) but the highest value was recorded at Maddallah site (S1) of the River Al-Zab during April of the year (Table 3).

The present study generally also showed that turbity was higher during cold months compared to hot seasons. Turbidity was higher in Al-zab (46.3 NTU) compared to Tigris which was almost 40 NTU. The turbidity mean of both waters was more than 35 NTU.

3.4. Biological Oxygen Demand (BOD)

The biological oxygen demand of all water samples studied ranged between 0.7 to 4.4 mg/l (Table 4).

The lowest value of BOD was recorded at Al-Shag site (S2) during August (0.7 mg/l) and at University site (S5)

during July (0.7 mg/l) and both stations were located on River Tigris. The BOD value (4.4 mg/l) was seen in Abo-Dalaf site (S8) during February. The analysis of variance showed a significant difference between BOD values recorded at different months and the P value was less than 0.5.

3.5. Total Viable Counts (TVC,s)

It was shown that the lowest number of heterotrophic bacteria i.e. TVC was isolated from the sample collected from Tikrit Bridge site on River Tigris at February (Table 5) and the value was 11 × 10/ml. The highest viable counts of bacteria was isolated from the water of AboDalaf (S8) on River Tigris during February and the value was 324 × 10/ml. The highest value of recorded at Maddallah area(S1) during January when the bacterial number was 223 × 10/ml. The heterotrophs were higher in number in River Tigris compared to Al-Zab River waters (Table 5). Cold months showed higher numbers of bacteria isolated. Statistical analysis did not show significance and the P value was more than 0.5 3.6. Total coliforms (TC,s): The present study showed a lowest number of total coliforms to be estimated at University site (S5) particularly during January, February and March and the values were 95.80 and 35/100 ml respectively (Table 6). Total coliforms were very low in number at Maddallah site on River Al-Zab at February (130/100 ml) but this number was highly elevated at the same station during

Table 3. Turbidity (NTU) of the water samples tested.

Table 4. Biological oxygen demand (BOD) mg/l at the water sample sites.

September (1600/100 ml). Total colifrms was generally higher in summer months in all water sites studied but the statistical analysis showed no significant differences and the P value was more than 0.5.

3.7. Fecal Coliforms (FC,s)

The most probable numbers (MPN,s) of fecal coliforms isolated at 44˚C were varied from site to site and from month to month (Table 7). The lowest number was recorded at Maddallah site (S1) on River Al-Zab in February which was 2/100 ml. Maddallah water site showed the highest number of fecal coliforms which was 1600/100 ml at April, June and July. Sites on River Tigris showed different degree of fecal coliforms presence, e.g. the MPN at Tikrit Bridge (S6) was 70 at January and 900 at August. The highest MPN in River Tigris sits was 1800 at Al-Mazraa and Abo-Dalaf sites (S4 and S8). Cold months showed higher fecal coliforms to be harversed. The statistical analysis of the data concerned showed a significant difference between sites of waters (P value was less than 0.5) but no significant difference was concluded according to months of collection (P values more than 0.5).

Table 5. Total viable counts (TVC,s × 10/ml)of bacteria isolated from water sample.

Table 6. The most probable numbers (MPN,s) of total coliforms isolated from water samples.

Table 7. The most probable numbers (MPN,s/100 ml) of fecal coliforms isolated from the water samples.

4. Discussion

All water bodies particularly the fresh is usually under environmental pressures leading to pollution of such vital human sources for human consumption. These pressures composed of chemical, physical and biological factors. Moreover, rapid human growth with various activities particularly in urban areas plays a major role in water contamination which consequently makes the situation more worse. Domestic and industrial wastes outfulls causing a serious damage to human habitat and finally leading to various diseases as well as shortage in suitable water sources applicable for human consumption and other uses needed by mankinds [2]. River Tigris is usually under pressure of these environmental factors which cause its pollution [3]. The Lower Al-Zab River is less affected by the mentioned factors due its geographical site that is almost relatively away from the civilian impact. Moreover, Al-Zab River is 110 kilometers in length starting from Dokan Dam and ending at its junction with River Tigris at Al-Shag in Al-Hawija.

Water temperature considered one of the vital factor for water habitat as it affects the dissolving of salts and gases especially oxygen and carbon dioxide [15]. Air temperature in Iraq is extreme which is highly elevated in summer exceeding 50˚C but during winter might decreased to be less than –10˚C. This thermal stress will obviously affects funa and flora that associated in life with water bodies and their sources. Furthermore, present study showed that the water temperature ranged from 0.9 to 26˚C. On the other hand, the present study revealed a high turbidity of the water of both River Tigris and River Al-Zab during April particularly at the Maddallah area on Al-Zab which was 81.03 NTU while the highest turbidity was seen at Al-Oja site on River Tigris during August (18.04 NTU). The rainfalls as well as river floods are the main causes of increased water turbidity during spring season in Iraq. This situation will increase the risk of water pollution as the rainfalls will clean out all pollutants towards the rivers. This is one of the major causes of increased numbers and types of bacterial indicators in water bodies [1,7].

Electrical conductivity can be define as the ability of water to conduct the electric current and this character depends on the concentration of water ions contents and water temperature [15,16]. In the present study, it was concluded that highest electrical conductivity was seen at Maddallah station on River Al-Zab in June but the lowest conductivity was recorded at Al-Mazraa station on River Tigris in February. Almost similar observations have been noticed by Al-Shwany [12]. This might be due to decreased amount and speed of Al-Zab water during summer in the last years along with increased domestic wastes nearby the river as large numbers of villages allocated on both sides of the river. In addition, River Al-Zab sourrounded by the most famous and important agricultural areas.

Biological oxygen demand (BOD) can be used for evaluation of the level of pollution due to domestic as well as industrial wastes mixed with water bodies. This variable is very important in self purification of water sources like rivers and lakes [17].

The present study revealed a range of BOD between 0.7 to 4.4 mg/litre (Table 4). The lowest value of BOD was recorded at University station (S5) during July whereas the highest value was seen at Abo-Dalaf site south of Tikrit city at February. This mean that water quality at Abo-Dalaf station is risky for human consumption and other uses [18]. The present study showed that the average value of BOD of River Al-Zab was 2.4 mg/l which is almost less than that found elsewhere [19]. However, the overall mean of BOD was 2.4 mg/l which is suitable for human consumption after drinking water purification process with reference to European characterizations 74/464/ EEC of waters used as sources for drinking waters [20].

The present study revealed variable total viable counts of heterotrophic bacteria with respect to different sites and months of collection; These values ranged between 11 to 324 × 10 cells/ml (Table 5). The highest numbers were isolated during January, February and March i.e. during cold weather whereas the lowest number was seen during September which is hot. Other workers concluded almost the same fluctuation of total viable counts in Iraqi rivers [12,21]. Cold weather as well as availability of organic matter are playing major roles in survival and presence of heterotrophic bacteria [7]. Furthermore, total coliforms is considered as an indicator for long-term water pollution [1]. The present study showed that the total coliforms were different according to sites of collection and the highest number was recorded in July which was almost 1023/100 ml (Table 6).The lowest most probable number of total coliforms was estimated during March (395/100ml). Hot months are associated with increased total coliforms and that may be due to decreased water bodies in rivers as well as the increased human activities in and/or around rivers which increased the pollution impact on these water bodies [21]. On the other hand, the most probable number of fecal coliforms isolated at 44˚C was considered as an indicator for recent microbial pollution [1,7]. The present study revealed a highest number during February (727.1/100 ml; Table 7) and the lowest number was seen during September (290.6/100 ml). However, Escherichia coli was the dominant bacteria among the fecal coliforms isolated in this locality. Maddallah site on Al-Zab showed 2 cells/100ml during February and this number is a strong indication that Al-Zab River waters under fluctuated sources of domestic pollution due to variability in dilution factor with a changable amount of waters released from Dokan Dam during the last yeasr. Moreover, the water flow of the River Al-Zab is very speedy due to its high slope compared to River Tigris and this is definitely affects the survival and number of bacteria in waters under study. However, the statistical analyses showed significant differences between the most probable numbers estimated at different localities during various months of study (P values were less than 0.5) using analysis of variance programme, Dancan test and t-test. It was concluded from the present study that Iraqi rivers as the main source of fresh waters for human consumption are under risk of shortage particularly of Al-Zab River as well as under severe impact of environmental pollution and chemical, physical and biological parameters. Moreover, the series of wars occurred in this country might increased the risk of water contamination that leads to public health hazards particularly the infectious diseases, cancers and genetic drifts. Finally, further investigations are disperatly needed to explore the various changes that might occurred in this locality.

5. Conclusion

The present study concludes that several physical, chemical and biological parameters of Tigris and Al-Zab rivers water (temperature, turbidity, electrical conductiveity, biological oxygen demand and bacterial indicators) vary depending on river, site and time of collection, the statistical analyses showed significant differences between the most probable numbers estimated at different localities during various months of study (P values were less than 0.5) using analysis of variance programme, Dancan test and t-test. It was concluded from the present study that Iraqi rivers as the main source of fresh waters for human consumption are under risk of shortage particularly of Al-Zab River as well as under severe impact of environmental pollution and chemical, physical and biological parameters. The most probable numbers (MPN,s) of fecal coliforms isolated at 44˚C were varied from site to site and from month to month (Table 7).The lowest number was recorded at Maddallah site (S1) on River Al-Zab in February which was 2/100 ml which was within the permissible limits of WHO for human consumption. The present study showed that the elcctrical conductivity of waters under investigation were varied and ranged between 230 to 678 ms/cm. The lowest value was recorded at Al-Mazraa site (S4) during January while the highest value was recorded at Maddallah site (S1) during June which was 675 ms/cm and this might be due to shortage of water supply from Dokan dam at this time of the year.

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