Why Measure Bisphenol A Continuously
in Effluent 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?

Why Measure BPA Online in Effluent Water?

The public debate generally centers on how much BPA leaches out of our food and beverage packaging into our diets. This testing is the realm of research institutes and, while extremely necessary, does not answer the whole question.

We are addressing an entirely separate but critical measurement: continuous analysis of the effluent from BPA production sites (primarily polycarbonate plants) to ensure that the chemical is not leaking into our environment. For these factories, BPA is a valuable raw material and not to be wasted, but real-world processes have upsets and inefficiencies that can translate into a toxic effluent stream. If BPA can enter waterways and ecosystems through this point source origin, then leachate from our bottles and cans is only one piece of the exposure puzzle.

The research on how easily BPA biodegrades in natural waters is contentious. In streams where the microbes are sufficiently acclimated, BPA can have a half-life of a few days to a week. Wastewater treatment plants that accept the BPA-laden effluent depend on acclimated microbes to break down the chemical, where biodegradation up to 90% is expected as a best case. When the concentration of BPA spikes above the threshold that this treatment is designed for, much greater breakthrough can be expected.

How can we be sure that our methods of cleaning up point source BPA waste are working? As usual in our newsletters, the answer is continuous chemical analysis. Measurement of BPA concentration in the effluent of production sites is a critical line of defense against exposure and merits just as much vigilance as the fight against leach-prone consumer products.

The Method

Luckily, Bisphenol A has strong absorbance in the UV region (where water is transparent). Therefore, the concentration of BPA in effluent can easily be monitored by UV spectroscopy.

The OMA Process Analyzer uses a high-resolution UV-Vis spectrophotometer to measure BPA concentration in real time. With a rugged, solid-state design and simple, automated performance, the OMA provides a low-cost solution for implementing the much-needed effluent analysis. Due to the intrinsically wide dynamic range of the technology, the same instrument can monitor low range (0-20 ppm), high range (0-100%), or anything in between with seamless accuracy.

In the specific application of measuring BPA in water, the pH of the stream normally complicates the analysis. Depending on the acidity of the stream, the chemical exists as an acid or a salt, each of which has a unique absorbance spectrum. Less intelligent systems require the operator to adjust the pH with consumables and thus kill the variation. Using powerful multi-component analysis, the OMA simultaneously monitors the absorbance curves of both forms of Bisphenol A. This approach provides a direct, pH-independent analysis with a drastically reduced margin of error.