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CU-Boulder CVEN 5534 - Wastewater characteristics

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1 Wastewater Sources, Flows and Contaminants into Municipal Sewers Served by Publically Owned Treatment Works (POTW) 1. Domestic (household wastes): toilet, shower, cooking, washing and laundry 2. Commercial/service: schools, hospitals, restaurants, offices, hotels, small businesses 3. Industrial: processing wastewater, cooling water 4. Non-point sources: a. Infiltration from groundwater into sewers b. Inflow from stormwater surcharge into sewer manholes c. Combined storm/sewer overflows, older sewer systems where storm sewers discharge into sanitary sewers (Chicago, San Francisco, etc.) Typical wastewater flowrates in US (from Metcalf and Eddy, 2003) Source gpcd except as noted lpcd except as noted Domestic 45-75 120-280 Commercial laundry 450 g/unit/d 1700 l/unit/d Hospital 175-400 g/bed/d 660-1500 l/bed/d School 25 g/student/d 100 l/student/d Breakout of residential indoor water use in US with and without water conservation practices and devices* Flow (L/capita-day) Use Without conservation With conservation Bathing 5 5 Showers 50 42 Dishwashing 4 4 Clothes washing 64 45 Faucets 43 42 Toilets 73 35 Leaks 36 18 Other domestic uses 6 6 Total 281 197 *Faucet aerators, flow-limited showerheads, low-flush toilets, pressure reducing valve, pressurized shower, retrofit kits for bathroom (toilet dam, leak detector, shower flow restrictor), vacuum toilet, water efficient dishwasher, water-efficient clothes washer.2 Impact of water-saving toilets, showers, washing machines: reduce domestic flowrates from 281 gpcd to 197 gpcd. International Comparison Region lpcd World average 63 US 365 China 80 Sub-Saharan Africa 25 Algeria/Morocco 38 Latin America 130 Industrial wastewater generation: highly variable depending on industry. Estimating based on industrial area 7.5 to 28 m3/ha-day for non-water using industry. For water using industries (food and beverage processing, manufacturing) without internal recycling, assume that 85-95% of water use will become wastewater. Sanitary wastewater from workers estimated from 30 – 95 L/capita-day. Pretreatment onsite (including flow equalization) can reduce impact of peak flows, high organic or toxics loading to POTW. Infiltration/Inflow can have a significant impact on wastewater flow Flows into collection systems from extraneous sources: 1. Infiltration. Inflows from service connections, cracks and joints in sewer pipes, or manhole walls. Wide range: 0.2 – 28 m3/ha-day depending on lot size, sewer pipe age and composition. During a storm event, infiltration and leakage can reach 500 m3/ha-day. 2. Steady inflow. Water from foundation, spring, or swamp drains, cooling water, generally constant and measured. 3. Direct inflow. Stormwater runoff in combined sewers, roof and yard drains, cross connections from storm drains, or through manhole covers. 4. Delayed inflow. Retarded stormwater discharge due to sump pumps, retention ponds, etc. 5. Total inflow. Sum of direct inflow at any point plus upstream flow from overflows and bypasses.3 Wastewater Constituents Important constituents: Particulate matter characterization a. Suspended solids size range: 0.01 (colloidal) to 100 m Reference particles: viruses (0.01 – 0.05); bacteria (0.5 – 1); algae, organic debris or bacterial flocs: 5 – 100. Suspended solids often defined by filtration measurement (particle diameter > 0.45 m. b. Organic composition: percent volatile (organic) versus fixed. Organic matter characterization a. Biodegradability (direct assay): biochemical oxygen demand (BOD) b. Aggregate organic content (chemical assay) i. Chemical oxygen demand (COD) ii. Total organic carbon (TOC) iii. Aromaticity (UV 254) iv. Volatile fatty acids v. Oil and grease : solvent extractable organic matter vi. Surfactants measured as reactivity with reagents: methylene blue active substances (MBAS) or cobalt thiocyanate active substances (CTAS) c. Individual compounds i. 129 Priority pollutants (VOC’s and SOC’s as well as heavy metals, radionuclides) ii. Disinfection by-products: trihalomethanes, haloacetic acids, bromated, N-nitrosodimethylamine (NDMA) iii. Pesticides iv. Emerging organic contaminants: pharmaceuticals (anti-inflammatory’s, antibiotics, synthetic hormones, painkillers, steroids, etc.), personal care products and plasticizers (detergents, nonylphenol, bisphenol A) Nutrients. a. Nitrogen i. Particulate: organic nitrogen (cells, organic debris) ii. Soluble species 1. Soluble organic nitrogen (urea, cell compounds) 2. Ammonium (NH4+)4 a. Total Kjeldahl Nitrogen (TKN) where TKN = ON + NH4-N 3. Nitrate (NO3-) 4. Nitrite (NO2-) 5. Nitrous oxide (N2O) as greenhouse gas b. Phosphorus i. Particulate (cells, and cell storage products) ii. Soluble: orthophosphate (PO43-) Other chemical characteristics a. pH i. 5.5 < pH < 9 for discharge and general microbial growth ii. pH > 6.5 for nitrification iii. pH > 7.2 for methane generation c. alkalinity: HCO3- + CO32- + OH- - H+ pH buffering capacity may be added or consumed during biological treatment d. salinity (TDS, electrical conductivity, SAR, etc) rarely affects treatment in typical wastewater, may affect reuse Pathogenic microorganisms a. Indicators: total coliform, fecal coliform, Salmonella, Clostridium perfringens, Enterovirus b. Specific organisms: Giardia lamblia, Cryptosporidium parvum Toxicity, measured as potential for inhibition of bacteria and/or accumulation in biosolids5 Constituents terminology definition Total solids TS all non water constituents Total volatile solids TVS ~all soluble and particulate organic matter, oxygen demanding Total fixed solids TFS=TS=TVS all soluble and particulate inorganic matter Total suspended solids TSS all particulate matter (typically > 0.45 m) Volatile suspended solids VSS ~particulate organic matter, oxygen demanding Fixed suspended solids FSS=TSS-VSS particulate inorganic matter Total dissolved solids TDS = TS-TSS all soluble constituents (typically < 0.45 m) Volatile dissolved solids VDS ~ soluble organic matter, oxygen demanding Fixed dissolved solids FDS soluble inorganic matter Settleable Solids solids that settle under gravity Turbidity NTU approximately colloidal matter (non-settleable solids) Color brown, gray, black measure of sewage age, redox state Odor TON threshold odor number for odor control measures Conductivity EC Measure of dissolved ions (salinity). TDS ~ 0.6*EC Ammonia NH3/NH4+ nutrients, oxygen

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