Abstract
High volumes of formation water comprising of complex mixture of hydrocarbons is generated during crude oil exploration. Owing to ecotoxicological concerns, the discharge of the formation water without remediation of hydrocarbonaceous pollutants is not permitted. Keeping this into mind, we carried out phycoremediation of hydrocarbons in formation water so that it can be safely discharged or re-used. For this, a native algal species was isolated from formation water followed by its morphological and 18S ribosomal RNA based identification confirming the algal isolate to be Chlorella vulgaris BS1 (NCBI GenBank Accession No. MH732950). The algal isolate exhibited high biomass productivity of 1.76 gm L−1 d−1 (specific growth rate: 0.21 d−1, initial inoculum: 1500 mg L−1) along with remediation of 98.63% petroleum hydrocarbons present in formation water within 14 days of incubation indicating an efficient hydrocarbon remediation process. Concomitantly, the hydrocarbon remediation process resulted in reduction of 75% Chemical Oxygen Demand (COD) load and complete removal of sulfate from formation water making it suitable for safe disposal or reuse as oil well injection water respectively. The present process overcomes the bottlenecks of external growth nutrient addition or dilution associated with conventional biological treatment resulting in a practically applicable and cost-effective technology for remediation of oil field formation water.
Highlights
High volumes of formation water comprising of complex mixture of hydrocarbons is generated during crude oil exploration
The comparison indicated that the concentration of Total Petroleum Hydrocarbons (TPH) and Chemical Oxygen Demand (COD) in the formation water is well beyond the permissible limits prescribed by regulatory agencies for its safe disposal
The present study developed a new method for remediation of petroleum hydrocarbon-rich formation water
Summary
High volumes of formation water comprising of complex mixture of hydrocarbons is generated during crude oil exploration. Since the bioremediation process is based on the application of algal species native to oil field formation water, it is expected that the algal isolate will be able to meet its quintessential growth requirement of carbon and macro/micro-nutrients from the petroleum hydrocarbons and ionic composition found in formation water respectively. This implies that the present microalgal remediation process will overcome the conventional bottlenecks compromising the practical applicability of bioremediation strategies as requirement of external nutrient supplementation or dilution of the oil field formation water to maintain biomass growth
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