Category	% biodegrdation at 'n' the day
	2	4	6	8	10	14	19	24	28
LAS-1*	0.41	1.86	23.65	37.90	54.20	61.34	66.46	67.85	68.93
LAS-2	0.32	2.98	9.01	23.61	40.23	57.62	63.80	60.37	68.09
LAS-3	0.31	5.32	19.80	34.83	49.50	61.40	68.29	69.67	70.53
AOS**	0.80	18.67	34.31	55.31	68.27	75.42	73.37	82.75	83.80
EMP/MLA***	7.80	23.49	57.40	67.80	75.70	80.90	86.10	88.70	91.32
PRODUCT	19.21	28.80	39.29	50.97	62.10	67.06	70.03	72.03	72.12
PRODUCT	0.18	0.35	1.67	12.80	18.90	40.00	72.20	83.13	87.70

*	-	LAS - Linear alkyl benzene suplhonate
**	-	AOS - Alpha olefin sulphonates
***	-	ENP/MLA - Ethoxylated nonyl phenol/methyle lavryl aminoxide

Reporting of results

The amount of C02 produced by the test compound during the test is measured and expressed as percent of the theoretical carbon dioxide it should have produced (TCO2), as calculated from the carbon content of the test compound (TOC).

TCO2 = mg CO per mg of test material

TCO2 (%)                        =          mg CO2 Produced          X 100
                                             mg test matrial added x TC02

Biodegradability %           =          Amount of C02 produced          X 100
                                                   Theoretical amount of CO2

The test matrials giving a result of greater than 60 percent yield of carbondioxide (within 28 days) are regarded as readily biodegradable and this level i.e. (60% yield) must be reached within initial 10 days.

RESULTS AND DISCUSSIONS

Tests were carried out with seven samples of detergent raw materials and products. The extent of degrada­tion varies with the type of active matter and other additions in formulation. The results are presented in Table 1. The graphical representation of results is given in Figures 3.1 - 3.7.

Both LAS and AOS gave consistent results and met the criteria of biodegradation as per OECD-301-B. Biodegrdation levels exceeded 60% in all cases. The 60% degradation level was reached in 14-16 days in case of LAS and within 10 days in case of AOS. First 10% degradation was reached within 5 to 7 days. Degradation rate was linear till about 60% and susequently declined. Nonyl phonol also showed excellent degradation characteristics reaching maximum level of 90%.

Additionally, two detergent products were also tested. Both these showed degradation levels over 60%. The degradation curves show less predictability due to complex nature of these formulated products, which contain several other additives, in addition to active detergent matters. In case of product-2, the onset was sluggish and 10 % level was dealyed till 8 days and thereafter it degraded rapidly reaching 60% within further 10 days.

Thus it was observed that

1. OECD-301B (modified sturm test) showed excellent and consistent results for testing detergent raw materials and products, under climatic conditions at Mumbai.


2. Both LAS and AOS showed adequate degradation levels. However, AOS showed better degradation.


3. Nonyl pheno/Lawryl alcohol-based active matter also showed excellent degradation.


4. Detergent products tested (2 nos) passed the test.

4.4 Suggestions for further work

1. Comparative study of LAS and AOS needs to be conducted to confirm their relativede gradation.


2. Detailed studies with more number of commercially available formulated products in India should be attempted. This hsould cover the retarding effects of the additives used in soaps and detergents.

REFERENCES

1. Arthur D. Little "Environmental and human safety of major surfactants". Final Report to soap and Detergent Association, New York, Vol-1, Feb. 1991.


2. Paintee HA. and Zebel T.F. "Biodegradation of LAS" Review of the environmental safety of LAS, 1988.


3. Paintee HA. and Zebel T.F. "Biodegradation of LAS" Review of the environmental safety of LAS, 1988.


4. Mishra Virendra, Pande Shridhar and Vishwanathan T. N. "Retardation of biodegradation of LAB by sublethal concentration of mercuric chloride". Bull environmental contamination and Toxicology, vol 47, 1991.


5. Beltrame Paolo and Beltreame Pier Luigi "Kinetics of phenol degradation by activated sludge in a continuous stirred reacter" Journal WPCF, Vol 52, 1980.


6. J. Part and A Gi raud.eds - "The pollution of water by detergents", Organisation for Economic cooperation and development, 1964.


7. Nyholm Niels, Damborg Axel and Lindgaard Palle "A comparative study of test methods for assessment of the Biodegradability of chemicals sea water - screening tests and simulation tests" Ecotoxicology and Environmental safety, vol 23, 1992.