直鎖アルキルベンゼンスルホン酸塩の家庭用吸込式廃水処理ソウにおける生物学的分解性

アルキルベンゼンスルホン酸塩の生化学的研究 (第3報)

抄録

Detergent industries in occidental countries are going to change the non-biodegradable alkylbenzene sulfonates derived from tetrapropylene (ABS) to biodegradable linear alkylbenzene sulfonates (LAS) in relation to programs envisaging the protection of water. It is said that most of the domestic sewage in those countries is treated in the sewage treatment plant by activated sludge units or trickling filters, owing to the wide spread of the public sewerage systems. It is known that LAS is biodegradable in this aerobic condition.
In our country, most houses are provided with cesspools for their domestic sewage disposal systems. Little has been studied about the biodegradability of LAS in such relatively oxygen deficient conditions as in the cesspool and under the ground.
1. The detergent effect on the drainage behaviour in a newly prepared cesspool in a private lot A has been observed for 16 months, providing the test family with a specified light-duty LAS detergent as a substitution of commercial ABS detergents for their kitchen use. It was discovered that the test cesspool had maintained good drainage in comparison to the former cesspool which was located beside the test cesspool.
As there has been no remarkable change in the consumption of the detergent and water since the changeover of the detergent and no difference was found in the bacteriostatic activities of LAS and ABS, the actual concentration of LAS in the test cesspool is presumed to be low enough to show no bacteriostatic action on bacteria which can degrade organic materials in the sewage.
2. The migration of the undegraded detergent residues from a cesspool into its neibouring well water was studied in the test lot A and in a private lot B of a nearly identical sewerage system and soil condition. It was found that the contamination of the detergent residues into well water (13m in depth) was undetectable in lot A. On the contrary, the trace amount of the detergent residues was observed in 20 meters deep well water of lot B where commercial ABS detergents had been used. This result shows that LAS is more biodegradable or removable than ABS in the cesspool or under the ground.
3. The biodegradabilities of four kinds of LAS and ABS were investigated by the aerobic storage test. All LAS showed more than 80% biodegradation within 24 hrs in the acclimated biological system prepared from sewage in the test cesspool, but nearly 48 hrs were needed to reach the same order of biodegradation in a similarly acclimated biological system prepared from sewage in the other cesspool of lot B.
Under aerobic and anaerobic conditions, bacterial counting and their isolation were carried out on a soil sample taken from the bottom of the test cesspool with bouillon agar medium and synthetic agar medium containing 0.2% LAS.
From the fact that those bacteria can grow on a synthetic medium containing 0.2 or 0.78% LAS as a whole source of hydrocarbon under aerobic and anaerobic conditions, it is suggested that LAS is biodegradable in the cesspool or under the ground. Identification of those effective baceria and the study on their ability to degrade LAS will be accomplished in the near future.