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Biodegradation of
synthetic detergents in wastewater
Olusola A. Ojo1*
and Benjamin A. Oso2
1Department
of Microbiology, Lagos State University, Badagry Expressway,
P.O. Box 12142, Ikeja, Lagos-Nigeria.
2Department
of Botany/Microbiology, University of Ibadan, Nigeria.
*Corresponding author.
E-mail:solayom@yahoo.com.
Tel: +234 – 8055055478.
Accepted 13
January, 2009 |
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A total of 76 wastewater samples were randomly collected from
pharmaceutical, textile, and detergent-manufacturing
industries as well as the Agbara Sewage Treatment Plant (STP).
Thirty-eight samples each in 2-L plastic containers were
collected for morning and evening effluent used for this
study. Composite samples were later developed and the
physico-chemical properties of these samples determined. The
physico-chemical properties of the composite wastewater
influenced the selected microbial population adapted to
utilization of detergent components. The optimum temperature
range of the composite wastewater was 33.9 – 34.3oC
while the mean optimum pH ranged from 6.9 – 8.8 for the
laboratory simulated biodegradation of test detergents.
Although, the fungal consortium was eliminated as the medium
approached the alkaline pH, this is as a result of the
metabolites produced. The macro-elements, the BOD and the
hydrocarbon concentration of the composite effluent were
above the EU and FEPA limits for discharged effluent. The
composite effluent was thereafter spiked with test
detergents (Elephant, Omo, Klin, Ariel Persil, Teepol, and
SDS) at 0.01% (w/v) and its progressive degradation
monitored for 30 days. The microbial detergent-degraders
population changed between Day 0 and 15, thereafter it
stabilized. The heterotrophic bacterial count from the
seventy-six randomly collected effluent samples was 42.9 x
106 cfu/ml, while the mean bacterial
detergent-degrader population was 20.94 x 106 cfu/ml.
The mean fungal population from the randomly collected
effluent sample was 4.5 x 106 cfu/ml. The
bacterial detergent-degraders characterized and identified
include Pseudomonas aeruginosa, Escherichia coli,
Enterococcus majodoratus, Klebsiella liquefasciens,
Enterobacter liquefasciens, Klebsiella aerogenes,
Enterobacter agglomerans, Staphylococcus albus,
Proteus sp., Klebsiella oxytoca and
Brevibacterium sp., while the fungal
detergent-degrader included; Myceliophthora thermophila,
Geomyces sp., Alternaria alternata, Fusarium
sp., Aspergillus flavus and Asperigillus
oryzae. The primary biodegradability of synthetic
detergent was confirmed by the Methylene Blue–Active
Substance (MBAS) method. Gas chromatography (GC) provided
the convincing evidence of synthetic detergent
mineralization within the 30 day period in a sewage
treatment plant. The detection of unusual peaks in the GC
profiles provided the scientific evidence of inclusion of
certain hydrocarbons in detergent formulation outside that
of industry specifications. The unusual peaks are
attributable to inclusion of certain chemical optical
brighteners (C17–C24). Linear alkyl
benzene sulphonates (LAS) which is the principal synthetic
detergent component are thus biodegradable and its use in
detergent formulation is environment - friendly.
Key
words:
Biodegradation, detergents, linear alkylbenzene sulphonate,
sustainable development. |
