Natural filtration for Laguna de Bay eyed | Inquirer News

Natural filtration for Laguna de Bay eyed

/ 03:02 AM November 27, 2011

It was a laid-back rural scene worthy of a painting by Fernando Amorsolo: women chattering over their laundry and their children doing stunts and splashing in the shallow Molawin Creek.

But for University of the Philippines Los Baños (UPLB) environmental scientist and phycologist  Macrina Zafaralla it was an upsetting scene.  Her eyes had focused on one of the boys, who filled his mouth with water and gulped it down.


“Not a kilometer away (from these people) was a sewerage outfall,” said Zafaralla, aghast.

Disturbed by what she had witnessed and the dangers to the health of the children, Zafaralla in March 2009 embarked on “phytoremediation,” a process of using plants to filter the water flowing down a 7-kilometer stretch of the Molawin Creek in Los Baños, Laguna.


Molawin Creek is one of the 33 tributaries and rivers of the Laguna Lake. It carries all forms of wastes from Mt. Makiling, the university facilities, dormitories, piggeries, and residential communities all the way down the stream.

Polluted lake

To reduce the solid waste pollution in the creek, Zafaralla installed a structure of interlocked bamboo poles across the five-meter width of the creek. She then let grow a meter-breadth of water hyacinths, which she calls the Aquatic Macrophyte Biosorption System (AMBS).

The water hyacinths soak in the water and absorb the wastes, thus filtering the water that flows to the other side of the structure.

Basically it’s “a barricade that functions as a living filtering system,” she said.

Zafaralla introduced the AMBS at a forum of lake fishers organized by Kilusang Lawa Kalikasan (KLK) at the compound of the Laguna Lake Development Authority (LLDA) here on Nov. 19.

KLK is a nongovernment organization of fishermen that aims to improve the condition of the deteriorating inland body.


“No one will deny that the lake is polluted. But to what extent is it polluted? Is the fish still safe to eat? There is a need to look (into these),” said Deputy House Speaker and Quezon Rep. Lorenzo “Erin” Tañada III, who was the guest speaker at the forum.

Tañada has filed a Laguna Lake Conservation Authority Act in Congress.

The KLK tapped the science community to replicate the AMBS in other lake tributaries.

Fish galore

Based on Zafaralla’s findings, the AMBS was able to collect tons of solid wastes. The water, after passing through the system, became clearer. She noted that aquatic life was also restored.

“Before, it was very hard to find a single fish in the (Molawin Creek). But in two to three weeks’ time (after the AMBS was placed), we noticed that tilapia fingerlings grew abundant. It was ‘fish galore.’ The fish were as many as the raindrops from the sky!” Zafaralla gushed.

Village caretakers

Zafaralla first tested the AMBS on the Molawin Creek near a community of about 45 families in Sitio Riverside.

“There was really no fish before. If there were a few, people would scoop out even the fingerlings just to have food,” said resident Mario Macan, 28. With no other options, the men worked as garbage collectors and the women as vegetable and flower vendors.

Pleased to see the return of a food source due to the AMBS, the residents themselves volunteered to collect the garbage trapped in the water hyacinth filter.

Zafaralla also taught them to prune the hyacinths so they would not grow into a thicket that would clog the water flow, and to dredge the riverbed to prevent its “shallowing” due to the accumulated sediments.

Whenever the water rises or flash floods destroy the bamboo structures, residents know how to fix and put them back.

“Almost every day, someone checks the river and picks up the thrash. We now have an everyday supply of fish for our families,” said Macan.

New biopark

The UPLB in 2010 declared the Molawin Creek a biopark. The university is the caretaker of the tributary.

A foreign research institution recently pledged support to Zafaralla’s study on the creek’s water quality.

Zafaralla said the next part of her research will focus on the biological and chemical quality of the water filtered by the AMBS. The research will also find out whether the system can also trap toxic and non-solid wastes such as lead and oil.

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TAGS: Laguna de Bay, Laguna Lake, Laguna Lake Conservation Authority Act, Molawin Creek, University of the Philippines-Los Baños (UPLB), UPLB environmental scientist and phycologist Macrina Zafaralla
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