Introduction to Anaerobic filter reactors
The first work on anaerobic filters date back to last 1960s and ever since they have had a growing application, today representing an advanced technology for the effective treatment of domestic sewage and a wide range of industrial effluents.
Anaerobic filter reactors are made out of a reactor tank and some sort of fixed filter medium. Biofilms are formed when anaerobic microorganisms are permitted to establish themselves on the filter medium. Plastic films and particles, as well as gravel, pumice, bricks, and other materials, are commonly used as filter media in different systems. New filter media must be injected with anaerobes, and it may take several months for the biofilm to develop itself to the point where it can be treated at full capacity.
The wastewater stream is pushed through the filter media during treatment cycles, which captures particles from the stream while also providing adequate surface area for anaerobes in the biofilm to be exposed to organic matter present in the stream. Filter reactor performance must be closely monitored over time, since the filter media will eventually become clogged with excess biofilm and particulate buildup, necessitating maintenance procedures such as backwashing and cleaning.
Although anaerobic filters can be used as the main wastewater treatment unit, these are more appropriate for post treatment, adding operational safety and stability to the treatment system as a whole.
How does anaerobic filter systems work?
A fixed-bed biological reactor having one or more filtration chambers in series is known as an anaerobic filter.
Particles are retained as wastewater passes through the filter, and organic matter is destroyed by the active biomass attached to the filter material's surface. Upflow is the most common mode of operation for anaerobic filters because the fixed biomass is less likely to be washed out.
Various design considerations:
1: To ensure an equal flow regime, the water level should cover the filter medium by at least 0.3 m.
2: The hydraulic retention time (HRT) is the most critical design parameter that affects filter performance. It is suggested that you take HRT for 12 to 36 hours.
3: The ideal filter would have a large surface area for bacteria to grow on, as well as pores that are large enough to avoid clogging. The increased surface area ensures that the organic matter is in contact with the associated biomass, which efficiently destroys it. The material should have a surface area of between 90 and 300 m2 per m3 of occupied reactor volume.
4: The diameter of typical filter materials ranges from 12 to 55 mm. Gravel, crushed rocks or bricks, cinder, pumice, or specifically moulded plastic bits are typically utilized, depending on local availability.
5: Vertical pipes or baffles can be used to create a link between the chambers. For maintenance, access to all chambers (through access ports) is required. The tank should be vented to allow for controlled release of odorous and potentially harmful gases.
Because the slow-growing anaerobic biomass must initially be developed on the filter medium, an anaerobic filter requires a 6 to 9 month start-up period to reach full treatment capacity. The filter can be inoculated with anaerobic bacteria to minimize start-up time, for example, by spraying septic tank sludge onto the filter material.
Over time, the flow should be steadily raised. Because of the sensitive ecosystem, it's important to avoid dumping harsh chemicals into the anaerobic filter.To make sure the tank is working properly, keep an eye on the scum and sludge levels. Solids will block the filter's pores over time. Furthermore, the thickening bacterial clump will break off and eventually clog pores. When the filter's efficiency drops, it needs to be cleaned. This is accomplished by either backwashing the system or removing and cleaning the filter material. Anaerobic filter tanks should be tested for water tightness on a regular basis.
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