I tested a water sample after collecting it from a wastewater treatment plant. The WWTP disinfects the water by using UV and then reaerates the samples. After that, they discharged the treated samples to the river. The collected sample is UV treated but not reaerated. I have got 2.2 mg/L ammonia-N in this sample. I think this is pretty much higher. I am planning to make potable reuse of this water. So what will be the probable causes for the presence of ammonia-N in this water? And also what are the effects of humans on the presence of ammonia-N in water? Thanks in advance.
U cannot complete remove contaminants i.e during treatment bet can achieve 99% removal efficiency. 1% of nitrate present in the treated water can regrow, bacteria can act on the 1% contaminants and cause ammonia to increase by virtue of the oxidation process. There are potential no major effect of ammonia in water except for it effect on the skin. Bet its largely dependent on the concentrations in ppm.
The UV disinfection is killing the bacteria in the wastewater, so that when it is aerated there is no or low capacity for converting the ammonia to nitrate. Try reversing the order. And then be prepared to address the nitrate which may require a facultative anaerobic digestion, which requires waiting a while after turning off the aeration before using the disinfection. Evaluate how long it will require to remove the nitrate and nitrite (especially for potable use) before completing with disinfection.
Good luck. Please report back with results and or questions.
ammonia is normally converted to nitrate by bacteria. Ammonia-nitrate is not harmful but can be used as an explosive as was observed in Lebanon. It is absorbed by the skin.
Ammonia levels of 2 mg/L is not a toxicity problem for potable water. However
As in the answer from Mr. Anderson, 2ppm of Ammonia-N is not too high for the effluent standard but it is excess the standard. Since Organic-Nitrogen in WWTP goes through biodegrading to NH4+ - Nitrite -Nitrate and the final product ideally be Nitrogen gas escaping to the air. But most of the time it's not the case due to pH and bioreaction conditions it will go back from nitrate to Ammonia. You might consider to add an aftertreatment process like Electrocoagulation to remove it then.
If the Ammonia is not removed it will 1) create a disinfection demand within the water treatment plant and 2) within the distribution system it will feed nitrifying bacteria that will convert it to Nitrate/Nitrite and the bacteria will lower the disinfectant and alkalinity within the water mains, in the process.
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