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(Figure 4-2). Each unit was continuously fed a mixture of groundwater and molasses (as a <br />• cazbon source). The ratio of molasses to sulfate content was varied so that an optimum cazbon to <br />sulfate ratio could be determined. Nutrients such as nitrogen and phosphorus were supplemented <br />to ensure adequate organism growth. <br />The bench-scale study began by inoculating the fixed media columns with a mixture of landfill <br />leachate and anaerobic sludge obtained from a municipal anaerobic digester. The columns were <br />then fed groundwater from BF-2, which was supplemented with mo]asses and nutrients at a rate <br />of 2 liters per day. This resulted in a hydraulic retention time in the reactor of approximately 1 <br />day. Effluent was recirculated at a rate of 100 liters per day. The gas generated in the anaerobic <br />column was first routed to a caustic scrubber to remove sulfide and then allowed to bubble <br />through the effluent chamber, thus allowing more hydrogen sulfide gas to be stripped off and <br />scrubbed (Figure 4-2). Excess gas was vented to the atmosphere. <br />Table 4-2 summarizes the operational pazameters of the three columns. Following a short <br />enrichment phase, where sulfate reducing bacteria and fermentative bacteria were allowed to <br />attach to the fixed-bed media, an acclimation phase was initiated. During the acclimation phase <br />(which is on-going), samples of the effluent were collected and analyzed for sulfate, manganese, <br />TDS, pH, sulfide, alkalinity, and total organic cazbon. Data from the acclimation phase aze being <br />analyzed to determine if the colunms have stabilized in terms of sulfate reduction and cazbon <br />removal. Data collection will continue in order to complete the determination of pertinent <br />kinetic and design parameters. Table 4-3 summarizes effluent data collected through March 10, <br />1999, and Figures 4-3 through 4-7 depict trends in effluent TOC, sulfate, TDS, pH, and <br />manganese with time. All data shown in this report represent system performance during the <br />acclimation period and aze not indicative of pseudo-steady state conditions chat would be <br />expected during full scale normal system operation. Therefore, system performance would be <br />expected to improve as the columns reach adequate acclimation. <br /> <br />Mountain Resources, In[. <br />p:11002671repaRSlmarchrprlrrl6wrrmngrmar[h.dac 52 <br />March 11, /999 <br />