Activated sludge acclimatisation kinetics to non-ionic surfactants

• Published in: Environmental technology Vol. 24; no. 1; pp. 109 - 114
• Main Authors: Carvalho, G., Novais, J.M., Pinheiro, H.M.
• Format: Journal Article
• Language: English
• Published: London Taylor & Francis Group 01-01-2003; Selper
• Subjects: Acclimatisation dynamics; Activated Sludge; Applied sciences; biodegradation kinetics; Biodegradation, Environmental; Biological and medical sciences; Biological treatment of waters; Biotechnology; degradation capadty retention; Environment and pollution; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General purification processes; Industrial applications and implications. Economical aspects; Industrial Waste; Kinetics; Pollution; Solubility; Surface-Active Agents - metabolism; surfactants biotreatment; transient state; Waste Disposal, Fluid - methods; Wastewaters; Water Movements; Water Pollutants - metabolism; Water treatment and pollution; Activated sludge; Kinetics; Waste water purification; Experimental study; Non ionic surfactant; Biological purification
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330309385541

The biodegradatíon of surfactants is a frequent and complex problem in domestic and industrial wastewater treatment processes. In addition to the resulting metabolites being sometimes refractory, the complete biodegradatíon of many of the most employed non-ionic surfactants requires long hydraulic retention times and the presence of specialised bacterial consortia. Preliminary acclimatisation tests highlighted the importance of the sludge acclimatisation state to a specific surfactant substrate for biotreatment efficiency. This paper reports on studies aimed at quantifying activated sludge acclimatisation and memory retention levels when subjected to changes in the type of surfactant included in the feed. Several transitions were tested, namely from an alkylphenol ethoxylate to a linear alkyl ethoxylate and the reverse, and between alkyl ethoxylates with different hydrophobic and hydrophilic molecular chain lengths. The kinetic results showed that sludge activation and memory loss were more dynamic for primary biodegradation. It was found that the sludge was harder to adapt to alkylphenol ethoxylate than to alkyl ethoxylate. The former also apparently introduced an inhibitory effect, resulting in very slow degradation kinetics when imposed to alkyl ethoxylate acclimatised sludge. When replacing an alkyl ethoxylate with another surfactant of the same family, a longer ethoxylate chain reduced the degradation rates. This effect was further enhanced by simultaneously increasing the hydrophobic chain length of the substrate. The acclimatisation kinetics after the replacement of an alkyl ethoxylate by a longer counterpart was slower than the reverse case, and memory was also more easily lost