Impact of Raw Water Ammonia on the Surface Water Treatment Processes and Its Removal by Nitrification

In Dhaka City, Dhaka Water Supply and Sewerage Authority (DWASA) supply drinking water and provides sanitation services since 1963 to the city dwellers. About 10 million people depend on the supply of drinking water and sanitation services provided by DWASA. At present DWASA is dependent more on the surface water than the under ground water because of over extraction of ground water2. Every year 2-3 m water level is going down. In this context, Saidabad Water Treatment Plant (SWTP) was established with the capacity of 225 MLD and went into operation on July 27, 2002. The Sitalakheya River near Dhaka city is the source of raw water for the SWTP (Figure 1). Different treatment processes like pre-chlorination, coagulation, filtration, disinfection, pH correction are used at SWTP to make the water potable as well as wholesome to the consumers. Ammonia is one of the important constituents of domestic wastewater and concentrations commonly range from 10 to 50 mg total ammonia-N/l, but might be as high as 200 mg total ammoniaN/l in domestic wastewater in arid and semiarid countries or industrial wastewater3. The condition of water in the peripheral river systems of Dhaka City like Balu-Lakheya River system, Dhaleswari-Kaliganga River system and Bangshi-TuragBuriganga River system has created great concern due to their massive deterioration in quality because of insidious pollution Impact of Raw Water Ammonia on the Surface Water Treatment Processes and Its Removal by Nitrification