Pilot Results of the Sulf-IX™ Process

Pilot results which have been previously reported (Bratty et al, 2008) demonstrate that the process is capable of meeting low effluent targets, while the formation of solid gypsum during the regeneration step can be controlled, and blinding of the resin beads can be avoided, resulting in long resin life. More recent testing has continued to confirm Sulf-IX™’s capabilities, including a detailed study of the use of the cationic stage of Sulf-IX™ as a stand-alone softening step which demonstrated calcium effluent concentrations below 20 mg/L.

Sulf-IX™ Used for Water SofteningOne of the advantages of the Sulf-IX™ technology is that in the right application the cationic and anionic stages can be operated independently. For example, the cationic stage can be used as a stand-alone water softening system for the removal of calcium or the anionic stage can be used to treat a stream of dilute waste sulphuric acid. Using either the full Sulf-IX™ Process or one of the stages independently has the benefit of reducing the TDS of the treated water without producing a concentrated liquid waste stream.

Metal Refinery Case StudyAn intensive piloting study was run on the waste water from a metal refinery with the intent of replacing the soda ash softening circuit with a cationic stage Sulf-IX™ circuit. When compared to a conventional soda ash softening circuit this offers a number of benefits, particularly upstream of a membrane process. Reviewing reaction (2) above, it can be seen that the calcium ions which are removed by the system are replaced by hydrogen ions, resulting in a lowering of the pH. Since membranes generally require acid addition in order to lower the feed pH, this pH adjustment due to Sulf-IX™ is a benefit to the system. Conversely, a soda ash circuit replaces the calcium ions with sodium ions. The sodium ions do nothing to reduce the pH, and since the charge balance requires replacing every calcium ion with two sodium ions the TDS contribution in mg/L is increased by a factor of 1.15 from the calcium to the sodium. Thus, as a result of replacing the soda ash softening with Sulf-IX™, the TDS loading on the membrane is lowered, resulting in longer membrane life, less brine production, and the elimination of the acid addition for pH adjustment. The net operating savings for a 68 m³/hr facility are calculated to be approximately US$4.20/m³.

CONCLUSIONS

As environmental regulations for the mining industry become stricter while commodity prices soften, industry leaders are seeking new technological approaches in order to stay competitive. Two significant water treatment technology platforms have been developed that can enhance environmental compliance and deliver lower life cycle costs for water treatment, namely: 1) the BioSulphide Process® and ChemSulphide® Process for water treatment and concurrent base metal recovery and 2) the Sulf-IX™ group of technologies for Ca/ Mg hardness and sulphate removal from mining wastewaters for water discharge or for recycle. These technologies can provide environmental and economic benefits compared to conventionally used technologies. The BioSulphide® and ChemSulphide® processes produce saleable metal products and clean water that can be re-used or safely discharged while reducing or eliminating the quantity of waste sludge produced. The Sulf-IX™ technology removes sulphate from wastewater without the production of waste brine and with reduced electricity consumption.

The sulphide-based processes have been demonstrated at eight operating commercial plants with flow rates up to 1,000 m³/hr and sulphide demand up to 3.7 T H₂S per day. The sulphate removal processes have been demonstrated under extensive pilot testing over several years. The sulphide and sulphate technology platforms may be integrated with conventional lime treatment, to provide a sustainable water treatment alternative to conventional practice.

APPENDIX I

Date: 2016-04-22; view: 1153