Monitoring ammonium/ammonia levels is critical for optimising wastewater treatment processes and for better understanding the impact of raw sewage discharge into surface waters.
Ammonium (NH4+) and ammonia (NH3) are both part of the nitrogen cycle and exist in equilibrium. Typically harmless ammonium is prevalent (>98%) over the more toxic ammonia (<2%), unless under high pH and temperature conditions.
In wastewater treatment plants (WWTPs) ammonium is monitored for process control to ensure optimal nitrification/denitrification aimed at converting any dissolved nitrogen (NH4+, NO2, NO3) ultimately into nitrogen gas (N2↑), leaving typically low levels of dissolved nitrogen in the discharge. If the process is not managed well, nitrous oxide is released, a damaging greenhouse gas.
However, discharge of untreated sewage during Combined Sewer Overflow (CSO) events, alongside agricultural fertiliser and industrial run-off, can result in high levels of ammonium/ammonia causing excessive algae growth and eutrophication in rivers, estuaries and coastal waters, with damaging effect on local aquatic life.
Incoming Environment Act 2021, Section 82 legislation in the UK will require operators to monitor ammonia levels up and down-stream of all WWTPs and CSOs, which equates to >50,000 locations.