Evaluating Effectiveness of Length of Closure in Remediating Coliform Contamination in Boracay Island

Author Information

David Caloza, University of the Philippines, The Philippines
Dolores Cleofas, University of Santo Tomas, The Philippines
Susan Abaño, National Water Resources Board, Qatar

Abstract

The international tourist destination of Boracay Island was closed by national authorities last April 2018 due to the persistent high coliform concentrations found in its beach waters. The cause of the contamination is identified as inadequate sanitation systems whose outflow goes to the groundwater. This water in turn leaks out to the sea. The rationale of the temporary closure is to allow natural mechanisms to clean the groundwater—mainly by the shutdown of all coliform contamination sources, coliform die-off and flushing via recharge of rainfall. The period of closure is six months. With a first order die-off rate of 0.03/day for coliform bacteria in karst soils, computer simulations show that the period of closure removes 99.4 percent of the contaminant-marker—adequate to bring the contamination down to levels that are acceptable for recreational waters. A further extension of six months would most likely bring the contamination below detection limits.

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• Category: Water and Sanitation

Posted by James Alexander Gordon

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