Anaerobic wastewater treatment has a good reputation for efficient and low-odor treatment of rivers containing high concentrations of organic pollutants. If you are studying biological treatment processes, you will undoubtedly ask questions such as "What is anaerobic wastewater treatment?" And "How does anaerobic wastewater treatment work?"
This article will give an approachable introduction to anaerobic treatment and divide it into three parts to help you clarify how it works and why you use it.
1. What is anaerobic wastewater treatment?
2. How does anaerobic wastewater treatment work?
3. Common types of anaerobic wastewater treatment systems include
4.What Aquasust could help you on anaerobic wastewater treatment?
What is anaerobic wastewater treatment?
Anaerobic wastewater treatment is a biological process in which microorganisms degrade organic pollutants in the absence of oxygen. In the basic anaerobic treatment cycle, wastewater enters the bioreactor vessel. The bioreactor contains a thick semi-solid substance called sludge, which is composed of anaerobic bacteria and other microorganisms. These anaerobic microorganisms or "anaerobic bacteria" digest the biodegradable substances present in the wastewater, thereby producing lower biological oxygen demand (BOD), chemical oxygen demand (COD) and/or total suspended solids (TSS) The effluent is used as a by-product of biogas.
Anaerobic wastewater treatment is used to treat various industrial wastewater from agriculture, food and beverages, dairy products, pulp and paper, and textile industries, as well as municipal sewage sludge and wastewater. Anaerobic technology is usually used for streams with high concentrations of organic substances (measured as high BOD, COD or TSS), usually before aerobic treatment. Anaerobic treatment is also used for special applications, such as the treatment of waste streams with inorganic or chlorinated organics, and is very suitable for treating warm industrial wastewater.
How does anaerobic wastewater treatment work?
Anaerobic wastewater treatment is a biological treatment in which anaerobic microorganisms are used to decompose and remove organic pollutants in wastewater. Although anaerobic treatment systems can take many forms, they usually include some form of bioreactor or storage that can maintain the oxygen-free environment needed to support the anaerobic digestion process.
The anaerobic wastewater treatment process includes two stages: the acidification stage and the methane production stage, both of which are in a dynamic equilibrium state. In the initial acid formation stage, anaerobic bacteria decompose complex organic compounds into simpler short-chain volatile organic acids. The second stage, called the methane production stage, consists of two steps: acetic acid production, anaerobic bacteria synthesize organic acids to form acetate, hydrogen and carbon dioxide; and methane production, and then anaerobic microorganisms act on these newly formed molecules , Forming methane gas and carbon dioxide. These by-products can be recycled for use as fuel, and wastewater can be used for further treatment and/or discharge.
According to specific application requirements and facility requirements, anaerobic digestion systems can be designed as single-stage or multi-stage devices, which means they can be equipped with separate acidification tanks and bioreactor devices.
Common types of anaerobic wastewater treatment systems include
Anaerobic lagoon
Anaerobic lagoons are large man-made ponds, usually between 1-2 acres in size and up to 20 feet deep. They are widely used in the treatment of agricultural wastewater from meat production, as well as the treatment of other industrial wastewater streams, and as a primary treatment step for urban wastewater treatment. Wastewater is usually piped to the bottom of the lagoon, where it settles to form an upper liquid layer and a semi-solid sludge layer. The liquid layer prevents oxygen from reaching the sludge layer, allowing the anaerobic digestion process to decompose the organic matter in the wastewater. On average, this process may take as little as a few weeks or as long as six months to bring the BOD/COD level to the target range. Anaerobic bacteria are beneficial to certain environmental conditions, such as warm water temperature (85-95° F) and near-neutral pH. Therefore, maintaining optimal conditions will increase the activity of anaerobic microorganisms, thereby reducing wastewater retention time. The rate of anaerobic respiration may also be limited by many factors, including fluctuations in BOD/COD concentration and the presence of substances such as sodium, potassium, calcium, and magnesium.
Anaerobic sludge bed reactor
The sludge bed reactor is an anaerobic treatment in which wastewater passes through a free-floating "blanket" of suspended sludge particles. When the anaerobic bacteria in the sludge digest the organic components in the wastewater, they multiply and collect into larger particles, which settle to the bottom of the reactor tank and can be recycled for future recycling. The treated sewage flows upwards out of the device. The biogas generated during the degradation process is collected by the collection cover during the entire treatment cycle.
There are several different forms of anaerobic sludge bed reactors, including
Upflow Anaerobic Sludge Bed (UASB): In UASB treatment, wastewater is pumped into the bottom of the UASB bioreactor and applied upward flow. When wastewater flows through, this causes the sludge layer to float.
Expanded granular sludge beds (EGSBs): EGSBs are very similar to UASB technology. The key differentiating factor is that wastewater is recycled through the system to promote more contact with the sludge. They are also generally higher than UASB, and the influent flow continues at a higher speed. Therefore, compared with the UASB system, the EGSB can handle streams with higher organic content.
Anaerobic Baffle Reactor (ABR): The ABR is composed of semi-enclosed compartments separated by alternating baffles. The baffle interrupts the smooth flow of wastewater and promotes more contact with the sludge layer when the sludge flows from the reactor inlet to the outlet.
Anaerobic filtration reactor
The anaerobic filtration reactor consists of a reactor tank equipped with a certain fixed filter medium. Anaerobic microorganisms are allowed to establish themselves on the filter media, forming so-called biofilms. Filter media varies from system to system. Common materials include plastic films and particles, as well as gravel, pumice, bricks, and other materials. New filter media must be inoculated with anaerobic bacteria, and it may take several months for the biofilm to build up to the point where it can be processed at full capacity.
During the treatment cycle, the wastewater stream passes through a filter medium, which is used to capture particles in the stream while also providing sufficient surface area to expose the anaerobic bacteria in the biofilm to the organic materials present in the stream. Over time, the performance of the filtration reactor must be carefully monitored, because the filter media will eventually become clogged by excessive biofilm and particle accumulation, and maintenance steps such as backwashing and cleaning are required to maintain optimal performance.