FAQs for High-Efficiency Sand Filters

High-efficiency microsand filters achieve submicron filtration performance

What are the applications of Vortisand filters?

Vortisand filters can be used anywhere media filtration is considered. Due to its outstanding ability to remove submicron particles, Vortisand filters are especially prized as a pretreatment step for reverse osmosis (seawater desalination or ultrapure water production), as a side-stream filter (cooling towers, chilled and hot water loops) or as a polishing filter (after secondary clarifiers or in produced water treatment). Vortisand filters are robust and versatile, making them suitable for a wide range of applications.

Where do you have installations?

There are more than 2,500 installations around the world (principally in North America, Europe and the Middle East). Our clients are found in all markets: hospitals, universities, data centers, food & beverage, oil & gas, automotive, chemical, etc. The first generation of Vortisand filters was predominantly used in cooling and heating applications. In 2011, an intensive R&D program led to the development of the H2F® series of systems, offering improved performance and greater filtration capacities.

When was the Vortisand system developed?

The original Vortisand filtration system was invented in Massachusetts in 1962 by Engineer Gilford Sharrow.

Why was the Vortisand system developed?

The Vortisand system was originally developed for the HVAC market. Conventional filters were inefficient at removing the very fine particles found in cooling tower and chiller loops. Airborne particles (dust and pollen), chemical precipitates and corrosion debris range in size from tens of microns to less than one micron. Centrifugal separators can only remove large and dense particles (typical cut-off greater than 40 microns). Conventional filters are unable to efficiently remove particles under 20 microns without chemical conditioning. Yet it is well documented that heat exchanger fouling is caused by much smaller particles. The Vortisand system was designed to remove such particles without the use of chemicals.

What is the removal efficiency of the Vortisand system?

Vortisand filtration systems provide submicron removal performance! The removal efficiency varies depending on the size and type of particles. Typically, the removal efficiency is high for large particles regardless of their nature (organic or inorganic). With smaller particles, the removal efficiency tends to diminish. For very small particles (a few microns and under), the nature of the particles strongly influences the removal efficiency, as surface charges become more important. Historically, removal efficiencies greater than 99% for particles of 5 microns and up have been documented, but for submicronic particles, the efficiency can vary.

What is the maximum operation temperature and pressure?

Materials and method of construction determine the maximum allowable temperature of the filters. Typically, PVC is limited to 105 °F while carbon and stainless steel are limited to 180 °F. The maximum allowable pressure is dependent on the temperature. Typically, Vortisand filters are designed for pressures ranging from 50 psi to 150 psi (3 to 9 bar).

Does the Vortisand system require pretreatment?

Pre-screening of the raw water may be necessary if it contains particles with size and density that prevent their evacuation during the backwash phase.

Does the Vortisand system require chemical conditioning?

Chemical conditioning of the raw water is typically not required with Vortisand, unless the conversion of dissolved solids to filterable solids is required to meet the treatment objectives (for example, oxidation of dissolved iron).

What type of filtration media is used?

The microsand filtration media is a fine sand with specific characteristics that help improve efficiency and water quality. Other filtration medias are available for special applications. Vortisand media is commercialized under the name Strata HDX™ and can only be purchased from Evoqua Water Technologies. Media replacement must be done under the supervision of Evoqua personnel.

How are Vortisand filters operated?

Vortisand filter operation is fully automated. Each system is equipped with a programmable logic controller (PLC), a touch-screen operator interface and two pressure transmitters (inlet and outlet). Backwash cycles are normally initiated on a high differential pressure. Alternatively, backwash cycles can be initiated based on a filtered water quality parameter (for example, high turbidity) or a time delay. Backwash cycles can also be initiated manually by the operator.

Is air used during the backwash phase?

In many applications, an air scouring phase precedes the backwash phase. Simultaneous air and water backwashing is not used. The duration of the air scouring phase is set by the operator (typically from 1 to 2 minutes). The purpose of the air scouring phase is to provide a high-energy scrubbing action that removes biofilm or other sticky material from the media.

What is the frequency and duration of the backwash phase?

The frequency of backwash depends on the raw water quality (concentration, size and nature of particles). The duration of the phase is set by the operator (typically from 5 to 12 minutes).