coroner污水处理工业废水回用中英文对照外文翻译文献

2021年1月22日发(作者：potential是什么意思)












(
文档含英文原文和中文翻译
)


中英文资料对照外文翻译




Catalytic strategies for industrial water re-use

Abstract
The
use
of
catalytic
processes
in
pollution
abatement
and
resource
recovery
is
widespread and of significant economic importance [R.J. Farrauto, C.H. Bartholomew,
Fundamentals
of
Industrial
Catalytic
Processes,
Blackie
Academic
and
Professional,1997.].
For
water
recovery
and
re-use
chemo-catalysis
is
only
just
starting
to
make
an
impact
although
bio-catalysis
is
well
established
[J.N.
Horan,
BiologicalWastewater Treatment Systems; Theory and Operation, Chichester, Wiley,

1990.].
This
paper
will
discuss
some
of
the
principles
behind
developing
chemo-catalytic
processes
for
water
re-use.
Within
this
context
oxidative
catalytic
chemistry
has
many
opportunities
to
underpin
the
development
of
successful
processes
and
many
emerging
technologies
based
on
this
chemistry
can
be
considered .
Keywords:
COD removal; Catalytic oxidation; Industrial water treatment
uction




Industrial water re-use in Europe has not yet started on the large scale. However,
with potential long term changes in European weather and the need for more water
abstraction
from
boreholes
and
rivers,
the
availability
of
water
at
low
prices
will
become
increasingly
rare.
As
water
prices
rise
there
will
come
a
point
when
technologies
that
exist
now
(or
are
being
developed)
will
make
water
recycle
and
re-use a viable commercial operation. As that future approaches, it is worth stating the
most
important
fact
about
wastewater
improvement
–

avoid
it
completely
if
at
all
possible!
It
is
best
to
consider
water
not
as
a
naturally
available
cheap
solvent
but
rather,
difficult
to
purify,
easily
contaminated
material
that
if
allowed
into
the
environment will permeate all parts of the biosphere. A pollutant is just a material in
the
wrong
place
and
therefore
design
your
process
to
keep
the
material
where
it
should
be
–

contained
and
safe.
Avoidance
and
then
minimisation
are
the
two
first
steps in looking at any pollutant removal problem. Of course avoidance may not be an
option on an existing plant where any changes may have large consequences for plant
items
if
major
flowsheet
revision
were
required.
Also
avoidance
may
mean
simply
transferring the issue from the aqueous phase to the gas phase. There are advantages
and
disadvantages
to
both
water
and
gas
pollutant
abatement.
However,
it
must
be
remembered
that
gas
phase
organic
pollutant
removal
(VOC
combustion
etc.,)
is
much
more
advanced
than
the
equivalent
water
COD
removal
and
therefore
worth
consideration
[1].
Because
these
aspects
cannot
be
over- emphasised
，
a
third
step
would be to visit the first two steps again. Clean-up is expensive, recycle and re-use
even
if
you
have
a
cost
effective
process
is
still
more
capital
equipment
that
will
lower your return on assets and make the process less financially attractive. At present
the best technology for water recycle is membrane based. This is the only technology
that will produce a sufficiently clean permeate for chemical process use. However, the
technology cannot be used in isolation and in many (all) cases will require filtration
upstream
and
a
technique
for
handling
the
downstream
retentate
containing
the
pollutants.
Thus,
hybrid
technologies
are
required
that
together
can
handle
the
all
aspects of the water improvement process[6,7,8].
Hence the general rules for wastewater improvement are:

1. Avoid if possible, consider all possible ways to minimise.


2. Keep contaminated streams separate.

3. Treat each stream at source for maximum concentration and minimum flow.

4. Measure and identify contaminants over complete process cycle. Look for peaks,
which will prove costly to manage and attempt to run the process as close to typical
values
as
possible.
This
paper
will
consider
the
industries
that
are
affected
by
wastewater issues
and the technologies that are available to
dispose of the retentate
which
will
contain
the
pollutants
from
the
wastewater
effluent.
The
paper
will
describe some of the problems to be overcome and how the technologies solve these
problems to varying degrees. It will also discuss how the cost driver should influence
developers of future technologies.

2. The industries





The process industries that have a significant wastewater effluent are shown in
Fig.
1.
These
process
industries
can
be
involved
in
wastewater
treatment
in
many
areas and some illustrations of this are outlined below.

Fig. 1. Process industries with wastewater issues.

2.1. Refineries





The process of bringing oil to the refinery will often produce contaminated water.
Oil pipelines from offshore rigs are cleaned with water; oil ships ballast with water
and the result can be significant water improvement issues.

2.2. Chemicals





The synthesis of intermediate and speciality chemicals often involve the use of a
water wash step to remove impurities or wash out residual flammable solvents before
drying.

2.3. Petrochemicals





Ethylene
plants
need
to
remove
acid
gases
(CO2,
H2S)
formed
in
the
manufacture
process.
This
situation
can
be
exacerbated
by
the
need
to
add
sulphur
compounds
before
the
pyrolysis
stage
to
improve
the
process
selectivity.
Caustic
scrubbing is the usual method and this produces a significant water effluent disposal
problem.

2.4. Pharmaceuticals and agrochemicals





These industries can have water wash steps in synthesis but in addition they are
often formulated with water-based surfactants or wetting agents.

2.5. Foods and beverages





Clearly use water in processing and COD and BOD issues will be the end result.

2.6. Pulp and paper





This
industry
uses
very
large
quantities
of
water
for
processing
–

aqueous
peroxide and enzymes for bleaching in addition to the standard Kraft type processing
of
the
pulp.
It
is
important
to
realise
how
much
human
society
contributes
to

contaminated water and an investigation of the flow rates through municipal treatment
plants soon shows the significance of non-process industry derived wastewater.

3. The technologies





The technologies for recalcitrant
COD and toxic pollutants in
aqueous effluent
are
shown
in
Fig.
2.
These
examples
of
technologies
[2,6,8]
available
or
in
development
can
be
categorised
according
to
the
general
principle
underlying
the
mechanism of action. If in addition the adsorption (absorption) processes are ignored
for this catalysis discussion then the categories are:

1. Biocatalysis

2. Air/oxygen based catalytic (or non- catalytic).

3. Chemical oxidation

1. Without catalysis using chemical oxidants

2.
With
catalysis
using
either
the
generation
of
_OH
or
active
oxygen
transfer.
Biocatalysis is an excellent technology for Municipal wastewater treatment providing
a
very
cost-effective
route
for
the
removal
of
organics
from
water.
It
is
capable
of
much
development
via
the
use
of
different
types
of
bacteria
to
increase
the
overall
flexibility
of
the
technology.
One
issue
remains
–

what
to
do
with
all
the
activated
sludge even after mass reduction by de-watering. The quantities involved mean that
this is not an easy problem to solve and re- use as a fertilizer can only use so much.
The
sludge
can
be
toxic
via
absorption
of
heavy
metals,
recalcitrant
toxic
COD.
In
this
case
incineration
and
safe
disposal
of
the
ash
to
acceptable
landfill
may
be
required. Air based oxidation [6,7] is very attractive because providing purer grades of
oxygen are not required if the oxidant is free. Unfortunately, it is only slightly soluble
in water, rather unreactive at low temperatures and, therefore, needs heat and pressure
to
deliver
reasonable
rates
of
reaction.
These
plants
become
capital
intensive
as
pressures
(from
_10
to
100
bar)
are
used.
Therefore,
although
the
running
costs
maybe low the initial capital outlay on the plant has a very significant effect on the
costs
of
the
process.
Catalysis
improves
the
rates
of
reaction
and
hence
lowers
the
temperature
and
pressure
but
is
not
able
to
avoid
them
and
hence
does
not
offer
a
complete solution. The catalysts used are generally Group VIII metals such as cobalt
or
copper.
The
leaching
of
these
metals
into
the
aqueous
phase
is
a
difficulty
that
inhibits the general use of heterogeneous catalysts [7]. Chemical oxidation with cheap
oxidants has been well practised on integrated chemical plants. The usual example is
waste
sodium
hypochlorite
generated
in
chlor-alkali
units
that
can
be
utilised
to
oxidise
COD
streams
from
other
plants
within
the
complex.
Hydrogen
peroxide,
chlorine
dioxide,
potassium
permanganate
are
all
possible
oxidants
in
this
type
of
process. The choice is primarily determined by which is the cheapest at the point of
use.
A
secondary
consideration
is
how
effective
is
the
oxidant.
Possibly
the
most

researched
catalytic
area is
the generation and use of _OH as
a very
active oxidant
(advanced oxidation processes) [8]. There are a variety of ways of doing this but the
most usual is with photons and a photocatalyst. The photocatalyst is normally TiO2
but other materials with a suitable band gap can be used [9,10]. The processes can be
very
active
however
the
engineering
difficulties
of
getting
light,
a
catalyst
and
the
effluent efficiently contacted is not easy. In fact the poor efficiency of light usage by
the catalyst (either through contacting problems or inherent to the catalyst) make this
process
only
suitable
for
light
from
solar
sources.
Photons
derived
from
electrical
power
that
comes
from
fossil
fuels
are
not
acceptable
because
the
carbon
dioxide
emission
this
implies
far
outweighs
and
COD
abatement.
Hydroelectric
power
(and
nuclear power) are possible sources but
the basic inefficiency is
not
being avoided.
Hydrogen
peroxide
and
ozone
have
been
used
with
photocatalysis
but
they
can
be
used separately or together with catalysts to effect COD oxidation. For ozone there is
the problem of the manufacturing route, corona discharge, which is a capital intensive
process often limits its application and better route to ozone would be very useful. It is
important
to
note
at
this
point
that
the
oxidants
discussed
do
not
have
sufficient
inherent
reactivity
to
be
use
without
promotion.
Thus,
catalysis
is
central
to
their
effective
use
against
both
simple
organics
(often
solvents)
or
complex
recalcitrant
COD. Hence, the use of Fenton’s catalyst (Fe) for hydrogen peroxide [11]. In terms of
catalysis these oxidants together with hypochlorite form a set of materials that can act
has ‘active oxygen transfer (AOT) oxidants’ in the presence
of a suitable catalyst. If
the AOT oxidant is hypochlorite or hydrogen peroxide then three phase reactions are
avoided
which
greatly
simplifies
the
flowsheet.
Cheap,
catalytically
promoted
oxidants
with
environmentally
acceptable
products
of
oxidation
that
do
not
require
complex chemical engineering and can be produced efficiently would appear to offer
one of the best solutions to the general difficulties often observed.
3.1. Redox catalysis and active oxygen transfer




The mechanism of catalytically promoted oxidation with hydrogen peroxide or
sodium hypochlorite cannot be encompassed within one concept, however there are
general
similarities
between
the
two
oxidants
that
allows
one
to
write
a
series
of
reactions for both
(Fig. 3) [5]. This type of mechanism could be used to describe a
broad
range
of
reactions
for
either
oxidant
from
catalytic
epoxidation
to
COD
oxidation. The inherent usefulness of the reactions is that;
1. The reactions take place in a two-phase system.
2. High pressure and temperature are not required.
3. The catalytic surface can act as an adsorbent of the COD to be oxidised effectively
increasing the concentration and hence the rate of oxidation.

The
simple
mechanism
shows
the
selectivity
issue
with
this
type
of
processes.
The
oxidant can simply be decomposed by the catalyst to oxygen gas
–
this reaction must
be avoided because dioxygen will play no role in COD removal. Its formation is an
expensive
waste
of
reagent
with
oxygen
gas
($$20/Te)
compared
to
the
oxidant
($$400
–
600/Te).
To
be
cost
competitive
with
alternative
processes
redox
catalysis
needs excellent selectivity.
3.2. Technology mapping




The technologies so far described can be mapped [12] for their applicability with
effluent COD concentration (measured as TOC) and effluent flow rate (m3 h-1). The
map
is
shown
in
Fig.
4.
The
map
outlines
the
areas
where
technologies
are
most
effective. The boundaries, although drawn, are in fact fuzzier and should be only used
as
a
guide.
Only
well
into
each
shape
will
a
technology
start
to
dominate.
The
underlying cost model behind the map is based on simple assertions
–
at high COD
mass flows only air/oxygen will be able to keep costs down because of the relatively
low
variable
cost
of
the
oxidant.
At
high
COD
concentrations
and
high
flows
only
biological
treatment
plants
have
proved
themselves
viable
–

of
course
if
done
at
source recovery becomes
an option. At low flows and low COD levels redox AOT
catalysis is an important technology
–
the Synetix Accent 1 process being an example
of this type of process (see Fig. 5 for a simplified flowsheet). The catalyst operates
under very controlled conditions at pH > 9 and hence metal leaching can be avoided
(<5 ppb). The activity and selectivity aspects of the catalyst displayed in Fig. 3 can be
further elaborated to look at the potential surface species. This simple view has been
extended by a significant amount of research [3,4,5]. Now the mechanism of such a
catalyst
can
be
described
in
Fig.
6.
The
key
step
is
to
avoid
recombination
of
NiO
holes to
give peroxy species and this can be contrasted with the hydrogen peroxide
situation
where
the
step
may
be
characterized
as
oxygen
vacancy
filled.
From
both
recombination
will
be
facilitated
by
electronic
and
spatial
factors.
The
range
of
application of the process is outlined below. From laboratory data some general types
of
chemical
have
been
found
suitable
–

sulphides,
amines,
alcohols,
ketones,
aldehydes,
phenols,
carboxylic
acids,
olefins
and
aromatic
hydrocarbons.
From
industrial
trials
recalcitrant
COD
(nonbiodegradable)
and
sulphur
compounds
have
been
successfully
demonstrated
and
a
plant
oxidising
sulphur
species
has
been
installed and is operational.
4. Conclusions





Wastewater treatment processes are in the early stages of development. The key
parameters
at
present
are
effectiveness
and
long
term
reliability.
Many
processes
operating are in this stage, including the redox

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