物理化学水处理英文讲义

1、Physical-chemical treatment of water and wastewater Topic 1l Course descriptionPrinciples of treatment for removing contaminants from drinking water and municipal wastewater ;includes air stripping, coagulation and flocculation, sedimentation, air flotation, filtration, disinfection, oxidation, memb

2、rane processes, water softening, and carbon adsorption.l Water quality regulationl Water characteristicsMicrobiological contaminants:a) Coliform bacteriab) More resistant microbesc) Protozoad) VirusesSynthetic organic chemicals(SOCs):a) Disinfection by-products(DBPs): THMs, HAAsb) Industrial contami

3、nants: VOCsc) Agricultural contaminantsInorganic chemicals(IOCs):a) Ground water contaminants: Heavy metal, radioactive wastesb) Plumbing systems: Pb, Cuc) Disinfectant residualsl Processes selectionConsiderations:1) Contaminants removal2) Utility capability3) Source water quality4) Costs5) Reliabil

4、ity6) Environmental capability7) Existing conditions8) Distribution system water quality9) Process flexibilityl Fundamental principles 1) Mass balance 2) Reaction kinetics3) Reactor design4) Aquatic chemistry: Acid-base chemistry/Precipitation/Oxidation-reduction Aim at: a) Facilitating separations

5、(转移)b) Achieving destruction (转化)l Material Balancel Reactor Theorya) Mixed Batch Reactor(MBR) 混合式反应器b) Continuously (Completely) Stirred Tank Reactor(CSTR) 连续搅拌式反应器c) Plug Flow Reactor(PFR) 推流式反应器l MBRa) Well-mixedb) Uniform composition in all substances and conditionsc) Constant volumed) No flow i

6、n or outl CSTRa) Well-mixedb) Uniform composition in all substances and conditionsc) With same flow in or outl PFRa) Uniform longitudinal velocity profileb) Transverse well-mixingc) No longitudinal mixingd) With same flow in or outl Fundamental of reaction kinetics GlossaryUnit operations-单元操作(physi

7、cal forces) ; Unit processes-单元过程(chemical reactions);Acidity-酸度; Alkalinity-碱度; Bases Coefficient- ; Equilibrium constant-平衡常数;ppm-百万分率; ppb-十亿分率;Physical-chemical treatment of water and wastewater Topic 2 Basics of Water and Wastewaterl WaterLake/ river/ reservoir/ groundwaterl Wastewatera) Sanita

8、ry wastewater（生活废水）b) Non-sanitary wastewater（非生活废水）c) Storm sewage（暴雨污水）l Constituents in water and wastewatera) Physical characteristicsTurbidity(NTU)/ Color(CU)/ Taste(TTN)/ Odor(TON)/ Temperatureb) Chemical characteristicsOrganicBOD (Biological Oxygen Demand)/COD (Chemical Oxygen Demand)/TOC (To

9、tal Organic Carbon)/Surfactants: Detergents/VOC (Volatile Organic Compounds)/Fat/ Oils/ Waxes/ GreaseInorganicAnion: Choloride (Cl-)/ Fluoride(F-)/ Nitrate(NO3-)/ Sulfate(S2-)Cation: Sodium(Na)/ Iron(Fe)/ Manganese(Mn)/ Lead(Pb) /Copper(Cu)/ Zinc(Zn)OthersPhAcidity and alkalinityNitrogenPhosphorousP

10、riority pollutants(优先控制污染物)Toxic metal and nonmetal ionsl Constituer 构成TS (total solids)/ TFS (total fixed solids)/ TVS (total volatile solids)/ FSS (fixed suspended solids)-TSS(total suspended solids)- VSS(volatile suspended solids)FDS (fixed dissolved solids)-TDS(total dissolves solids)-VDS(volati

11、le dissolves solids)l Other Important Terms1) BOD/COD/TOC/TN/TP/TSS2) Solubility Product(溶度积)3) Chemical Equilibrium(化学平衡)4) Henrys Law Constant(亨利常数)5) DOl Indicator MicroorganismServing as a surrogate to indicate the water quality with respect to the fecal contamination or relative quantities of a

12、ll forms of pathogens.a) Fecal Pollutant Originb) Indicator OrganismsEscherichia coli/ Fecal coliform/ Total coliformc) Numeration(计数方法):Membrane Filtration Techniquel Measurement l CalculationHardnessAlkalinityPhysical-chemical treatment of water and wastewater Topic 3 Typical Processes for Water T

13、reatmentl Water Engineering Tasks:a) Removal of particlesb) Removal of pathogen to prevent waterborne diseasesc) Removal of chemical cotaminantsd) Control of taste and odorGoals:a) BOD5 1-5mg/Lb) TN <1mg N/Lc) TP <0.5mg P/Ll Management of Water Resources Source selectionsMajor Sources: River/

14、Lake/ reservoir/ Groundwater/ Sea waterl River Water Quality:a) Fluctuates in time and location;b) Usually has a high turbidity, large number of bacteria, and a low hardness;c) May have overgrowth of algae generating unpleasant flavors (smells & tastes) and color. l Eutrophication Eutrophication

15、 often occurs in closed water bodies such as shallow tidal rivers, lakes, reservoirs, sea bays because of limited dilution capacity resulting in nutrients accumulation in the mud.Cause:a) Death of fishes due to release of toxicants from a algae;b) Shortage of dissolved oxygen during night-time as al

16、gae consume a great deal of oxygen by algal respiration;c) Unpleasant flavors such as bad taste and smell and high tubidity. Deal with: below 1mg N/L & 0.5mg P/Ll Water Treatment & Supply Systems for River Water Major impurities: large & small sized debris, fine particles, ammonia, algae

17、, dissolved organic matterSystem:River Pumping Plain sedimentation coagulation Flocculation Sedimentation Filtration Disinfection Pumping Storage Neighborhoodl Lake/ Reservoir Water Treatment Major impurities: SS & TDS lower than river waterQuality: Clear than river water because of the sediment

18、ation effect.Quantity: It also varies in seasons.System:Lake Pumping Aeration/ Prechlorination/ Preoxidation coagulation Flocculation Sedimentation Filtration Disinfection Pumping Storage Neighborhoodl Ground Water/ Well Water Treatment Major impurities: Heavy metal, chemical & biological pollut

19、ants. Hardness：Ca & MgSystem:Well Aeration Softening Filtration Disinfection Add Fluoride Storage Neighborhoodl Other Water Treatment Processesa) Softeningb) Ion Exchangec) Reverse Osmosis 反渗透d) Activated Carbon AdsorptionPhysical-chemical treatment of water and wastewater Topic 4 Overview of Se

20、wage Treatmentl Terminology u Composition-构成; Constituents-成分; Contaminants-污染物; Pollutants-污染物；Impurities-杂质; Nutrient-营养物; u Point sources-点源; Non-point sources-非点源; Effluent-流出; Influent-流入;u Reclamation-再生; Recycling-回收利用; Repurification-再净化; Reuse-重新使用u Sludge-污泥; Solids-固体; Biosolid-生物固体;l Par

21、ameters of wastewaterBOD5/DO/COD/TDS/TP/TN/Fecal coliform l Effluent Standardsa) Established from a stand view of “best available technology”b) Consider environmental or purification capacity of a water receiving bodyc) Depend on usage of a receiving body and types of treatment methodsl Treatment le

22、vela) Preliminaryb) Primaryc) Advanced primaryd) Secondarye) Secondary with nutrient removal f) Consider environmental or purification capacity of a water receiving bodyg) Advancedl Typical Sewage Treatment SystemRaw Waste Bar Screen Grit Chamber Primary Sedimentation Biological Treatment Secondary

23、Sedimentation Advanced Treatment Disinfection Receiving Water Bodyl Types of sewage treatment processesa) Mechanical treatmentb) Biological treatmentc) Advanced treatmentl Removal of constituentsa) Suspended solids Screening/ Grit removal/ Sedimentation/ High-rate clarification/ Flotation/ Chemical

24、precipitation/ Depth filtration/ Surface filtrationb) Biodegradable organics (可生物降解的有机物)Aerobic suspended growth variations/ Aerobic attached growth variations/Anaerobic suspended growth variations/Anaerobic attached growth variations/Lagoon variations/ Physical-chemical systems/ Chemical oxidation/

25、 Advanced oxidation/ Membrane filtrationc) NutrientsNitrogen: Chemical oxidation/ Suspended-growth nitrification(硝化) and denitrification(反硝化) /Fixed-film nitrification and denitrification variations/Air stripping/ Ion exchangePhosphorus: Chemical treatment/ Biological phosphorus removalNitrogen &

26、; phosphorus: Biological nutrient removal variationsd) PathogenChlorine compounds/ Chlorine dioxide/ Ozone/ Ultraviolet(UV) radiatione) Colloidal and dissolved solidsMembrane/ Chemical treatment/ Carbon adsorption/ Ion exchangef) Volatile organic compoundsAir stripping/ Carbon adsorption/ Advanced o

27、xidation/ g) OdorsChemical scrubbers/ Carbon adsorption/ Biofilters/ Compost filtersl Primary Treatmenta) Preliminary treatment: Bar screen/ Grit chamber/ Comminuterb) Primary Sedimentationl Biological Treatment (secondary)a) Activated Sludgeb) Trickling Filterc) Rotating Biological Contactorl Disin

28、fectionl Oil and Grease Controll Advanced Treatmenta) Nitrogen removal: Ammonia stripping/ Nitrification/ Denitrificationb) Phosphorus removal: Chemical precipitation/ Biological Processes c) For water reused) Depend on usage: filtration/ GAC WordsNitrosomonas - 亚硝化单胞菌; Nitrobacter 硝化菌; Denitrifer 脱

29、氮菌Physical-chemical treatment of water and wastewater Topic 5 Preliminary Unit Operationsl Unit operations and processesUnit operationsa) Flow meters流量计b) Pumpingc) Screeningd) Mixinge) Flocculationf) Setting and flotationg) Filtrationh) Adsorptioni) Aeration and strippingj) MembraneUnit processesa)

30、 Softeningb) Neutralization中和c) Stabilizationd) Chemical precipitatione) Phosphorus removalf) Iron and manganese removalg) Coagulationh) Ion exchangei) Disinfectionj) Oxidation-reductionl Flow Metersa) Coriolis flowmetersb) Turbine flowmeters 涡轮流量计c) Differential pressure flowmeters 压差流量计d) Variable

31、 area flowmeters 转子流量计l WeirsWeir is an obstruction that is used to back up a flowing stream of liquid.l ScreeningA unit operation that separates materials into different sizes .Coarse screens(6-150mm)/ Micro screens(<0.5um)/ Fine screens(<6mm)a) Screenings retained on the coarse (>12mm)Deb

32、ris, rocks, branches, pieces of lumbers, leaves, paper, plastics, rags, organicsb) Screenings retained on the fine(>6mm)Small rags, razor blades, grid, fecesl Coarse solids reductiona) Comminutor 磨碎机b) Macerator 碎渣机c) Grinder 研磨机l Flow equalizationA method used to overcome the operational problem

33、s caused by flowrate variations, to improve the performance of the downstream processes, to reduce the size and cost of downstream treatment facilities.l Grit removalGrit chambers are designed to remove grit, consisting of sand, gravel, cinders, or other heavy solid materials that have subsiding vel

34、ocities or specific gravities substantially greater than those of the organic putrescible solid in wastewater.Horizontal-flow grit chambers/ Aerated grit chambers/ Vortex-type grit chambersl PumpingA unit operation that is used to move fluid from one point to another.l MixingPhysical-chemical treatm

35、ent of water and wastewater Topic 6 Aeration ( Air Stripping )l MechanismExchange of gases from air phase to water phase (absorption) or from water phase to air phase (stripping) due to the displacement of the system from equilibrium partitioning. Unsaturation/absorption Saturation/equilibrium Super

36、saturation/desorptionl Two-Film TheoryIt states that gas transfer is governed by the resistance of the gas and liquid films surrounding the interface.l Gas Transfer TheoryTherefore, the extent of displacement of the system from equilibrium provides the driving force that governs the gas (mass) trans

37、fer.l Major Types of Aeration MeansDiffused (or bubble) aerationSurface (mechanical) aerationGravity aerators: Cascade/ Inclined/ Tower/ Stack Tray/ Cascade Tower/ Spray AeratorPhysical-chemical treatment of water and wastewater Topic 7 Coagulation/ Flocculationl Colloidal StabilityRepulsion force:

38、Electrostatic potentialAttraction force: Van der Waals forcel Coagulation Theorya) Iron layer compressionb) Adsorption and charge neutralizationc) Sweep coagulationl Hydrolyzed Trivalent Alum Ionsl Action of hydrolyzed metal ions1) Ionic layer compression2) Adsorption and charge neutralization3) Ads

39、orption and interparticle bridging4) Enmeshment in sweep flocPhysical-chemical treatment of water and wastewater Topic 8 Settling (or Sedimentation, clarification)l BasicsPhysical removal of dense/heavy suspended solids from water by exposing the water to relatively quiescent conditions to allow set

40、tleable solids to be removed by the action of the force of gravity.settling tank (basin) / sedimentation tank (basin) / clarifierl Factors affecting particle settlingParticle densityParticle concentrationDilute suspension / Concentrated suspensionSurface flocculent natureDiscrete particles / Floccul

41、ating particlesl 4 typesDiscrete Settling / Flocculating Settling Zone Settling / Compression Settlingl Discrete SettlingType I settling is characterized by settling of individual particles without interaction with adjacent particles.The shape, size and density of the particles remain unchanged duri

42、ng settling.Examples of Type I Settlings : Settling of sand, grit etc.Application : Design of primary settling tank, grit chamberl Flocculating SettlingSettling flocculating particles in dilute suspension:Dilute suspension - no interference of the velocity field between particles.Flocculating partic

43、les - aggregation of particles causing continually changing in size and shape of particles for settling.The flocs will increase their size - speed up settlingl Variations of the types of sedimentation tankHorizontal-flow settling tankUpflow clarifierHigh rate (inclined plate) settlersReactor (solid

44、contact) clarifierPhysical-chemical treatment of water and wastewater Topic 15 MembraneFeedwater (f)Qf=feedwater flowrateCf=feedwater concentrationPf=feedwater pressurePermeate (f)QP=permeate flowrateCP=permeate concentrationPP=permeate pressureConcentrate (f)QC=concentrate flowrateCC=concentrate co

45、ncentrationPC=concentrate pressurel ClassificationMicrofiltration (MF)-微滤Ultrafiltration (UF)-超滤Nanofiltration (NF)-纳滤Reverse osmosis (RO)-反渗透Dialysis-渗析Electrodialysis (ED)-电渗析Membrane processOperating structure (pore size)Typical operating rang, umPermeate descriptionTypical constituent removedMicro-filtrationMacropore(>50 nm)0.08-2.0Water,dissolved solutesTSS, turbidity, protozoan oocysts and cysts,