AWWA Water Science Author Spotlight: Anushka Mishrra

Abstract

Having recently published an article in AWWA Water Science, Anushka Mishrra answered questions from the publication's editor-in-chief, Kenneth L. Mercer, about the research.

Uptake of Silicate by Pipe Scale Materials and Effects on Lead Release

Anushka Mishrra, Ziqi Wang, and Daniel E. Giammar

Anushka Mishrra at work in the laboratory at the University of California, Berkeley.

I earned an undergraduate degree in chemical engineering. I then pursued a PhD in energy, environmental, and chemical engineering, where my research focused on legacy contaminants in drinking water supply and distribution systems. Currently, in my postdoctoral work, I am developing water treatment technologies to remove toxic hexavalent chromium from drinking water sources, which allows me to apply my expertise toward improving water quality and environmental health.

Pausing during a hike up Mount Diablo in Northern California.

During my PhD work, I studied the effect of sodium silicate, a type of corrosion inhibitor, on lead release from lead service lines and observed that it can significantly reduce lead to very low concentrations. In our AWWA Water Science article, we investigated the mechanism behind this corrosion control path using sodium silicate. Specifically, we aimed to understand whether sodium silicate chemically reacted with lead-based solids formed in the pipe or if it created a physical barrier to prevent lead from releasing into the water.

To understand the interactions between silica, lead-based corrosion products, we used a unique approach: Rather than simply collecting water samples from lead pipes, we removed solids from the interior of actual lead pipes and suspended them in water for our experiments. This method allowed us to study lead release under controlled conditions, offering a fresh perspective beyond typical field or laboratory setups. We applied surface characterization techniques to examine the interactions and structural changes on the pipe material, gaining insights into how the corrosion inhibitor affects lead release.

I was initially apprehensive about investigating the mechanism by suspending real lead pipe scales or corrosion products, aiming to eliminate the diffusion-limited transport typically present within the pipe. To my surprise, we did not observe any specific chemical interactions between silica and lead that would indicate a decrease in lead solubility. This unexpected result revealed that silica's role in corrosion control is achieved primarily by inhibiting the diffusion of lead from the corrosion products in the lead service lines.

Our research has highlighted silica's role in reducing lead release, along with insights into its inhibition mechanism. This opens up opportunities to investigate whether this phenomenon is specific to lead service lines with a thick layer of corrosion products inside the pipe. Additionally, it would be valuable to identify the specific characteristics of these corrosion products that enable sodium silicate to function effectively as a corrosion inhibitor.

I’m constantly learning while advancing research to develop next-generation technologies for a sustainable and resilient water supply. It's incredibly motivating to know that my efforts can lead to safer drinking water and healthier communities.

To learn more about Anushka's research, visit the article, available online at https://doi.org/10.1002/aws2.1364.