Presentation on theme: "CE/Geol/ChE 174 Hazardous Materials Treatment of Commercial and Industrial Hazardous Wastes Christopher Vais 510-610-3396"— Presentation transcript:
CE/Geol/ChE 174 Hazardous Materials Treatment of Commercial and Industrial Hazardous Wastes Christopher Vais
Examples of Industrial Haz. Wastes Photo and X-ray processing – silver rich fixers – developers Electroplating – cyanide – acids – solvents and strippers Paint stripping – methylene chloride – solvents – alkali Wastewater from pulp and paper mills – wood pulp Wastewater from refineries – sour water – phenols
Most HW Generated is Wastewater 238 million tons of haz waste generated in U.S. annually – 90% is wastewater The hazardous constituents in wastewater must be either – treated prior to discharge to a wastewater treatment plant – Collected for disposal at a HW landfill – Collected for treatment off-site
Common Constituents of Industrial Wastewater 1. Suspended solids 2. Soluble organics 3. Toxic organics 4. Heavy metals and cyanide 5. Color and turbidity 6. Nitrogen and phosphorus 7. Refractory substances (resistant to biodegradation) 8. Oil and floating material 9. Volatile materials
Treatment of Industrial Wastewater: Depends on Final Destination Wastewater treatment plant – For additional treatment Directly to the environment – Surface water – Groundwater / aquifer recharge – Direct use
Prior to Discharge to a POTW Water must meet requirements developed by the local POTW for your industrial facility – Discharge limits typically listed in a permit – Periodic sampling and analytical requirements Typical Limits – Biochemical oxygen demand – Suspended solids – Fats, oils and grease – Heavy metals – Toxic organics
Direct Discharge to Water Body Requires a National Pollutant Discharge Elimination System (NPDES) permit Effluent must meet strict standards – Specific to discharger (e.g., a north bay refinery) – Specific to the receiving water (e.g., shallow vs. deep areas of SF Bay)
Types of Waste Treatment CHEMICAL TREATMENT PHYSICAL TREATMENT BIOLOGICAL TREATMENT THERMAL (INCINERATION)
Deciding Amongst Treatment Technologies Partitioning between water and air – What factor or coefficient?? ______________ Partitioning between water and organics – What factor or coefficient?? ______________ Biodegradability – What factor or coefficient?? ______________ Moisture content
Parameters for Selected Priority Pollutants CompoundBiodegradation constant (100 L/mg-hr) Henry’s Law Constant (1000 atm- m3/mole Octanol-Water Partition Coefficient (Kow) Acetone Benzene Chlordane x 10⁵ Hexachloro- benzene 3 x 10⁻⁴ x 10⁶ Tetrachloroethane3 x 10⁻⁴ Vinyl Chloride Chloroform<
Catalysis Increase of rate and mechanism of a chemical reaction dechlorination of chlorinated hydrocarbons complete air oxidation of cyanides
Electrolysis Oxidation or reduction at an electrode surface immersed in a conductive solution under the influence of an applied potential.
Hydrolysis reaction of a salt with water to form an acid and a base XY + Water > HY + XOH Drawbacks? ____________________
Neutralization Adjustment of the pH by addition of either an acid or a base. Continuous or batch reactors
Photolysis breakdown of chemical bonds under UV or visible light Becoming common form of disinfection
Oxidation / Reduction Oxidation – Transfer of electrons from the chemical being oxidized to the oxidizing agent – Common oxidants: ________________________ Reduction – transfer of electrons from the reducing agent to the chemical being reduced, EXAMPLE: reduction of Cr+6 (hexavalent state) to Cr+3 (trivalent state) using sulfur dioxide
Precipitation Change in the solubility of compounds by addition of: 1. ________________________ 2. ________________________ 3. ________________________ 4. ________________________
Physical Treatment Processes Trying to achieve one or more of the following: 1. _________________________ 2. _________________________ 3. _________________________
Physical Treatment Processes Adsorption Air Stripping Centrifugation Distillation Electrodialysis Evaporation Filtration Flocculation, Precipitation, and Sedimentation Flotation Freeze Crystallization Ion Exchange Solidification
Adsorption Separates organics (and some inorganics) from an aqueous waste stream attraction and accumulation of the adsorbate (the organic) contained in water or some aqueous phase onto the surface of a rigid, solid phase (the adsorbent) such as activated carbon.
Air Stripping Volatile components are transferred from a liquid mixture (water) to a gas (air). Driving force: – departure of the vapor-liquid phase concentrations from equilibrium – mass transfer in the direction of decreasing concentration.
Centrifugation Centrifugal force is used to separate liquid from the solid in an enclosed environs. Used to – dewater sludge resulting in a reduction of the sludge volume, reduce slurry volumes Results in an increased solids concentration in the waste streams
Distillation Nondestructive liquid phase separation process used for organic component recovery based on differences in _______________
Electrodialysis Separates ionic components of a waste stream Uses synthetic membranes and an electrical field – membrane is a semi-permeable one, allowing either anions or cations to pass through it – electric field causes separation of positive from negative ions
Evaporation Concentrates the waste and reduces its volume by heating the mixture in pipes, ponds The vapor phase is not collected and/or condensed as in distillation
Filtration Liquid passes through a porous media that traps the solids Typical media: – _________________ Backwash to clean filter
Flocculation, Precipitation, and Sedimentation Removes suspended solids, colloids Enhance conditions for floc formation – Changing solubility of metals – Settling chamber Flocculating particles aggregate or coalesce thereby changing the particle size, shape, and even specific gravity
Flotation (Dissolved Air Flotation) removes solids suspended in the waste – via agitation – sometimes via chemical addition Air bubbles reduce the solid density – Bubbles carry particles to the surface of the tank. A froth or foam forms at the top and contains the solids – removed with a skimmer arm
Freeze Crystallization The waste water is cooled to form purified ice crystals Remaining liquid will be more concentrated The process can be repeated on the same waste to further concentrate
Ion Exchange A synthetic or natural resin material Used to removed dissolved solids Heavy metals and anions attach to the resin surface, exchanged for other anions that were previously on the surface Occurs quickly, unless/until all the exchange sites are filled – “Breakthrough” – requires ______________
Solidification Fixes or encapsulates the waste o Rendering the HW into a nonhazardous solid product Solidifying agents: Silicates Cement-based (Portland is common; results in rock-like solid) Lime-based Thermoplastics Organic polymers
Types of Waste Treatment CHEMICAL TREATMENT PHYSICAL TREATMENT BIOLOGICAL TREATMENT THERMAL (INCINERATION) ULTIMATE DISPOSAL – LAND TREATMENT
REFRESHER: Deciding Amongst Treatment Technologies Partitioning between water and air – Henry’s Law coefficient Partitioning between water and organics – Kow – octanol water coefficient Biodegradability – Biodegradation rate constant Moisture content
Biological Treatment Uses microbes to decompose organic wastes In addition to biodegradation, sorption and stripping also occur.
Aerated lagoons Three types – Well mixed (all aerobic) – Facultative – Settling lagoons 3 to 5 meters deep Treatment efficiency – Oxygen availability – Waste biodegradability – Nutrients (N & P) – Detention time
Activated Sludge Similar to aerated lagoons 2-stage process – Aeration basin – Clarifier Some microbes are wasted, others are returned to the system (“activated”)
Anaerobic Digestion Uses microbes that do not need oxygen to respire Not usually suitable for industrial wastes
Composting Land reclamation, landfarming Biodegradation of organics in the soil Requires collection of leachate and runoff for groundwater protection Can aerate by turning the soil
Trickling Filters Microbes are supported on a solid media structure (e.g., rock, plastic) Wastewater is trickled over the media There is a biofilm layer – Aerobic outer layer – Inner layer may be anaerobic – Waste concentration changes within the biofilm
Waste Stabilization Ponds Dilute industrial wastes Shallow basins – 1 to 2 meters deep Wind provides limited aeration – Deep ponds are anaerobic at the bottom Photosynthetic algae of surface
Prior to Discharge to POTW
Post-Treatment: Equilization prior to discharge to WWTP 1.Prevents shock loading of biological systems by dampening organic fluctuations. 2. Enables better pH control, and can reduce chemical requirements for neutralization. 3. Minimizes flow surges to physical/chemical treatment systems. 4. Provides continuous feed to biological systems 5. Enables controlled discharge to POTWs enabling even distribution of the waste load. 6. Prevents high concentrations of toxics from entering the biological treatment plant too rapidly.
Processes at the WWTP Primary Secondary Tertiary / Advanced
Primary Treatment Physical treatment – settling basins – Use gravity to remove suspended solids Screens, grinders, grit removal
Tertiary/ Advanced Treatment Filtration to remove solids Removal of nitrogen and phosphorus Disinfection – Chlorine gas – UV light
Ultimate Disposal Options Following treatment, remaining wastes often incinerated or disposed to land – Waste streams remaining from wastewater treatment at the industrial site – Solid wastes not discharged to sewer – Solids/sludge from the wastewater treatment plant
Incineration Destroys Structure Destroys molecular structure of waste – Not elemental composition Molecules with more stable structures and stronger chemical bonds require longer residence times and/or higher temperatures “Incinerability” – Based on heat of combustion per unit weight
Incinerator Operating Conditions Combustion temperature Residence time Degree of mixing Presence of excess air
Examples of Incinerators Liquid injection – Any pumpable waste – Converts liquid waste to gas prior to combustion Kilns – Used on solids, liquids, and gases – Many different types (e.g., rotary kilns, cement kilns, lime kilns, aggregate kilns) Calcination or sintering – 1800°C and atmospheric pressure. – Destroys organics; reduces the volume of inorganics
Incinerator Performance Destruction and Removal Efficiency (DRE) – EPA will determine the DRE required for a waste stream – Example: RCRA requires DRE of 99.99% for all “principal organic hazardous constituents”(POHCs) Example: Wastes containing dioxins and furans requires % DRE
Incineration: Needs Air Pollution Control Equipment (APCE) Incomplete combustion – afterburners for exhaust – Combust the exhaust at higher temperature than the combustion of primary waste stream – Example: dioxin and furan creation More toxic than precursors 75 dioxin congeners; 135 furan congeners Particulate control – baghouses, water scrubbers Control of acid formation – HCl from combustion of chlorinated organics
Land Farming Organic wastes only – biodegradation Upper layers of soil Effective, low cost, simple Can enhance soil Degradation factors – Waste Composition – Contact between the waste and the microbes – Soil Temperature – Soil pH – Oxygen – Inorganic Nutrients- N & P – Moisture Content
Landfilling Area filling – Disposal is above ground – Advantages: ____________________________ Trenching – Below-grade – Advantage: ____________________________ Both produce gases (explosion issue) and leachate (GW and SW contamination issue) that must be monitored and treated
Deep Well Injection Transfer of liquid waste deep underground – Far away from freshwater sources Criteria for waste waters: – Low Volume, High Concentration Waste – Difficult to treat by other methods – Compatible with material in disposal zone – Biologically Inactive – Non corrosive Over 9 billion gallons/year HW injected in the US
Five Well Classes
Regulated by U.S. EPA Under the Safe Drinking Water Act Administered by the Underground Injection Control (UIC) program of EPA
Injection Well Operation Requirements (Class I, II & III) Site free of faults & other adverse geologic features Drill below potential drinking water (any water in formation must have TDS > 10,000 mg/L) Double piping: Tubing in Casing – Multiple containment layers Test well integrity every 5 years
California Examples of Permitted Deep Well Injection Class I – California Specialty Cheeses – Hilmar Cheese Class II – Greka Integrated, Inc. (Fined $$ in Summer 2006 for improper use) Class V Experimental – City of Los Angeles
CO2 Sequestration What about Underground Injection as Climate Change Solution??
Geologic Sequestration of CO2 Process of separating and capturing carbon dioxide (CO2) from a source, such as a coal fired electric generating power plant, transporting the CO2, and injecting it through a well into the deep subsurface. Once underground, it is believed the CO2 will be trapped, or sequestered, for a long period of time.
Geologic Sequestration of CO2 Earth has widely-distributed geologic formations which have capacity to store injected CO2 Current estimates indicate that the storage capacity is extremely large and widespread. With proper site selection and management, geologic sequestration could play a major role in reducing CO2 emissions.
Pilot Tests of CO2 Sequestration Currently using Class V experimental technology well classification to pilot the technology Pilot projects will provide information about how CO2 behaves in the sub-surface and additional technical information on proper well construction and operational procedures. The results will be used to decide if there is a need to develop new UIC regulations for commercial-scale CO2 injection projects