Envi Chapter 7

University of San Carlos - Department of Chemical Engineering

University of San Carlos - Department of Chemical Engineering

Types of Solid Wastes 3 General Categories Municipal Wastes Food wastes – the animal, fruit, or vegetable residues resulting from the handling, preparation, cooking and eating of foods Rubbish – combustible and noncombustible solid wastes, excluding food wastes or other putrescible materials Ashes and residues – materials remaining from the burning of wood, coal, coke and other combustible wastes Demolition and construction wastes – wastes from razed buildings and other structures Special wastes – wastes such as street sweepings, roadside litter, catch-basin debris, dead animals, and abandoned vehicles Treatment-plant wastes – the solid and semisolid wastes from water, Wastewater, and industrial-waste treatment facilities

University of San Carlos - Department of Chemical Engineering

Industrial Wastes - wastes arising form industrial activities and typically include rubbish, ashes, demolition and construction wastes, special wastes, and hazardous wastes

Hazardous Wastes - wastes that poses a substantial danger to human, plant, or animal life - exhibits any of the following characteristics: ignitability; corrosively; reactivity or toxicity

University of San Carlos - Department of Chemical Engineering

Sources of Solid Wastes Municipal Wastes Table 1. General Sources of Municipal Solid Wastes Source

Typical facilities, activities, or Locations where wastes are generated

Types of solids wastes

Residential

Single family and multifamily dwellings, low-, medium-, and high-rise apartments, etc.

Food wastes, rubbish, ashes, special wastes

Commercial

Stores, restaurants, markets, office buildings, hotels, motels, prints shops, auto repair shops, medical facilities and institutions, etc.

Food wastes, rubbish, ashes, demolition and construction wastes, special wastes, occasionally hazardous wastes

Open Areas

Streets, alleys, park, vacant lots, playgrounds, beaches, highways, recreational areas, etc.

Special wastes, rubbish

Treatment plant Sites

Water, wastewater, and industrial treatment processes, etc.

Treatment-plant wastes, principally composed of residual sludges

University of San Carlos - Department of Chemical Engineering

Hazardous Wastes - generated in limited amounts throughout most industrial activities - spillage must also be considered

University of San Carlos - Department of Chemical Engineering

Properties of Solid Wastes Physical Composition Individual Components Food wastes, paper, cardboard, plastics, textiles, rubber, leather, wood, garden trimmings, glass, tin cans, nonferrous metals, ferrous metals, dirt, ashes brick, etc. Particle Size Important in the recovery of the materials Moisture Content Express as the mass of moisture per unit mass of wet or dry material Density Vary with geographic location, season of the year, and length of time in storage

University of San Carlos - Department of Chemical Engineering

Chemical Composition 4 Important Properties for Solid waste to be used as Fuel 1. Proximate Analysis (a) Moisture (loss at 1050C for 1 hr) (b) Volatile Matter (additional loss on ignition at 9500C) (c) Ash (residue after burning) (d) Fixed Carbon (remainder) 6. Fusing Point of Ash 7. Ultimate Analysis 8. Heating Value (Energy Value)

University of San Carlos - Department of Chemical Engineering

Solid-Waste Management: An Overview Materials Flow in Society Raw Material

Residual debris

Manufacturing

Residual waste material

Processing and Recovery

Secondary Manufacturing Consumer

Final Disposal Raw materials, products and recovered materials Waste materials

University of San Carlos - Department of Chemical Engineering

Reduction in Raw Materials Usage Reduction in Solid-Waste Quantities Reuse of Solid-Waste Materials Materials Recovery Energy Recovery Day-To-Day Solid-Waste Management

University of San Carlos - Department of Chemical Engineering

SEPARATION The wastes that are desirably separated at source are: • Food wastes • Paper and cardboard • Plastic • Metals ferrous • Metals non-ferrous • Glass

All other household waste that can be delivered to drop-off centers include: • Bulky waste • Yard waste • Hazardous household waste

University of San Carlos - Department of Chemical Engineering

Requirements for Source Separation Infrastructure required: • Community drop-off centers • Public drop-off centers ( civic amenity centers) • Environmental advertising programmes

Manual and Mechanical Sorting Manual sorting – can only be recommended for clean, dry and more or less pre-sorted waste Mechanical sorting – more commonly used for all fractions can be sorted

University of San Carlos - Department of Chemical Engineering

Storage and Transport of Solid Waste The type of storage used depends on the collection facility, which may be: • Doorstep Collection • Regular kerb collection • Civic amenity drop-off • Haulier for skip collection of bulky items • Community recycle bins • Vacuum trucks

University of San Carlos - Department of Chemical Engineering

Biological Solid Waste Treatment Three options for biological solid waste treatment: • Aerobic or composting • Anaerobic or biogas • Combined anaerobic and aerobic

Composting

organic matter + O2 aerobic  bacteria → new cells + CO2 + H 2O + NH 3 + SO4 Process Requirements • Temperature • Moisture Content • Oxygen • C/N ratio • pH • Biochemical composition and texture

University of San Carlos - Department of Chemical Engineering

Temperature • Psychrophilic – 15 to 200C • Mesophilic – 25 to 350C • Thermophilic – 50 to 600C Moisture Content Optimum moisture content – 50 to 60% Oxygen Optimum oxygen levels – 15 to 20% C/N ratio Optimum ratio – 30 pH Optimum pH – 6 to 8 Biochemical Composition and texture

University of San Carlos - Department of Chemical Engineering

Environmental Parameters • Heavy metals • Odor • Sterilization • Inert Contaminants

Anaerobic Digestion bacteria organic matter + H 2O anaerobic   → new cells + CO2 + CH 4 + NH 3 + H 2 S

Processes Involved • Hydrolysis • Acidogenis • Methanogenesis

University of San Carlos - Department of Chemical Engineering

Process Requirements

• Be oxygen free • Not to contain inhibiting salts • Have a 6.5 < pH < 7.5 • Be of adequate alkalinity, 1500 to 7500 mg/L • Have sufficient nutrients • Be temperature steady at either mesophilic or thermophilic conditions • Have constant solids loading rate

University of San Carlos - Department of Chemical Engineering

Two-Stage Anaerobic and Aerobic Methods • No external water is needed for producing a slurry feedstock to the anaerobic digester. • No effluent water is produced. • There are high rates of biogas production. • A stabilized humus product is produced. • A refuse derived fuel is produced.

Mixer

Thermal Energy Biogas

Air

Digested sludge

Organic Solid Waste

Blend tank

High solids anaerobic digester

Aerobic composter

Humus Dryer Soil Amendment

Plug flow reactor

Aerobic reactor

Flow diagram for combined treatment or organic solid waste and municipal sludge.

Refuse Derived Fuel

University of San Carlos - Department of Chemical Engineering

Thermal Treatment – Combustion/Incineration

Gasification – degradation takes place with a deficit of oxygen Pyrolysis – if the gasification is dry distillation

Combustion – thermal degradation with excess oxygen Incineration – chemical oxidation at high temperatures

1870s in United Kingdom - first waste incineration plant was built

University of San Carlos - Department of Chemical Engineering

Design Principles for Waste Incinerators

Incinerator

University of San Carlos - Department of Chemical Engineering

Design Principles for Waste Incinerators Unloading and storage of waste Crane Hopper and feeding system Grates Furnace Air Supply Boiler system Slag and ash removal

The combustion Process in Waste Incinerators • Drying • Gas pyrolysis and gas combustion • Combustion or carbon residue

University of San Carlos - Department of Chemical Engineering

Air Emission and Flue Gas Cleaning

Flue Gas

Water

R E A C T O R

Chimney Stack

Bag Filter

Residue

Hydrated lime Silo

Layout for a dry flue gas cleaning process.

Container

University of San Carlos - Department of Chemical Engineering

Solid Waste Landfill

University of San Carlos - Department of Chemical Engineering

University of San Carlos - Department of Chemical Engineering

Hazardous Wastes Ignitable - the substance causes or enhances fire Reactive - the substance reacts with others and may explode Corrosive - the substance destroys tissues or metals Toxic - the substance is a danger to health, water, food and air Task of an Environmental Engineer.... - identify the hazardous waste streams - for each stream, quantify the waste - for each stream, characterizing the waste according to whether its form is physical, chemical or biological - recommending waste minimization measures - identifying hazardous waste treatment options - specifying safe disposal routes for waste residues of treated waste

University of San Carlos - Department of Chemical Engineering

Hazardous Wastes

A solid waste that may cause or significantly contribute to an increase in mortality or an increase in serious irreversible or incapacitating reversible illness; or pose a substantial present or potential hazard to human health or the environment when it is improperly treated, stored, transported, dispose of or otherwise manage; and the characteristic can be measured by a standardized test or reasonable detected by generators of solid waste through their knowledge of their waste. (USEPA)

University of San Carlos - Department of Chemical Engineering

Table 2. EU hazard categories of hazardous waste

Hazard Category H1 H2 H3A H3B H4 H5 H6 H7 H8 H9 H10 H11 H12 H13 H14

Directive 91/689 Explosive Oxidizer Highly flammable Flammable Irritant Harmful Toxic Carcinogenic Corrosive Infectious Teratogenic Mutagenic Water contact liberates toxic gas Source of hazardous substance Ecotoxic

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Hazardous waste generated around your house... antifreeze batteries brake fluid chemical strippers chlorine bleach contact cement drain cleaners fire extinguisher flea collars and sprays prescription drugs toilet cleaners

herbicides insect repellent insecticides kerosene lawn chemicals lighter fluids lye moth balls nail polish remover old propane tank spot remover used motor oil

University of San Carlos - Department of Chemical Engineering

Medical Hazardous Waste - Obsolete medicines past the expiry date - Cytostatica with a special demand for careful handling - Infectious material - Pathological waste - Sharp and pointed items - Waste from dental clinics

University of San Carlos - Department of Chemical Engineering

Hazard Symbols for Chemicals

Explosive (E)

Toxic (T)

Oxidizing agent (O)

Very Toxic (T+)

Corrosive (C)

Highly Flammable (F)

Harmful (Xn)

Dangerous for the environment (N)

Extremely Flammable (F+)

Irritant (Xi)

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Warning Labels for Transport of Dangerous Goods

Explosives

Flammable Solids

Radioactive Material

Gases

Oxidizing substance

Corrosive

Flammable Liquids

Toxic substance

Miscellaneous

University of San Carlos - Department of Chemical Engineering

Warning Labels for Transport of Dangerous Goods

Cryogenics

Magnetic Material

This Way Up

Cargo Aircraft Only

University of San Carlos - Department of Chemical Engineering

University of San Carlos - Department of Chemical Engineering