The Importance of Maintaining Wastewater Quality - Guy Forrest-Hay

In the typical wastewater treatment process, the goal of primary, secondary and tertiary effluent treatment is to reduce or remove organic matter, solids, nutrients, disease-causing organisms and other pollutants from the treated wastewater before it is discharged to a body of water. In addition to disinfectants, other chemicals are sometimes added during the treatment process to help settle out or strip out nutrients including phosphorus or nitrogen. Some examples of nutrient removal systems include coagulant addition for phosphorus removal and air stripping for ammonia removal. To ensure efficient operation of any wastewater treatment plant, three different but equally important sets of measurements must be analysed.

1) Parameters essential to cleaning processes: pH as measured at the inlet and DO as measured in the aeration tank

2) Parameters essential to measuring efficiency: BOD and COD as measured at the inlet and in the treated effluent

3) Parameters essential to plant optimization: DO, ammonium, nitrate, nitrite and phosphorous

Ammonia, Nitrogen and Phosphorus

The environmental rationale associated with monitoring nitrogen levels in wastewater treatment is to ensure that nutrient levels are sufficient to allow the optimum population of bacteria to proliferate to break down waste. In tandem with this, there is the fundamental requirement to minimise concentrations of ammonia in the final outfall so that the effluent is fully compliant with environmental discharge standards. Additionally, ammonia monitoring is used to document discharge levels set by regulatory authorities, especially where non-compliance can result in penalties.

For control of a nitrification/denitrification process in a waste water treatment plant, ammonia measurement is a must. Nitrogen is a nutrient which will encourage undesirable, oxygen depleting growth in rivers and lakes, and is poisonous for fish and micro-organisms.