The effect of temperature on the removal of non-ionic surfactants during small-scale activated-sludge sewage treatment—II. Comparison of a linear alkyl phenol ethoxylate with branched-chain alkyl phenol ethoxylates

Abstract

The biodegradability of a linear alkyl phenol ethoxylate surfactant has been compared with the biodegradabilities of two branched-chain alkyl phenol ethoxylates during sewage treatment in small-scale activated-sludge plants. In addition, a linear alkyl benzene sulphonate (LAS) anionic surfactant was tested to study its removal during treatment in the “porous-pot” equipment. Tests were carried out at ≈ 20°, 12°, 8° and 5°C to study the effect of temperature on the removal of the different materials. Very little difference was found between the degrees of removal of any of the alkyl phenol ethoxylates. They were well degraded at 20°C, but a stable degree of removal could not be maintained at reduced temperatures. At 8°C and 5°C the percentage removals fluctuated between 60 and 90 per cent. This appears to be a feature of the behaviour of alkyl phenol ethoxylates during this type of treatment. The LAS surfactant, after a period of acclimatization, was consistently degraded by more than 90 per cent at all temperatures of operation.