THE ANALYSIS AND FATE OF ACRYLAMIDE MONOMER IN AQUEOUS ENVIRONMENTS.
FINAL REPORT - DGR 480/306.
Report No DWI0084
- Analytical methods for the analysis- of acrylamide and acrylic
acid (a possible degradation product) have been developed and
published. The method capable of detecting acrylamide at trace (0.2
µg/l ) levels is somewhat time consuming owing to the derivatisation
and extraction procedures. To partially alleviate this difficulty an
additional rapid (8-20 minutes) screening method with a detection
limit of 5 µg/l acrylamide, was developed.
- Owing to its neutral polar nature acrylamide was not
significantly adsorbed onto solid surfaces other than activated
carbon during laboratory experiments.
- A wide variety of aerobic/anaerobic,
photo-synthetic/non-photosynthetic microheterotrophs which occur in
nature and polluted aqueous and sediment environments, possess the
ability to degrade acrylamide. Seasonal variations in the rate of
degradation occur owing to temperature differences. This effect is,
however, variable and cannot be predicted from basic temperature
kinetics without knowledge of microheterotroph community composition
etc. Chlorination and heavy metal pollution may prevent acrylamide
degradation for in excess of two months.
- Strong oxidising and reducing agents may degrade acrylamide, but
neither pH variation between 4 and 10 or the chlorination procedures
used in tapwater preparation change acrylamide.
- For the sewage works studied (activated sludge and biological
filter bed) no acrylamide loss was-noted during primary settlement,
confirming the laboratory studies that suggested that acrylamide
would not be adsorbed onto solid surfaces. An approximate 50% loss
of acrylamide was noted for both the activated sludge tanks and
biological filter beds. A loss of 0 to 8% was shown for the final
settlement tanks. Laboratory studies on collected sewage samples
showed the in situ acrylamide loss to be a biological process. As
rapid degradation of acrylamide was associated with biologically
active surfaces, it is possible that when polyacrylamides are used
to dewater sludges that the acrylamide which is initially entrained
in a polymer/sludge matrix might be degraded before diffusing into
- Degradation/adsorption studies using a river continuously
artificially dosed with acrylamide for three months could not
demonstrate any in situ mass loss of acrylamide, This further
supports the inference that acrylamide is not significantly adsorbed
onto solid surfaces. For the residence time of the stream studied
(4 - 5 hours) the continuous dosing of acrylamide was- insufficient
to acclimatise the microheterotrophs sufficiently to effect any in
situ degradation. Laboratory incubation of collected river samples
showed that prior to acrylamide exposure there was an increase in
degradative rate with river maturing. The continuous dosing of
acrylamide appeared to cause some additional increase in microbial
activity as shown by increased degradations rates.
- In situ exposure of aquatic insects to low levels of acrylamide
(5-40 µg/l ) caused mass mortalities, but the effect appeared to be
In conclusion it is considered that the improvements in
polymerisation procedures, which have lowered the acrylamide monomer
levels to less than 0.3% for many commercial products, has eased the
likelihood of serious acrylamide contamination of water through the
use of polyacrylamides. The use of high monomer content polymers,
the manufacture of polymers from monomer (either at factories or in
situ, as for sewer grouts, etc) and the recycling of waste paper
might still lead to significant acrylamide levels in potable waters.
The most common forms of sewage treatment seem to only remove
approximately 50% of the acrylamide input, although acclimatisation
might improve this figure. A one day preliminary survey at a
Yorkshire sewage works (which has received acrylamide discharges for
several years) showed that levels of acrylamide in the effluent were
comparable to the inlet levels. As acrylamide is not adsorbed or
chemically degraded in rivers and microbial activity is unlikely to
remove a significant proportion in less than a day, dilution must be
relied upon to protect water supplies. Potable water treatment
processes, other than activated carbon, do not remove acrylamide.
The sterilisation procedures for potable water preparation appear to
stabilise acrylamide in tapwater for in excess of two months. These
factors combined to make it imperative that preventive measures are
used to ensure that water sources are not contaminated. It is not
considered feasible to develop a technique with a detection limit of
0.2 µg/l acrylamide that is rapid enough for the screening of large
numbers of samples (i.e. 50 + per day) as such detection levels
require derivatisation and extraction procedures,which are of
necessity,time consuming. A rapid direct injection technique which
has a detection limit of 5 µg/l acrylamide has been developed at
this laboratory. It is suggested that a suitable means of monitoring
water supplies would be infrequent selective analysis for 0.2 æg/l
and routine analysis at the 5 µg/l level.
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