Nitrate pollution of Neogene alluvium aquifer in Morogoro municipality, Tanzania

Abstract

Concern over nitrate pollution of groundwater in integrated water quality management has been growing recently. The levels of nitrate in wells from septic tanks and urban agriculture with nitrogen fertilizers application may increase the potential groundwater pollution by nitrate. The purpose of this study was to determine the concentrations and spatial distribution of nitrate (NO 3 −) in groundwater in Morogoro municipality. Groundwater samples were collected from 20 wells during wet season period in March-April 2010 in 6 wards namely Kihonda, Mji Mpya, Mafisa, Saba Saba, Boma and Kilakala. The spectrophotometer was used to measure the NO 3 − concentration in water samples. The minimum and maximum nitrate levels were 1.4 and 32.5 mg/L respectively in the wards studied with an average of 7.76 mg/L. These results showed that all of the groundwater samples have NO 3 − concentration below the Tanzania Bureau of Standards upper limit value and World Health Organization guideline of 75 mg/l and 50 mg/l respectively. Also, the level of nitrate concentration tends to decrease with depth for most of the places due to the anoxic condition that is available at the higher depth which facilitates the utilization of nitrate by anaerobic microorganisms.

Occurrence of nitrate in Tanzanian groundwater aquifers: A review

“…However, due to increasing water demand, poor infrastructures, and deteriorating quality and quantity of river water, surface water supply from Ruvu and Mzinga rivers does not suffice the water requirements for Dar es Salaam City . To supplement surface water, significant number of wells and boreholes has been developed by different organizations and individuals in Dar es Salaam (Mato 2002;Bakari et al 2012;Mjemah et al 2012; and Morogoro (Kibona et al 2011). Spatial distribution of nitrate observed at different time in the groundwater in Dar es Salaam is presented in Fig.…”

“…According to Kibona et al (2011), nitrate concentrations of groundwater within the Morogoro municipality ranged from 1.4 to 32.5 mg/l where wells that are less than 40 m deep had higher values. Almost 25 % of reported wells had nitrate concentration above 10 mg/l.…”