AWWA WQTC64057

In support of the U.S. government's reconstruction effort in Iraq, the Iraq Rural Water Reconstruction Program (the rural water program) seeks to find cost-effective, sustainable solutions for providing potable water in rural areas. The rural water program will install 71 potable water systems in rural communities of fewer than 5,000 people, resulting in the provision of 35-liters of potable water per person each day. Many of these communities are small and remote. Surface water from the Tigris and Euphrates river systems supplies water to about half of Iraq's land area including rural areas. The quality of untreated water throughout rural areas varies widely but generally is poor. Heavy mineralization, suspended solids and frequent high salinity characterize Iraq's water supply. The rural water program utilizes chlorination, compact filtration units, and/or reverse osmosis desalination to purify the local surface water source. Conventional water treatment systems include coagulation, flocculation, sedimentation, and filtration. In compact units, the same steps are combined in one treatment train. These units, including the control system, are pre-designed, assembled at the factory, skid mounted, and transported fully assembled to the site. At the site, the treatment unit requires only piping and electrical connections to complete the installation. Waters with TDS higher than 1,000 mg/l and less than 10,000 mg/l are frequently treated as brackish water. Most of the water in Iraq is considered brackish, and expensive desalination equipment will be required. This degree of treatment is not affordable for the Iraqi people. Consequently, the brackish level for feasible plants was increased to 1,500 mg/l TDS and water sources will not be utilized if the raw water TDS is higher than 5,000 mg/l. Generally speaking, desalination consumes a large amount of energy. Many remote villages rely on costly, often limited supplies of diesel fuel for their energy needs; therefore, finding relatively inexpensive, widely available water treatment units is desirable. Reverse osmosis (RO) was chosen as the desalination process in lieu of ion exchange. The selection considerations included equipment capital and O&M cost, chemical handling, concentrate disposal, system safety and simplicity of operation. RO permeate was blended with a bypass stream of water to produce a finished water having a TDS of no more than 1,500 mg/l. Hence, assuming the maximum raw water TDS is 5,000 mg/l and the minimum TDS removal of RO is >90%, at 75% recovery, the maximum projected permeate TDS is 500 mg/l, and the minimum by-pass to permeate blend ratio will be 28%. Common surface water post-treatment elements include disinfection, chlorine contact tanks, treated water pumping, on-site treated water storage with optional offsite elevated treated water storage, on-site power service and a back-up diesel generator set. There are three major concerns critical to the wider use of desalination in inland areas. These include addressing the environmental issues of concentrate disposal, and improving desalination efficiency. Includes table, figures.