IWRA Proceedings

AbstractMany rural areas located in arid or semi arid climates depend on underground water as the only source of fresh water. Unfortunately, many of these sources present high levels of toxic and non- toxic elements like sodium chloride, sodium sulfate, arsenic and fluoride. These elements like many others make underground water unacceptable for human consumption, based on the concentrations found and on the local potable water standards. Reverse osmosis (RO) has become the standard way to desalinate small scale process. RO investment costs have been reduced in the last 20 years to an affordable amount even for rural areas; however operating costs have increased again in the past 20 years due to an increase in the rising cost of energy. In many cases rural areas have a very low income and energy sources are sometimes not available, this can lead to abandoned RO rural units or even result in no units at all. The abandonment of rural RO units is the direct result of the absence of both electrical and diesel payments. This situation brought the objective to develop an eolic RO unit with a lower operating cost, compared to the standard electrical RO unit operating cost. The objectives of the project were 1) To develop of an eolic energy buffer system to reduce pressure variation between the commercial eolic pump (wind mill) and the RO membrane unit. 2) The installation and performance monitor of a pilot eolic RO unit under different wind conditions. 3) The evaluation of energy savings per m3 of produced potable water. A commercial 16ft wind mill with a 3” piston from Aeromotor along with three 4” x 40” spiral wound membrane model SE4040CZH from Osmonics were selected and installed at an arsenic and fluoride underground water source with 897 ppm of total dissolved solids (TDS). An eolic energy buffer was designed and installed between the wind mill and the RO membranes. The eolic energy buffer controlled operating pressure at wind speeds from 0 to 40 km/hr. The buffer system was able to operate water pressure between 3.75 and 4.5 bar. The minimum wind speed that obtained the lowest operating pressure (3.75bar) was 10 km/hr with a water production of 45 l/day. The maximum useful wind speed was 18 km/hr with a maximum operating pressure of 4.5 bar and a maximum water production of 70 l/day. The pilot eolic RO averaged in a 12 month period a wind speed of 8.46 km/hr, and the regulate operating pressure was an average of 4.12 bar with an average water production of 1000 l/day and 49 ppm of TDS. No external energy was needed in the desalination process aside from eolic energy. Energy savings from the use of eolic RO are 2731 Kj/m3. The Eolic Energy Buffer System regulates inlet pressure at set point allowing commercial wind mills and reverse osmosis membranes to be connected and operate with regular maintenance. The Eolic Reverse Osmosis system represents a feasible, reliable and sustainable small scale desalination option for rural areas.