Engineering:Shade ball
A shade ball is a small plastic sphere floated on top of a reservoir for environmental reasons, including to slow evaporation and prevent sunlight from causing reactions among chemical compounds present in the water. Also known as bird balls, they were developed initially to prevent birds from landing in bodies of water.
History
Shade balls were originally known as bird balls, as they were developed initially to prevent birds from landing on toxic tailing ponds produced by mining operations.[1][2]
They have also been used by airports to prevent birds from being attracted to nearby drainage ponds, thus reducing collisions with planes.[3]
Usage by LADWP
Starting in mid-2009, the Los Angeles Department of Water and Power (LADWP) put about 400,000 balls in the Ivanhoe reservoir with the main objective of preventing the formation of a carcinogenic chemical, bromate, which forms when sunlight interacts with naturally occurring bromine and the chlorine added to prevent algae growth.[1][4] In the original release by the LADWP, there is no mention of water conservation as an objective and the project was planned for a five-year life span, until a Griffith Park project was completed. The reduction in evaporation led to an estimated savings of about 1.1 billion l (290 million US gal) of water in one year.[1]
Construction
The shade balls used in the Los Angeles project are made of high-density polyethylene (HDPE) with carbon black additive to make the balls opaque and protect the plastic from ultraviolet radiation.[5][6][7][8] Adding carbon black also prevents the formation of bromate, a suspected human carcinogen.[9][10]
They are about 4 inches (10 cm) in diameter, and are partially filled with water to avoid being blown by wind. HDPE plastic is commonly used for food and beverage containers as well as water distribution pipes.[5]
References
- ↑ 1.0 1.1 1.2 Oved, Marco Chown (November 12, 2016). "Shade Balls – Just Add Water". Toronto Star. https://www.pressreader.com/canada/toronto-star/20161112/282952449774508.
- ↑ Daigneau, Elizabeth (November 23, 2015). "L.A. Says Goodbye to 'Shade Balls'". Governing. https://www.governing.com/archive/gov-shade-balls-water-quality.html.
- ↑ Siegel, Robert; Harasick, Richard (August 12, 2015). "Los Angeles Unleashes 'Shade Balls' To Protect Reservoir Water Quality". All Things Considered. NPR.
- ↑ Vara-Orta, Francisco (10 June 2008). "A reservoir goes undercover". https://www.latimes.com/archives/la-xpm-2008-jun-10-me-balls10-story.html.
- ↑ 5.0 5.1 "Shade Balls: Sustainable Drought Prevention". Precision Plastic Ball. . Retrieved March 31, 2016.
- ↑ "Los Angeles Reservoir Covered With 96 Million Shade Balls to Conserve Water Amidst Drought" (in en). https://abcnews.go.com/US/los-angeles-reservoir-covered-96-million-shade-balls/story?id=33038319.
- ↑ Ferris, Robert (2015-08-13). "'Shade balls' protect LA water supply during drought" (in en). https://www.cnbc.com/2015/08/13/shade-balls-protect-la-water-supply-during-drought.html.
- ↑ Wagner, Laura (2015-08-11). "LA Rolls Out Water-Saving 'Shade Balls'" (in en). NPR. https://www.npr.org/sections/thetwo-way/2015/08/11/431670483/la-rolls-out-water-saving-shade-balls.
- ↑ "Potassium Bromate (Group 2B)". International Agency for Research on Cancer: Summaries and Evaluations. Canadian Centre for Occupational Health and Safety. http://www.inchem.org/documents/iarc/vol73/73-17.html.
- ↑ Kurokawa, Y; Maekawa, A; Takahashi, M; Hayashi, Y (July 1990). "Toxicity and carcinogenicity of potassium bromate – a new renal carcinogen". Environmental Health Perspectives (Environmental Health Perspectives) 87: 309–35. doi:10.1289/EHP.9087309. PMID 2269236.
External links
- Video of 2014 Shade Ball Deployment on YouTube
- Video "Why Are 96,000,000 Black Balls on This Reservoir?" on YouTube
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