Sand Filtering

There are many types of water sand filtration, such as Slow Sand Filtering, Rapid Sand Filtering and Deep sand bed. These sand filters are used in everyday life, in aquariums, water industries, and more.

• Sand Filter

  
  A sand filter is a filter that has sand in it, that collects unwanted particles in the water. To clean the sand in the sand filter, a process called backwash is executed. This is the act of running the sand filter backwards.

A diagram showing the backwashing procedure of a sand filter.

• Deep Sand Bed Filtration

  
  ‘Deep sand bed’ is a filtration method used in some saltwater aquariums. A deep sand bed, similar to the Berlin Method, is designed to cultivate anaerobic bacteria in the

  

  Malta National Aquarium

  bottom layers of sand, converting the nitrate to nitrogen gas to remove toxic nitrates. In freshwaters, nitrate can reach high levels that can potentially cause the death of fish.
   
  
  
  
  

• Slow Sand Filter

  
  
  Slow sand filters are used in water purification for treating raw water to produce a potable product. They are used primarily to treat surface water, and can also be found in large aquariums. Slow sand filters work through the formation of a gelatinous layer, or biofilm, called the hypogeal layer (also called Schmutzdecke) in the top few millimetres of the fine sand layer. The hypogeal layer is formed in the first 10–20 days of operation and contains

  

  Slow Sand Filter

  bacteria, fungi, protozoa, rotifera and other aquatic insect larvae. The surface biofilm is the layer that provides the most effective purification in water treatment, with the sand under its layer providing the support medium for this biological treatment layer. As water passes through the hypogeal layer, particles of foreign matter are trapped in the mucilaginous and soluble organic material is adsorbed. The water quality of a slow sand filter is of excellent quality with 90-99% bacterial reduction.
  

• Rapid Sand Filter

  
  The rapid sand filter or rapid gravity filter is another type of filter used in water purification and is commonly used in municipal drinking water facilities as part of a multiple-stage treatment system. This type of filter uses coarse sand and other granular material to remove

  

  Rapid Sand Filter

  particles and impurities that have been trapped in a floc (a loosely clumped mass of fine particles) through the use of flocculation chemicals—typically alum (Al₂(SO₄)₃.14H₂O). The unfiltered water flows through the filter under the force of gravity or under pumped pressure and the floc 
  
  material is trapped in the sand.
  
  
  
  
  Made By Kyle Farrugia
  KSGenre © 2016