08 December 2016

Oily water does not make for good salads!

BB sent me this report ("Hazard Assessment of Chemical Additives Used in Oil Fields that Reuse Produced Water for Agricultural Irrigation, Livestock Watering, and Groundwater Recharge in The San Joaquin Valley of California: Preliminary Results" [pdf]), to whose authors I sent the following questions:
Do I read your report correctly, that you are merely enumerating the chemicals but NOT measuring their concentrations?  And am I right to assume that produced water use/discharge is occurring WITHOUT any purification treatment? Or is there some treatment that’s not detailed?
Seth B.C. Shonkoff, PhD, MPH replied with:
You are correct that we did not evaluate concentrations of these chemical additives in the produced water. The first step that we undertook in this hazard analysis was to compare the recently reported chemical constituents to toxicity, priority pollutant, and other databases to identify what should be monitored for and then how. To date the only chemical constituents monitored for were naturally occurring constituents (e.g., boron, arsenic, heavy metals) as well as some others less frequently (annually or every 5 years). This is the first assessment of chemical ADDITIVES used during oil and gas production in fields that are reusing their water for these purposes.

There is very limited treatment prior to irrigation, groundwater recharge and livestock watering. The produced water undergoes oil-water separation and then is run through walnut shells prior to application. Depending upon water availability from other sources it is mixed with between 20% to 50% other water sources prior to application.
In other words (my summary), scientists are merely identifying which chemical additives and related byproducts may be present in the Central-Valley-oil-field wastewater now used for irrigation. The concentrations and impacts of those chemicals are yet to be understood.

Bottom Line Higher water scarcity results in greater use of sources that are farther, dirtier and potentially more harmful to public health and the environment. Policies dating from an age of abundance may not consider the costs of those sources to health or the environment. They need to be updated.

H/T to BB


  1. I am familiar with the water produced in the Mt. Poso oil field in eastern Kern County, much of which is delivered to irrigators. The oil there is quite shallow (generally less than 2,000 feet), and very viscous (14 API or so). A typical well produces 98% water and 2% oil. The water Iies under the oil, of course. Beneath that is solid granite. When the oil is pumped, it is a mixture of oil and water, which are separated by settling in tanks. The remaining water is then treated (here, I am not sure with what, but it is not just walnut shells). It is regularly tested by the State before delivery to water districts.
    For years, the produced water was used to water livestock, with no ill effects. Because it is the naturally filtered consequence of Sierra snowmelt, it is very pure. Oil field workers sometimes drink it.
    There is no good reason for people to be scared that this water is being used to grow crops. There is no evidence of food contamination.

    1. @Kurtz -- thanks for the reply. Would you agree that it would be good to test that water, to see if it's polluted? Also, would you agree that other produced/irrigation water might be polluted? That's what the paper is calling for.

  2. Sure, that water should be, and is, tested, both by the state and the irrigation district. No irrigation district wants to distribute polluted water. Tests on produce grown with this water have shown no dangerous accumulation of pollutants.
    Water from shallow wells producing in sandy soils on the east side of Kern County is completely different from wastewater produced in other regions. The vast majority of oil wastewater is found at greater depths, and in areas with more recent (geologically) marine sediments. This stuff is truly nasty, but it can have value when pumped back into the producing formation to drive more oil towards the wellbores. In fact, water not from the oil reservoir often can not be used for this purpose, because of its different chemical makeup. Potable water would never be used for this purpose. There is a lot of nonsense out there about how much water is used in oil production; most of it is this otherwise useless water, or water used to generate steam in a closed system, with comparatively small losses. Wastewater not used for oil recovery must be by law disposed of into isolated strata a mile or more beneath any potable aquifer.


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