In Situ Treatment of Acid Mine Drainage by Sulphate Reducing Bacteria in Open Pits: Scale-Up Experiences

Abstract

Over the past three years, Noranda Technology Centre (NTC) has evaluated the feasibility of using sulphate-reducing bacteria (SRB) to treat acid mine drainage (AMO), in a pit or an underground mine. Following an initial study conducted in batch flasks that determined major process parameters (residence time, temperature effect, nutrients and substrate requirements), a conceptual flow sheet was developed. In order to confirm the concept for full-scale application, the present study included screening and· selection of inexpensive nutrients and larger scale tests in a 280-L drum, a 160-L tall column and 5-L continuous reactors. The start-up conditions examined with drum tests included sediment formation (reactor inoculation methods and nutrient preconditioning), influent location and final effluent quality (e.g. metals, pH, BOD, COD, odor, etc.). The tall-column test (5 m) was conducted to define the reaction zone and the extension of H 2 S dispersion in the pit. Nutrient utilization and S balance were estimated by monitoring off gases in 5-L continuous reactors as well as effluent quality. Due to the low S0 4 conversion rate found at low temperatures (e.g. 4 to 10°C), which is found in the bottom of the pit, the amount of nutrients required to treat moderate strength AMO with a high flow rate was determined to be very high, causing technical and economical difficulties in full-scale application of the process. The process was recommended for low loading situations.

Passive Treatment of Acid Mine Drainage in Bioreactors using Sulfate‐Reducing Bacteria

“…Alternatively, less expensive organic carbon sources such as waste material from the agricultural and food processing industry have been assessed for their potential to sustain sulfate reduction. The alternative organic carbon sources may be selected between two groups of materials—cellulosic wastes and organic wastes (Kuyucak and St‐Germain, 1994). Generally, cellulosic wastes include sawdust, hay, alfalfa, and wood chips, whereas organic wastes include cattle manure, cow manure, horse manure, poultry manure, sheep manure, rabbit manure, granular or sewage sludge, peat, pulp mill, molasses, and compost (see Table 1).…”

Removal of sulphate, COD and Cr(VI) in simulated and real wastewater by sulphate reducing bacteria enrichment in small bioreactor and FTIR study

“…It was usually accepted that precipitation of metal sulfides occurred in at least 3-5 days (Kuyucak and St-Germain, 2006). A shorter HRT may not allow adequate time for SRB activity to neutralize acidity and precipitate metals.…”

Selection of permeable reactive barrier materials for treating acidic groundwater in acid sulphate soil terrains based on laboratory column tests

“…SRB are greatly limited by substrate availability and factors such as nutrient availability, sulphate availability, metal toxicity and pH are far less important (Logan et al 2005). Some PRBs utilise SRB because the reduction of sulphate is a sink for protons and therefore decreases the acidity of the groundwater and soil solution (Kuyucak and St-Germain 1994;Loy et al 2004). The oyster shells may host SRB, which will enhance the neutralising capacity of the oyster shells but also may increase the risk of biological clogging.…”

“…The formation of alkalinity was greatly enhanced by the dissolution of the oyster shells (Fig. 7), which buffered the incoming acidity and probably protected the bacteria (Kuyucak and St-Germain 1994). Figure 8 displays the variation in ORP with distance along the column at four different time intervals.…”