Hi Anvar, I develop porous ...

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