PowerPointPrsentation

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M. Kolb, Fachhochschule Aalen
Treatment of Industrial Wastewater
1. Chemical Industry
1.1 Biological treatment
Because of the enormous adaptation ability of
bacteria biocenosis waste- water of the chemical
industry can often be biologically treated
(aerobically). The following points must however
be considered
In few cases the wastewater is treated
anaerobically.
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Schematic diagramm of the BASF Ludwigshafen
wastewater-treatment plant
Daily influx 700.000 m3 BOD5 load
375.000 kg/day BOD5 removal 97 COD removal
89 Nitrate removal 98
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Special Bioreactors used in chemical industry
Advantages   O2-Exploitation better21 (air) ?
5 (off-gas)  normal activated sludge process
21 ? 16 Lesser requirement of area Closed
reactors ? no emission of aerosols and odour
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The Hoechst tall bioreactor (Biohochreaktor)
process
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Hoechst tall bioreactor (Biohochreaktor)
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1.2 Extraction   Examples Phenol can be
extracted from wastewater with butyl acetate,
cumene or diisopropylether. The remaining
concentration is between 20 and 500 mg/l which is
not toxic for the bacteria in the activated
sludge tank. Phenol and the extraction solvent
are separated in a following distillation
process. The extraction solvent is reused in the
process. Acetic acid can be extracted with ethyl
acetate, again the extraction solvent is recycled
for the process and acetic acid is a valuable
substance
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1.3 Adsorption   (very important also for the
purification of drinking water and waste
gas) Adsorption processes are used for waste
water generally, but mostly for individual
wastewater streams.   Adsorbents Activated
carbon Lignite coke Aluminium oxide Adsorber
resins
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Regeneration Activated carbon can be thermally
reactivated, i. e. the adsorbed substances are
combusted Lignite coke is burned Aluminium
oxide is thermally regenerated Adsorber resins
can be regenerated with methanol or
acetone Applications Aniline is adsorbed from
alkaline solutions, desorption by acid
solutions Phenol is adsorbed from acidic
solutions, desorption by alkaline
solutions Landfill leachets (Deponie-Sickerwasser
) can be treated biologically followed by
ultrafiltration and activated carbon adsorption
(for non-biodegradable substances)
Special Application Addition of activated carbon
into the activated sludge basin ? growth
surface for microorganisms causes higher biomass
concentration.
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• 1.4 Wastewater incineration (Abwasserverbrennung
  )
• Combustion of organic substances, water matrix is
  simultaneously vaporized
• Suitable if
• substances present are poorly biodegradable or
  biologically toxic
• high organic load ? heat of combustion is
  sufficient for vaporation of water
• the wastewater contains a multicomponent mixture
  in which concentrations vary in a large amount
• salts shall be recycled

• Applications
• icincineration of wastewater from terephthalic
  production
• incineration of wastewater which contains
  lignosulfonic acids
• emulsified organic matter

Problems - metal corrosion by
acids -  incrustination by salts -  flue gas
treatment   Combination with combustion of waste
gases and solids is possible
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Wastewater incineration
Clariant AG, Gersthofen plant reasonable from ca.
50.000 mg/l COD, therephthalic acid
(the combustion energy of the organic compounds
meets the evaporation energy of the water)
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1.5 Wet Oxidation (Nassoxidation) Oxidation with
O2 at higher temperature and higher pressure,
water not vaporized Often followed by biological
treatment
Characteristics -    for not degradeable or
slowly degradeable or toxic substances -     for
partial streams -     for high concentrations of
contaminants -     some tolerance for salts and
acids -     corrosion problems (Ti, PTFE)
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Low pressure wet oxidation T lt 200 C, p 5 20
bar At COD gt 6.000 mg/l heat recovery from
enthalpy of oxidation is comparable to the total
energy requirement of the process   SO32-/HSO3-,
phenol, amino- and hydroxyl substituted phenols,
waste water from dye manufacturing   AOX
decreases, COD decreases, BOD5 increases   High
pressure wet oxidation T gt 200 C, p gt 20 bar At
COD gt 50.000 mg/l heat recovery from enthalpy of
oxidation is comparable to the total energy
requirement of the process  
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wet oxidation plant T 300 C, p 120 bar
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1.6 Oxidation with H2O2, H2O2/UV, O3 Often
followed by biological treatment   H2O2 hardening
plants, tanneries Selfdecomposition, catalyzed
by heavy metal ions is unfavourable   H2O2/Fe2
(Fentons reagent) H2O2 ? HO HO- Fe2 HO- ?
Fe3 HO HO H e- ? H2O

from oxidized
substances   Best
results at pH 3 Neutralization leeds to sludge
formation
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O3, O3/UV two mechanisms   so called direct
oxidation under acidic conditions, slow process
can be accelerated by UV-rays O3 h? ? O
O2 O H2O ? H2O2 H2O2 h? ? 2 HO   alkaline
oxidation takes place also via the intermediate
formation of hydroxyl radicals O3 HO- ? HO2-
O2 HO2- O3 ? O2- O2 HO H2O O3 O2- ?
HO- 2 O2 HO   Organic halogen compounds are
dehalogenated, but formation of new organic
halogen compounds from inorganic halides is
possible
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2. Breweries, tanneries, papermills, creameries,
food- production Wastewater can be treated
biologically (aerob) but BOD5 N P-ratio has
to be checked.     Danger Wastewater can cause
the formation of bulking sludge (Blähschlamm).
The extent of activated sludge flocs is
diminished relative to filament-like organisms  
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Microscopic pictures of activated sludge
many filament-like bacteria bulking sludge, slow
sedimentation (115x)
strong bacteria flocs (90x)
Sphaerotilus natans, filament-like Bacteria
(1150x)
Vorticella spec. (230 x)
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3. Anaerobic treatment of wastewater Sugar
industry, starch industry, yeast manufacture,
alcohol destillation BOD5-concentration gt 2000
mg/l Compare anaerobic treatment of sludge in
municipal wastewater treatment Subsequent
aerobically biological purification is necessary
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Anaerobic degradation of organic substances to
biogas
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• Advantages
• No energy for supplying the process with air
• Energy rich biogas is formed
• Less production of sludge (ca. 10 compared with
  aerobic degradation)
•   
• Disadvantage
• Residence time longer (gt 2 days) ? not for
  treatment of municipal wastewater

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Two-stage anaerobic fluidized-bed reactor for
treating wastewater from bakers yeast
manufacture by Gist Brocades, Delft, Holland
Carbon balances in the (A) aerobic and (B)
anaerobic microbial degradation of organic
compounds
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pilot plant for anaerobic treatment of textile
waste water (right) and aerobic treatment of
municipal textile waste water
(left)Aalen-Unterkochen
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4. Electroplating industry   Many electroplating
facilities   After electroplating the workpiece
has to be cleaned from the adhesive solution by
this washing process wastewater
occurs   wastewater contains toxic components
cyanide (CN-), chromate (CrO42-), Metal-ions and
slowly biodegradeable organic components
(EDTA)   Special treatment of wastewater is
necessary separated facilities for treatment of
chromate, cyanide and acidic bathes
former wastewater from flow-basin was led
directly into the detoxification plants, today it
is led into ion-exchange facilities and reused in
the flow-basins
After regeneration of the ion-exchanger (HCl,
NaOH) the concentrated solutions are detoxified
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Cyanide CN- OCl- H2O ? Cl-CN 2OH-
(pH 10 12)
toxic   Cl-CN 2OH- ? OCN- Cl-
H2O   Disadvantage chlorinated compounds are
formed (AOX) with organic additives of the
bathes   Therefore oxidation with H2O2/UV, O3,
H2SO5, H2O2/H2SO5   Chromate   Cr2O72- 3
HSO3- 8H ? 2Cr3 3HSO4- 4 H2O (pH 2,5)
Metal ions   Me2 2OH- ? Me(OH)2 ? Me3
3OH- ? Me(OH)3 ?   Precipitation
with polymers containing SH-groups or Na2S also
possible
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Sludge   Filter press, hazardous waste
site     Newer developments   Recycling of metal
ions electrolytic deposition after -        
reverse osmose -         electrodialysys -        
ion-exchanger