Optimization of Biodegradation of Phenol in a Refinery Effluent Treatment Facility

Background: Regulatory agencies in Nigeria and all over the world demand that refinery wastewater (RWW) meet stipulated regulatory limits before discharge into the environment. Biodegradation of toxic hydrocarbon constituents of these effluents, such as phenol, has remained a challenge with regards to compliance with regulatory requirements.
Aims: This study investigated the effect of micronutrients and macronutrients on the biodegradation of phenol in RWW.
Methods: The micronutrients used in the study were CoSO4, MnSO¬4, ZnSO4 and CuSO4 while the macronutrients comprised urea and NPK. Range-finding and optimum concentration tests were performed for each of the nutrients. The experiment was carried out in a 3L Erlenmeyer’s flask incubated in a rotary shaker under experimentally determined optimum cultural conditions, using a fractional factorial design. Phenol concentration (mg/ml) was monitored daily throughout the experiment using spectrophotometric method.
Results: The result obtained from the study revealed that a combination of CoSO4, MnSO¬4 and NPK was most efficient in enhancing the degradation of phenol in the RWW. After three days of incubation, phenol concentration of 141.99 mg/ml was reduced to 0.1 mg/ml. This value is lower than the phenol concentration of 0.5 mg/ml recommended for discharge of RWW into the environment. The degradation model derived from the study can be represented with the equation, y = 8.4998e-2.302x and R² = 0.961.
Conclusion: This study has revealed that the combination of CoSO4, MnSO¬4 and NPK can efficiently enhance phenol degradation in RWW for effectual compliance with the regulatory discharge limit. This study has also demonstrated the positive effect of micronutrients and macronutrients on the biodegradation of refinery effluent. Amongst all the nutrients screened, the combination of NPK, MnSO4 and CaSO4 was most efficient in enhancing the biodegradation of phenol in RWW. This could be as a result of preferential assimilation of these specific nutrients by the microbial culture involved in the degradation. Operators of petroleum refineries in Nigeria should employ the synergistic effect of micronutrients and macronutrients in stimulating the microbial culture for optimal biodegradation of phenol in RWW as identified in this research.