Effectsofexplosiveexplosionshockwavepretreatmenton

EffectsofexplosiveexplosionshockwavepretreatmentonsludgedewaterabilityDayongChen⇑,JunYangStateKeyLaboratoryofExplosionScienceandTechnology,BeijingInstituteofTechnology,5SouthZhongguancunStreet,HaidianDistrict,Beijing100081,PRChinahighlightsExplosiveexplosionshockwavecanimprovesludgedewaterability.Theviscosityandparticlesizehaveanimportantroleonsludgedewaterability.Increasingexplosivedosageswillincreasesludgeturbidity.Highexplosivedosageislesseffectiveforthereductionofparticlesize.articleinfoArticlehistory:Received14March2012Receivedinrevisedform25May2012Accepted27May2012Availableonline1June2012Keywords:SludgeExplosiveexplosionshockwaveDewaterabilityParticlesizeViscosityabstractThepotentialbenefitsandmechanismofexplosiveexplosionshockwavepretreatmentonsludgedewa-teringtreatmentswereinvestigatedinthisstudy.Watercontentofsludgecakeaftercentrifugationwasusedtoevaluatesludgedewaterability.Particlesize,viscosity,turbidity,andmicrographweredeter-minedtoexplaintheobservedchangesinthepretreatmentprocess.Theresultsindicatedthattheopti-malpretreatmentcondition,generatingthelowestwatercontentofsludgecake,was25gexplosiveand96.7%originalsludgewatercontent.Thisconditionresultedinthereducedparticlesizeandviscosityaswellasincreasedturbidity.Particlesizeandviscositysignificantlycontributedtoenhancesludgedewa-terability.Micrographinvestigationindicatedthatexplosiveexplosionshockwavepretreatmentcouldrupturesludgeflocs,releasephysicallyboundwater,andextracellularsubstancesintothesolution,con-sequentlyenhancingsludgedewaterability.2012ElsevierLtd.Allrightsreserved.1.IntroductionActivatedsludgetechnologyisawidelyusedbiologicalmethodforwastewater(especiallymunicipalwastewater)treatment,butlargequantitiesofwaste-activatedsludgeareproducedinthepro-cess(Zhangetal.,2010).Acommoncharacteristicofdifferenttypesofsludgeistheveryhighwatercontent,thecolloidalandcompressiblenatureofthesludge(Mahmoudetal.,2011).Thisexcessivewaterincreasesthevolumeandthecosttotransportthesludgetothefinaldisposalsite.Theseproblemscanbereme-diedbysludgedewateringbecausethisprocessreducesthesludgevolume.Dewateredsludgeisalsogenerallymucheasiertohandle.However,sludgedewateringremainsthemostexpensiveandmostpoorlyunderstoodwastewatertreatmentprocess(Bruusetal.,1992).Dewateringisgenerallyperformedbyphysicalmeanswithmechanicalmethods,suchasvacuumfiltration,beltfilterpresses,dryingbeds,andcentrifugation.Theadditionofpolyelectrolytetosludgeispresentlythemostwidelyusedpretreatmentinwastewatertreatmentplants(WWTP)toimprovemechanicaldewatering(Fengetal.,2009).Thesludge,regardlessofthecondi-tioning,maintainsagel-likestructureandextremelyhighcom-pressibility,renderingdewateringaquitechallengingprocess(Citeauetal.,2011).Theuse,especiallytheoverdosage,ofpoly-mersmaycausevariousenvironmentalproblemsinthesuperna-tantofwatergeneratedduringthesludgedewateringprocess.Theresidualpolymersindewateredsludgecakesmayposelong-termrisktothesurroundingenvironment,especiallywhenthesludgecakesaresubjecttolandfillasthefinaldisposal,whichisveryexpensive(VanderRoestetal.,1999).Thus,variousalternativemethodshavebeenproposedtoim-provethesludgedewateringcharacteristics,includingtheadditionofFenton’sreagentpretreatment(Tonyetal.,2008),ultrasonica-tion(Naetal.,2007;Lietal.,2009;Fengetal.,2009),ultra-rapidfreezing(ParkerandCollins,1999),electrolysis-pretreatment(Yuanetal.,2011),hydrogenperoxide(Neyensetal.,2004),andfry-drying(Ohmetal.,2009),aswellasapplicationsofdryice(Jeanetal.,2001),seawaterandbrine(Liuetal.,2011),acid(Delinetal.,2011)andfungi(AhmadunandAbul,2007).Explosionsresultfromthealmostinstantaneousconversionofasolidorliquidintogasafterdetonationofanexplosivematerial.Detonationgas0960-8524/$-seefrontmatter2012ElsevierLtd.Allrightsreserved.⇑Correspondingauthor.Tel:[phone];fax:[phone].E-mailaddress:[e-mail](D.Chen).BioresourceTechnology119(2012)35–40ContentslistsavailableatSciVerseScienceDirectBioresourceTechnologyjournalhomepage:(WightmanandGladish,2001).Effectsofexplosiveexplosionshockwavepretreatmentonsludgedewateringhasnotbeenexam-inedinenvironmentscienceandengineeringuntilrecently,althoughthesepotentiallybeneficialtechniqueshavebeenappliedinotherindustrialfields,suchasengineeringblasting(Chuetal.,2012),explosionworking(Koehler,1952),materialsscience(RahmanandItoh,2011),andfoodscience(Hamashimaetal.,2011),amongothers.Anewpretreatmentmethod,i.e.,pretreatingsludgewithexplo-siveexplosionshockwavewasproposedinthepresentstudy.Thefeasibilityofthisprocesswasalsoexamined.Theobjectivesofthisresearchweretoassessthevariationinthesludgephysicalcharacteristics,suchasdewaterability,particlesize,viscosity,tur-bidity,whenexplosiveexplosionshockwavepretreatmentwasimplemented.Therelationshipbetweendewat