Treatment Technologies ENVM 649: Principles of Waste Management and Pollution Control Dr. Robert Beauchamp

GENERAL CATEGORIES THERMAL TREATMENT PHYSICAL/CHEMICAL TREATMENT BIOLOGICAL TREATMENT CONTAINMENT & DISPOSAL

THERMAL TREATMENT INCINERATION THERMAL ADSORPTION DESTROYS ORGANIC COMPOUNDS, REDUCES VOLUME.CONVERTS LIQUID WASTE TO SOLIDS.HIGH REMOVAL EFFICIENCIES. 900-1500 DEG. C (ROTARY KILN, LIQUID INJECTION). MOBILE OR FIXED. THERMAL ADSORPTION THERMAL DESORPTION: VOLATIZES VOC's. 300-600 DEG. C. PYROLYSIS, & VITRIFICATION PYROLYSIS: CONVERTS VOC's TO COMBUSTIBLE, GAS, CHARCOAL, LIQUIDS AND ASH. 500-800 DEG. C. VITRIFICATION: HIGH TEMPERATURE ELECTRODES MELT THE WASTE. IN-SITU OR EX-SITU. GASES ARE COLLECTED BY A HOOD FOR TREATMENT. 4,000 VOLTS REQUIRED - 3,600 DEG. C. NEED SUFFICIENT GLASS FORMINGMATERIAL. DEEP WATER TABLE.

IN SITU TREATMENT (SOILS) SOIL FLUSHING BIOREMEDIATION VAPOR EXTRACTION SOLIDIFICATION

PHYSICAL TREATMENTS (IN-SITU) SOIL FLUSHING: REMOVING SOIL CONTAMINANTS (ORGANIC/INORGANIC) FOR TREATMENT SOIL WASHING: SIMILAR TREATMENT USING: WATER, ACIDIC SOLUTIONS, & SURFACTANTS

SOLIDIFICATION/STABILIZATION POZZOLAN - PORTLAND SYSTEMS (PHYSICAL ENTRAPMENT) CONTAMINANTS: METALS, PCB’S, OIL SLUDGES, WASTES (VINYL CHLORIDE, RESINS, ASBESTOS, SULFIDES, ETC.) POZZOLANS INCLUDE: FLY ASH, PUMICE, LIME KILN DUST. THERMOPLASTIC TREATMENT: ASPHALT OR POLYETHYLENE - BIND THE WASTE (I.E., SLUDGES, PAINT, RADIOACTIVE MATERIALS, METALS, ORGANICS)

BIOLOGICAL PROCESSES AEROBIC AND ANAEROBIC AEROBIC: MICROORGANISMS NEED A CARBON & ENERGY SOURCE. TEMPERATURE AND PH MUST BE CONTROLLED. NUTRIENTS-NITROGEN, PHOSPHOROUS. PH 6 - 8 IS BEST. NEED O2 AERATION IS REQUIRED. TEMPERATURE > 15 DEGREES C IS BEST.

BIOLOGICAL PROCESSES (cont) ANAEROBIC DIGESTION: ABSENCE OF FREE O2 CONVERTS HYDROCARBONS FROM COMPLEX TO SIMPLER MOLECULES & TO CO2 & METHANE. REQUIRES NO POWER. VERY HIGH ORGANIC DESTRUCTION RATES. METHANE CAN BE OF COMMERCIAL VALUE. LESS LAND REQUIRED. DISADVANTAGES: MAY TAKE A LONG TIME EXPERIENCE LACKING DESIGN CAN BE DIFFICULT A PH = 6 - 8 IS BEST.

VAPOR EXTRACTION/AIR SPARGING IN-SITU AIR STRIPPING PROCESS AIR STRIPPING: REMOVES VOC'S - LIMITED TO 100MG/L VOC'S. HENRY'S LAW GOVERNS EQUILIBRIUM RELATIONSHIP & HELPS DESIGN THE AIR STRIPPER. STEAM STRIPPING: TREATS MORE SOLUBLE, LESS VOLATILE VOC'S, AND HIGHER CONCENTRATIONS OF VOC’S. AIR SPARGING: REMOVES HIGHEST MOLECULE WEIGHT PETROLEUM COMPOUNDS AND CHLORINATED SOLVENTS. AIR IS FORCED BELOW THE H2O TABLE. VAPOR EXTRACTION SYSTEMS COLLECT CONTAMINANT IN THE AIR AFTER BEING BROUGHT TO THE SURFACE.

CHEMICAL PRECIPITATION A SOLUBLE SUBSTANCE IS CONVERTED TO A INSOLUBLE SUBSTANCE. CAN BE REMOVED BY SETTLING OR BY FILTERING. METALS OF CONCERN - ARSENIC, BARIUM, CADMIUM, CHROMIUM, COPPER, LEAD, MERCURY, SILVER, ZINC. SOURCES OF METALS - METAL PLATING AND POLISHING, THE STEEL AND ELECTRONICS INDUSTRY.

CHEMICAL PRECIPITATION PROCESS A PRECIPITANT IS ADDED - HYDROXIDE (LIME) I.E.CALCIUM HYDROXIDE). REMOVES METALS AS METAL HYDROXIDE. METALS PRECIPITATED AS SULFIDES & CARBONATES. DEPENDS ON: CONCENTRATION,PH, PRESENCE OF OTHER MATERIALS. PH OF 9 - 11 IS OPTIMAL CAN REDUCE TO = OR < 1.0 MG/L NOTE: METAL HYDROXIDES ARE AMPHOTERIC (SOLUABLE @ HIGH AND LOW PH).

SULFIDE PRECIPITATION SULFIDES ARE NOT AMPHOTERIC HAVE VERY LOW SOLUBILITIES SOURCES OF SULFIDE INCLUDE IRON SULFIDE & SODIUM SULFIDE. PROBLEM - PH NEEDS TO BE > 8 TO PREVENT FORMATION OF HYDROGEN SULFIDE (TOXIC GAS)

CARBONATE PRECIPITATION NEED A LOWER PH - 7.5 - 8.5 (LOWER THAN THE HYDROXIDE METHOD)

SODIUM BOROHYDRIDE PRECIPITATION  A REDUCING AGENT PH 8-11. GOOD FOR LEAD, MERCURY, NICKEL, COPPER, GOLD.

ELECTROLYTIC RECOVERY WORKS BEST FOR PROCESS STREAMS WITH HIGH CONC. OF METALS. USES ANODE AND CATHODE ELECTRODES. CATHODES ARE IMMERSED IN A CHEMICAL MEDIUM UNDER AN APPLIED POTENTIAL. METAL IONS ARE REDUCED TO ELEMENTAL FORM AT THE CATHODE. ADVANTAGES: METALS RECOVERED FOR REUSE. TOXIC DISCHARGE REDUCED. LOW INITIAL INVESTMENT. LOW OPERATION EXPENSES. MINIMAL MAINTENANCE. DISADVANTAGES: ONLY GOOD FOR STREAMS WITH HIGH CONCENTRATIONS. DEPLETION OF METALS IN STREAMS OFFER RESISTANCE TO CONTINUOUS METAL MIGRATION TO THE CATHODE.  GAS FORMATION @ CATHODES (H & CL).

ACTIVATED CARBON ADSORPTION FOR LIQUIDS AND GASEOUS STREAMS USED WHEN WASTE STREAM IS NOT FULLY UNDERSTOOD. USED IN TREATMENT TRAIN. CARBON CAN BE REUSED GRANULATED CARBON USED IN FLOW THROUGH COLUMNS, AND POWDERED AC IS USED FOR SLURRY REACTIONS.

ACTIVATED CARBON ADSORPTION (cont) 3 PROCESSES: PHYSICAL ADSORPTION-WEAK CHEMICAL ADSORPTION CHEMICAL BONDING ELECTROSTATIC ADSORPTION - ATTRACTIVE FORCES ADSORPTION INCREASES AS SOLUBILITY DECREASES AS MOLECULAR WEIGHT OF THE CONNTAMINANT DECREASES. MICROBIAL ACTIVITY INCREASE DUE TO OXYGEN, NUTRIENTS, & SUBSTRATE MATERIAL. MICROBES MAY HINDER OR ENHANCE ADSORPTION.

ACTIVATED CARBON ADSORPTION (cont) COSTS: CAPITAL COSTS ARE HIGH (INCL. EQUIPMEN COMPRESSORS, CONTROLS, ETC.) OPERATING COSTS ARE LOW. PROBLEM: SOLID ACCUMULATION AND FOULING EXHAUSTS THE CARBON. SOLUTION: REVERSE THE FLOW AND BACKWASH THE CARBON.