Fluidized Bed Bioreactor Technology: New Options for Selenium-Containing Mining Waters

摘要

A total of six pilot programs have now been successfully conducted using biological fluidized bed reactor (FBR) technology to study the removal of selenium (Se) from surface waters and wastewaters at various facilities in the US and Canada. This FBR technology has been utilized in the same anoxic mode for similar service in the reduction of oxyanions including perchlorate, nitrate, and various metals, for decades at a variety of full-scale installations. It has recently been shown that some of these long-operating installations have also been removing Se throughout their operating period. Flow rates of such operating systems have ranged to 6,000 gpm, and total removal of oxyanion contaminants has been as high as 5,000 lbs/day. Nevertheless, the most recent testing for Se treatment expands the matrix of operating data already available to cover applications with low feedwater temperatures, high nitrate concentrations, different electron donors, and twostage system design. Each of these factors is highly relevant to surface water treatment from mining operations. The most recent designs for full scale FBR systems, some of which are now being installed, address very high (above 2,500 gpm) and very low (less than 100 gpm) glow rates, and flow rates and concentrations of Se and nitrate that may vary greatly on a seasonal basis. All such testing, even with wide ranging ratios of Se to other oxyganions, has indicated less than 5 μg/L of total Se is achievable in the effluent following conventional solids separation. Testing has shown the value of conducting optimization using efficient electron donors, as well as the value of heating and heat recovery, one stage versus two stage configurations, and other design factors. the value of conducting optimization using efficient electron donors, as well as the value of heating and heat recovery, one stage versus two stage configurations, and other design factors.