By product of oil and gas extraction, OPW is considered as an alternative to irrigate the fields during the drought season in the Cawelo district. This has raised the suspicions amongst the environmentalists, who worry about the fields and crops being enriched in salt and boron. Even though these elements are found in abundance in diluted OPW, their concentrations are still regarded as safe for consumption.
A recent study conducted by researchers from Duke University has regarded the use of diluted OPW completely safe for the fields and the crop. Avner Vengosh, who is one of the authors of the study, said that they did not find any traces of harmful metals and radioactivity in their sample of crops.
Even if boron and salts start accumulating in the soil beyond safe levels, farmers can always opt for a boron-resistant crop. Mixing OPW with more proportion of freshwater can also reduce the chances of harmful elements concentrating within the soil and the crop. This recent study can help dissipate fears regarding the use of OPW in the fields. Using diluted OPW to water the fields can prove to be the most efficient usage of resources, leaving more groundwater supply for drinking purposes.
However, the soil that was tested was from the fields that utilized OPW from certain oilfields, and the composition of OPW varies from the oilfield to oilfield. This means that results produced from the research are not generic, and can only be applied to the fields from which the samples were taken. To determine how safe OPW is for irrigating a particular field will require a sample from that specific field.
Andrew J Kondash et al, The impact of using low-saline oilfield produced water for irrigation on water and soil quality in California, Science of The Total Environment (2020). DOI: 10.1016/j.scitotenv.2020.139392