Many parts of the world have started using treated sewage water for reuse such as irrigation or even drinking water. There is much potential to implement aquifer storage recovery (ASR) systems that reuse treated effluent sewage (TSE). To recycle TSE in the Middle East, further knowledge and testing of system sites for water recycling, more secure safe, large storage places, site specific wells, and thorough monitoring of system sites is needed. The hydrogeologic data collected at this point is not extensive enough to determine how water will behave in many sites. Water can be used in the dry season from these storage sites, and many harmful compounds will start to break down over time. Maliva et al. shows in this paper that TSE can be broken down to pure potable water. –Darien Martin
Maliva, R., Missimer, T., Winslow, F., Herrmann, R., 2011. Aquifer storage and recovery
of treated sewage effluent in the Middle East. Arabian Journal of Science and Engineering 36, 63 – 74.
In order to be cost-effective and help the Middle East meet its supply and demand with water, storage areas should provide long term holding capacity. Above ground systems don’t meet this requirement. Storage tanks, which could hold enough water for long-term storage, would be too expensive, and surface reservoirs have large evaporative loss and demand lots of land. Underground storage in aquifers is best suited for the job. Managed aquifer recharge (MAR) is idealized; using wells or added surface water to fill aquifers keeps them at a high enough water pressure to prevent salt-water intrusion. In these systems, water can be is added and drawn from the same well, or added through infiltration basins.
Maliva et al. presents two approaches to storage and recharge of water in the Middle East. Water can be either physically or chemically bounded. Physically bound storage is enclosed by essentially impermeable concrete or rock on bottom and sides, and adding water and increasing pressure maintain MAR. Chemically bounded ASR systems include a freshwater body injected into brackish water. Brackish water is flushed away and then only freshwater surrounds the well. A zone of mixed water forms between the two water qualities, but separation can be kept with the right levels of pressure.
Pathogenic microorganisms and chemical contaminants are found in TSE before treatment. Pathogenic microorganisms coming from animals’ intestines are a top concern and can infect a person who is exposed only once. The decay or removal of these microorganisms in Middle East groundwater may take several days to weeks in these warm waters. Chemical contaminants are also found in aquifer water from industrial activity, wastewater, and treatment chemicals. Treatment chemicals react with compounds in the water to form disinfection byproducts (DBPs). Emerging chemical compound threats to health, which are not yet controlled, are called CECs. Technologies to identify CECs have recently started to improve, and are now being measured in groundwater, surface water and TSE. CECs are a threat to health throughout the world wherever humans go. A certain degree of treatment and tests is required before TSE is injected into ASR systems. Components of the wells and aquifers should be designed to be readily accessible so that the ASR system can continue to be tested at every step of its processes. Possible threats to water purity and recovery efficiency (the percent of freshwater able to be retrieved) include surrounding rocks of multiple porosity levels with irregularities such as fissures which can make water movement unpredictable.
TSE converted to potable water is believed to be pure, but is usually avoided for the time being. Possibilities for reuse include direct potable drinking water and indirect potable reuse such as irrigation. With TSE reused as drinking water, TSE would be properly treated and then integrated into the potable water systems. Many times adding it to freshwater then breaks down harmful compounds faster. But for now, keeping systems with TSE in them physically separated from pure water systems, is the accepted practice. In Saudi Arabia, the Council of Leading Islamic Scholars agrees that TSE could be fully purified again to drink, and TSE potable water will likely go up in acceptance and even demand in the near future, especially in areas that have a dramatically dry season.
Some places are being considered for aquifer storage resource systems that incorporate TSE. In the United Arab Emirates, where conditions for underground storage are not ideal with high salinity and multiple amounts of rock porosities, ASR systems have been constructed in shallow, unconfined aquifers. The city of Abhu Dhabi is testing a site for TSE incorporation. Also in Riyadh, Saudi Arabia, the depleted Minjur aquifer is now filled with treated TSE water. Sites have also been tested in Kuwait.
Through testing of specific sites, it is likely that more ASR systems including treated TSE will emerge throughout the Middle East with the increase of water demand. Especially arid regions with population growth will be in great need of more water and TSE may become an important source. Information on the hydrogeologic conditions for proper ASR systems incorporating TSE is limited, but growing. Procuring pure water supplies from TSE is very feasible areas around the Middle East are being tested for TSE purification and storage plans.