1986-12-08_GENERAL DOCUMENTS - M1977493 (2)

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21 3 inches of tailings containing admixed sludge. The main root for the 11-inch jfi buried sludge layer had grown only 3.25 inches downward and had then sent out lateral feeder roots. The main roots in the plots with sludge layers at depths of 7 and 15 inches were much longer but grew in a circular manner, I , ; again only in the presence of the organic admixture. Conversely, the main root system for the plot with sludge at 3 inches grew down into and through the sludge layer to within 2 inches of the bottom of the tailings in the barrel. Table 3 clearly shows the much greater plant growth• attained with the ;1; sludge layer at shallow levels. '1. Pelletization of Tailings i Earlier tests indicated that a better root environment and soil aeration i :: was obtained by pelletizing the tailings. Pelletized material also appears well suited for use on tailing pond slopes, because the textured surface pro- I,. sides natural sites for plant growth. Therefore, a test series was made using a l.5-inch layer of pellets on top of tailings containing sludge layers buried 3 and 15 inches under the normal tailings surface. The pellets were minus-3/8-plus=1/8-inch size and contained, in percent, 92.4 tailings, 6.6 sewage sludge, and 1 chemical binder, either Coherex or Paracol TC 1842. Pellets were prepared in a rotary drum pelletizer and demon- strated good structural strength. The pellets contained the equivalent of 10.8 tons per acre of sludge in the top 1-1/2-inch layer, somewhat less than the maximum 15 tons per acre used in the top 3 inches of tailings as in previ ous tests. Approximately 1-1/4 inches of pellets were distributed over the surface of the plots , the seeds were planted, and the final 1/4-inch of pellets were used as a cover for the seeds. Seeds used on each plot included crested wheatgrass, Ranger alfalfa, rye grain, and alsike clover. A 2-inch rl . tomato plant was also transplanted into each plot. Two plots had sludge layers 4-1/2 inches under the top of the pellet layer. The other two plots ] I , were made up similarly but with the sludge layers at 16-1/2 inches under thet surface. Table 4 shows the number of plants germinating per 100 seeds 2 weeks +; after planting and the number surviving at the end of 10 weeks for each plot. TABLE 4. - Germination and survival of plants with buried sludge layers e� and pelletized cover, percent Type of binder. . . . . . .. Coherex Paracol 41 t Depth of sludge layer. 4-1/2 inches 16-1/2 inches 4-1/2 inches 16-1/2 inches Plant Germi- Sur- Germi- Sur- Germi- Sur- Germi- Sur- nations vivall nation vival nation vival nation vival t Crested wheatg rass. . . . 79 75 82 70 72 66 79 69 , Ranger alfalfa. . . . . . . . 57 49 67 42 70 55 58 38 Rye grain. .. . . . . . .. . . . 54 43 72 48 63 43 64 49 Alsike clover. . . . . . . . . 29 10 50 7 54 17 49 11 • Tomato..... . . . . . . . . . . . - 'Germination rate at 2 weeks after planting and the survival of plants after 10-week growth.