ميكروبيولوجيا المياه في حوض وادي العروب
عيد أحمد عيسى الطوباسي
Eid Ahmad Issa Toobasi
Water resources in Palestine are threatened by many dangers; overexploitation of the Palestinian groundwater by the Israelis and pollution of groundwater by wide spread Israeli settlements on Palestinian land. These factors, along with poor awareness of protection of the environment by the Palestinians, seriously threaten the Palestinian water resources. From the public health perspective, this increases the level of water pollution which results in many health risks. The study of the microbiology of a water source is an important aspect in evaluating the quality of water. The global burden of infectious waterborne disease is considerable. Reported cases highly underestimate the real incidence of worldwide waterborne diseases, in this regard Palestine is no exception. Several studies in the West Bank dealt with the microbiology of water and pointed to the poor quality of water used for human consumption. These studies examined few microbiological indicator bacteria in cisterns, dug wells and swimming pools. One recent study (Atteyeh, 2007) examined the presence of DNA of Helicobacter pylori and other pathogens (presence of DNA rather than viable bacteria) in three Palestinian water resources, one of which is Wadi Al-Arroub. In this study the microbiology of a water basin in a heavily populated area of the West Bank, namely Wadi Al-Arroub was examined. The study focused on groundwater samples from 9 deep wells and 11 springs and identified several indicator bacteria, several bacterial pathogens, two protozoan pathogens, and nitrate level. The study was conducted in the period between May 2005 and January 2006 on water samples from Wadi Al-Arroub drainage basin in Palestine. The study catchment with an area of 61 km2 is a sub-basin of the Dead Sea-Jordan River Basin and part of the Eastern Basin of the Mountain Aquifer. The objective of this study is to provide information about Wadi Al-Arroub drainage catchment by identifying the different microbiological pollutants, their possible sources and the impact on water resources, and to highlight possible measures to improve the situation. iv Total coliform (TC), Faecal coliform (FC), Faecal streptococci, Total Viable Count, Staphylococcus aureus, Pseudomonas aeruginosa, Entameoba histolytica, Giardia intestinalis, and nitrate (NO3) level were analyzed for ground water resources. Eighty five samples were collected; the TC bacteria isolated were identified in 17 (52%) out of 33 well water samples and 33 (94%) out of 35 spring water samples. Samples analyzed for FC were not detected in well water samples, but 35 (80%) out of 44 spring water samples had FC. This indicates that spring water is highly contaminated with wastewater infiltration from cesspits and stream wastewater. Faecal streptococci were detected in 5 (12%) out of 41 well water samples and 38 (86%) out of 44 spring water samples. Staphylococcus aureus was identified in 9 (22%) out of 41 well water samples and 36 (82%) out of 44 spring water samples. Pseudomonas aeruginosa was detected in 3 (7%) out of 41 well water samples and 8 (18%) out of 44 spring water samples. The Total coliform bacterial isolates were differentiated into Enterobacter, Klebsiella, Citrobacter, Escherichia coli and Faecal coliform and were identified at 48 %, 9%, 12%, 15% and 0% respectively in groundwater well samples. And were identified at 46%, 54%, 46%, 71%, and 80% respectively in spring water samples. This indicates more serious spring water contamination. The identification of E. coli in 5/33 (15%) of well water samples and in 25/35 (71%) of spring water samples is an indication of faecal contamination of these water sources. All well water samples had a Total Viable Count (TVC) less than 500CFU/ ml after chlorination which agrees with the WHO guidelines for drinking water ≤ 500CFU/ ml. Protozoal pathogens such as E. histolytica and G. intestinalis were not detected in any spring water samples in spite of the presence of bacterial indicators and pathogens. The nitrate (NO3) concentration (< WHO guideline 45 mg/l) is higher in spring water samples (75%) than in well water samples (20%). Nitrate is a major component of fertilizers which are overused in agriculture. Another source of nitrate may be wastewater from different sources especially poorly designed cesspits and stream wastewater. v These results show that tested springs are highly polluted and to a greater extent than the deep wells. This is directly related to the rocks characteristics and depth of ground water. Specific measures have to be taken to improve the situation of spring water, aimed at reducing the risk of waterborne infectious diseases.
الدراسات البيئية , Environmental Studies