extant biodegradation testing with linear alkylbenzene ...tge/wc0054p3.pdf · extant biodegradation...

Extant Biodegradation Testing With Linear Alkylbenzene Sulfonate in Laboratory and Field Activated Sludge Systems

Xiaohong Huang1, Timothy G. Ellis1, and Sandra K. Kaiser2

1 Dept. of Civil and Construction Engineering, Iowa State University, Ames, IA 50011-32322 The Procter and Gamble Company, Cincinnati, OH 45253-8707

ABSTRACT

Two 1-L porous pot (65 µ stainless steel mesh) reactors were fed synthetic wastewaterwith a COD of 200 mg/L including 2 mg/L linear alkyl benzene sulfonate (LAS) to evaluate theinfluence of specific operating conditions (i.e, hydraulic retention time, HRT, and solidsretention time, SRT) on the measured rate of LAS biodegradation. The reactors were operated inparallel under a constant SRT of 10 d, and HRTs of 2, 4, 6, and 12 h. Subsequently, the reactorswere operated under a constant HRT of 6 h, and SRTs of 3, 6, 10, and 15 d. The biodegradationresponses of LAS were measured using a respirometric method, and the extant kinetic parameterswere evaluated using the Monod model. The extant kinetic parameters obtained from theseexperiments suggest that the HRT had little impact on the measured kinetic parameters (µ̂ = 0.14± 0.06 h-1, KS = 0.4 ± 0.3 mg COD/L, and Y = 0.67 ± 0.02 mg biomass COD formed/mg LASCOD utilized) at a constant SRT of 10 d. The SRT had a more noticeable effect on the measuredbiodegradation kinetics (e.g., Y increased from 0.50 ± 0.08 to 0.66 ± 0.05 mg/mg when the SRTincreased from 3 to 10 d at a constant HRT of 6 h). Extant kinetics for LAS biodegradation weremeasured in the field at two activated sludge wastewater treatment plants operated at differentconditions. The field results were similar to the results from laboratory systems operated tosimulate the field conditions (µ̂ values ranged from 0.02 - 0.05 h-1, KS values ranged from 0.11 -0.39 mg COD/L, and yield values ranged from 0.46 - 0.50 mg biomass COD formed/mg LASCOD utilized). The week to week variability in measured LAS kinetic parameters was greaterwith the field samples than with the laboratory samples, possibly due to the non-steady statenature of the treatment plants. The long term variability in the field kinetic parameters wascomparable to the laboratory variability. These results confirm the efficacy of the extantrespirometric technique to measure biodegradation rates of surfactants in laboratory and fieldsystems operated at a range of HRT and SRT conditions.

Keywords: Linear alkyl benzene sulfonate (LAS), biodegradation, extant kinetics, respirometer,activated sludge

INTRODUCTION

Surface active agents (surfactants) are components of widely used household laundrydetergents, household cleaners, shampoos, cosmetics, antistatic agents, textile aids, and textilesofteners. Linear alkyl benzene sulfonate (LAS) was introduced in 1965 as a biodegradable

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Copyright (c) 2000 Water Environment Federation. All Rights Reserved.

alternative to non-biodegradable branch-chained alkyl benzene sulfonates (ABS) and since hasbecome the common anionic surfactant in commercial detergent formulations. For example, in1994, 950,000 metric tons of LAS were used in Europe, North America, and Japan alone(Nielsen et al., 1997). Trehy et al. (1995) reported environmental LAS concentrations in theinfluent (3.0 – 7.7 mg/L) and effluent (0.003 – 0.086mg/L) of the activated sludge process from10 U.S. domestic wastewater treatment plants. Kaiser et al. (1997) reported LAS concentrationsin the influent to domestic wastewater treatment plants typically ranges from 1 mg/L to 5 mg/L.

LAS consists of a mixture of phenol-substituted alkyl chains (with an average chainlength of 11.8) with all homolog chains having a negatively charged, bound sulfonate group.LAS alkyl chain lengths typically range from C10 to C14 in the United States and from C10 to C13 inEurope (They et al., 1996). C12 LAS is a representative homolog that can be used to study LASbiodegradation characteristics. Representative structures for LAS and C12 LAS are shown inFigure 1 “Chemical structure of linear alkylbenzene sulfonate (LAS) and C12 LAS.” Because of its widespread household use, LAS is commonly present in the influent to municipalactivated sludge POTWs and is discharged to natural water bodies at low concentrations. As aresult, the fate of LAS in wastewater treatment plants has been the subject recent studies. Forinstance, Krueger et al. (1998) observed that LAS was readily biodegraded in activated sludgesystems and the LAS had a half-life of 1-2 days. Others have reported on the complexity in themeasurement of LAS biodegradation intermediates which cause difficulties in biodegradationanalysis (Holt et al, 1995; Trehy et al., 1996; Crescenzi et al., 1996; Federle et al, 1997; Mampelet al, 1998; Krueger et al, 1998). A study by Nielsen et al. (1997), confirmed that LAS wascompletely degraded in wastewater treatment plants. Trehy et al. (1996) reported that theremoval from four activated sludge systems averaged 99.5% for LAS and 99.1% for LASintermediates.

Surfactants are complex organic chemicals where hydrophobic and hydrophilic groupsare joined together in the same molecule. A study of the fate of LAS in wastewater treatmentplants should consider the microbial degradation of surfactants under different microbial growthconditions, since LAS is biodegraded by a consortia of microorganisms (van Ginkel, 1996). Consequently, the growth conditions of the degrading consortia will determine to a large extentthe removal characteristics of LAS and its intermediate degradation products in activated sludgewastewater treatment systems. Operating conditions, such as the SRT, will contribute to theresulting growth kinetics of the degrading microorganisms. Chudoba et al., (1989) suggestedthat both the maximum volumetric removal rate (qv,max ) and maximum specific removal rate(qmax) of xenobiotic compounds were dependent on the SRT of the mixed culture. van Ginkel(1996) demonstrated the importance of SRT for maintaining sufficient surfactant-degradingmicroorganisms in wastewater treatment plants. In addition, HRT was found to have an effect,although less dramatic than the effect of the SRT. In a previous study using porous pots tosimulate activated sludge, effluent concentrations of LAS were found to be a function of influentconcentrations when the HRT was less than 10 h (Kaiser et al., 1997).

In an effort to determine the fate of LAS in wastewater treatment systems, research hasfocused on the development of a technique to measure LAS biodegradation kinetics. Federle etal. (1997) determined that primary and complete biodegradation of LAS were best described by a

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first-order approach with the first-order rate constants of 0.50-0.53h-1. The kinetics and removalof LAS in municipal activated sludge treatment systems have been previously studied usinglaboratory continuous-flow activated sludge systems and radiolabelled LAS (Kaiser et al., 1999). First-order rate constants of LAS removal were determined during this study, but the methods todetermine the kinetic constants were labor-intensive and time consuming. Zhang et al. (1999)found that the biodegradation rate of anionic surfactants over a range of concentrations (i.e., sub-and supra-critical micelle concentrations) followed the Monod kinetics.

The main objective of the present study was to determine the efficacy of the extantrespirometric technique to measure the biodegradation kinetic parameters of surfactants inlaboratory and field activated sludge. The goal was to be able to use the resulting kinetics todescribe, and eventually to predict, the fate of LAS in activated sludge systems. The extantkinetic parameters of LAS were measured over a range of operating conditions at severalactivated sludge wastewater treatment plants, and in porous pot reactors simulating activatedsludge in the laboratory. To evaluate the influence of HRT and SRT, the extant kineticparameters were measured at HRTs of 2, 4, 6, 12 h and SRTs of 3, 6, 10, 15 d. In addition,activated sludge samples from local wastewater treatment plants were evaluated using the sameextant respirometric procedure, and the results were compared with those from the laboratorystudy.

MATERIALS AND METHODS

Porous pot reactors. The laboratory apparatus consisted of two porous pot reactors witha working volume of 1-L. They were operated in parallel as continuous stirred tank reactors(CSTRs) for a period of one year. The porous pot reactors consisted of a stainless steel meshwith a pore size of 65 �, which provided effective separation of suspended solids eliminating theneed for a separate clarifier as shown in Figure 2 “Laboratory porous pot system.” Sludgewastage was performed automatically three times per day using a timer or once per day manuallyto maintain the desired SRT.

Materials. Surfactant LAS used in this study was a mixture of LAS homologs with96.8% C12 LAS, dodecyl benzene sulfonate-sodium salt, in liquid form with 51.5% activefraction. For all kinetic measurements, an injection concentration of 2 mg/L as COD was used. 1 mg/L LAS was found to be equivalent to 2.7 mg/L as COD by the standard COD test. Thefraction of the biomass involved in the biodegradation of LAS was assumed to be equal to thefraction of energy (COD) supplied to the culture by LAS (Blackburn et al.,1987 and Magbanua etal., 1998). Consequently, a competent biomass fraction of 2.7% was used for the laboratoryexperiments. A similar competent biomass fraction (2.9%) was determined for the fieldexperiments.

Phosphate buffer was added to the biomass sample to maintain the pH at approximately6.80 to 7.0 during the respirometer tests (Ellis and Anselm, 1999). The composition of thephosphate buffer used in this study consisted of 6.67g/L Na2 HPO4 �HO2 and 3.39g/L KH2 PO4,and approximately 10 mL buffer solution was added per L sample.

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Extant Respirometric Tests. Respirometric tests were used as a surrogate measurementof LAS disappearance in batch kinetic tests as described previously (Ellis et al., 1996a). In thetest, phosphate buffer was added to the biomass sample from the laboratory porous pot reactor orfield activated sludge aeration basin. The sample was then placed in a 250 mL sealedrespirometric vessel with a constant temperature water jacket (Tudor Glass Co., Belvedere, SC).The dissolved oxygen (DO) concentration was measured by a DO meter (Model 3550, YellowSprings, CO), and the DO probes were fitted with high sensitive membranes. The temperaturewas controlled by a water bath at 25 ± 0.1 �C. The initial dissolved oxygen concentration waselevated to approximately 16-18 mg/L using pure oxygen to prevent oxygen from becominglimiting during the entire respirometric response. The biomass was continuously stirred using amagnetic stir bar. When a linear decrease in DO was observed, a low concentration (2 mg/L asCOD) injection of LAS was made to the respirometric vessel, resulting in a low initial substrateto biomass concentration ratio (S0: X0) ensuring that the test was a measure of the extant kineticsof the biomass (Grady et. al., 1996). The DO response data was collected continuously at asampling frequency of 10 Hz through a data acquisition board installed in a personal computer.The resulting data file was averaged to provide a DO measurement every 2 to 4 seconds andnormalized to subtract the background endogenous oxygen uptake rate. The biodegradationresponse was modeled in an Excel™ spreadsheet, and the kinetic parameters were estimated bynonlinear regression using a fourth-order Runge-Kutta approximation of the Monod equation .

Preliminary experiments to ascertain the reliability and reproducibility of the extanttechnique for measuring surfactant kinetics included experiments to determine the effect of theinitial substrate concentration, the effect of the initial DO concentration, and the effect of re-injecting LAS to the same biomass sample. The tests were conducted with biomass from theBoone Water Pollution Control Plant (WPCP), Boone, Iowa. Grab samples of the influent toBoone plant were collected and measured by liquid chromatography/mass spectroscopy (LC/MS)to determine the LAS influent concentration.

To evaluate the validity of using synthetic wastewater for the laboratory studies, a side-by-side comparison of porous pot reactors fed synthetic and raw wastewater was performed. Extant tests were run to determine whether the kinetic parameters in the two reactors werecomparable. The raw wastewater was collected from the Boone WPCP and diluted to 200 mg/Las COD. The composition of the synthetic wastewater is shown in Table 1 “Characteristics ofsynthetic wastewater.” Both wastewaters were fed at a concentration of 200 mg COD/L, and 2mg/L LAS (5.4 mg/L as COD) was added to the synthetic wastewater. It was assumed that theactual wastewater contained a similar amount of LAS (which was confirmed by subsequentanalysis). The reactors were operated at room temperature 22 ± 2 �C. To maintain a diversemicrobial consortium, 5 ml of mixed liquor from a local municipal wastewater treatment plantwas added to the reactors every other day. This addition represented less than 2% of the feedCOD to the reactors and less than 2% of the porous pot mixed liquor concentration at alloperating conditions.

After it was determined that synthetic wastewater was an acceptable substitute for realwastewater, two porous pot reactors were fed synthetic wastewater to evaluate the influence ofHRT and SRT on the biodegradation responses. The reactors were operated in parallel under a

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constant SRT of 10 d, and HRTs of 2, 4, 6, and 12 h. Subsequently, the reactors were operatedunder a constant of HRT of 6 h, and SRTs of 3, 6, 10, and 15 d. An additional porous potoperating condition was run at 18 h HRT and 30 d SRT to simulate the operating conditions atthe Boone WPCP.

The majority of the field tests were conducted at the Boone WPCP, an extended aerationactivated sludge plant with an HRT of approximately 18 h and SRT in the range of 24 - 30 d. Additional field tests were conducted at the Iowa City Wastewater Treatment Plant (WWTP), aconventional activated sludge plant with an HRT of approximately 4 - 6 h and SRT ofapproximately 6 d.

RESULTS AND DISCUSSION

LAS concentrations were measured in the influent to the Boone WPCP, and the resultsindicated a range of LAS concentrations from 1- 5 mg/L as shown in Table 2 “Concentration ofLAS in the influent to the Boone Water Pollution Control Plant.” These findings aresimilar to the results reported by Kaiser et al., 1997. From this table it can be seen that C12 LASaccounted for about 20% of the total LAS concentration. The C12 homolog was used as therepresentative test compound for this study. To estimate of the competent fraction of LASdegrading biomass, an average LAS concentration of 2.86 mg/L (7.72 mg COD/L) and influentCOD concentration of 265 mg/L were used to calculate a COD fraction of 2.9%. Therefore,since the biomass obtained 2.9% of its energy from LAS, it was assumed that 2.9% of thebiomass had the capacity to degrade LAS (Magbanua, et al., 1998). A competent fraction of2.9% was used for the field studies. Similarly, the competent fraction of degrading biomass inthe porous pot reactors was estimated as 2.7%, since LAS contributed 2.7% of the feed COD.

To evaluate the effect of different initial conditions on the extant respirometric technique,a series of experiments was performed. For instance, different initial DO concentrations wereused when measuring the oxygen consumption to evaluate if this had any effect. After manyrepetitions of LAS biodegradation, 16 mg/L was found to be the lower limit to allow thecomplete biodegradation of LAS in the laboratory experiment prior to oxygen becoming limiting(at approximately 1 mg/L). The upper DO concentration limit of the DO meter wasapproximately 20 mg/L, and a range of DO concentrations from 16 to 20 mg/L was used toevaluate the influence of the initial DO on the measured kinetic parameters. The biomass forthese experiments was obtained from a porous pot reactor with an HRT of 6 h and a SRT of 15 d,and the results are shown in Table 3 “Influence of the initial DO Concentration on the extantkinetics of LAS.” These results suggest that the initial DO concentration in this range did nothave an impact on the resulting measured kinetic parameters. Similar results were obtained whencomparing the kinetics for LAS by biomass that had received one injection and biomass that hadreceived several repeated injections.

A typical respirometric response of a biomass sample to an injection of LAS in therespirometric procedure is given in Figure 3 “Normalized respirometric response and modelfit for an Iowa City WWTP biomass sample to an injection of LAS.” The biomass for this

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experiment was obtained from the Iowa City WWTP and had a mixed liquor volatile solidsconcentration of 1990 mg/L. The goodness of fit of the Monod model is illustrated by thisfigure. In addition, the reproducibility of the kinetic parameter estimates was demonstrated bythe standard deviations within an experiment. Typically the standard deviations were within 20%of the mean values for most of the measured parameters. One exception to this was the standarddeviations for KS which were somewhat higher.

During the comparison of raw and synthetic wastewater in the porous pot reactorsoperated at a HRT of 12 h and SRT of 8 d, biodegradation kinetics were measured periodically. The results are shown in Table 4 “Extant kinetic parameters from porous pot reactors fedsynthetic and actual wastewater.” Comparison with the Student t-test indicates that there wasno significant difference between the parameters obtained from the two systems at an α=0.05. Ina separate experiment, the extant kinetics of the composite synthetic and raw wastewater wasmeasured using the corresponding biomass from the Boone plant. In these experiments, 2 mgCOD/L of the total wastewater (i.e., not just one component of the wastewater such as LAS) wasinjected into the extant respirometer. These results (Table 5 Extant kinetic parameters ofsynthetic and raw wastewater by Boone biomass”) also indicated very similar responsesbetween the two systems with respect to the pseudo-first order rate coefficient, k (where k =q̂/KS). As expected for the total wastewater, the KS values were higher than the injectionconcentration (2 mg/L as COD), and in these instances, separate estimates of q̂ and KS are notpossible (Ellis et al., 1996a) due to the correlation between the parameters at these experimentalconditions (Robinson, 1985; Robinson and Tiedje,1983). Sykes (1999) has suggested that the KSvalue for a multicomponent wastewater is a cumulative function of the individual KS values forthe individual substrates, and this would explain a KS value greater than 2 mg/L as COD for theseexperiments. Consequently, the k value (L/mg�h) was reported. It can also be seen from this datathat the composite wastewater samples had significantly higher yield values than LAS alone. This is likely due to incomplete biodegradation of the entire organic fraction of the wastewaterinjection during the approximately 30 minute time period of the extant test. It is likely that theparticulate COD fraction of the synthetic and raw wastewater samples took longer to degradeduring the test. In any event, the interesting results from this experiment was the similarity inresponse by the Boone biomass sample to the synthetic and raw wastewater samples. Thesimilarity in the biodegradation kinetic parameters obtained with the biomass from the twoporous pot reactors and by the Boone biomass sample suggests that the synthetic wastewater wasa valid alternative to raw wastewater for the subsequent porous pot reactor studies to examine theinfluence of HRT and SRT on LAS kinetics.

Effect of HRT and SRT on LAS biodegradation. Experiments to test the influence ofa range of HRTs (2 h, 4 h, 6 h and 12 h) with a constant SRT of 10 d on the biodegradationkinetics of LAS were performed. Subsequently, the experiments to test the influence of a rangeof SRTs (3 d, 6 d, 10 d, 15 d) with a constant HRT of 6 h were conducted. The results of theextant biodegradation tests are shown in the Table 6 “Influence of HRT and SRT on thebiodegradation kinetics of LAS.” In addition, the trends in the kinetic responses are shown inFigure 4 “Extant biodegradation kinetics of LAS as a function of HRT” and Figure 5“Extant biodegradation kinetics of LAS as a function of SRT.”

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It can be seen from Table 6 and Figure 4 that the kinetic parameters were fairly constantwith a µ̂ of 0.08 - 0.09 h-1, a q̂ of 0.13~0.14 h-1, a KS of 0.16 mg COD/L and a Y of 0.65~0.66mg/mg, at HRTs longer than 6 h. At lower HRTs more variability in the extant kineticparameters was observed. This could be explained by the fact that at lower HRTs the reactorsbehaved less like ideal CSTR systems (i.e., there was more opportunity for short circuiting andvariations in flow at shorter HRTs). Similar results were observed by Kaiser et al.(1997) whereeffluent concentration of LAS remained constant and relatively independent of influentconcentrations at higher HRTs, but varied at lower HRTs.

The effect of SRT on the biodegradation of LAS is shown in Figure 5. These results alsosuggest that SRT did not have a dramatic effect on the measured biodegradation kinetics of LAS. The yield increased slightly with increased SRT at low SRT conditions, but stayed constant atlonger SRTs. There appeared to be a slight decrease in µ̂, q̂, and KS at long SRT conditions, suggesting a low velocity, high affinity enzyme system at these conditions. The evidence forthis, however, was not strong. In pure culture studies, Sokol (1987, 88a, 88b, 92) observed amuch more pronounced decrease in µ̂ values for cultures grown at increasing long SRTs.

The results of these experiments indicate that operating conditions have some impact onthe complete biodegradation of LAS. But when the HRT is long enough, the effect of HRT canbe ignored. Compared with HRT, SRT has more impact on the biodegradation of LAS. Thebiodegradation rate for LAS will slightly decrease when the SRT is long enough. The extantkinetics ranges of LAS obtained from the biomass fed by synthetic wastewater are 0.50-0.69mg/mg for yield, 0.05-0.20 h-1 for µ̂ values, 0.09-0.33 h-1 for q̂ and 0.09-0.78 mg COD /L for KS.

To further evaluate the capability of the respirometer technique to obtain comparablekinetics of LAS from the lab and the field, one porous pot reactor was run to simulate theoperating conditions of the Boone WPCP under a HRT of 18 h and a SRT of 30 d. Table 7“Extant kinetics of LAS at the Boone and Iowa City plants and laboratory porous potssimulating field conditions” and provides a comparison of the extant kinetics of LAS measuredusing laboratory biomass simulating field conditions and biomass from the Boone and Iowa Cityplants. Student-t tests suggest that there were no significant differences in the values of µ̂, KS,and Y between the three biomass samples tested at an α = 0.05. These results suggest that thelaboratory simulation of the field conditions provided an accurate assessment of the actual kineticcapabilities. This would be important for operating laboratory systems to predict full-scaleperformance with regard to the impact of operational changes on the biodegradation kinetics ofspecific organic compounds. The results in Table 7 are also shown in Figure 4 and Figure 5 tocompare with the results of the laboratory study concerining the impact of HRT and SRT. Thesimilar ranges of the kinetic values and the similar trends with respect to changes in HRT andSRT give more evidence to support the conclusions obtained in the laboratory study.

During this study, field biomass samples were collected periodically and the extantkinetics of LAS were measured. A competent biomass fraction of 2.9% was used for all the fielddata analysis. Table 7 and Figure 6 show the variability in the measured µ̂, q̂, KS, and Yvalues for the Boone WPCP. The interesting finding from this data is that the variability of thefield data was comparable to the variability seen in laboratory activated sludge systems operated

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at steady-state over a prolonged period of time (Bielefeldt and Stensel, 1999, and Ellis et al.,1996b). One might expect that the variability of full-scale systems which have varying influentconcentrations, varying flow rates, and fluctuating operating conditions would be considerablygreater than laboratory systems intentionally operated at steady-state. These findings raiseimportant questions as to what causes the variability in biodegradation kinetics. Once the kineticvariability is characterized, the resulting changes in biodegradation rates can be accounted forduring the design and operation of activated sludge systems.

CONCLUSION

The efficacy of the extant respirometric technique to measure the extant kinetics of LASbiodegradation by field and laboratory biomass was demonstrated in this study. LASbiodegradation kinetics in laboratory porous pot reactors were independent of whether the reactorwas fed synthetic or real wastewater. The influence of HRT on the measured biodegradationkinetics was minimal (µ̂ = 0.14 ± 0.06 h-1, KS = 0.4 ± 0.3 mg COD/L, and Y = 0.67 ± 0.02 mgbiomass COD/mg substrate COD) with the possible exception that the biokinetic parameterswere more variable at the low HRT conditions (i.e., when HRT < 6 h). The SRT had morenoticeable effect on the measured biodegradation kinetics (e.g., Y increased from 0.50 ± 0.08 to0.66 ± 0.05 mg/mg when the SRT increased from 3 to 10 d at a constant HRT of 6 h).

When the laboratory porous pot reactors were operated to simulate field conditions,similar extant kinetic parameters resulted. In fact, the extant kinetics (µ̂, KS, and Y) from bothfield sites, the Boone WPCP and Iowa City WWTP, were not significantly different at the 95%confidence level. These findings suggest that there is not a wide variation in the kinetic responsefor LAS among different treatment plants. The week to week variability in LAS biodegradationkinetics at the Boone plant was significant. This variability, whether due to the short termchanges in operating conditions or gradual changes in the microbial community structure, wasnot substantially different from what has been seen in laboratory activated sludge systemsintentionally operated at steady-state. The usefulness of the extant respirometric technique torapidly and reproducibly track changes in LAS biodegradation kinetics in activated sludgecultures in the laboratory and the field was demonstrated.

ACKNOWLEDGMENTS

The authors thank Bill Begley and David Lee at Procter and Gamble for their expertiseand assistance in determining LAS concentrations and Dave Mozena at the Boone WPCP andSteven Julius at the Iowa City Wastewater Treatment Plant for their help in collecting mixedliquor samples. This work was funded by the Water Environment Research Foundation (98-CTS-3). This manuscript has not been subjected to the Foundation’s peer and administrativereview and therefore does not necessarily reflect the views of the Foundation, and no officialendorsement should be inferred.

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Table 1. Characteristics of synthetic wastewater fed to the porous pot reactors.

Macronutrients Concentration, mg/L

UreaNutrient broth

Lauric acidPotato starch

Non-fat dried milkDietary fiber

Sodium acetateNa(HCO3)

K3PO4 • H2OFeSO4 • 7H2O

LASAS

37.660.07.06.060.010.020.010.03.00.52.01.0

Micronutrients Concentration, �g/L

NiSO4 • 6H2OZnCl2

CuCl2 • 2H2OCoCl2 • 6H2O MnSO4 • H2O

EDTA K2MoO4

100621591822745

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Table 2. Concentration of LAS in the influent to the Boone Water Pollution Control Plant.

Date Collected

C10 LASmg/L

C11 LASmg/L

C12 LASmg/L

C13 LASmg/L

C14 LASmg/L

Total LAS C10-14 mg/L

9/23/99 0.74 0.54 0.18 <0.05 <0.05 1.46

9/23/99 0.66 0.36 0.1 <0.05 <0.05 1.12

10/7/99 1.1 0.82 0.44 <0.05 <0.05 2.36

10/7/99 1.08 0.94 0.56 <0.05 <0.05 2.58

10/8/99 1.76 1.88 0.9 0.18 <0.05 4.72

10/8/99 1.86 1.68 1.16 0.22 <0.05 4.92avg ± s.d. 1.20 ± 0.50 1.03 ± 0.61 0.55 ± 0.41 <0.2 ± 0.03 <0.05 2.86 ± 1.61

Table 3. Influence of the initial DO concentration on the extant kinetics of LAS.

No. µ̂, h -1 q̂, h -1 KS, mg COD/L Y, mg/mg Initial DO, mg/L

1 0.067 0.098 0.055 0.677 16.645

2 0.067 0.098 0.159 0.681 17.749

3 0.056 0.084 0.215 0.668 19.897

4 0.057 0.077 0.032 0.733 18.677

5 0.060 0.082 0.061 0.732 18.770

6 0.051 0.071 0.014 0.725 19.661

Average 0.059 0.085 0.089 0.703 18.567

s.d. 0.006 0.011 0.079 0.030 1.215

The µ̂, q̂, KS, Y values refer to the maximum specific growth rate, maximum specific substrateremoval rate, half-saturation coefficient, and biomass yield coefficient, respectively, in theMonod equation. All parameters are in terms of COD units. The MLVSS concentration of thebiomass was 1550 mg/L and the LAS injection concentration was of 2 mg COD/L. S.d. refers tothe standard deviation of the mean.

WEFTEC 2000


Table 4. Extant Kinetic parameters from porous pot reactors fed synthetic and actualwastewater (12 h HRT, 8 d SRT).

Day µ̂, h-1 q̂, h-1

KS, mg/L as

COD Y, mg/mgMLVSS,

mg/L n

Reactor fed synthetic wastewater

1 0.03 0.06 0.16 0.54 2650 1

10 0.021 0.065 0.905 0.318 1380 1

20 0.030 0.094 0.425 0.321 808 1

30 0.042 0.135 0.100 0.312 633 1

40 0.049 0.080 0.100 0.425 604 1

47 0.035 0.130 0.400 0.428 604 3

avg ± s.d. 0.035 ± 0.011 0.102 ± 0 031 0.386 ± 0.330 0.347 ± 0.047 7Reactor fed raw wastewater

1 0.03 0.06 0.16 0.54 2650 1

10 0.033 0.089 0.727 0.369 1080 1

20 0.053 0.089 0.196 0.593 772 1

30 0.027 0.089 0.100 0.298 614 1

40 0.029 0.093 0.400 0.314 592 2

47 0.036 0.112 0.439 0.337 632 7

avg ± s.d. 0.033 ± 0.011 0.099 ± 0.014 0.459 ± 0.307 0.348 ± 0.136 12

The parameters are as defined in Table 3.

WEFTEC 2000


Table 5. Extant kinetic parameters of synthetic and raw wastewater by Boone WPCPbiomass.

System k , L/mg�h Y, mgCOD/mgCOD MLVSS, mg/L

1

0.0199 0.773

6040.00987 0.659

avg: 0.0149 ± 0.0071 avg: 0.716 ± 0.081

2

0.0157 0.871

592

0.00935 0.822

0.0157 0.824

0.0188 0.755

0.0119 0.853

avg: 0.0143 ± 0.0037 avg: 0.825 ± 0.044

* Reactor 1 was the porous pot reactor fed synthetic wastewater and the injected substrate wassynthetic wastewater resulting in a concentration of 2 mg/L as COD. Reactor 2 was fed actualwastewater from the Boone Water Pollution Control Plant and the injected substrate was actualwastewater resulting in a concentration of 2 mg/L as COD. The k value is the pseudo-first orderrate coefficient (where k = q̂/KS) measured in the extant technique when separate estimates of q̂and KS are not possible.

WEFTEC 2000


Table 6. The influence of HRT and SRT on the biodegradation kinetics of LAS.

HRT, day

SRT, day

µ̂, h-1

µ̂X, mg(L× h)-1

q̂, h-1

q̂x, mg(L× h)-1

KS,mgCOD/L

K(q̂/KS)L(mgCOD h)-1

Y, mg/mg

VSS, mg/L

n

2 10 0.18± 0.07 24.93±8.81 0.26± 0.13 36.10±16.80 0.78± 0.86 0.34±0.15 0.68± 0.10 3574±263 10

4 10 0.20± 0.05 17.10±4.20 0.33± 0.13 28.26±10.74 0.47± 0.30 0.69±0.42 0.68± 0.07 2244±26 10

6 10 0.08± 0.03 4.26±1.34 0.13±0..04 6.51±1.88 0.16± 0.15 0.81±0.24 0.66±0..05 1336±41 10

12 10 0.09±0..02 2.70±0.56 0.14±0.02 4.15±0.72 0.16±0..18 0.83±0.12 0.65±0.05 785±19 10

6 3 0.05± 0.01 0.52±0.11 0.10± 0.02 1.00±0.17 0.18± 0.07 0.59±0.24 0.50± 0.08 250 10

6 6 0.08± 0.02 1.42±0.35 0.11± 0.02 2.08±0.42 0.09± 0.11 1.25±0.18 0.65± 0.04 472± 13 10

6 10 0.08± 0.03 4.26±1.74 0.13±0..04 6.51±1.88 0.16± 0.15 0.81±0.24 0.66 ± 0.06 1336± 41 10

6 15 0.06±0.01 3.73± 0.60 0.09± 0.02 5.35± 0.99 0.09± 0.10 1.01±0.17 0.69± 0.03 1550 10

The biomass used for these tests were obtained from the porous pot reactors at steady-state-conditions under different operatingconditions. The parameters are as defined in Table 3.

WEFTEC 2000


Table 7. Extant kinetics of LAS at the Boone and Iowa City plants and laboratory porouspots simulating field conditions.

Date µ̂, h-1 µ̂X, mg (L�h)-1 q̂, h-1 KS, mgCOD/L Y, mg/mg MLVSS, mg/L

Boone WPCP

8/23/99 0.02 2.45 0.06 0.16 0.54 2650

9/6/99 0.05 5.01 0.09 0.02 0.21 2250

3/23/00 0.04 5.28 0.15 0.58 0.40 3100

4/1/00 0.02 2.99 0.06 0.55 0.56 3415

4/06/00 0.01 2.49 0.08 0.10 0.21 4380

4/19/00 0.02 7.60 0.07 0.28 0.53 7500

ave ± s.d. 0.03±0.0 4.30±2.04 0.10±0. 0.39±0.36 0.46±0.21 3756

Iowa City Wastewater Treatment Plant, n = 5

ave ± s.d. 0.05±0.0 4.06±2.08 0.14±0. 0.19±0.06 0.50±0.14 1990

Porous pot simulation of Boone WPCP, n = 10

ave ± s.d. 0.02±0.0 2.14±0.85 0.05±0. 0.11±0.16 0.48±0.13 2250

The parameters are as defined in Table 3.

WEFTEC 2000


CH3 (CH2 )X CH (CH2 )Y CH3

SO3

CH3 (CH2 )9 CH CH3

Na +SO3

Figure 1. Chemical structure of linear alkylbenzene sulfonate (LAS) and C12 LAS where xplus y equals 7 to 11 depending on the length of the alkyl chain (Trehy et al, 1996).

LAS

C12 LAS

WEFTEC 2000


Sludgewastage

Influent

(200 mg/L COD)

Effluent Stainless steel pot(vol~1000mL)

Airbubble

PlexiglasCylinder

Figure 2. Laboratory porous pot system.

WEFTEC 2000


WEFTEC 2000


extant biodegradation testing with linear alkylbenzene ...tge/wc0054p3.pdf · extant biodegradation...

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