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À̸§ °ü¸®ÀÚ waterindustry@hanmail.net ÀÛ¼ºÀÏ 2012.11.08 Á¶È¸¼ö 2309
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¿©°ú¡¤ºÐ¸® ±â¼úÀÇ Ã¹ ¹ø°·Î´Â Á߷¿¡ ÀÇÇÑ Ä§Àü(sedimentation) ±â¼ú·Î¼­ (¿ø½É·Â¿¡ ÀÇÇÑ Ä§ÀüÀåÄ¡, °í¼ÓÀÇ µð½ºÅ©ÇüÅ ºÐ¸®ÀåÄ¡ ¹× µ¥Ä­ÅÍ(decanter) ÀåÄ¡´Â º°µµ·Î °ËÅä) À̹ø °ËÅä´Â ÁÖ·Î ½ºÅ©¸° ȤÀº ü°É¸²(sieve)¿¡ ÀÇÇÑ ºÐ¸®¿ë ÀåÄ¡(´ëºÎºÐ Áß·ÂÀÛ¿ë¿¡ ÀÇÇÑ ±¸µ¿) ¹× ¿©°úž(deep bed) ±¸Á¶ÀÇ ÇÊÅÍ¿¡ ÀÇÇÑ ºÐ¸®¿ë ÀåÄ¡(¿ª½Ã ±¸µ¿·ÂÀº ÁÖ·Î Áß·ÂÀÛ¿ë¿¡ ÀÇÁ¸)¿¡ °üÇÑ °ÍÀÌ´Ù. ÀÌ·¯ÇÑ ºÎ·ù¿¡ ¼ÓÇÏ´Â ÀåÄ¡µéÀº ¡âgravity clarifiers and thickeners ¡âlamella separators ¡âclassifiers and elutriators ¡âflotation cells ¡âscreens(both stationary and moving) ¡âdeep bed granular(sand) filters µîÀ¸·Î ºÐ·ùµÈ´Ù.

ÀÌ¿Ü¿¡ À¯»çÇÑ ¸ñÀûÀ¸·Î Á¤¼ö ¹× Æó¼ö¸¦ ó¸®Çϴµ¥ »ç¿ëµÇ´Â °ÍÀ¸·Î »ý¹°¹ÝÀÀ±â(surface biological reactors) ¹× trickle filters µîÀÌ ÀÖ´Ù. ÀÌÁ¦ À§¿¡ ¾ð±ÞµÈ ÀåÄ¡µé¿¡ ´ëÇÑ °³¹ß ÇöȲ¹× ´ëü¿ëÀ¸·Î »ç¿ëµÇ´Â »õ·Î¿î °³¹ß ÀåÄ¡µéÀ» ¼Ò°³ÇÏ°íÀÚ ÇÑ´Ù.
 
In this, the first of what is intended to be a set of articles reviewing recent developments of the technologies of filtration and its closely related separative processes, the main topic is sedimentation under the force of gravity(centrifugal sedimentation, the province of the high speed disc separator and the decanter, will be covered in a later article).

This is coupled with separation by a screen or sieve, which is largely gravity driven, and separation in a deep bed(or sand) filter, where, again, the driving force is often that of gravity. The full range of equipment types to be covered therefore is as follows, although not all will have noteworthy developments:
 
. gravity clarifiers and thickeners,
. lamellar separators,
. classifiers and elutriators,
. flotation cells,
. screens, both stationary and moving, and
. deep bed granular(sand) filters,
 
with which are also included the surface biological reactors, or trickle filters, used for treating water and wastewaters with similar purpose to other items in this list. The article will look at developments in the listed equipment types, but also at novel items that aim to replace them.
 
 
¡ã È£ÁÖÀÇ Outotec»ç°¡ °³¹ßÇÑ thickener ÀåÄ¡ ¿ëµµ·Î »ç¿ëµÇ´Â Â÷¼¼´ë¿ë Feedwell ½Ã½ºÅÛ.

Gravity Sedimentation(Á߷¿¡ ÀÇÇÑ Ä§Àü)
±¸µ¿·ÂÀ¸·Î Áß·ÂÀ» ÀÌ¿ëÇϴ ħÀüÀåÄ¡´Â ºÎÀ¯¼º ¹°Áú ¿ø¼ö·ÎºÎÅÍ °íÇü¼º ÀÔÀÚ(solid particle)¸¦ ºÐ¸®ÇÏ´Â °ÍÀ¸·Î ħÀüÁ¶(settling tank)¸¦ ¼³Ä¡Çϱâ À§ÇÑ Ä¿´Ù¶õ ºÎÁö¸éÀûÀÌ ÇÊ¿äÇÏ´Ù. ÀÌ´Â ¸Å¿ì È¿°úÀûÀÎ °ø¹ýÀ¸·Î ó¸® È¿À²Àº ħÀüÁö ¸éÀû¿¡ ÀÇÇÏ¿© ÁÖ·Î °áÁ¤µÇ´Â ÆíÀ̳ª ´ë¿ë·®ÀÇ ¹°·®À» ó¸®ÇÑ´Ù ÇÏ´õ¶óµµ ºñ±³Àû ÀûÀº ¿¡³ÊÁö¸¦ ÇÊ¿ä·Î ÇÑ´Ù.

Áï, ÇöÀåÀÇ ÃæºÐÇÑ ºÎÁö°¡ Á¦°ø °¡´ÉÇÏ¸ç ºñ±³Àû ÀûÀýÇÑ ºñ¿ëÀÇ Ã³¸®°¡ Çã¿ëµÈ´Ù¸é ÀÌ·¯ÇÑ Á߷¿¡ ÀÇÇÑ Ä§Àü ¹æ½ÄÀº ºÎÀ¯¼º ¹°ÁúÀ» ħÀü ºÐ¸®½ÃÅ°´Âµ¥ ¸Å¿ì ¸Å·ÂÀûÀÎ ¹æ¹ýÀÌ µÉ °ÍÀÌ´Ù. µû¶ó¼­ ÀÌ °ø¹ýÀº Á¤¼öó¸® ħÀü°øÁ¤, µµ½Ã¡¤»ê¾÷ Æó¼öó¸®, ¼±±¤(mineral processing) µî¿¡ Æø³Ð°Ô Àû¿ëµÇ°í ÀÖ´Ù.
 
±×·¯³ª Ç×»ó ÃæºÐÇÑ ºÎÁö°¡ È®º¸µÇ´Â °æ¿ì´Â ¸¹Áö ¾ÊÀ¸¸ç ±âÁ¸ ´ë¿ë·® ħÀüÀåÄ¡°¡ ¼³Ä¡µÇ¾î ÀÖ´Â ºÎÁö¸¦ ¿ì¼±ÀûÀ¸·Î È°¿ëÇØ¾ß ÇÏ´Â ÇöÀå¿¡¼­´Â Á¦ÇÑµÈ ºÎÁö ¸éÀû¿¡¼­µµ µ¿ÀÏÇÑ Ã³¸®È¿À²À» °®±â À§ÇØ Ä§ÀüºÐ¸®°øÁ¤(clarification process)À» °³¼±Çϱâ À§ÇÑ ¹æ¹ýÀ» ã¾Æ¾ß ÇÑ´Ù.
 
The separation of solid particles from a suspending liquid by sedimentation under the force of gravity is characterised by the need for large land areas on which to stand the settling tanks. It is potentially a very efficient process, with actual efficiency determined by the settlement area devoted to the task.

It is also a relatively low consumer of energy, even though it often has to deal with high volumetric flow rates, because the flow rates in terms of flow per unit cross sectional area of flow channel are quite low. If, therefore, there is land available, at a reasonable price, gravity sedimentation is an attractive means for clarifying dilute suspensions. For this reason, it is extremely widely used in fresh water clarification, in municipal and industrial waste water treatment, and in mineral processing and similar industrial applications.

However, there is not always sufficient land available, or there are higher priority uses for the land that is currently occupied by a large clarifier, so that considerable development has gone into improving the clarification process in order to achieve the same separation efficiencies in a smaller ground area.

Clarifiers and Thickners(ħÀü¡¤³óÃàÀåÄ¡)
º¸´Ù ±ú²ýÇÑ »óµî¼ö(overflow)¸¦ »ý»êÇϱâ À§ÇÑ ¸ñÀûÀÇ Ä§ÀüÀåÄ¡(clarifier)¿Í À¯ÀÔ¼öº¸´Ù ÈξÀ ³óÃàµÈ »óÅ·Π½½·¯Áö¸¦ ¹ß»ý½ÃÅ°´Â ¸ñÀûÀÇ ³óÃàÀåÄ¡(thickener)´Â ¼º´É °³¼±À» À§ÇÑ °³¹ß·Î ÀÀÁýÁ¦ Åõ¿©(coagulants) ¹× ȥȭÁ¦(flocculants)¸¦ »ç¿ëÇÏ°Ô µÇ¾ú´Ù. ±× °á°ú ºÎÀ¯¼º ÀÔÀÚ¹°ÁúµéÀº ±× Å©±â°¡ Ä¿Áö°Ô µÇ¾î ħÀüÀÛ¿ëÀÌ ºü¸£°Ô ÁøÇàµÉ ¼ö ÀÖ¾ú´Ù.

¼ö ½Ê³â Àü¿¡´Â ÇÕ¼ºÈ¥È­Á¦(synthetic flocculants)ÀÇ °³¹ß·Î ºÐ¸®±â´É È¿À²ÀÌ Å©°Ô Áõ°¡µÇ¾úÀ¸¸ç ÃÖ±Ù¿¡´Â ºÎÀ¯¼º °íÇü¹°Áú(suspended solids)°ú ºü¸£°í ¿Ïº®ÇÑ Á¢ÃËƯ¼ºÀ» °¡Áö´Â ȥȭÁ¦(flocculants) ¹°Áú °³¹ß¿¡ ¿¬±¸°¡ ÁýÁߵǰí ÀÖ´Ù.
 
º¸´Ù °³¼±µÈ ȥȭÁ¦°¡ ÷°¡µÈ ½Ã½ºÅÛÀ¸·Î´Â È£ÁÖ Outotec»ç°¡ °³¹ßÇÑ ³óÃà±â(thickener) ¿ëµµ·Î »ç¿ëµÇ´Â Â÷¼¼´ë¿ë Feedwell ½Ã½ºÅÛÀÌ ÀÖ´Ù. Feedwell ½Ã½ºÅÛÀÇ ¼³°è ³»¿ëÀº Áö³­ 40³â°£ Å« º¯È­´Â ¾ø¾úÁö¸¸ ó¸® ½Ã¿¡ À¯·®ÀÇ Áõ°¡ ¹× ¿¡³ÊÁö »ç¿ë µîÀÇ ¿ä±¸¿¡ ÀÇÇÏ¿© ÈξÀ ´Ù¾çÇØÁ³´Ù.

ƯÇã µî·ÏµÈ Outotec»ç Á¦Ç°ÀÇ ¼³°è´Â CFD(computational fluid dynamics) ¸ðµ¨¸µ äÅÃÀ¸·Î Â÷º°È­¸¦ °¡Á®¿ÔÀ¸¸ç, ÀÌ ½Ã½ºÅÛÀº vaneÀÇ inner floor ¼³°è¸¦ Ư¡À¸·Î ÇÏ¿© ½Ã½ºÅÛÀ» 2°³ÀÇ Á¸À¸·Î ºÐ·ùÇÏ¿© ¿îÀüµÇ´Â, Áï »óºÎ´Â mixing¿ëÀ¸·Î ÇϺδ aggregation¿ëÀ¸·Î ÀÛ¿ëÀ» ÇÏ°Ô µÇ¾î ÀÖ´Ù.
 
Clarifiers, which are intended to produce a clear overflow, and thickeners, which aim to produce an underflow considerably more concentrated than the feed suspension(often with a clear overflow as well), have been improved in performance by the use of coagulants and flocculants mixed with the feed suspension so as to increase the average size of the suspended particles, and so hasten settling.

The appearance of synthetic flocculants several decades ago gave a marked increase in separation efficiency, and modern developments have concentrated upon achieving rapid and complete contacting of the flocculant with the suspended solids, and, of course, in having available progressively more efficient flocculants.

An example of the improved flocculant addition and mixing system is the next generation feedwell introduced by Outotec, of Australia, particularly for thickeners(see Figure 1). Feedwell designs had changed little over the past 40 years or so, but the demands placed upon them have become more severe as flow rates have increased, and energy considerations have become more important.

The patented Outotec design has benefited from computational fluid dynamic modelling, and features an inner floor of vanes, separating the feedwell into two zones, an upper zone for mixing and a lower one for aggregation.

ÇÕ¼º Æú¸®¸Ó Àç·á(synthetic polymer)´Â Á߷¿¡ ÀÇÇÑ Ä§Àü(gravity sedimentation) °ø¹ý¿¡ ¸Å¿ì Å« ÀåÁ¡À» º¸¿©ÁÖ°í ÀÖÁö¸¸, º£¿Ã¸®¾ÆÀÇ Ä§ÀüÀåÄ¡(Actiflo compact clarification process)¿¡¼­ º¸´Â¹Ù¿Í °°ÀÌ ÀÌ·¯ÇÑ ÀåÁ¡À» °¡Áø À¯ÀÏÇÑ È¥È­Á¦(flocculant)¶ó°í´Â ¸»ÇÒ ¼ö ¾ø´Ù.

ÀÌ °ø¹ýÀº Ç÷ÏÀ» Çü¼ºÇϱâ À§ÇÑ ¹°Áú·Î ¹Ì¼¼¸ð·¡ ÀÔÀÚ(microsand particle)À» »ç¿ëÇϴµ¥, ÀÏ¹Ý ¸ð·¡ÀÔÀÚ º¸´Ù ´õ Á¶¹ÐÇÏ¿© ºÎÀ¯¼º °íÇü¹°ÀÇ Ä§ÀüÀÛ¿ë Ư¼ºÀ» ´õ¿í °³¼±½Ãų ¼ö ÀÖ¾úÀ¸¸ç, ±× °á°ú »óµî¼ö ¹°·®(overflow rates)¸¦ Áõ°¡½ÃÅ°¸ç ¹Ý¸é¿¡ ü·ù½Ã°£(retention time)Àº °¨¼Ò½ÃÅ°´Â È¿°ú¸¦ º¸¿©ÁØ´Ù.
 
±× °á°ú ÀÛÀº ±Ô¸ðÀÇ Ä§ÀüÁ¶(settling tank) ¼³Ä¡°¡ °¡´ÉÇØ ¼³Ä¡¸éÀûÀº ±âÁ¸ ó¸® Ç÷£Æ®º¸´Ù ÈξÀ Àû°Ô ÇÒ ¼ö ÀÖ´Ù. ¹Ì¼¼ ¸ð·¡ÀÔÀڴ ħÀüµÈ ½½·¯Áö·ÎºÎÅÍ È¸¼ö°¡ µÇ¸ç Ç÷£Æ® ³»¿¡¼­ Àç»ç¿ëÀÌ °¡´ÉÇÏ´Ù.

ħÀüÀåÄ¡ ¿¡¼­ °¡Àå °ý¸ñÇÑ ±â¼ú°³¹ßÀº ´ë±Ô¸ð ȸ»çµéÀÇ ¼öó¸® ºÐ¾ß °øÁ¤ °³¹ßÀ» À§ÇÑ ½ÃÀå ÁøÃâ¿¡ ÀÇÇØ ÀÌ·ïÁ³À¸¸ç À̵é ȸ»ç·Î´Â Veolia»ç¸¦ Æ÷ÇÔ Axel Johnson/Parkson, GE, Severn Trent, Siemens ¹× F L Smith µîÀÌ´Ù. À̵éÀº ¸ðµÎ È¿À²ÀûÀÎ ÆÐÅ°Áö ÇüÅ·Π¼³°èµÈ ħÀü Ç÷£Æ®¸¦ ¿î¿µÇÏ°í ÀÖ´Ù. ¸¹Àº ¾çÀÇ ¿ø¼ö 󸮸¦ À§ÇÑ Ä§Àü(clarification)¿¡¼­´Â ±âÁ¸ÀÇ ÀüÇüÀûÀΠħÀüÀåÄ¡(clarifier)º¸´Ù »õ·Î¿î ÀåÄ¡ °³¹ßÀ» ¿ä±¸ÇÏ°í ÀÖ´Ù.

ÀÌ·¯ÇÑ ±â¼úÀº ´Ü¼øÇÑ Ä§ÀüÀåÄ¡ ¶ó°í ºÎ¸£±âº¸´Ù´Â ÇÊÅ͸µ ¿©°úÀåÄ¡¸¦ °¡¸®Å°°í ÀÖÀ¸¸ç °¡Àå ¸Å·ÂÀûÀÎ °ÍÀ¸·Î´Â Fibra»çÀÇ ÇÊÅÍÁ¦Ç°ÀÌ´Ù. ÀÌ´Â ÇöÀåÁ÷°á ÀåÄ¡(in-line device) ÇüÅ·Π¼³Ä¡, ¿©·¯ °³ÀÇ ¼¶À¯»ç(fiber) ¹­À½À¸·Î ±¸¼ºµÇ¾î ÀÖ´Ù.

°¢°¢Àº ¿ø¼öÀÇ È帧°ú º´ÇàµÇ°Ô µ¿À۵Ǿî ÇÊÅ͸µ ±â´ÉÀ» ¼öÇàÇÏ¸ç ¼¼Á¤½Ã¿¡´Â ¼ø¹æÇâ(forward flush) È帧À¸·Î ¿îÀüµÈ´Ù. ÀÌ Á¦Ç°Àº ÀÌÁ¦±îÁö ºñ±³Àû ¼Ò±Ô¸ðÀÇ »ê¾÷Æó¼ö¿ëÀ¸·Î¸¸ Àû¿ëµÇ¾úÁö¸¸ ¸ðµâ ÇüÅ·ΠÁ¶¸³µÇ¸é º¸´Ù Å« ¹°·®µµ ó¸®ÇÒ ¼ö ÀÖ´Ù.
 
Although synthetic polymers have been of huge benefit to gravity sedimentation processes, they are not the only flocculant of current interest, as is shown by Veolia Water¡¯s Actiflo¢â(¢âÀº ÷ÀÚ) compact clarification process, which uses microsand particles as the seed for floc formation.

The denser sand particles give the suspended solids much improved settling characteristics, resulting in high overflow rates and short retention times. The resultant small settling tank footprint can be as little as one twentieth that of conventional plants. The microsand particles can be recovered from the settled sludge and recycled within the plant.

What must be counted as a major development in the field of clarification is the appearance on the treatment process marketplace of several large companies, who have all spotted the value of the water and wastewater business. These include Axel Johnson/Parkson, GE, Severn Trent, Siemens and F L Smidth, in addition to Veolia, all of whom now offer clarification plant in the form of efficient packages. The existence of a major process need in the clarification of such large quantities of liquid as is presented by the water and wastewater sectors attracts, not surprisingly, any number of new equipment developments aimed at taking some of this business from the conventional clarifier.

These are mostly filters rather than sedimenters, but one of the most intriguing is the Fibra filter, which is an in-line device, consisting of a bundle of fibres each parallel to the liquid flow, which are squeezed together pneumatically to act as the filter, and then expanded and forward flushed to clean(see Figure 2). Although demonstrated so far only on relatively small industrial waste applications, there is no reason why sufficient modules should not be mounted in parallel to achieve any required throughput.

Lamellar Separators
Á߷¹æ½Ä ħÀüÁ¶(gravity settler)ÀÇ ºÎÁö¸éÀû °¨¼Ò¸¦ À§Çؼ­´Â ħÀüÁ¶¸¦ ¿©·¯ °³ÀÇ ¹æ(floor)À¸·Î ºÐ¸® ¼³Ä¡ÇÏ¿© ±×µéÀ» À§¾Æ·¡ ÀûÃþ±¸Á¶·Î ÇÏ´Â °ÍÀÌ´Ù. ÃàÀûµÈ ½½·¯ÁöµéÀ» ¿ÜºÎ·Î ³»º¸³»±â À§Çؼ­´Â ÀÌ·¯ÇÑ ÀûÃþ±¸Á¶°¡ ¼öÆò±âÁØ 45¡­60µµ ±â¿ï±â·Î ¼³Ä¡µÇ¾î¾ß ÇÑ´Ù.
 
ÀÌ·¯ÇÑ ±â¿ï±â¸¦ °¡Áø tilted-plate(inclined-plate ȤÀº lamella)ÇüÅÂÀÇ Ä§ÀüÀåÄ¡(clarifier)´Â Çٽɺи® ¸ñÀû(main separator) ȤÀº Æú¸®½Ì¿ë ºÐ¸®(polishing separator)¿¡ »ç¿ëµÇ¸ç, ÀÌÁ¦´Â ħÀüÀåÄ¡ ½Ã½ºÅÛÀÇ ¸Å¿ì ÀϹÝÀûÀÌ°í ÀüÇüÀû ½Ã½ºÅÛÀ¸·Î Àνĵǰí ÀÖ´Ù.

ÀÌ·¯ÇÑ ±â¿ï±â ÇüÅÂ(tilted-plate) separatorÀÇ ¿îÀüƯ¼ºÀº ¹Ì¼¼ÇÑ ÀÔÀÚµéÀÌ ½Ã½ºÅÛÀÇ ¹Ù´ÚÀ¸·Î ¶³¾îÁö´Â À̵¿°Å¸®°¡ ¸Å¿ì ÀÛ´Ù´Â °ÍÀÌ´Ù. ´ÜÁ¡À¸·Î´Â ÇϺÎÀÇ È帧(underflow)»ó¿¡¼­ °í³óµµ ³óÃà»óÅ·ΠµÇÁö ¾ÊÀ¸¸ç ¶ó¸á¶ó(lamella) ÀçÁú Ç¥¸é¿¡ ½ºÄÉÀÏ ¹ß»ý ȤÀº ½ºÄÉÀÏ ºÎÂøµÇ´Â ±âȸ°¡ ¸¹´Ù.
 
ÆÐÅ°Áö ÇüÅ ¼öó¸® Ç÷£Æ®¿¡¼­ 1Â÷ ħÀüÁ¶(main settlement zone)À¸·Î ¿îÀüµÇ´Â tilted-plate separator´Â Veolia»ç Actiflo ½Ã½ºÅÛ¿¡¼­ º¼ ¼ö ÀÖ´Ù. Siltbuster»çÀÇ ¿î¼Û¿ë ºÐ¸®ÀåÄ¡(mobile separator)´Â tilted-plate packÀ» Àû¿ëÇÑ Á¦Ç°À¸·Î ªÀº ½Ã°£ ħÀü°øÁ¤ÀÇ ÀϹÝÀûÀÎ Á¦Ç°ÀÌ´Ù.
 
One of the ways in which the footprint for gravity settlers has been decreased was to cut the ¡°floor¡± of the settler into several pieces, and then to stack them one above the other. In order for any collected sludge to be able to escape, the sections have to be mounted at an angle(usually 45-60¡Æ) to the horizontal.

The resultant tilted-plate(inclined-plate or lamella) clarifier has become a familiar feature in sedimentation systems, either as the main separator, or as a polishing separator working on the overflow.

The main operating feature of the tilted-plate separator is that a suspended particle has only a small distance to fall before it reaches the ¡°floor¡± and so be removed from suspension. Its disadvantages are its inability to produce a sufficiently high solids concentration in the underflow, and the chances of scaling or deposition on the lamella surfaces.
 
The tilted-plate separator as the main settlement zone in a packaged water treatment plant can be seen in versions of the Veolia Actiflo¢â system mentioned above, while Siltbuster¡¯s range of mobile separators, employing tilted-plate packs, are a common sight wherever a short term need for clarification arises.
 
 
¡ã Fibra»çÀÇ ÇÊÅÍÁ¦Ç°. ÇöÀåÁ÷°á ÀåÄ¡(in-line device) ÇüÅ·Π¼³Ä¡, ¿©·¯ °³ÀÇ fiber ¹­À½À¸·Î ±¸¼ºµÇ¾î ÀÖ´Ù. °¢°¢Àº ¿ø¼öÀÇ È帧°ú º´ÇàµÇ°Ô µ¿À۵Ǿî ÇÊÅ͸µ ±â´ÉÀ» ¼öÇàÇÑ´Ù. ¼¼Á¤½Ã¿¡´Â ¼ø¹æÇâ(forward flush) È帧À¸·Î ¿îÀüµÈ´Ù.
Flotation System (ºÎ»ó½Ã½ºÅÛ)
ºÎÀ¯¼º °íÇü¹°ÁúÀÌ ÇϺηΠ¶³¾îÁö´Â Çö»ó°ú ´Þ¸®, ºÐ¸®¿ë º£¼¿ÀåÄ¡(separation vessel)ÀÇ »óºÎ·Î ¿À¸£°Ô µÇ´Â ¿ø¸®ÀÇ ºÎ»ó½Ã½ºÅÛ(flotation system)Àº ÀÏ¹Ý Ä§ÀüÀåÄ¡¿Í ¹Ý´ë°³³äÀ¸·Î ±âÆ÷(air bubble)°¡ °³°³ÀÇ ºÎÀ¯¼º ÀÔÀÚ¹°Áú°ú Á¢ÃËµÇ¸ç ±× °á°ú ºÎ·Â ¹ß»ýÀ» ÅëÇØ ºÎ»óÀÌ ÀÌ·ç¾îÁø´Ù.

º£¼¿ ÇϺο¡¼­ õ°øÇüÅÂÀÇ Æ©ºê(perforated sparge tubes)³ª ±â°èÀûÀΠȥÇÕÀåÄ¡(mechanical agitation)¿¡ ÀÇÇØ ¹ß»ýµÇ´Â ºÎ»ó½Ã½ºÅÛÀº ´ëºÎºÐ °¡¾ÐºÎ»ó ÇüÅÂ(dissolved air type)ÀÌ´Ù.
 
Áï °ø±â´Â ³ôÀº ¾Ð·Â »óÅ°¡ µÇ¸é ±ú²ýÇÑ ¹°ÀÇ È帧¿¡¼­ ¿ëÇØ, ±× °á°ú °úÆ÷È­ »óÅÂÀÇ ¹°·Î À¯ÀÔÀÌ ÀÌ·ç¾îÁö¸ç. ¿ëÁ¸»óÅÂÀÇ °ø±â´Â 50§­ Å©±âÀÇ ¹Ì¼¼ ±âÆ÷(fine bubble)»óÅ·Π¼Ö·ç¼Ç°ú ÇÔ²² ¹ß»ýµÈ´Ù.

ÀÌ·¯ÇÑ °¡¾ÐºÎ»ó(DAF) ½Ã½ºÅÛÀÇ °¡Àå Å« °³¹ßÀº À̸¦ ¶ó¸á¶ó ºÐ¸®»óÅÂ(lamella separator)¿Í °áÇÕ½ÃÄÑ °á±¹ ºÎ»óÀåÄ¡(flotation unit)ÀÇ ¼³Ä¡¸éÀûÀ» °¨¼Ò½ÃŲ °ÍÀ̾ú´Ù.
 
ÀÌ·¯ÇÑ ½Ã½ºÅÛÀ¸·Î´Â Siemens»çÀÇ RC series flotation plant¿¡¼­ º¼ ¼ö ÀÖ´Ù. °¡Àå ºü¸£°Ô ¿Ã¶ó¿À´Â ÀÔÀÚ¼º ¹°ÁúÀº ºÎ»ó¿ë ÅÊÅ©(flotation tank) À§·Î Á÷Á¢ À̵¿µÇ¸ç ¼­¼­È÷ ¿Ã¶ó¿À´Â ÀÔÀÚµéÀº plate pack¿¡¼­ ºÐ¸®°¡ ÀÌ·ç¾îÁø´Ù.

Siemens»çÀÇ ºÎ»óÁ¶Ç÷£Æ®´Â °¡¾ÐºÎ»óÁ¶(DAF)¿Í °ø±âÀ¯µµºÎ»ó(induced air flotation)À» °áÇÕÇÑ ½Ã½ºÅÛÀ̸ç GE»ç´Â entrapped air flotation ±â¼ú·Î Æó¼ö󸮿뿡 »ç¿ëµÇ°í ÀÖ´Ù. ºÎ»óÁ¶ Ç÷£Æ® Split-O-Mat ½Ã¸®Áî·Î Àß ¾Ë·ÁÁ® ÀÖ´Â Envvirocheme»ç´Â »õ·Î¿î Flomar ½Ã¸®ÁîÀÇ ½Ã½ºÅÛÀ» Áö³­ÇØ ¹ßÇ¥Çß´Ù. HL range ¸ðµ¨Àº ½ÄÇ° ¹× À°·ù»ê¾÷¿¡ Àû¿ëµÇ´Â °ÍÀ¸·Î ³ôÀº ºÐ¸®¼º´É È¿À²À» Ư¡À¸·Î ÇÏ°í ÀÖ´Ù.
 
The opposite of sedimentation in the sense that the suspended solids are caused to rise to the top of the separation vessel rather than fall to the bottom, flotation works by attaching an air bubble to each suspended particle or floc, giving it the buoyancy to rise.

Originally generated by perforated sparge tubes or mechanical agitation at the base of the vessel, most flotation systems are now of the dissolved air type, in which air is dissolved in a flow of clean water at high pressure, and the resultant super-saturated water is injected into the suspension, the dissolved air coming out of solution as fine bubbles, of the order of 50§­ in diameter.

A major improvement in the DAF system has come from allying it with a lamella separator, which significantly reduces the footprint of the flotation unit. Such a system can be seen in the Siemens RC Series flotation plants, where the fastest rising particles go straight to the top of the flotation tank, while the slower rising ones are separated in the plate pack.

Siemens¡¯y flotation plants are sold as featuring DAF and induced air flotation, while GE has a new technology for waste water treatment that it terms ¡°ntrapped air flotation¡± Already well known for its Split-O-Mat? series of flotation plants, Envirochemie launched last year a new Flomar series, among which the HL range features a high performance separation package especially suited to the food and meat industries.
 
 
¡ã °¡Àå ÃÖ±Ù °³¹ßµÈ ½ºÅ©¸° ÀåÄ¡´Â vibratory(ȤÀº gyratory) screen separator(Russel Finex»ç). Àç»ý¼ö(recycled water)ÀÇ Å©¸®´× ¹× ´Ù¸¥ ºÐ·ù±â´É ¿ëµµ·Î »ç¿ëµÇµµ·Ï Á÷°æ 2m±îÁö °³¹ßµÅ ÀÖ´Ù.
Screens(½ºÅ©¸° ÀåÄ¡)
½ºÅ©¸°(screen)Àº ħÀü ÀåÄ¡°¡ ¾Æ´ÏÁö¸¸ ¿©±â¿¡ ¾ð±ÞÇÏ´Â °ÍÀº ±¸µ¿·ÂÀÌ ÁÖ·Î Áß·ÂÀÛ¿ë¿¡ ÀÇÇØ ÀÌ·ç¾îÁö¸ç ÀÌ´Â »óÇϼöµµ ó¸® °øÁ¤¿¡¼­ Áß¿äÇÑ ±â´ÉÀ» ÇÏ°í Àֱ⠶§¹®ÀÌ´Ù.

½ºÅ©¸° ÀåÄ¡´Â ¿©·¯ ´Ù¾çÇÑ ÇüÅ·ΠÁ¸ÀçÇϴµ¥ ÁÖ·Î simple in-line strainer·ÎºÎÅÍ complex rotary drum screen ȤÀº multi-deck gyratory separator µîÀ¸·Î ±¸ºÐµÈ´Ù.
 
À̵éÀº º¸´Ù º¹ÀâÇÑ ÇÊÅ͸µÀ» ¿ä±¸ÇÏ´Â ¾×»ó È帧ÀÇ »óÇâ·ù(upstream) ±â´É, ÀÔÀÚ¼º ¹°ÁúÀÇ ºÐ¸®±â´É ¹× ºÒ±ÕÀÏÇÑ Å©±âÀÇ °ÇÁ¶(dry) ȤÀº ħÀû(wet) »óÅÂÀÇ È¥ÇÕµÈ °íÇü¼º ÀÔÀÚ¹°Áú·ÎºÎÅÍ 2°³ ÀÌ»óÀÇ ¹°ÁúÀ» ºÐ¸®Çϴµ¥ »ç¿ëµÈ´Ù.

ÀÌ·¯ÇÑ ºÐ·ù ±â´É ¿ªÇÒÀ» À§ÇÏ¿© ½ºÅ©¸°ÀåÄ¡´Â ÇÊ¿¬ÀûÀ¸·Î ±â°ø(aperture)ÀÇ Á¤È®µµ ¹× ÀÌÀÇ Á¤È®¼ºÀ» À¯ÁöÇϱâ À§ÇÑ ±â´ÉÀ» °¡Á®¾ß ÇÑ´Ù. µû¶ó¼­ º¸´Ù Å« ¿ë·®ÀÇ ±Ý¼Ó¼º ¸Þµð¾Æ, Áï perforated plate³ª crimped wire mesh ÇüÅ·Π»ç¿ëÀÌ ¿ä±¸µÈ´Ù.

°¡Àå ÃÖ±Ù °³¹ßÀÇ ½ºÅ©¸° ÀåÄ¡´Â Áøµ¿ÇüÀÇ vibratory(ȤÀº gyratory) screen separator·Î Àç»ý¼ö(recycled water)ÀÇ Å©¸®´× ¹× ´Ù¸¥ ºÐ·ù±â´É ¿ëµµ·Î »ç¿ëµÇµµ·Ï Á÷°æÀÌ 2m±îÁö °³¹ßµÅ ÀÖ´Ù. ÀÌ·¯ÇÑ Á¾·ùÀÇ Á¦Ç°Àº Kason, Russel Finex, Sweco µî Á¦Á¶»ç·ÎºÎÅÍ °¡´ÉÇÏ´Ù.

Screens are not sedimentation devices, but they are covered in this article because the driving force is often that of gravity, and they are a significant component of the treatment processes for water and waste water, in common with the clarifiers just discussed.

Screens exist in a wide range of types, from the simple in-line strainer to the complex rotary drum screen or the multi-deck gyratory separator. They are used for separation of particles from a liquid flow, usually in a position upstream of a more delicate filtration requirement, and for separating two or more fractions from a mixture of differently-sized solid particles, either in the dry or wet state.

For this classification duty, an essential feature of the screen is the accuracy of its apertures, and its ability to retain this accuracy in use. This results in large-scale use of metallic media, either perforated plates, or crimped wire mesh.

The most developed of the screen types is the vibratory(or gyratory) screen separator, which is now available in sizes up to 2m in diameter, for cleaning of recycled water, and other scalping and classification duties. As evidenced by the pages of Filtration + Separation, new features are available from manufacturers, such as Kason, Russell Finex, and Sweco on an almost annual basis(see Figure 3).
 
 
¡ã TETRA Deep Bed tertiary filter Á¦Ç°.
Deep Bed Filters(¿©°úžÇü ÇÊÅÍ)
¿©°úžÇü ÇÊÅÍ(Deep Bed Filter)´Â ħÀüÀåÄ¡°¡ ¾Æ´ÏÁö¸¸ ´ë´Ù¼ö ½Ã½ºÅÛÀÌ Áß·ÂÀÛ¿ë(hydraulic head)¿¡ ÀÇÇØ ¿îÀüµÇ¸ç Áß·Â½Ä Ä§ÀüÀåÄ¡ ¹× ºÎ»ó Ç÷£Æ®¿Í º´ÇàÇÏ¿© »óÇϼöµµ ó¸® ¿ëµµ·Î »ç¿ëµÇ°í ÀÖ´Ù.

À̵éÀº ½ÇÁ¦·Î ¸ð·¡ ÀÔÀÚµéÀÇ Æ´»õ ¾È¿¡ ½ÉÃþ ¿©°ú¿¡ ÀÇÇØ ÀÛ¿ëµÇ´Â °ÍÀ¸·Î(º£µåÀÇ ÃÖ»óºÎ¿¡¼­ »ý¹°ÇÐÀû ¹ÝÀÀÀ¸·Î »ç¿ëµÇ´Â ¿Ï¼Ó È帧ÇüÅÂÀÇ ¸ð·¡ ¿©°ú±â´Â Á¦¿Ü), ÃàÀûµÈ ¹°ÁúµéÀº ¹°ÀÇ »óÇâ·ù ÀÛ¿ë¿¡ ÀÇÇÑ Ç÷¯½ÌÀ¸·Î ÁÖ±âÀûÀ¸·Î Á¦°ÅµÇ¸ç °É·¯Áø °íÇü¹°Áú(trapped solids)Àº ¹èÃâÀÌ ÀÌ·ç¾îÁ®, ±× ÀÌÈÄ º£µå³»ÀÇ ¹°ÁúµéÀº Á¤»óÀûÀÎ ÃæÁø ³ôÀÌ ¼öÁØÀ¸·Î µÇµ¹·Á Áø´Ù.

Áö³­ ¼ö³â°£ÀÇ º£µåÇü ÇÊÅÍÀÇ °³¹ßÀº ÁÖ·Î ÀÚü °íÀ¯ÀÇ ¹®Á¦Á¡À» ÇØ°áÇϴµ¥ ¸ñÀûÀ» µÎ¾ú´Ù. Áï, Á¶´ë ÀÔÀÚ(coarse particle)¸¦ ¸ÕÀú Á¦°ÅÇÏ°í ¹Ì¼¼ÀÔÀÚ(fine particle)À» ³ªÁß¿¡ Á¦°ÅÇÏ´Â °¡Àå È¿°úÀûÀÎ ÇÊÅÍ ¿©°ú ¹æ¹ýÀ» ã´Â °ÍÀ¸·Î Ç÷¯½Ì ÇÏ´Â µ¿¾È º£µåÀÇ È®Àå ¹× ÀçÁ¶Á¤ (resettlement) °úÁ¤Àº ¸ð·¡ÀÇ ÀûÃþÀ» »óºÎ´Â ¹Ì¼¼ÇÑ ±¸Á¶·Î ÇϺδ Á¶´ë ±¸Á¶·Î ±¸¼ºµÇµµ·Ï ÇÏ¿´´Ù.

ÀÌ·¯ÇÑ ¹®Á¦¿¡ ´ëÇÑ °¡Àå È¿°úÀû ÇØ°áÃ¥Àº ´ÙÃþ¿©°úž(multi-media bed)À¸·Î ´Ù¾çÇÑ Á¾·ùÀÇ ¹Ìµð¾î°¡ ¼­·Î ´Ù¸¥ ¹Ðµµ·Î º£µå ³»¿¡ ÀûÃþ, »óÃþºÎ¿¡¼­´Â ´ú Á¶¹ÐÇÏ°Ô µÇ¾î ¹Ìµð¾î°¡ °¡Àå ¿Ï¸¸ÇÑ ¼Óµµ·Î ÀçÁ¶Á¤µÇ¸ç ÇϺδ ´õ¿í Á¶¹ÐÇÏ°Ô ±¸¼ºµÇ´Â ±¸Á¶ÀÌ´Ù.
 
Although also not a sedimentation device, the deep bed filter is included here because many do operate by means of gravity (i.e. hydraulic head), and the greater proportion of them is used in the water and wastewater treatment applications alongside(or instead of) gravity clarifiers and flotation plants.

They work actually by depth filtration within the interstices of the sand particles(except for the slow sand ¡°ilters¡±that use a biological reaction in the topmost layer of the bed). The collected materials must be removed periodically, which is done by flushing with water in upward flow, to expand the bed and release the trapped solids, after which the bed solids are allowed to settle back to their normal layer height.

The developments of the deep bed filter over the years have mainly been aimed at overcoming its innate limitations - the wish to filter downwards through coarse particles and then fine for the most effective filtration, whereas the expansion and resettlement of the bed during flushing leaves the sand with the finest particles on top and the coarsest on the bottom.

The most effective solution to this problem has been the multi-media bed, which has layers of different materials essentially of differing densities laid in the bed with the least dense, which resettles most slowly, as the top layer, and the most dense at the bottom.

¡ã DynaSand filter. ÀÌ ÇÊÅÍ´Â nutrient(ÀÎ ¹°Áú) Á¦°Å¿ëÀ¸·Î »ç¿ëµÈ´Ù.

¿©°úžÇü ÇÊÅÍÀÇ °¡Àå ÃÖ±Ù °³¹ßÀº ÀÏ¹Ý ¼öó¸® ¹× Æó¼öó¸®ÀÇ 3Â÷ ó¸® °øÁ¤¿¡ 2Â÷ ó¸® ÀÇ ÁÖµÈ °øÁ¤ÈÄ¿¡ Æú¸®½Ì ÇÊÅÍ ±â´ÉÀ¸·Î »ç¿ëµÇ´Â °ÍÀÌ´Ù. ÀÌ Á¦Ç°ÀÇ ¿¹´Â Severn Trent»çÀÇ TETRA Deep Bed tertiary filter Á¦Ç°À¸·Î ½±°Ô ¿Â¿ÀÇÁ °¡´ÉÇÑ ÇÏÇâ·ù(downflow) ÇüÅ·Π¿îÀüºñ¿ëÀ» ÃÖÀûÈ­ÇÑ ¸ðµ¨ÀÌ´Ù. ÀÌ ±â¼úÀº ±× ÈÄ¿¡ °íÇü¹° Æ÷Áý(solid capture)°ú Áú¼Ò ¼ººÐÀÇ »ý¹°ÇÐÀû Á¦°Å¸¦ µ¿½Ã¿¡ ÇÒ ¼ö ÀÖ´Â TETRA Denite systemÀ¸·Î °³¹ßµÆ´Ù.

¶ÇÇÑ ¿ëÁ¸¼º ö¹°Áú, ¸Á°£, ºñ¼Ò ¹× Ȳȭ¼ö¼Ò ±×¸®°í ºÎÀ¯¼º ¹Ì¸³ÀÚ ¹°ÁúÀ» Á¦°ÅÇÏ´Â manganese greensand ÇüÅ·Π¿©·¯ °¡Áö Á¾·ùÀÇ ¿©°úž ÀûÀç ¹Ìµð¾î(bed media)°¡ Inversand Company¿¡ ÀÇÇØ °ø±ÞµÇ¸ç ÃÖ±ÙÀÇ °³¹ßÇ°ÀÎ Greensand Plus Á¦Ç°Àº ¸¶Âû¿¡ ¸Å¿ì Å« ÀúÇ×·ÂÀ» °¡Áö°í ÀÖ´Ù.

ÇÑÆí, °íÁ¤»óÀÇ fixed deep bed filterÀÇ °¡Àå Áß¿äÇÑ °³¹ßÀº À̵¿¼ºÀÇ moving bed formatÀÇ Ã¤ÅÃÀ¸·Î bed mediaÀÇ ¹Ì¼¼ÇÑ Á¶°¢µéÀÌ ºÐ¸®Áö¿ª(separation zone)¿¡¼­ ÇÏÇâÀ¸·Î À̵¿ÇÏ´Ù°¡ À¯Ã¼ÀÇ À̵¿ È帧¿¡ µû¶ó ¸ð¾ÆÁ®¼­ °á±¹ Ŭ¸° Á¸À¸·Î »óÇâ À̵¿µÈ´Ù.
 
Áï, ÇÊÅÍÂÊÀ¸·Î µÇµ¹¾Æ°¡´Â »çÀÌŬ¿îµ¿À» ÇÏ°Ô µÇ¸ç, ÀÌ·¯ÇÑ ÀåÄ¡´Â ÇÑ Á¾·ùÀÇ ¹Ìµð¾î ÀÔÀÚ¹°Áú(bed particle)À» ÇÊ¿ä·Î Çϳª °íÁ¤Çü º£µå(fixed bed)º¸´Ù ÈξÀ Å« ³ôÀÌÀÇ °ø°£(vertical space)¸¦ ÇÊ¿ä·Î ÇÑ´Ù. ÀÌ ÀåÄ¡´Â Parkson»çÀÇ DynaSand Á¦Ç°ÀÌ ÁÁÀº ¿¹À̸ç ÀÌ´Â ÇöÀ纸´Ù °­È­µÈ nutrient(ÀÎ ¹°Áú) Á¦°Å¿ëÀ¸·Î »ç¿ëµÈ´Ù.
 
One of the most recent developments of the deep bed filter has been its use in the tertiary stages of water and waste treatment, as a polishing filter after the secondary active process. An example of this is SevernTrent¡¯ TETRA¢âDeep Bed tertiary filter, which is a downflow unit that can be readily switched on and off, thus optimising operating costs.

This has been further developed as the TETRA Denite¢âsystem, which combines solids capture with the biological removal of nitrogen (as nitrate). A different kind of bed medium is now supplied by the Inversand Company, in the form of a manganese greensand that not only removes suspended particulate material, but also dissolved iron, manganese, arsenic and hydrogen sulphide. The latest version, Greensand Plus, has much greater resistance to attrition.

The most important development of the fixed deep bed filter has been its adaptation to a moving bed format, in which the bed of granules falls downwards from a separation zone, to be picked up in a flow of transporting fluid, which carries it upwards to a cleaning zone, from which it falls back to the filter to complete the cycle. This requires just one grade of bed particle, but takes up much more vertical space than the fixed bed. Parkson¡¯DynaSand¢â is a good example of such a system, now used for enhanced nutrient (i.e. phosphorus) removal.
 
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