research article removal of the 2-mercaptobenotiazole from...

Research ArticleRemoval of the 2-Mercaptobenotiazole fromModel Wastewater by Ozonation

Jan Derco1 Angelika Kassai2 Michal Melicher1 and Jozef Dudas1

1 Faculty of Chemical and Food Technology Slovak University of Technology Radlinskeho 9 812 37 Bratislava Slovakia2Water Research Institute Nabr Arm Gen L Svobodu 5 812 49 Bratislava Slovakia

Correspondence should be addressed to Jan Derco jandercostubask

Received 31 August 2013 Accepted 20 October 2013 Published 23 January 2014

Academic Editors J J Brandner and M A Centeno

Copyright copy 2014 Jan Derco et alThis is an open access article distributed under theCreativeCommonsAttributionLicense whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The feasibility of ozonation process for 2-mercaptobenzothiazole (2-MBT) removal follows from results of ozonation of the modelwastewater Total removal of 2-MBT was observed after 20 minutes of ozonation Very good reproducibility of repeated ozonationtrials including sampling and analysiswas observedHowever themajority of dissolved organic carbon (DOC) and chemical oxygendemand (COD) remained in the reaction mixture Benzothiazole (BT) and 2-hydroxybenzothiazole (OBT) intermediates wereidentified during degradation of 2-MBT with ozone In addition to the above benzothiazole derivatives the creation of some otherorganic compounds follows from results of mass balance The best fits of experimental data were obtained using the first kineticmodel for 2-MBT and zero-order kinetic model for COD and DOCThe reaction time of 60 minutes can be considered as effectivewith regard to controlled oxidation in order to increase a portion of partially oxidized substances Higher biodegradability andlower toxicity of ozonation products on respiration activity of activated sludge microorganisms was observed at higher ozonationtime

1 Introduction

Ozone is very strong oxidant and reacts with most of in-organic and organic pollutants It is used in water andwastewater treatment Ozone can react directly with a com-pound or trough reactions of hydroxyl radicals generatedin the ozone decomposition that then react with a com-pound It appears as an attractive treatment option due toits well-known capacity to oxidise aromatic compounds[1]

Benzothiazoles are toxic and poorly biodegradable pol-lutants Benzothiazole and its derivatives are widely usedas industrial chemicals in the leather and wood industriesas biocorrosion inhibitors in cooling systems ingredients inantifreezing agents for automobiles andmainly as vulcaniza-tion accelerators in rubber production They are often usedas herbicides and fungicides as anti-fungal drug as corrosioninhibitors in cooling water as slimicides in the paper andpulp industry and mainly as vulcanization accelerators inrubber production [2] Correspondingly these xenobiotic

compounds are widely distributed in the environment andhave been detected in industrial wastewater as well as in soilsestuarine sediments and superficial water [3] Benzothiazolecompounds have been detected in various environmentalcompartments in wastewaters soils estuarine sedimentsand superficial waters [2]

Benzothiazoles pose an environmental concern whenreleased into watercourses [4] These compounds inhibitmicroorganisms activity in conventional biological wastew-ater treatment systems and most of them are not readilybiodegradable [2 5] Moreover these compounds can beabsorbed into cell membranes leading to bioaccumulation[2] Unfortunately conventional biological wastewater treat-ment cannot effectively remove such contaminants sincethey are resistant to biodegradation [2]

2-Mercaptobenzothiazole (2-MBT) is widespread toxicand poorly biodegradable substance Moreover 2-MBTinhibits degradation of easily degradable organics and waste-water nitrification is inhibited at far lower concentrations [6]This compound is known to be toxic to aquatic organisms [7]

Hindawi Publishing Corporatione Scientific World JournalVolume 2014 Article ID 173010 7 pageshttpdxdoiorg1011552014173010

2 The Scientific World Journal

allergenic [8] and inducing tumours [9] Published datarelated to biodegradation of MBT are ambiguous Mainprizeet al [10] and Gaja and Knapp [11] reported that it maybe metabolised (although incompletely) by microorgan-isms which have been cultivated on other benzothiazolesChudoba et al [12] suggested MBT as a recalcitrant tobiodegradation The removal of MBT by activated sludge isspecified as a nonenzymatic process [11] It may also hamperwastewater treatment processes at concentrations higher than600120583molsdotLminus1 [13] Fiehn et al [6] have foundMBT to inhibitdegradation of easily degradable organics and the process ofnitrification was inhibited at a far lower concentration MBTis readily transformed to oxidation products by ozonationand wastewaters containing MBT should easily be detoxifiedusing ozone [6] Thus the development of efficient treat-mentpretreatment processes is required in order to eliminatetheir discharge into aquatic ecosystems

Puig et al [14] studied the ozonation of complex wast-ewater containing eight benzothiazole derivatives Theyachieved complete removal of 2-MBT but did not detectany benzothiazole derivative although there was no decreasein dissolved organic carbon (DOC) Fiehn et al [6] in-vestigated the ozonation of model wastewater containing600120583molminus1 of 2-MBT at pH 3 7 and 9 All tests werecarried out at a constant pH An aerobically treated tan-yard effluent was taken for a comparative ozonation of 2-MBT at pH 7 This wastewater sample was also spikedwith 600120583molminus1 of 2-MBT During ozonation maximumvalue of BT OBT and BTSO2 was measured after 6 125and 15 minutes and the process took over 55 minutes toremove all identified benzothiazole derivatives including2-MBT

No significant differences in the results of ozonationcarried out at the above pH values were observed Duringthe comparative ozonation with aerobically treated tan-yardeffluent spiked with the same amount of 2-MBT the sameintermediates were observed at the same time periods For BTthe same concentration was measured as during ozonation ofthe model wastewater OBT concentration reached 15 timesof the maximum concentration and BTSO2 was about halfcompared with the measured values in the ozonation of themodel wastewater Based on the total balance of dissolvedorganic carbon (DOC) however the authors stated that at theend of the process about 75 of the residual DOC remainedunidentified Therefore benzothiazole derivatives may stillenter the aqumineatic environment if the 2-MBT-containingeffluents are not biologically degraded with suitable bacterialsludge after the ozonation [6]

This work aims to study the kinetics of degradation andtransformation of 2-MBTwith ozone andmonitor the impactof ozonation products on activated sludge microorganismsThe aim is to find conditions for controlled ozonation 2-MBTin terms of its partial transformation complete mineraliza-tion and reduce toxicity to activated sludge microorganismsAnother objective is to determine the specific parametervalues for 2-MBT and verify the reproducibility of experi-mental measurements including analytical determination ofindicators 2-MBT COD and DOC

2 Materials and Methods

21 Characterisation of Wastewater The wastewater fromrubber industry contains more than 200mgsdotLminus1 of 2-MBT[1 15] Similar content of 2-MBT was measured in thewastewater produced from N-cyclohexyl-2-benzothiazol-sulfenamide [16 17] The concentration of MBT in modelwastewater varied from 661 to 1055mg Lminus1 for this set ofexperiments The chemical was provided by Merck (ge955purity)

22 Experimental Equipment and Procedures Ozonationexperiments were carried out in two glass columns 004mdiameter and 170m height The first column was filled withactivated sludge sample and the other one with solution ofpotassium iodide The reason was to specify the amount ofresidual ozone as well as to destroy residual ozone in theoutlet of ozonation column The effective volume of bothcolumns was 10 litre Schematic diagram of experimentalozonation apparatus is shown in Figure 1 The Lifetech ozonegenerator with the maximum ozone production 50 gsdothminus1was used Mixture of ozone and oxygen was introducedinto ozonation column at the bottom and it was mixedwith model wastewater sample through fine-bubble porousaeration element

The system was operated in batch mode with regardto wastewater samples Wastewater samples were added toozonation column at the beginning of trials Continuousflows of oxygen at 20 Lsdothminus1 (119879 = 220∘C 119901 = 99 800 Pa) wereapplied for generation of ozone Ozonation trials were carriedout at performance of ozone generator 70 of the powermaximum Ozonation times were from 20 to 60 minutes Atselected time intervals samples were collected and analyzedfor indicators COD and identified benzothiazoles (BT 2-MBT OBT)

The outlet gas mixture was conducted into second bubblecolumn through a fine-bubble porous distribution elementThe dimensions of the column were identical to ozonationcolumn The column was filled with a solution of potassiumiodide The excess ozone destruction was carried out in thiscolumn Likewise as the ozonation column the effectivevolume of the bubble column was 10 L The concentrationof ozone in gas phase was measured using Life ODU 200Analyzer

The influence of raw and ozonatedwastewater samples onactivated sludgemicroorganisms activity was evaluated basedon results obtained by respirometric measurements Oxygenuptake rates by microorganisms of activated sludge whichwas cultivated in semicontinuous laboratory scale activatedsludge process were measured [18]

23 Analytical Procedures 2-MBT and other BT derivativeswere analysed using Hewlett Packard Liquid Chromatog-raphy series II 1090 with DAD detector Direct injectionmethod was applied using linear gradient of RP-HPLC withUV-DAD detector on the column C18 (Merck) TOC wasmeasured with analyzer Shimadzu TOC-VCPHCPN (Japan)Analytical control of model wastewater during the treatment

The Scientific World Journal 3

1 2

3 3

4

5

6 67 7

8

9

10

11

Figure 1 Schematic diagram of experimental apparatus 1 ozona-tion column 2 destruction of residual ozone 3 oxygen supply 4ozone generator 5 mixture of oxygen and ozone 6 ozone distri-bution 7 sampling 8 residual gas outlet 9 separation of moisture10 glass fiber filter 11 UV analyzer of ozone content in gas phase

procedures included also COD (chemical oxygen demand)determination [19 20]

24 Mathematical Treatment of Experimental Data Experi-mental data were fitted by zero (see (1) first see (2) and thensee (3)) order reaction kinetic models For a batch reactionsystem under the assumption of a constant reaction volumethe following relationships are obtained

COD119905

= COD0

minus 1198960

119905 (1)

COD119905

= COD0

exp (minus1198961

119905) (2)

COD119905

=COD0

(1 + COD0

1198962

119905) (3)

where COD119905

(gmminus3) denotes the value of COD in wastew-ater in time 119905 COD

0

(gmminus3) the initial value of COD inwastewater and 119896

0

(gmminus3 hminus1) 1198961

hminus1 1198962

(gminus1m3 hminus1) therate constants for the kinetics of zero the first and the secondorder respectively

The parameters of the applied kinetic models were calcu-lated by the grid search optimization procedureThe residualsum of squares (1198782

119903

) between the observed values and thevalues given by the model divided by its number of degreesof freedom ] (the number of observations less the number ofparameters estimated) was used as the objective function

25 Partial Oxidation and Mineralization To evaluate theoxidized and mineralized portions of synthetic sewage pol-lution during ozonation and identification of the highest

efficiency of partial oxidation we used following equation[21 22]

120572CODoxi = 1 minusCOD119905

COD0

(4)

120572CODminer = 1 minusDOC119905

DOC0

(5)

120572CODpartoxi = 120572CODoxi minus 120572CODminer (6)

120583CODpartoxi =120572CODpartoxi

120572CODoxi (7)

where 120572CODoxi is the proportion of oxidized organic pol-lutants expressed as COD 120572CODminer is the proportionof oxidized COD which was completely mineralized and120572CODpartoxi is only partially oxidized COD of the syntheticwastewater during the process The effectiveness of partialoxidation 120583CODpartoxi is proportional to the ratio of decreasein COD due to the transformation of substances intermedi-ates (120572CODpartoxi) and the decrease of oxidized COD of thesynthetic wastewater (120572CODoxi) in the process

26 Impact onActivated SludgeMicroorganisms Respiromet-ricmeasurements [22] were conducted to assess the impact ofozonation products on activated sludge microorganismsThemeasurement results have been processed using the followingMonod equation (see (8) [22] and for Haldan equation see(9)) [23 24]

119903119883

= 119903119883max119878

119870119878

+ 119878 (8)

119903119883

= 119903119883max

119878

119870119878

+ 119878 + (1198782119870119868

) (9)

where 119903119883

and 119903119883max are respectively the specific respiration

rate andmaximum specific respiration rate [mgsdotgminus1sdothminus1] and119878119870119878

and119870119868

are the substrate concentration half-saturationconstant and inhibition constant [mgsdotLminus1] The values ofkinetic parameters in (8) and (9) were determined using thegrid search method

27 Mean Oxidation State of Organic Carbon Wastewatertreatment processes try to convert the environmentally harm-ful carbon species into a less problematic one often CO

2

A suitable method to monitor the fate and oxidation stateof the total organically bound carbon is the mean oxidationnumber of organic carbon (MOC) as proposed by Stum andMorgan [25] and extended byVogel et al [26] Forwastewatercontaining more pollutants COD and TOC values can becombined to give a MOC estimate according to (10)

MOC = 4 minus 15CODoTOC (10)

where CODo is the organic COD and TOC is total organiccarbon


1200

900

600

300

00 10 20 30 40 50 60

Time (min)

MBT

(mgmiddot

Lminus1)

Figure 2 Dependencies ofmeasured (⧫) and calculated (mdash) 2-MBTvalues on ozonation time

500

450

400

350

3000 10 20 30 40 50 60

Time (min)

DO

C (m

gmiddotLminus

1)

Figure 3 Dependencies of measured (⧫) and calculated (mdash) DOCvalues on ozonation time

3 Results and Discussion

Three independent series of measurements with reactiontimes of 20ndash60 minutes were performed Thus overall 23experimental values were used for eachmonitored variable toevaluate the kinetics The pH values varied in the range from123 to 79 during ozonation experiments

The time dependencies ofmeasured and calculated valuesof 2-MBT COD and DOC are presented in Figures 2 to4 The boundaries of the 95 confidence intervals whichwere calculated on the basis of statistical analysis of repeatedmeasurements are also marked in these figures

There can be seen two regions in Figure 2 During thefirst region with duration of approximately 15 minutes theconversion of 2-MBT to BT and other BT-derivatives occursaccording to mechanisms proposed by Fiehn et al [6] andresults published by Derco et al [17 27] Kinetic datameasured for this region were fitted very well by zero-orderkinetics The trend of 2-MBT transformation is very similarwith the trends of DOC and COD degradation kinetics(Figures 3 and 4) However from the values of zero-orderkinetic constants (Table 1) it follows that transformation anddegradation processes occur simultaneously with obviouslyhigher transformation rate of 2-MBT in comparison todegradation rates of DOC and COD Relatively very low2-MBT concentration values and consequently also 2-MBTdecline rates are obvious for the second stage of 2-MBTdependence on ozonation time

2500

2000

1500

1000

500

00 10 20 30 40 50 60

Time (min)

COD

(mgmiddot

Lminus1)

Figure 4 Dependencies of measured (⧫) and calculated (mdash) CODvalues on ozonation time

Table 1 The values of the kinetic parameters and statistical charac-teristics

Variable 119873 119896119899

Dimension of 119896119899

1199032

119883119884

1198782

119903

MBT 0 5559 mgsdotLminus1 minminus1 09888 968DOC 0 177 mgsdotLminus1 minminus1 07590 248COD 0 1921 mgsdotLminus1 minminus1 09175 8143

FromFigure 2 it is evident that during the first 20minutesof the process performance almost complete elimination of 2-MBT in the model wastewater occurred However after thisreaction time 938 of the original value of DOC (Figure 3)and 755 of the original value of COD (Figure 4) remainedin the model wastewater

It is obvious that 2-MBT was only partially oxidizedand majority was transformed to intermediates and prod-ucts respectively simple benzothiazole derivatives whichremained in the treated model wastewater During the next40 minutes of ozonation performance DOC value declinedto 685 and COD decreased to 376 of the initial values

Calculated values in Figures 2 to 4 correspond to the bestdescriptions of the experimental values using conventionalkinetic models The values of kinetic parameters and statis-tical characteristics (correlation coefficient and residual dis-persion) are for individual indicators of pollution and kineticmodels with the best description of the experimental valuesgiven in Table 1 The best description of the experimentalvalues of DOC and COD was achieved using zero kinetics(Table 1) Removal of 2-MBT corresponds to the first kineticmodel (Table 1)

From dependencies pictured in Figures 2 to 4 from thevalues of the statistical characteristics given in Table 1 andit can be seen that the largest residual dispersion betweenmeasured and calculated values shows time dependence of 2-MBT values In Table 2 there are given the results of statisticaltreatment of repeated experiments which were carried outto verify the reproducibility of the results achieved Theremovals of studied pollution indicators depending on reac-tion time are graphically illustrated in Figures 2 to 4

The results in Table 2 show the largest variability of CODvalues measured after 15 minutes of ozonation In the caseof 2-MBT the value of 95 confidence interval did notexceed 3 of the average 2-MBT value after 15 minutes ofozonationThe accuracy of repeated measurements for DOC


Table 2 Results of statistical processing achieved removal efficiencies in repeated experiments aimed to verify the reproducibility of results

Reaction time 15min 30min 60min

Variable Pollutant averageefficiency

95 confidenceinterval

Pollutant averageefficiency




2-MBT 972 29 mdash mdash mdash mdashDOC 46 10 155 13 365 08COD 271 96 413 23 658 18

0 10 20 30 40 50 60

Time (min)

20

15

10

5

0

1200

800

400

0

BT O

BT (m

gmiddotLminus

1)

2-M

BT (m

gmiddotLminus

1)

Figure 5 Dependence of concentrations (e) 2-MBT (⧫) BT and (◼)OBT on ozonation time

and COD pollution indicators increases at longer reactiontimes The limit values for 95 confidence intervals for theseindicators of pollution did not exceed 3of the average valuesafter 60 minutes of ozonation It can be concluded that thereproducibility of the results of repeated ozonation assaysincluding sampling and analysis was very good

From the statistical analysis of repeated measurements ofinitial values the following specific values for 2-MBT havebeen obtained COD2-MBT = 2008 gsdotgminus1 (limit value for confidence interval is plusmn0145 gsdotgminus1) and DOC2-MBT =0463 gsdotgminus1 (limit value for 95 confidence interval isplusmn0032 gsdotgminus1)

In Figure 5 are in addition to 2-MBT shown also timedependencies of identified intermediates (BT and OBT) of2-MBT transformation with ozone It can be seen fromthese dependencies that to a maximum decrease of 2-MBTconcentration correspond maximum values of the degra-dation products After removaltransformation of 2-MBTthe content of these derivatives gradually decreases to zeroconcentration

Taking into account the above values of DOC and CODit is obvious that in the sample of ozonated model wastewaterthere are accumulated so far unidentified reaction products

Figure 6 shows the dependencies of oxidation miner-alization partial oxidation portions and the effectivenessof partial oxidation (see (4)ndash(7)) on ozonation time during60 minutes oxidation assay with the model sample of 2-MBT Of these dependencies it follows that time courses ofthe portions of COD oxidation (see (4) (120572CODoxi)) min-eralization (see (5) (120572CODmin)) and partial oxidation (see(6) (120572CODpartoxi)) exhibit an approximately linear depen-dence on the reaction time High partial oxidation efficiency

0 10 20 30 40 50 60

Time (min)

10

08

06

04

02

00

120572CO

D120583

COD

(mdash)

Figure 6 Dependencies of COD portions on ozonation time (e)120572CODoxi (998771) 120572CODmin (⧫) 120572CODparcoxi and (◼) 120583CODpartoxi

(see (7) 120583CODpartoxi about 73) corresponds to the reactiontime of 20 minutes Due to the fact that this responsetime corresponds to a relatively low proportion of 120572CODoxi(193) of which the portion of 120572CODpartoxi is 141 theseparameters cannot be considered to be effective in termsof controlled oxidation in order to increase the portion ofpartially oxidized substances with higher oxygen contentprior to completing mineralization processes by economi-cally the most convenient biological wastewater treatmentprocesses From this aspect an effective reaction time is 60minutes (120572CODoxi = 623) while the proportion of partiallymineralized 120572CODpartoxi is 510

This is confirmed by the time dependencies of specificconsumption of ozone related to unit mass of COD reduction(ΔO3

ΔCOD) and the mean oxidation number of organiccarbon MOC [22 26] which are shown in Figure 7

In Figure 8 the time courses of ozone concentrationsare shown measured under the same conditions at theinlet and outlet of the ozonation column filled both withdemineralized water and themodel wastewater It can be seenthat during approximately 40 minutes of ozonation of themodel wastewater nearly all supplied ozone was transferredto the liquid phase After this time ozone concentration in thegas phase gradually increased indicating a less consumptionof ozone for oxidation of created intermediates and productsThis indicates also the reaction conditions at which theozonation process is not limited by the amount of ozonesupplied Based on ozone balance can be stated that 986of O3

was transferred to liquid phaseThe results of respirometric measurements to assess the

impact of products generated during the ozonation of themodel wastewater containing 2-MBT on the activity of


Table 3 Kinetic parameters and correlation coefficients

Kineticequation

119903119909119898

(mgsdotgndash1sdothndash1)119870119878

(mgsdotdmndash3)

119870119868

(mgsdotdmndash3)1199032

119909119910

(mdash)Monod 116 702 mdash 09767Haldane 181 3344 441 09275

0 10 20 30 40 50 60

Time (min)

30

25

20

15

10

05

00

10

00

minus10

minus20

minus30

ΔO3Δ

COD

(gmiddotgminus1)

MO

C (mdash

)

Figure 7 Dependencies ofΔO3

ΔCOD (◼) andMOC (998771) values onozonation time

the activated sludge microorganisms are shown in Figure 9Respirometric measurements were performed with activatedsludge which was cultivated in semicontinuous lab-scalemodel of activated sludge process (glucose peptone sludgeage 10 days) The first ozonation of the model wastewaterlasted 15 minutes From the dependence of specific oxy-gen uptake rate on COD value it is clear that at higherCOD values there exists inhibition of respiratory activ-ity of activated sludge microorganisms For a descriptionof this dependence Haldane kinetic model was used (see(9)) The second curve in Figure 9 corresponds to themeasurement of respiratory activity after the addition ofozonized model wastewater samples containing 2-MBT after40 minutes ozonation For a description of this dependenceMonod kinetic model was used (see (8)) Parameter valuesof Monod and Haldane equations and correlation coeffi-cient values are given in Table 3 The maximum values ofspecific respiration rate obtained for ozonized samples ofsynthetic sewage of 2-MBT are significantly smaller than forreference sample glucose (119903

119909119898

= 995mgsdotgminus1sdothminus1) On theother hand respirometric measurements indicate that theinhibitory effect of a model substance and its degradationproducts to ozone can be reduced by a longer duration of theozonation

4 Conclusions

From the evaluation of the results of repeated measurementsit can be concluded that the reproducibility of treatmentassays including sampling and analysis was very good Thebest description of the experimental 2-MBT COD and DOCdata was obtained by using zero kinetic model Almostcomplete removal of 2-MBT was observed after 20 minutes

0 10 20 30 40 50 60

Time (min)

120

100

80

60

40

20

0

Con

cent

ratio

n of

O3

(gO3middotN

mminus3)

Figure 8 Time dependencies of O3

concentration in the gaseousphase mdash Input e Output 2-MBT and ◼ Output H

2

O

100

80

60

40

20

000 50 100 150 200 250

COD (mgmiddotLminus1)

r xm

(mgmiddot

gminus1middoth

minus1)

Figure 9 Dependencies of SOUR with the activated sludgemicroorganisms on COD values during respirometric measure-ments performed with ozonized model wastewater containing 2-MBT during 15 minutes (e) experimental (- - -) calculated andduring 40 minutes (◼) experimental (mdash) calculated

of ozonation However in the reaction mixture there were938 ofDOC and 755 of CODof the original values at thattime These results confirm that at the first stage of 2-MBToxidation with ozone prevails its transformation into otherorganic materials Benzothiazole derivatives OBT and BTwere identified as emerging intermediates during decomposi-tion of 2-MBT with ozone Results of mass balance of carbonindicate that also other organic compounds are created Thereaction time of 60minuteswith 510proportion of partiallyoxidizedCODwas found to be effective in terms of controlledoxidation in order to increase the amount of partially oxi-dized compounds From the balance of ozone amounts at theinlet and outlet of the reactor it follows that 986 of suppliedozone during the ozonation was transferred from gas intoliquid phaseThe results of respirometricmeasurements showthat the specific respiration rate of the model wastewatersample ozonated for 40 minutes was significantly highercompared to the sample after 15 minutes of ozonation Thiscan be explained by the fact that the sample ozonated for15 minutes contained more less ozonated substances whichare toxic on microorganisms of activated sludge at higherconcentrations reducing their respiration activity and havingan inhibitory effect


Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the Slovak Research and Devel-opment Agency under contract no APVV-0656-12 Theauthors wish to thank also the support of the VEGA Grant1073412

References

[1] H Valdes C A Zaror andM Jekel ldquoKinetic study of reactionsbetween ozone and benzothiazole in waterrdquo Water Science andTechnology vol 48 no 11-12 pp 505ndash510 2003

[2] H de Wewer and H Verachter ldquoBiodegradation and toxicity ofbenzothiazolesrdquo Water Research vol 31 no 11 pp 2673ndash26841997

[3] H Valdes and C A Zaror ldquoOzonation of benzothiazolesaturated-activated carbons influence of carbon chemical sur-face propertiesrdquo Journal of Hazardous Materials vol 137 no 2pp 1042ndash1048 2006

[4] H Valdes F A Murillo J A Manoli and C A ZarorldquoHeterogeneous catalytic ozonation of benzothiazole aqueoussolution promoted by volcanic sandrdquo Journal of HazardousMaterials vol 153 no 3 pp 1036ndash1042 2008

[5] H De Wever S Weiss T Reemtsma et al ldquoComparison ofsulfonated and other micropollutants removal in membranebioreactor and conventional wastewater treatmentrdquo WaterResearch vol 41 no 4 pp 935ndash945 2007

[6] O Fiehn G Wegener J Jochimsen and M Jekel ldquoAnalysisof the ozonation of 2-mercaptobenzothiazole in water andtannery wastewater using sum parameters liquid- and gaschromatography and capillary electrophoresisrdquoWater Researchvol 32 no 4 pp 1075ndash1084 1998

[7] Y Yoshioka and Y Ose ldquoA quantitative structure-activityrelationship study and ecotoxicological risk quotient for theprotection from chemical pollutionrdquo Environmental Toxicologyand Water Quality vol 8 no 1 pp 87ndash101 1993

[8] J H Jung J L McLaughlin and J D Guin ldquoIsolation viaactivity-directed fractionation of mercaptobenzothiazole anddibenzothiazyl disulfide as 2 allergens responsible for tennisshoe dermatitisrdquo Contact Dermatitis vol 19 no 4 pp 254ndash2591988

[9] L Swirsky Gold T H Slone B R Stern and L BernsteinldquoComparison of target organs of carcinogenicity for mutagenicand non-mutagenic chemicalsrdquoMutation Research vol 286 no1 pp 75ndash100 1993

[10] J Mainprize J S Knapp and A G Callely ldquoThe fate ofbenzothiazole 2 sulphonic acid in biologically treated industrialeffluentsrdquo Journal of Applied Bacteriology vol 40 no 3 pp 285ndash291 1976

[11] M A Gaja and J S Knapp ldquoRemoval of 2-mercaptoben-zothiazole by activated sludge a cautionary noterdquo Water Re-search vol 32 no 12 pp 3786ndash3789 1998

[12] J Chudoba F Tucek and K Zies ldquoBiochemischer Abbau vonBenzothiazolderivatenrdquo Acta Hydrochim vol 5 pp 499ndash5011977

[13] H De Wever K De Moor and H Verachtert ldquoToxicity of 2-mercaptobenzothiazole towards bacterial growth and respira-tionrdquoApplied Microbiology and Biotechnology vol 42 no 4 pp631ndash635 1994

[14] A Puig P Ormad P Roche J Sarasa E Gimeno and J LOvelleiro ldquoWastewater from themanufacture of rubber vulcan-ization accelerators characterization downstream monitoringand chemical treatmentrdquo Journal of Chromatography A vol 733no 1-2 pp 511ndash522 1996

[15] M H Habibi S Tangestaninejad and B Yadollahi ldquoPhotocat-alyticmineralisation ofmercaptans as environmental pollutantsin aquatic system using TiO

2

suspensionrdquo Applied Catalysis Bvol 33 no 1 pp 57ndash63 2001

[16] J Derco A Gulyasova M Kralik and L Mrafkova ldquoTreatmentof an industrial wastewater by ozonationrdquo Petroleum and Coalvol 42 no 2 pp 92ndash97 2001

[17] J Derco M Melicher A Kassai J Dudas and M ValickovaldquoRemoval of Benzothiazoles by ozone pretreatmentrdquo Environ-mental Engineering Science vol 28 no 11 pp 781ndash785 2011

[18] H Spanjer P A Vanrolleghem G Olson and P L DoldldquoRespirometry in control of the activated sludge processprinciplesrdquo IAWQ Scientific and Technical Report 7 J WArrowsmith Bristol UK 2000

[19] ISO 6060 Water QualitymdashDetermination of Chemical OxygenDemand International Organisation for Standardisation Gen-eve Switzerland 1989

[20] A E Greenberg L S Clesceri and A Eaton Eds StandardMethods for the Examination of Water and Wastewater Amer-ican Public Health Association Washington DC USA 22ndedition 2005

[21] J C Jochimsen andM R Jekel ldquoPartial oxidation effects duringthe combined oxidative and biological treatment of separatedstreams of tannery wastewaterrdquo Water Science and Technologyvol 35 no 4 pp 337ndash345 1997

[22] D Mantzavinos E Lauer M Sahibzada A G Livingston andI S Metcalfe ldquoAssessment of partial treatment of polyethyleneglycol wastewaters bywet air oxidationrdquoWater Research vol 34no 5 pp 1620ndash1628 2000

[23] J R Sonnad and C T Goudar ldquoSolution of the Haldaneequation for substrate inhibition enzyme kinetics using thedecomposition methodrdquo Mathematical and Computer Mod-elling vol 40 no 5-6 pp 573ndash582 2004

[24] G Tziotzios G Lyberatos S Pavlou and D V VayenasldquoModelling of biological phenol removal in draw-fill reactorsusing suspended and attached growth olive pulp bacteriardquoInternational Biodeterioration and Biodegradation vol 61 no2 pp 142ndash150 2008

[25] W Stum and J J Morgan Aquatic Chemistry John Wiley ampSons New York NY USA 2nd edition 1981

[26] F Vogel J Harf A Hug and P R Von Rohr ldquoThe meanoxidation number of carbon (MOC )mdasha useful concept fordescribing oxidation processesrdquoWater Research vol 34 no 10pp 2689ndash2702 2000

[27] J Derco M Melicher and A Kassai ldquoRemoval of selectedbenzothiazols with ozonerdquo in Municipal and Industrial WasteDisposal X-Y Yu Ed vol 26 p 239 INTECH Rijeka Croatia2012

International Journal of

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allergenic [8] and inducing tumours [9] Published datarelated to biodegradation of MBT are ambiguous Mainprizeet al [10] and Gaja and Knapp [11] reported that it maybe metabolised (although incompletely) by microorgan-isms which have been cultivated on other benzothiazolesChudoba et al [12] suggested MBT as a recalcitrant tobiodegradation The removal of MBT by activated sludge isspecified as a nonenzymatic process [11] It may also hamperwastewater treatment processes at concentrations higher than600120583molsdotLminus1 [13] Fiehn et al [6] have foundMBT to inhibitdegradation of easily degradable organics and the process ofnitrification was inhibited at a far lower concentration MBTis readily transformed to oxidation products by ozonationand wastewaters containing MBT should easily be detoxifiedusing ozone [6] Thus the development of efficient treat-mentpretreatment processes is required in order to eliminatetheir discharge into aquatic ecosystems

Puig et al [14] studied the ozonation of complex wast-ewater containing eight benzothiazole derivatives Theyachieved complete removal of 2-MBT but did not detectany benzothiazole derivative although there was no decreasein dissolved organic carbon (DOC) Fiehn et al [6] in-vestigated the ozonation of model wastewater containing600120583molminus1 of 2-MBT at pH 3 7 and 9 All tests werecarried out at a constant pH An aerobically treated tan-yard effluent was taken for a comparative ozonation of 2-MBT at pH 7 This wastewater sample was also spikedwith 600120583molminus1 of 2-MBT During ozonation maximumvalue of BT OBT and BTSO2 was measured after 6 125and 15 minutes and the process took over 55 minutes toremove all identified benzothiazole derivatives including2-MBT

No significant differences in the results of ozonationcarried out at the above pH values were observed Duringthe comparative ozonation with aerobically treated tan-yardeffluent spiked with the same amount of 2-MBT the sameintermediates were observed at the same time periods For BTthe same concentration was measured as during ozonation ofthe model wastewater OBT concentration reached 15 timesof the maximum concentration and BTSO2 was about halfcompared with the measured values in the ozonation of themodel wastewater Based on the total balance of dissolvedorganic carbon (DOC) however the authors stated that at theend of the process about 75 of the residual DOC remainedunidentified Therefore benzothiazole derivatives may stillenter the aqumineatic environment if the 2-MBT-containingeffluents are not biologically degraded with suitable bacterialsludge after the ozonation [6]

This work aims to study the kinetics of degradation andtransformation of 2-MBTwith ozone andmonitor the impactof ozonation products on activated sludge microorganismsThe aim is to find conditions for controlled ozonation 2-MBTin terms of its partial transformation complete mineraliza-tion and reduce toxicity to activated sludge microorganismsAnother objective is to determine the specific parametervalues for 2-MBT and verify the reproducibility of experi-mental measurements including analytical determination ofindicators 2-MBT COD and DOC

2 Materials and Methods

21 Characterisation of Wastewater The wastewater fromrubber industry contains more than 200mgsdotLminus1 of 2-MBT[1 15] Similar content of 2-MBT was measured in thewastewater produced from N-cyclohexyl-2-benzothiazol-sulfenamide [16 17] The concentration of MBT in modelwastewater varied from 661 to 1055mg Lminus1 for this set ofexperiments The chemical was provided by Merck (ge955purity)

22 Experimental Equipment and Procedures Ozonationexperiments were carried out in two glass columns 004mdiameter and 170m height The first column was filled withactivated sludge sample and the other one with solution ofpotassium iodide The reason was to specify the amount ofresidual ozone as well as to destroy residual ozone in theoutlet of ozonation column The effective volume of bothcolumns was 10 litre Schematic diagram of experimentalozonation apparatus is shown in Figure 1 The Lifetech ozonegenerator with the maximum ozone production 50 gsdothminus1was used Mixture of ozone and oxygen was introducedinto ozonation column at the bottom and it was mixedwith model wastewater sample through fine-bubble porousaeration element

The system was operated in batch mode with regardto wastewater samples Wastewater samples were added toozonation column at the beginning of trials Continuousflows of oxygen at 20 Lsdothminus1 (119879 = 220∘C 119901 = 99 800 Pa) wereapplied for generation of ozone Ozonation trials were carriedout at performance of ozone generator 70 of the powermaximum Ozonation times were from 20 to 60 minutes Atselected time intervals samples were collected and analyzedfor indicators COD and identified benzothiazoles (BT 2-MBT OBT)

The outlet gas mixture was conducted into second bubblecolumn through a fine-bubble porous distribution elementThe dimensions of the column were identical to ozonationcolumn The column was filled with a solution of potassiumiodide The excess ozone destruction was carried out in thiscolumn Likewise as the ozonation column the effectivevolume of the bubble column was 10 L The concentrationof ozone in gas phase was measured using Life ODU 200Analyzer

The influence of raw and ozonatedwastewater samples onactivated sludgemicroorganisms activity was evaluated basedon results obtained by respirometric measurements Oxygenuptake rates by microorganisms of activated sludge whichwas cultivated in semicontinuous laboratory scale activatedsludge process were measured [18]

23 Analytical Procedures 2-MBT and other BT derivativeswere analysed using Hewlett Packard Liquid Chromatog-raphy series II 1090 with DAD detector Direct injectionmethod was applied using linear gradient of RP-HPLC withUV-DAD detector on the column C18 (Merck) TOC wasmeasured with analyzer Shimadzu TOC-VCPHCPN (Japan)Analytical control of model wastewater during the treatment


1 2

3 3

4

5

6 67 7

8

9

10

11




COD119905

= COD0

minus 1198960

119905 (1)

COD119905

= COD0

exp (minus1198961

119905) (2)

COD119905

=COD0

(1 + COD0

1198962

119905) (3)

where COD119905


0


0


hminus1 1198962



119903





COD0

(4)


DOC0

(5)



120572CODoxi (7)



119903119883

= 119903119883max119878

119870119878

+ 119878 (8)

119903119883

= 119903119883max

119878

119870119878

+ 119878 + (1198782119870119868

) (9)

where 119903119883



and119870119868



2





1200

900

600

300

00 10 20 30 40 50 60

Time (min)

MBT

(mgmiddot

Lminus1)


500

450

400

350

3000 10 20 30 40 50 60

Time (min)

DO

C (m

gmiddotLminus

1)






2500

2000

1500

1000

500

00 10 20 30 40 50 60

Time (min)

COD

(mgmiddot

Lminus1)



Variable 119873 119896119899


1199032

119883119884

1198782

119903

















0 10 20 30 40 50 60

Time (min)

20

15

10

5

0

1200

800

400

0

BT O

BT (m

gmiddotLminus

1)

2-M

BT (m

gmiddotLminus

1)







0 10 20 30 40 50 60

Time (min)

10

08

06

04

02

00

120572CO

D120583

COD

(mdash)










Kineticequation

119903119909119898


(mgsdotdmndash3)

119870119868


119909119910


0 10 20 30 40 50 60

Time (min)

30

25

20

15

10

05

00

10

00

minus10

minus20

minus30

ΔO3Δ

COD

(gmiddotgminus1)

MO

C (mdash

)




119909119898


4 Conclusions


0 10 20 30 40 50 60

Time (min)

120

100

80

60

40

20

0

Con

cent

ratio

n of

O3

(gO3middotN

mminus3)



2

O

100

80

60

40

20

000 50 100 150 200 250


r xm

(mgmiddot

gminus1middoth

minus1)






Acknowledgments


References
















2
















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










1 2

3 3

4

5

6 67 7

8

9

10

11




COD119905

= COD0

minus 1198960

119905 (1)

COD119905

= COD0

exp (minus1198961

119905) (2)

COD119905

=COD0

(1 + COD0

1198962

119905) (3)

where COD119905


0


0


hminus1 1198962



119903





COD0

(4)


DOC0

(5)



120572CODoxi (7)



119903119883

= 119903119883max119878

119870119878

+ 119878 (8)

119903119883

= 119903119883max

119878

119870119878

+ 119878 + (1198782119870119868

) (9)

where 119903119883



and119870119868



2





1200

900

600

300

00 10 20 30 40 50 60

Time (min)

MBT

(mgmiddot

Lminus1)


500

450

400

350

3000 10 20 30 40 50 60

Time (min)

DO

C (m

gmiddotLminus

1)






2500

2000

1500

1000

500

00 10 20 30 40 50 60

Time (min)

COD

(mgmiddot

Lminus1)



Variable 119873 119896119899


1199032

119883119884

1198782

119903

















0 10 20 30 40 50 60

Time (min)

20

15

10

5

0

1200

800

400

0

BT O

BT (m

gmiddotLminus

1)

2-M

BT (m

gmiddotLminus

1)







0 10 20 30 40 50 60

Time (min)

10

08

06

04

02

00

120572CO

D120583

COD

(mdash)










Kineticequation

119903119909119898


(mgsdotdmndash3)

119870119868


119909119910


0 10 20 30 40 50 60

Time (min)

30

25

20

15

10

05

00

10

00

minus10

minus20

minus30

ΔO3Δ

COD

(gmiddotgminus1)

MO

C (mdash

)




119909119898


4 Conclusions


0 10 20 30 40 50 60

Time (min)

120

100

80

60

40

20

0

Con

cent

ratio

n of

O3

(gO3middotN

mminus3)



2

O

100

80

60

40

20

000 50 100 150 200 250


r xm

(mgmiddot

gminus1middoth

minus1)






Acknowledgments


References
















2
















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










1200

900

600

300

00 10 20 30 40 50 60

Time (min)

MBT

(mgmiddot

Lminus1)


500

450

400

350

3000 10 20 30 40 50 60

Time (min)

DO

C (m

gmiddotLminus

1)






2500

2000

1500

1000

500

00 10 20 30 40 50 60

Time (min)

COD

(mgmiddot

Lminus1)



Variable 119873 119896119899


1199032

119883119884

1198782

119903

















0 10 20 30 40 50 60

Time (min)

20

15

10

5

0

1200

800

400

0

BT O

BT (m

gmiddotLminus

1)

2-M

BT (m

gmiddotLminus

1)







0 10 20 30 40 50 60

Time (min)

10

08

06

04

02

00

120572CO

D120583

COD

(mdash)










Kineticequation

119903119909119898


(mgsdotdmndash3)

119870119868


119909119910


0 10 20 30 40 50 60

Time (min)

30

25

20

15

10

05

00

10

00

minus10

minus20

minus30

ΔO3Δ

COD

(gmiddotgminus1)

MO

C (mdash

)




119909119898


4 Conclusions


0 10 20 30 40 50 60

Time (min)

120

100

80

60

40

20

0

Con

cent

ratio

n of

O3

(gO3middotN

mminus3)



2

O

100

80

60

40

20

000 50 100 150 200 250


r xm

(mgmiddot

gminus1middoth

minus1)






Acknowledgments


References
















2
















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation



















0 10 20 30 40 50 60

Time (min)

20

15

10

5

0

1200

800

400

0

BT O

BT (m

gmiddotLminus

1)

2-M

BT (m

gmiddotLminus

1)







0 10 20 30 40 50 60

Time (min)

10

08

06

04

02

00

120572CO

D120583

COD

(mdash)










Kineticequation

119903119909119898


(mgsdotdmndash3)

119870119868


119909119910


0 10 20 30 40 50 60

Time (min)

30

25

20

15

10

05

00

10

00

minus10

minus20

minus30

ΔO3Δ

COD

(gmiddotgminus1)

MO

C (mdash

)




119909119898


4 Conclusions


0 10 20 30 40 50 60

Time (min)

120

100

80

60

40

20

0

Con

cent

ratio

n of

O3

(gO3middotN

mminus3)



2

O

100

80

60

40

20

000 50 100 150 200 250


r xm

(mgmiddot

gminus1middoth

minus1)






Acknowledgments


References
















2
















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











Kineticequation

119903119909119898


(mgsdotdmndash3)

119870119868


119909119910


0 10 20 30 40 50 60

Time (min)

30

25

20

15

10

05

00

10

00

minus10

minus20

minus30

ΔO3Δ

COD

(gmiddotgminus1)

MO

C (mdash

)




119909119898


4 Conclusions


0 10 20 30 40 50 60

Time (min)

120

100

80

60

40

20

0

Con

cent

ratio

n of

O3

(gO3middotN

mminus3)



2

O

100

80

60

40

20

000 50 100 150 200 250


r xm

(mgmiddot

gminus1middoth

minus1)






Acknowledgments


References
















2
















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation












Acknowledgments


References
















2
















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









research article removal of the 2-mercaptobenotiazole from...

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