PART 1: WHAT HAPPENS WHEN IT RAINS?
MANILA, MARCH 25, 2009 (STAR) STAR SCIENCE By Michelle C. Almendrala, Ph.D. - (First of two parts) The ferocious effect of continuous heavy rains is always associated with massive flooding in Metro Manila, and several provinces of the Philippines. However, there is another equally important problem brought about by moderate to heavy rains. This is water pollution.
The principal environmental issues associated with rain are the impacts to surface water (http://en.wikipedia.org/wiki/Groundwater and http://en.wikipedia.org/wiki/Soil) through the transport of water pollutants to these systems. As it rains, the water runs off the surfaces of buildings, houses and streets — this is known as urban runoff. The rain, therefore, will pick up contaminants such as oil, grease, petroleum (http://extoxnet.orst.edu/faqs/safedrink/metals.htm and http://extoxnet.orst.edu/faqs/safedrink/microorg.htm), bacteria and viruses, and toxic chemicals from automobiles, among others. Urban runoff is recognized as a significant source of contamination to water. When runoff flows along the ground, it can carry (http://en.wikipedia.org/wiki/Soil_contamination) soil contaminants such as (http://en.wikipedia.org/wiki/Pesticide) pesticides, in particular herbicides (http://en.wikipedia.org/wiki/Herbicide), insecticides (http://en.wikipedia.org/wiki/Insecticide) fertilizers (http://en.wikipedia.org/wiki/Fertilizer) and excess nutrients such as nitrogen and phosphorus. These contaminants usually come from agricultural land and even from our own washing water used for bathing, for washing clothes and dishes, and for cleaning our houses and workplaces.
The detergents we use for washing contain phosphorus, which is a nutrient that can cause algae to grow too fast and have the potential to degrade water quality. Rain or water runoff can also carry human wastes, as well as animal wastes, which contain disease germs and parasites. Wastes from factories and industries, such as the mining and smelting industries, contain poisonous and harmful chemicals that do not break down. These can go on poisoning the environment for a long time. As the rainwater runs off, the chemicals dissolve and flow into septic tanks, waste treatment plants, streams or lagoons. These contaminants can also slow or stop the microbes that would otherwise break down and purify organic wastes, making other water pollution problems worse. Therefore, when it rains, all these contaminants are carried by rainwater into rivers, lakes, streams and oceans (surface water). Also, a portion of the rainwater or runoff seeps into the ground water where the pollution can get into wells and springs. As a consequence, our source of drinking water, the surface water and groundwater, will be polluted.
Chemicals from water runoff pose a potential threat to human health and an even greater threat to aquatic organisms. Polluted water runoff can have many adverse effects on plants, fish, animals and people. For instance, the world’s poorest population in Bangladesh is confronting the accidental poisoning of as many as 77 to 95 million of its 140 million people with arsenic-contaminated drinking water. The epidemic of arsenic-related cancer has just begun (Hussam et al., 2008). The reason for the groundwater contamination is the use of arsenic as fertilizer to soil. Farmers were adding arsenic at 20-30 mg/kg (http://www.sos-arsenic.net/english/tsp.html) and a very high amount of uranium as fertilizer to soil two to three times a year (two to three crops, mainly rice) for more than two decades that possibly caused ground water contamination (SOS, 2008). Thus, the arsenic dissolved in rainwater and then percolated through the aquifer over several years.
Human wastes, which are mostly nitrogen compounds, which get into drinking water, can turn into nitrites that have been linked to cancer in humans. Another effect of contaminated drinking water results in various water-related diseases and ill health such as cholera and typhoid. The seasonal rains could bring a cholera and/or typhoid epidemic. Just recently, a cholera epidemic broke out in September 2008 in Zimbabwe’s capital, Harare, and caused the death of about 700 people. Sixteen thousand cases of cholera were recorded due to lack of clean water. It was reported that the sewerage system collapsed and the uncollected garbage was burned and allowed to rot in the streets, thus, causing the drinking water contamination. When it rains, all the filth from the garbage and large pool of raw sewage are running in the streets, and flowing into people’s wells or other contaminated sources like rivers.
(To be concluded)
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Dr. Michelle C. Almendrala is a faculty member of the School of Chemical Engineering and Chemistry, Mapua Institute of Technology; an associate member of the Philippine-American Academy of Science and Engineering; a member of the Philippine Institute of Chemical Engineers; a member of the Water Environment Association of the Philippines Inc.; and a member of the Association of the Water Environment Federation, USA. She was selected as a principal candidate for a Fulbright Scholar Advanced Research award in the United States during the academic year 2009-2010 for her research on “Recycling of Biobutanol Fermentation Broth by Membrane Ultrafiltration” at the Department of Chemical and Biomolecular Engineering of the Ohio State University in Columbus, Ohio. Her research interests are membrane separation applications in wastewater treatment and recycling; rice bran oil extraction, fruit juice clarification and concentration by osmotic distillation using hollow fiber membrane. E-mail her at email@example.com.
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