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TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Anaerobic Treatment of Textile Dyeing Wastewater
(within extra work agreed on in the last meeting, combining workpackages)
Lettinga Associates Foundation
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Work packages integrated
• WP05.05.3 (Centexbel)– Tests for water reuse
• WP06.05.5 (LeAF)– Tests by anaerobic bioreactor
• WP06.07.1 (ENEA)– Membrane tests to produce reusable water
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Overall experiment
Membranetreatment
Anaerobictreatment
Reusetests
Raw wastewaters
AnaerobiceffluentsMembrane
effluents
LeAF
ENEA
Centexbel
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
The part of LeAF
• Anaerobic pre-treatment of dyeing wastewater for membrane treatment with the objective of reuse
• Treatment of two streams:– Reactive dyeing and acid dyeing wastewater
• Recording of respirograms of water from the different treatment stages
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Previous presentation
Project meeting in March:Results of the continuous experiment were presented
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Memory refresher - some of the conclusions
• Reactor set-up was not optimal
• Passing all effluent twice through the reactors did improve colour removal for acid dyeing, not for reactive dyeing
• Size waste seems a suitable co-substrate for anaerobic decolourisation
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
What is new?
• Batch experiments conducted to get more insight in anaerobic treatment of the same two wastewaters– Comparison treatment at 30ºC / 55ºC – Application of electron mediator to whether
performance can be improved
• Respirograms
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Batch experiments
• Bottles of 120 ml• Filled with 50 ml wastewater• Headspace N2-CO2 (70%-30%)
• At 30ºC with size as co-substrate• At 30ºC and 55ºC with VFA/Glucose• In presence and absence of AQS as
electron mediator
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Electron mediation
• Biological reduction of dyestuffs is non-specific process
• Usually slow, mediator accepts electron faster and transfers it to dye molecule
• Widely tested with single azo dyes, little known about effect in real wastewaters
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Azo dye reduction
Ba
cte
riu
m
Electron donor
Electron donor
(oxidised)
Azo dye
Aromatic amines
Medium
Next: electron mediator is AQS (AnthraQuinone-2-Sulphonate)
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Mediated azo dye reduction
O
OSO3H
OH
OHSO3HB
act
eri
um
Electron donor
Electron donor
(oxidised)
Azo dye
Aromatic amines
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
0
20
40
60
80
100
0 1 2 3 4t (d)
Colo
ur
(% le
ft)
0
20
40
60
80
100
0 1 2 3 4t (d)
Colo
ur
(% le
ft)
Reactive dyeing - thermo/meso
O = Chemical control = Sludge+ww+VFA/Glucose Sludge+ww+VFA/G+AQS
420 & 500 nm 610 nm
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Reactive dyeing
• 420 and 500 nm: results as expected– Thermophilic incubations show faster
decolourisation– AQS speeds up decolourisation rates
• 610 nm: unexpected behaviour– all incubations have the same rate,
although thermophilic bottles reach better final decolourisation
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
0
20
40
60
80
100
0 2 4 t (d)
Colo
ur
(% le
ft)
0
20
40
60
80
100
0 2 4 t (d)
Colo
ur
(% le
ft)
Acid dyeing - thermo/meso
O = Chemical control = Sludge+ww+VFA/Glucose Sludge+ww+VFA/G+AQS
475 nm 620 nm
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Example of acid dyeing spectra(Mesophilic incubation with co-substrate and AQS)
0.0
0.5
1.0
1.5
2.0
2.5
400 500 600 700 800nm
A
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Acid dyeing
• 620 nm: Mesophilic results as expected
– Thermophilic is faster, but AQS has no effect– AQS has effect under mesophilic conditions
• 475 nm: unexpected behaviour
– Decolourisation lines are chaotic, but:– When looking at spectra, product formation
can be seen for incubations with AQS
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Additional results
• Size waste vs VFA/Glucose mixture– No significant differences (both wastewaters)– Size waste is an interesting co-substrate
• Formation of precipitates after time– After 14 days acid dyeing controls (chem.
control & sludge+ww) suddenly decolourised. Dark blue flocs had been formed.
– In biologically active bottles (+Co / Mediator) there were also flocs, but grey.
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Conclusions
• Thermophilic treatment is advantageous– Most dyeing effluent is hot, no need to cool down– Faster than at 30ºC with mediator
• Decolourisation depends on dye type– Chosen wavelengths represent different dyes– In this way different behaviour can be followed– Important to know dye structures beforehand to
be able to draw conclusions
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Conclusions
• Electron mediator– Can largely increase decolourisation rate and
improve final colour for mesophilic treatment – Does not work for all dye types
• Need for more knowledge on:– behaviour of different dye types in anaerobic
treatment under different conditions– effect of mediators in different kinds of real
wastewater to assess their potential
TOWEF0 - Paris - October 2003 Lettinga Associates Foundation
Integration batch/continuous
• Reactive dyeing:– Batch results comparable with reactor
results in first days of reactor operation
• Acid dyeing:– Batch results better than reactor results– Improvement of colour removal when using
effluent as influent probably due to mechanical filtration of precipitates formed in effluent during storage
