Question

a. I) describe how microorganisms transform nitrogen during wastewater treatment ii? give examples of the microorganism(species, functional groups) involved in nitrogen transformation reaction

Answer 1

Nitrogen is present in many forms in the septic system. Most nitrogen excreted by humans is in the form of organic nitrogen (dead cell material, proteins, amino acids) and urea. After entering the septic tank, this organic nitrogen is broken down fairly rapidly and completely to ammonia, NH3, by microorganisms in the septic tank. Ammonia is the primary form of nitrogen leaving the septic tank. In the presence of oxygen, bacteria will break ammonia down to nitrate, NO3. In a conventional septic system with a well aerated leaching facility, it is likely that most ammonia is broken down to nitrate beneath the leaching field.

Nitrate can have serious health effects when it enters drinking water wells and is consumed. Nitrate and other forms of nitrogen can also have deleterious effects on the environment, especially in coastal areas where excess nitrogen stimulates the process known as eutrophication. For this reason, many alternative technologies have been designed to remove total nitrogen from wastewater. These technologies use bacteria to convert ammonia and nitrate to gaseous nitrogen, N2. In this form nitrogen is inert and is released to the air.

Biological conversion of ammonia to nitrogen gas is a two step process. Ammonia must first be oxidized to nitrate; nitrate is then reduced to nitrogen gas. These reactions require different environments and are often carried out in separate areas in the wastewater treatment system.

Bacteria used for above processes are :-

Nitrosomonas

Nitrobacter