Geochemistry of wastewater recharge: Managing heavy metals sorption and controlling soil degradation processes in recharge basins of the SHAFDAN wastewater reclamation plant

The project objectives are to study the long-term geocemical changes in the recharge-basins soils of a wastewater treatment plant (The Dan Region Reclamation Project (SHAFDAN)) using the Soil Aquifer Treatment (SAT) approach, and to evaluate their effects on the chemical and hydraulic performance of the system. Studies are conducted in basins operating up to 2 decades by comparison to the adjacent native sand dune. A controlled loading experiment, using an experimental pond on-site in the SHAFDAN area, is on-going as well. The Dan Region Reclamation Project (SHAFDAN) is the largest municipal wastewater reclamation project in Israel, serving a population of 1.2x106 people. The plant treats about 100x106 m3 of wastewater per year with plans under way to expand its capacity to 140x106 m3/yr. Raw municipal wastewater is treated either in facultative oxidation ponds or in a mechanical-biological plant using an activated sludge process involving nitrification/denitrification steps. As a final step in the process, the recycled effluents are recharged into the local aquifer using sandy recharge-basins, for polishing and storage in what is called the "Soil-Aquifer Treatment" (SAT). Following that, the water is pumped and supplied to irrigation. SAT was designed to filter-out microorganisms and suspended materials from the effluent, reduce COD and BOD, and remove inorganic constituents. Its ability to perform these tasks is crucial for the proper performance of the whole reclamation operation and for obtaining a high quality product that can be used for "unlimited irrigation"

Funded by Mekorot, Israel National Water Co.

(Participants: A. Banin (PI), C. Lin, G. Eshel, K.E. Roehl, I. Negev, D. Greenwald, Y.Shachar and Y. Yablekovitch, Hebrew University)

Study of the causes for continuous and seasonal decreases in percolation rate of the recharge basin soils at the SHAFDAN sewage water reclamation plant and development of treatments for their prevention and control

Significant repeating decreases in the effective percolation rate during the fall and the winter seasons was discovered in the recharge basins of the Soreq site at the SHAFDAN plant. The project objectives are: (a) To quantify the extent of seasonal changes during the annual cycle, (b) to study the causes and mechanisms for the critical deterioration in recharge rates during the fall/winter and (c) to initiate a field trial to test the effect of amendments on the seasonal and long term deterioration in infiltration rates.

Funded by Mekorot, Israel National Water Co.

(Participants: A. Banin (PI), D. Greenwald, C. Lin, I. Negev and Y. Yablekovitch, Hebrew University)

Redox processes in soils irrigated with reclaimed sewage effluents: Field cycles and basic mechanisms

The use of reclaimed sewage effluents for irrigation is increasing at a significant rate. The relatively high levels of suspended and, especially, dissolved organic matter and nitrogen in effluents likely will affect the redox regime in field soils irrigated with them. In turn, the changes in redox regime will affect, among other parameters, the organic matter and nitrogen dynamics of the root zone, trace organic decomposition processes, and adsorption and release of heavy metals. As such, this may profoundly alter the quality and productivity of fields irrigated with reclaimed sewage water. The overall objective of the project is to investigate in detail the changes in redox potentials in situ in fields irrigated with reclaimed wastewater and continue to develop basic understanding of the controlling processes. The specific objectives are (a) to monitor continuously the redox potential in field soils irrigated with reclaimed waste water and compare them with soils in adjacent fields irrigated with fresh-water and (b) to study, under controlled conditions, the effects of redox changes on two selected key processes related to waste water irrigation, namely heavy metals sorption and pesticide degradation.

Funded by IS-US BARD.

(Participants: A. Banin (PI), Hebrew University, J. W. Stucki, University of Illinois; J. E. Kostka, Florida State University)

Mars soils: Chemical and mineralogical properties and the exobiological connections

One of the key issues related to future Mars exploration is the search for water and life. Mars soil contains the clues for water activity on the planet's surface and its enigmatic nature is still posing questions related to our understanding of Mars evolution. Experimental and modeling studies are conducted to better understand the nature of the soil and develop scenarios and models for its formation, addressing the existing information on their rather enigmatic nature.

(Collaborators: R.M. Mancinelli, SETI Institute/NASA-Ames Research Center, Moffett Field, CA., USA; J.B. Orenberg, San Francisco State University; T. Roush, NASA-Ames Research Center).