and coagulant itself. With the movement of floc from bottom to top, the lower surface of mud layer increases and thickens; meanwhile
The bypass flow of the tank formed by the principle of filtration hydraulics leads the upper surface layer of the suspended mud layer to continuously flow into the central mud receiving barrel, and the upper surface layer is continuously thinned. In this way, the thickness of the suspended mud layer reaches a dynamic balance.
. When the coagulated effluent passes through the suspended mud layer from bottom to top, the floc filter layer separates the suspended colloidal particles, flocs and flocs through the physical adsorption and electrochemical characteristics of the interface and van der Waals force.
Impurities such as bacteria and thallus are all trapped in the suspended mud layer, and the effluent quality reaches the tertiary treatment level. Because the mud layer is composed of high-density flocs, the filtration efficiency is much higher than that of conventional sand layer filtration.
; Because the suspended floc mud layer is used as the filter layer, the head (resistance) loss of filtration is very small, so the power consumption is much lower than that of conventional sand layer filtration and microporous filtration.
Or reverse osmosis membrane filtration; Because the filter mud layer is automatically added and taken away by the sludge in the sewage during the purification process, that is, the filter mud layer itself is constantly updated.
The filter mud layer always maintains a stable thickness and stable physical adsorption and electrochemical adsorption performance, so a stable filtration effect can be obtained.
. But also completely eliminates the necessary backwashing of the filter layer in the traditional system and many troubles caused by backwashing. This structure and principle are completely different from the traditional sewage tertiary treatment and filtration device.
There are no expensive equipment such as reverse osmosis membrane filtration, microporous filtration and activated carbon filtration. Therefore, saving investment, low power consumption and low operating cost are the inevitable advantages of SPR system.
6.6 Flocculants selected. SPR system is also a good sludge filter aid, so the sludge slurry finally discharged from the system has good dewatering performance, and no additional filter aid is needed.
Directly pumped into the filter press for dehydration. Mud cakes can be made into sidewalk tiles for reuse, which will not bring about the problem of secondary pollution. It has no fatal weakness of high water content and poor dewatering performance of sludge produced by traditional biochemical methods.
7. This type of sewage purifier has been started to treat pig farm sewage, chicken farm sewage, coal mine tunnel sewage, pig slaughterhouse sewage and sorghum distiller's grains sewage.
Wastewater containing a lot of organic pollutants and ammonia nitrogen, such as textile printing and dyeing wastewater, recycled paper papermaking wastewater and urban domestic sewage; It has also been successfully applied to the purification and reuse of sewage with high suspended solids content, such as sewage from ceramic factories, wall and floor tile factories, marble polishing sewage, coal washing sewage, wet dust removal sewage from coal-fired boilers, quartz sand washing sewage and so on.
The authoritative testing departments in various places have tested the relevant data of sewage purifiers entering and leaving the water. The test report shows that the ammonia nitrogen removal rate can reach 85%, the total nitrogen removal rate can reach 95%, and the organic nitrogen removal rate can reach 96%.
The removal rate of BOD can reach 95%, the removal rate of suspended solids can reach 98.3% ~ 99.6%, and the turbidity of effluent can reach below 3 degrees (3 mg/L). This is the low investment of this water purification system.
And low operation cost. This is not achieved by the primary and secondary treatment systems of conventional physical and chemical methods and biochemical methods.
In addition to the special urban domestic sewage pipeline system in developed countries, the actual urban sewage is often mixed with a large amount of industrial sewage. It is a reality that the biodegradability is poor and the composition of pollutants changes irregularly and rapidly, but the growth and reproduction process of microorganisms that degrade some organic pollutants is too long. Therefore, the traditional biochemical system is difficult to adapt to the sewage in today's increasingly industrialized cities. SPR system has the adaptability to treat a variety of industrial sewage and the rapid response ability of physical and chemical methods. It is easy to cope with the change of sewage quality at the entrance of the system by automatic means and maintain a stable purification effect.
8. When adding disinfectant to SPR system, ammonia can be removed by chlorine oxidation as long as the dosage of chlorine is increased (no additional equipment is needed), which further improves the ammonia nitrogen removal efficiency of sewage treatment system.
9. If the ammonia nitrogen content of the effluent treated by the SPR system does not meet the strict requirements (for example, the emission standards of some developed countries or regions stipulate that the ammonia nitrogen content is below 1mg/L).
Alternatively, a primary ion exchange device can be arranged in series to finally remove ammonia nitrogen through clinoptilolite ion exchange columns.
Because clinoptilolite ion exchange system requires that the suspended matter content of inlet water should be less than 35 mg/L, otherwise it will affect the function and life of ion exchange column, thus greatly increasing the operating cost of ion exchange. get through
It is difficult for traditional primary and secondary sewage treatment devices to reach such pretreatment level for a long time, which limits the wide application of ion exchange to remove ammonia nitrogen. at present
SPR sewage treatment system can absolutely ensure that the content of suspended solids in purified effluent is less than 3mg/L (in actual operation, the content of suspended solids in effluent is mostly 1mg/L).
The load of ammonia nitrogen removal in the subsequent clinoptilolite ion exchange system is greatly reduced, and the service life of the exchange column will be greatly prolonged, that is, the operating cost of ion exchange will be greatly reduced.
The advantages of ion exchange technology for removing ammonia nitrogen will be fully exerted.
As early as 1970s, Rosemann Sewage Treatment Plant in Minneapolis, Minnesota, USA used pure physical and chemical methods to treat municipal domestic sewage.
The technological process is chemical coagulation-precipitation-filtration and activated carbon adsorption-clinoptilolite ion exchange. The final effluent quality standards are: ammonia nitrogen 1 mg/L, BOD10 mg/l.
, phosphorus 1 mg/L, suspended matter 10 mg/L, pH 8.5. It is proved that the pure physical and chemical method is technically feasible to treat urban sewage. Now, relying on the newly invented SPR water purification technology
, will make the economy of this process more complete.
10 。 In fact, the content of suspended solids in the effluent treated by SPR sewage purification system is less than 3 mg/L, and the turbidity is less than 3 degrees (mg/L), which meets the tap water standard.
It won't block the water pipeline again, and it has been well disinfected. It is very safe and reliable to send this effluent back to all parts of the city as irrigation water for urban lawn green space and tree greening.
. The residual nitrogen content in the effluent treated by SPR system is already very low, so it is not necessary to remove nitrogen as a nutrient for plant growth or so cleanly.
Yes Therefore, the investment and operation cost of advanced denitrification treatment can be avoided, which not only ensures the environmental quality, but also saves a lot of money for the society. Use this reclaimed water instead of tap water as urban greening water.
, will greatly save the city's fresh water resources, reduce the water supply pressure of the city's municipal departments, and will certainly produce great benefits to the overall economic development of the city. This is a new concept of urban sewage reuse.
1 1 。 This purely physical and chemical sewage treatment system is less affected by weather, environment and human factors, and the control ability and flexibility of operators on the treatment system are much better than those of biochemical methods.
As we all know.
The process flow of urban domestic sewage treatment plant can adopt the following new modes:
Scheme [1]: General city: After the sewage is treated by SPR system, it can be reused for urban greening, watering grassland trees or as industrial water.
Urban domestic sewage storage and regulation tank: SPR sewage treatment system-sludge dewatering-sludge making sidewalk.
Wastewater can be reused for watering urban grasslands and trees, or as industrial water.
Scheme [2]: Cities with special requirements: After domestic sewage is treated by SPR system, ammonia nitrogen is removed by ion exchange, and finally discharged into the sea or reused.
Urban domestic sewage storage and regulation tank: SPR sewage treatment system-sludge dewatering-making sidewalk tiles from sludge.
Ammonia nitrogen is removed by clinoptilolite ion exchange, and the effluent is discharged into the offshore, or reused for watering urban grasslands and trees, or used as industrial water.
If the relevant departments can help create some simple conditions for the live performance, they can transport a set of water treatment capacity 10 ~ 20 cubic meters/
SPR sewage purifier and its complete supporting system went to the site to perform the continuous start-up operation of urban sewage purification treatment, and explained the purification mechanism in detail by playing videos and slides.
At the same time, please ask the local authoritative water quality testing department to carry out water quality testing of purification effect. The maximum overall dimension of the whole device is 3m long, 1.4m wide and 2.4m high, and the total weight is less than one ton.
On the basis of successful technical demonstration, we will work closely with local environmental protection departments and industries to build urban domestic sewage treatment plants based on local scientific and technological strength and manufacturing capacity.
In addition, SPR system can also be used for purification and self-circulation of park lake water in urban areas. It is hoped that the urban sewage treatment plant to be built will become a model of urban domestic sewage treatment technology in the world after adopting SPR sewage treatment technology.
If the SPR sewage treatment system is added as the final advanced treatment device on the basis of the existing primary and secondary urban sewage treatment system, the effluent can meet the standard of industrial tap water, thus achieving the purpose of final effluent reuse, which is also an excellent scheme to upgrade the existing urban sewage treatment system.
Three. Baileke sewage treatment technology
L, BIOLA process characteristics
Baileka process is a multi-stage activated sludge wastewater treatment system with phosphorus and nitrogen removal functions. It is a sewage treatment system developed by using natural soil pond as reaction pond. From 1972, after years of research, an activated sludge treatment system with certain characteristics has been formed, which adopts a soil pond structure, adopts a mobile aeration chain floating on the water surface, and hangs a microporous aeration head at the bottom.
The construction investment is greatly reduced by using soil pond, and the brick removal efficiency of oxygen is further strengthened by using aeration chain aeration system, which reduces the operation cost and greatly improves the treatment effect. The process design is simple, without complicated management, and it has great economic and social benefits under suitable conditions.
1. 1 low-load activated sludge process
Baileka process has large sludge reflux, high sludge concentration, large biomass and long relative aeration time, so the sludge load is low. The sludge loading rate of BOD5 in Longtian Sewage Treatment Plant is
0? 05kgBOD/kgMLSS.d, sludge concentration of 400Omg/L, sludge age of 29 days, and little excess sludge.
1.2 The aeration tank adopts taxi structure.
According to the National Environmental Protection Agency 1992 "Investigation and Research on Industrial Wastewater Treatment Facilities", 54% of the funds for industrial wastewater treatment facilities in China are used for civil facilities, while only 36% are used for equipment, which leads to this kind of situation.
The main reason for this investment allocation model is that most process tanks use expensive reinforced concrete tanks. The civil construction cost of Longtian Sewage Plant is 5 million yuan, accounting for only 20% of the total investment.
Large reinforced concrete ponds are not only expensive, but also difficult to build. However, for many aeration processes, the soil pool is not considered, because the soil pool will cause groundwater erosion, and it is very difficult to install the aeration head on the basis of the soil pool.
In order to reduce investment, Beleca technology has done a lot of work on the aeration tank to study the structure of the soil tank. One is to separate sewage and groundwater with HDPE impervious membrane, and the other is to avoid drilling holes in the bottom wall of the tank by the microporous aeration head suspended on the floating pipe.
This kind of earth tank with HDPE impervious membrane is not only easy to excavate and low in investment, but also can fully meet the functional requirements of sewage treatment tank and adapt to local conditions and site topography. Its advantages are more fully reflected in some special geological conditions, such as earthquake-prone areas and loose soil areas. The service life of HDPE impervious membrane soil pool is much longer than that of reinforced concrete pool.
1.3 high-efficiency aeration system
The structure of Baileka aeration system is that the aeration head is suspended on the floating chain and stays at the water depth of 4-5m. When bubbles escape from its surface, the diameter is about 50um. Such tiny bubbles mean the increase of oxygen contact area and the improvement of oxygen transmission efficiency. At the same time, because the bubbles are constantly disturbed by the water flow and the swing of the floating chain, the bubbles do not move vertically upward, but obliquely, thus prolonging the residence time in the water and improving the oxygen transfer efficiency. The operation shows that the oxygen permeability of Baileka suspension chain is much higher than that of ordinary aeration process and fixed micropore aeration process at the bottom. Baileka aeration heads are hung on floating chains, which are loosely fixed on both sides of the aeration tank, and each floating chain can make a serpentine movement in a certain area of the tank. During the movement of aeration chain, its natural swing can achieve good mixing effect and save the energy needed for mixing.
The energy consumption required for stirring in the aeration tank of Beleka system is only 1? 5W/m3, while the energy consumption of conventional aeration method is l0-l5W/m3. Because of the special structure of Biorak)-Friox, the aeration head will not be blocked even in a very complicated environment, which means that the aeration device can run for several years without maintenance, and the required maintenance cost is very small.
The aeration system and supporting high-efficiency blower ensure high oxygen transfer efficiency, and the oxygen supply capacity is 2? 5kgO2/kW？ H), and the traditional sewage treatment plant this value is lkgO2/lkW? H) The blower is located at the edge of the pool, which reduces the cost of the blower room and air conveying pipeline.
1.4 Simple and effective sludge treatment
Another characteristic of Baileka process is that the amount of sludge returned is large, and its residual sludge is much less than that of traditional process.
Under the condition of constant load, the retention time of sludge in the aeration tank of Baileka process is several times that of traditional process. Because the sludge in the sludge pool is completely stable, it will not rot, and even if it is stored for a long time, it will not produce odor, which is why the sludge is easier to treat than the traditional process. Moreover, the sludge pool can be made into a soil pool structure, which saves the cost of building a factory.
1.5 Simple and easy to maintain
Baileka system has no underwater fixed parts, so it is not necessary to drain the water in the pool during maintenance, but to hoist the aeration head under the aeration chain to the maintenance site by boat. Practice shows that aeration does not need any maintenance in the first few years, mainly because the aeration pipe is made of very fine fibers (about 0? 003mm), and filled with polymer, in order to achieve the purpose of waterproof and dustproof. At the same time, the aeration head has about 80% free space and 20% surface area, which is just the opposite of the traditional aeration head. Therefore, the area where microorganisms can grow is very small and can be easily removed. When the aeration head must be repaired, it will not affect the operation of the whole sewage treatment plant. There are few moving parts and aging parts in this process. Use reliable and durable materials when selecting equipment and materials. This process doesn't need much automation. It does not need any fragile detectors or any complicated control systems, and the operation of these control systems also requires special technology and expensive accessories.
1.6 secondary aeration safety pool
In order to ensure the water quality when the load changes, the Baileka process uses a relatively independent tank for secondary aeration to ensure the cleanliness of the effluent and sufficient dissolved oxygen in the water.
1.7 secondary sedimentation tank
Sludge generated in the aeration tank is separated in the secondary sedimentation tank and returned to the aeration tank to participate in sewage purification. Part of the secondary sedimentation tank and aeration tank of Baileka process are combined into one, which further saves the civil construction cost and occupied area. The sludge settled in the secondary sedimentation tank is discharged into the sludge tank for reflux through a floating sludge scraper and a sludge suction machine.