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2779900 
Journal Article 
Degradation of a cationic surfactant in activated sludge pilot plants 
Fenger, BH; Mandrup, M; Rohde, G; Sorensen J, CK 
1973 
1 
Water Research
ISSN: 0043-1354
EISSN: 1879-2448 
HEEP/74/07093 
7 
8 
1195-1208 
HEEP COPYRIGHT: BIOL ABS. Tetradecyldimethylbenzylammonium chloride (TDBA) can be degraded in activated sludge pilot plants described, if proteins are present at the same time and also if TDBA is the only source of C. The reduction over a period of 21 days in 1 experiment averaged about 73, and 75% in a 2nd experiment. In a 3rd experiment the reduction was about 41.5%. This lower result was probably due to poorer operating conditions. Adsorption on the activated sludge probably accounts for only a small part of the reduction and most of it is due to biological degradation. The volumetric leading on the pilot plant and the O2 content in the aeration tank do not influence the degradation. Within the range of 15-25 degrees C temperature had little influence on degradation of TDBA. The following degradation products were demonstrated qualitatively: acetic acid, benzoic acid, and tetradecyldimethylamine. Bacteriological examinations show that degradation of TDBA caused a bacterial selection. Hardly any other bacteria than Pseudomonas and Comamonas were present in the activated sludge. Non-adapted activated sludge is strongly inhibited by a few ppm of TDBA. Sudden discharges of TDBA to a biological treatment plant would therefore badly upset the treatment plant in the absence of anionic surfactants which would probably neutralize their effect. Continous discharges of small amounts of quaternary ammonia compounds to an adapted activated sludge would hardly have any effect.