363 16 Chemical Processes during Biological Wastewater Treatment Willie F. Harper, Jr., Tamara Floyd-Smith, and Taewoo Yi 16.1 INTRODUCTION Removing pharmaceutical and personal-care products (PPCPs) during biological wastewatertreatmentisimportantforpreventingtherapidaccumulationofthese chemicals in our environment. Accordingly, the wastewater treatment community has responded to these concerns with a great deal of applied research. Analytical methodsarenowavailableforlow-leveldetectionofPPCPsinwastewater,andsur- veys of wastewater inuent and efuent streams have revealed the broad classes of micropollutants present in municipal wastewater (see Chapter 1 and Chapter 5 for a review of the various classes of PPCPs and veterinary medicines present in waste- water). This chapter presents experimental ndings related to the sorption and bio- degradation of various classes of PPCPs in biological wastewater treatment systems. Thisincludesareviewoffull-scalePPCPremovalperformanceandlooksatkey issuesrelatedtobothsorptionandbiodegradation.Therealsoisdiscussionrelatedto the possible effects of antibiotic compounds on the spread of antimicrobial-resistant microorganisms via the activated sludge process. Contents 16.1 Introduction 363 16.2 The Activated Sludge Process: A Brief Overview 364 16.3 Full-Scale Studies 364 16.4 Sorption 368 16.5 Biodegradation 371 16.6 Antibiotic-Resistant Microorganisms and the Activated Sludge Process 376 16.7 Conclusion 378 References 378 © 2008 by Taylor & Francis Group, LLC 364 Fate of Pharmaceuticals in the Environment and in Water Treatment Systems 16.2 THE ACTIVATED SLUDGE PROCESS: A BRIEF OVERVIEW Theactivatedsludgeprocessisusedtotreatbothmunicipalandindustrialwaste- waterbeforethewaterisreturnedtotheenvironment(orreused).Intheactivated sludge process, microorganisms remove soluble organic constituents from wastewa - te r. A conventional municipal activated sludge wastewater treatment plant (WWTP) schematic is shown inF igure16.1 . Inuent wastewater is screened for removal of wastewaterlargedebris(e.g.,rags,glass,rocks)andthenitisfedtoaprimaryclari- e rforremovalofsettleableparticulatematter.Theprimaryefuentisthenfedto an aeration basin where particulate and dissolved organics and nutrients are removed by a occulent biomass. It is in this basin that actively growing microorganisms maytakepartinchemicalreactionsthatremoveandperhapstransformPPCPs.The wastewateristhenroutedtoasecondaryclarierforbiomassrecycleandforsolids separation to produce a claried secondary efuent. In many wastewater treatment facilities,secondaryefuentisfurthertreatedwithgranularltrationforremovalof nonsettleablematerialordisinfectiontodestroypathogens. 16.3 FULL-SCALE STUDIES NumerousreportshaveexploredtheremovalofvariousclassesofPPCPsatfull scale,generallyattemptingtoevaluatewhethermunicipalWWTPsareactingas persistent point sources for PPCP discharge to the environment. Ternes 1 showed that theremovalefcienciesrangedfrom10to90%inWWTPsinGermany,andTernes et al. 2 showedthatremovalefcienciesforpolarPPCPsvariedfrom12to90%for WWTPsinBrazil.Gomezetal. 3 conducteda1-yearmonitoringstudyatasewage treatmentplantinSpain,andtheyfoundthattheremovalefcienciesfor14organic micropollutantsvariedfrom20%(carbamazepine)to99%(acetaminophen).Joss et al. 4 showed that only 4 out of 35 compounds are 90% removed using state-of- the-artbiologicaltreatmentsystems,and17outof35areremovedatlessthan50% efciency. These studies are in addition to others that present high removal efcien - ci es. Oppenheimer and Stephenson 5 found that removal efciencies for frequently detectedPPCPsweregenerallyhigh(>80%),andanotherstudybyJonesetal. 6 FIGURE 16.1 Conventional activated sludge wastewater treatment plant schematic. © 2008 by Taylor & Francis Group, LLC Chemical Processes during Biological Wastewater Treatment 365 found that ibuprofen, paracetamol, salbutamol, and mefenamic acid were removed at approximately 90% within a large sewage treatment plant in England. Overall, these efforts have shown that the removal efciencies vary greatly. That conclusion that PPCP removal in full-scale systems varies considerably is further supported by Lishman et al., 7 who investigated the presence of selected acidic drugs, triclosan, polycyclic musks, and selected estrogens in WWTP inuent and efuent at sites in Canada. They found that three analytes were never detected during the survey (clobric acid, fenoprofen, fenobrate) and three analytes were always removed at high efciency for all treatment congurations (ibuprofen, naproxen, triclosan). Two analytes were removed at low efciencies (gembrozil, diclofenac), but better removals were observed for treatment congurations with higher solid retention times. Five polycyclic musks were surveyed; general conclu- sions could not be reached because of the small dataset and because of numerous nonquantiable results, but removal efciencies generally were variable. E2 and E1 were both removed at high efciency for all treatment systems. As shown in Fig- ure 16.2, even where conventional WWTPs are concerned, removal efciencies for different PPCPs can vary signicantly. Diclofenac removal efciency is negative in Figure 16.2, suggesting that diclofenac may be deconjugated during the treatment process. Generally, these full-scale studies have not collected the type and amount of data necessary to organize mass balances for specic PPCPs, so that a clear articu- lation of the relative roles of sorption and biodegradation in the full-scale process is generally unavailable. Some studies have complemented full-scale studies with batch experiments, so that the potential for sorption or biodegradation at full-scale can be assessed. Removal efciencies can vary as a function of the type of compound. Carballa et al. 8 surveyed two cosmetic ingredients (galaxolide, tonalide), eight pharmaceuticals (carbamazepine, diazepam, diclofenac, ibuprofen, naproxen, roxithromycin, sulfa- methoxazole, and iopromide), and three hormones (estrone, 17β-estradiol, and 17α- –150 –100 –50 0 50 100 150 IBP NPX TCL ADBI AHTN DCF Compound Removal Efficiency (%) Plant 4 Plant 5 Plant 7 IBP — Ibuprofen; NPX — Naproxen; TCL — Triclosan ADBI — Celestolide; AHTN — Phantolide; DCF — Diclofenac FIgure 16.2 Removal efciencies for selected PPCPs for three conventional activated sludge systems as reported by Lishman et al., 2006. (Image created by W.F. Harper, Jr.) © 2008 by Taylor & Francis Group, LLC 366 Fate of Pharmaceuticals in the Environment and in Water Treatment Systems ethinylestradiol) at municipal WWTPs in Spain. They found that the overall removal efciencies ranged between 70 and 90% for the fragrances, 40 and 65% for the anti- inammatories, approximately 65% for 17 C-estradiol,and60%forsulfamethoxa- zole. However, the concentration of estrone increased along the treatment due to the partial oxidation of 17 C-estradiol in the aeration tank. Nakada et al. 9 measured a host of compounds, including six acidic analgesics or anti-inammatories (aspirin, ibuprofen, naproxen, ketoprofen, fenoprofen, mefenamic acid), two phenolic antisep - tics (thymol, triclosan), four amide pharmaceuticals (propyphenazone, crotamiton, carbamazepine, diethyltoluamide), three phenolic endocrine disrupting chemicals (nonylphenol, octylphenol, bisphenol A), and three natural estrogens (17 C- estradiol, e strone, estriol) in 24-h composite samples of inuents and secondary efuents from municipal WWTPs in Tokyo. They found that aspirin, ibuprofen, and thymol were removedefcientlyduringsecondarytreatment(>90%efciency).Theyalsofound that amide-type pharmaceuticals, ketoprofen, and naproxen showed poor removal (<50% efciency), probably because of their lower hydrophobicity (log K ow <3).This studywasalsothersttoreportthepresenceofcrotamiton(atopicaltreatmentfor scabies),andtoshowthatitispersistentduringsecondarytreatment.Overall,these results reinforce the conclusion that removal efciencies vary for the various PPCPs and suggest that chemical characteristics also may play an important role in deter - miningthefateofeachcompoundinbiologicalwastewatertreatment. Removal efciencies also can vary as a function of the sludge retention time (SRT). Oppenheimer and Stephenson 5 studiedtheremovalof20PPCPsinfull-scale and pilot-scale WWTPs in the United States, and they organized their data using abin assign m entsystem,whichassignedeachdetectedcompoundintoacategory related to the frequency of detection (i.e., infrequent, variable, and frequent) and into another category related to the removal efciencies (excellent removal, moderate removal,poorremoval).TheyfoundthathalfofthePPCPswerefrequentlydetected andwereremovedatlessthan80%efciencyatanSRTof5daysorless.Caffeine andibuprofenwereamongninecompoundsthatwerebothfrequentlydetectedand removedwellforallthesystemsinthestudy.Galaxolideandmuskketonewerealso frequentlydetectedbutremovedat80%onlywhentheSRTexceeded25days. Membrane bioreactor systems (MBRs) have been evaluated as possibly better technologyforremovingPPCPs.MBRsuseasuspendedgrowthbioreactor,like in conventional activated sludge, but replaces gravity sedimentation with micro- or ultraltration( Figure 16 .3). The MBR is an attractive treatment conguration because it eliminates the need for secondary clarication, which in turn allows the overall treatment process to be sited on a much smaller footprint. Kim et al. 10 found that the MBR system was efcient for hormones (e.g., estriol, testosterone, androstene- d i one) and certain pharmaceuticals (e.g., acetaminophen, ibuprofen, and caffeine) withapproximately99%removal,butMBRtreatmentdidnotdecreasetheconcen - tration of erythromycin, trimethoprim, naproxen, diclofenac, and carbamazepine. Oppenheimer and Stephenson 5 usedalimiteddatasettosuggestthatMBRprovided no additional PPCP removal, when compared to similarly operated conventional systems. Kimura et al. 11 foundthatMBRsexhibitedmuchbetterremovalregard- ingketoprofenandnaproxen,butwithrespecttotheothercompounds,comparable removal was observed between the MBRs and conventional systems. These data © 2008 by Taylor & Francis Group, LLC Chemical Processes during Biological Wastewater Treatment 367 suggestthatMBRslikelyoffernoinherentadvantageoverconventionalsystemsfor removingPPCPs,butbecauseMBRsareoperatedatlongsolidretentiontimesand at high mixed liquor suspended solids (MLSS) concentrations, those operational fac - to rsarelikelythecauseofanymeasureddifferencesinPPCPremovalefciencies. Finally,thereremainsaneedtocontinuetoconductfull-scalestudies,withthe goal of organizing accurate mass balance and fate data. To accomplish this, rigorous wastewater sampling methods must be employed. For example, these full-scale stud - ie s collected data using time-weighted composite sampling using automatic sam- pl ers, equipped with sample storage in cooled compartments. This strategy allowed the reports to collect data that are likely to represent a reasonable estimate of the PPCPconcentrationsofinterest,aswellastheinherentvariability;butthisapproach is not infallible. Many of the PPCPs of interest are biodegradable and may be trans - fo rmed while the samples remain stored in the collection container. Still other com- po undsarehighlyhydrophobicandsorbstronglytobiomasssolidsandcolloidal materials that are also present in the original sample. In these cases, it is possible to underestimate the concentrations of interest, either because the solids are not prop - er ly resuspended before sample analysis, or because of inadequate extraction tech- ni ques. Finally, time-weighted sampling collects a given wastewater volume at given time intervals, even if the wastewater ow is low. This means that time-weighted sampling may cause low-ow PPCP concentrations to be overrepresented in the composite sample. For these reasons, future sampling campaigns should consider the use of ow-weighted sampling in combination with frequent grab sampling to FIGURE 16.3 Membrane bioreactor schematic diagram. © 2008 by Taylor & Francis Group, LLC 368 Fate of Pharmaceuticals in the Environment and in Water Treatment Systems minimize the error associated with sample collection. Each collected sample should alsobemixedvigorouslytoresuspendsettledmaterial,andPPCPanalysisshouldbe carried out on both the ltered and unltered samples. Improvements in sample col- le ction methodology will strengthen the reliability of the data, which in turn will no doubt be the basis for future treatment plant optimization and regulatory action. 16.4 SORPTION In general, the partitioning of organic compounds from water onto activated sludge biomassisreferredtoasadsorption,althoughitmaybemoreappropriatetoreferto thisassorptionbecausetheremaybesomeuncertaintyastowhetherthecompound is on the surface (adsorption) or partitioning into another phase (absorption). When sorptionisofinterest,itisimportanttoestablisharelationshipbetweenwhatison thesurfaceandwhatisintheaqueousphase,arelationshipgenerallyreferredtoas a sorption isotherm. The term isotherm comes f rom the idea that the equilibrium is reachedataconstanttemperaturetodistinguishthistypeofpartitioningfromcon- densation. These relationships are determined experimentally and then the data are usedtodetermineapartitioningcoefcient,whichisameasurefortheafnityofa givencompoundfortheactivatedsludgebiomass. Partitioning coefcients (K d )havebeendeterminedinanumberofstudiesto investigate PPCP sorption to activated sludge. Ternes et al. 12 conductedaseriesof batch tests with primary and secondary sludge slurries to determine partitioning coefcientsforanumberoftargetPPCPs.TheyfoundthattheK d values of pharma- ceuticalsrangedfrom<1to500Lkg –1 , while that of the polycyclic musk fragrances acetyl hexamethyl tetrahydronaphthalene (AHTN) and hexahydrohexamethylcyclo- pentabenzopyran(HHCB)provedtobemuchhigherandupto5300and4900Lkg −1 , respectively. They also found signicant differences between the K d values obtained between primary sludge and secondary sludge. For acidic pharmaceuticals and musk fragrances, the K d values were higher when measured with primary sludge; the oppo- sitewastruewithneutralpharmaceuticals,iopromide,andethinylestradiol. The sorption equilibrium partitioning coefcients determined for steroid estro- ge nswithactivatedsludgeshowsomelimitedvariability,buttheyaregenerallyin good agreement (Figure 16.4).Claraetal. 13 foundthatthelog(K d ) for steroid estro- genswas2.84(2.64to2.97)and2.84(2.71to3.00)forE2andEE2,respectively.In theworkbyTernesetal. 12 the log (K d ) for EE2 was determined to be 2.54 (2.49 to 2.58). Yi et al. 14 foundthatthelogK d forEE2was2.7formembranebioreactorsludge and2.3whenthesludgewastakenfromasequencingbatchreactor,sincetheMBR particle sizes were signicantly smaller than the SBR particles. This result suggested that particle size may explain some of the variability that is reported for steroid estro- ge npartitioningcoefcients.Andersenetal. 15 determined distribution coefcients (K d )withactivatedsludgebiomassforthesteroidestrogensestrone(E1),17C-estra- diol (E2), and 17B-ethinylestradiol (EE2) in batch experiments, and they determined log K d valuesforsteroidestrogensof2.6,2.7,and2.8,respectively.WhenAndersen et al. 15 corrected their log K d values to account for the organic carbon content of thesludge,theyfoundthatthelogK d values were 3.16, 3.24, and 3.32, respectively. These values were remarkably consistent with the sorption partitioning coefcients © 2008 by Taylor & Francis Group, LLC Chemical Processes during Biological Wastewater Treatment 369 determinedwheresoilisusedasthesorbate. 16–19 Taken together, these partitioning coefcients enable practitioners to model PPCP sorption in activated sludge processes andnumericallyevaluatetheimportanceofsorptionasaremovalmechanism. Sorptionisnotalwaysanimportantremovalmechanism.Ternesetal. 12 found that, for compounds with the K d values less than 500 L Kg -1 ,only20%ofthetargetcompound masswasassociatedwiththesludgesolids,whichshowedthatthemajorityofthemass of the target compounds remained in solution. This result supported the idea that sorp- ti onisnotanimportantremovalmechanismformany ph armaceutical compounds. Yu et al. 20 conducted aerobic batch biodegradation (using activated sludge as microbial inocula) experimentstoevaluatethebiodegradationbehaviorof18targetPPCPsatinitialconcen- tr ations of 50, 10, and 1 μg L -1 . The target compounds included a number of antiseptics, barbiturates, and anticonvulsants. Their sterile control studies showed no loss of target PPCPsduringtheentireincubationperiod,andsorptiontothebiomasswasfoundtobe negligibleforalltestingconditions.UraseandKikuta 21 conducted a series batch experi- menttoexaminetheremovalof3steroidestrogens(i.e.,17C-estradiol), 2 e ndocrine dis- ruptors (i.e., bisphenol A), and 10 pharmaceutical substances by activated sludge. Many of the target PPCPs in this study were hydrophilic, had lower water–sludge partition coef- c ients than the steroid estrogens, and remained in the aqueous phase, with only a small fraction partitioning to the activated sludge. When sorption is important, there is a sorption/desorption cycle that should be investigated experimentally. In some cases desorption fails to restore the full capac - ity of the sorbent, and when this happens some of the sorption sites remain occupied. This is referred to as sorption hysteresis, and this has been reported for many organic compounds where either soil or sludge acts as the sorbent. 22–24 Hysteresis has thus farreceivedlittleattentionwherePPCPsorptiontosludgeisconcerned.Recently, FIGURE 16.4 Partitioning coefcients determined for steroid estrogen sorption to acti- vated sludge. 0 0.5 1 1.5 2 2.5 3 Clara et al. 2005 Ternes et al. 2004 Yi et al. 2006 (MBR) Yi et al. 2006 (CBR) Andersen et al. 2005 R eference log (K d ) EE2 E2 E1 © 2008 by Taylor & Francis Group, LLC 370 Fate of Pharmaceuticals in the Environment and in Water Treatment Systems Kimetal. 23 showed sorption hysteresis in the case of tetracycline sorption/desorp- tion with activated sludge, but this is probably because tetracycline forms strong complexeswithCa(II)andotherdivalentcationsknowntobeimportantforoc stability. 25,26 PPCPsorptionhysteresisisabasicandrelevantprocessthathasnot received great attention to date. One cause of sorption hysteresis may be related to particle characteristics (e.g., size),andthereisaneedtostudythepossiblefundamentalconnections.Yiand Harper 27 hypothesized that sorption hysteresis is more pronounced as the biomass particle size distribution shifts toward larger sizes. The rationale for this was that smallerocsaremoredenseandlesspermeablethanlargeroc, 28,29 therefore allow- ing for much less intraparticle entrapment of PPCPs. In general, activated sludge particlesinconventionalprocessesaretypically80to300μmindiameter, 30 and thisstructuretypicallyconsistsofsmallermicrocolonies(approximately8to15μm) connectedbyexocellularpolymericandinorganicmaterial,andwithafewlarge ow channels that facilitate transport. 28,29 Smaller activated sludge particles can be foundinbioreactorslikeMBRs, 14,31 and smaller particles have less internal polymer, ahighernumberofcellsperunitvolume, 28 andtheydonothavethelargeowchan- nels that facilitate transport. Yi and Harper 27 investigated this hypothesis by operating two laboratory-scale bioreactor systems and an MBR and a conventional bioreactor (CBR), both operated in continuous ow mode. The experimental strategy was to harvest biomass from the bioreactors for use in a series of sorption/desorption batch tests. The data retrieved from the batch tests were used to determine sorption and desorption isotherms, from which the partitioning coefcients (K d and K ds ,respectively)andsorptionhysteresis (HI) index values were calculated. Sorption HI was calculated as follows: HI KK K ds d d (16.1) The subscript T (23°C) and C r (C r levelis0.5)refertospecicconditionsof constant temperature and residual solution phase concentration ratio, respectively. ThepartitioningcoefcientdeterminedfromthesorptionexperimentsisK d ,andthe partitioning coefcient determined from the desorption experiments is K ds .Samples were also collected for biomass particle size analysis. A typical sorption/desorption result is shown in Figure 16.5forthetwodifferent biomass oc suspensions. The suspension taken from the MBR had a mean particle sizeof10μm,whilethatoftheCBRhadameanparticlesizeof120μm.Inthis example the sorption/desorption experiment yielded K d and K ds values of 0.47 L/g and0.56L/gfortheMBRbiomass,and0.32L/gand0.61L/gfortheCBRbiomass, respectively. Using these values, the hysteresis index values for the MBR and CBR were 0.19 and 0.89, respectively. Results such as these suggest that the particle size inuenced the hysteresis index for EE2 sorption. Yi and Harper 27 foundthatasthe meanparticlesizeincreasedfrom10to230μm,theHIincreasednonlinearlyfrom approximately 0.2 to 0.9. This result showed that the biomass particle size can have a © 2008 by Taylor & Francis Group, LLC Chemical Processes during Biological Wastewater Treatment 371 dramatic effect on the entrapment of EE2 within activated sludge oc, which in turn may affect the ultimate fate of EE2. 16.5 BIODEGRADATION Biodegradation is likely due to cometabolic activity because PPCPs are not present in high enough concentration to support substantial biomass growth. This means that PPCP transformation is most likely to occur during exponential growth stages and during active degradation of the primary substrates present in wastewater. The published reports of cometabolism of PPCP are currently limited. Most of the pub - lished reports that concern cometabolism focus on the removal of xenobiotics that areproducedasaresultofindustrialandmilitaryactivity(e.g.,chlorinatedsolvents such as trichloroethylene, nitroaromatic compounds, explosives, dyes, polyurethane foams). These compounds may be present in the environment at much higher con - centrations than PPCPs are, but many industrial pollutants and PPCPs share some of thesamestructuralfeatures(i.e.,polyaromaticrings),sotheremaybecommonreac- ti onmechanisms.Itisalsoknownthatcometabolismisoftenaninitiatingreaction, producing intermediates that may be more biodegradable (and therefore would par- ti cipateinthecentralmetabolicpathways),orthatmaybesusceptibletoadsorption or polymerization reactions and rendered nonbioavailable (i.e., dead-end product). Quintana et al. 32 observed the cometabolic transformation of four acidic pharma- ceuticals in laboratory-scale experiments. Although cometabolism is likely when biodegradation is occurring, there is only limited information that clearly connects cometabolism with the removal of PPCPs. One interesting example comes from Alexy et al., 33 whofoundthateachof18antibioticswasnotbiodegraded,butsome 0 20 40 60 80 100 120 140 0 50 100 150 200 250 300 Aqueous EE2 (+g/L) Biomass-Associated EE2 (+g/g) MBR- desorp MBR-sorp CBR-sorp CBR - desorp Arrows Show Extend of Hysteresis Reprinted from Yi and Harper. 27 e effect of biomass characteristics on the partitioning and sorption hysteresis of 17α- ethinylestradiol. In press. Water Research (WR6011). Copyright (2007). With permission from Elsevier. FIGURE 16.5 Typical sorption and desorption isotherms for MBR and CBR biomass. © 2008 by Taylor & Francis Group, LLC 372 Fate of Pharmaceuticals in the Environment and in Water Treatment Systems partial biodegradation was observed when sodium acetate also was present. This sug- geststhatwhensodiumacetateisavailableasaprimarysubstrate,theantibioticsmay be subject to cometabolism. Biodegradation may sometimes result in the formation ofastablebyproduct.HaibandKummerer 34 found that diatrizoate (found in X-ray contrast media) was biodegraded aerobically to 3,5-diamino-2,4,6-triodobenzoic acid, whichwasnotfurtherdegradedbybacteria.Quintanaetal. 32 also found that biotrans- formationofketoprofenandbezabrateproducedmorestablemetabolites. Awidevarietyofmono-anddioxygenaseenzymescantransformxenobiotics during exponential growth conditions, 35 but biotransformation of pollutants in the absence of bacterial growth also may occur as a result of enzymes previously pro- ducedbydead(nonviable)bacteriaandasaresultofextracellularenzymesexcreted by viable bacteria. 36,37 Activated sludge communities are diverse and known to house awidevarietyofnonspecicmono-anddioxygenaseenzymesassociatedwithboth heterotrophic and autotrophic microorganisms. 38,39 There is circumstantial evidence linking nitriers to a unique capability to biologically (perhaps cometabolically) transform steroid estrogens such as EE2. Surveys of municipal WWTPs indicated that nitrifying sludges remove EE2 more efciently than those that do not nitrify. 40 Numerous experimental results further supported this contention: Vader et al. 41 degraded EE2 using nitrifying activated sludge, and they noted the presence of unidentied hydrophilic daughter products. Several groups 14,42–44 also biologically degraded EE2 using nitrifying mixed cultures. These combined results suggest that EE2 and NH 4 transformation rates are linked. AspecicEE2transformationmechanismmayinvolveammoniummonooxygenase (AMO),thekeyenzymethatcatalyzestheconversionofammoniatonitriteinnitri- fyingorganisms.Forexample,AMOisalsocapableofcometabolicallyoxidizing polycyclic aromatic rings. 45,46 TheactivesiteofAMOisburiedinthecoreofthe protein,wherefourneighboringB-helices provide two histidine and four glutamic acidsasironligands. 47,48 Onefaceofthedi-ironsitecontainsahydrophobicpocket and may be well suited for organic substrates like EE2. Yi et al. 14 showed that EE2 and NH 4 + are simultaneously degraded in an AMO-containing extract. Yi and Harper 43 proposed a conceptual picture linking EE2 removal and NH 4 + removal (Figure 16.6).AMOconvertsNH 3 to NH 2 OH in the presence of oxygen. This step requires reducing power that is regenerated as NH 2 OH is oxidized to NO 2 by hydroxylamine oxidoreductase. Electrons then enter a catalytic cycle involving a binuclear copper site located at the AMO active site. Oxygen reacts to convert the Cu(I)toCu(II),buttheoxygenremainsboundasperoxideion(O 2 - ). This oxygenated form of the enzyme then reacts with organic substrates to produce the Cu(II) form. Yi and Harper 43 evaluated the conceptual model shown in Figure16.6usingan enzymeextracttakenfroman enriched (notpure)cultureofnitriers.Theydeter- minedtheratioofEE2/NADHremovedbyincubatingEE2,NADH,andothercom- ponentsinthepresenceofanAMO-containingenzymeextract;themolarratioof NADH/EE2determinedduringtheincubationwas2.2,whichisconsistentwith theactionof monooxygenase-mediatedbiotransformationshowninFigure16.6. ThisresultshowsthatthecometabolicbiotransformationofEE2wasm onooxygen- as e mediated, as opposed to being dioxygenase mediated, because the NADH/EE2 © 2008 by Taylor & Francis Group, LLC [...]... (DOC), but clofibric acid and diclofenac were not eliminated and were discharged at a level of approximately 95% of their initial concentration; they did find, however, that the elimination in the anoxic region of the biofilm reactor improved the removal efficiencies of clofibric acid and diclofenac to values between 60 and 80% of their initial concentration Winkler et al.52 found that ibuprofen (as well... efficiencies of less than 10% at steady state These results imply that biodegradation is not likely to play a large role in determining the ultimate fate of synthetic antibiotics in conventional biological wastewater treatment systems © 2008 by Taylor & Francis Group, LLC 376 Fate of Pharmaceuticals in the Environment and in Water Treatment Systems Although a number of elucidating studies concerning biodegradation... in the sludge of a municipal water treatment plant contain © 2008 by Taylor & Francis Group, LLC 378 Fate of Pharmaceuticals in the Environment and in Water Treatment Systems integron-specific DNA sequences, so that their presence in this environment indicates that sludge is a specific location where genes are coming together and being distributed Tennstedt et al.64 found that 12% of the plasmids isolated... biologically, and the naproxen solution containing products of chlorination caused biomass sloughing and discharge from the bioreactor Zwiener and Frimmel51 investigated the biodegradation of three active compounds of pharmaceuticals (clofibric acid, ibuprofen, and diclofenac) in shortterm tests with a miniaturized upflow biofilm bioreactor with an oxic/anoxic configuration The biofilm reactor removed 85% of the. .. soils and sediments Applied Geochemistry 2003, 18, 955–972 © 2008 by Taylor & Francis Group, LLC 380 Fate of Pharmaceuticals in the Environment and in Water Treatment Systems 25 Martin, S.R Equilibrium and kinetic studies on the interaction of tetracyclines with calcium and magnesium Biophysical Chemistry 1979, 10, 319–326 26 Sobeck, D and Higgins, M Examination of three theories for mechanisms of cationinduced... sludge contained class 1 integron-specific sequences, and that these sequences contained genes that code for two chloramphenicol-resistance proteins 16. 7 CONCLUSION Overall, the removal of various classes of PPCPs depends of the chemical characteristics of the PPCPs in question, that of the sludge, and operating conditions of the WWTP Removal efficiencies at full scale vary considerably across the numerous... antibiotic-resistance genes for vancomycin (vanA) and ampicillin (ampC), and they found that, in municipal wastewater, the resistance gene vanA was detected in 21% of the samples, and ampC in 78% The presence of hospital wastewater also may affect antibiotic resistance rates Reinthaler et al.60 evaluated the resistance patterns of E coli in WWTPs and found that the highest resistance rates were found in E... vancomycin, ceftazidime, cefazolin, and penicillin G from municipal activated sludge They also estimated that the amount of vancomycinresistant enterococci in activated sludge to be approximately 16% (as a percentage of cultivable species), and the amount of cefazolin-resistant enterobacteriaceae in activated sludge biofilms to be approximately 19% (approximately 11% in the WWTP discharge) The vancomycin-resistant... coli strains of a sewage treatment plant that treats not only municipal sewage but also sewage from a hospital They also found that, among the antimicrobial agents tested, the highest resistance rates in the penicillin group were found for ampicillin (up to 18%) and piperacillin (up to 12%); in the cephalosporin group for cefalothin (up to 35%) and cefuroxime-axetil (up to 11%); in the group of quinolones... to 15%); and for trimethoprime/sulfamethoxazole (up to 13%) and for tetracycline (57%) They determined that more than 102 CFU E coli/mL reached the receiving water, and thus sewage treatment processes contribute to the dissemination of resistant bacteria in the environment Although antibiotic-resistant microorganisms are present in activated sludge, there are indications that the biological treatment . (notpure)cultureofnitriers.Theydeter- minedtheratioofEE2/NADHremovedbyincubatingEE2,NADH,andothercom- ponentsinthepresenceofanAMO-containingenzymeextract;themolarratioof NADH/EE2determinedduringtheincubationwas2.2,whichisconsistentwith theactionof monooxygenase-mediatedbiotransformationshowninFigure16.6. ThisresultshowsthatthecometabolicbiotransformationofEE2wasm. Group, LLC 380 Fate of Pharmaceuticals in the Environment and in Water Treatment Systems 25. Martin, S.R. Equilibrium and kinetic studies on the interaction of tetracyclines with calcium and magnesium Francis Group, LLC 378 Fate of Pharmaceuticals in the Environment and in Water Treatment Systems integron-specic DNA sequences, so that their presence in this environment indi- cates that sludge