Waste Treatment

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Waste Treatment and Disposal technology : 

Waste Treatment and Disposal technology Hazardous Materials and Hazardous Waste Management (G. Woodside), Chap. 12

??????????????? : 

???????????????

Slide 3: 

??:??????,?????????????? ??:????? ?? ????:?????????,?????????????????????,????????????????? ????:?????????,??????????????,???????????,?????????????,???????????????????????????????? ????:?????????

Slide 4: 

????:???????????,??????????????,???????(separation)???or??(volume reduction)???or??(detoxification)????(stabilization)???? Purpose:????????????/???,??????????,???????

Slide 5: 

Waste treatment can incorporate several different unit processes a wastewater treatment system include oil-water separation, neutralization, biological treatment, sedimentation and sludge dewatering

Treatment Technology : 

Treatment Technology Physical/chemical process Biological process Thermal process Soil/groudnwater treatment Land-based treatment Based on types of technology or environmental area Many facilities use a combination of several types of treatment.

Treatment Technology : 

Treatment Technology Concentration. A physical treatment. Reduce the volume of hazardous waste; less expensive. Detoxification. Chemical or biological processes. Destroy toxic components or reduces these chemicals to less toxic form; generally more expensive. Fixation/Solidification. Usually a physical treatment. Reduce the mobility of the toxin. Based on characteristic of technology

Concentration: physical treatment basically : 

Concentration: physical treatment basically Purposes: phase change of HW or concentrate ?HW? for further treatment more easily 3 types of technology (purposely) a. Gross removal of contaminant: sedimentation, clarification, precipitation, flotation b. Solid dewatering: centrifugation c. Polishing: filtration, evaporation, ion exchange, peat adsorption, reverse osmosis (RO)

Concentration: physical treatment : 

Concentration: physical treatment Processes: Sedimentation (Gravitational settling) and clarification Carbon Adsorption: activated carbon adsorption Flotation: opposite of sedimentation Centrifugation Distillation Filtration Evaporation Distillation Solvent Extraction Ion Exchange (Resin Adsorption): cation, anion exchange Membrane technologies: Reverse Osmosis (RO), Dialysis, Electrodyalysis Solvent Extraction Stripping

Physical process : 

Physical process Carbon Adsorption Adsorption is the process in which matter (soluble ) is extracted from one phase and concentrated at the surface of a second phase. This is a surface phenomenon as opposed to absorption where matter changes solution phase, e.g. gas transfer.

Adsorption?? vs. Absorption?? : 

Adsorption?? vs. Absorption?? When a substance is attached to a surface is is called adsorption. For example, substance is attached to the internal surface of active carbon. When a substance is absorbed in a different medium it is called absorption. For example, a gas is taken in a solution

Slide 12: 

adsorbate: material being adsorbed adsorbent: material doing the adsorbing. examples are activated carbon (AC)

Activated Carbon : 

Activated Carbon Activated carbon is produced to achieve a very big internal surface (between 500 - 1500 m2/g) Granular activated carbon (GAC): particle diamter ~ 1500µm Powdered activated carbon (PAC): particle diamter < 100µm

Slide 14: 

Carbon adsorption is effective at removing organic compounds with low polarity, high MW, low water solubility and high boiling point. Adsorption of organic, non-polar substances such as: Mineral oil BTEX  Poly aromatic hydrocarbons (PACs) (Chloride) phenol Adsorption of  halogenated substance: Odor Taste Yeasts Various fermentation products

Slide 15: 

Physical adsorption: Van der Waals attraction between adsorbate and adsorbent. The attraction is not fixed to a specific site and the adsorbate is relatively free to move on the surface. This is relatively weak, reversible adsorption. Adsorption capacity for particular compound or mixed wastes is determined as an adsorption isotherm????? and tested in laboratory or a pilot unit.

Slide 16: 

Point C3 the column starts to breaktrough????? and near C4 the column is not purifying anymore. Between point C3 and C4 regeneration ??of the column is needed.

Dissolved Air Flotation(DAF)?? : 

Dissolved Air Flotation(DAF)?? Opposite of sedimentation Separate suspended solids and oil/grease from aqueous streams and to concentrate or thicken sludge Oil or SSs float to surface of a tank by air bubbles. Coagulant chemicals may needed to improve removal efficiency Remove metal hydroxides and oil Applicable only for waste having densities close to that of H2O

Distillation??/ Fractional distillation?? : 

Distillation??/ Fractional distillation?? Separate volatile components by differences in vapor pressures or boiling points among volatile fractions and water If a waste contains a mixture of volatile components with different vapor pressures ? Fractional distillation Separate volatile compounds from nonvolatile components ? Evaporation?? Evaporation is often used to remove residual moisture or solvents

Evaporation : 

Evaporation

??????-????? : 

??????-????? ???????????,??????????????????? ??????????????????,?????????????? ?????????????????,??????????,???????? ???????

Solvent extraction??????? : 

Solvent extraction??????? Mixing of a waste stream with an extraction fluid When distillation is ineffective (mixtures of similar vapor pressures or boiling point) Extraction fluid must be immiscible in the waste stream 2 steps: 1. solvent waste contact 2. Phase separation of liquids

??????????? : 

??????????? ??????????? ?(???????(-OH)???,??????????)???(??2-???3-???4-???????)?????????????? ???????????????,??????????????????????????????? ????????????:??????????????????????????????????????????????????????????

??????????? : 

??????????? ????1-??????? ???????????,?????????????????????????,?????????????,?????????????????? ???????????????2,000 mg/L?????200 L/min?,?????? ????????????,????????????????????????????

Ion Exchange : 

Ion Exchange An adsorption process where ionic species are adsorbed from solution by exchanging places on exchange media (zeolite??) Primarily for metal removal (Ba, Cd, Cr, Cu, Hg, Ni…), nonmetallic ions (NO3-, SO42-, CN-, F-…)

Ion Exchange????? : 

Ion Exchange????? ??????????????????????????????????,???????????,??? ?????,??????? ???????????????? (Ion wars) ????? Cationic exchange + ??

?????? : 

?????? ????1-????? ???????????????? (BF4-)???? ????(??) ??????????,????Pb2+?Sn2+???? ????????,??????BF4-?F-???? ????????????????????????????????

??? : 

??? ??????? ????????(??PC??) ?????????????????????,??????????? ???????????,???????????????? ??????????(??????????????????) ???????????????????????? ????????

??? : 

??? ??????? ????? ?????????????????? ??????????,??????????????????????,?????????????,??????????? ?????????????? ????,????????????????????????,??????????,??????? ?

???(HF)?? : 

???(HF)?? ????????????????????????: ?????~ ??? ??????????????,???????? ??????~ ??? ??????????????????????,????????????,?????????? ???????????Na+/K+ATPase ??????????,????????????;?????????????????,???????

?????? : 

?????? ????1-????? ????????????????????????,????pH???3-3.5?,?????10 mg/L?,?????,??????(regeneratioin) ????????:1-2 N HCl??; ??????:4-5%NaOH?? ???????????????,????BF4-?Pb2+?Sn2+??????????????????,????-???????

Membrane Filtration : 

Membrane Filtration Several processes: Reverse Osmosis (RO), Dialysis, Electrodyalysis based on the driving force (electricity or pressure) to filter particles, ions, or organic molecules through a membrane

??????? : 

???????

Membrane Filtration : 

Membrane Filtration Individual membrane filtration processes can be defined by pore size: Microfiltration??? : 0.1~1.0 µm,????,???? Ultrafiltration???: 0.002~0.1 µm,??????? Nanofiltration????: 0.001~0.01 µm,????????????????? Reverse osmosis???: 0.0005~0.002 µm,?????????????

Membrane technology : 

Membrane technology ?????????????????????????,????????,???????????2-5 %;???????????????? ???????????????,??????????????? ????????????,?????? (fouling??) ???????????1?????(acids, alkalines, oxidizer, detergents or organic solvent);????????????

Neutralization : 

Neutralization pH adjustment of acidic or caustic waste to more neutral range; simply mix acidic wastes with alkali waste to neutralize each other common for wastewater and gases treatment, but less use with solid wastes inexpensive treatment

Neutralization : 

Neutralization Most common neutralizing agents are lime [??, Ca (OH)2]for acidic wastewater and H2SO4 for basic wastewater.

Neutralization : 

Neutralization Neutralization of acid gases with liquid caustic solution ? wet scrubbing???? Flue gas from incineration is scrubbed with soda ash solution (Na2CO3 ) or lime to remove acid gases

Flue gas : 

Flue gas gas that exits to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, boiler or steam generator Often refers to the combustion exhaust gas produced at power plants Contain nitrogen (typically more than two-thirds) derived from the combustion air, carbon dioxide (CO2), water vapor, as well as pollutants such as particulate matter, CO, NOx and SOx

Precipitation?? : 

Precipitation?? Most commonly used for metal removal from aqueous wastewater. Accomplished by pH adjustment or addition of a chemical reagent to forms a precipitant with metal Hydroxide precipitation, sulfide precipitation and carbonate precipitation are the common metal forms. Flouride (F-)can be also removed by precipitation

?????? : 

?????? ????2-??????? ????? ??????????????Ca(OH)2?CaSO4?CaCl2?,???????????? ????:Ca2++2F-?CaF2(s) ? ??? ????????????[PAC,?Al2(OH)n Cl 6-n?m ]????[Al2(SO4)3],??????????,?????????????? Al(OH)3 ?????,?????????????????

?????? : 

?????? ????-?????(??BF4-) ??:????????BF4-???,?????CaF2??????BF4-???????????????,???HF,???Ca2+???CaF2?? ????????????????????????????,????,????????????????????????????????

??????(?) : 

??????(?) ????-?????(???????) ????????,?????????,???????????????? ?????pH?,?????pH???6-7??,?????Al2(SO4)3,??70-95 oC????2??????????,?BF4-???????????????(H3AlF6),????Ca(OH)2,?F-?Ca2+??,??????CaF2?? ??????pH?????8-10??,???????Pb2+?Sn2+?????????????????? ??????????,???????? ???????F-?Pb2+?,???????

?????? : 

?????? ????-?????(??) ??????,?????????(>24 hr),??????????????????????? ??????,???????BF4-?????????????????????? ????-?????(???????) ?????-??????????????,?????????????? ??????????,??????(??24????)

??? : 

??? ??????? ?????????(CrO3 )?????(Cr2O72- )???,?????????? ?pH = 1.5-6.0?,?HCrO4-?? pH = 6.5?,HCrO4-???CrO42- ??pH??,??CrO42-?? ??????????,??????HCrO4-??

??? : 

??? ??????? ?????????????????????? ?????????????????,????????????????? ????????????????? ?????????,??Cr2O3????,???? ???????,???????????????????????????????????? ??????????????????,??????????????????

?????? : 

?????? ????1-?????(?????????) ????????????????pH?,??????????,?????????????,???????????????? ???(????)??????,???????????????: SO2+H2O?H2SO3 ??????????,??????: 2H2CrO4+3H2SO3?Cr2(SO4)3+5H2O

?????? : 

?????? ????1-????? ?????pH??,??pH????????(???) H2SO3?H++HSO3-(Ka=1.72×10-2) HSO3-?H++SO32- (Ka=1.0×10-7) ?pH?,??????????????(H2SO3?????) ?????????(pH<3.0) ??,????????pH

?????? : 

?????? ????1-????? ??????????,???NaOH?Ca(OH)2????,??????Na2SO4?H2SO3?NaHSO3????? Cr2(SO4)3+ 3Ca(OH)2? 2Cr(OH)3+3CaSO4 H2SO3+Ca(OH)2?CaSO3 +2H2O ??????????,pH = 7.5-10.0????????? (???)

Treatment Technology : 

Treatment Technology Concentration. A physical treatment. Reduce the volume of hazardous waste; less expensive. Detoxification. Chemical or biological processes. Destroy toxic components or reduces these chemicals to less toxic form; generally more expensive. Fixation/Solidification. Usually a physical treatment. Reduce the mobility of the toxin. Based on characteristic of technology

Detoxification Technologies : 

Detoxification Technologies concentration processes end up with small volume but concentrated toxic product Purpose: reduce toxicity of end products from concentration processes Chemical or biological processes (concentration usually physical processes): chemical oxidation/reduction, neutralization, incineration, and biodegradation Most of these processes will not reduce the toxicity all the way to zero, but down to certain level only

Oxidation/Reduction : 

Oxidation/Reduction Partial or complete degradation of many organic and inorganic compounds Oxidation : ? the valence of an ion with a loss of e- reduction : ? the valence with a gain of e- render hazardous wastes less hazardous or harmless via addition of strong oxidants (Cl2, O3, H2O2) or reductants (sulfur dioxide SO2, sodium bisulfite NaHSO3, FeSO4, sodium borohydride NaBH4)

Chemical oxidation : 

Chemical oxidation treat many inorganic and organic liquid and solid wastes such as cyanide, alcohol, phenols, biphenyls, organic sulfide, and some pesticides can be a pretreatment for biological treatment; oxidize COD to BOD limit: usually not complete reaction, may produce more toxic product Factors affect oxidation: pH, type and quantity of oxidizable compounds, metals (can react with oxidants) Example: cyanide-bearing wastewater from metal-finishing industry is typically oxidized with alkaline chlorine or hypochlorite solutions

??? : 

??? ??????? ????????(NaCN)???(HCN) ??????????,????????????????????????? ?????????,????????????????,???????????????(1),HCN????,?pH???(2): (1)NaCN+H2O?HCN+NaOH (2)HCN?H++CN-(Ka = 4.8 × 10-10,25?)

?????? : 

?????? ????-??? ????? (?????) ???????: ????:C12+2OH-+CN-?CNO-+2C1- + H2O ????:3C12+6OH-+2CNO-?2HCO3- +N2+6Cl-+2H2O ??? (cyanate) ??? Fast Slow

??????(?) : 

??????(?) ?????????????????(cyanogen chloride, CNCl)????,?????: ???1 :CN-+OCl-+H2O?CNCl+2OH- ???2:CNCl+2OH-?CNO-+Cl-+H2O ???:CN¯+OCl¯?CNO¯+Cl¯ ????????????????(ORP)???

??????(?) : 

??????(?) ?????– ????????? ??????????NaOCl????????,??????pH=10-12.5?????????,?????????????0.3-1.0 g/L,?????????CO2?N2 (???????? ) ????????????????,??????,?????????,(??:Ni+ ? Ni2+,Fe2+ ? Fe3+,Cr(?) ? Cr(?)?) ,?????????????

Other oxidants : : 

Other oxidants : Ozone (O3) light blue gas, a powerful oxidizing agent advantage : avoidance of chlorinated by-products of using Cl. Excess O3 decomposes to O2 (half-life in H2O @20oC: 20 minutes, @ 20oC: 15 minutes) Disadvantage: Short half-life in H2O Low water solubility Can be generated only on-site, high electrical cost

How is ozone produced? : 

How is ozone produced? principally O3 is produced by irradiation of dry air wit Ultra-violet light just like that occurs naturally from the sun in the upper atmosphere producing O3 layer

Other oxidants : : 

Other oxidants : Hydrogen Peroxide H2O2 one of the most powerful oxidizers Oxidize many organic compounds via hydroxy radical (·OH)

Advanced Oxidation Processes (AOPs)?????? : 

Advanced Oxidation Processes (AOPs)?????? active intermediates (·OH free radicals….) were produced during redox reaction to destroy target hazardous compounds usually for treatment of recalcitrant organics (benzene, phenol, chlorophenol, toluene, xylene…)

Slide 62: 

example: Fenton Fe2+ + H2O2 ? Fe(OH)2+ + OH? ? Fe3+ + OH? + OH- Fe2+ : catalyst H2O2: oxidant - pH controlled at acidic condition (pH 2 ~ 3) others: UV/O3, O3/H2O2, UV/H2O2, O3/TiO2

Chemical Reduction : 

Chemical Reduction hexavalent chromium (Cr+6), Hg, Pb Cr+6: highly toxic, generated from metal finishing industry “Hex chromium” is reduced to comparatively innocuous trivalent chromium, Cr+3 by SO2 SO2 + H2O ? H2SO3 2 CrO3 + 3 H2SO3 ? Cr2(SO4)3 +3 H2O Cr2(SO4)3 + 3 Ca(OH)2 ? 2 Cr(OH)3(s) ? + 3 CaSO4 not applicable for organic waste reduction Chromic hydroxide

Photolysis (??) : 

Photolysis (??) light energy (UV) to break up chemical bonds of hazardous material treatment of pesticides and dioxin (in the presence of hydrogen): Dehalogenation reaction (????) Aryl-H + RCl Aryl-Cl + RH h?

??????????? : 

??????????? ????2-?????? ?????????????(direct photolysis)?????(indirect photolysis),??????????????????????????????????????????????? ??????????????????,?????????????????????,??????????????????????????????,????????????????,???????(???????)

Electrolysis ??\ : 

Electrolysis ??\ recovery of metals in wastewater metal ions ? metal molecules on cathode treat high concentration of cyanide, heavy metal-containing wastewaters

Wet Air Oxidation ????? : 

Wet Air Oxidation ????? Oxidation of soluble or suspended components in water using oxygen as the oxidizing agent. When air is used as the source of oxygen the process is referred to as wet air oxidation (WAO) oxidation reactions occur at temperatures of 150º C to 320º C and pressures from 10 to 220 bar (150 to 3200 psig) to oxidize organics and some inorganics (cyanide or ammonia ) in aqueous wastes in presence of catalyst At these elevated temperature and pressure, the solubility of oxygen in water is dramatically increased, thus providing a strong driving force for the oxidation. system must be maintained under pressure to avoid excessive evaporation of water

Wet Air Oxidation : 

Wet Air Oxidation Operating parameters: temperature, pressure, oxygen concentration, residence time

Wet Air Oxidation : 

Wet Air Oxidation Suitable for high strength of industrial wastewater (COD of 10,000 to over 100,000 mg/L) Waste must be in the liquid phase. Limited to wastewaters containing oxidizable organic and inorganic compounds. For example, WAO cannot destroy PCBs, some halogenated aromatics and some pesticides. High energy input, expensive

Biological processes : 

Biological processes Detoxification process Utilize degradation?? capability of natural decomposer – microorganism (bacteria, actinomycetes, fungi) under engineering controls to break down hazardous wastes to innocuous metabolites apply only to water-containing, biodegradable organic wastes. Generally for removal of organic pollutants from wastewater having low-to-moderate concentrations of simple organic compounds (aliphatic, oil) or lower concentration of complex compounds (aromatic, phenolic, cyanide)

Biological processes : 

Biological processes Most are aerobic processes (in presence of oxygen), some are anaerobic (without oxygen) Biodegradation products: Aerobic: CO2, NH3, NO3-, SO42- ,H2O and biomass Anaerobic: CO2, CH4, NH3, H2S ,H2O and biomass

Biological removal of hazardous wastes : 

Biological removal of hazardous wastes Harvesting cells

Biodegradability ?????? : 

Biodegradability ?????? Aliphatic hydrocarbons ? easily degrade Substituted group ? increase refractory (persistent) Aromatic ? not so difficult Halogenated aromatic ? increase refractory Polymer ? hard to degrade

Refractory, persistent, recalcitrant compounds ???????? : 

Refractory, persistent, recalcitrant compounds ???????? biodegradation-resistant compound; includes many xenobiotic compounds & some natural products such as humus, lignin. usually toxic to cells (including microbes), so compound may kill microbes that could potentially degrade them if it is too concentrated Including: Halides high-branched molecules low solubility compounds

General guidelines for biodegradability : 

General guidelines for biodegradability Aliphatic with carboxyl (-COOH), ester (-COO-R) or hydroxyl (-OH) groups ? readily biodegradable Compounds with carbonyl (-C=O-) group or double bond ? moderately biodegradable (slow for acclimation?? ) Compounds with amino (NH2-R) or hydroxyl group decrease biodegradability relative to degree saturation (1o >2o >3o) Biodegradability decreases with increasing degree of halogenation Biodegradability: aliphatic > aromatic > halogenated aliphatic > halogenated aromatic

Biological processes : 

Biological processes Liquid/slurry-phase treatment: activated sludge????, aerated lagoon???, contact stabilization pond?????, Extended aeration?????, trickling filter???, rotating biological contactor????? (RBC), sludge digestionj???? Solid-phase treatment: composting???, land farming??? On-site (In-situ) vs. Off-site (Ex-situ) treatment Require more sophisticated operational controls: microbes sensitive to rapid change of wastes concentration or feeding rate.

Process control parameters: : 

Process control parameters: Hydraulic Retention Time (HRT) the average length of time the wastewater remains in a reactor HRT = Volume of aeration tank(V)/influent flowrate (Qin) MLSS/MLVSS: microbes concentration in the reactor Food/Microorganism ration (F/M ratio???) ?Sludge loading ratio (SLR, ?????) BOD (or COD) in the influent divided by MLVSS in the reactor Measurement of organic loading on the system A high F/M leads to high oxygen consumption, insufficient treatment; low F/M encourage filamentous organisms to predominate, leading to poor settleability Other parameters: Mean cell residence time [MCRT???????? or Sludge residence time (SRT), Sludge age], pH, DO

Thermal processes : 

Thermal processes destroy, break down or aid in desorption of contaminants in gases, vapors, liquids, sludges and solids. Most are incineration?? processes: combust HW in the presence of oxygen @ T= 800~1650oC Materials become ash Process: catalytic oxidation (typically use metal oxides as catalyst, Pd or Pt), Fluidized Bed????, Liquid injection???????? , Rotary kiln??????? , Multiple Hearth??????

Slide 79: 

Fluidized Bed incinerator Liquid injection incinerator

Slide 80: 

Rotary kiln incinerator???????

Incineration offers: : 

Incineration offers: the destruction of waste, the production of energy from waste the disposal of hazardous waste Products of incineration: gaseous: CO2, H2O, SOx, POx, HF, HCl, HBr, I2, also present are metal oxides and traces of unburnt waste solids: Fly Ash??(metals, oxides and non-combustibles

Incineration control parameters: : 

Incineration control parameters: Temperature?? : 900 – 1100oC will destruct hydrocarbon, 1100 to 1300°C are needed for chlorinated solvents and other wastes which are difficult to incinerate; below 900°C hazardous by- products (dioxins and furans???) will formed. Residence Time???? : hold the waste at high temperatures for sufficient time to ensure destruction (gas, 2 sec; solid, min~hrs) Turbulence or mixing?? : enables waste and air to be well mixed, should be maximized so that contact between the waste and the oxygen in air is as high as possible ? ?????3T

Stabilization Technology (Solidification, Fixation ) ?????? : 

Stabilization Technology (Solidification, Fixation ) ?????? Desinged to limit or reduce the ultimate release of hazardous material from a waste; usually for liquid or semi-solid wastes (sludge) Accomplished by reducing the solubility of the hazardous materials ? reduce the mobility of the toxin Done by mixing (or fixing) hazardous wastes with a nonleachable matrix, then ship the matrix to TSDF or hazardous waste landfill Required for hazardous wastes containing heavy metals

Process Classification : 

Process Classification Cement-based process: ????????????????? Lime-based process: ??, CaCO3??? Thermoplastic process: paraffin??, polyethylene, bitumen, asphalt as solidifying agent Organic polymer process: urea-formaldehyde, polyester, polyethylene Self-cementing process: pozzolanic material Encapsulation: microencapsulation & macroencapsulation

???????? : 

????????

Final Disposal of Hazardous Waste : 

Final Disposal of Hazardous Waste Landfill developed previously for the disposal of municipal refuse ? Sanitary landfill as an alternative to the open dump Hazardous Waste Landfills (secure landfill): bury pretreated hazardous wastes in a landfill constructed with low-permeable soil material (clay) or synthetic non-leachable liners (butyl rubber, chlorinated polyethylene…), along with a leachate collection system and a final cover 3 classes of disposal site (for hazardous and non-hazardous)

Classes of Disposal Sites : 

Classes of Disposal Sites Class I – ?????Waste Management Units for hazardous Waste accept only hazardous waste treatment residues sites must be designed and constructed very carefully, includes groundwater monitoring wells, leak detection system, liners (double-layered), leachate collection systems and covers U.S.: Utah, Idaho, Nevada, Washington

Classes of Disposal Sites : 

Classes of Disposal Sites Class II – ?????Waste Management Units for Designated wastes allow only certain solid hazardous wastes (asbestos, construction debris, low-level contaminated soil) have least control system

Classes of Disposal Sites : 

Classes of Disposal Sites Class III – ?????Landfill for Nonhazardous Waste accept common household trash and other nonstable wastes? municipal landfill simply bury with only a few control system (leachate collection, groundwater monitoring) hazardous waste disposal in a Class III site is against the law

Slide 90: 

Class II Class III Class I