Sand filter


Sand filter

Sand filters are used for water purification. There are three main types;
# rapid (gravity) sand filters
# upflow sand filters
# slow sand filters

All three methods are used extensively in the water industry throughout the world. The first two require the use of flocculant chemicals to work effectively whilst slow sand filters can produce very high quality water free from pathogens, taste and odour without the need for chemical aids.

Passing flocculated water through a rapid gravity sand filter strains out the floc and the particles trapped within it reducing numbers of bacteria and removing most of the solids. The medium of the filter is sand of varying grades. Where taste and odour may be a problem (organoleptic impacts), the sand filter may include a layer of activated carbon to remove such taste and odour.

Sand filters become clogged with floc after a period in use and they are then backwashed or pressure washed to remove the floc. This backwash water is run into settling tanks so that the floc can settle out and it is then disposed of as waste material. The supernatant water is then run back into the treatment process or disposed off as a waste-water stream. In some countries the sludge may be used as a soil conditioner. Inadequate filter maintenance has been the cause of occasional drinking water contamination.

Sand filters are occasionally used in the treatment of sewage as a final polishing stage (see Sewage treatment). In these filters the sand traps residual suspended material and bacteria and provides a physical matrix for bacterial decomposition of nitrogenous material, including ammonia and nitrates, into nitrogen gas.

ee also

* Water purification
* Water treatment
* American Water Works Association


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • sand filter — …   Useful english dictionary

  • Slow sand filter — Slow sand filters are used in water purification for treating raw water to produce a potable product. They are typically 1 to 2 metres deep, can be rectangular or cylindrical in cross section and are used primarily to treat surface water. The… …   Wikipedia

  • Rapid sand filter — The rapid sand filter or rapid gravity filter is a type of filter used in water purification and is commonly used in municipal water treatment facilities. Rapid sand filters use relatively coarse sand and other granular media to remove particles… …   Wikipedia

  • slow sand filter — A bed of sand through which water slowly flows; the gelatinous microbial layer on the sand grain surface removes waterborne microorganisms, particularly Giardia, by adhesion to the gel. This type of filter is used in some water purification… …   Dictionary of microbiology

  • Filter (chemistry) — In domestic food and drink preparation where bulk solids are removed from liquids, this is often called a strainer. Filtrate is the liquid produced after filtering a suspension of a solid in a liquid.Filtrand (or Residue) is the solid residue… …   Wikipedia

  • filter — I n. 1) to pass smt. through a filter 2) a cloth; sand filter II v. 1) (d; intr.) to filter into (foreign influence began to filter into the country) 2) (d; tr.) to filter through * * * [ fɪltə] sand filter a cloth to pass smt. through a filter …   Combinatory dictionary

  • Filter [1] — Filter. Strömt eine Flüssigkeit so durch einen porösen Körper, daß die in ersterer enthaltenen Suspensionen dem letzteren durch Adhäsion verbleiben[26] oder sich vor demselben festlegen, so nennt man den Vorgang Filtration, den Körper das Filter… …   Lexikon der gesamten Technik

  • Filter — Fil ter, n. [F. filtre, the same word as feutre felt, LL. filtrum, feltrum, felt, fulled wool, this being used for straining liquors. See {Feuter}.] Any porous substance, as cloth, paper, sand, or charcoal, through which water or other liquid may …   The Collaborative International Dictionary of English

  • Filter bed — Filter Fil ter, n. [F. filtre, the same word as feutre felt, LL. filtrum, feltrum, felt, fulled wool, this being used for straining liquors. See {Feuter}.] Any porous substance, as cloth, paper, sand, or charcoal, through which water or other… …   The Collaborative International Dictionary of English

  • Filter gallery — Filter Fil ter, n. [F. filtre, the same word as feutre felt, LL. filtrum, feltrum, felt, fulled wool, this being used for straining liquors. See {Feuter}.] Any porous substance, as cloth, paper, sand, or charcoal, through which water or other… …   The Collaborative International Dictionary of English


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.