The bacterial degradation of synthetic anionic detergents

Abstract

Experimental work carried out during the period from October 1966 to April 1968 has been concerned with the assessment of the biodegradability of synthetic anionic detergents, with particular reference to the “slope culture” technique. Solutions of the detergents known as JNX, JNQ, sodium tetrapropylene benzene sulphonate, a “difficult” alkyl benzene sulphonate and Dobane 055 were inoculated with bacteria from various sewage works effluents which had undergone prior acclimatization to a particular detergent on an agar slope; unacclimatized bacteria were also investigated. Further tests were carried out using a single, standard effluent and a microbial slime from an experimental recirculating filter together with a more stringent testing procedure. The results of all tests showed that the detergents had a low biodegradability value when compared with other methods, and they were inconsistent. Bacteria which degraded JNX were isolated from a sewage works effluent and from the microbial slime which developed on an experimental recirculating filter matured on JNX. Inoculation of the bacteria into a detergent solution was found to be ineffective in assessing their detergent degrading ability. A recirculating filter was developed for this purpose and proved to be successful. The active bacteria were members of the genera Klebsiella, Achromobacter, Flavobacterium and Micrococcus. The environmental conditions controlling detergent degradation by a pure culture of bacteria were also investigated. With the prior knowledge that the recirculating filter provided a favourable environment, each of its predominant physical characteristics was simulated individually. Degradation occurred in the presence of inert materials such as gravel, asbestos, or dried activated sludge provided that the detergent solution was vigorously agitated. The presence of an additional nutrient such as peptone did not appear to interfere with the normal degradation of the detergent. With the knowledge of the essential conditions for degradation, attempts were made to induce the bacteria E. coli and Serratia marcescens to degrade JNX in a recirculating filter; these attempts were unsuccessful.