Environmental Science & Engineering - www.esemag.com - May 2005
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Jet mixers solve sludge storage tank settling problem
Three sludge storage tanks at Camp Creek, Georgia,
wastewater treatment plant were fitted with jet mixers
for mixing and aeration of the three sludge storage
tanks. The 70 ft. diameter aerobic digesters are
designed to digest primary and secondary sludge. The tanks
have a 26 ft. average side water depth with a 10 ft. deep cone
in the centre. Liquid level varies from 6 ft. to 26 ft. and the design sludge concentration is 4%.
During construction, the jet mixers were installed and
the tanks were filled with sludge. The tanks were put into
operation after the sludge had settled for 3 months. The jet
mixers were flushed with water and the system started up
with no plugging or solid settling issues.
Mixing Systems, Inc. solved the settling issues by
installing a single jet mixer/aerator near the bottom cone
section of the tank. This directs the mixing plumes along
the tank floor where the solids settled. One screw pump
provides the mixing energy for the jet mixer/aerator. One
positive displacement blower provides the air for oxidation
of the volatile solids in the digester. The pump is run on a
continual basis to provide mixing in the digester. One 125
HP air blower can deliver air flow to each tank. The plant
has a bank of four air blowers, which includes one stand-by
blower.
As a result of efficient mixing, there are no odours such
as hydrogen sulfide and methane. The new system also has
no in-basin moving parts and easily handles fluctuating liquid
conditions. According to Mixing Systems, Inc. the jet
mixers are designed to pass greater than 2-inch spherical
solids.
For additional information, contact e-mail: mixing@mixing.com or visit www.mixing.com.
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