Lecture 17 Chapter 9 (cont’d) Waste Heat and other topics

Major Causes of Thermal Pollution use of water as a cooling agent soil erosion deforestation of shorelines run-off from hot paved surfaces

48% goes to environmental uses such as instream flows, wild and scenic river flows, required Delta outflow and managed wetlands. 41% is used by agriculture 9% is used by cities and industry. About 75% of California’s available water occurs north of Sacramento, while about 80% of the demand occurs in the southern two-thirds of the state. Groundwater provides about 40% of the state’s water supply. In dry years, that percentage can go as high as 60%. California - Water Resources

Fig. 9-8, p. 304

Table 9-5, p. 305

Fig. 9-9, p. 306

Effects of Warm Water on Aquatic Plant Growth Elevated CO 2 when coupled with elevated temperature and minerals can increase certain plant growth from 220% to 350% (Carbon Dioxide Science Magazine 2006) Thermal pollution from power plants, storm water runoff, and other sources can raise the overall water temperature of a lake or water body. In some instances, such artificial temperature rise enables certain plant species to become dominant, whereas prior to the artificial rise in water temperature, the same plant did not do so well (Moss 1959 and Allen and Gorham, 1973). Algae also seek the warmer sunlight-rich zone near the surface; the surface gives them all the sunlight energy they need to produce their own food.Algae The general rule for temperature and oxygen in water: warm water contains less dissolved oxygen than does cool water.

Effects of Thermal Pollution Thermal Shock –Detrimental to plant and animal growth –Can result in “fish kill” Thermal Enrichment –warm water from power plants may be used for irrigation to extend plant growing season in frost-prone areas –speed the growth of fish and shellfish for commercial production –melt snow on sidewalks –desalinate ocean water However, the harmful effects of thermal pollution seem to outweigh the beneficial ones.

Fig. 9-10, p. 307

Fig. 9-11, p. 308

Fig. 9-12, p. 310

Fig. 9-13, p. 311

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Waste Heat Adsorber For 40 o chilled water

Waste Heat Desalination Unit Boiling water: 650 kWh/m 3 Reverse Osmosis: 1.6 kWh/m 3 (2.25 to 2.75 kWh/m 3 for seawater)