The plant was required to meet strict effluent limits that complied with regulatory and process requirements for downstream processing. After the initial 12 month period, the size of the pilot plant increased and a Sulf-IX™ unit treating up to 24 m3/hr was built and tested.
The process incorporated two stages:
Cation Exchange Circuit – selectively removed calcium from the plant feed using strong acid cationic ion exchange resin. The resin was regenerated using sulphuric acid, causing the sulphate to precipitate as gypsum. The gypsum was separated, filtered and shipped offsite for disposal. The cation circuit had to meet strict effluent limits dictated by downstream processing requirements including calcium concentrations below 20 mg/L, maximum turbidity of 50 NTU, and a pH between 3 and 4.
Anion Exchange Circuit – selectively removed sulphate from the plant feed using a weak base anion resin. The resin was regenerated using lime, causing the calcium to precipitate as gypsum. The gypsum was separated, filtered and shipped offsite for disposal. The anion circuit had to meet strict effluent limits that complied with regulatory requirements including sulphate levels below 500 mg/L.
The pilot results indicated that the Sulf-IX™ technology was capable of meeting strict effluent limits while delivering significant cost savings compared to alternative processes.
The operating cost of the cation circuit of the Sulf-IX™ plant was estimated to be about one-third that of a similar capacity soda ash softening and acidification system.
The operating cost of the anion circuit was affected by the efficiency of ammonium removal upstream of the anion circuit but offered a significantly lower cost of removing sulphate from the wastewater than a conventional membrane process combined with an evaporator-crystallizer for Zero Liquid Discharge (ZLD).