CFIEAlTSTRY AND INDUSTRY
?!)!I usccl for ench night's tre:it.iiiciit WIIR 12 11). It was fount1 that tlic nictliuin on Xo. 3 bCCillllC clcriiicr tlinii thc iiicdiuni on tlic unchlorinntccl coiit.rol filters (Xos. 1 nntl 2) and also sonic slight poiitling on tlic filters wiis relicvcd on Xu. 3. Unfortunittcly tlic trciit~~ii~nt, rrtluccd pirrificotioii efficiency. l-Iowcvcr, it is iiidiciitcd tliiit such trcntnicnt; ~1 1 1 1 coiitrol t.lic clcnnlincss of n filter : I I I ~ also rclicvc slight poiiding.
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Coscmsross
The resii1t.s nbtninctl arc prol~il~ly not ns COlllplCtC ns ~iiiglit I c dcsircd owing to tlic sitinll niiitil~er of filters used for cspcriitic~it, nuil tlic ~a r i i i t i ~~i s i n ~tiotlc of const riiction, ngc, condition, nnd geiicriil bc~linviour of the few filters ~vliicli \VCI'C clnployctl. This h v e v c r , docs not imply t.lint tlic tlntn cnnnot lie uscfully :ipplictl to othcr filters aud poutling prolilcitis. Tlir results support thc following concliisions :
(i) The relief of ~vcll-cstn.I~lislict11 poncling is n dilliciilt, iiiittter ncccssitiiting drastic trciltnicut with Iiirgc doses of chlorine (0.5 'to 1% CI,) prcfernbly iipplictl its strong chlorine writer, b1e:ich solution, or Iiypochloritc direct to tlic surfiicc nicdiii~ii, siiy, by liose or \v:itcring cans. Suclt t rent ittent, will generally rctlucc filter piirifitxition ctlicicncy but t liis i~ uot sc!rioiis since a filter rliiickly recovers froiti i i i i ovcrtlosc of chlorine :iiitI, in any case, elficicncy will :tlrcntly IJC low owiiig to poiiding. With winter ponding it is evident tlitrt clriistic I rcatnient :q)pc;irs c:ip;iIh of giving rapid relief, iiud ulilcss relief is rilpid it is of Iittlc .i~lucJ since the lo^ clticieucy owing to ponding is niost ~i ~i t l ~~i ~i t l h rind t h ~iouding will take iL lotlg tiinc to clcilr 11it.t 1triilly. IU p i e d , winter pnndiiig does not. dispcrsc Iiiitl1ritlly iiritil the spring.
(ii) In tliosc ciiscs where \vcll-cstiilJlislictl pontling is nwiiig to the iigc and cloggcil coiiditioii of the filter csccptionnlly drastic trcntiiiciit is rcquirctl i111d tlic results obtniucd by forking solid blcitching powder into the nicdiuni iirc proi~iising. Tlic tcuipornry iiiciipacitiition of such n filter is of little importi~nce since i l l 1 old filter ciuiliot trciitt u fill1 load of se\vilgc ellicic~~tly iilitl t,lius nnythiiig thiit C ~U be done to IIICL'C~ISU its ciipncity iiutl cflicicncy is justificd. \Vhcthcr it is