Revision 8/4/05
2
UThe Amphidrome® Process
The Amphidrome® system is a submerged attached growth bioreactor process, designed
around a deep-bed sand filter. It is specifically designed for the simultaneous removal of
soluble organic matter, nitrogen and suspended solids within a single reactor. Since it
removes nitrogen, it may also be considered a biological nutrient removal (BNR) process.
To achieve simultaneous oxidation of soluble material, nitrification, and denitrification in
a single reactor, the process must provide aerobic and anoxic environments for the two
different populations of microorganisms. The Amphidrome® system utilizes two tanks
and one submerged attached growth bioreactor, called the Amphidrome® reactor. The
first tank, the anoxic/equalization tank, is where the raw wastewater enters the system.
The tank has an equalization section, a settling zone, and a sludge storage section. It
serves as a primary clarifier before the Amphidrome® reactor.
This Amphidrome® reactor consists of the following three items: underdrain, support
gravel, filter media. The underdrain, constructed of stainless steel, is located at the
bottom of the reactor. It provides support for the media and even distribution of air and
water into the reactor. The underdrain has a manifold and laterals to distribute the air
evenly over the entire filter bottom. The design allows for both the air and water to be
delivered simultaneously--or separately--via individual pathways to the bottom of the
reactor. As the air flows up through the media, the bubbles are sheared by the sand,
producing finer bubbles as they rise through the filter. On top of the underdrain is 18”
(five layers) of four different sizes of gravel. Above the gravel is a deep bed of coarse,
round silica sand media. The media functions as filter, significantly reducing suspended
solids and provides the surface area for which an attached growth biomass can be
maintained.
To achieve the two different environments required for the simultaneous removal of
soluble organics and nitrogen, aeration of the reactor is intermittent rather than
continuous. Depending on the strength and the volume of the wastewater, a typical
aeration scheme may be three to five minutes of air and ten to fifteen minutes without air.
Concurrently, return cycles are scheduled every hour, regardless of the aeration sequence.
During a return, water from the clear well is pumped back through the filter and
overflows into the energy-dissipating TEE. A check valve in the influent line prevents
the flow from returning to the anoxic/equalization tank via that route. The energy-
dissipating TEE is set at a fixed height above both the media and the influent line, and the
flow is by gravity back to the front of the anoxic/equalization tank.
The cyclical forward and reverse flow of the waste stream and the intermittent aeration of
the filter achieve the required hydraulic retention time and create the necessary aerobic
and anoxic conditions to achieve the required level of treatment.
(16 pages)
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