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1、1,An Introduction to Urban Water and Wastewater Treatment Technologies,2,Contents,1.Contaminants in Water 2.Contaminant Sources and Treatability 3.Best Available Technologies 4.Trend of Development,3,1.Contaminants in Water,1.1 Target of Water Quality Control,Wastewater Discharge Regulation,Key poin
2、t:Protection of human health,4,1.2 Capacity of Water EnvironmentA simple calculation,Ci:Concentration of contaminant iMi:Mass of contaminant i in waterV:Water volume,Mi0:Mass of contaminant i receivedMir:Mass of contaminant i assimilated(removed)by the water body itself(self purification),5,1.2 Capa
3、city of Water EnvironmentWater quality criteriaThis is equivalent toMir is a measure of the environmental capacity,Cis:Standard for contaminant i,Mis:Maximum permissible mass of contaminant i in water,6,1.3 Water Environmental StandardAmerican standard:Clean Water Act(CWA)Ambient Water Quality Crite
4、ria for the Protection of Human HealthAquatic Life CriteriaNutrient Criteria,7,1.3 Water Environmental StandardAmerican standard:Clean Water Act(CWA)The NRWQC 2002 includesCriteria for priority toxic pollutants:120 items(15 for inorganic,105 for organic pollutants)Criteria for non priority pollutant
5、s:45 itemsCriteria for organoleptic(taste and odor)effects:23 itemsDownloadable athttp:/wqcriteria.html,8,1.3 Water Environmental StandardChinese standard:Environmental Quality Standards for Surface Water(GB 3838-2002)Fundamental parameters(地表水环境质量标准基本项目标准限值):24 itemsSupplemental parameters for sour
6、ce water for community water supply(集中式生活饮用水地表水源地补充项目标准限值):5 itemsSpecific parameters for source water for community water supply(集中式生活饮用水地表水源地特定项目标准限值):80 items,9,表1 地表水环境质量标准基本项目标准限值(单位:mg/L),10,表1 地表水环境质量标准基本项目标准限值(单位:mg/L),11,表1 地表水环境质量标准基本项目标准限值(单位:mg/L),12,表2 集中式生活饮用水地表水源地补充项目标准限值(单位：mg/L),13,
7、表3 集中式生活饮用水地表水源地特定项目标准限值(单位：mg/L),14,表3 集中式生活饮用水地表水源地特定项目标准限值(单位：mg/L),15,表3 集中式生活饮用水地表水源地特定项目标准限值(单位：mg/L),16,1.4 Pollutants of Public ConcernIndicative parametersSuspended solids:SSDissolved solids:TDS(salinity)Organic substances:COD,BOD,TOC,UV Dissolved oxygen:DOAcidity:pHNutrientsNitrogen:TN,NH3
8、-N,NO3-N,NO2-N Phosphorous:TP,Portho,Ppoly,Poranic,17,1.4 Pollutants of Public ConcernSynthetic organic chemicals(SOCs)Industrial products such as PCBs(Polychlorinated biphenyls)Industrial byproducts such as DioxinPesticides and herbicides DBP precursors Natural organic matter(NOM)such as humic acid
9、s etc.Persistent organic pollutants(POPs)DDT,PCBs,PAHs,Hexachlorobenzene,Dioxins,Furans,18,1.4 Pollutants of Public ConcernEndocrine disruptive chemicals(EDCs)Heavy metals such as Cr,Pb etc.PCBs,hormones,dioxinsOrgano-chlorinated pesticidesMicroorganismsGiardiaCryptosporidiumViruses and bacteria,19,
10、2.Contaminant Sources and Treatability,2.1 Contaminant SourcesPoint sources:Sources of pollutants from a discrete location such as a pipe,tank,pit,or ditch.Non-point sources:Source of pollutants from a number of points that are spread out and difficult to identify and control.Non-point sources attri
11、bute a great deal to water pollution:Nutrients,pesticides,NOMCertain POPs and EDCs,20,2.2 Treatability of PollutantsThe treatability of pollutants depends on theirSizeSuspendedColloidalSolubleChemical propertiesOrganicInorganicBiodegradabilityBiodegradableBio-non-degradable,21,Water quality and trea
12、tability matrix,22,Domestic wastewater as an exampleMethods of pollutants classificationSuspended and soluble:using a 0.45 mm filterSettleable and non-settleable:plain settling for 2 hoursCoagulable and non-coagulable:coagulation and settlingSecondary treatment:activated sludge process(oxidation dit
13、ch),23,24,2.3 Limitation of Conventional TreatmentConventional treatmentTypical process for water treatment:Coagulation sedimentation filtration chlorination Typical process for wastewater treatment(activated sludge process):Screening primary settling biological unit secondary settling chlorination,
14、25,2.3 Limitation of Conventional TreatmentPollutants that can be removedSuspended solidsColloidal matterBiodegradable organic matterBacteria and viruses Pollutants that cannot be removedMost of the dissolved solidsBio-non-degradable organic matterChlorine persistent microorganisms(e.g.Cryptosporidi
15、um),26,3.Best Available Technologies,3.1 Strategic Considerations on the Selection of Available TechnologiesConventional technologies are fundamental technologies and their enhancement should be the first choiceConversion of the property of pollutants is sometimes more important than a complete remo
16、val of the pollutantsCombination of different technologies is the key for effective removal of pollutants,27,3.2 Enhancement of Conventional TechnologiesEnhanced coagulationFor the removal of NOM in drinking water treatmentFor the enhancement of primary treatment in wastewater treatmentTaking NOM re
17、moval as an example USEPA Enhanced Coagulation Rule,28,3.2 Enhancement of Conventional TechnologiesEnhanced coagulationRequirements for enhanced coagulation:Enhanced coagulation required as TOC 2 mg/LStep 1:percent removal requirements,29,Step 2:0.3/10 slope,30,pH adjustment is the key point,31,3.2
18、Enhancement of Conventional TechnologiesEnhanced filtrationFor the safeguard of drinking water quality especially the control of Giardia and CryptosporidiumGiardia lamblia:cyst size 8-12mm x 7-10mmCryptosporidium parvum:oosyst size 4.5-5 mm For tertiary wastewater treatment to acquire high quality e
19、ffluent,32,3.2 Enhancement of Conventional TechnologiesEnhanced filtrationRelationship between turbidity and particle size,33,Example of turbidity and Cryptosporidium oocyst data,34,3.2 Enhancement of Conventional TechnologiesEnhanced filtrationIron oxide-coated media for NOM sorption and particulat
20、e filtrationIron and aluminum hydroxide-coated media for the removal of Cryptosporidium,35,Breakthrough curves for NOM sorption onto coated sand,36,Zeta potential of uncoated sand and sand coated with iron and aluminum hydroxide,37,Improvement of the removal of Cryptosporidium oocysts in sand filter
21、s,38,3.2 Enhancement of Conventional TechnologiesEnhancement of biological processFluidized pellet bed(FPB)bioreactor as an example through a combination of physicochemical process and biological processHRT reduced to less than 1 hourPrimary settling and secondary settling omittedOrganic removal equ
22、ivalent to activated sludge processHigh TP removal achieved,39,Flow diagram of the FPB bioreactor,40,Pellets(granule sludge)formed in the bioreactor SEM image of microbes on the surface of the pellets,41,Distribution of aerobic and anaerobic bacteria,42,Removal of SS,COD,TP and TN by the bioreactor,
23、43,3.3 Ozone and Advanced Oxidation ProcessesReactivity of ozone in aqueous solutionIn an aqueous solution,ozone may act on various compounds by Direct reaction with the molecular ozoneIndirect reaction with the radical species that are formed when ozone decomposes in water Advanced oxidationOxidati
24、on by free radical reaction,44,Pathways of ozonationPseudo first-order kinetic equation of ozone decomposition,45,Ozone decomposition process,46,Initiators,promotors,and inhibitors of free-radical reactionsInitiators:the compounds capable of inducing the formation of a superoxide ion O2-from an ozon
25、e moleculePromotors:all organic and inorganic molecules capable of regenerating the O2-superoxide anion from the hydroxyl radicalInhibitors:compounds capable of consuming OH radicals without regenerating the superoxide anion O2-,47,Mechanism of ozone decomposition,48,Ozone decomposition process by h
26、ydroperoxide ions,49,Ozone decomposition process by UV radiation,50,3.3 Ozone and Advanced Oxidation ProcessesOzonation of synthetic organic chemicalsTwo ozonolysis pathways of ozonation:Direct attack by electrophilic or dipolar cyclo additionIndirect attack by free radicals produced by reaction wit
27、h water and water constituents,51,Kinetics of ozonation of dissolved organic micropollutantsOzonation pathwaysLet,52,The OH radicals are generated by ozone attack on organic and inorganic initiators,and there exists a relation asThe total oxidation rate of the particular substrate i can be written a
28、s,53,Characteristics of ozonation of organic compoundsDecrease of aromaticityUnsaturated structure to saturated structureGeneration of intermediate productsTotal degradation often needs very high ozone dose and takes longer time,54,Example:Ozonation of aromatic compounds,55,3.3 Ozone and Advanced Ox
29、idation ProcessesOzonation of natural organic matter(NOM)Aquatic humic substances(AHS):Isolation method:microfiltration of the water and adsorption of organics on XAD-8 resin at pH=2,followed by NaOH elution and separation by precipitation at pH=1.Two main groups:Humic acid precipitated fractionFulv
30、ic acid remaining part in the solution,56,Possible reaction of zone consumption in a natural aquatic environment,d inhibitorsi initiatorsp promotorss-scavengers,57,Ozone action on AHS,58,The effects of ozonation on AHSFormation of hydroxyl,carbonyl and carboxyl groups;Increase of polarity and hydrop
31、hilicity;Loss of double bonds and aromaticity;Shift in the molecular weight distribution toward lower-molecular-weight compounds.,59,Py-GC-MS analysis results,60,THMs and HPLC analysis results,61,Specific UV adsorption(SUVA)as a parameter showing the biodegradability of AHSTOC or DOC:total amount of
32、 organic carbonUV254:concentration of organics with unsaturated structureSUVA:UV-to-TOC ratio which represents the fraction of unsaturated functional groups in unit concentration of organic matterHigh SUVA value:less biodegradableLow SUVA value:more biodegradable,62,3.4 Membrane TechnologiesSpectrum
33、 of impurities in water and applicable filtration processes,63,3.4 Membrane TechnologiesMembrane operation,64,3.4 Membrane TechnologiesPressure-driven membrane operationRO:at least twice the osmotic pressure must be exerted 5 to 8 MPa for seawaterNF:osmotic backpressure much lower than RO typically
34、0.5 to 1.5 MPaUF:operating pressure 50 to 500 kPaMF:operating pressure similar to UF,65,3.4 Membrane TechnologiesPermeation behaviorDarcys lawTo account for the effects of osmotic pressure,66,3.4 Membrane TechnologiesReduction in Permeate FluxRc:resistance of concentration boundary layer Rcp:resista
35、nce of concentration-polarization layer D:diffusivity,67,3.4 Membrane TechnologiesReduction in Permeate Flux,The accumulation of materials on,in,and near a membrane in the presence of a cross flow,Reductions in permeate flux over time,68,3.4 Membrane TechnologiesMechanism of membrane foulingCake for
36、mationPore blockageAdsorptive foulingBiofouling,SEM image of a biofilm formed on a membrane,69,Conventional UF or MF process,70,Conventional NF or RO process,71,3.4 Membrane TechnologiesMembrane bioreactor(MBR)Principle of MBR,(a)MBR,(b)Membrane for tertiary treatment,72,3.4 Membrane TechnologiesMem
37、brane bioreactor(MBR)MBR configuration,(a)Recirculated MBR,(b)Integrated MBR,73,3.4 Membrane TechnologiesMembrane bioreactor(MBR)Advantages of MBRGreater biomass concentration and greater loadsHigh removal efficiencyLess sludge productionGreater reliability and flexibility of applicationAbility to a
38、bsorb variations and fluctuations in the applied hydraulic and organic loadComplete control of the sludge age to allow the development of slow-growing microorganisms(such as nitrifying bacteria),74,4.Trend of Development,4.1 Integration of Water and Wastewater SystemFundamental considerationsWater s
39、upply and wastewater systems are subsystems in the series of urban metabolic system of waterWater supply according to the purposes of use regarding both quantity and qualityDesign of water and wastewater systems as one comprehensive water system,75,Future urban water system with application of membr
40、ane technology,76,4.2 Decentralized Systems for Wastewater Treatment and ReusePhilosophy of decentralizationNon-mixingGrey water:Large volumes,COD diluted,little nutrients,pathogens,no pharmaceuticals,personal care productsBlack water:Little volumes,possibilities to minimise them even further,high C
41、OD and nutrients,pathogens,pharmaceuticals and hormonesSeparate treatmentTreatment depends on the objectiveRecovery of useful resourcesWater,energy,fertilizer,77,4.3 Control of Micropollutants in Water and Wastewater TreatmentControl of pollutant sourceUtilization of hybrid processAdvanced oxidation and carbon adsorptionUtilization of hybrid membrane processMembrane-powdered activated carbon reactorIon exchange membrane reactor,
