Abstract
The microbiological quality of refinery effluent, and water and sediments of the effluent receiving Okrika sector of bonny estuary was investigated. Treated waste water (TWW) recorded the highest total heterotrophic bacteria (THB) of 1.6 X 109 cfu/ml, while raw waste water had the highest bacterial diversity of 24.82%. The THB population of the water body was lowest (8.6X103cfu/ml) at the effluent outfall site (SS1) in January compared to the highest (1.10X108cfu/ml) recorded at the control station (SS6). The sediment samples were richer in microbial population density with highest value of 8.6X109cfu/g and least value of 7.8X104cfu/g recorded at SS6 and SS1 respectively. While fungi population showed significant upstream - downstream variation in sediment, the population of fungi in the water samples was relatively stable (3 logs) throughout the study period. The most predominant bacterial genera in the refinery effluent include Bacillus sp (23.37%), Pseudomonas sp (12.41%), and Staphylococcus sp. (10.59%). Similarly, Bacillus sp (15.73% & 16.77%) and Pseudomonas sp (13.72% & 11.44%) were the most prevalent in the river water and sediment respectively. Penicillum sp, Fusarium sp dominated the fungi population. The effluent outfall site (SS1) recorded the least generic diversity of 13.16% and 13.92% both for water and sediment samples respectively. Pollution of the Bonny estuary by refinery effluent resulted in changes in the microbial population density and disappearance of organisms like Chromobacter species, Vibro species, E. coli and Serratia species from the affected sites.
Highlights
In the last 40 years, Nigeria has experienced increased activities in the areas of crude oil exploitations, refining and product marketing operations
We present pilot data and information on the stability of microbial community of Okrika arm of Bonny estuary after more than 40 years of exposure to refinery effluent
The results obtained for the bacteria and fungi population of the different refinery effluents are presented in Table 1.The highest total heterotrophic count was recorded in Treated waste water (TWW), followed by Observation Pond Waste Water (OPWW), Raw Waste Water (RWW), Non-Process Waste Water (NPWW), and Process Waste Water (PWW) in decreasing order
Summary
In the last 40 years, Nigeria has experienced increased activities in the areas of crude oil exploitations, refining and product marketing operations. While these activities have generated immense financial benefits for the country, they have generated serious health and environmental problems. Related activities and accidental discharges contribute to the influx of these pollutants especially in the Niger Delta areas. The different types of pollutants which emanate from oil refineries have been known for years to have effects on the biological productivities of the ecosystem into which they are discharged. Chemical analysis of organic pollutants from Nigerian refineries [1], [2], [3] have identified 15 petroleum based hydrocarbons mostly phenols which are toxic to organisms. With acknowledged influence of some of these pollutants on other factors, it is obvious that there is a possibility of chemical interactions between these parameters which may affect the microbial population and diversity
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