Packed Flume

Design considerations for the limestone flume are discussed elsewhere.7 8 The flume is a 500 ft long vee-section channel filled with txH in. crushed limestone to a depth of about 3 in., designed to neutralize 2 gpm of pH 4.0 mine wastewater to pH 6.3. 

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Water neutralized with limestone and reagent solution was stripped of carbon dioxide by spraying, followed by settlement in a basin, then filtration through a dam of straw bales, except that effluent from the limestone-packed flume was not subsequently treated. A small copper cementacion unit was also operated. 

The autogenous mill initially neutralized mine wastewater by as much as 3.3 pH units to pH 8.4, a similar degree of initial neutralization to that observed in the limestone-packed flume, and exceeding the design neutralization from pH 4.0 to 6.3,... 

As the site is snowbound for about six months of each year, the treatment plant was designed to operate unattended for months on end. Unattended operation over short periods was demonstrated, though after the final inspection before winter the wastewater supply from the mine to the treatment plant was interrupted by rupture of the feed pipe under snow loading, which also crushed two sheds at the site. However, a flume packed with crushed limestone to neutralize mine drainage operated continuously through the winter under snowpack. 

Pearson, F., "Removal of Copper from Acidic Water in a Flume Packed with Crushed Limestone, Proceedings of Hazardous Materials Management Conference and Exposition, Disneyland Hotel, April 5-7, 1988, Sponsored by Association of Bay Area Governments, Oakland, Calif, pp. 431-441, 1988. 

Irnrr and retention time for droplrts to coalesce A pipe diameter is chosen that is large enough to present coalesced 1 droplets from shearing in accordance with the dispersion equation discussed in the previous installment. In effect, the unit grows a droplet distribution curve in the inlet stream that can then be treated in the tank or flume. Fig. 1 shows an ( installation using SP packs in a series of tanks Fig. 2 shows an installation in a series of compartments in a horizontal flume such as a barge bull or a pit. 

SP pack system. Number and size of tanks can be determined. Alternatively, dimensions and number of compartments in a horizontal flume can be specified. 

Step 5. Since flow is greater than 3,000 hwpd, SP packs in tanks arc probably nor attractive (unless surplus tanks are available). If system is on a barge, consider a horizontal flume. See Step 10 If SP packs are not used, and since d, is less than 30 microns, a flotation unit must be used. Proceed to Step 6 (Note Since <, is close to 30 microns, it may be possible to treat water without a flotation unit. The more conservative case is taken for this example.)... 

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