The biodegradability of ethoxylates based on synthetic primary alcohols and on iso‐octylphenol has been evaluated by field trials with a trickling filter sewage treatment plant serving a small community. Ethoxylates based on synthetic alcohols showed good biodegradability in the trickling filter even in winter. This is in line with laboratory tests. Effluents were practically nonfoaming and on further aeration an ultimate biodegradability of 99% was achieved. Ethoxylates based on iso‐octylphenol biodegraded in winter to an extent of some 20% only. In summer, values as high as 80% were obtained. In general however ethoxylates of this type cannot be considered biodegradable. Effluents showed a considerable tendency to foam even under summer conditions.

The biodegradability of a number of linear alkylbenzene sulfonates (LAS) has been evaluated by field trials with a trickling filter sewage plant serving a small community. All the LAS material examined showed a satisfactory order of biodegradability. In all the LAS materials examined, aeration of the sewage effluent resulted in further biodegradation to a degree corresponding to 96% to 99% degradation of the LAS present in the settled sewage. The results of laboratory scale biodegradation tests are largely in agreement with those obtained in the field trials. However, with tests of the simple open bottle type, such as the test of the U.K. Standing Technical Committee on Synthetic Detergents, misleading indications of low biodegradability may sometimes be obtained on products of higher molecular weight. Such products do not appear to acclimatize sufficiently rapidly to bacteria under the conditions of the open‐bottle test. Under practical sewage treatment conditions, or with tests which simulate these, a high order of biodegradation is obtained. There were only minor differences in biodegradability between an LAS derived from paraffins and those derived from cracked wax olefins.

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The biodegradability of primary alcohol sulphates derived from a coconut alcohol and from a synthetic alcohol (Dobanol 25 -Shell trademark, known as Ncodol in the U.S. and Canada) has been evaluated by field trials with a trickling-filter sewage treatment plant serving a srrall community. Both these materials showed a high order of biodegradability, average values in the 96-98% region being obtained. On aeration of effluents in the laboratory further degradation to 99% was achieved with both alcohol sulphates. Effluents containing only residues of either alcohol sulphate were practically nonfoaming.