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 point: Protection of human health,4,1.2 Capacity of Water Environment A 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 assimilated (removed) by the water body itself (self purification),5,1.2 Capacity of Water Environment Water quality criteria This is equivalent to Mir 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 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: 120 items (15 for inorganic, 105 for organic pollutants) Criteria for non priority pollutants: 45 items Criteria for organoleptic (taste and odor) effects: 23 items Downloadable at http:/www.epa.gov/waterscience/criteria/ wqcriteria.html,8,1.3 Water Environmental Standard Chinese 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 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 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 Indicative 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) 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 Pollutants 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 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 attribute a great deal to water pollution: Nutrients, pesticides, NOM Certain POPs and EDCs,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 pollutants 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 Conventional 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 that 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 Strategic 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 different 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 treat