What is Anaerobic wastewater treatment?
Anaerobic wastewater treatment is a biological process of degradation of organic contaminants by microorganisms in the absence of oxygen. In anaerobic treatment cycle, wastewater enters a bioreactor receptacle which contains a thick, semi-solid substance known as sludge, comprising of anaerobic bacteria and other microorganisms. These microorganisms, or “anaerobes,” digest the biodegradable matter present in the wastewater, resulting in a wastewater with lower biological oxygen demand (BOD), chemical oxygen demand (COD), and/or total suspended solids (TSS), as well as biogas byproducts.
Anaerobic treatment is used for treatment of industrial effluent streams from agricultural, food and beverage, pulp and paper, and textile industries, as well as municipal wastewater.Anaerobic technologies are specifically deployed for wastewater with high concentrations of organic content.
How does Anaerobic wastewater treatment work?
Anaerobic wastewater treatment is a type of biological treatment using anaerobic microorganisms to break down and remove organic contaminants from wastewater. Anaerobic treatment systems include some form of bioreactorscapable of maintaining the oxygen-free environment needed to support the process of anaerobic digestion.
The anaerobic wastewater treatment process has two stages: an acidification phase followed by a methane production phase, with both processes occurring in dynamic equilibrium.
What are the different types of Anaerobic Digester?
Depending upon application needs and facility requirements, anaerobic digester system can be designed as single- or multi-stage units, i.e.; they can be configured with a separate acidification tank and a bioreactor unit. Common types of anaerobic wastewater treatment systems are:
Anaerobic activated sludge process, Anaerobic filter, Anaerobic lagoon, Imhoff tank, One-stage anaerobic digester, Plug-flow anaerobic digester, Two-stage anaerobic digester, Upflow anaerobic sludge blanket digestion (UASB), Up-flow and down-flow anaerobic attached growth system.
1: Two-stage anaerobic digester
Two-stage anaerobic digestion is a breakthrough in the field of renewable and sustainable energy technology that potentially transforms organic constituents and simultaneously resolves the threat of energy crisis and waste disposal. This type of digester is provided when population ranges from 30,000 to 50,000.
The process followed in two-stage anaerobic digester
In first stage, liquefaction of organic solids mainly takes place, digestion of soluble organic materials and gasification occurs. First stage usually has high rate digester and continuous mixing is preferred.
In second stage, gasification occurs however main use is supernatant separation, gas storage and digested sludge storage. This second stage is a conventional digester type and it is provided with intermittent mixing. Organic loading on first stage is more than second stage.
The anaerobic waste treatment method is effective for the treatment of many organic wastes. The anaerobic treatment of organic wastes results in the production of carbon dioxide and methane and involves two distinct stages.
Firstly, complex components, including fats, proteins, and polysaccharides are hydrolyzed by facultative bacteria. These bacteria then subject the products of hydrolysis to fermentations and other metabolic processes leading to the formation of simple organic compounds, mainly acids and alcohols. The first stage is knownas "acid fermentation".
In the second stage, the end products of the first stage are converted to methane and carbon dioxide by anaerobic bacteria. This stage is known as "methane fermentation"
2: Upflow anaerobic sludge blanket reactor (UASB)
UASB reactor is a widely employed anaerobic system for industrial sewage treatment and has been recognized as the third most popular and extensively used sewage treatment technology.
The process of UASB reactors
In UASB reactor, influent wastewater enters from the bottom and accumulation of anaerobic sludge in the form of granules takes place in the bottom of the reactor and the flow of wastewater is in upward direction through the sludge blanket. In the UASB reactor the anaerobic bacteria form dense granules and it settles and remains as a blanket at the bottom of the reactor.
When the wastewater flows upward through the granules, it consumes the waste and produces methane and carbon dioxide. This gas generated is collected in a gas storage tank, which is further used for the generation of energy. The treated wastewater comes out of the opening at the top, which is then processed further.
UASB type reactor is preferred over the other types of reactors for the anaerobic treatment of industrial wastewaters, as it can work even on high organic loading rates.
3: Downflow anaerobic reactor
Downflow anaerobic filter is similar to trickling filter in operation. DAF is similar to fixed film reactor. The loosely held biomasswithin the void spaces is potentially wiped out of reactor. The specific surface area of media is quite important in DAF as compared to UAF. There is less problem of clogging and wastewater with some SS concentration can be treated using DAF. Water is fed through several points alongthe depth of the filter.
How can Netsol help?
Netsol have expertise in wide range of waste water treatment technologies. We can customize wastewater treatment plants that will cater to all your needs and at the same time effectively treat different types of wastewater. We are dedicated to provide hands on service, expert counselling and training to our valuable customers.