A TECHNICAL EVALUATION OF THE EXISTING WASTEWATER TREATMENT PLANTS IN THE HEBRON GOVERNORATE

Abstract

The subject of sewage treatment is increasingly gaining interest due to the severe pollution impacts posed currently by cesspits and septic tanks in rural areas of the Hebron District. Currently, sewers and treatment plants are only available in Kharas, Nuba, Deir-Samit, and Al Aroub among all rural areas of the Hebron district. This study demonstrates in depth the performance of these four wastewater treatment plants.

Low cost wastewater treatment plants in Kharas and Nuba villages were constructed by Palestinian Hydrology Group (PHG), where wastewater treated anaerobically using Upflow Activated Sludge Blanket (UASB), and then aerobically using wet land. The system applied in Deir-Samit village is anaerobic primary treatment one. It consists of two compartment septic tanks followed four compartment biofilters and finally a storage tank. A pilot scale duckweed system was constructed in Al-Aroub secondary school by Environmental Authority. The system consists of settling tank, Duckweed lagoons (ponds) and storage reservoir.

Testing of the four systems carried out by different investigators show that the performance of the plants is very good, with little differences between each treatment plants. The removal efficiency in Kharas and Nuba treatment plants in terms of COD and BOD reaches about 90%, while for Deir-Samit and Al Aroub reaches 70%. The efficiency for other pollutants removal was quite good. The systems were able to treat the sewage at acceptable levels and solve environmental problems. The fieldwork of this study includes; registration of all distinguished problems along with flow measurement, frequent sampling of wastewater from different points in the treatment plants, and then testing the collected samples in the laboratory of PHG. The results of analysis for each treatment plant were compared together to recommend and adopt the most suitable small scale wastewater technology for rural areas in the Hebron Governorate.

The site visits and preliminary investigation show that there is some problems in the treatment plants such as; the wastewater treatment plant at Kharas receives high loads of olive mill effluents and the wastewater color is black and with oily appearance and odor. The duckweed plant in the first cell in Al Aroub wastewater treatment plant is died while the second cell is with complete plant cover. The wetland in Nuba wastewater treatment plant is not full of wastewater and no outflow is detected.

The water consumption in the studied rural areas is very low (about 40-70 l/c.d). Because of this, the values of some parameters are comparatively higher than the typical values. Even this the results reveals that the rural sewage is less concentrated than municipal sewage.

The whole systems at Kharas and Nuba achieved 93% removal in terms of COD, 90% in terms of TSS, 35% in terms of TS, and 20% in terms of ammonia. While the system of Deir Samit achieved 62%, 70%, 20% and -20% removals for the COD, TSS, TS and NH4. The Duckweed ponds system at Al Aroub achieved removal efficiency of 60% for COD, 70% for TSS, 27%for TS, and 55% for ammonia.

It seems that the UASB-Wetland system at Kharas and Nuba villages is more efficient in the reduction of pollutants. At optimal conditions, the septic tank-biofilter and duckweed ponds systems are a good choice for replacing the existing cesspits and could serve a cluster of houses.

The success of sewage treatment systems reported in this project make us more confident to apply these technologies in other rural communities. UASB anaerobic system followed by wetland is recommended in this study.