The action of the micro-organisms on organic and complex inorganic materials, leads to the production of ammonia. When ammonia is present in water at high enough levels, it will have detrimental effects on animal life. For this reasons ammonia in a wastewater plant might be monitored and removed at different points in the process:
Ammonia levels at the intake can change a lot from day to day and from hour to hour. No instrument to date is able to measure ammonia at the raw wastewater inlet (soon after the screens) without an extensive maintenance regime or filtration system. If there was an instrument able to measure ammonia levels soon after the screens operators could:
Today’s paradigm for measuring ammonia at the intake is:
The 3500 Ammonia Monitor is the only instrument in the market that has been specifically designed to monitor the levels of ammonia at the raw wastewater intake. The principle of operation is the measurement of headspace gases from a sample tank containing the waste water to be measured.
The MS3500 works by passing water through a sample tank as shown below. Sodium Hydroxide (NaOH) is added to increase the pH of the waste water, converting NH4+ to Ammonia. Through the use of Henry’s Law the concentration of gases in the headspace is proportional to the concentration of the substance in the water. The Ammonia and other volatiles in the waste water will pass into the headspace above the waste water where it will be trapped. This will continue until equilibrium is reached.
A sample of the headspace gases are then passed across sensors in the MS3500 sensor head which respond to the Ammonia in the headspace but reject other contaminants. This response is then analysed by the instrument and a concentration value is generated based upon the relationship between the concentration present in the headspace and that in the water.
This is from a site in London that serves a population equivalent of more than 1 million people. The test lasted three months and again 24-hours sample sets were obtained. A very good correlation between MS3500 and the lab results was demonstrated. After months of tests the customer is now confident of the solution and of the correlation with his own lab. Three systems will be used to monitor the two inlets of raw wastewater into the WWTP and help the plant to: