A field trial of seeded reverse osmosis for the desalination of a scaling-type mine water

Abstract

Conventional membrane desalination processes are limited when applied to waters which contain high concentrations of scaling salts. The processes are either severely limited on recovery or require expensive and difficult pretreatment to prevent scaling of membrane surfaces. Problems with scaling can be overcome with the use of seeded systems. This paper describes the evaluation of a seeded reverse osmosis (SRO) pilot plant to desalinate mine water which is nearly saturated with calcium sulphate. The pilot plant had a capacity of 5 m3/day and was operated for a period of 5000 hours, with 92–96 % water recovery. Tubular modules were necessary throughout the tests to allow recycling of the calcium sulphate slurry, which contained 2–6 % suspended solids. The cellulose acetate membranes performed satisfactorily and the results of salt rejection and membrane productivity are discussed. The SRO unit was operated with minimal pretreatment and there has been no evidence of membrane scaling by calcium sulphate or fouling by contaminants present in the mine water.