Desalination – the future solution to our water crisis

By Engr. Edgar Mana-ay

Water is still the very basic need of any economy but because of the COVID-19 pandemic, which tremendously reduced economic activities, demand for water was greatly reduced.

This summer should have been the new normal of abundant water supply (no malls, no restaurants) but as usual we are now experiencing water shortage.

As this writer have pointed out so many times in the past, Metro Iloilo can never rely on Tigum, Aganan and Jalaur rivers as its exclusive water sources. Another month more of summer days, water in these three rivers would reach the two inches deep and certainly cannot provide the 200,000 cubic meters per day (cmd) sufficient (pagusto pero indi patuyang) water for Metro Iloilo, sans the various deep and shallow wells that many residents are using.

At two inches water depth, the most that the three water processing plants – Flo Water in Jalaur River, Metro Iloilo Bulk Water Supply in Tigum River in Maasin and the newly contracted supplier of MIBWS, Mactan Rock in Aganan River – can produce only about 70,000 cmd, way short of at least 120,000 cmd.

Again, for the nth time, this writer has stated that as Filipinos, we don’t have the discipline and the political will to rehabilitate and improve the forests in Maasin which is the watershed source of Aganan and Tigum rivers that drain towards the sea.

Relying solely on Maasin watershed is an exercise in futility. Metro Iloilo Bulk Water Supply (MIBWS), the joint venture supply company of Manila Water and Metro Iloilo Water District (MIWD), is embarking on the right direction in finding out how much underground water do we really have in Iloilo that can add to the present supply.

But this is a very expensive endeavor because it requires scientific investigation such as Geo-resistivity survey and then drilling even though the outcome of water quantity is not sure. Drilling up to 300 ft. or more requires an expenditure of close to 2 million pesos. But it is encouraging to note that a very large subdivision in Pavia extending towards Sta. Barbara has successfully drilled water wells in excess of 300 ft. (a feat never done before in the area) and is producing potable water at a very modest of 400 cmd per well. It is an irony that Iloilo is located in the tropics and receives tremendous rainfall, yet suffers from perennial water shortage.

It is but natural that a country like Israel, which is in a dessert environment, suffers from perennial droughts, with its worst in the last 900 years happening in 2010. But these days, Israel now has surplus of potable water. The major contributor to this is the Sorek Desalination Plant 10 miles south of Tel Aviv which gets its supply of salt water a mile offshore of the Mediterranean Sea. It is the largest reverse-osmosis (RO) desal facility in the world, producing 410,000 cubic meters per day (cmd) of fresh water from salt water and supplies 1.5 million Israelite. that’s 270 liters per day per person which is quite reasonable considering the water scarcity in a dessert environment (in the U.S, it’s 600 liters of water per day per capita).

Desalination by Reverse Osmosis works by pushing saltwater into membranes (you don’t call it filters anymore) containing microscopic pores. The water gets through, while the larger salt molecules are left behind. (In Saudi Arabia because of tremendous oil resources, they just boil sea water at vacuum condition, then condense the water vapor; this method costs double than RO). But in RO, microorganism in seawater quickly colonize the membranes and block the pores and controlling them requires periodic costly and chemical-intensive cleaning. Such is the RO system at SM City where supply is brackish water from nearby deep wells but saltiness or TDS still ranges up to 3,000. TDS allowed by Philippine Standard for Drinking Water (PSDW) for drinking water is 500 while sea water can have a TDS of as high as 13,000 during summer. But water scientists at Israel’s Zuckerberg Institute for Water Research have developed a chemical free system RO using porous lava stones as its first line of filters to capture the microorganism before they reach the membranes. It is one of the many breakthroughs in membrane technology that made desalination more efficient and cheaper approaching cost of bulk water processing from rivers.

For the background of our readers, for as long as there is water, there will always be microorganism, the most common we tackle in our aquarium at home is algae. Those of us with aquarium as a hobby is familiar with the periodic and tedious cleaning to get rid of the algae that builds up with time. At the Israeli Sorek Plant, saltwater supply is now free of these algae or phytoplankton before it reaches the membrane system, thus saving a lot of operational cost.

Just to give our readers some idea on the cost of water you are consuming: a refilling station (the process used is also an RO) will charge P15 for a 20 liter container and that’s 75 centavos per liter. A half liter bottled water from the sari-sari store will cost P10 and that’s P20 per liter and this bottled water is the most expensive drinking water we are buying in the super markets and stores. Besides, we also litter the environment with these empty plastic bottles. MIWD bills us at an average of P22/cubic meter or 2.2 centavos per liter. A bulk water processing plant utilizing river water can produce potable water at the plant gate at 1.5 centavos a liter while a reverse osmosis plant in Iloilo City, whose source is brackish water (TDS not exceeding 2,000) can produce potable water at 8 centavos a liter.

The Sorek Desal Plant can produce water at 5 centavos a liter! It is strongly suggested that NWRB (National Water Resource Board), Metro Iloilo Bulk Water Supply, Mactan Rock and Flo Water send their representatives to Sorek Desal Plant in Tel Aviv, Israel to replicate such low-cost desalination process in our country.

We are an archipelago and we can locate a series of desal plants along our shorelines, thus saving on transmission costs. If we have to progress, we have to push our imaginations and ideas to reality. For according to Sean O’Faolain (1900-1991): “There is only one admirable form of imagination that is so intense that it creates a new reality, that it make things happen.”