Back­wash­ing – crit­i­cal to wa­ter treat­ment plant per­for­mance

DEMM Engineering & Manufacturing - - PRODUCT WATCH -

In wa­ter treat­ment plants, the qual­ity of wa­ter out­put is de­ter­mined by how well the fil­tra­tion sys­tem is op­er­at­ing. A key in­gre­di­ent in keep­ing the fil­tra­tion sys­tem work­ing at its best is the fre­quency and qual­ity of back­wash­ing pro­cesses.

Over time, the me­dia in a wa­ter treat­ment fa­cil­ity be­comes coated and even clogged by par­ti­cles and de­bris. Reg­u­lar fil­ter clean­ing is cru­cial to en­sure the sys­tem re­mains ef­fi­cient and the qual­ity of the wa­ter out­put, sound.

“The ef­fec­tive­ness of the fil­tra­tion sys­tem is the linch­pin of ev­ery wa­ter treat­ment pro­gram,” says Graeme Cooper, man­ag­ing di­rec­tor of Tecpro Aus­tralia. “To keep it run­ning at op­ti­mum per­for­mance, it is vi­tal to reg­u­larly clean the fil­ter, and this is done by back­wash­ing.”

Back­wash­ing in­volves shut­ting down fil­tra­tion and re­vers­ing the f low of wa­ter to run back­wards through the fil­ter at a higher ve­loc­ity, which dis­lodges par­ti­cle build up. Air­flow is some­times used to am­plify the clean­ing process, ei­ther be­fore or dur­ing back­wash­ing with wa­ter.

“Typ­i­cally there are three dif­fer­ent ap­proaches to back­wash­ing,” says Cooper. “Some sys­tems use wa­ter only, while oth­ers use air and wa­ter con­sec­u­tively, or air and wa­ter si­mul­ta­ne­ously.”

The op­ti­mal ap­proach de­pends on the type and rate of par­ti­cle build up in the fil­ter.

“It’s fair to say that the com­bi­na­tion of air and wa­ter si­mul­ta­ne­ously gives the strong­est scour rate, and there­fore a more rig­or­ous clean,” says Cooper.

“Dur­ing air back­wash­ing, holes in the stem al­low air to be pumped into the noz­zles from where it f lows up through the me­dia help­ing to dis­lodge ma­te­rial that has built up. The fol­low­ing wa­ter back­wash raises the fil­ter me­dia and f lushes away all the un­wanted ma­te­rial.”

In­stalling noz­zles with the cor­rect size air holes (and/or slots) in the stem for air scour­ing is crit­i­cal to achiev­ing the right amount of air­flow and back pres­sure. The lo­ca­tion, di­men­sions and num­ber of air holes and slots is an­other im­por­tant fac­tor in the de­sign of the fil­ter noz­zle. For the noz­zle to work ef­fec­tively it is es­sen­tial that the air holes and slots are specif­i­cally de­signed to suit the ca­pac­ity of the back­wash air sup­ply.

“Noz­zles that have a short stem with­out back­wash holes/slots are not suit­able for air scour­ing as they will use too much air and so they are not able to guar­an­tee the equal air dis­tri­bu­tion in the to­tal num­ber of noz­zles in­stalled in the fil­ter drain f loor. They are only for use with wa­ter back­wash­ing,” says Cooper.

He adds that de­sign­ing, con­struct­ing and in­stalling the cor­rect noz­zles to suit sys­tem de­mands is fun­da­men­tal to the ef­fec­tive­ness of wa­ter treat­ment plants.

“We help man­agers who are re­spon­si­ble for wa­ter plant main­te­nance to get max­i­mum per­for­mance and life from their fil­ters by se­lect­ing the right fil­tra­tion and back­wash­ing noz­zle to match their needs,” says Cooper. “The ILMAP range of sand fil­ter noz­zles is par­tic­u­larly use­ful for sys­tem up­grades be­cause it is avail­able in 22 dif­fer­ent mod­els, eight stan­dard stem lengths, eight types of thread and 10 dif­fer­ent slot widths.

“This means there is a choice avail­able to match the pre­cise di­men­sions of sys­tems of any age. ILMAP will also man­u­fac­ture noz­zles to in­di­vid­ual client spec­i­fi­ca­tion.”

Tecpro Aus­tralia is the exclusive Aus­tralasian dis­trib­u­tor of the ILMAP range of sand fil­ter noz­zles and ac­ces­sories, which are de­signed and man­u­fac­tured in Italy.

“There are dif­fer­ing opin­ions re­gard­ing noz­zle slot width but Tecpro Aus­tralia be­lieves that it is prefer­able to have slot widths which are smaller than the small­est me­dia par­ti­cles that will come in con­tact with the noz­zle,” says Cooper. “The slot widths in ILMAP’s sand fil­ter noz­zles are pre­ci­sion moulded so they are ex­tremely ac­cu­rate and re­li­able. ILMAP sand fil­ter noz­zles are also strong, durable and are avail­able in a range of ma­te­ri­als mak­ing them tem­per­a­ture and chemical re­sis­tant to suit any en­vi­ron­ment.”

demm.co.nz/reader-en­quiry #D131206

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