Water quality parameters comparison

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Hi All

The WHO defines, "Petroleum products" as Petroleum products are used in large quantities, primarily as fuels. They are complex mixtures of chemicals derived from crude oil by distillation and fractionation. They consist primarily of a wide range of aliphatic and aromatic hydrocarbons, many of which are of extremely low solubility in water. Petroleum products are widely stored and handled and are often spilt. The primary concern for drinking-water is the potential for spills into source water, penetration of distribution systems and contamination of drinking-water treatment works.

I am confused with a similar term, "Dissolved Hydrocarbons" which I came across a water project recently.  The potable water quality of the project in question described "Dissolved Hydrocarbons" with a guaranteed level of < 0.01 mg/L, with a rider that, " The taste and smell threshold value varies widely according to product and it is 0.0005 ppm (mg/L) for hydrocarbons and distillate "

My questions to all are as follows:-

Taxonomy

5 Answers

  1. Hi Anvar,

    Petroleum ​Products and ​Dissolved ​Hydrocarbons - ​can these 2 ​terms be taken ​same.  ​This is to ​check ​compliance with ​WHO
    I would say no. Petroleum products covers a very wide range of compounds, both water soluble and insoluble. Dissolved Hydrocarbons would be a subset of Petroleum Products (only those compounds that are water soluble). The 'Guidelines for drinking-water quality: fourth edition incorporating the first
    addendum'     provides the following comment on Petroleum Products:

    So there is no guideline value for Petroleum Products in this reference. I was unable to any reference to Dissolved Hydrocarbons in this document. Could you let me know which reference you obtained the value for Dissolved Hydrocarbons from?


    If both are ​different, then ​how do we deal ​with the ​distillate & ​hydrocarbons as ​stated in the ​rider. ​Based on the above I think that you could focus on the 'Dissolved Hydrocarbons'. Dissolved Hydrocarbons are likely to be smaller hydrocarbons, including TPH, BTEXN and PAH compounds. The solubility/miscibility of hydrocarbons in water reduces sharply as the number of carbons in the molecule increases.

    There is a good paper which shows this:

    https://www.nrcresearchpress.com/doi/pdfplus/10.1139/v73-599

    I think that if you had  process in place to remove bulk organics (Petroleum Products) and possibly a separate removal process specifically to remove Dissolved Hydrocarbons you would meet the WHO requirement.

    In addition you should be monitoring your product water for TRH(C1-C10), BTEXN and PAH suites. These are standard analytical suites that most laboratories should provide.

    Of course this should be subject to a proper risk assessment (I don't know what the composition of your feed water is or what you plan to do with it).


    Are dissolved ​hydrocarbons, ​as a parameter ​more stringent ​than the WHO ​defined ​Petroleum ​Products ​

    It would seem so. There appears to be no guideline value for Petroleum Products in the ' Guidelines for drinking-water quality: fourth edition incorporating the first addendum'. 

    While there also appears to be no specific guideline value (that I could find) for Dissolved Hydrocarbons there are guideline values for the various compounds that would make up Dissolved Hydrocarbons.

  2. Hi Anvar,

    I develop porous mineral grains for deep bed media filters for removal of petroleum from water, and understand that:

    Water can contain free hydrocarbons that float to the surface, dispersed hydrocarbons that remain in suspension as very fine droplets and dissolved hydrocarbons, which are short-chained and relatively low-weight molecules in which a polar part plays a relatively strong role in binding to water molecules. They are all petroleum products that need to be removed for reaching drinking water quality, whereby the dissolved hydrocarbons are the bigger nuisance, and some are even carcinogenic and should have very low limit concentrations. Thus, not all petroleum products in water are dissolved hydrocarbons, and both terms might not be taken as the same.

    I understand that the WHO follows the approach used by the TPHCWG. To make the problem more manageable they divided Total Petroleum Hydrocarbons into a series of fractions based on the number of carbon atoms in conjunction with general structure.

    As concerns the EC6–EC8 aromatic fraction, they say: “Drinking-water guidelines have been developed for the two compounds in this range that are found in petroleum products: benzene (10 µg/liter) and toluene (700 µg/liter). Toluene has a very low reported odor threshold in water and may be detected by odor at concentrations below the guideline value” and “it is of particular importance that these values should only be used in conjunction with sensory assessment for taste and odor, which will, in most cases, be detectable at concentrations below those concentrations of concern for health, particularly with short-term exposure”. Finally, they say: “In some cases, the only method available is the measurement of total hydrocarbons. This is less satisfactory, but by using the lowest drinking-water value, it would provide a conservative assessment.”

    The text from the rider "The taste and smell threshold value varies widely according to product and it is 0.0005 ppm (mg/L) for hydrocarbons and distillate" is confusing. Note that a similar value is mentioned as the very low detection limit of 0.5 µg/liter in water in measurement method EPA 5030B for aromatic volatile aromatics, using gas chromatography with a photoionization detector, specifically for these more volatile aromatic components (US EPA, 1997a, 1997b).

    So, are dissolved hydrocarbons, as a parameter more stringent than the WHO defined Petroleum Products?

    As I understand, first comes odor and taste, if there are carcinogenic compounds like benzene, you need to take into account total water consumption, and if you have not the instruments to measure these, then the concentration of Petroleum Products, as a precaution, may not exceed the stringent limit for the dissolved hydrocarbon, such as benzene.

    https://www.who.int/water_sanitation_health/dwq/chemicals/Petroleum%20Productsrev071105.pdf

    Regards,

    Hans

  3. Our products using enhanced microbial action stimulated by a fully organic, biodegradable solution will remove petroleum/hydro carbon from polluted water.

    WWW.BIOPHYSICS-RESEARCH.NET

    1 Comment

  4. Why in the world the WHO would set parameters for industrial hydrocarbons I will never understand.  Health ok remediation not ok. The question is quite valid. W H O has tried to  make it difficult to take an easy cleanup project and blow it up to larger than life. ALL hydrocarbons at every level of distillation are easily bioremediated using the Archaea species of microbes.  W H O in a nut shell: 23 odds and ends setting on a table, 22 fall off, what do you have left, an odd or an end.  Good luck