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Recent research by Orenco Systems Incorporated has resulted in an advanced packed bed treatment technology that uses a textile medium. The textile medium has a complex fiber structure that offers an extremely large surface area for biomass attachment. The textile porosity is very high providing high hydraulic conductivity and excellent air movement through the medium.
Textile bed filters provides all the benefits inherent of recirculating sand filters but overcomes some limitations such as (1) land area, (2) media quality or accessibility and (3) installation quality.
1. Land area – Some sites lack the land area required for a sand filter. Sand filters for single-family residences typically require between 100 and 400 square feet. The land area needed for a textile bed filter is much smaller, typically 20 to 40 square feet, because the loading rates are 5 to 20 times higher.
2. Media quality or accessibility – Good quality sand media is occasionally not locally available. In addition, getting sand to some sites such as mountainous regions or isolated areas can be difficult. The manufactured textile medium ensures consistent quality and availability.
3. Installation – The lightweight textile medium and small filter size make pre-manufactured treatment units practical, eliminating onsite construction and reducing installation time, labor and construction errors.
The textile bed filter treats wastewater with the same processes as the recirculating sand filter. The two basic components of the textile bed filter are a process tank/recirculating tank and textile filter unit.
Process Tand &Textile Bed Filter (OSI Advantex System)
The wastewater percolates both through and between the textile media. A visible biological film attaches onto the filter medium. Due to the high porosity within the filter aerobic conditions exist that are ideal for microbes that break down the organics in the liquid and convert ammonia to nitrate. Other conditions exist that result in further nitrogen reduction within the media. Eighty percent of the filtrate recirculates back to the high-carbon, low-oxygen (anoxic) environment of the process tank that is ideal for microbes that reduce nitrates to nitrogen gas (denitrification). Harmless nitrogen gas is then released freely back into the atmosphere.
The process tank is sized based on daily flows. It also contains a pump and timer. Typically, the pump will dose the textile filter(s) for one minute every 20 minutes. A splitter ball valve will divert a minimum of 80% of the flow back into the process tank. The remaining effluent will be diverted to a disposal system, such as pump chamber and leach trenches or a variety of other disposal methods.
The textile filters come in prepackaged modules that can be placed on top of the process tank. The top of the filter modules must be at-grade to allow air into the system.
Inspect the processing tank for liquid depth, color of scum and effluent, and sludge and scum thickness. (After the first year’s measurement of septic tank sludge and scum thickness, measurements only need to be taken about every three years.). Measurements of solids accumulation help to determine when the tank needs pumping. A recommendation for pumping should be made when there is an accumulation of scum extending to a depth of about three inches above the top of the outlet ports of the pumping system or an accumulation of sludge to a depth within six inches below the bottom of the outlet ports.
The pumping system should be inspected annually to ensure that all pumps are operating properly. The inspection should include:
1. Verify that there are no obvious holes or leaks in the pump tank riser.
2. Verify that the float cords are neatly wrapped inside the riser so they cannot interfere with the operation of the floats.
3. Verify the high water alarm works by lifting the top float up.
4. Verify the programmable timer settings are correct.
5. Read and record the elapsed timer meter and or cycle counter if the control panel is equipped with these devices.
6. Inspect recirculating splitter device.
If a strong or offensive odor is emitted form the filter, measure the DO levels in the filtrate and recirculation chamber and adjust the recirculation time if necessary. The following textile filter items should be checked annually:
1. Check the organic build-up on the media under the orifices.
2. Clean and flush the manifold.
3. Check residual pressure against start-up value. If the pressure is more than 20% higher than the start-up value, perform additional cleaning and verify that all orifices are clear.
4. Inspect for ponding. The filter should not be saturated. Effluent should move freely through the media. If there is a build-up of oil and grease that is causing the ponding, scrape a sample from the biomat and have it analyzed by a lab.
Some Advantages and Disadvantages are listed below.
Advantages:
· Textile filter beds produce a high quality effluent.
· Leach fields can be small and shallow.
· Low energy requirements.
· The treatment capacity can be expanded through modular design.
· Stable and work well for intermittent usage.
· Need smaller land area than most systems.
· Ease in construction
· Nitrogen reduction is often times possible depending on system setup.
Disadvantages:
· Systems are relatively new and long-term capabilities are unknown.
· Media may need replacing after several years of use.