Anaerobic wastewater treatment is best for effective, odour-free treatment of sewage streams, with high levels of organic pollutants. This article will give a clear overview of anaerobic bacteria in sewage treatment plants, and the working of anaerobic treatment in sewage treatment plants.
What is anaerobic wastewater treatment?
In anaerobic wastewater treatment, bacteria break down organic pollutants during the biological process in the absence of oxygen. Wastewater enters a bioreactor container in a simple anaerobic treatment cycle. Sludge, a thick, semi-solid substance found in the bioreactor, is made up of anaerobic bacteria and other microorganisms.
By breaking down the biodegradable material in the wastewater, these anaerobic bacteria, also known as "anaerobes," produce an effluent with decreased biological oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solids (TSS), as well as biogas by-products.
Application of anaerobic wastewater treatment
In addition to treating municipal sewage sludge and wastewater, anaerobic wastewater treatment is utilised to treat a range of effluent streams from the agricultural, food and beverage, dairy, pulp and paper, textile industries, etc.
For streams with high levels of organic matter (measured as high BOD, COD, or TSS), anaerobic methods are often used, frequently before aerobic treatment. Warm industrial wastewater is well suited for anaerobic treatment, which is also employed for specialised applications, such as the treatment of waste streams with inorganics or chlorinated organics.
How does anaerobic treatment work in Sewage Treatment Plant?
Anaerobic bacteria are employed to decompose and eliminate organic pollutants from wastewater, during this sort of biological treatment. While, there are many different types of anaerobic treatment systems, they typically contain a bioreactor or repository that can maintain the oxygen-free atmosphere, required to sustain the anaerobic digestion process.
1: The two steps of the anaerobic wastewater treatment process are acidification and methane generation, which both take place in a dynamic equilibrium.
2: Anaerobes convert complicated chemical molecules into more straightforward, short-chain volatile organic acids during the initial acid-forming stage.
3: The second phase, also referred to as the "methane-production phase," is divided into two stages: acetogenesis, in which anaerobes create organic acids to produce acetate, hydrogen gas, and carbon dioxide; and methanogenesis, in which anaerobic microorganisms act on these recently created molecules, to produce methane gas and carbon dioxide.
4: While, the wastewater can be sent for additional treatment or release, the by-products can be recycled for use as fuel.
Types of anaerobic wastewater treatment systems
Anaerobic digester systems can be built as single or multi-stage units, which means they can be set up with a separate acidification tank and a bioreactor unit, depending on the particular application needs and facility requirements.
The following are examples of common anaerobic wastewater treatment systems:
· Anaerobic lagoons
Anaerobic lagoons are man-made ponds that can be up to 20 feet deep and are normally between 1-2 acres in size. They are frequently employed as the first stage of municipal wastewater treatment, as well as for the treatment of various industrial wastewater streams, and agricultural wastewater.
Typically, wastewater is routed into the lagoon's bottom, where it congeals into an upper liquid layer and a semi-solid sludge layer. Anaerobic digestion can take place to break down the organic elements in the wastewater, because the liquid layer prevents oxygen from reaching the sludge layer.
BOD/COD levels can be brought to the desired range using this approach in less than few weeks, or as long as six months on average. Maintaining ideal circumstances will increase the rate of anaerobic microbe activity, leading to a shorter wastewater detention time.
Factors affecting anaerobic digestion in anaerobic lagoons
Anaerobes like particular environmental conditions, such as the warm water temperatures ranging from 85 to 95° F, as well as near-neutral pH value. Several other factors, such as variations in BOD/COD concentration and the presence of chemicals like sodium, potassium, calcium, and magnesium, can also slow anaerobic respiration down.
· Anaerobic filter reactor
A reactor tank with a set filter media makes up anaerobic filter reactors. On the filter media, anaerobic microorganisms are permitted to establish their presence, creating a biofilm. The materials used as filter media vary from system to system, but common ones include gravel, pumice, bricks, and plastic films and particles.
Anaerobes must be introduced to fresh filter medium, and it may take a while for the biofilm to form itself and be fully functional for treatment. The filter medium, which serves to catch stream particles and also provides a lot of surface area for exposing anaerobes in the biofilm to the organic compounds in the stream, is passed through the wastewater stream as it goes through the treatment cycles.
Performance of the filter reactor must be constantly monitored over time since the filter media, will eventually clog with too much biofilm and particulate build-up, necessitating maintenance procedures like backwashing and cleaning to keep it operating at its best.
· Anaerobic sludge blanket reactors
Anaerobic treatment methods like sludge blanket reactors carry wastewater, through a suspended "blanket" of free-floating sludge particles. Anaerobes in the sludge grow and accumulate and form larger granules that sink to the bottom of the reactor tank, and can be recycled for subsequent cycles.
The cleaned effluent rises and exits the unit. Throughout the course of the treatment cycle, collection hoods are used to collect the biogas produced by the degradation process.
There are several varieties of anaerobic sludge blanket reactors, including:
1: Upflow anaerobic sludge blanket (UASB) treatment: It involves pumping wastewater into the bottom of a UASB bioreactor, while applying an upward flow. This makes the sludge blanket float as the wastewater passes past it.
2: Expanded granular sludge beds (EGSBs): The wastewater is circulated repeatedly to encourage more contact with the sludge. Moreover, they are typically taller than UASBs and can sustain faster influent flows. EGSBs are able to treat streams with higher loads of organics.
3: Anaerobic baffled reactors (ABRs): These are made up of compartments that are semi-enclosed and divided by alternating baffles. The baffles prevent the wastewater stream from flowing smoothly from the reactor's input to output, promoting more contact with the sludge blanket.
Leading manufacturer of sewage treatment plants
Municipalities and industries can contact Netsol Water water treatment experts, for a variety of advanced treatment techniques including aerobic and anaerobic wastewater treatment. We also have experience in custom-designing and producing biological wastewater treatment systems for a variety of industries.
We also have been providing wastewater treatment services to municipalities for many years. These services include water clarifying, sludge dewatering, chlorination and de-chlorination, phosphorus removal, odour control, etc. Call us at +91 9650608473 or email at enquiry@netsolwater.com for further information.
