Friday, August 17, 2007 Speak out: Desalination plant at SRP By ENGR. Soekarno Tecson USC Class 75
THE utilization of RO desalination system at the South Road Properties (SRP) is a significant step in developing a safe, sustainable, drought-proof, cost effective and environmentally friendly water supply alternative.
It is just the right time to take advantage of the continually developing membrane technology, which has been regarded as the water treatment technology of choice in a wide variety of situations around the world.
However, there are few points worthy of comments:
--System Design. Is the present RO installation at SRP designed to process brackish water or seawater? Both processes may appear the same but actually very much different in design configurations, fixed and operating costs, and specifications on materials of construction.
Brackish water designed system definitely cannot be used to desalinate seawater.
--Proposal to sell 20,000 cu. m. per day desalinated water to MCWD. Is this the projected surplus from SRP’s potential RO feed water source?
If this will come from an RO processed brackish water to be sourced out from Pond A, the required raw water volume at 60 percent normal recovery rate for brackish water desalination system is 33,333 cu.m. per day.
And at 0.50 meter average pond depth, this will be equivalent to 66,666 square meter or roughly 7.0 hectares per day of impounded water. This means the existing Pond A could easily run dry in about a week unless it is proven to be sitting on underground spring that assures continuous recharge.
--Operating capacity. With the 700 cu. m. per day operating capacity of the existing RO installation, it will require about 30 more installations of the same size to supply the 20,000 cu. m. per day surplus requirement.
Frankly, the P26 million facility that can produce only 700 cu. m. per day is rather expensive unless there are some reserved and preserved RO trains inside ready for hookup and increase the current capacity four times.
--Deep well water source. Considering the site of the proposed 15 water wells which will be on a reclaimed sea bed, chances of extracting brackish water is less against borehole situated along the original edge of the shore, where the seawater-freshwater interface is normally occurring.
High salinity RO feed stream would mean complete change of system design since a brackish water RO system will become useless if the feed stream is approaching 30 percent of the seawater salinity, say 10,000 ppm.
--Overall viability. If well kept, brackish water desalination approach would be more viable than the proposed gigantic pipeline from the North.
However, to make it more convincing, it would be best to show to the consuming public the results of the MCWD study on the quality of desalinated brackish water infused into their distribution network in Cordova and part of Mactan Island.
