AWWA WQTC64057

In support of the U.S. government's reconstruction effort in Iraq, the Iraq Rural WaterReconstruction Program (the rural water program) seeks to find cost-effective,sustainable solutions for providing potable water in rural areas. The rural water programwill 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 thesecommunities are small and remote.Surface water from the Tigris and Euphrates river systems supplies water to about half ofIraq's land area including rural areas. The quality of untreated water throughout ruralareas varies widely but generally is poor. Heavy mineralization, suspended solids andfrequent high salinity characterize Iraq's water supply. The rural water program utilizeschlorination, compact filtration units, and/or reverse osmosis desalination to purify thelocal 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, skidmounted, and transported fully assembled to the site. At the site, the treatment unitrequires 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 treatedas brackish water. Most of the water in Iraq is considered brackish, and expensivedesalination 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 1,500mg/l TDS and water sources will not be utilized if the raw water TDS is higher than5,000 mg/l.Generally speaking, desalination consumes a large amount of energy. Many remotevillages rely on costly, often limited supplies of diesel fuel for their energy needs;therefore, finding relatively inexpensive, widely available water treatment units isdesirable. Reverse osmosis (RO) was chosen as the desalination process in lieu of ionexchange. The selection considerations included equipment capital and O&M cost,chemical handling, concentrate disposal, system safety and simplicity of operation. ROpermeate was blended with a bypass stream of water to produce a finished water having aTDS of no more than 1,500 mg/l. Hence, assuming the maximum raw water TDS is 5,000mg/l and the minimum TDS removal of RO is >90%, at 75% recovery, the maximumprojected permeate TDS is 500 mg/l, and the minimum by-pass to permeate blend ratiowill be 28%.Common surface water post-treatment elements include disinfection, chlorine contacttanks, treated water pumping, on-site treated water storage with optional offsite elevatedtreated 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, andimproving desalination efficiency. Includes table, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2006

Number of Pages:

11

File Size:

1 file , 620 KB