Abstract
The Dan Region Reclamation Project (Shafdan) reclaims ~125 millions of cubic meters per year (Mm3/year) of treated wastewater from the Tel Aviv Metropolitan area. Following secondary treatment, the effluent is recharged into a sandy aquifer for soil aquifer treatment (SAT). Over the past three years, a decrease in recharge capacity was noticed. Several operational causes were considered including reservations regarding the tillage procedure of recharge ponds. Tillage of the recharge ponds facilitates aeration, breaking surface crusts and the removal of vegetation. The procedure includes deep (40–60 cm) plowing and shallow (10–20 cm) sweep-knives (SK) cultivator or discus. In this research, the existing tillage equipment was compared to a new equipment, which includes a deep subsoiler and a chisel-knives (CK) cultivator. The effects of each tool on the infiltration rate (IR), recharge capacity, and soil compaction were examined. The results suggest a significant improvement in the recharge capacity, up to 95% and 15% on average following subsoiler and CK cultivator treatments, respectively, with respect to the existing plowing treatment. In addition, the depth of the compacted soil layer increased from ~30 to ~55 cm after subsoiler treatment. It seems that this shallow layer, developed under an improper tillage regime, played a major role in the reduction of the recharge capacity. Essential understanding of other operational factors such as drying periods, preparation of the field, and soil micro-topography was also achieved.
Highlights
IntroductionThe Dan Region Wastewater Reclamation Plant (Shafdan plant), established during the 1970s, provides a centralized, high-quality solution for sewage produced by the most populated area in Israel
The Dan Region Wastewater Reclamation Plant (Shafdan plant), established during the 1970s, provides a centralized, high-quality solution for sewage produced by the most populated area in Israel.The plant collects the sewage from the Tel-Aviv Metropolitan area (Dan Region) and neighboring municipalities, treats it and recharges it into a defined coastal aquifer section for complementary soil aquifer treatment (SAT)
The reduction in recharge capacity, and its restoration on the other hand, are not solely related to the tillage equipment, and to additional parameters that are required for correct maintenance procedures
Summary
The Dan Region Wastewater Reclamation Plant (Shafdan plant), established during the 1970s, provides a centralized, high-quality solution for sewage produced by the most populated area in Israel. The plant collects the sewage from the Tel-Aviv Metropolitan area (Dan Region) and neighboring municipalities, treats it and recharges it into a defined coastal aquifer section for complementary soil aquifer treatment (SAT). In this manner, the Shafdan plant treats about 125 Mm3 /year of raw sewage from seven municipalities, industrial areas, and approximately 1.5 million inhabitants. The sewage is treated to a level of secondary effluents using a mechanical biological treatment plant (MBTP) prior to infiltration in the SAT ponds. The recovered effluents, after SAT treatment, are characterized by excellent quality for most of the measured parameters, which comply with the levels allowed by the Israeli Health Ministry for unrestricted irrigation of any crop [1,10,11]
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