ENVIRONMENTAL
CURRENTS Sea Water Desalination
Introduction of aluminum equipment may lead to new economies in sea water desalination processes. The exceptionally good heat transfer qualities of the metal, used successfully in other heat exchange operations involving sea water, suggest that aluminum tubing can be used to advantage in desalination plants, possibly at savings approaching half the price of tubing currently used. To demonstrate the anticipated lowering of both installation and long-term maintenance costs, Reynolds Metals Co. has been awarded a research contract by the Office of Saline Water, U.S. Department of the Interior, t o build and operate a pilot desalination plant at Wrightsville Beach, N.C. Construction will be handled by Aqua-Chem, Inc., of Waukesha, Wis. Small by comparison with the multimillion-gallon size of other projected desalination plants, the Reynolds pilot plant will have an initial daily capacity for converting 50,000 gallons of sea water into potable water, with a capability for scaling up as required, according to D. A. Fauth, Reynolds project director. The pilot plant features a 26-stage, singleeffect flash distillation unit that, through a series of pressure reduction steps, permits steam generation and distillation with significant heat economies. Government predictions that more than 7z of the nation’s water will come from the sea by the year 2000 point up the importance of continuing research and development aimed at more economical desalination processes. (See feature on page 124). Evaporation Losses
Evaporation losses from the Salton Sea in California will be determined in a two-year study by the Geological Survey (Department of the Interior). Purpose of the study on the 360-square-mile lake is to compare results with estimates based on evaporation losses from standard evaporation pans a few feet in diameter. USGS has estimated that 1.3 million acre-feet (433 billion gallons) evaporate from the Salton Sea annually. On the same basis, USGS estimates such losses from the Great Lakes at 100 billion gallons per year, equivalent t o almost half the 220 billion gallons withdrawn daily in the U.S. for municipal and industrial use.
Solid Wastes Field Laboratory Construction will begin early this year on the first Public Health Service field laboratory t o concentrate on solid waste pollution abatement. To be located on a 15-acre tract owned by the University of Cincinnati in a residential-commercial area of Cincinnati, Ohio, the facility will be used t o find methods for improving the management of municipal, industrial, and agricultural wastes under conditions reflecting common disposal practices in the U.S. Goals include the elimination of health hazards associated with unsanitary solid waste collection, storage, and disposal. Standards of sanitation and safety higher than those found in average community refuse disposal operations will be maintained at the new facility. Slated for study are control of air pollution from solid waste incineration, deterioration of refuse in the environment, design and operation of sanitary landfills, and control of groundland surface water pollution caused by solid waste. Volume 1, Number 2, Febriiary 1967
109
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110 Environmental Science and Technology
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ENVIRONMENTAL
CURRENTS Composting Municipal Waste
Coniposting municipal refuse and sewage sludge t o produce soil conditioners may create a new outlet for the disposal of modern society’s increasing mound of solid waste. The Tennessee Valley Authority, in cooperation with the U.S. Public Health Service and Johnson City, Tenn., has begun construction of a demonstration plant a t Johnson City to study the feasibility of coniposting as a niethod of waste disposal. The $750,000 project, financed by the Public Health Service, is scheduled t o begin operation this spring. Bricks from Discarded Silt
Face bricks from residues of sand and gravel washing operations near Washington, D.C., have been made in laboratories of the Geological Survey (Department of the Interior). The silty clay waste materials, a potential pollution hazard in local streams, may now offer builders a new supply of inexpensive brick. Polymer Coagulators
Polymeric coagulators and activated carbon filters are the key to a sewage and waste water treatment developed by Calgon Corp. The polymers coagulate and settle solids from raw sewage in the primary treatment process. This clarified water then passes over large filter beds of regenerable granular activated carbon that filter out the remaining suspended solids and adsorb the dissolved organic contaminants. Calgon says its process can treat organic wastes to a higher quality a t a lower cost than is possible with secondary treatment. The process improves chemical coagulation techniques for removal of phosphates. According t o Calgon, cities with only primary treatment facilities can, by using polymeric coagulants, remove 30 to 50z more polluting materials than can be removed by settling alone. Another advantage of the process is its flexibility-a plant’s capacity can be increased by reactivating the carbon more frequently or by adding carbon to the filters. Calgon says that the new process can be installed on one tenth the land and a t perhaps two thirds the cost of conventional plants. Dow Chemical, which started marketing polymeric coagulators in 1964, has also been actively promoting the use of such materials for primary treatment. This past year Dow and the city of Grand Rapids, Mich., undertook a joint effort to study a treatment system designed to operate with polymeric coagulators. Another use for polymeric niaterials will be explored by the research division of the Western Co. (Richardson, Tex.) under a $300,000 contract from the Federal Water Pollution Control Administration. The company plans to study the feasibility of adding such materials to combined sewerstorm lines to enable them to carry greater quantities of sewage during rains. The additives increase fluid flow in pipes by reducing turbulent friction loss. If the method proves feasible, demonstration tests will be conducted in the Dallas-Fort Worth area in mid-1968. Volume 1, Number 2, February 1967 111
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