THE ANALYSIS AND FATE OF ACRYLAMIDE MONOMER IN AQUEOUS ENVIRONMENTS. FINAL REPORT - DGR 480/306.
Report No DWI0084

OCT 1980

SUMMARY

  1. 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 g/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 g/l acrylamide, was developed.
  2. Owing to its neutral polar nature acrylamide was not significantly adsorbed onto solid surfaces other than activated carbon during laboratory experiments.
  3. 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.
  4. 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.
  5. 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 the water.
  6. 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.
  7. In situ exposure of aquatic insects to low levels of acrylamide (5-40 g/l ) caused mass mortalities, but the effect appeared to be species selective.

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 g/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 g/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 g/l and routine analysis at the 5 g/l level.

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