Response of nitrosomonas, nitrobacter and escherichia coli to drilling fluids. – L.O. Odokuma and E. Akponah
Inhibition of ammonia oxidation by Nitrosomonas, nitrite consumption by Nitrobacter and carbon IV oxide evolution by Escherithia coil were employed as indices to determine the effect of four drilling fluids (Paradril, IMCO-W, IMCO-O and Gel/KCL/polymer to these bacteria. The percent log survival of these bacteria when exposed to these fluids was also used as an index. Ammonia oxidation was monitored as nitrite accumulation. Both nitrite accumulation and nitrite consumption were determined by coupling of diazotised sulfanilic acid with -napthylethylene diaminedihydrochloride. Result revealed decreases in the percentage log survival with increasing concentration of the drilling fluids and increasing exposure period of the three bacteria. Nitrite accumulation in cultures containing Nitmsomonas decreased with increase in concentration and exposure time of the four fluids. Controls (containing Winogradsky Phase I with Nitrosomonas and no toxicants) revealed an increase in nitrite accumulation with increase in exposure time. Nitrite consumption in Nitmbacter containing cultures decreased with increase in concentration and exposure time to fluids. Controls (containing Winogradsky Phase II with Nitrobacter and no toxicants) showed a similar trend but the decrease was not as rapid. Carbon IV oxide evolution in cultures containing E. coil generally decreased with increase in concentration and exposure time to fluids. Controls (containing lactose broth with E. coli and no toxicant) revealed an increase in CO2 evolution with increase in exposure time. These results showed that the drilling fluids inhibited the two stages of the nitrification process in the ecosystem and also respiration by Escherichia coil. This may affect the agricultural productivity of ecosystems in the Niger Delta with regards to causing dislocation in the nitrogen cycles where nitrifying bacteria participate and the detritus food chain where aerobic) and facultative anaerobes like E. coil are important.