By:
Ilan Kesler –BallTech CEO
Tzachi Tzvi –Water quality engineer southern district of Mekorot.BallTech
Defining the need
Backwash is one of the main challenges of deep-media filtering.
Standard backwash systems are complicated multiple-step systems for washing the filter media: backwash with water, combination of air and water backwash, and direct washing. Common operation methods of standard sand filter systems require installation of rotating equipment such as an air compressor, nozzles, valves, and complex manifolds.
Added to the complex equipment needed to perform the backwashes are operational water-losses. Filtering facilities in the Arava, for instance, lose 2-4% of the filtrate to backwashes.
Introducing the technology
BallTechs innovative backwash method may simplify the backwash system, reduce water losses, and reduce the costs of constructing filtering plants.
The unique BallTech technology performs the backwash procedure in a different order:
• batch pumping of the media from the bottom of the filter and washing it with raw water
• running media and filtered particulates to the top part of the filter
• Separating of the media from the filter particulates at the top of the filter; media settles and the filtered particulate is washed with backwash water.
Testing the technology at Mekorot
WaTech® together with the water quality unit and the southern district of Mekorot initiated an experiment to test the technology.
The site they chose is the Zofar standard filtration plant in the Arava valley which has a total flow rate of 490 cubic meter/hour. Raw water at this site contains iron and sulfur residual which must be removed from the water before it can be supplied to irrigate crops. The standard filters are backwashed once every 48 hours or when a pressure drop of 6m is reached. Backwash stages are: water emptying, air scour, back wash, direct wash. Loss from a single backwash in this plant is an estimated 120 cubic meters and total losses amount to 4% annually.
Based on earlier tests conducted by BallTech, water losses using the new system are significantly lower than the amount of backwash water lost in a standard -media filter. The projects current goal is to test performance over time.
It is also necessary to test the technology for robustness and for various malfunctions. The total availability of the BallTech filter will be determined and compared to availability of standard filters.
Filtered water quality will also be examined, keeping in mind that the BallTech has developed a novel backwashing system not a new filtration method.
The test will be conducted by the southern district team, under the professional guidance of Mr. ZahiZvi who is the regional water-quality engineer, Ms. Eti Mansherov head of water quality department at Mekorots Headquarter. WaTech® division will supply the framework that is needed for the test to succeed.
Potential benefit
The BallTech unique backwashing method does not use air scour or water backwash. This means that, if the system indeed proves to be effective over time, water and water/air backwashes can be dispensed with (no need for compressor, nozzles, valves, and complex piping), and establishing a filtering plant will become more economical.
The Balletch backwashing method also cuts down backwashing time, producing increased availability of
the filters.
Based on earlier tests conducted by BallTech water losses using this method are significantly lower than the amount of wash water lost in a standard deep-media filter. If the system proves to be effective over time it will be possible to reduce water losses.
Additional applications
Filtration has a much broader application than this specific implementation in the Arava. If this technology proves to have a significant advantage over standard filtration further applications can be tested, such as:
1. Filtration of surface water
2. Filtration of treated waste water (effluent)
3. Pre-treatment of groundwater, sea-water, and treated waste water ( reclaimed water) prior to desalination
