Abstract

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 – 34.3^oC 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, Proteussp., 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 (C_17–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.