I write regarding the March 9 article “Septic, Sewer, or Something Else?” which stated, “Additionally, conventional septic systems do not remove nitrogen…”

I am an environmental scientist and specialize in onsite wastewater treatment systems; this statement is incorrect. Numerous scientific studies have concluded that conventional septic systems, when installed properly, on average, remove 25- to 30 percent of the total nitrogen. Advanced onsite wastewater treatment systems have been shown to remove 25– to more than 60 percent of total nitrogen.

The Environmental Protection Agency is currently sponsoring research on passive nitrogen removal systems that appear to be removing 50- to 90 percent of total nitrogen. These systems utilize wood-based carbon sources and require no more maintenance than a conventional septic system. This is a promising technology and something that the Madison Water Pollution Control Authority should follow.

David Potts

Killingworth