Surfactants, activated sludge test

This test method comprises a continuously operating activated sludge test which is recommended by OECD as a Confirmatory Test [60] for anionic surfactants and has been included in the relevant EEC guideline [58] in the form of a reference test. 

Shake flasks were inoculated with mixed liquor suspended solids from activated sludge units in a Houston area domestic waste sewage treatment plant. Initial surfactant concentrations were 20 mg/ . CO2 formed from biodegradation was trapped in aqueous Ba(OH)2. The amount of CO2 formed was determined by back-titrating residual Ba(OH)2 with HCl at the end of each test period. Glucose was included as a positive biodegradation standard. 

In the confirmatory test, activated sludge from a domestic sewage treatment plant, test surfactant (20 mg/1) and synthetic sewage of composition... 

Considering these aspects, two test methods have been developed for the determination of the degradability of surfactants which simulate the conditions in effluent purification (continuous activated sludge process) or in the receiving body of water (static screening test). Because of their relative simplicity they can be carried out in large series as a matter of routine. 

May and Neufahrt [81] have reported on the behaviour of the cationic surfactant distearyldimethylammonium chloride (DSDAC) in sludge-activating units. In the OECD Confirmatory Test, they obtained elimination rates of between 91% and 93% at a feed rate of 2.78 mg of DSDAC/1 or 1.75 mg of DSDAC/1, with an... 

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