By Patrick Higgins
The proper tools are essential to fixing any problem. Over the years, Ohio EPA’s Compliance Assistance Unit (CAU) has helped dozens of water resource recovery facilities (WRRF) get back into and maintain compliance with NPDES discharge permits. Their field toolkit has included an assortment of batch sampling kits and handheld instruments. Each tool had its place but each also had limitations and, as a result, the compliance puzzle often was missing important pieces. Increasingly, as nutrient limits were incorporated into discharge permits, the missing piece was characterizing the dynamics of nitrification and denitrification.