The Bio-​Sand Filter

The Bio-​Sand Fil­ter and ‘Ideas at Work’

Improv­ing water qual­ity for the rural com­mu­nity is a con­tin­u­ing pri­or­ity in Cam­bo­dia and has been recog­nised in its Mil­len­nium Devel­op­ment Goals (MDG’s). Part of these improve­ments has seen a focus on house­hold treat­ment meth­ods to improve bio­log­i­cally con­t­a­m­i­nated water. One of these is the Bio-​Sand Fil­ter (BSF). IaW are always keen to take the lead in intro­duc­ing and improv­ing tech­nolo­gies based on good prac­tice and user feed­back. IaW recog­nised oppor­tu­ni­ties because of man­u­fac­tur­ing and prac­ti­cal dis­ad­van­tages of the con­ven­tional square BSF units. We decided to intro­duce the first round units to Cam­bo­dia because of a num­ber of ben­e­fits they have. These are:

  • A sig­nif­i­cant reduc­tion in mould mate­ri­als – eas­ier to han­dle and trans­port to the pro­duc­tion site
  • Lower over­all mould unit cost
  • Ease of mov­ing the unit on the ground – the unit can be ‘rolled’ by one person,
  • As much as 20% less con­crete required than con­ven­tional square units – cost sav­ings all round – by cut­ting corners!!
  • A more aes­thet­i­cally pleas­ing design

Bio-​Sand Fil­ter mould components

The mould unit is an all steel con­struc­tion man­u­fac­tured to a high qual­ity and fin­ish. The main parts of the mould unit are shown in the exploded view below, these are:
1) the puller, 2) an inner mould, and 3) outer mould.

Bio Sand Filter

More info: info@​ideas-​at-​work.​org

The mould is sim­ply bolted together, turned upside down and fit­ted with a cop­per out­let pipe. A con­crete mix is then poured in the mould and com­pacted down. After sev­eral hours the puller is used to remove the inner mould after which the outer mould can be removed reveal­ing the fin­ished fil­ter shell. The fil­ter is then filled with sand and gravel layers.

The Bio-​Sand Fil­ter unit

Con­t­a­m­i­nated water is poured into the unit at the top. The water passes through the dif­fuser plate and the sand and gravel lay­ers. Head pres­sure pushes water through the cop­per pipe in the base to the out­let point. Bio­log­i­cal con­t­a­m­i­na­tion is reduced through the actions of adsorp­tion; mechan­i­cal fil­ter­ing, pre­da­tion (bio­log­i­cal layer’) and nat­ural die off. The typ­i­cal flow rate of the unit is around 60 litre/​hour.


Dimen­sions of the fin­ished fil­ter:
Outer diam­e­ter: 35cm
Inner diam­e­ter: 30cm
Height: 95cm
Weight: 60kg

Read more in pdf

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Ideas at Work

A Cam­bo­dian social enter­prise that:

  • Brings water and san­i­ta­tion prod­ucts to the Cam­bo­dian rural market;
  • Through an inno­v­a­tive dis­tri­b­u­tion channel;
  • With pro­mo­tion of financ­ing through micro loans;
  • IaW uses a busi­ness approach to full­fill its social goals.

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