The following is an interview with Devon Smith, P.E., of Underwood Engineers, a civil environmental consulting firm, about his experience with the ResidualHQ Automated Disinfectant Control System.

Can you give us a quick overview how the project started, and the organizations involved?

When we started up the Southern New Hampshire Regional Water project, evidence indicated nitrification was occurring in the system. A task force was formed that included the State, Underwood Engineers, Ph.D.s and professors from the University of New Hampshire, the Town of Derry and key water system operators and other consulting firms. We workshopped together how we wanted to address the nitrification situation.

Jim Malley of UNH found a case in New England that was similar to our problem. A water district had built a tremendous amount of water tanks to add fire suppression and as a result had too much storage, which had an adverse impact on water quality. They found that by adding chlorine to storage tanks they could help mitigate nitrification by satisfying nitrite’s chlorine demand and also re-form monochloramine with any excess free ammonia. During a significant nitrification event the monochloramine can deplete quickly leaving just free ammonia, again which can cause the problem to cascade. Through their work they founded the “do no harm approach” where only chlorine is added versus chlorine and ammonia.

Download the pdf below to read the full interview and learn more the ResidualHQ system.