Physical parameters of water sources
In this study, the parameters included pH, turbidity and temperature that may indicate changes in water quality. A pH meter was used to measure pH of collected samples in the field. The results showed a mean range from 7.4 to 7.8 for all sources (Table 3), which indicated that the water sources were neutral.
Turbidity is a standard measurement in water sampling where suspended sediment plays an important role and may be useful for estimating E. coli in water particularly for lake water and reservoirs. In Sudan, turbidity of waters can be caused by air molecules where the air is dusty. Turbidity was observed to be 5500 NTU and 45.4 NTU for river and irrigation canal water, respectively (Table 3). These high measurements may indicate the presence of pathogenic microorganisms in these water sources.
Temperature is reported to influence the rate of chemical reactions. The mean values for temperatures ranged from 23.6 to 28.2 °C for all samples collected. The temperature of cooler containers was seen as 23.6 °C. High temperature of 28.2 °C in bottled water can be explained by the fact that the data were taken at midday when temperatures are usually very high in Sudan.
Water quality of sources
The results showed that 69% of samples collected (84/122) were safe, 14% intermediate (17/122), 6% in high risk (7/122), and 12% unsafe (14/122) water (Table 4). Water sources contained E. coli bacteria with variable degrees. River and irrigation canals water were completely unsafe for consumption. The reason might be that these sources are open and exposed to pollutants. Zamxaka et al. (2004) found that more turbid sources are the most microbiologically contaminated. The results showed an association between high turbidity in rivers and irrigation canals and the presence of E. coli. Water quality might vary rapidly, due to the rainfall that can greatly increase the levels of microbial contamination in open sources. Hunter (2003) found that waterborne outbreaks often occur following rainfall.
This result is in line with Valipour (2014) who stated that the increase in irrigation systems has adverse impacts on quality of water resources. Some farmer communities living inside the Gezira irrigation scheme area used canal water for drinking and washing. Boelee et al. (2007) confirmed that in irrigation systems all over the world, water is not only used for the irrigation of agricultural crops, but for a whole range of domestic and other purposes as well. Most of the industrial cities (Wad Medani industrial area) and sugar factories around the study area (Sennar sugar factory) discharge their waste into the river which could have serious adverse health effects on the communities using water for domestic purposes.
A total of 65% of household water taps, 75% of yard taps and 59% of communal taps were safe. Taps normally takes water either from treatment plants through the network distribution of boreholes. The water treatment plant was found to be 100% E. coli free, and 82% of the boreholes contained safe water. Boreholes indicated safe groundwater. This result did not agree with results published by Ell-Amin et al. (2010) which indicated that Wad Medani groundwater was highly contaminated. This research was conducted in the Wad Medani locality, while Amira’s work included the Managil locality which is known for polluted water. A study carried out by Engström et al. (2015) in Juba indicated that an important contamination mechanism was fecal pollution of the contributing groundwater, which was probably due to the presence of latrines. Groundwater aquifers in these areas are not rich and communities depend mainly on surface water, which is liable to contamination. Elevated tanks are found either in households or in public schools and are well controlled and routinely checked, and it could therefore account that 64% tanks were containing safe water (Table 4).
Risk category according to urban, peri-urban and rural areas
In this study, urban population are those living within the Wad Medani city, while the peri-urban communities are those living around the city and rural communities are living in villages away from the city where most of them practice agriculture. Table 5 shows the quality of water sources in urban, peri-urban and rural areas of the study area.
Generally, water sources in urban area are safe particularly treatment plant and bottled water (vendor water) (Table 5). There was, however, tap water which was classified as unsafe for drinking water in the urban area. The river water was totally unfit for drinking water as was one water cooler. Boreholes were found in all areas and generally safe except for 3 boreholes in the rural communities. Water tanks in rural areas were 54.5% safe. Canal water is extended through peri-urban and rural areas. The majority of the rural people are cultivators (Musa et al. 1999) with fields irrigated by water drawn from the canals which is unsafe. The canal water was 33.3% high risk in peri-urban and 66.7% unsafe in rural area. The result shows that the highest level of contamination of water sources (high risk and unsafe) was observed in rural area (9.1%) followed by urban (5.7%), and peri-urban (1.6%).