The Tigris is considered the sole surface water resource in Mosul city/IRAQ. Its water is used for domestic, municipal, industrial, agricultural, and recreational purposes. Besides, the Tigris is thought to be the ultimate sink for all wastewater arising from above activities.
The Tigris had been put under monitoring for years. Many papers and theses were published regarding its sources of pollution, pollutants concentration, degradation in water quality, and other aspects [1
This paper is another effort added to previous works trying to shed light on evaluating status of the river as it passes through a selected stretch within Mosul city. Such stretch includes the major point and non point sources of pollution that do affect river water quality and quantity.
Results and Discussions
The Tigris - like any other water resource - is subjected to numerous sources of pollution. Municipal discharges, industrial pollutants, agricultural activities residuals, direct runoff, tourism, illegal practices, atmospheric pollution, and others are few examples. The most important sources covered for the purpose of this paper are listed in table (2)
It is estimated that as huge as 400000 m3
of wastewater is daily discharged - untreated - into the river. This is equivalent to 17000 m3
/hr with a peak of 20000m3
/hr at day hours. Domestic waste loads, on the one hand, add a great burden on the pollution of the Tigris. These wastes comprise foul wastes of more than 6000 dwellings and apartments lacking waste collection system. Considerable amounts of these wastes are directly or indirectly (via valleys) discharge their loads into the river (table 3
The field survey reveals that some of the pollution sources are direct point sources while some other sources are indirectly affecting the river water quality. As these sources differ, the nature of their pollution loads vary accordingly as shown in tables (4
. The characteristics of discharged wastewater can be grouped into the medium-strong categories according to guidelines [8
]. The tests also verify that a clear deterioration in water quality does occur. Concentration of various contaminants & compounds exceed the limits recommended by local and authorized agencies [9
Odor, foam, color, death and migration of aquatic life, and dominance of anaerobic conditions can easily be detected near sewer outfalls. These adverse consequences as well as the increase of pollutant concentrations have lessen the river aesthetics, increase hardness, salinity, and rendering the water unfit for different beneficial uses.
The changes in the physical characteristics of the river water such as temperature, turbidity, and suspended solids are clearly demonstrated in table 7
. These changes are detected as the river passes along the stretch of the study area. In the north of the city there exists a large water impoundment. Some quarries and constructional mills are encountered. Animal breeding (buffalo, sheep and cows) are widespread. In the heart of the city there are more than 15 point sources discharging their loads into the river. It is strongly stressed that such activities will continue deteriorating the river water quality.
One of the most important sources of pollution is the domestic discharges. Such wastes render the river water unfit for beneficial uses. Previous studies [11
] revealed that the river water is no longer valid for swimming. The total bacterial count in the discharged wastewater is amounted as high as 2×104
. These amounts exceed the recommended values [12
]. This disorder is attributed to some illegal practices such as discharging toilet waste directly into the river or due to in-house slaughtering activities.
Eutrophication, a phenomenon that largely takes place at lakes and slow moving water bodies has found an access to occur in the Tigris. This problem arises from the fact of using large amounts of nutrient-rich detergents. Throughout the past years, detergents were distributed to the families as a part of a monthly ration of oil for food program during sanction (1991-present). Such detergents contained high concentrations of phosphorous the main cause of eutrophication, (see table 8
Moreover, eutrophication can be detected by chlorophyll measurement which surpasses the guidelines of 2mg/l [13
]. Eutrophication is known of its vast adverse effects, some of which are listed in table (9)
. The BOD5
values represent the organic pollution of the Tigris. Organic load leads to decline of dissolved Oxygen and release of ammonia and nitrite. This declination may extend for tens of kilometers.
illustrates BOD variations along the studied stretch. This table indicates that river water can be classified as poor-good in terms of quality as per authorized standards [14
]. It does show that the Tigris starts recovering its health after 40km.
On the other hand, the survey revealed the huge adverse impacts incurred by industry, tourism and health-care institutions. Most of local industries have no wastewater treatment plants. Wastes are directly discharged untreated into the Tigris. Most of existing wastewater treatment plants do not perform as expected. Moreover, such plants are secondary and incapable of removing nutrients (P&N compounds) as well as they poorly perform at shock loads occasions. Table (11)
shows the performance of some plant covered by the survey.
Heavy metals such as chrome, copper, and arsenic may have an access to reach the river. Some industries produce these elements in their processes like textiles industries, tanneries, etc. Al–Layla & Al-Rawi confirm this fact upon studying impact of textile wastewater discharges on the Tigris [15
]. Lead concentrations may increase in the river water. This element arises from traffic and reaches the river from runoff or via atmosphere. The problem with heavy metal is that they are absorbed by particulates at normal pH levels causing very low dissolved traces and consequently its monitoring becomes very complicated [16