Procedure Lab Test for COD and BOD

1. Proced Procedure ure lab test test for for COD COD and and BOD BOD BOD TEST PROCEDURE

1. To ensure ensure proper biolog biological ical activity activity during during te te BOD test! test! a "aste"ater "aste"ater sa#ple$ sa#ple$

a. %ust be free of clorine. &f clorine is present in te sa#ple! a declorination ce#ical 'e.g! sodiu# sulfite( #ust be added prior to testing.  b. )eeds to be in te p* range of +., - ., S.U. &f te sa#ple is outside tis range! ten acid or base #ust be added as needed. c. )eeds to ave an e/isting ade0uate #icrobiological population. &f te #icrobial  population is inade0uate or unno"n! unno"n! a 2seed2 solution of bacteria is added along "it an essential nutrient buffer solution tat ensures bacteria population vitality.

3. Speciali4ed Speciali4ed 566 566 #7 BOD bottles bottles designed designed to to allo" full full filling filling "it no no air space space and  provide an airtigt seal are used. Te bottles are filled "it te sa#ple to be tested or  dilution 'distilled or deioni4ed( "ater and various a#ounts of te "aste"ater sa#ple are added to reflect different dilutions. 8t least one bottle is filled only "it dilution "ater as a control or 2blan.2

5. 8 DO DO #eter is used to #easure #easure te initial initial dissolved dissolved o/yge o/ygen n concentration concentration '#g97( '#g97( in eac bottle! "ic sould be a least :.6 #g97. Eac bottle in ten placed into a dar incubator at 36;C for five days.

<. 8fter five five days '= 5 ours( te te DO #eter #eter is used again again to #easure #easure a final final dissolved dissolved o/ygen concentration '#g97(! "ic ideally "ill be a reduction of at least <.6 #g97.

,. Te final final DO reading reading is ten ten subtracted subtracted fro# fro# te initial initial DO reading reading and and te result result is te BOD concentration '#g97(. &f te "aste"ater sa#ple re0uired dilution! te BOD concentration reading is #ultiplied by te dilution factor.

COD TEST PROCEDURE 1. Prior to co#pleting te COD test! a series of no"n standards are prepared using >*P 'potassiu# ydrogen ptalate(. %ost "aste"ater sa#ples "ill fall in te ig range! so standards of 166! 3,6! ,66 and 1666 #g97 are typically prepared. COD standards can also be purcased. 3. 8 COD reactor9eating '1,6;C( bloc and a colori#eter are turned on so tat bot instru#ents are allo"ed to stabili4e. 5. Pre-prepared lo"-range '5 - 1,6 pp#( or ig-range '36 - 1,66 pp#( vials are selected for te COD test based on e/pected results. Bot ranges can be used if e/pected results are unno"n. <. One vial is #ared as a ?blan!@ and tree or four vials are #ared "it no"n standard levels. T"o vials are ten #ared for te "aste"ater sa#ple to #ae a duplicate run. )ote$ &f #ultiple "aste"ater sa#ples are being run! at least 16A of sa#ples are duplicated. ,. 3 #7 of li0uid are added to eac vial. &n te case of te ?blan!@ 3 #7 of D& "ater are added. 3 #7 of eac standard are added to te corresponding vials. &f te "aste"ater  sa#ple is tested at full strengt! ten 3 #7 is added to te corresponding vial. &f dilution is re0uired! ten serial dilutions are perfor#ed and 3 #7 of te diluted sa#ple are added to te corresponding vial. +. Eac vial is #i/ed "ell and placed into te reactor bloc for t"o ours. 8fter t"o ours! te vials are re#oved fro# te bloc to a cooling rac for about 1, #inutes. . Te colori#eter is set and calibrated per te specific instructions for tat unit 'i.e.!  proper "avelengt! blan and standards( and eac vial is placed in te unit and te COD concentration read. :. &f te sa#ple "as diluted! te corresponding #ultiplication is #ade.

3. %eaning of BOD and COD i. BOD 'bio-ce#ical o/ygen de#and( BOD is te traditional! #ost "idely used test to establis concentration of organic #atter in "aste"ater sa#ples. &t is based on te principle tat if sufficient o/ygen is available! aerobic biological deco#position by #icroorganis#s "ill continue until all "aste is consu#ed.

ii. COD 'ce#ical o/ygen de#and( COD is te #ost popular alternative test to BOD for establising te concentration of organic #atter in "aste"ater sa#ples. Te COD test only taes a fe" ours to co#plete! giving it a #aor advantage over te ,-day BOD test. aste"ater treat#ent syste# personnel can use COD as an al#ost real-ti#e operational adust#ent para#eter. 5. BOD and COD li#itation before discarge to river  Te #a/i#u# BOD and COD values "ere 11.+ #g9l and 35. #g9l! respectively in river "ater. Tere "as a significant degree of self-purification as te river "ater flo"s. <. , Different of BOD and COD COD BOD 1. %ore specific  values are generally 1. 7ess specific and value are lo"er tan COD 3. ill generate a iger concentration reading tan 3. "ill generate a lo"er concentration reading ta BOD for a particular "aste"ater sa#ple! 5. Te total #easure#ent of all ce#icals including organics  in-organics in te "ater or "aste "ater <. &ncludes bot biodegradbale and non biodegradable substances

COD for a particular "aste"ater sa#ple 5. %easure of te a#ount of o/ygen tat re0uire f  te bacteria to degrade te organic co#ponents  present in "ater or  "aste "ater  <. contains only bio-degradable.

,. #easure#ents can be #ade in a fe" ours

,. #easure#ents tae five days.

,. at is BOD,F Te BOD test is also no"n as 2BOD,2 since it is based on te accurate #easure of DO 'dissolved o/ygen( at te beginning and end of a five-day period in "ic te sa#ple is eld in dar! incubated conditions