Diffuser (sewage)
Encyclopedia
An air diffuser or membrane diffuser is an aeration
device typically in the shape of a disc, tube or plate, which is used to transfer air and with that oxygen into sewage or industrial wastewater. Oxygen is required by microorganisms/bacteria residents in the water to break down the pollutants. Diffusers use either rubber membranes or ceramic elements typically and produce either fine or coarse bubbles.
Other diffused aeration devices include: jet aerators
, aspirator
s, and U tubes.
There are two main types of diffused aeration systems, retrievable and fixed grid, that are designed to serve different purposes. In the case of a plant with a single tank, a retrievable system is desirable, in order to avoid stopping operation of the plant when maintenance is required on the aeration system. Fixed systems, on the other hand, are typically less costly, and often more efficient because it is easier to make full use of the floor.
Automated software is available on the web to assist with drafting of aeration systems in CAD, as well as calculation software to help determine diffuser requirements for a given wastewater
.
s. This provides a buffer between the EPDM substrate and wastewater, hence reducing the likelihood of chemical attack and oxidation, and also providing better resistance to biological fouling and calcium scaling (manufacturers claim).
Aeration
Aeration is the process by which air is circulated through, mixed with or dissolved in a liquid or substance.-Aeration of liquids:-Methods:Aeration of liquids is achieved by:...
device typically in the shape of a disc, tube or plate, which is used to transfer air and with that oxygen into sewage or industrial wastewater. Oxygen is required by microorganisms/bacteria residents in the water to break down the pollutants. Diffusers use either rubber membranes or ceramic elements typically and produce either fine or coarse bubbles.
Types of Diffusers
Diffusers are generally referred to as either:- Fine Bubble/Fine PoreFine bubble diffusersFine bubble diffusers are a pollution control technology used to aerate wastewater for sewage treatment. They produce a plethora of very small air bubbles which rise slowly from the floor of a wastewater treatment plant or sewage treatment plant aeration tank and provide substantial and efficient...
- Coarse BubbleCoarse bubble diffusersCoarse bubble diffusers are a pollution control technology used to aerate and or mix wastewater for sewage treatment. They produce 1/4 to 1/2 inch bubbles which rise rapidly from the floor of a wastewater treatment plant or sewage treatment plant tank...
Other diffused aeration devices include: jet aerators
Jet aerators
A jet aerator is an aspirating device, which is used to aerate liquid such as water, sewage, sludge, manure, leachate, etc. The jet aerator works by the principle of venturi effect and the liquid is typically supplied by a centrifugal chopper pump...
, aspirator
Aspirator
An aspirator, also called an eductor-jet pump or filter pump, is a device that produces vacuum by means of the Venturi effect. In an aspirator, fluid flows through a tube which then narrows. When the tube narrows, the fluid's speed increases, and because of the Venturi effect, its pressure...
s, and U tubes.
Design Specifications
Typical efficiency of a full floor coverage diffused aeration system in clean water is 2%/ft submergence or 6.6%/m submergence. When converted to mass transfer into process or dirty water, it is typically closer to about half of those figures. Manufacturers of fine bubble systems have supported claims that the type, number and size of "pores" have a great effect on efficiency of a diffused aeration system.Types of diffused aeration systems
Diffusers are typically connected to a piping system which is supplied with pressurized air by a blower. This system is commonly referred to as a diffused aeration system or aeration gridThere are two main types of diffused aeration systems, retrievable and fixed grid, that are designed to serve different purposes. In the case of a plant with a single tank, a retrievable system is desirable, in order to avoid stopping operation of the plant when maintenance is required on the aeration system. Fixed systems, on the other hand, are typically less costly, and often more efficient because it is easier to make full use of the floor.
Automated software is available on the web to assist with drafting of aeration systems in CAD, as well as calculation software to help determine diffuser requirements for a given wastewater
Wastewater
Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...
.
Developments in Membrane Coatings
A developments in recent years has been surface coatings of PTFE on EPDM membraneArtificial membrane
An artificial membrane, or synthetic membrane, is a synthetically created membrane which is usually intended for separation purposes in laboratory or in industry. Synthetic membranes have been successfully used for small and large-scale industrial processes since the middle of twentieth century. A...
s. This provides a buffer between the EPDM substrate and wastewater, hence reducing the likelihood of chemical attack and oxidation, and also providing better resistance to biological fouling and calcium scaling (manufacturers claim).
External links
- [EDI Tech Bulletins http://www.wastewater.com]
- [SSI Aeration http://www.stamfordscientific.com]
- [Ecosafe diffused aeration http://www.diffusedaeration.com]