CHANGES IN HYDRAULIC AND POLLUTION LOADS FOR THE SEWAGE STREAM OF WADI AL-SAMN (HEBRON DISTRICT )

Abstract

Current disposal options of municipal wastewater in some cities of the West Bank are the discharge into wadis directly from the sewer outfall. This is demonstrated frequently through the existing of many wastewater streams in the West Bank. Normally domestic and industrial wastewaters are received into municipal sewers. The wastewater flow into wadis in such areas is existing over the year and in wintertime, chance is given to runoff water to be mixed with wastewater and thus loosing both waters without getting any beneficial use from them. On the contrary, pollution problems are becoming more complicated under wet flow conditions because the wadi flow or the wet section length is becoming longer.

The focus here is given to Hebron City wastewater stream (named wadi al-Samn, according to its name at the upstream), which originates in the Palestinian Authority areas, South of Hebron, passes Yatta, Beit-Emra, Karmah, Abu-al-Asja and Daherrya communities before it runs through the 1948-cease line fire to the east and then south of Beer al-Saba', and then enters Gaza, where it ends in the Mediterranean. The wadi total length is more than 120 km starting from the sewer outfall (upstream) at Hebron City and ending at the Mediterranean Sea (downstream), of which 47 km are inside the Palestinian Authority area including the West Bank and Gaza Strip.

The wadi path length at different sections is: 9 km for Hebron section, 11 km for Yatta section, 4 km for Beit Emra section and 14.5 km for Daherrya section. This means that the wadi extends for a distance of 38.5 km inside Hebron District borders while it extends for a length of 77 km inside the 1948-Palestine. Also the wadi part crossing Gaza Strip is at a length of 8.75 km which finally ends in the Med. Sea.

The influenced population from the wadi discharge is exceeding 50,000. While the influenced land by the wadi pollution is possibly extending at a distance of 0.5 km from each wadi side. This means that the affected land area could be about 40 km2 inside the district. The effect on groundwater is expected and the wadi extends for a distance of 5 km on the Eastern basin and not less than 30 km on the Western basin. Pollution effects on agriculture, land (soil), ground and surface waters, wildlife and air pollution are expected to be severe.

Dry weather flow values indicates an average flow rate value around 3800m3/d with velocity variation from 1.97 m/min to 7.36 m/min and with wadi wet cross sectional area variation from 0.31575 m2 to 0.698 m2. Wet weather flow values indicates flow rate value around 28000m3/d and it represents storm conditions. This means that the wadi flow under wet conditions could be not less than 8 times its value under dry conditions.

At a certain segments of the wadi, a 38% COD reduction occurred for the wastewater while an increase of 36% occurred at other segments due to wastewater loads coming from tankers which originate from sepatge and stone-cutting industry. Then a decrease of 12% occurred at a following section and finally as the wastewater flows to at the wadi final part, an increase in COD value of 35% took place due to availability of sepatge and stone-cutting loads again.

Similar trend were observed for NH4 and TSS as the wastewater flows to the wadi downstream.