WaterFilters
What is water filters and for what its used? Interesting fact from the History of Water Filters Types of Filters Slow Sand Filter Rapid Sand Filter

Water Filtration Information

Is it possible to do without system of water treating? How correctly to select test of water and to make the chemical analysis? I wish to establish a water treating system. With what should I begin? What should be productivity of the system? In what building is the water-purifying equipment placed and how much space does it take? How much does installation take? What guarantee period on the equipment for water treating? How often should I replace filters and reagents in systems of water treating?

Types of Filters


Filters can be categorized in a variety of ways. The table below shows the characteristics of four types of filters which can be used in water treatment.

Slow Sand Filter

Rapid Sand Filter

Pressure Filter

Diatomaceous earth filter
(Diatomite filter)

Filtration rate
(GPM/ft2)

0.015-0.15

2-3

2-3

1-2

Pros

Reliable. Minimum operation and maintenance requirements. Usually does not require chemical pretreatment.

Relatively small and compact.

Lower installation and operation costs in small filtration plants.

Small size. Efficiency. Ease of operation. Relatively low cost. Produces high clarity water. Usually does not require chemical pretreatment.

Cons

Large land area required. Need to manually clean filters.

Requires chemical pretreatment. Doesn’t remove pathogens as well as slow sand filters.

Less reliable than gravity filters. Filter bed cannot be observed during operation.

Sludge disposal problems. High head loss. Potential decreased reliability. High maintenance and repair costs.

Filter Media

Sand.

Sand. Or sand and anthracite coal. Or sand and anthracite coal and garnet.

Sand. Or sand and anthracite coal. Or sand and anthracite coal and garnet.

Diatomaceous earth.

Gravity or Pressure?

Gravity.

Gravity.

Pressure.

Pressure, gravity, or vacuum.

Filtration Mechanism

Biological action, straining, and adsorption.

Primarily adsorption. Also some straining.

Primarily adsorption. Also some straining.

Primarily straining.

Cleaning Method

Manually removing the top 2 inches of sand.

Backwashing.

Backwashing.

Backwashing.

Common Applications

Small groundwater systems.

Most commonly used type of filter for surface water treatment.

Iron and manganese removal in small groundwater systems.

Beverage and food industries and swimming pools. Smaller systems.

Among the great variety of filters, the most popular in usage still slow sand filters and rapid sand filters.