Water and nitrogen mass balance for Nablus-East

Abstract

Analyzing the urban water cycle is crucial for adequate urban water management and pollution control of the natural water cycle. Knowledge about exfiltration from sewer networks is very limited; but the few available studies indicate that exfiltration pollution loads pose un-counted serious threat to groundwater. The research was carried out on Nablus-East with a population of 94,910 inhabitants, to assess the pollution load of wastewater exfiltration from the sewers network and outlets. The investigations were carried out mainly on two catchments; a sub-main small controllable catchment, and a main catchment representing 86% of Nablus-East. The wastewater flows and loads from the two catchments were measured, and water consumption records were obtained as ArcMap software shapefiles. The results revealed that 82.2% of the consumed water ends up in the sewer network. The exfiltration wastewater from the sewer network resembles 12.8% of the consumed water, while 65.2% drains untreated to wadi Al-Sajor through the outlets, and 4.2% ends up in cesspits. The specific water consumption, wastewater production, wastewater exfiltrated from the sewer network and wastewater reaches the outlet are respectively 79.6, 65.4, 10.2 and 55.2 L/c.d. The specific pollution loads exfiltrated from the sewered part of Nablus-East are 2.4(g N/c.d), 0.25 (g TP/c.d), 23.5(g CODt/c.d) and 13 (g BOD/c.d). The total nitrogen load of the produced wastewater from Nablus-East is 1.88 (kg N/ha*day), out of which 1.49 (kg N/ha*day) reaches the outlets as a major point source pollution. The remaining 0.39 (kg N/ha*day) routes into exfiltration from sewer network of 0.29 (kg N/ha*day) and in cesspits is 0.10 (kg N/ha*day). The annual urban nitrogen loading of Nablus-East wastewater is 688 (kg N/ha*yr), which is very high due to high population density. Therefore, a wastewater treatment plant should be constructed as a first priority, and the sewers network should be rehabilitated.