Public Health Risk Assessment of Treated and Untreated Produce Water Effluent

Abstract

Discharge of produced water into the aquatic environment may release chemicals that are highly toxic to sensitive marine species even at low concentrations, causing bio-degeneration/transformation of the biota. Some metals and hydrocarbons may accumulate in sediments, bio-accumulate in bottom living biological communities which may pose threat to humans and animals. Physicochemical quality of untreated and treated produced water were assessed.Toxicity and pollution levels as well as human health risk assessment of treated and untreated produced water were also determined to ascertain the level of environmental safety vis-à-vis effects of treatment, in order to identify potential environmental concerns from existing treatment practices. Microbial density and concentration of eight heavy metals in produced water samples were assessed following standard procedures and different indices were used to assess the health risk.Concentration (in mg/L) of iron was 6.9 (untreated) and 0.001 (treated wastewater), arsenic 0.001 for both untreated and treated wastewater, zinc (0.002 for both untreated and treated wastewater), mercury (0.001 for both untreated and treated wastewater), chromium (0.001 for both untreated and treated wastewater), cadmium (1.1 for untreated and 0.001 for treated wastewater), lead (0.9 for untreated and 0.001 for treated wastewater) and nickel (0.005 for both untreated and treated wastewater). Further, statistical analysis showed correlation between physicochemical parameters of untreated and treated wastewater as well as heavy metal concentrations. Health risk assessment showed major potential non-carcinogenic risk was via ingestion, with led as the main contributor. Overall non-carcinogenic risk evaluation of produced water showed that humans are not susceptible. Similarly, chromium was the major contributor to the carcinogenic health risk but values for lethal average daily doses and cumulative carcinogenic risk were within permissible limits.