pH-Independent Measurement of Hydrogen Sulfide in Liquids

H2S and ions in water (animation)

You’ve been measuring H2S in Water the Wrong Way

Measuring hydrogen sulfide concentration in a pH-volatile liquid (such as water) is much more difficult than in a medium like natural gas. As the pH increases, the H2S dissociates into its ions HS (bisulfide) and S2- (sulfide), which are not measured by a typical H2S sensor. A reading that doesn’t account for the presence of these other ionic forms is meaningless at high pH because it would grossly understate the total H2S loading of the fluid when the pH drops. Continue reading “pH-Independent Measurement of Hydrogen Sulfide in Liquids”

Why Measure Chromium Concentration in Liquids?


Hexavalent Chromium Contamination

In 1952, Pacific Gas & Electric (PG&E) started adding hexavalent chromium (Cr6+) to cooling water in order to suppress rust in a Hinkley, California compressor station. The toxic metal was stored in unlined pools, allowed to percolate into the ground and contaminate the water supply. Unexplained illnesses (including respiratory cancer and organ damage) in the town sparked an investigation (as dramatized in the film Erin Brockovich), ultimately resulting in a blockbuster settlement of $333M in 1996.

The Cr6+ levels in Hinkley groundwater were reported at 0.58 ppm in 1993, high above the 0.1 ppm legal limit of the time; due to widespread violations exposed since the Hinkley case, some states are planning to implement Cr6+limits as low as 0.06 ppb. A 2010 study found that 21 US cities suffered from chromium-contaminated groundwater. There is currently no enforced contamination limit for Cr6+ in drinking water, but legislation for this purpose is in progress. Continue reading “Why Measure Chromium Concentration in Liquids?”

Why Measure Bisphenol A Continuously in Effluent Water?

BPA analysis in water

The BPA Controversy, In Brief

The international fight over banning Bisphenol A from use in consumer products has now spanned decades with no sign of either side backing down. BPA is known to mimic estrogen in the human body, but the strength of its effects and the levels of real exposure are heavily disputed. Studies have variably linked BPA to male infertility, breast cancer, and behavioral disorders, fueling concern among the scientific community and wary shoppers alike.

However, BPA is quite entrenched as industry’s chemical of choice for strengthening polycarbonate plastics and producing resins—4.6 million tons of it were manufactured globally in 2012, a figure that will only rise with demand from emerging markets. While some regulatory legislation has been successful, particularly in banning BPA-constructed baby bottles due to infants’ heightened susceptibility to low-dose effects, we still live in a world that will likely continue producing BPA on a massive scale for decades to come. The question, then, is what can we do to effectively mitigate exposure in our communities? Continue reading “Why Measure Bisphenol A Continuously in Effluent Water?”