NANOTECHNOLOGY PROCESSES FOR LOW QUALITY WATERS POLISHING FOR SUSTAINABLE AGRICULTURE PRODUCTION AND GROUNDWATER PROTECTION

摘要

Low quality waters and primarily secondary treated urban wastewater can be utilized for diverse purposes, including irrigation, maintenance of recreation sites, aquatic life preservation and groundwater recharge. Secondary effluent commonly contains elevated amounts of dissolved solids and subject to the treatment level also contains pathogens. Advanced complementary wastewater treatment is required in order to maintain low health risk, sustainable agriculture production, and minimize salinization processes of the soils and groundwater along with preventing long-range time adverse effects of gradual accumulated environmental pollution. These challenging goals can be attained mostly by implementing complementary nanotechnology processes. Secondary domestic effluent of the City of Arad (Israel) has been reused in field experiments for irrigation of edible crops. The secondary effluent is polished by a two stage nanotechnology system: UltraFiltration (UF) and Reverse Osmosis (RO) membranes. The UF stage is efficient for the removal of the suspended matter, organic matter and the pathogens. The successive RO stage provides safe removal of the dissolved solids (salinity). The UF stage can be considered as well as a pretreatment stage for the RO stage, diminishing fouling risks of the RO membranes. Preliminary removal of the dissolved solids from the effluent, prior to application (via the RO stage), offsets the need of extra leaching of salinized soils. Effluent of various qualities as given by the salinity (Electrical Conductivity-EC) has been applied for agricultural irrigation of a series of annual crops. Best agricultural yields were obtained when applying effluent with minimal amounts of dissolved solids as compared with conventional secondary effluent without any complementary treatment. It was reflected as well by the soil salinity which was the lowest in the plots irrigated with RO effluent. Applying effluent after the RO treatment stage in regions with shallow groundwater will guarantee minimal environmental contamination.