Volume 17 [2015]

Petroleum products are used in different forms in auto-mechanic workshops every day. Spent motor oil disposed-off improperly contains potentially toxic substances which can seep into the water tables and contaminate ground water. This study involved isolation and screening of bacterial species capable of utilizing hydrocarbons from three auto-mechanic workshops in Abeokuta, Ogun State. Total Heterotrophic Bacterial Counts ranged from 1.03 × 10⁶ to 2.81 × 10⁶ CFU/g. Total Oil Degrading Bacterial Counts varied between 4.0 × 10⁵ and 2.01 × 10⁶ CFU/g while Surface Active Bacterial Counts were from 1.2 × 10⁴ to 2.76 × 10⁵ CFU/g. Twenty-four bacteria species capable of utilizing petroleum as a carbon source were isolated from various contaminated soils using enrichment technique. Isolated bacteria include: Bacillus spp., Pseudomonas aeruginosa, Micrococcus spp., Proteus mirabilis, Proteus vulgaris and Enterobacter spp. Redox indicator 2, 6-dichlorophenol indophenol (DCPIP) was used to screen for efficient hydrocarbon (Kerosene, Premium Motor Spirit, and Engine oil) degradation by bacteria. Degradation efficiency was measured by optical density at 600 nm. Micrococcus spp., Proteus mirabilis, and Pseudomonas aeruginosa were found to be the best isolates growing on majority of hydrocarbons due to their high utilization value when growing on the hydrocarbons tested.

Adsorption of Cu (II) ions by untreated sugarcane bagasse (USCB) and treated sugarcane bagasse (TSCB) was investigated. Sugarcane bagasse was treated with 0.1M oxalic acid prior to TSCB adsorption studies. Dependence of Cu (II) adsorption on pH, contact time, temperature and initial concentration of adsorbate solution were also investigated. Optimum pH 2 and contact time of 100 minutes were observed for both USCB and TSCB, while Cu II sorption increased with temperature. Under optimum condition, TSCB adsorbed Cu (II) ions better than USCB (1.854mgg^-1and 0.556mgg^-1respectively). Thermodynamic investigations showed that Cu (II) adsorption was feasible, spontaneous and endothermic. Kinetic data was adequately described by Ho’s pseudo-second-order kinetic model while intra-particle diffusion model described a slow adsorption affinity. It was concluded that Cu (II) adsorption by sugarcane bagasse is a favourable chemisorption process and was well explained by both Langmuir and Freundlich isotherms.

The United Arab Emirates (UAE) is one of the leading countries in the per capita bottled water consumption. This seems to be in controversy with adherences of local water authorities to stringent municipal water standards. A public survey (n= 891) was conducted to ascertain the perception of people in the country regarding bottled and tap water quality. The survey form was formulated based on the stated preference approach and was furnished in both Arabic and English languages. Some questions in the survey form require rating the quality of tap water and identifying the type of water the respondent drinks. For respondents who usually drink bottled water, they were asked to choose the reason(s) why they usually drink bottled water. Those who drink tap water more often were similarly asked to choose the reason(s) why they prefer tap water to bottled water. The study revealed that a large fraction of the UAE residents classify the quality of tap water as either good or excellent, yet many of them drink bottled water. This could be attributed in part to the high standard of living where the cost of bottled water is considered by the majority of the respondents as affordable. Other influential factors include the belief that bottled water has a better taste and concerns about tap water contamination. The latter may stem from the perception that water is not sufficiently treated or contamination is induced into the water from the distribution system or the in-house storage tanks. The study shows that more people in the UAE will drink tap water if relevant authorities provide information about tap water quality and if regular inspections and cleaning of the in-house storage tanks is conducted.

Sequencing batch reactor (SBR) is a time-oriented wastewater treatment (WWT) system in a single reactor with flow and energy input according to the predetermined operational cycle time. The treatment efficiency of SBR varies with the duration of the cycle time, which affects the reactor size and hence the cost of WWT plant. This paper presents an experimental study in a bench scale SBR model with a working volume of 15 L with an onjective to determine  the optimum cycle time for simultaneous removal of carbon and nutrient from the dairy wastewater. Using the equalized dairy wastewater experiments with four cycle times of 8 h, 6 h, 4 h and 2 h were conducted and the effluent concentrations were compared to the effluent standards. In conclusion, the data suggest the SBR process with 6 h cycle time as the optimum cycle time for treating dairy wastewater for simultaneous carbon and nutrient removal.