Nonylphenol deca-ethoxylate removal from wastewater by UV/H2O2: Degradation kinetics and toxicity effects

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Maurizio

Carotenuto

a

_,

_Giovanni

_Libralato

b,∗

_,

_Hatice

_Gürses

a

_,

_Antonietta

_Siciliano

b

_,

Luigi

Rizzo

c

_,

_Marco

_Guida

b

_,

_Giusy

_Lofrano

d

a_Dipartimento_di_Chimica_e_Biologia_“Adolfo_Zambelli”,_Università,_degli_Studi_di_Salerno,_via_Giovanni_Paolo_II_132,_84084,_Fisciano,_SA,_Italy b_Department_of_Biology,_University_of_Naples_Federico_II,_Complesso_{Universitario}_di_Monte_S._Angelo,_Via_Cinthia_ed._7,_80126,_Naples,_Italy c_Department_of_Civil_Engineering,_University_of_Salerno,_via_Giovanni_Paolo_II_132,_84084,_Fisciano,_SA,_Italy

d_Centro_Servizi_Metrologici_e_Tecnologici_Avanzati_(CeSMA),_University_of_Naples_Federico_II

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received17December2018

Receivedinrevisedform28January2019 Accepted30January2019

Availableonline3February2019 Keywords:

Nonylphenolethoxylates Wastewater

Advancedoxidationprocesses Radicalscavengers

Ecotoxicology

a

b

s

t

r

a

c

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Nonylphenolethoxylated(NPEOs)nonionicsurfactantshavebeenincreasinglyusedindifferent indus-trial,commercialanddomesticapplications.Unfortunately,theyareclassiﬁedasendocrinedisrupting chemicals(andalsoconsideredascontaminantsofemergingconcern)havingadverseeffectsonanimal andhumanreproduction.Thetreatmentofnonylphenol-decaethoxylated(NP-10)viaH2O2/UV-C

pro-cessatdifferentreactiontimes(5,10,20,40,80min)andH2O2concentrationswasinvestigated.After

80mintreatmenttheremovalratesofNP-10solution(initialconcentration100mg/L)indeionizedwater were88%,97%and98%for10,20and100mg/LofH2O2respectively.Thesameexperimentalconditions

wereappliedtorealwastewaterspikedwith100mg/LofNP-10showingthefollowingremovalrates: 84%,98%and99%,respectively.ThepossiblecontributionofdifferentradicalstoNP-10degradationby H2O2/UV-Ctreatmentwasinvestigatedbyevaluatingtheeffectofdifferentradicalscavengers(namely

NO3−,NaCl,Na2SO4,Na2CO3,KH2PO4andphatalate).Toxicitydata(Aliivibrioﬁscheri,Raphidocelis

sub-capitataandDaphniamagna)ontreatedsolutionsandwastewaterhighlightedthepresenceofresidual toxicityinallsamplesevidencingthatnocompletemineralizationoccurred.

1. Introduction

Nonylphenol ethoxylates (NPEOs) are surface active agents

(surfactants)thatarepartofthebroadercategoryofsurfactants

knownasalkylphenolethoxylates(APEs).Dependingonthedegree

ofethoxylation,NPEOspresentoctanol-waterpartitioning

coefﬁ-cients(logKow)rangingfrom4.20to4.50changingitssuitability

for the speciﬁc use, generally, at relatively low cost (Mcleese

etal.,1981;Ciabattietal.,2009).Thesecharacteristicsmakethem

suitablefordifferentindustrial,commercialanddomestic

applica-tionsinsurfacecleaner,lubricant,shampoo,anddetergents(CEPA,

1999).NPEOscanreachfromtenstohundredsofmg/Linindustrial

efﬂuents(ZhouandZhang,2017;Chokweetal.,2017).

∗ Correspondingauthorat:DepartmentofBiology,UniversityofNaplesFederico II,ComplessoUniversitariodiMonteS.Angelo,ViaCinthiaed.7,80126,Naples,Italy.

E-mailaddresses:mcarotenuto@unisa.it(M.Carotenuto),

giovanni.libralato@unina.it(G.Libralato),gurses.hatice90@gmail.com(H.Gürses), antonietta.siciliano@unina.it(A.Siciliano),l.rizzo@unisa.it(L.Rizzo),

marguida@unina.it(M.Guida),glofrano@unisa.it(G.Lofrano).

Althoughthe toxicity ofNPEOs varies,rangingfrom

moder-atelytoxictotoxictoﬁshandaquaticorganismsonanacutebasis

and increasingas thelengthoftheethoxylatechain(molecular

weight)decreases,agrowingconcernisposedbytheirby-products,

mainly nonylphenol (NP), because of theirpotential estrogenic

effecttotheaquaticbiota(Chenetal.,2007).Accordingto

NP-10safetydatasheetandPAN-Pesticedatabase(2019),onlyacute

toxicityeffectsareavailablesuggestinglow-mediumtoxicity

lev-els,neverthelessitspotentialactivityasendocrinedisruptor(i.e.

variousbacteriamedianeffectconcentration(EC50)>1000mg/L;

EC50=17mg/LforScenedesmusquadricaudaand15mg/LforLemna

minor; lethal median concentration (LC50)=9.3–21.4mg/L and

20.9mg/LforDaphniamagnaandGammaruspulex(48h),

respec-tively;ﬁshLC50=3.8-7.7mg/LforPimephalespromelas(96h)and

16.4mg/LforPoeciliareticulata(48h)).

NPisapriorityhazardoussubstance(PHS)undertheEU’sWater

FrameworkDirective(WFD)andisconsideredanemergingorganic

pollutantthatmimicsthenaturalhormone17␤-estradiol

interfer-ingwithorganisms’reproduction(LeeandLee,1996;Soléetal.,

2000;Reisetal.,2014).InviewofNPEO’stoxicity,theEuropean

UnionunderDirectiveNo.,2003/53/ECprohibitedtheuseofNPand

https://doi.org/10.1016/j.psep.2019.01.030

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Fig.1.a)Verticalreactorconﬁguraton;b)Horizontalreactorconﬁguration.

NPEO’sandrecommendedtheirreplacementwithcostlyalcohol

ethoxylates.Currently,manufacturerswithintheEUcannot

pro-ducetextilesorclothingcontainingNPorNPEO,butthisdoesnot

meanthattheycanbefoundinwastewatergeneratedfromthe

wash-offofextra-UEmanufacturedclothes(Lofranoetal.,2016a,b).

TheEU 2004ban onmanufactureof textiles and clothing

con-tainingNP(EOs)ledtoafallinNPinUKwaterbodies,butupto

20%oftheNPlevelsfoundinUKwaterbodiescomesfrom

wash-offfromimportedtextilesandclothing(UKEnvironmentAgency,

2013).

Moreover,NPstilloccursintheaquaticenvironmentwith

con-centrationsvaryingwidelyinsurfacewaterfromtensofng/L(Brix

etal.,2010)todozensofmg/L(Pengetal.,2008).Duetolowcostand

higefﬁciency,NPEOarestillinuseindevelopingcountrieswhere

signiﬁcantlyhighconcentrations(uptosometensofmg/L)are

detectedintheefﬂuentofindustrialwastewatertreatmentplants

(WTPs)(Maoetal.,2012).Theyarebeingdischargedcontinuously

intotheenvironmentandthusapropermanagementofsuchkind

ofwastewateris urgentlyrequired.Unfortunately,conventional

biological(such asactivatedsludge)processes arenot effective

inthetreatmentofsohigh(tensofmg/L)NPEOconcentrations,

thereforeasuitableadditionaltreatmentisnecessarytoimprove

theirreduction/removal.Accordingly,variousprocesseshavebeen

investigatedsuchasozonation(Lenzetal.,2004;Ledakowiczetal.,

2005),adsorption(Fanetal.,2011)andadvancedoxidation

pro-cesses(AOPs).AmongAOPs,dfferentmethodshavebeenstudied

inNPEOdegradation,namelygammaradiation/H2O2(Abbasetal.,

2015),UVC/H2O2,photo-Fenton(Karcietal.,2013),(S2O28−

)/UV-C(Olmez-Hancietal.,2013),heterogeneousFenton-likeprocess (Shahbazietal.,2014),heterogeneousphotocatalysis,

eletrochem-icaloxidation andphoto-assisted electrochemicaloxidation (Da

Silvaetal.,2015).However,althoughAOPsareknowntoaffect

water/wastewatertoxicity(Rizzo,2011;Lofranoetal.,2017),only

infewcasestheﬁnalefﬂuentwascheckedforresidual

ecotoxic-ity(Lenzetal.,2004;Ledakowiczetal.,2005;Karcietal.,2013;da Silvaetal.,2015),and,frequently,onlyonebiologicalmodelwas

usedlimitingdatainterpretationforecologicalriskassessmentof

NPEOs(Karcietal.,2013).

AmongstAOPs,H2O2/UV-Cisa well-establishedprocess,not

sensiblyaffectedbypH(Parsons,2004).

Inthepresent study,thedegradationofthenonionic

surfac-tantTergitolTM_type_NP-10_(CAS_number:_{127087-87-0),}_used_in

cleanersanddetergents,paperandtextileprocessing,paintsand

coatings,agrochemicalsandmetalworkingﬂuidwasinvestigated

byusingH2O2/UV-Cprocess.Experimentswerecarriedoutintwo

reactorconﬁgurationstoevaluatetheeffectofi)deionizedwater

andspikedrealwastewater,ii)scavengers(CO3−andphtalates)

andintereferringsubstances(NO3−andSO4−).Theecotoxicityof

untreatedandtreatedsampleswasinvestigatedconsideringa

bat-teryoftoxicitytests(Aliivibrioﬁscheri,Raphidocelissubcapitata,and

Daphniamagna).

2. Materialsandmethods

2.1. Chemicalsandanalyticaltechniques

TergitolTM_type_NP-10_(C

35H64O11)waspurchasedfrom

Sigma-Aldrich(USA).Theformulationwasacolourlessandhighlywater

soluble.Ultrapurewater(UW)(Milli-Q®_system_Elix_10,_Merck

Mil-lipore,Billarica,MA,USA)wasusedforpreparationoftestsolutions.

AstocksolutionofH2O2 (30%w/w;SigmaAldrich,St.Louis,MO,

USA,)wasused.

A high-performance liquid chromatography (HPLC) system

equippedwitha module pump(Thermo SpectraSystem P2000)

and an UV–vis detector (Thermo SpectraSystem) was used for

TergitolTM_{determination.}_TergitolTM_separation_was_achieved_by

HypersilODSC18(150mm×4.6mm,5␮mparticlesizeThermo

FisherScientiﬁc,Waltham,MA,USA)reversedphasecolumnusing

amobilephaseofmethanol:water(90:10,v/v) ataﬂowrateof

1.0mL/min.Injectionvolume,absorbancewavelength,excitation

andemissionwavelengthsweresetat30␮L,275nm,230nmand

310nm, respectively. TergitolTM _{concentration} _was _determined

accordingtothecalculationofpeakareasbyexternalcalibration.

Thelimitofdetectionwasidentiﬁedassignal-to-noiseratio(S/N)

equalto0.050mg/L.

Wastewater, originate from a municipal wastewater

treat-mentplant(WWTP),locatedinCampaniaregion(Italy)receiving

wastewater collected from urban households, agro-industries,

zootechnicalactivities,hospicesandotherfacilities.TheWWTPhad

anaveragecapacityof300,000p.e.,andanaverageﬂowrate

rang-ingof45,000m3_d−1_._The_treatment_process_includes:_i)_Mechanical

pre-treatment (screening and pumping stations, grit and oil

removal);ii)Rainwatersection(primarysedimentationand

aer-atedstorage);iii)Secondarytreatment(nitriﬁcation-denitriﬁcation

andﬁnalsettling);andiv)Tertiarytreatment(gravityﬁltrationon

sand),anddisinfectionwithperaceticacid.Wastewatersamples

werecharacterisedforbiologicaloxygendemand(BOD5),

chemi-caloxygendemand(COD),totalsuspendedsolids(TSS),nitrogen

asammonia(N-NH3),nitrate(NO3−),andnitrite(NO2−),andtotal

phosphorus(TotalP)accordingtoAPHA(2012).

2.2. Experimentalset-up

H2O2/UV-Cadvancedoxidationexperimentsincludedtwo

con-ﬁgurations:a)UV-Clamp,encasedinaquartztube,axiallycentered

respecttothereactorandimmersedintothesolution(vertical

con-ﬁguration,VC);b)UV-Clamphorizontallypositioned10cmabove

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trations(10,20,100mg/L)andreactiontimes(5,10,20,40,80min)

lookingforthebestoperativeconditionsofH2O2/UV-Cprocessin

deionizedwater(DW),comparingVCandHCconﬁgurationsforthe

degradationofTergitolTM_{concentration}₍₁₀₀_mg/L)._The_H

2O2

/UV-C process wascarried out atroom temperature(25±2◦C) and

naturalsolutionpH(5.5).Controlexperimentswerealsoconducted

toobserveTergitolTM_degradation_in_the_absence_of_either_UV-C_or

H2O2.

Thesecondexperimentalscenarioincludedtheserialaddition

totestingsolutionofcompoundsusuallyworkingasscavengers

ofhydroxyl radicals: (NaCl (1000mg/LCl–); Na2CO3 (300mg/L

CO32–), KH2PO4 (10mg/L PO43), NaNO3 (50 and 500mg/LNO3),

852mg/Lofphthalate(correspondingto1000mgO2/LofCOD)as

wellasinterferingsubstancesNa2SO4(500mg/LSO42–),inorderto

evaluatetheirpotentialeffects.

In the third experimental scenario, real wastewater (WW)

taken from a wastewater treatment plant (BOD5=18mg/L;

COD=48.5mg/L;TSS=46mg/L;N-NH3=1.42;N-NO3−=0.25mg/L;

N-NO2-=3.34mg/L;totalP=1.23mg/L)wasspikedwith100mg/L

TergitolTM_evaluating_the_inﬂuence_of_matrix_on_the_behaviour_of

theprocess.

Analysiswascarriedoutatleastinduplicateandreportedas

meanandsemi-dispersion.

Afterwithdrawalofthesamples,theresidualH2O2was

imme-diately quenched with few mL of catalase at 0.1g/L to allow

subsequenttoxicityanalysis.

2.4. Ecotoxicity

ToxicitytestswithA.ﬁscheri,R.subcapitata,andD.magnawere

carriedoutontreated(100mg/LofTergitolTM_in_deionized_water

andrealwastewaterspikedwith100mg/lofTergitolTM_after₈₀_min

ofphoto-oxidationtreatment)anduntreatedwastewatersamples

TergitolTM_._According_to_quality_assurance_and_quality_control

pro-cedures,bioassaysincludedtheassessmentofnegativeandpositive

controlsaccordingtothecorrespondingstandardmethod.In

par-ticular,theacutebioluminescenceinhibitionassaywascarriedout

usingA.ﬁscheri(NRRL-B-11177)accordingtoISO(2007).The

lumi-nescencewasmeasuredwitha Microtox® _analyser_(Model_500,

AZUREnvironmental)after5and15minat15◦C.Testswerecarried

outintriplicate.DatawereanalysedwithMicrotoxOmnisoftware

andtheresultexpressedaspercentageofbioluminescence

inhibi-tion.

The chronic growth inhibition test with R. subcapitata was

carriedoutaccordingtoISO(2012).Cultureswerekeptin

Erlen-meyer ﬂasks. The initial inoculum contained 104 _cell/mL. _The

speciﬁcgrowthinhibitionratewascalculatedconsidering6

repli-catesexposedat20±1◦Cfor72hundercontinuousillumination

(6000lx).Effectdatawereexpressedaspercentageofgrowth

inhi-bition.

Newborndaphnids(<24hold)wereexposedtosample

accord-ingtotheISO6341method.Daphnidsweregrownat 20±1◦C

revealedsigniﬁcantdifferencesamongtreatments,post-hoctests

werecarriedoutwithTukey’stest.Statisticalanalyseswere

per-formedusing Microsoft® _Excel _{2013/XLSTAT©-Pro}_(Version _7.2,

2003,Addinsoft,Inc.,Brooklyn,NY,USA).

Finally, toxicity datawere integrated accordingto Persoone

etal. (2003)and Lofranoet al.(2016a,b). Thehazard

classiﬁca-tionsystemisbothbasedonPEorTU50includesaClassIforPE

b20%(score0)(orTU50<0.4),ClassIIfor20%_≤PEb50%(score

1)(or0.4<TU50<1),ClassIIIfor50%≤PEb100%(score2)(or

1<TU50<10),ClassIVwhenPE=100%inatleastonetest(score

3)(10<TU50<100)andaClassVwhenPE=100%inallbioassays

(score4)(TU50>100).Finally,theintegratedclassweightscorewas

determinedbyaveragingthevaluescorrespondingtoeach

micro-biotestclassnormalisedtothemostsensitiveorganism(highest

score).

3. Resultsanddiscussion

3.1. Kineticstudies

ExperimentsonTergitolTM_at₁₀₀_mg/L_carried_out_under_dark

(100mg/LofH2O2)provedthattheuseofH2O2appliedalonedid

notallowanyreduction inNP-10concentration(Fig.2a,b).

Pre-liminarymeasurementsofUVabsorbancespectra(200–400nm)

ofuntreatedTergitolTM_indicated_two_distinct_absorbance_bands_<

300nm:i)apeakat224nmandii)anotherpeakat275nm

charac-teristicofmanyphenoliccompounds(Kimetal.,2005),evidencing

thatTergitolTM _absorbs_light_in_the_UV _C _region._The_photolysis

of100mg/Lof TergitolTM _resulted_in _20%_and_30%_removal

efﬁ-ciencyafter80mininHCandVC,respectively(Fig.2a,b).InKarci

etal.(2013),theUV Cphotolysisof100mg/LNP-10wasevaluated

ina3250mL-capacity,horizontallypositionedandbatch-operated

cylindricalphotoreactorwiththeUV Clightsource(40Wlamp,

1.4×10−5 EinsteinL−1 s−1at253.7nm)locatedinthecenterof

thephotoreactorina quartzsleeve.Accordingtotheirresultsa

removalrateof92%wasobtainedafter120min,evidencingthat

theefﬁciencywasstronglyaffectedbylamppower,geometryand

reactiontime.

Chen etal. (2007)evaluated thephotolysis of200mg/L

NP-10usinga125Whigh-pressuremercurylampwiththeprimary

wavelength of 365nm; an absorbance peak at 270nm

corre-sponding to the broken benzene ring was observed after 6h

irradiation.

H2O2/UV-CprocessresultedinaTergitolTMremovalof87,90

and 99%in VCconﬁguration after80mintreatment, whereas a

removalof79,87and95%wasachievedinHCconﬁgurationafter

thesametreatmenttime,with10,20and100mg/LofH2O2,

respec-tively.

The rather poor NP-10 removal kinetics (k

NP-10=0.046±0.0007min−1)andefﬁcienciesobtainedviaphotolyisis

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concentra-Fig.2.KineticcurvesofTergitolTM_(initial_{concentration}₁₀₀_mg/L)_under_different processes:a)verticalconﬁguration;b)horizontalconﬁguration.

Table1

Kineticconstants±standarddeviationsforTergitolTM_degradation_by_H

2O2/UV-Cin VCandHCconﬁgurations,respectively.

H2O2dose(mg/L) kVC(min−1) kHC(min−1)

10 0.024±0.002 0.024±0.003

20 0.051±0.003 0.030±0.003

100 0.150±0.007 0.074±0.008

tioninaccordancewiththeﬁndingsofKarcietal.(2013)which

reportedthat thehighest NP-10removal ratecoefﬁcient(k

NP-10=0.59±0.030min−1)wasachievedwithH2O2/UV-Cprocessat

aH2O2concentrationof340mgL−1

AsshowninTable1,TergitolTM_abatement_rates_increased_upon

increasingtheinitialH2O2 concentrationsfrom10 to100mg/L,

showingkineticconstantshigherinVCcomparedtoHC,except

ataninitialoxidantconcentrationof20mg/L.Thepositiveeffect

ofincreasingH2O2concentrationshasalreadybeenevidencedin

formerrelatedstudies(Arslan-Alaton,2010)andwasattributedto

theenhancedHO•production.

Inthepresentstudyafter20minofphotoxidationwith100mg/L

ofH2O2theremovalof100mg/LNP-10inVCandHCsetupreactor

was89%and82%,respectively.

3.2. Intereferingcompounds

Under the operating conditions described above (100mg/L

TergitolTM_and₁₀₀_mg/L_H

2O2),noneoftheintereferingsubstances

Fig.3.Effectsof:a)phatlatesandb)nitrateonphotoxidationrateofTergitolTM_in VCreactor,overthetime.

(NaCl, Na2CO3, KH2PO4, Na2SO4) showeda signiﬁcanteffect at

theinvestigatedconcentrations,butphthalatesandonlypartially

nitrate.Asmatteroffact,17%ofremovalofTergitolTM_was_achieved

after80minofphotoxidationinpresenceof852mg/Lofphthalate

(Fig.3a).

The irradiation of nitrate-rich water leads to nitrite

forma-tionwithareactionquantumyielddependentontheexcitation

wavelength,temperature,pHandnitrateconcentration(Mackand

Bolton,1999).Photolysisofnitrateandnitriteresultsinthe

forma-tionofreactivespeciessuchasthe·OHradicalbutalsoNO·,NO2·,

ONOO_·.AsshowninFig.3b,theremovalkineticsslightlyimproved

byincreasingthenitrateconcentration.

ItispossiblyduetotheOHradicalproductionfromtheNO3−

absorptionofUVaccordingtothefollowingreaction:

NO−3+h+H+→·NO2+·OH

Assumingthatthemolarratiobetweennitrateandhydroxyl

radicalswas1:6.6and1:0.65for50mg/Land500mg/Lofnitrate

respectively,itcanbestatedthatintheﬁrstcasethereisaslight

scanvengereffectofnitrate,whereasinthesecondonethereis

acontributionofradicalnitritetotheoxidationreactionatshort

time.

Unlikeofourresults,thepresenceofnitrate(5mg/L)affected

removal of bisphenol A (BPA) in previous experiments with

UV/H2O2(Parketal.,2014).However,itworthtonoticethatthe

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Fig.4.a)Comparisonbetweenphotoxidationremovalof100mg/LTergitolTM_from DWandWWinVCandHCreactoratthedifferentvaluesofH2O2concentrations; b)comparisonbetweenphotoxidationkineticcurvesof100mg/LofTergitolTM_from DWandWW,inVCreactor.DashedlinesarethecurveﬁtforDWsampleswhereas dotlinesarethecurveﬁtofWWsamples.

1:23and1:46correspondingto150mg/land300mg/lofhydrogen

peroxiderespectively.

3.3. Realwastewater

Accordingtotheresultsachieved withdeionized water,the

removalofTergitolTM_in_VC_reactor_was_higher_compared_to_HC

reactorinrealwastewaterforalltheH2O2concentrations(Fig.4a).

Therefore,thekineticstudyfortheevaluationoftheinﬂuenceof

thewatermatrixwascarriedonlyinVC.Asexpectedthe

kinet-ics contant in DW (0.0184±0.0013min−1, 0.024±0.004min−1,

0.072±0.004min−1 for 10, 20 and 100mgL−1 of H2O2

respec-tively) were higher than in WW (0.0096±0.0003min−1,

0.0156_±0.0011min−1, 0.045_±0.002min−1 for 10, 20 and

100mgL−1ofH2O2respectively).ByincreasingtheH2O2

concen-tration from10 to 100mg/L, after 80min of photoxidationthe

TergitolTM_removal_was_about_76.97%,_85.76%,_99.69%_and_53.43%,

71.31%, 97.28% in DWand WW, respectively. After50min,the

treatmentwith100mg/lofH2O2carriedoutinDWachievedabout

97% ofTergitolTM _removal,₃₀_min_more _of _{photoxidation}_were

requiredtoachievethesamevalueofTergitolTM_removal_in_WW.

Fig.5. Toxicity(asTU50)ofTergitolTM_solutions₍₁₀₀_mg/L)_treated_with_UV-C (VC)atthreeincreasingconcentrationsofH2O2(NP-10=0mg/L;C-10=10mg/L; C-20=20mg/L;andC-100=100mg/L)assessedconsideringA=A.ﬁscheri,B=R. sub-capitata,andC=D.magna;datawithdifferentletters(a–b)aresigniﬁcantlydifferent (Tukey’s,p<0.05).

3.4. Ecotoxicologytests

3.4.1. Deionizedwater-basedsolutions

ToxicitydataonDW-basedsolutionsspikedwith100mg/Lof

NP-10andafter80minofphotoxidationtreatmentwithUV-C(VC)

atincreasingH2O2concentrations(NP-10=0mg/L;C-10=10mg/L;

C-20=20mg/L;andC-100=100mg/L)weresummarizedinFig.5

(A–C).Resultsshowedspecies-speciﬁceffectswithincreasinglevel

oftoxicitydisplayedbyR.subcapitata<A.ﬁscheri<D.magna.

Bac-teria(Fig.5A)didnotshowanysigniﬁcanttoxicityremovalafter

C-20andC-100,andaslighttoxicityincreaseafterC-10.Microalgae

(Fig.5B)presentedrelativelylowtoxicityeffectswithasigniﬁcant

reductionoftoxicityfrom31%(TergitolTM₎_to_1%_(C-10),_while

toxi-cityincreasedinC-20(8%)andC-100(39%).InthecaseofD.magna

(Fig.5C),thetoxicitywassigniﬁcantlyhighercomparedtoFig.5A

andB,especiallyafterC-100treatment.Nosigniﬁcantreduction

oftoxicitywasdetectedafterTergitolTM_treatment,_nevertheless

itwassigniﬁcantlyremoved(>90%).AccordingtoLofranoetal.

(2016a,b)andPersooneetal.(2003),toxicitydatawereintegrated.

Samplesweredeemedaspresentingbetween“slightacute

toxi-city”and“acutetoxicity”withahazardclassiﬁcationscoreof1.3

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Fig.6.Toxicityeffects(as%ofeffect)ofwastewatersamplesspikedwith100mg/L ofNP-10andtreatedwithUV-CatthreeincreasingconcentrationsofH2O2 (C-10=10mg/L;C-20=20mg/L;andC-100=100mg/L)assessedconsideringA=A. ﬁscheri,B=R.subcapitata,andC=D.magna;datawithdifferentletters(a–b)are signiﬁcantlydifferent(Tukey’s,p<0.05).

Resultsstatedthat TergitolTM _{mineralization}_was_not _complete,

andby-productscanstillexertanadverseeffectontarget

biolog-icalmodels.Similarly,itwasobservedinKarcietal.(2013)were

acutetheH2O2/UV-Cprocessultimatelyresultedinahigheracute

inhibitoryeffect(27%inhibition)thantheoriginalNP-10solution.

3.4.2. Wastewaterbasedexperiments

ToxicitydataonrealWWspikedwith100mg/LofTergitolTM_and

after80minofphotoxidationtreatmentUV-C(atincreasingH2O2

concentrations (NP-10=0mg/L; C-10=10mg/L; C-20=20mg/L;

andC-100=100mg/L)inVCreactor,after80min,were

summa-rizedinFig.6(A–C)expressedaspercentageofeffect.Thetoxicity

ofwastewaterperse,beforespiking,induceda12%,10%and15%

effectinA.ﬁscheri,R.subcapitataandD.magna,respectively.These

backgrounddatawereusedtonormalizethevaluesreportedin

Fig.6(A–C).AfterthephotoxidationtreatmentinpresenceofH2O2

increasingconcentrations,toxicityvalueswereonlyslightlyhigher

thaninDW(Fig.5)forA.ﬁscheri(Fig.6A)andR.subcapitata(Fig.6B),

whiletoxicityinD.magna(Fig.6C)wasreducedespeciallyfor

C-10andC20,whileresidualtoxicitycanbedetectedforC-100(i.e.

thetoxicityinFig.6wasexpressedas%ofeffectandnotasTU50

likeinFig.5).Inallcases,thebestperformancewasobtainedwith

10mg/LofH2O2.AccordingtoLofranoetal.(2016a,Lofranoetal.,

2016bandPersooneetal.(2003),toxicity datawereintegrated.

Samplesweredeemedaspresentingbetween“acutetoxicity”and

“highacutetoxicity”withahazardclassiﬁcationscoreof2.7(2(A.

ﬁscheri)+3(R.subcapitata)+3(D.magna)]/3(D.magna)).

4. Conclusions

Promisingremovalefﬁciency(upto99%)wasobservedafter

UV-C/H2O2 processconsideringtheverticalconﬁgurationofthe

reactorafter80minofreactiontimeofTergitolTM spiked

deion-izedwater.Similarly,inTergitolTMspikedwastewaters,theremoval

efﬁciencywasupto96%afterUV-C/H2O2processconsideringthe

verticalconﬁgurationofthereactorafter80min.InbothTergitolTM

spikeddeionizedwaterandrealwastewater,theefﬁciencyof

post-treatmenttoxicityreduction/removalremainedpoor,mainlydue

toreactionby-productsevidencingmedium-highlevelsofresidual

toxicity.Thus,furtherresearchisneededtooptimizethetreatment

processschemetoimprovetheﬁnalecotoxicologicalqualityofthe

efﬂuent.

Thecharacterizationofthedegradationproductscouldhelpto

theestimationoftheircontributiontotheoveralltoxicity.Ifthe

degradationproductsofTergitolwouldbebiodegradables,a

subse-quentbiologicaltreatmentstepcouldbeintegratedfortheremoval

of organicmatterand residualtoxicity after80min-H2O2/UV-C

treatment.

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