Clari-DAF dissolved air flotation system
- Removes primary contaminants such as algae, precipitated organics, iron, and manganese
- Ideal for open seawater source water containing contaminants such as membrane-fouling algae (red tide) and free or emulsified oil
- No polymer required, excellent clarifier prior to membrane filtration
- High loading rate – up to 16 gpm/ft2 (40 m/hr), 10 times that of conventional sedimentation systems
- Compact design – up to 1/10th the footprint of conventional clarification
- Water produced from system typically well below 1 ntu prior to filtration, yielding filter run times of 3-4 time that of previous sedimentation systems
- Can be installed in concrete tanks or provided as steel package plants
- Rapid start-up
- Other applications include open intake seawater pretreatment, filter backwash recovery, and treatment of tertiary WW lagoon effluent
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.