1、An Introduction to Urban Water and Wastewater Treatment Technologies,Prof. X. C. WangXian Univ. of Architecture & Technology,2,Contents,1. Contaminants in Water2. Contaminant Sources and Treatability3. Best Available Technologies4. Trend of Development,3,1. Contaminants in Water,1.1 Target of Water
2、Quality Control,Wastewater Discharge Regulation,Key point: Protection of human health,4,1.2 Capacity of Water EnvironmentA simple calculation,Ci : Concentration of contaminant i Mi : Mass of contaminant i in water V : Water volume,Mi0 : Mass of contaminant i received Mir : Mass of contaminant i assi
3、milated (removed) by the water body itself (self purification),5,1.2 Capacity of Water Environment Water 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 Environme
4、ntal Standard American standard: Clean Water Act (CWA)Ambient Water Quality Criteria for the Protection of Human Health Aquatic Life Criteria Nutrient Criteria,7,1.3 Water Environmental Standard American standard: Clean Water Act (CWA) The NRWQC 2002 includes Criteria for priority toxic pollutants:
5、120 items (15 for inorganic, 105 for organic pollutants) Criteria for non priority pollutants: 45 items Criteria for organoleptic (taste and odor) effects: 23 itemsDownloadable athttp:/www.epa.gov/waterscience/criteria/ wqcriteria.html,8,1.3 Water Environmental Standard Chinese standard: Environment
6、al 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 items Supplemental parameters for source 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 items Specific 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
7、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,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 Concern In
8、dicative parameters Suspended solids: SS Dissolved solids: TDS (salinity) Organic substances: COD, BOD, TOC, UV Dissolved oxygen: DO Acidity: pH Nutrients Nitrogen: TN, NH3-N, NO3-N, NO2-N Phosphorous: TP, Portho, Ppoly, Poranic ,17,1.4 Pollutants of Public Concern Synthetic organic chemicals (SOCs)
9、 Industrial products such as PCBs (Polychlorinated biphenyls) Industrial byproducts such as Dioxin Pesticides and herbicides DBP precursors Natural organic matter (NOM) such as humic acids etc. Persistent organic pollutants (POPs) DDT, PCBs, PAHs, Hexachlorobenzene, Dioxins, Furans ,18,1.4 Pollutant
10、s of Public Concern Endocrine disruptive chemicals (EDCs) Heavy metals such as Cr, Pb etc. PCBs, hormones, dioxins Organo-chlorinated pesticides Microorganisms Giardia Cryptosporidium Viruses and bacteria,19,2. Contaminant Sources and Treatability,2.1 Contaminant Sources Point sources: Sources of po
11、llutants 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 attribute a great deal to water pollution: Nutrients, pesticides, NOM Certain POPs and E
12、DCs,20,2.2 Treatability of Pollutants The treatability of pollutants depends on their Size Suspended Colloidal Soluble Chemical properties Organic Inorganic Biodegradability Biodegradable Bio-non-degradable,21,Water quality and treatability matrix,22,Domestic wastewater as an example Methods of poll
13、utants classification Suspended and soluble: using a 0.45 mm filter Settleable and non-settleable:plain settling for 2 hours Coagulable and non-coagulable:coagulation and settling Secondary treatment:activated sludge process (oxidation ditch),23,24,2.3 Limitation of Conventional Treatment Convention
14、al treatment Typical process for water treatment: Coagulation sedimentation filtration chlorination Typical process for wastewater treatment (activated sludge process): Screening primary settling biological unit secondary settling chlorination,25,2.3 Limitation of Conventional Treatment Pollutants t
15、hat can be removed Suspended solids Colloidal matter Biodegradable organic matter Bacteria and viruses Pollutants that cannot be removed Most of the dissolved solids Bio-non-degradable organic matter Chlorine persistent microorganisms (e. g. Cryptosporidium),26,3. Best Available Technologies,3.1 Str
16、ategic Considerations on the Selection of Available Technologies Conventional technologies are fundamental technologies and their enhancement should be the first choice Conversion of the property of pollutants is sometimes more important than a complete removal of the pollutants Combination of diffe
17、rent technologies is the key for effective removal of pollutants,27,3.2 Enhancement of Conventional Technologies Enhanced coagulation For the removal of NOM in drinking water treatment For the enhancement of primary treatment in wastewater treatment Taking NOM removal as an example USEPA Enhanced Co
18、agulation Rule,28,3.2 Enhancement of Conventional Technologies Enhanced coagulation Requirements for enhanced coagulation:Enhanced coagulation required as TOC 2 mg/L Step 1: percent removal requirements,29,Step 2: 0.3/10 slope,30,pH adjustment is the key point,31,3.2 Enhancement of Conventional Tech
19、nologies Enhanced filtration For the safeguard of drinking water quality especially the control of Giardia and Cryptosporidium Giardia lamblia: cyst size 8-12mm x 7-10mm Cryptosporidium parvum: oosyst size 4.5-5 mm For tertiary wastewater treatment to acquire high quality effluent,32,3.2 Enhancement
20、 of Conventional Technologies Enhanced filtration Relationship between turbidity and particle size,33,Example of turbidity and Cryptosporidium oocyst data,34,3.2 Enhancement of Conventional Technologies Enhanced filtration Iron oxide-coated media for NOM sorption and particulate filtration Iron and
21、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 filters,38,3.2 Enhancement
22、of Conventional Technologies Enhancement of biological process Fluidized pellet bed (FPB) bioreactor as an example through a combination of physicochemical process and biological process HRT reduced to less than 1 hour Primary settling and secondary settling omitted Organic removal equivalent to act
23、ivated sludge process High TP removal achieved,39,Flow diagram of the FPB bioreactor,40,Pellets (granule sludge) formed in the bioreactorSEM 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,43,3.3 Ozo
24、ne and Advanced Oxidation Processes Reactivity of ozone in aqueous solutionIn an aqueous solution, ozone may act on various compounds by Direct reaction with the molecular ozone Indirect reaction with the radical species that are formed when ozone decomposes in water Advanced oxidationOxidation by f
25、ree 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 reactions Initiators: the compounds capable of inducing the formation of a superoxide ion O2- from an ozone
26、molecule Promotors: all organic and inorganic molecules capable of regenerating the O2- superoxide anion from the hydroxyl radical Inhibitors: compounds capable of consuming OH radicals without regenerating the superoxide anion O2-,47,Mechanism of ozone decomposition,48,Ozone decomposition process b
27、y hydroperoxide ions,49,Ozone decomposition process by UV radiation,50,3.3 Ozone and Advanced Oxidation Processes Ozonation of synthetic organic chemicals Two ozonolysis pathways of ozonation: Direct attack by electrophilic or dipolar cyclo addition Indirect attack by free radicals produced by react
28、ion with water and water constituents,51,Kinetics of ozonation of dissolved organic micropollutants Ozonation 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
29、written as,53,Characteristics of ozonation of organic compounds Decrease of aromaticity Unsaturated structure to saturated structure Generation of intermediate products Total degradation often needs very high ozone dose and takes longer time,54,Example: Ozonation of aromatic compounds,55,3.3 Ozone a
30、nd Advanced Oxidation Processes Ozonation 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 pre
31、cipitated fractionFulvic acid remaining part in the solution,56,Possible reaction of zone consumption in a natural aquatic environment,d inhibitors i initiators p promotors s - scavengers,57,Ozone action on AHS,58,The effects of ozonation on AHS Formation of hydroxyl, carbonyl and carboxyl groups; I
32、ncrease of polarity and hydrophilicity; 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 biodegradabilit
33、y of AHS TOC or DOC: total amount of organic carbon UV254: concentration of organics with unsaturated structure SUVA: UV-to-TOC ratio which represents the fraction of unsaturated functional groups in unit concentration of organic matter High SUVA value: less biodegradable Low SUVA value: more biodeg
34、radable,62,3.4 Membrane Technologies Spectrum of impurities in water and applicable filtration processes,63,3.4 Membrane Technologies Membrane operation,64,3.4 Membrane Technologies Pressure-driven membrane operation RO: at least twice the osmotic pressure must be exerted 5 to 8 MPa for seawater NF:
35、 osmotic backpressure much lower than RO typically 0.5 to 1.5 MPa UF: operating pressure 50 to 500 kPa MF: operating pressure similar to UF,65,3.4 Membrane Technologies Permeation behavior Darcys lawTo account for the effects of osmotic pressure,66,3.4 Membrane Technologies Reduction in Permeate Flu
36、xRc: resistance of concentration boundary layerRcp: resistance of concentration-polarization layerD: diffusivity,67,3.4 Membrane Technologies Reduction 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,
37、3.4 Membrane Technologies Mechanism of membrane fouling Cake formation Pore blockage Adsorptive fouling Biofouling,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 Technologies Membrane bioreactor (MBR) Principle of MBR,(a)
38、 MBR,(b) Membrane for tertiary treatment,72,3.4 Membrane Technologies Membrane bioreactor (MBR) MBR configuration,(a) Recirculated MBR,(b) Integrated MBR,73,3.4 Membrane Technologies Membrane bioreactor (MBR) Advantages of MBR Greater biomass concentration and greater loads High removal efficiency L
39、ess sludge production Greater reliability and flexibility of application Ability to absorb variations and fluctuations in the applied hydraulic and organic load Complete control of the sludge age to allow the development of slow-growing microorganisms (such as nitrifying bacteria),74,4. Trend of Dev
40、elopment,4.1 Integration of Water and Wastewater System Fundamental considerations Water supply and wastewater systems are subsystems in the series of urban metabolic system of water Water supply according to the purposes of use regarding both quantity and quality Design of water and wastewater syst
41、ems as one comprehensive water system,75,Future urban water system with application of membrane technology,76,4.2 Decentralized Systems for Wastewater Treatment and Reuse Philosophy of decentralization Non-mixing Grey water: Large volumes, COD diluted, little nutrients, pathogens, no pharmaceuticals
42、, personal care products Black water: Little volumes, possibilities to minimise them even further, high COD and nutrients, pathogens, pharmaceuticals and hormones Separate treatment Treatment depends on the objective Recovery of useful resources Water, energy, fertilizer,77,4.3 Control of Micropollutants in Water and Wastewater Treatment Control of pollutant source Utilization of hybrid process Advanced oxidation and carbon adsorption Utilization of hybrid membrane process Membrane-powdered activated carbon reactor Ion exchange membrane reactor ,78,
