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Sedimentation behaviour of red mud—reply
Letters
to the Edrtors
the pomt of vtew of condmons of mrcrobml growth The activated sludge pumped from a clardier to a tubular reactor was subjected to changes m the envrronment condtttons (step excttatrons on the substrate concentratton) Of course, the lag m specrfic growth rate should be taken mto account for calculattons of extt concentratrons m a tubular reactor
MAREK WOJCIK Technical and Agnculturol Academy Deportment of Technology and Chemrcoi 85-326 Bydgoszcz, Semrnarypw 3 Poland
Chem~ol En@neenng Scrence 1979 Vat 34 p 753
Enguaeenng
Pergamon Press
753 REF?SRJ?,NCES
[II Wotfbauer D, Klettner H and Moser F, Chem Engng Scr 1978 33 953 r21 Mateles R I , Ryu D Y and Yasuda T , Nature 1%5 208 263 Bloeng 1%7 9 [31 Galley J W and Bungay H R, Biofechnol 617 Bloeng 1968 10 [41 GllIey J W and Bungay H R , Blotechnol 99 (51 Storer F F and Gaudy A F, Enulr SCI Tech 1969 3 143 I61 Sundstrom D W , Klet H E and Brookman G T , Blotechnol Broeng 1976 18 1 Broeng 1977 19 1431 [71 Chase L M , Brotechnof [81 Elmaleh S and Ben Atm R , Chem Engng SCJ 1978 33 365 [9l Perret C J , J Gen Muzrobrol l%O 22 589
Pi-Wed III Great Bntam
(Recerved
for pubhcatwn
Dear Strs, WoJcrk (see above) has grven very mterestmg comments on the paper we have pubhshed 111thrs ~ourna![l], that would deserve thorough drscusslon At thrs moment only a few remarks on hrs contrtbutton shaJl be made It 1s selfevtdent, that the change tn the concentratron of the surroundmg substrate IS much more pronounced m case of a plug 0ow aeratron basm, than m a basm with strrred tank charactenshc. and that a hrgher mfluence of a lag phase ts to be expected m a plug flow basm However, d we assume the substrate concentratron to be gtven as BOD. COD or TOC. as m [l], then another effect IS much more effective. that hasbeen called “adsorptron” [2,3] It ISvery much enhancmg the ehmmahon of the substrate from the waste water tn the Brst tune after entertng the aeration bastn A lag phase tn BOD removal practrcally does not take place due to adsorption, a lag phase m oxygen consumptron accordmg to our experience 1s not eifectrve enough by far to explant the equal performance of a plug flow basm and a bastn with hrgh backmtxmg, this IS shown by the fact, that the maxrmum of the oxygen consumptton takes place very soon after mtxmg acttvated sludge and waste water Out of thrs reason the uuhzatron of the ktnetrc model of Wuhrmann[4] can be Justied as a tirst approxunation for m case of synthetrc waste waters the reahty Of a superpositron of the elunmatton reactrons has been proved[4]. and It gtves a reahsttc picture of the mfluence of restdence tnne drstrtbution on the steady state performance of the basm Of course the zero order reactrons Wuhrmann assumes can be regarded as Monod reactrons wtth very low values of K, A closer aproxunatron to reahty ISachreved by a model mcludmg ehnunatron by adsorptron[3], thrs model however at the moment IS formulated only for plug flow basms, we hope that we shah be able to extend thus type of model to basms with hrgher backnuxmg
15 March
1979)
We feel, that the mcorporatton of the dynamics of bacterial growth. especraily of the dynamtcs of adJustmg the specdic growth rate to the model should be done as a further refinement, modelltng however always IS a compromtse between the accuracy and the complexrty of the model We therefore would hke to conclude, that the kmetrc model of Wuhrmann is of course not the final or stngle answer to the problems of modelhng the activated sludge process, d avoids however serious mrstakes that occur when a Monod type model IS used and substrate 1s descnbcd by a gross parameter as BOD or COD, espectally when the performance of a contmuous plants IS to be calculated based on batch data The authors would hke to correct an erraneous cm&Ion of a paper by Joschek er al [5] Thts paper does not show a factor of 3 between kmettcs measurements m a batch reactor and a contmuous plant, but a factor of about 1 7,t e a divergence of about the thrted Instrtut for Chemical Fundamentals Technrcal Unruersrty Austno
Engmeenng of Grar
0
WOLFBAUER H KLETTNER F MOSER
REFERENCES [l] Wolfbauer 0 , Klettner H and Moser F , Chem Engrtg Scr 1978 33 953 [2] Theophrlou J , Wolfbauer 0 and Moser F , gwflwasserobwasser 1978 119 H 3 S 135/14O [3] Theophtlou J , Wolfbauer 0 and Moser F , gwflwasserobwosser tn press [4] Wuhrmann K and Beust F , Schwerz Zertschr Hydrologre 1958 xx [5] Joschek H , Dehler J , Koch W , Engelhardt H and Getger W , Chemre-Ing Techntk 1975 47(10) 422
to the Edrtors
the pomt of vtew of condmons of mrcrobml growth The activated sludge pumped from a clardier to a tubular reactor was subjected to changes m the envrronment condtttons (step excttatrons on the substrate concentratton) Of course, the lag m specrfic growth rate should be taken mto account for calculattons of extt concentratrons m a tubular reactor
MAREK WOJCIK Technical and Agnculturol Academy Deportment of Technology and Chemrcoi 85-326 Bydgoszcz, Semrnarypw 3 Poland
Chem~ol En@neenng Scrence 1979 Vat 34 p 753
Enguaeenng
Pergamon Press
753 REF?SRJ?,NCES
[II Wotfbauer D, Klettner H and Moser F, Chem Engng Scr 1978 33 953 r21 Mateles R I , Ryu D Y and Yasuda T , Nature 1%5 208 263 Bloeng 1%7 9 [31 Galley J W and Bungay H R, Biofechnol 617 Bloeng 1968 10 [41 GllIey J W and Bungay H R , Blotechnol 99 (51 Storer F F and Gaudy A F, Enulr SCI Tech 1969 3 143 I61 Sundstrom D W , Klet H E and Brookman G T , Blotechnol Broeng 1976 18 1 Broeng 1977 19 1431 [71 Chase L M , Brotechnof [81 Elmaleh S and Ben Atm R , Chem Engng SCJ 1978 33 365 [9l Perret C J , J Gen Muzrobrol l%O 22 589
Pi-Wed III Great Bntam
(Recerved
for pubhcatwn
Dear Strs, WoJcrk (see above) has grven very mterestmg comments on the paper we have pubhshed 111thrs ~ourna![l], that would deserve thorough drscusslon At thrs moment only a few remarks on hrs contrtbutton shaJl be made It 1s selfevtdent, that the change tn the concentratron of the surroundmg substrate IS much more pronounced m case of a plug 0ow aeratron basm, than m a basm with strrred tank charactenshc. and that a hrgher mfluence of a lag phase ts to be expected m a plug flow basm However, d we assume the substrate concentratron to be gtven as BOD. COD or TOC. as m [l], then another effect IS much more effective. that hasbeen called “adsorptron” [2,3] It ISvery much enhancmg the ehmmahon of the substrate from the waste water tn the Brst tune after entertng the aeration bastn A lag phase tn BOD removal practrcally does not take place due to adsorption, a lag phase m oxygen consumptron accordmg to our experience 1s not eifectrve enough by far to explant the equal performance of a plug flow basm and a bastn with hrgh backmtxmg, this IS shown by the fact, that the maxrmum of the oxygen consumptton takes place very soon after mtxmg acttvated sludge and waste water Out of thrs reason the uuhzatron of the ktnetrc model of Wuhrmann[4] can be Justied as a tirst approxunation for m case of synthetrc waste waters the reahty Of a superpositron of the elunmatton reactrons has been proved[4]. and It gtves a reahsttc picture of the mfluence of restdence tnne drstrtbution on the steady state performance of the basm Of course the zero order reactrons Wuhrmann assumes can be regarded as Monod reactrons wtth very low values of K, A closer aproxunatron to reahty ISachreved by a model mcludmg ehnunatron by adsorptron[3], thrs model however at the moment IS formulated only for plug flow basms, we hope that we shah be able to extend thus type of model to basms with hrgher backnuxmg
15 March
1979)
We feel, that the mcorporatton of the dynamics of bacterial growth. especraily of the dynamtcs of adJustmg the specdic growth rate to the model should be done as a further refinement, modelltng however always IS a compromtse between the accuracy and the complexrty of the model We therefore would hke to conclude, that the kmetrc model of Wuhrmann is of course not the final or stngle answer to the problems of modelhng the activated sludge process, d avoids however serious mrstakes that occur when a Monod type model IS used and substrate 1s descnbcd by a gross parameter as BOD or COD, espectally when the performance of a contmuous plants IS to be calculated based on batch data The authors would hke to correct an erraneous cm&Ion of a paper by Joschek er al [5] Thts paper does not show a factor of 3 between kmettcs measurements m a batch reactor and a contmuous plant, but a factor of about 1 7,t e a divergence of about the thrted Instrtut for Chemical Fundamentals Technrcal Unruersrty Austno
Engmeenng of Grar
0
WOLFBAUER H KLETTNER F MOSER
REFERENCES [l] Wolfbauer 0 , Klettner H and Moser F , Chem Engrtg Scr 1978 33 953 [2] Theophrlou J , Wolfbauer 0 and Moser F , gwflwasserobwasser 1978 119 H 3 S 135/14O [3] Theophtlou J , Wolfbauer 0 and Moser F , gwflwasserobwosser tn press [4] Wuhrmann K and Beust F , Schwerz Zertschr Hydrologre 1958 xx [5] Joschek H , Dehler J , Koch W , Engelhardt H and Getger W , Chemre-Ing Techntk 1975 47(10) 422