3.2.1. Ions
Although Al was not detected in all raw water supplied to the treatment plants, the treated water of the WTP contained some Al (
Table 7 and
Table 8). This is possibly due to the use of aluminum as a coagulant in the traditional treatment process of the considered plants [
20]. Findings showed that the maximum Al values were detected for the Abu Al Khaseeb plant, showing an average value of 0.06 mg/l, while the minimum values were recorded for the Al Shauaiba Old plant (0.03 mg/l). The Al-bradiah 1, Al-Garmma1 and Al Basra Unified WTP showed similar Al values of 0.04 mg/l, while the Al-Ribat, Shatt Al Arab and Al Jubila 1 WTP had similar Al values of 0.05 mg/l. The measured Al levels for the treated water did not exceed the standards for potable use of 0.2 mg/l [
29,
30] and irrigation standards of 5 mg/l [
30,
31], according to
Table 9.
The study indicated that the K values are at their maximum for treated water obtained from Abu Al Khaseeb WTP, followed by concentrations for the Al-bradiah 1 and Shatt Al Arab plants (
Table 7). The water treated by the Al-Garmma 1 plant had K values higher than those for the waters obtained from the Al Jubila 1 and Al Basra Unified plants. The Al Shauaiba Old plant has treated raw water values for K, which are significantly (
p < 0.05) lower than the ones for other WTP (
Table 7). Compared to the raw waters, no considerable K removal was observed in any of the treatment plants.
Findings show that K concentrations significantly exceed the standards for potable and agricultural use of 8 mg/l and 12 mg/l, as indicated by WHO [
3] and the Food and Agriculture Organization (FAO) [
29] of the United Nations, respectively. Considering public health concerns, there are no considerable health challenges linked to the consumption of high K dosages from drinking water as reported by Sebastian et al. [
31]. From an agricultural point of view, elevated K values may prevent stem damage of plants at predominantly low temperature as reported by Hakerlerler et al. [
32] and Cakmak [
33].
Sodium concentrations for treated waters were at their maximum for water obtained from the Abu al Khaseeb plant followed by those for the Al-bradiah 1 and Shatt Al Arab plants. The Al-Garmma 1 plant treated water leading to Na concentrations slightly higher than those for the Al-Jubila plant. Statistically, no significant difference (
p > 0.05) in Na concentrations were observed for the water treated by A-Ribat and Al Basra Unified plants, while the Al Shauaiba Old plant produced water with Na concentrations, which were significantly (
p < 0.05) lower than the ones for the other WTP (
Table 7).
Findings showed that all treated water had Na levels that significantly exceeded the standards for drinking water, which are 200 mg/l, as recommended by ICS [
26] and USEPA [
30]. For people requiring a restricted Na intake, a threshold of 500 mg/day is recommended. Moreover, a value of 200 mg Na/l for drinking water has been suggested to allow for a good taste of the water (
Table 9) [
3]. Vomiting, nausea, thirst, convulsions, muscular twitching and possible death due to hypertension may result from orally overdosing with sodium chloride [
30]. Furthermore, the treated water showed elevated Na levels that significantly exceeded the threshold for agricultural, which is 920 mg/l [
30]. Only the Al Shauaiba Old plant had treated water with Na concentrations (109 mg/l) that would allow for water use in irrigation. Saline soil may be obtained when irrigated with water containing elevated Na concentrations, which will impact negatively on soil structure and permeability as well as on plant growth and productivity [
34].
The Abu Al Khaseeb plant had treated water of the highest Mg concentration, which is similar to those of the Al-bradiah 1 plant followed by those for the Shatt Al Arab plant (
Table 7). Statistically, there is no significant difference (
p > 0.05) in Mg values for treated waters obtained from the Al-Ribat and Al Basra Unified plants. The Al-Garmma 1 WTP produced water with Mg levels higher than water from the Al Jubila 1 plant. Moreover, the Al Shauaiba Old plant produced the best effluent in terms of Mg concentrations, which were significantly (
p < 0.05) lower than the ones for the other plants (
Table 7). No exceedances were noted for treated water Mg values compared to the standards for drinking water, which are 50 mg/l, as indicated by ICS [
26] and WHO [
3], respectively. The World Health Organization indicated that drinking water portability may be impaired when concentrations of Mg plus Na sulphate exceeded 1000 mg/l [
3]. In comparison, all treated waters (except for those obtained from the Al Shauaiba Old plant) had Mg values that considerably exceeded the irrigation threshold of 60 mg/l [
30]. Irrigation water with high Mg concentrations may cause infiltration problems and subsequent drainage challenges for soil. The sodium impact on soil may increase when the Ca to Mg ratio (Ca/Mg) is less than one (Mg dominant water), which would reduce the yield of some crops such as sugar beets, wheat, maize and barley [
29].
Regarding Ca concentrations,
Table 7 shows that the maximum values were recorded for the water treated by the Abu Al Khaseeb plant followed by those for the Al-bradiah 1 and Shatt Al Arab plants. Slight differences were observed for Ca concentrations when compare to values of the Al Jubila 1 and Al-Garmma 1 plants. Statistically, the results indicated that there are no significant differences (
p > 0.05) in Ca concentrations when comparing Al-Ribat and Al Basra Unified treated waters with each other, while the Al Shauaiba Old plant treated water had Ca values, which were significantly (
p < 0.05) lower than the ones for the other plants (
Table 7). Compared to the standard thresholds of 125 mg/l and 200 mg/l as indicated by ICS [
26] and WHO [
3], respectively, recommended for drinking purposes, Ca concentrations in the treated water were considerably elevated with the exception of those linked to the Al Shauaiba Old plant.
Regarding public health, Ca is important for the human body; mainly for strong teeth and bone building, activation of oocytes, contraction of muscles, clotting of blood, transmission processes, heart beat regulations and cells fluid balances. Sufficient Ca is also required during pregnancy, breast feeding and for the main growth periods of children. Calcium deficiency may result in the deterioration of bones, leading to increases in fractures (osteoporosis) as stated by Pravina et al. [
35].
Compared to the irrigation standard threshold of 400 mg/l for Ca [
29], results showed that all treated waters had Ca concentrations that were lower than this threshold, with the exception of the Abu Al Khaseeb and Al-bradiah 1 plants, which had treated waters of Ca concentrations slightly exceeding the threshold (
Table 7). Calcium is a critical secondary nutrient for yield development as it is required in relatively large amounts for plant cell wall and temperance formations. Moreover, Ca is vital for the soil structure, as it displaces Na in the soil, resulting in soil quality improvements [
29].
The Abu Al Khaseeb plant followed by the Al-bradiah 1 and Shatt Al Arab plants had waters with the highest Cl concentrations (
Table 7). Statistically, no significant differences (
p > 0.05) for Cl were observed in the treated waters obtained from the Al-Garmma 1 and Al Basra Unified plants when compared with the Al Jubila 1 and Al-Ribat plants, respectively, while the Al Shauaiba Old plant treated water resulting in Cl values, which were significantly (
p < 0.05) the lowest. Treated water from all plants had Cl values that were considerably exceeding standard thresholds, which are 250 mg/l for drinking water, as indicated by ICS [
26] and WHO [
3], and 1063 mg/l for irrigation [
30]. In treatment plants, Cl was added as a disinfectant to purify the water in terms of pathogens. Chlorine is available as an abundant ion in nature mainly in the form of salts. Exposure to Cl gas or liquid could be harmful even in small amounts. Highly contaminated drinking water with Cl may cause respiratory issues such as asthma and cell damage, mainly in children, as well as increasing the risk of bladder cancer [
3]. Using Cl as a disinfectant is useful in managing and maintaining a drip irrigation system. However, highly chlorinated irrigation water may be toxic for plants, resulting in the slow-down of plant growth or even their death [
29].
The highest sulphate concentrations were noted for the Abu Al Khaseeb plant followed by those for the Shatt Al Arab and Al-bradiah 1 plants (
Table 7), while the lowest values were recorded for those waters from the Al Shauaiba Old plant followed by ones for the Al-Ribat plant. Statistically, the results showed that there is no significant (
p > 0.05) difference in sulphate values when comparing treated waters of the Al-Ribat plant with those of the Al-Jubila1, Al Basra Unified and Al-Garmma 1 plants, while the Al Shauaiba Old one showed treated waters with sulphate values, which were significantly (
p < 0.05) the lowest.
Compared to drinking water standards, treated waters from all plants had sulphate concentrations that considerably exceeded the thresholds of 400 and 250 mg/l for drinking water as indicated by the ICS [
26] and WHO [
3], respectively. According to the World Health Organization, drinking water with high sulphate concentrations may cause laxative effects mainly when the two hardness constituents (both Ca and Mg) are available [
3]. Moreover, the sulphate levels for all treated waters considerably exceeded the irrigation standard of 960 mg/l [
29]. High sulphate availability in the irrigation water may increase the salt levels in the soil, resulting in the reduced availability of phosphorus for plants, as reported by the FAO [
29].
Water hardness is the amount of dissolved Ca and Mg in the water [
3]. Similarly, the Abu Al Khaseeb and Al-bradiah 1 plants produced water of the highest hardness values followed by those of the Shatt Al Arab plant (
Table 7). No significant differences (
p > 0.05) were observed when comparing treated water hardness concentrations from the Al Jubila 1 and A-Ribat plants with those of the Al-Garmma 1 and Al Basra Unified plants, while the water hardness values for the treated water of the Al Shauaiba Old plant were significantly (
p < 0.05) the lowest. The total hardness of water is mostly expressed as milligrams of Ca carbonate per liter [
3].
The TH for the treated water had the highest concentrations for the Abu Al Khaseeb, Al-bradiah 1 and Shatt Al Arab plants (
Table 7), while the lowest values were observed for the water obtained from the Al Shauaiba Old plant. No considerable differences were found when comparing the TH values for waters from the Al Jubila 1 and Al-Garmma 1 plants with those from the Al-Ribat and Al Basra Unified plants.
Concerning drinking water standards, the World Health Organization classified water based on Ca carbonate concentrations to be soft if the concentration of Ca carbonate is <60 mg/l, moderately hard for concentrations between 60 and 120 mg/l, hard for values between 120 and 180 mg/l and very hard for values > 180 mg/l [
3]. Based on this classification, treated water obtained from all plants can be classified as “very hard” (TH > 180 mg/l). Moreover, treated water from all plants (except for Al Shauaiba Old) showed TH values that considerably exceeded the Iraqi and WHO standards for drinking water, which are 500 mg/l and 300 mg/l, respectively [
3,
29].
Generally, seasonal variations in concentrations were the highest during hot months (June to October) (
Figure 4), possibly due to the high water demand caused by elevated temperatures. Moreover, the SAR, as the main raw water source, showed deteriorations in water quality parameters during hot months as well. No significant differences were observed when comparing the inflow and outflow water properties for all parameters, indicating that none of the treatment plants were fit-for-purpose.