Biological treatment

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Biological treatment uses a variety of biological materials and bacteria that are suitable for residential and commercial areas. In this method, the circulating water is purified due to the presence or absence of oxygen. Aerobic wastewater treatment is divided into two types of adhesive and suspended growth. In suspended growth, there is a system in which wastewater microorganisms remain suspended.
Anaerobic treatment or anaerobic digester, as its name implies, is a set of biological processes that are used to treat industrial and sanitary wastewater without the presence of oxygen. In this method, with the help of bacteria and microorganisms, we will achieve our desired, which is purification. But there is a fundamental difference, and that is the decomposition of organic matter without the help of microorganisms. This method is the most common method for removing organic and solid materials in industrial effluents and sewage. After being hydrolyzed, these organic materials are converted to fatty acids and sugars and converted to methane gas in a process that can be used as fuel in industry. This method is always more popular because it produces less cost and sludge.
In this method, the pH of the wastewater must be measured. The most suitable range for methane-producing bacteria is 6.6 to 7.6. However, excessive concentration of acids in the reactor also disrupts the function of bacteria. This process, like any other reaction, can be affected by temperature changes. Because increasing and decreasing temperature is the main factor in the activity of microorganisms. The temperature in optimal conditions should be in the range of 3 to 40 degrees Celsius.
Anaerobic wastewater treatment
In the UASB (Up Flow Anaerobic Sludge Blanket) method, as the name implies, they treat wastewater with the help of anaerobic pathogenic bacteria. These bacteria convert the organic matter of industrial wastewater into methane gas, which is also a source of energy. This system has a high performance of about 80% by reducing toxic substances and directing them to enter aerobic systems. This system was designed and put into operation in the late 1970s in the Netherlands with the aim of upgrading septic tanks.
The ABR (Anaerobic Baffled Reactor) method using baffled anaerobic reactors plays an important role in the wastewater treatment process. The most important feature of this process is the high speed of purification compared to other anaerobic methods. In this method, the reactors are divided into separate chambers, and the system is much less sensitive to changes than other similar anaerobic devices. Low manufacturing costs and no mechanical mixing system are the advantages of this reactor. Perhaps the most important advantage of this system is its ability to separate the phases of acidogenesis.
UAFB (Up Flow Anaerobic Fixed Bed) method or upward flow adhesive growth method, with the help of reactors that operate in the process of multi-stage digestion, have plastic fillings or P.V.C. They are created for the growth and multiplication of microorganisms, which is usually very fast. They are embedded in the form of matrix plates inside the reactor and these matrices create a suitable substrate for the growth and multiplication of microorganisms. Sludge production in this system is very low and takes up less space than other methods. This process is a simple anaerobic procedure that does not require advanced equipment and technology.
Aerobic wastewater treatment
The most common method of this aerobic treatment is activated sludge process, which has different types. This process is one of the main methods of treating human sanitary wastewater. You may be interested to know that this process was discovered by two British engineers in 1913.
Despite the different types of methods of this treatment process, but the basis of the treatment method is all the same, and that is the loss of 50 to 70% of the total suspended solids after entering the treatment plant. Non-use of chemicals in this method makes it a permanent advantage over other methods of wastewater treatment. There are various parameters in the design of activated sludge processes, including hydraulic retention time (HRT), cell retention time (SRT), and feed to microorganism ratio (F / M).
The main components of the activated sludge process are aeration pool and sedimentation pool. In the aeration pool, the incoming wastewater is thoroughly mixed with the microbial mass and is called mixed liquor. In this part, the desired oxygen is supplied by the ventilation compressor. This liquid must remain in the pool for 5 to 7 hours to become floating sludge and its suspended particles are returned to the aeration pool and the rest is sent to the sludge treatment unit. There are different types of activated sludge process, some of which we will mention.
Among all types of activated sludge processes, conventional activated sludge process with mold flow is the most used in the treatment of various types of wastewater, especially municipal wastewater.
Extensive aeration process is used in the treatment of industrial wastewater, which often contains complex soluble organic matter.
In the gradual aeration process, the intensity of aeration to the sewage along the pool is reduced because the sewage initially needs more oxygen and as the pollution decreases, the need for oxygen in it also decreases.
In the complete mixing process method, the incoming wastewater is immediately mixed with oxygen and bacteria in the aeration basin and the organic load, MLSS and oxygen concentrations become uniform throughout the reactor.
The contact stabilization process uses two separate aeration tanks for wastewater treatment.
The cross-process is a modified form of the aeration process for wastewater with