Environmental Technology ChimH409 (2-0-1)

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Environmental Technology ChimH409 (2-0-1)
Welcome _at_ Bruface
Universite Libre de Bruxelles
Dept Water Pollution Control
Michel Verbanck mikeverb_at_ulb.ac.be 2012
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European Waste Catalogue and Hazardous Waste List
(since 2002)
classes all wastes into 20 chapters. Examples
Common Industrial Waste Processes Chromate,
Phenol and Cyanide
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• machine-tool coolants and cutting oils

• spent pickling acids

• cyanide CN-

Absolutely avoid generate HCN locally !
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Centralized detoxication plant for reception
handling of hazardous wastes

• spent acids (including chromic acid)
• spent alkaline cleaning solutions
• cyanide CN-
• solvents such as phenols

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Chromate removal
Cr 6 which is much more toxic than Cr 3 ,
needs absolutely to be controlled. Chromium is
found in wastes from metal plating and finishing
operations. It is present in rinse waters from
chromic acid baths and in spent baths from
electroplating and anodizing processes.
The detoxication treatment is by reduction and
precipitation, in a process whereby a soluble
metallic ion is reduced through an
oxidation-reduction reaction and then
precipitated by conversion to an insoluble
metallic hydroxide. The reaction using ferrous
sulfate is
Na2Cr2O7 6 FeSO4 7H2SO4 ? Cr2(SO4)3
3Fe2(SO4)3 7H2O Na2SO4 pH lt 3 Followed by
precipitation at pH close to 9 (see following
chevron curves characteristic of metal
hydroxides solubility) Cr2(SO4)3 3Ca(OH)2 ?
2Cr(OH)3? 3CaSO4
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detoxication of CN- (conversion into cyanates
which are less toxic) through electrolytic
oxidation
Alternatively O3 can be used as the oxidising
agent
CN- O3 ? CNO- O2
Afterwards, total destruction of the hazardous
waste is preferable
2 NaCNO (cyanate) 4 NaOH 3Cl2 ? 2CO2 6NaCl
N2 2H2O
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New development Enhanced oxidation of
cyanide by the combined action of hydrogen
peroxide and UV irradiation
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removal of phenols
for low concentrations
C6H5OH 14O3 ? 6CO2 3H2O 14O2
for highest concentrations recovery in a solvent
(typically benzene) followed by phase separation
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Environmental fate and behaviour of LNAPL (Light
Non-Aqueous Phase Liquid) and DNAPL (Dense),
respectively.
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Permeable Reactive Barriers
A Permeable Reactive Barrier (PRB) is an
engineered emplacement of reactive materials that
is placed in the subsurface, designed to
intercept a contaminant plume. It provides an
obligated flow path through the reactive media,
and transforms the contaminant(s) into
environmentally acceptable forms to attain
remediation concentration goals downgradient of
the barrier.
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Cement rotary kilns are convenient tools to
ensure that the triple T rule (Temperature Time
- Turbulence) is appropriately respected for
the destruction of specific organics. These
ancillary waste destruction units were, for
instance, used at the time of the Belgium
dioxinated chicken crisis in 1999.
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Management of fine-grained contaminated sediments
deposited in harbours
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