Physico chemical processing of

(hazardous) waste

WASTE

MANAGEMENT

AND

TECHNOLOGY

Martin Kubal

Mecislav Kuras

Institute of Chemical

Technology in Prague

Waste is classified as hazardous if:

- it is listed in the Hazardous Waste List;

- it is mixed with or contaminated by any of the components listed in the

Hazardous Waste List;

- it should display one or more of the hazardous properties.

Cause of hazard – occurence of dangerous chemicals and their mixtures.

Most dangerous – hazardous waste from industry, especially from chemical

industry and other industries dealing with chemical processes (metallurgy,

pharmacy, petrochemistry, glass, machinery, etc.) containing mixtures of

chemicals often of unknown composition and origin.

Treatment of them requires special approaches with higher cost and health and

environmental risk.

Effects: Hazardous waste is a waste which may pose a substantial present or

potential hazard to human health or the environment when impropoperly treated,

stored or disposed of, or otherwise mismanaged.

hazardous waste origin and effect

hazardous waste – EU definition

Council Directive 91/689/EEC of 12 December 1991 on hazardous waste:

For the purpose of this Directive 'hazardous waste` means:

- wastes featuring on a list to be drawn up in accordance with the procedure laid down

in Article 18 of Directive 75/442/EEC on the basis of Annexes I and II to this Directive,

not later than six months before the date of implementation of this Directive. These

wastes must have one or more of the properties listed in Annex III. The list shall take

into account the origin and composition of the waste and, where necessary, limit values

of concentration. This list shall be periodically reviewed and if necessary by the same

procedure,

- any other waste which is considered by a Member State to display any of the

properties listed in Annex III. Such cases shall be notified to the Commission and

reviewed in accordance with the procedure laid down in Article 18 of Directive

75/442/EEC with a view to adaptation of the list.

Properties of wastes which render them hazardous*explosive, oxidizing, highly flamable, flamable, irritant, harmful, toxic, carcinogenic,

corrosive, infectious, teratogenic, mutagenic, substances and preparations which

release toxic or very toxic gases in contact with water, air or an acid, substances and

preparations capable by any means, after disposal, of yielding another substance, e.g. a

leachate, which possesses any of the characteristics listed above, ecotoxic

*see appendix at the end of presentation

The total amount of waste produced in the European Union is currently about

1 800 000 000 tonnes per year. Approximately 90 000 000 tonnes of this waste is

hazardous.

Czech Republic in 2010*:

hazardous waste - production

total (tons) category of waste

hazardous

(tons)

other (tons)

production of waste 24 123 560 1 370 679 22 752 881

manufacturing industry

(including chemical industry)

4 202 463 550 376 3 652 088

waste and water management 2 507 187 550 690 1 956 497

municipal waste 3 334 240 5 028 3 329 212

* Statistical Yearbook of the Czech Republic

hazardous wastes - significant part of industrial wastes,

especially wastes of chemical character

The approach used to develop systems to treat and dispose of industrial

wastes is distinctly different from the approach used for municipal wastes.

There is a lot of similarity in the characteristics of wastes from one

municipality, or one region, to another. Best approach to designing a

treatment system for municipal wastes is to analyze the performance

characteristcs of many existing municipal systems and deduce an optimal

set of design parameters for the system under consideration.

In the case of industrial wastes, however, few industrial plants have a high

degree of similarity between products produced and waste generated.

Therefore, emphasis is placed on analysis of the wastes under

consideration, rather than on what is taking place at other industrial

locations.

character of industrial wastes

Wastes from industries are customarily produced as:

- liquid wastes (process wastes, which go to an on-site or off-site

wastewaster treatment systems),

- solid wastes (including hazardous wastes, which include some liquids)

- air pollutants

These wastes are managed and regulated differently depending on the

characteristics of the wastes and process producing them. The three phases

of wastes are closely interrelated, both as they are generated and managed

by individual industrial facilities. Industrial wastes that are discharged to

neither air nor water are classified as solid, industrial or hazardous wastes.

Interrelation of industrial wastes categories - examples

Solid wastes disposed of in the ground can influence the quality of

groundwater and surface waters by way of leachate entering groundwater

and traveling with it through the ground, then entering a surface water body

with groundwater recharge.

Volatile organics in that recharge water can contaminate the air. Air

pollutants can fall out to become surface water or groundwater pollutants,

and water pollutants can infiltrate the ground or volatilize into the air.

Additionally, waste treatment proces can transfer substances from one of the

three waste categories to one or both of the others.

Waste treatment or disposal systems themselves can directly impact the

quality of the air, water or ground.

Methods for treating industrial liquid wastes -

three categories

Chemical methods - changing the chemical structure involve

exchanging or sharing electrons between atoms.

Physical methods - without necessarily changing the chemical

structure of substances.

Biological methods - involve living organisms like bacteria or other

microorganisms using organic or, in some instances, inorganic

substances for food. In so doing , the chemical and physical

characteristcs of the organic and/or inorganic substances are changed.

In being so used, complex organic molecules are systematically

broken down, than reassembled as new cell protoplasm.

Treatment of air discharges from industry

The discharge, or release, of substances to the air, no matter how slight, is

regarded as air pollution. Discharge can be direct, by means of a stack,

vent, hood, or the like, or indirect, by way of leaks from a building´s

windows, doors, or other openings(fugitive emissions). Fugitive emission

must be considered to evaluate a facility total emissions.

Methods used for controlling particulate emissions:

- gravity and inertial separators, including so-called cyclones are dry, „no-

moving parts“ devices. They take advantage of the relatively high specific

gravity of certain types of particulate matter, incl. fly ash, dust, cement

particles, and organic solids,

- electrostatic precipitators which take advantage of the electrostatic

charge on the surface of particles

- fabric filters, which make use of physical blocking and adsorption,

- wet scubers, which make use of a liqiud to entrap particulate, thus

removing them from a gas stream.

Solid waste treatment and disposal

If a manufacturing process generates „scrap“ that cannot be reused, it may

be treated as solid waste. When a final residue is produced that cannot be

further treated or disposed of economically on-site, it must be shipped off-

site for disposal.

Disposal of final treatment residues and plant wastes in general depends on

the source and chemical characteristic of the waste material itself. Thus, the

first step is to determine into which category the waste belongs:

- hazardous waste, having one of the hazarous properties determined by

law,

- nonhazardous solid waste.

There are a lot of industrial wastes that must be classified as hazardous

wastes. Hazardous wastes are typically the most toxic, expensive and

regulated type of industrial waste.

Industrial nonhazardous waste do not meet the definition of hazardous

waste, but they are excluded from most municipal landfills because of their

physical and chemical characteristics.

„Physico-chemical treatment“ is defined in the EU legislation (Directive

2008/98/EC, which repealed Directive 2006/12/EC) as a waste disposal

operation:

„D 9 Physico-chemical treatment not specified elsewhere in this Annex which

results in final compounds or mixtures which are discarded by means of any of the

operations numbered D 1 to D 12 (e.g. evaporation, drying, calcination, etc.)“

Physical and chemical treatments are strongly interrelated. For example a

precipitate of a hazardous waste compound formed by a chemical reaction

is separated from the reaction mixture by physical means such as

sedimentation and filtration.

In order to characterize wastes for physical treatment, it is necessary to

know their chemical properties – pH of wastewater or the chemical

properties of solids that may be dangerously reactive when produced by

the drying of sludges.

Physico-chemical treatments of hazardous waste

Physico-chemical treatment is applied mostly for industrial waste of

chemical character.

One of the first steps to consider in waste treatment is separation, which

can save tremendous amount of effort and expense by resagregating

wastes in forms that can be treated most economically or which may be not

even hazardous. Separation may be as simple as draining an aqueous layer

from organic one in two-phase waste.

Methods of physical treatment

Physical treatment of wastes depends upon the physical properties of the

material treated, as state of matter, solubility in water and organic solvents,

density, volatility, boiling point and melting point. It consists especially of:

phase separation, sedimentation, filtration, membrane separation

(reverse osmosis, nanofiltration, ultrafiltration), sorption by activated

carbon or resin, distillation and stripping, drying and evaporation,

extraction

Physico-chemical waste treatment

Physical, chemical and biochemical treatment option from these three areas are

strongly interrelated. For example, a precipitate of a hazardous waste

compound formed by chemical reaction is separated from the reaction mixture

by physical means, such as sedimentation or filtration.

Before considering physical treatment and their treatment options it is useful to

have an overview of the various kinds of treatment to which hazardous

substances may be subjected, including their advantages and disadvantages.

Safety dictates that the first thing to do with hazardous waste is to consider any

acute hazards that it may pose and take appropriate preventive actions.

Important examples are cyanides and sulfides, which can react with acids or

hydrolyze to give toxic HCN or H2S respectively. Reactive wastes must be

treated with the appropriate reagents to reduce their hazards. One of the first

step to consider in waste treatment is separation.

Separation frequently results in resource recovery that yields materials of

economic value. For example separation of hazardous substances sorbed to

spent activated carbon can give an carbon product that can be reactivated and

used again.

Treatment options

Separation of components of a mixture that are already in two different

phases.

Sedimentation and decantation are easily accomplished with simple

equipment. In many cases the separation must be aided by mechanical

means, particularly filtration or centrifugation. Flotation is used to bring

suspended organic matter or finely divided particles to the surface of a

suspension. Many wastes are composed of aqueous / organic mixtures in

colloidal sized emulsion. An important and often difficult waste treatment

step consists of separation of these components, a process called emulsion

breaking. Acids (including waste acids), other chemical reagents and heat

may all be employed for this purpose.

Once an emulsion is broken, centrifugation can be used to separate the

phases.

Methods of physical treatment

Mixture of undesirable substances or „pollutants“ in water.

Lot of wastes (especially industrial) are in a form of solution or emulsion.

Solution – one or more substances (solutes) dissolved in another medium

(solvent).

When dissolved, the solutes become distributed uniformly throughout the

solvent volume.

Substances that ionize into cations and anions (e.g. sodium chloride) are

soluble in polar solvents such as water (hydrophilic substances).

Substances that do not ionize (oils) are poorly soluble in polar solvents but

highly in non-polar solvents (hydrophobic substances).

Emulsions – hydrophobic substances can be induced to go into a state that is

equivalent in many way to a water solution by emulsification. Emulsion is

equivalent to solution in that it consists of a stable mixture that will not separate

under quiescent conditions. As a mixture flows from one place to another , it

does not change in character. Two ways to accomplish emulsification:

- with emulsifying agent (detergent)

- to mix hydrophobic substance with water together vigorously

Emulsion decomposition (water and oil phases) – heating or aditives.

Waste forming aqueous / organic mixtures

Stable mixture – pollutants will not settle out of water under gravity

(sedimentation).

To treat water – another processes than simple sedimentation.

Effective treatment process – need to recognise forces responsible for the

mixture stability.

Five general types of mixtures:

1. true solution – stability arises from hydrogen bonding between water

molecules and electrical charge of each ion

2. emulsion – caused by emulsifiyng agent (detergent) – link of small

droplets of liquid substance to water – one agent portion dissolved in

water another dissolved in droplets of pollutant

3. emulsion in which stability of droplet pollutant mixture in water arises from

repulsion caused by like electric charges in the droplet surface

4. colloidal suspension – small particles of nonsoluble solid are held away

from each others by repulsive forces of like electric charge on surface of

each solid particle

5. Solution in which ions that would normally not be soluble in water under

prevailing conditions are held in solution by so called chelating agents.

An important type of phase transfer is extraction, including liquid-

liquid and liquid-solid extraction. Transfer of substance from a

solution to a solid phase is called sorption. An important example is

sorption on activated carbon.

Physical precipitation – process in which a solid forms from a solute

in solution as result of physical changes in the solution (cooling the

solution, evaporation of solvents, alteration of solvent composition).

(Compare to chemical precipitation in which a chemical reaction in

solution produces an insoluble material).

Phase transfer or phase transition

Activated-carbon adsorption can be used to remove of wide variety of contaminants

from liquid and gaseous streams (most frequently used for organic compounds). The

process is relative nonspecific, and thus, is widely used as a broad spectrum

treatment operation when the chemical composition of a stream is not fully

understood.

Common treatment application include groundwater treatment, chemical-spill

response, industrial wastewater treatment, air-pollution control system.

Physical adsorption results from the action of van der Waals forces, relatively week

interactions produced by the motion of electrons in their orbitals.

Chemical adsorption or chemisorption , involves electronic interactions between

specific surface sites and solute molecules, resulting in the formation of a bond that

can have all of the characteristics of a „true chemical bond.“

Electrostatic adsorption based on the forces between ions and charged functional

groups and is synonymous with the term ion-exchange.

The adsorption process is reversible - possibility to remove the adsorbed

contaminants after the adsorption capacity of the carbon has been exhausted.

Both result from from electrostatic interaction.

Activated-carbon adsorption

Solvent extraction is referred to two different types of processes:

Liquid-liquid extraction is the separation of constituents from a liquid solution by

contact with another, immiscible liquid in which the constituents are more

soluble.

Liquid- solid extraction (leaching) is the separation of the constituents from

solids by contact with a liquid in which the constituents dissolve.

In hazardous wastes treatment the term „solvent extraction“ is usually

reserved to liquid-liquid extraction, especially extraction of organic compounds

from aqueous solution into immiscible solvents.

Solvent extraction is physical separation process, used for transfer of

constituents from one liquid solution (or solid matrix) to another. The

constituents are unchanged chemically.

Application - for separation of a valuable constituent from impurities present in

the original solution or concentration of a constituent for ease of subsequent

recovery or treatment.

Solvent extraction

Molecular separation is often based upon membrane processes in

which dissolved contaminants or solvent are forced through a

membrane. The most widely used membrane process is reverse

osmosis in which water from wastewater is forced through a

membrane that is selective to water yielding purified water product

and leaving behind a concentrated liquor containing impurities.

Other membrane processes include ultrafiltration and electrodialysis

in which ions in a solution subjected to electrolysis migrate selectively

through alternate membranes that allow for the passage of cations

and anions.

Molecular separation

Membrane separation processes play an increasing role in the reduction or

recycling of hazardous wastes. This processes separate the contaminant (solute)

from a liquid phase (solvent, typically water). Main functions: volume reduction,

recovery or purification of the liqiud phase, concentration or recovery of the

contaminant or solute.

Pressure driven processes:

Reverse osmosis - water separation from a feed stream containing inorganic ions .

The purity of recovered water is relatively high - water is suitable for recycling.

Nanofiltration separates ions or organic components from water by limiting the size

of membrane pores through which a contaminant can pass. Typically used for

removing contaminants with molecular weight 100-500 from water.

Ultrafiltration - separates organic compounds from water according to the size

(molecular weight) of the organic molecules. Membranes are manufactured with the

capability to remove contaminants with the molecular weigh between

100 - 1, 000,000.

Microfiltration - separates with a micrometre sized membrane (0.1 to 10 m)

Electric potential driven processes

Electrodialysis - removes ionic components from water. It produces moderate quality

product water (i.e. several hundred mg/L salts ).

Membrane separation

INLET

PERMEATE

CONCENTRATE

Fundementals of membrane separation

STORAGE

TANK

FILTER

1. STAGE

RO

SOLIDIFICATION/

EVAPORATION

1. PERMEATE

2. STAGE

RO

STORAGE

TANK

FILTER

HCl

2. P

ER

ME

AT

E

1. CONCENTRATE

2. CONCENTRATE

Reverse osmosis

treatment of landfill

leachate

http://www.eco-web.com/edi/090714.html

Pressure driven membrane separation processes

When semipermeable membrane separates two solutions of different

dissolved - solid concentration, pure water flows through the membrane into

the concentrated solution (resulting in osmotic pressure), while ions (i.g.

dissolved salts) are retained behind the membrane. This process is known

as osmosis.

During reverse osmosis, pressure is applied to the more concentration

solution to reverse the normal osmotic flow, and pure water is forced

through the semipermeable membrane into tle less concentrated solution.

The purified stream that passes through the membrane is called permeate,

the concentrated stream retained by the membrane is known as

concentrate.

Advantages of reverse osmosis:

- both the recovered solvent and the concentrates solute can be

recycled to a manufacturing process,

- the separation process does not require an energy-intensive

phase change such as is required for destillation or evaporation

- capital costs are also relatively low.

Membrane separation – reverse osmosis

Ultrafiltration (UF) and nanofiltration (NF) utilise pressure and a semipermeable

membrane to separate nonionic material from a solvent (such as water). These

membrane - separation techniques are particularly effective for the removal of

suspended solids, oil and grease, large organic molecules, and complexed

heavy metals from wastewater stream.

In UF and NF systems, the membrane retains material based solely on size,

shape and molecule flexibility. The membrane acts as a sieve to retain dissolved

and suspended materials that are physically too large to pass throug its pores.

The major difference between UF and NF is the molecular weight of separated

species. Both methods utilise identical operating principles.

Electrodialysis relies on ion-exchange membrane in a direct-curent electrical

field to separate inorganic ionic species from solution. Like reverse osmosis

membranes, electrodialysis membrane are sensitive to fouling that limit waste-

treatment application of this technology. The metal-finishing and electroplating

industry is the greatest potential market for these systems.

Membrane separation – ultrafiltration, nanofiltration,

electrodialysis

The applicability of chemical treatment to waste depends upon the chemical

properties such acid-base, oxidation-reduction, precipitation, reactivity,

flammability, corrosivity and compatibility with other wastes. An attractive

feature of chemical treatment is the opportunity to treat wastes with other

wastes, e.g. mutual neutralisation of waste acids with waste bases.

It consists especially of:

- acid/base neutralisation

- chemical precipitation

- chemical flocculation

- oxidation/reduction

- chemical extraction and leaching

- ion exchange

Methods of chemical treatment

Neutralisation is a process used to eliminate waste acids and bases as

shown by the following reaction:

H+ + OH- → H2O

Although simple in principle, neutralisation can present some problems in

practice, such as evolution of volatile contaminants or mobilisation of soluble

substances. The heat generation from the above reaction when the waste

envolved are relatively concentrated can result in dangerous hot solution

and even spattering. Strongly acidic or basic solutions are corrosive to

pipes, containers and mixing apparatus.

Lime (Ca(OH)2) is a widely used base for treating acidic wastes. Sulphuric

acid (H2SO4) is a relatively inexpensive acid for treating alkaline wastes.

However, addition of too much sulphuric acid can produce highly acidic

products. For some applications, acetic acid (CH3COOH), is preferable. It is

a weak acid and also naturalproduct and biodegradable.

Neutralistion, or pH adjustment, is often required prior to the application

of other waste treatment processes (biochemical treatment –

microorganisms usually require a pH range of 6 to 9.

Acid/base neutralisation

Oxidation and reduction can be used for the treatment and removal of a variety of

inorganic and organic wastes. The net result of these reactions is the conversion of the

waste to a nonhazardous form or to a form that can be isolated physically.

Ozon, O3, is a strong oxidant that can be generated on-site by an electrical discharge

through dry air or oxygen:

3O2 → 2O3

electrical discharge

Oxidation of organics

(CH2O) + (O) → CO2 + H2O

organic matter

Oxidation of inorganics

Cyanide: 2CN- + 5 OCl- + H2O → N2 + 2HCO3- + 5Cl-

Iron (II): 4 Fe2+ + O2 + 10 H2O → 4 Fe(OH)3 + 8H+

Reduction of inorganics

Chromate 2CrO42- + 3 SO2 + 4H+ → Cr2(SO4)3 + 2H2O

Permanganate MnO4- + 3Fe2+ + 7 H2O → MnO2(s) + 3 Fe(OH)3 (s) + 5 H+

Oxidation/reduction

Precipitation is used in hazardous waste treatment primarily for the removal of

heavy metal ions from water as shown for the chemical precipitatiopn of

cadmium:

Cd2+ (aq) + HS- → CdS (s) + H+ (aq)The most widely used means of precipitation metal ions is by the

formation of hydroxides such as chromium (III) hydroxide:

Cr3+ + 3 OH- → Cr(OH)3

The source of hydroxide ions, OH-, is a base (alkali), such as lime (Ca(OH)2,

sodium hydroxide (NaOH), or sodium carbonate (Na2CO3).

Sulfide precipitation is very effective means of treatment, because the

solubility of some heavy metal sulfides is extremely low. Sources of sulfide

ions include sodium sulfide, Na2S, sodium hydrosulfide (NaHS), hydrogen

sulfide (H2S), and iron (II) sulfide.

Some metals can be precipitated from solution in the elemental metal form by

the action of a reducing agent (e.g. sodium borohydride, NaBH4).

Metal ions can be converted to the elemental form and removed from solution

by reaction with more active metal by a process called cementation – the

reduction of toxic cadmium with relatively harmless zinc:

Cd2+ + Zn → Cd + Zn2+

Chemical precipitation

Electrolysis consists of the electrochemical reduction and oxidation of

chemical species in solution by means of electricity applied to electrode from

an external source. One species in solution (usually a metal ion) is reduced

by electrons at the cathode and another gives up electrons to the anode and

is oxidised there.

Cathode (-) Anode (+)

Cu2+ + 2e- → Cu H2O → ½ O2 + 2e- + 2H+

In hazardous waste application electrolysis is most widely used in recovery

of metals, mostly from electroplating media, from wastewater and rinsewater

from the electronics industries and from metal finishing operations.

The metals that are most commonly recovered by electrolysis are cadmium,

copper, gold, lead, silver and zinc.

Recovered metals are usually recycled to the process that produces the

waste.

Electrolysis

Chemical extraction or leaching in hazardous waste treatment is the removal

of a hazardous constituents by reaction with extractants in solution.

Acidic solutions dissolve poorly soluble heavy metal salts by reaction of the

salt anions with H+.

PbCO3 + H+ → Pb2+ + HCO3-

Ion exchange

Ion exchange is a means of removing cations or anions from solution onto a

solid resin. Ions taken up by an ion exchange resin may be removed by

treating the resin with concentrated solutions of acid, base or salt (NaCl).

The net result is to concentrate the ions originally removed from dilute

solution in water into a much more concentrated solution.

The greatest use of ion exchange in hazardous waste treatment is for

removal of low level of heavy metal ions from wastewater. Ion exchange is

employed in the metal plating industry to purify rinsewater and spent plating

bath solution.

Chemical extraction and leaching

Influence of pH and other chemical variables on leaching.

pH value – major chemical variable controling the leaching of minor and major

elements from waste or residue.

pH value influenced the solubility of important minerals (oxides, hydroxides,

carbonates).

Cationic and anionic constituents are bound to these solid residues by

adsorption/desorption on mineral surface with a pH-dependent charge.

Leaching of cationic constituents increases towards low pH, anionic constituents

towards high pH.

Calcium – typical cation leaching behaviour (concentration increase towards low pH).

Molybdenum is present as the oxyanion molybdate (MoO42-) – leaching

concentration increasing towards high pH.

Amphoteric behaviour of e.g. Pb and Zn that can be present both in cationic and

anionic form, show substantial and increasing leachability both at low (cationic form)

and high (anionic form) pH value.

The general leaching behaviour can be further modified by the effect of other

chemical parameters (redox potential, complexation of inorganic components).

Leaching properties of waste or residue

Photolytic reactions or the process of photolysis are those in which

protons or electromagnetic radiation consisting of shortlwavelenght

visible light or ultraviolet radiation are absorbed by a molecule,

causing a chemical reaction to occur.

Photolysis can be used to destroy a number of kinds of hazardous

wastes. In such applications it is most useful in breaking chemical

bonds in refractory organic compounds.

Photolysis can be used to destroy several kinds of hazardous waste

substance, such as dioxins, herbicides (atrazin), 2,4,6-trinitrotoluene

(TNT) and polychlorinated biphenyls (PCB).

The addition of chemical oxidant such as potassium peroxodisulfate

K2S2O8, enhances destruction of oxidising active photolytic products.

Photolytic reactions

Chemical treatment of hazardous waste:

neutralization, precipitation, oxidation-reduction

J.Pichtel: Waste Management Practices, ISBN:978-1-4665-8519-5

Explosive: substances and preparations which may explode under the effect of flame or

which are more sensitive to shocks or friction than dinitrobenzene.

Oxidizing: substances and preparations which exhibit highly exothermic reactions when in

contact with other substances, particularly flammable substances.

Flammable: liquid substances and preparations having a flash point equal to or greater than

21°C and less than or equal to 55°C.

Highly flammable: liquid substances and preparations having a flash point below 21°C

(including extremely flammable liquids), or substances and preparations which may become

hot and finally catch fire in contact with air at ambient temperature without any application of

energy, or solid substances and preparations which may readily catch fire after brief contact

with a source of ignition and which continue to burn or to be consumed after removal of the

source of ignition, or gaseous substances and preparations which are flammable in air at

normal pressure, or -substances and preparations which, in contact with water or damp air,

evolve highly flammable gases in dangerous quantities.

Irritable: non-corrosive substances and preparations which, through immediate, prolonged or

repeated contact with the skin or mucous membrane, can cause inflammation.

Harmful: substances and preparations which, if they are inhaled or ingested or if they

penetrate the skin, may involve limited health risks.

(Appendix) PROPERTIES OF WASTES WHICH RENDER THEM HAZARDOUS

Toxic: substances and preparations (including very toxic substances and preparations)

which, if they are inhaled or ingested or if they penetrate the skin, may involve serious, acute

or chronic health risks and even death.

Carcinogenic: substances and preparations which, if they are inhaled or ingested or if they

penetrate the skin, may induce cancer or increase its incidence.

Corrosive: substances and preparations which may destroy living tissue on contacts.

Infectious: substances containing viable micro-organisms or their toxins which are known or

reliably believed to cause disease in man or other living organisms.

Teratogenic: substances and preparations which, if they are inhaled or ingested or if they

penetrate the skin, may induce non-hereditary congenital malformations or increase their

incidence.

Mutagenic: substances and preparations which, if they are inhaled or ingested or if they

penetrate the skin, may induce hereditary genetic defects or increase their incidence.

Substances and preparations which release toxic or very toxic gases in contact with water,

air or an acid.

Substances and preparations capable by any means, after disposal, of yielding another

substance, e.g. a leachate, which possesses any of the characteristics listed above.

Ecotoxic: substances and preparations which present or may present immediate or delayed

risks for one or more sectors of the environment

Questions related to the presentation

- Which type of waste is mainly processed by physico – chemical

techniques?

- Principal physical processes for waste treatment.

- Principles of membrane separation.

- Principal chemical processes for waste treatment.

- Interrelationship between physical and chemical processing of waste.