Wed, Nov 14, 2007 - Page 4 News List

EPA system stops reservoir algae

By Meggie Lu  /  STAFF REPORTER

The Environmental Protection Ad-ministration (EPA) Environmental Analysis Laboratory (EAL) reported yesterday at a press conference the preliminary success of an artificial intelligence (AI) system capable of monitoring and preventing the formation of microcystis algal blooms, a toxic algae found in reservoirs.

Microcystis occurs naturally in fresh water, EAL Director-General Wang Pih (王碧) said, adding that the organism most commonly blooms in warm and nutrient-rich waters.

"While traces of microcystis pose no health threat, microsystis-dense drinking water releases microcystin into the liver and may cause health problems or even death," Wang said, citing a 1996 incident in Brazil where a group of dialysis patients died after consuming microcystis-contaminated water.

"The WHO states that a microcystis-density of over 10 parts per billion [ppb] is a sign that an algae bloom will form, so preventative strategies should be deployed," Wang said.

The monitoring of microcystis density is a race against time, EAL's Assistant Research Fellow Mike Yen (顏榮華) said, because, "Algae monitoring is traditionally done by regularly transporting water samples to the lab and analyzing them with Liquid Chromatograpy Mass Spectrometry (LCMS) equipment."

"By the time we detect the density to be over 10ppb, an algae bloom may form within 24 hours," he said.

The AI system is a cost-efficient way to monitor microcystis, since it costs NT$400,000, compared with NT$10 million (US$310,000) for the LCMS, and can detect real-time algal density, he said.

"The AI system utilizes a chlorophyll alpha sensor strategically placed in the reservoir where microcystis density is highest, and wirelessly transmits data to EAL every second" said EAL assistant research fellow Huang Ren-guei (黃壬瑰). Huang said that since chlorophyll alpha is found in all algae, an increase indicates an increase in the water's algal density.

However, since all algae contain chlorophyll alpha, an increase would not necessarily come from microcystis, Huang added.

"The photosynthesis process of microcystis comes to the rescue," Huang said, "because it makes the water-surface density of microcystis different during the day and night."

During the day, air is pushed out of the algae causing them to sink, allowing them to feast on nutrients at the bottom of the reservoir.

During the night, algae float to the surface of the water, she said.

"When the chlorophyll alpha-density is over 6ppb and the day-night difference over 2ppb, we can be quite sure that the increase is due to microcystis," she said.

The lab can respond by disturbing the water surface or by releasing water where the algae are accumulating.

"Taiwan is lucky in that the microcystis-density in our water reservoirs has historically been very low, however an accurate and fast alarm system can help us maintain this record," Wang said. "We hope to use the system in other reservoirs around the country."

This story has been viewed 1857 times.
TOP top