What are the sewage treatment processes？
The demand for sewage treatment is accompanied by the birth of the city. Urban sewage treatment technology has undergone hundreds of years of changes, from the initial first -level treatment to the current third -level treatment, from simple disinfection to organic matter removal, nitrogen dehydration and phosphorus and then deep treatment. Among them, the advent of the active sludge method is even more of the epoch -making significance, and this year is the 100th anniversary of the birth of the active sludge law. How will urban sewage treatment technology develop in the future? In this regard, let's review the road where urban sewage treatment has gone in those years.
First -level treatment stage
The history of urban sewage treatment can be traced back to the ancient Rome period. At that time, the environmental capacity was large, and the self -purification ability of water bodies could also meet human water needs. People only need to consider drainage problems. Later, the process of urbanization accelerated, and domestic sewage caused by spreading bacteria that caused the spread of infectious diseases. Out of health considerations, humans began to deal with discharged domestic sewage. Early treatment methods were used to precipitate or disinfect them with lime, alum, etc. In the late Ming Dynasty, there were already sewage purification devices in my country. However, due to the lack of demand at that time, my country's domestic sewage was still mainly agricultural irrigation. In 1762, the United Kingdom began to use lime and metal salt to treat urban sewage.
Two-level treatment stage ----- organic matter removal process
In the middle of the eighteenth century, the European Industrial Revolution began. Among them, organic matter in urban domestic sewage became the focus of removal. In 1881, French scientists invented the first biore reactor, which was also the birth of the first anaerobic biological treatment pool -MORIS Pond, which opened the prelude to the biological method of processing sewage. In 1893, the first biological filter was put into use in Wales in the UK and quickly promoted in Europe and other countries in Europe. The development of technology has promoted the production of standards. In 1912, the Royal Sewage Treatment Commission proposed to evaluate the pollution of water quality by BOD5.
In 1914, ARDEN and LOKETT published a paper on the active sludge method in the British Chemical Engineering Society. Essence Two years later, the United States officially established the first active sludge sewage treatment plant. The birth of the active sludge method has laid the foundation of urban sewage treatment technology in the next 100 years. At the beginning of the birth of the active sludge method, the charging-row process was used. At that time, the automatic control technology and equipment conditions were relatively backward, resulting in cumbersome operations, easy blocking, and no obvious advantages compared to biological filters. After that, the continuous push -type activated sludge method (CAS method) quickly replaced it after the appearance, but because the oxygen consumption speed of the sludge in the push -type reactor changed the length of the pool Cooperate, the active sludge method is facing the problem of insufficient local oxygen supply. In 1936, the aerated activity sludge method (TAAS) and the stage aeration method (SFAS) proposed in 1942 improved the oxygen supply balance from the aeration and water inlet methods. In 1950, McGoni in the United States proposed a complete mixed -type activated sludge method. This method can effectively solve the problem of sludge expansion by changing the survival method of the active sludge microbes to adapt to the gradient changes in the matrix concentration in the aeration tank.
With the widespread application of actual production students and the continuous and technological improvement, in the 1940s and 1960s, the activated sludge method gradually replaced the biofilm method and became the mainstream process of sewage treatment. In 1921, the active sludge law spread to China, and China built the first sewage treatment plant -Shanghai North District sewage treatment plant. In 1926 and 1927, the sewage plant of Shanghai East and Western District was built. At that time, the daily processing volume of three water plants was 35,500 tons.
In the 1950s, the problem of nutritionalization of water bodies was prominent in the 1950s, and nitrogen removal and phosphorus and removing phosphorus became another main demand for sewage treatment. As a result, a series of nitrogen -removing phosphorus removal processes were derived on the basis of the active sludge method.
In the early 1950s, phosphorus was found and used for phosphorus removal.
In 1969, the BARTH of the United States proposed that the three -stage method was used to remove nitrogen. The first section was a good oxygen segment, which mainly removed organic matter. In the second paragraph, it was nitrated by alkaline nitrate.
In 1973, on the basis of the original process, Barnard completely separated the hypoxia and the oxygen reactor, the sludge returned to the hypoxic reactor, and added an internal reflux device to shorten the process. Good oxygen (A/O) process.
In the 1970s, American experts, on the basis of the A/O process, plus phosphorus removal became the A2O process. The Guangzhou Datan Sha Sewage Treatment Plant, which was established in my country in 1986, used the A2O process. At that time, the design and processing water was 150,000 tons. It was the largest sewage treatment plant in the world at that time.
The A2O process of the oxidation trench process is to divide the biological treatment of anaerobic section and the good oxygen segment, while the oxidation sulcus is a closed ditch -type structure, combining the characteristics of push -flowing and complete hybrid activity sludge methods. Qi, precipitation and sludge stabilize. The mixture of sewage and activated sludge is continuously circulating, and the system can form anoxy areas and hypoxic areas, thereby achieving biological nitrogen removal and phosphorus. The oxidation sulcus was puzzled during the day, and it was used as a sedimentation tank at night. Compared with the active sludge method, it has the advantages of simple processing technology and simple structure, long age, less residual sludge, easy dehydration, and stable treatment effect.
In 1953, the Pasveer Institute of the Public Health Engineering Research Association of the Netherlands proposed the oxidation groove technology, also known as the "Paswell ditch". In 1954, the first oxidation groove sewage treatment plant was built in Voorshoten, the Netherlands, when the service population was only 360. In the 1960s, this technology was rapidly promoted and applied in Europe, North America, and South Africa. According to statistics, as of 1977, more than 2,000 Paswell oxidation sulcus was put into operation in Western Europe. In 1967, the Dutch DHV company developed and developed Carroussel's oxidation grooves. It is a ditch system composed of multiple channels. The development of Karuser oxidation grooves has gone through three stages: ordinary Caruser oxidation groove, Caruser 2000 oxidation groove, and Karusel 3000 oxidation groove. In 1970, ENVIREX in the United States launched the production of ORBAL oxidation grooves. It consists of 3 concentric garden -shaped or oval channels, which are connected between various channels. The exterior channels are introduced first. While continuously circulating, it enters the next channel in turn, which is equivalent to a series of complete mixed reaction pool connecting series in series in series. Together, finally from the center channel. The alternate work oxidation groove is developed by the Dan Daguger Company. This process has low cost and easy maintenance. Usually there is a dual ditch alternation and Sanlou alternate (T -type oxidation groove) oxidation trench system and semi -alternative working oxidation ditch.
The two sections of the two sections of the two -stage method only connect a set of two groups of active sludge methods in series. The first and second aeration pools are the same, and most of the organic matter is adsorbed and degraded in the first section. The load of the second -stage sludge is very low, and its water quality is better than the single -level active sludge method of the same volume air. However, as the volume of the first aeration pool has doubled, it is equivalent to double the load of the sludge. It is in the stage of susceptible expansion, and it is difficult to operate management.
In the mid -1970s, Professor Botho Bohnke in Germany developed the AB process. This process further increases the first section of the sludge load on the basis of the traditional two -stage method, and runs in a high load and short mud age. The age of the mud is long. Due to the short -term age and the large amount of mud, the removal effect of the phosphorus is very good. After removing a large number of organic matter after section A, the volume of sections B can be greatly reduced. Water quality. However, due to the removal of a large amount of organic matter in section A, the lack of carbon source B, so the advantages of this process when dealing with low concentrations of urban sewage are not obvious. Later, in order to solve the age of nitrifying bacteria during nitrogen dehydration, the AO-A2O process was developed by the contradiction between the short mud age when the phosphorus removal was removed. This process consists of two relatively independent nitrogen dehydration and phosphorus removal processes. The first section of mud is short and is mainly used for phosphorus removal. The second section of mud age and low load are used for nitrogen dehydration.
On the basis of the AO-A2O process, Austria has developed a Hybrid process. There are three internal refund devices between the two sections of this process. Provide carbon source. The first paragraph is mainly to remove organic matter and phosphorus. The second paragraph is the nitrification function, and rely on the first aeration tank to refuse the mixture to nitrate and remove nitrogen.
The SBR process batch activity sludge method (SBR) process is to divide the anaerobic segment from the good oxygen segment in time. In the early 1970s, it was developed by Irvine. It has only one basic unit in the process, which combines the functions of adjustment pools, aeration tanks, and the second sink pool. The operation process of the classic SBR reactor is: water inlet → aeration → precipitation → water water → standby
In the early 1980s, the continuous Iceas craftsmanship was born. On the basis of the traditional SBR process, this process adds a partition wall to the reaction pool to separate the reaction pool into a small -volume pre -reacting area and a large -volume main response area. The small holes enter the main response area at the speed of layer flow, solving the problem of intermittent water inlet. Subsequently, Professor Goranzy developed the Cass /Cast process. Similar to the IceAS process, an optional section is added in the front section of the reaction pool. The sewage first mixes with the return hybrid fluid from the main response zone. Under anaerobic conditions, the selection section is equivalent to the anaerobic tank of the front. Phosphorus creates favorable conditions. In the 1990s, the Sigus company in Belgium developed the Unitank system on the basis of Sanyou oxidation. It consists of 3 rectangular pools, of which the rectangular pool on both sides of the outside can be used as both aeration and sedimentation tanks. A rectangular pool in the middle is only used as an aeration tank. Space push is effectively combined. The MSBR method is an improved SBR (Modify SBR), which uses a single pool multi -style method to combine the advantages of traditional activated sludge methods and SBR technology. The reactor is composed of aerated grid and two alternating sequential processing grids. The main exposure grid maintained continuous aeration throughout the operating cycle, and every half of the cycle, the two sequential batch processing grid alternatives were used as SBR and clarification pools. This process can be continuously water -in and can use less connecting pipes, pumps and valves.
In recent decades, the shortage of energy and resources has attracted widespread attention. Further nitrogen removal and demand for energy conservation and resource recovery has become the mainstream direction of the development of sewage treatment technology. A group of emerging nitrogen removal and phosphorus removal technology are applied.
Anammox-Shaaron combination technology In 1994, DELETT University developed anaerobic ammonia oxidation (Anammox) technology. Invoasuring environments, anaerobic ammonia oxidation can use ammonium ions (NH4+) to oxidize with nitrite root (NO2-) into Nitrogen.
This process is completely self -supporting compared with the traditional neigizer process, without any organic carbon source. In 1998, the University of Dutch Deelf has developed a Sharon process based on the principle of short -range nitrification and nitrification. The first case was in the DOKHAVEN water plant in Rotterdam, the Netherlands. The basic principle is that in the same reactor, first use nitrifying bacteria to oxidize ammonia to NO2- under the aerobic conditions; then under the hypoxic conditions, the organic matter is nitrized to nitrate nitrite to form nitrogen. The process process is shortened and does not need to be neutralized. Compared with the traditional activated sludge method, it can reduce the oxygen supply by 25%and 40%of the nitrifying carbon source, which is conducive to the recycling and utilization of resources and energy. It is more suitable for urban wastewater with lower concentrations of carbon and nitrogen.
At present, with the Sharon process as the nitrification reactor, the Anammox process is a nitrification reactor, which can save 60%oxygen supply and 100%carbon source compared with the traditional process.
Three -level treatment phase
In the past ten years, as the pollution has intensified, the shortage of water resources, humans have put forward higher requirements for water quality, and the rise of sewage depth treatment and reuse technology. The focus of the sewage treatment plant is no longer the amount of emissions of pollutants, but how to improve water quality. Biofilm and membrane separation technology began to show its unique advantages. In the 1960s and 1970s, biofilm technology developed again with the emergence of new synthetic materials. The main processes include biological filters, biological turntables, biological contact oxidation, biological flow beds, etc.
At present, more membrane processing techniques are mainly micro filter (MF), ultrafiltration (UF), reverse osmosis (RO) and membrane biological reactor (MBR) technology. At the beginning of this century, the "NEWWATER" water plant in Singapore used the method of adding ultrafiltration membrane and reverse osmosis membrane after secondary treatment. Based on history, you can know Xingdu. Looking back at the entire historical process, the footprint of urban domestic sewage treatment is deepened with the needs of human health, the changes in the quality of the water environment, and the degree of sewage treatment. At the same time The continuous evolution of process technology, its operations, land occupation, procedures steps, and energy resources are simplified a little bit. People have higher demand for water quality, while the processing process is becoming more and more simple.
