waste mngmt - Water Quality Water Quality and Waste...

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Unformatted text preview: Water Quality Water Quality and Waste Management FScN 4131 Food Quality October 11, 2000 • Uses of Water 1. Ingredient 2. Cleaning and sanitation 3. Personal consumption Water Quality: Drinking EPA regulations: Primary drinking water regulations • Enforceable Water Quality: Primary Drinking Water Regulations Types of contaminants: • Inorganic chemicals (16) • Organic chemicals (54) • Radionuclides (3) • Microorganisms (4) Secondary drinking water regulations • Non-enforceable • Cosmetic, aesthetic or taste defects Water Quality: Process Water Water Quality: Primary Drinking Water Regulations • Hardness (“Hard water”) a) Temporary – High concentration of Ca and Mg bicarbonates – Traditionally expressed as CaCO3 – Removed by boiling Ca(HCO3)2 CaCO3 Water Quality: Process Water • Hardness (“Hard water”) a) Permanent – High concentrations of Ca and Mg sulfates – Not removed by water Water Quality: Process Water Temporary hardness classification Temporary mg/L mg/L SOFT 0 - 60 MODERATELY HARD* 61 - 120 HARD* HARD 121 - 180 VERY HARD > 180 *Recommended level for drinking water Grains 0 - 3.5 3.6 - 7.5 7.6 - 10.5 > 10.5 Water Quality: Process Water Water hardness issues – Interferes with detergent effectiveness – Forms scale on equipment and plumbing • • • Heat exchangers Boilers CIP equipment Water Quality: Process Water Other Issues: – High Fe undesirable for soft drinks – High Ca affect texture of navy beans and peas – Leaves residue that favors accumulation of organic material and microorganisms Water Quality: Treatment 1. Sedimentation 2. Pretreatment 3. Coagulation 4. Softening 5. Filtration 6. Disinfection Water Quality: Treatment 1. Sedimentation • Eliminates soil and suspended material Water Quality: Treatment 2. Pretreatment • Addition of activated carbon to eliminate tastes or odors • Addition of chlorine to enhance coagulation and softening Water Quality: Treatment 3. Coagulation or flocculation – Addition of alum (aluminum sulfate) or ferric chloride – They form a gel-like floc – Removes all suspended material Water Quality: Treatment 4. Filtration – Sand filters remove extra floc – Activated carbon filters to remove organic compounds – Reverse osmosis (RO) eliminates inorganic salts Water Quality: Treatment 5. Softening – Boiling – Ion-exchange NaCl columns - trap Ca ions Water Quality: Treatment 6. Disinfection – Chlorination – Ultraviolet light units Waste Management Waste Management Feedstock Water Food Processing Product Indicators of Wastewater Quality • • • • Biochemical Oxygen Demand (BOD) Chemical Oxygen Demand (COD) Dissolved Oxygen (DO) Total Organic Carbon (TOC) Wastes: water, offal, packaging, etc. Indicators of Wastewater Quality • Residue in wastewater – Settleable Solids (SS) – Total Suspended Solids (TSS) – Total Dissolved Solids (TDS) – Fats, oil and grease (FOG) – Turbidity – Total Kjeldhal Nitrogen (TKN) – Phosphorous – Sulfate and sulfide Indicators of Wastewater Quality • Biochemical Oxygen Demand (BOD) – Concentration of oxygen consumed by microorganisms to decompose organic matter present in water – Index of the biodegradable material – AOAC’s official method (BOD5) • Lasts 5 days • Oxygen concentration measured by titration or by a dissolved oxygen meter probe Typical BOD5 of Food Wastes Type Dairy and milk products Food products Meat products Rendered products Vegetable oils BOD5 (ppm) ppm) 670 790 1,140 1,189 530 From Marriott, N.G. (1999) Indicators of Wastewater Quality • Biochemical Oxygen Demand (BOD) – Disadvantages: 1) Does not measure total organic matter 2) Time consuming 3) Lacks reproducibility Indicators of Wastewater Quality • Chemical Oxygen Demand (BOD) – Concentration of oxygen that organic matter consumes chemically – Determined indirectly with potassium dichromate, K2Cr2O7 – Measures non-degradable matter – Disadvantages • Not all organic matter can be degraded • Not all molecules are oxidized Indicators of Wastewater Quality • Dissolved Oxygen (DO) – Measures remaining oxygen – Lack of DO indicates poor quality to sustain aquatic life – Measured by: • Iodometric titration • Electrode probe (interference of other molecules) BOD and OD website: http://www.epa.gov/OWOW/monitoring/volunteer/stream/vms52.html Indicators of Wastewater Quality • Total Organic Carbon (TOC) – Measures CO2 produced from organic matter produced by catalytic oxidation or combustion at >680ºC – Fast and highly reproducible – Requires lab equipment – Expensive instrument: Combustion/nondispersive infrared gas analysis method Indicators of Wastewater Quality • Residue in Wastewater: Settleable Solids (SS) – Material that settles within 1 hour – Measured in an Imhoff cone – Easy to perform Indicators of Wastewater Quality Residue in Wastewater: • Total suspended solids (TSS) – Nonfilterable residue Indicators of Wastewater Quality Residue in Wastewater: • Nitrogen – Ammonia, nitrites, nitrates, proteins, – Some forms can be toxic to plants • Total dissolved solids (TDS) – Filterable residue – Hard to eliminate • Phosphorous – Polyphosphates and ortophosphates – Detrimental for aquatic life Waste Management • Solid Waste Disposal Waste Management Solid Waste Disposal – Municipal garbage disposal – Dehydrated and used for animal feed – Composting • Aerobic microbial decomposition process • Organic wastes are mixed with: bark, straw, fall leaves, paper, wood chips • Liquid Waste Disposal Waste Management Solid Waste Disposal: Composting • Stages: 1) Mesophilic 2) Thermophilic 3) Cooling or maturation Waste Management Solid waste disposal: Composting • Steps: 1. Solid waste is comminuted and mixed with other materials 2. Stacked in windrows 2 x 3 m Stacked 3. Aeration provided 4. Re-comminuted Waste Management Liquid waste disposal • General considerations: – Waste: economic and ecological consequences – Waste prevention can be more cost effective – Sanitation: 30% of waste water – Cleaning and sanitizing compounds are toxic Waste Management • Liquid waste disposal Treatment Natural Water Streams Pretreatment Municipal Waste Treatment Waste Management • Liquid waste disposal: Pretreatment – Municipal surcharges based on BOD5, suspended solids and grease – Based on municipal regulations – Grease materials can be an attractive subproduct Waste Management • Liquid waste disposal: Pretreatment • Processes: – Flow equalization • Reduces hydraulic loading of waste stream • Performed in an equalizing tank – Screening • Removal of solids with a screen – Skimming • Removal of floating solids and fat Waste Management • Liquid waste disposal: Treatment Primary: physical Secondary: biological Tertiary: purification Waste Management • Liquid waste disposal: Primary Treatment • Steps: 1) Sedimentation – In tanks – Removes from 40-60% TSS or 25-45% BOD5 2) Flotation – Removes oil, grease and suspended matter – Dissolved air flotation uses air bubbles Waste Management • Liquid waste disposal: Secondary Treatment • Biological oxidation of organic matter • Purpose: Mineralization: convert organic matter to CO2 Mineralization: or CH4, ammonia, nitrate, sulfate, and phosphate Waste Management • Liquid waste disposal: Secondary Treatment • Types: – Anaerobic lagoons – Anaerobic digestors – Aerobic lagoons – Trickling filters Waste Management Waste • Liquid waste disposal: Secondary Treatment • Types: – Activated Sludge – Oxidation ditch – Land application – Rotating biological contactor Waste Management • Liquid waste disposal: Tertiary Treatment • Types: – Physical separation – Physical-Chemical separation – Tertiary lagoons – Chemical oxidations – Disinfection Municipal Wastewater Treatment • City of Oxnard http://www.oxnardwastewater.org/treatment.html http://www.oxnardwastewater.org/treatment.html ...
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