The study sought to find out how hydrocarbons are broken down in effluent from petrol stations by the existing bacteria in the
effluent. This was established by collecting samples from two petrol station interceptors and subjecting them to
chromatography tests as well as bacterial enumeration experiments over a period of forty days. It was observed that various
changes took place in the samples from the chromatography results, whereby the constituent hydrocarbon quantities reduced
significantly and in some cases they got eliminated completely. It was also confirmed that there existed various strains of
bacteria in the samples and their population increased for a period of time until it reached an optimum where the population
stagnated. Both observations realized enhanced changes and faster growth of microorganisms where nitrogen and phosphorous
had been added to the samples.