Cost Saving Conversion to Air-Whip Pumps ® Dissolved Air Flotation
All DAF (Dissolved Air Flotation) installations have basic requirements. In order to achieve maximum dissolved air in the water, the following must be available:
• Significant air to water surface area interface (achieved within the pump)
• Pressure, provided by the pump (preferably 75 to 115 psi., depending on installation and design)
• Time. Dissolving air is not instantaneous. It requires time under pressure and interface. This is the purpose of the saturation tank/pressure header.
For very large DAF installations having very high flows, the Air-Whip pump is capable of delivering flows to match the “white water” requirement up to about 400 GPM. It must be understood that as the flow increases, the residence time in the pump decreases, placing more dependence on the saturation vessel part of the system. In some cases, the client has simply injected directly into the influent line of the DAF with no problem generating “white water”. This can work if the flow through the Air-Whip pump is relatively low. For higher flows, a tank or larger diameter section of pipe of sufficient length must be provided to introduce sufficient residence time under pressure for the sheared air to be dissolved into the water. In many of the modern DAFs, this saturation tank is the pressure header from which “white water” is delivered to multiple points. All properly designed DAFs have some type of saturation vessel for this purpose. Some are capped large diameter pipe sections and some are tanks, but they serve the same specific purpose. An installation without this device can never perform to full capability.
Contact KeysTec, LLC to review the details of your installation to determine suitability for conversion to the Air-Whip. In many cases, the “Full Flow” or “Split Flow” configuration can give you a significant increase in the capacity of your DAF.
Note: DAFs are sometimes used in conjunction with sand filters. This is yet an emerging concept that has known issues. Typically, sand filters are used for certain metallic compounds:
Vietnam and Bangladesh are both confronted with high arsenic concentrations, but distinct water compositions require different solutions. Arsenic mitigation depends for the most part on natural factors, such as the availability of alternative water sources and the feasibility of water treatment. If several options are available, socioeconomic factors determine which mitigation option is implemented most successfully.
The socially accepted and already widespread sand filters in the Red River delta have advantages for their simplicity and low cost of operation. The removal of iron from the pumped water is immediately apparent even to people who are not aware of the arsenic problem. Thus, sand filters are a good option in Vietnam and in other affected regions with high concentrations of dissolved iron.
Use of sand filters must be carefully evaluated and specifications must be strictly followed.