Author: Okaa Anthony Ifeanyi
Department: Applied Microbiology
Affiliation: Nnamdi Azikiwe University Awka
Biodegradabilities of surfactants in seven detergents namely Morning Fresh, Mama lemon, Newday Fresh, LB wash `N’ Wax, Classic Handwash Fresh, Lily Fresh and a Standard-Sodium Dodecylsulphate (SDS) were determined using the river water die-away method. The ease of degradation over a 28-day monitoring period followed the order- SDS (90%), Lily Fresh (85%), Newday fresh (77.50%), LB wash `N’ Wax (60%), Mama Lemon (57%), Classic Handwash (50.75%) and Morning Fresh (50%). Lily Fresh has a chemical oxygen demand (COD) value of 3900mg/L (highest) while Morning Fresh had the least with 1560 mg/L in the original liquid detergents. Newday Fresh recorded the highest nitrate concentration of 350mg/L while Mama Lemon recorded the lowest concentration of 150mg/L in the original liquid detergents. Lily Fresh had the highest sulphate concentration of 1500mg/L while Morning Fresh had the least with a sulphate concentration of 650mg/L in the original liquid detergents. There were marked decreases in chemical oxygen demand, sulphate and nitrate concentrations during the river water die-away tests of the liquid detergents. The initial (day 0) and final (28th day) chemical oxygen demand concentration of the samples were in the following order: LB Wash ‘N’ Wax (165mg/L
and 25mg/L), Classic handwash (200mg/L and 30mg/L), Newday Fresh (200mg/L and 30mg/L), Morning Fresh (140mg/L and 35mg/L), Sodium dodecyl sulphate (200mg/L and 35mg/L), Mama Lemon (150mg/L and 45mg/L) and Lily Fresh (250mg/L and 45mg/L). The initial and final days sulphate concentrations of the samples were as followed: LB Wash ‘N’ Wax (75mg/L
and 5mg/L), Morning Fresh (65mg/L and 6mg/L), Mama Lemon (84mg/L and 7.50mg/L) Classic handwash (95mg/L and 8mg/L), Sodium dodecyl sulphate (80mg/L and 9.50mg/L) Newday Fresh (120mg/L and 10mg/L) and Lily Fresh (150 mg/L and 10.50mg/L). The mean pH of the river water in the presence of the detergents over the 28-day period ranged from 6.2 to 7.8. The mean counts of detergent utilizing bacteria in the river water ranged from 3 x 104 cfu/ml to 1.04 x 106 cfu/ml, with a percentage range of 1.9 to 66.2. The total viable counts of the samples increased steadily during the river water die-away tests and recorded the highest counts on the 20th day in the following order: SDS (8.7 x 104cfu/ml), Classic handwash (9.0 x 104cfu/ml), LB Wash ‘N’ Wax (9.4 x 104cfu/ml), Mama Lemon (9.8 x 104cfu/ml), Morning Fresh (1.13 x 105cfu/ml), Newday Fresh (1.33 x 105cfu/ml) and Lily Fresh (1.65 x 105cfu/ml). The following
bacteria: Escherichia coli, Pseudomonas aeruginosa, Bacillus sp, Citrobacter freundii, Flavobacterium sp, Staphylococcus haemolyticus, Enterobacter aerogenes and Salmonella sp were found to effect the degradation with Pseudomonas aeruginosa predominating. There were positive correlations between the pH, nitrate, sulphate and COD values with their respective total viable counts of the samples during the biodegradation test. There was a significant difference (P<0.05) between the mean pH and nitrate values; mean pH and sulphate values; and, mean pH
and COD values of the samples respectively during the biodegradation test. With the exception of SDS, it was concluded that the detergent that supported the highest microbial growth was the most easily degraded and have provided an insight to the fate of these surfactant components in the aquatic environment.
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