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Oxidation ponds.

Under favorable conditions of soil and climate, sewage, either raw or preclarified, can be treated by stabilization basins or oxidation ponds where it is retained for several weeks. During this period, the organic matter is oxidized by oxygen absorbed from the air and that produced in photosynthesis of algae in the sewage. So that full advantage may be taken of algae growth, the ponds are kept shallow, 3 to 5 ft deep, and design factors relate surface area and BOD values. North Dakota health officials found that a ten-acre pond should be provided for about each 1,000 population although this may vary with climate and other factors. It is generally recommended that the total oxygen loading not exceed 35 lb per day per acre of surface area or 1.14 lb per day per 1,000 sq ft.

Bottom sludge accumulations in ponds may be removed by a variety of ways. Equipment and techniques are discussed in Section C-10 of this manual. Measurement of sludge depths, volumes, and pockets in ponds is discussed in Section D-6 of this manual.

Aerated Ponds. The loading of oxidation ponds can be increased by installing aeration devices in them. Mechanical aerators as discussed in Section D-4, are available for this purpose.

The oxidation system of Air Diffusion Systems consists of a blower, PVC manifold, and specially formed and processed polyethylene tubing for aeration. Oil-less compressed air is distributed through the tubing, which is laid in a grid pattern on the bottom of the lagoon.

Instead of employing perforated plastic tubing, the tubing can serve as headers for "static" diffusers, erected at strategic points along the bottom of a pond. Manufacturers of such diffusers are given in Section D-4.

Wastewater treatment by aquaculture, which uses earthen ponds for secondary and advanced wastewater treatment is another method that has been used in various areas with some success. The ponds may be greenhouse Covered and stocked with plants and animals having the ability to utilize and destroy the organics or stabilize unwanted compounds. Refer to Section D-5 of this manual for additional information on this topic.

Pond Liners. Prefabricated asphalt panels are available as lining materials, sometimes combined with fiberglass reinforcement, plasticizers or plastic sheeting. Information on asphalt liners can be obtained from the Asphalt Institute. Polyester fibers have been used for reinforcing and stabilizing asphalt, promoting water tightness and reducing cracks.

Other companies furnishing pond liners include Colloid Environmental Technologies Co.; Environetics, Inc.; Exxon Chemical Co.; Fabricated Polymers Div., Fluid Systems; Gundle Lining Systems, Inc.; JPS Elastomerics Corp., Environmental Products Div.; MPC Containment Systems Ltd.; National Seal Co.; Occidental Chemical Corp.; Plastic Fusion Fabricators, Inc.; Poly Flex, Inc.; Reef Industries, Inc.; Fred B. Rivas Co.; SLT North America, Inc.; Inc.; Serrot Corporation.

Liner membranes reinforced with polyester scrim encapsulated between two layers of DuPont "Hypalon" are furnished by JPS Elastomerics Corp., Environmental Products Dept.

C.I.M. Industries Inc. has a seamless asphalt-extended polyurethane membrane that can be squeegeed, rolled, or sprayed onto fabric reinforcement.

Field seam welders and a portable seam testing tools are available from National Seal Co.: Gundle Lining Systems, Inc.; and SLT North America, Inc.

The synthetic resins and polymers, used to manufacture thermoplastic materials, have been perfected to make possible a relatively inexpensive, quickly applied liner, capable of withstanding the conditions encountered in water storage. These include polyvinyl chloride (PVC), chlorinated polyethylene (CPE), chlorosulfonated polyethylene, polyisobutylene (butyl), ethylene propylene diene monomer (EPDM), polychloroprene polymer (neoprene), polyolefin, and others. The application of these materials interchangeably or without an understanding of their properties should be avoided.

Manufacturers of the resins, polymers and reinforcing materials, the basic sheeting material manufacturer or calenderer, materials, and the fabricator of the finished reinforced product are all interested in the end use of their products and can provide guidance as a result of years of experience. Also, many firms have had extensive and valuable experience in the installation of membranes. The consulting engineer and the user armed with adequate knowledge of local conditions, can obtain information from such firms, prepare the site and foundation, and select an experienced installer.

Major manufacturers of polymers and resins, sheeting or calender rolls, and fabricators of finished liners are given in Section C-8.

True Temper Corp. furnishes a rubber-backed fabric for oily wastes. Environetics, Inc. can furnish the liners for the containment of liquid sludge and other wastes. SLT North America, Inc. produces liners for various uses including aeration lagoons and other waste treatment applications. Shelter-Rite, Div. of Seaman Corp., makes a chemical and oil resistant fabric.

Impervious clay or commercially prepared mixtures of clay and bentonite provide a seepage barrier that can be effective for creating oxidation ponds and lagoons. American Colloid Co. furnishes such material, known as "Vol-clay." Other suppliers of bentonite and similar materials are The Soil Stabilization Products Company; Wyo-Ben Inc.

Baffles. Floating baffles to prevent-channeling and create a turn-over effect by using top and bottom flow patterns are furnished by Containment Systems; Environetics, Inc.; Oil Mop, Inc.; Slickbar Products Corp. Weirs and baffles for wastewater ponds are also produced by Franklin Miller, Inc.; MFG Water Treatment Products Co.; Pat Lindsay Associates, Inc.; Plasti-Fab Inc.; ThermaFab, Inc.

There are times, however, when it may not be practical or economical to provide separate storm and sanitary sewer facilities. One method of getting around separation is to provide temporary storage facilities for the combined overflow. During dry weather and at times of low flow, the combined overflows can then be treated.

The design of polishing ponds is described in a series of articles by Dr. Linvil Rich. Refer to the indexes of PUBLIC WORKS.
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Title Annotation:Water Pollution Control
Publication:Public Works
Date:Apr 15, 1995
Words:935
Previous Article:Activated sludge processes.
Next Article:Biological filters.
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