Limestone and goat dung in acid mine drainage treatment

Abstract

Acid mine drainage (AMD) is a major problem nowadays to the environment because it causes acidic water and high heavy metals content. In this study, AMD samples were obtained from a tailing pond of tin mine in Perak. The pond is the recycle water system of the tin ore processing plant and has pH values in the range of 2.5-2.8 and high heavy metals and sulphate contents. This can damage the equipment in the mine such as water pump. The AMD samples from this location were treated with two different materials, namely limestone and goat dung fertiliser. Limestone was used as neutralising material for acidic water and to reduce the heavy metals content. Goat dung fertiliser was used in reducing sulphate in the AMD sample. Four different methods were carried out based on the material used. For the first method, 500 mL of AMD sample was allowed to flow through limestone layered column. The four different limestone sizes used were in the ranges of 2-4 mm, 1-2 mm, 850 pm - 1 mm and 425-850 pm. For the second method, 500 mL o f AMD sample was allowed to flow through organic fertiliser layered column. For third method, 500 mL of AMD sample was allowed to flow through organic fertiliser and limestone layers. For fourth method, 500 mL o f AMD sample was allowed to flow through limestone and organic fertiliser layers. Single batch column technique was used in all experiments. For each experiment, the permeate was collected every 15 min, 30 min, 45 min, 60 min and 75 min. The results show that pH values obtained in all of the experiments increased after treatment in all methods. The highest pH obtained was 7.17 ± 0.01 by using 300 g of organic fertiliser with 60 min retention time. The lowest sulphate concentration obtained was 666.50 ± 92.63 mg/L by using Method 3 with a ratio of 50 g organic fertiliser to 50 g limestone and retention time o f 30 min. The concentrations of heavy metals such as arsenic and chromium were reduced and complied with Standard A and Standard B of the Environmental Quality Act 1974. All methods used were able to increase pH and reduced sulphate concentration. Methods 1, 3 and 4 can reduce heavy metals such arsenic, cadmium, nickel and zinc. Among these methods, Method 3 is the most suitable method in treating AMD.