Physicochemical and Microbial Characterization of Treated and Untreated Produced Water

Introduction: The discharge of produced water into the aquatic environment presents a risk to the environment. This is a form of pollution and may release toxicants that are highly noxious to sensitive marine species even at low concentrations, which causes bio-degeneration/transformation and biodiversity loss.

Research Gap: There are insufficient literatures on extensive monitoring of the physicochemical and microbial characteristics of produced water. Existing literatures concerning analysis of treated and untreated produced water are not comprehensive with respect to number of physicochemical variables analyzed.

Aim: To ascertain if the physicochemical properties and microbial population of produced water were within acceptable regulatoy specifications.

Place and Duration of Study: The study was conducted in the Federal University of Petroleum Resources, Effurun, Delta State, Nigeria from July, 2021 – April, 2022.

Methodology: Electrical conductivity, dissolved oxygen, pH, temperature, turbidity, total petroleum hydrocarbons, nitrates, phosphates, sulphates and others were assessed using standard methods. Microbial counts were carried out for total heterotrophic bacteria and hydrocarbon utilizing bacteria using the pour plate method.

Results: Values obtained for some key physicochemical parameters monitored in the produced water are as follow: pH (8.10±0.03 for untreated and 8.27±0.01 for treated); electrical conductivity (35700±11 µs/cm for untreated and 41600±17 µs/cm for treated); total dissolved solids (22848±14mg/l for untreated and 26629±9mg/l for treated); dissolved oxygen (2.05±0.01mg/l for untreated and 4.23±0.03mg/l for treated); biochemical oxygen demand (28.90±0.7mg/l for untreated and 18.4±0.1mg/l for treated); phosphate (2.05±0.01mg/l for untreated and 4.23±0.03mg/l for treated); nitrate (54.82±1.9mg/l for untreated and 50.21±0.9mg/l for treated); total hydrocarbon content (118.00±0.00mg/l for untreated and 34.00±0.00mg/l); total heterotrophic bacteria (4.1e+04 CFU/ml for untreated and 2.8e+04 CFU/ml for treated); and hydrocarbon utilizing bacteria (2.44e+03 CFU/ml for untreated and 1.58e+03 CFU/ml for treated). Statistical analysis of the produced water showed varying forms of correlation between physicochemical parameters of untreated and treated produced water.

Conclusion: It is important to assess properties of produced water before disposal into aquatic environment as chronic impact associated with long-term exposures may pose potential ecological risks.