Chapter 6.2 Physico-chemical treatment
Notes on this chapter
The material presented here gives an overview of the main technologies presently used in
the field of physico-chemical treatment. The special item of stabilisation and
solidification is addressed separately in Chapter 6.4.
The techniques addressed in this chapter should be considered in relation to general
aspects of legislation and standardisation, which differ considerably between countries
and groups of countries (such as the European Union). Most treatment processes are
landfill pre-treatment. Among the most important influences on treatment choices are the
types and permit conditions of available landfills, whether they are simple landfills
(sanitary or secure) or co-disposal sites, and whether they accept storage of stabilised
wastes. The selection, and sophistication, of a chosen treatment will depend on these
landfill requirements and on their operating parameters and standards.
The slides cover the main aspects of the different technologies, but they can be extended
with additional technical aspects according to the state of art in the countries (or groups)
on the training course. The slides can only address broad issues relating to the treatment
techniques. Trainers should add or adapt details of equipment, construction and
management aspects to meet local circumstances.
Valuable sources of additional information include technical documents from
conferences, technical reviews and magazines, particularly those published by the
national environmental protection agencies, national standards institutes and international
associations such as the International Solid Waste Association (ISWA), FEAD and
EURITS.
List of slides
Title slide
Slide 2 Physico-chemical treatment
Slide 3 Physico-chemical treatment facilities
Slide 4 Physico-chemical treatment in central treatment facility
Slide 5 Treatment residues
Slide 6 Physical processes
Slide 7 Separation
Slide 8 Adsorption
Slide 9 Sedimentation
Slide 10 Sedimentation - example
Slide 11 Flotation
Slide 12 Drying and evaporation
Slide 13 Drying and evaporation - example
Slide 14 Chemical processes
Slide 15 Reduction and oxidation
TRP Chapter 6.2
1
Slide 16 Oxidation in practice
Slide 17 Reduction in practice
Slide 18 Neutralisation
Slide 19 Precipitation
Slide 20 Other chemical processes
Slide 21 Combined physical and chemical processes
Slide 22 Physico-chemical treatment
Slide 23 Key considerations
Slide 24 Summary
Background notes
1 Physical and chemical methods for the treatment of wastes involve a range of different
but commonly-used treatment processes, often used in combination, to separate or
transform hazardous substances. By definition they do not include biological processes.
2 The many advantages of physico-chemical treatment processes include the fact that
little energy is required.
3 Typically, physical treatment processes are long-established and relatively low-tech.
Chemical treatment methods are also well-established. As a result these two treatment
methods may require relatively lower capital investment levels than some other methods
such as thermal processing. They do however still require a high level of expertise to
ensure their safe operation.
4 Physico-chemical treatment of wastes can be used to deal with both solid and liquid
wastes, as well as organic and inorganic wastes, providing the appropriate processes are
used. However, both physical and chemical processes are specific for each waste,
requiring an in-depth knowledge of the waste to be treated and an understanding of a
variety of applications.
5 Chemical reactions must be closely monitored and checked by a qualified laboratory.
The presence of substances which inhibit the catalyst, where used, can affect the success
of the process.
6 The facility design and equipment selection for physical-chemical treatment of waste
are determined by the properties and characteristics of the wastes which will be treated.
They are also influenced by the national and regional regulations and standards which are
in force.
Sources of further information
Batstone, R; Smith, JE & Wilson, DC editors (1989) The safe disposal of hazardous
wastes: The special needs and problems of developing countries World Bank,
Washington, Technical paper No 93 Vol 2 in 3 volumes ISBN 0-8213-1144-1 (available
as pdf files from www.worldbank.org/publications/)
TRP Chapter 6.2
2
Guyer, Howard H (1998) Industrial processes and waste stream management Wiley
ISBN 0-4712-9984-7
ISWA (2002) Safe hazardous waste management systems: a state of the art guide for
decision makers – forthcoming from www.iswa.org
LaGrega, MD; Buckingham, PL; Evans, JC & ERM Group (1994) Hazardous Waste
Management McGraw Hill, New York ISBN 0-07-019552-8
Lohwongwatana, B; Soponkanaporn, T & Sophonsridsuk, A Industrial hazardous waste
treatment facilities in Thailand Waste Management & Research Vol 8 No 2
Nash, JM; Cheung, B; Fung, CH; Lei PK, Mak, PW; Rootham, RC; Stokoe, MJ & Tong,
R (1991) Control and treatment of hazardous (chemical) waste in Hong Kong Waste
Management & Research Vol 9 No 3
Ravishankar, R (1990) Opportunities and constraints for cement kiln incineration in
Malaysia, Waste Management & Research Vol 8 No 2
Razzell, WE (1990) Chemical fixation, solidification of hazardous waste, Waste
Management & Research, Vol 8 No 2
Technical guidelines from the Secretariat of the Basel Convention www.basel.int
UNEP (1991) Hazardous waste policies and strategies – a training manual, Technical
report No 10 UNEP Industry & Environment Programme Activity Centre &
Environmental Education & Training Unit, Paris ISBN 92-807-1311-6
Web sites
The Basel Convention www.basel.int
International Solid Waste Association www.ISWA.org
United Nations Environment Programme, Division of Technology, Industry and
Economics www.uneptie.org
TRP Chapter 6.2
3