Treatment TechnologiesTreatment Technologies

ENVM 649: Principles of Waste Management and Pollution Control

Dr. Robert Beauchamp

GENERAL CATEGORIESGENERAL CATEGORIES

THERMAL TREATMENT

PHYSICAL/CHEMICAL TREATMENT

BIOLOGICAL TREATMENT

CONTAINMENT & DISPOSAL

THERMAL TREATMENTTHERMAL TREATMENT

INCINERATION – 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, & VITRIFICATIONPYROLYSIS: 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)IN SITU TREATMENT (SOILS)

SOIL FLUSHING

BIOREMEDIATION

VAPOR EXTRACTION

SOLIDIFICATION

PHYSICAL TREATMENTS (IN-SITU)PHYSICAL TREATMENTS (IN-SITU)

SOIL FLUSHING:– REMOVING SOIL CONTAMINANTS (ORGANIC/INORGANIC)

FOR TREATMENT

SOIL WASHING:– SIMILAR TREATMENT USING: WATER, ACIDIC

SOLUTIONS, & SURFACTANTS

SOLIDIFICATION/STABILIZATIONSOLIDIFICATION/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 PROCESSESBIOLOGICAL PROCESSES

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.

AEROBIC AND ANAEROBIC

BIOLOGICAL PROCESSES (cont)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 SPARGINGVAPOR 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 PRECIPITATIONCHEMICAL 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 PROCESSCHEMICAL 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 PRECIPITATIONSULFIDE 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 PRECIPITATIONCARBONATE PRECIPITATION

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

SODIUM BOROHYDRIDE PRECIPITATIONSODIUM BOROHYDRIDE PRECIPITATION

 A REDUCING AGENT

PH 8-11. GOOD FOR LEAD, MERCURY, NICKEL, COPPER, GOLD.

ELECTROLYTIC RECOVERYELECTROLYTIC 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 ADSORPTIONACTIVATED 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)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)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.