Abstract

Permeable reactive barriers (PRB) are a system for the treatment of ground waters used in the decontamination of acid mine drainage. In this technology, the reactive material is placed as a barrier in the subsoil, and the sulphate, metals and acidity are removed by the metabolic activity of the Sulphate Reducing Microorganisms (SRM). The substrates of the PRB must be economical and provide organic material which favors microbial growth. In this research, biological batch reactors were used to evaluate SRM activity in 10 organic mixtures with different concentrations of: Bio solids obtained from a wastewater treatment plant, fish bone-tissue, and bark compost and zero-valent iron. The mixtures were incubated at 30 +/- 2 degrees C for 47 days. To indicate the sulphate reduction pH, H2S, SO42-, redox potential and alkalinity were determined. The total numbers of microorganisms were determined by epifluorescence, and the numbers of SRM were determined by MPN. The chemical and microbiological results indicated that the mixtures with the greatest concentration of compost, and with presence of bio solids and zero-valent iron, presented higher SRM activity. Reactors with only a single source of organic material proved less effective in the treatment of acid mine drainage.