Challenges Associated with Quality of Soda Ash, Abijata Lake, Central Main Ethiopian Rift, Ethiopia

Abstract

Abijata-Shalla Soda Ash Share Company in the central Main Ethiopian Rift is producing soda ash (Na2CO3)by evaporating brine water from Abijata Lake. A study was undertaken to assess the challenges associated with the mining practices and quality of soda ash. Presently, 5000t of soda ash is produced annually with a grade of about 90% against the expected 20,000t with 97% grade. During fieldwork, a geological map is prepared and collected soil, trona, soda ash and water samples for chemical analysis. Water samples were collected from the lake and from different evaporation ponds. Soil samples were collected around the ponds and soda ash samples from the processing plant. All the samples were analyzed for major cations and anions in addition to pH and other parameters. The field and laboratory data suggest that the mining method, pond design, and the timing of transfer of brine water from one pond to another are the major challenges that are affecting the quality of soda ash. New pond design is suggested with minor modification to the existing design which is expected to increase the grade close to 97% Na2CO3.  Keywords: Abijata-Shalla Lakes; Brine water; Evaporation; Trona; Soda Ash; Ethiopia.