Journal of Biology, Agriculture and Healthcare www.iiste.org ISSN 2224-3208 (Paper) ISSN 2225-093X (Online) Vol.4, No.1, 2014 23 Effects of Different Concentrations of Biocides on Fungal Populations, Isolated from Biofilms of Corroded Oil Pipelines, Niger Delta Region, Nigeria Godwin U. Akpan 1 , Marian G. Solomon 2 and Godwin Abah 3 . 1.Department of Soil Science and Land Resources Management, University of Uyo, P.M.B. 1017, Uyo, Nigeria 2.Department of Soil Science, University of Calabar, P.M.B. 1115, Calabar, Nigeria 3.Department of Animal Science, University of Uyo, P.M.B. 1017, Uyo, Nigeria E-mail of the corresponding author: godwinuakpan@uniuyo.edu.ng, agumoren1@yahoo.com Abstract Microbiologically influenced corrosion is a problem commonly encountered in facilities in the oil and gas industries. The present study described fungal enumeration and identification in biofilms of oil pipelines in Oshie flow station in Rivers State and Irri flow station in Delta State, Nigeria using traditional cultivation technique. The fungal species isolated in biofilms from the two sites are as follows Verticillium dahlae, Saccharomyces cerevisiae, Penicillium corylophilum, Botrytis cinerea, Fusarium oxysporum, Aspergillus paradoxus, Humicola grisae, Aureobasidium pullulans, Monilia balanitis, Hormoconis resinea, Asperillus flavus and Helimenthosporium maydis. The study also focuses on the use of three biocides to inhibit or eliminate the identified organisms in order to minimize the material and financial losses encountered by oil and gas companies, because of microbiologically influenced corrosion (MIC). The performance of three biocides (ozone, sodium hypochlorite and formaldehyde) at the concentrations of 0, 1, 2, 3, 4 and 5% in eliminating the fungal species isolated from biofilms of oil pipelines in Rivers and Delta States, Niger Delta, Nigeria. It is shown, that formaldehyde, ozone exhibited the best biocidal characteristics and concentrations of 1 and 2 % eliminated almost all the fungal species after 72 hours of contact time. This study is relevant to the problem of microbiologically influenced corrosion as the data may contribute to elucidate which fungal species contribute to the MIC process and to gain a better understanding of the fungal community of biofilms. This study will give us better understanding of the biocide capable of eliminating fungal species in biofilm of oil and gas pipelines. Keywords: Concentration, fungal population, biocides, microbiologically influenced corrosion, biofilms 1. Introduction Microbiological influenced corrosion of mild steel pipelines is an important economical problem facing oil and gas industries. Microbes form tubercles, which block fluid flow and can facilitate localized corrosion leading to through-wall penetrations. Microbes of diverse physiological types and metabolism potentialities have been recovered from fresh tubercles or under-deposits corrosion and characterized. Microbiological influenced corrosion is increasingly recognized as a serious problem when metal surfaces are exposed to natural waters (Pope et al., 1984). Microbiologically influenced corrosion or biocorrosion is a corrosion problem in the oil and gas industries facilities. These may occur when microbial consortia interact with metallic surfaces through the establishment of multispecies biofilms in which different microorganisms contribute to corrosion through a co- operative global metabolism (Little and Ray 2002; Frenchel 2002). Corrosion affects the operation and maintenance cost of the pipelines, and many oil pipelines face severe corrosion and biofouling problems (Benka Coker et al. 1995). Generally, most microbiologically influenced corrosion studies focused only on bacterial involvement, however, under aerobic conditions, other singled celled organisms such as fungi, yeast and diatoms can influence corrosion (Prasad, 2000). The predominant types of fungi associated with MIC are acid producing fungi (Hormoconis resiaea) hydrocarbon utilizing fungi heterotrophic fungi (Saccharomyces cerevisiae) and fungi secreting organic acids and slime (Puyate and Rim-Rukeh, 2008). These organisms coexist within a biofilm matrix of metal surfaces, functioning as a consortium in a complex and coordinated manner. The various mechanisms of biocorrosion reflex the variety of physiological activities carried out by these different types of microorganisms when they coexist in biofilms (Al-Saleh et al., 2011). The activities of these microorganisms causing corrosion of petroleum pipelines may be controlled or inhibited by the application of biocides or surfactants (Lechevallier et al., 1988). Examples of biocides are chlorine, sodium azide, glutaraldehyde and sodium hypochlorite (Videla, 1996). Despite decades of study on MIC, it is still not known with certainty how many species of microorganisms contribute to corrosion and researchers continue to report on the formation of biofilms by an