Effective removal of low-density solids
Xylem’s Leopold Clari-DAF system is a
clarification technology for the pretreatment of rapid gravity and membrane
filter feed water. It’s a highly-effective, proven technology for removing
low-density particulates found in lakes and reservoirs, which are problematic
for typical sedimentation systems. The Clari-DAF system excels at removing
filter clogging algae and precipitated solids (TOC, Fe, Mn), as well as Giardia
and Cryptosporidium. It is also an unsurpassed system for treating open
seawater intakes with contaminants such as algae (red tide) and free or
emulsified oil that are naturally buoyant and best removed by flotation.
The process is designed on the concept that
it’s easier to float low-density solids than to settle them. Normally, solids
that are hundreds of microns in size are required to settle, while particles
that are only tens of microns in size can be easily floated. Its performance is
superior to conventional clarification in providing consistent water quality,
producing consistently high sludge solids, and operating at high loading rates –
results that can lower your total cost of operation.
The Clari-DAF system begins by dissolving air
under pressure into water according to Henry’s Law of Dissolution. Releasing
the pressure via a special device creates millions of micro-bubbles
approximately 30 to 100 microns in diameter. The micro-bubbles attach to floc
in the water and float it to the surface for removal. The resulting floated
sludge is then removed from the surface of the water by hydraulic means, and
clarified water is removed from the bottom of the basin by laterals.
Lowering overall cost of plant operation
Xylem’s Leopold Clari-DAF system can
dramatically improve the quality of the water produced at a lower
cost. The result of improved effluent water quality includes longer filter
runs, less backwash water, less media breakdown, and less filter-to-waste.
Longer filter run lengths means less power costs because of less frequent
filter backwashing; reducing in-plant water use and filter-to-waste means less
treated water is discarded – a savings in lost expense.
The Clari-DAF system also equates to chemical
cost savings. When compared to a conventional clarification plant, Clari-DAF
consumes less coagulants and polymers – eliminating the increased chemicals
required and mixing necessary to achieve larger, heavier floc that will
settle.Water treatment plants utilizing the Clari-DAF system will also realize
a considerable improvement in solids handling as well. The average number of
man hours spent handling the sludge output will decrease thanks to improved
cake solids. Cost savings can be achieved thanks to both lower sludge disposal
costs and lower labor costs.
The Leopold Clari-DAF system can also
accommodate much higher loading rates, enabling a compact design with
flow-through rates increased by as much as ten times that of conventional
clarification tanks. The compact design results in improved land use,
especially in existing plants with no room for expansion, and installation in
concrete tanks contributes to keeping capital costs low, as well as minimizing
corrosion. The small system size also allows for retrofitting many different
types of clarifiers with the Clari-DAF system, saving considerable civil
construction cost and time.