Table 6 Summary of treatment options available for coal seam gas co-produced water (© Copyright, SKM 2011). Treatment option Description Contaminant removal Suitability/Application Limitations Additional process requirements Waste Membrane Desalination (RO) Water subject to high pressure through a semi-permeable membrane for separation of contaminants Broad constituents including salt, heavy metals and trace organic matters Well-suited for ranges of dissolved contaminants, including TDS, heavy metals and organics Stringent required. High energy demand. May not remove all contaminants to minimum levels. May make water too clean for receiving environment. Multi-media or membrane filtration. Post-treatment, including chemical adjustment (for SAR). Ion exchange for improving recovery High concentration brine Electrodialysis (ED) and Electrodialysis Reversal (EDR) An electrochemical process in ions migrate through membranes as a result of their attraction to two electrically-charged electrodes Broad constituents, including salt and heavy metals Well-suited for removal of TDS, mainly for charged contaminants, including and heavy metals No removal of uncharged forms of contaminants. Not economical for feed TDS > 4000 mg/L. Filtration – for SS removal. GAC/Advanced oxidation/wetland for the removal of uncharged forms of contaminants High concentration brine Thermal Desalination Water subjected to a phase change for purification Broad constituents, including salt, heavy metals and trace organic matters Well-suited for ranges of dissolved contaminants, including TDS, heavy metals and organics High energy demand unless heat source is already available. Post-treatment, including chemical adjustment High concentration brine Ion Exchange Charged resin replaces conductive salts with replacement ions (e.g. H+ and OH-) Targeted contaminant removal Not practical for gross TDS removal. May be suited for reduction of targeted contaminants and/or for the desalination processes No reduction in salinity. Irreversible organic matter adsorption. None Regeneration fluid with high salt content
Advanced Oxidation Generation and use of hydroxyl radical for destruction of trace organic contaminants and micro-organisms Microorganisms and trace organics Well-suited for to target specific trace organic contaminants as necessary No reduction in salinity. Effectiveness highly influenced by contaminant levels. None Granular Activated Carbon Adsorption of dissolved organics onto activated carbon Trace organics and heavy metals Well-suited for as necessary No reduction in salinity. Blockage of media by solids. Ineffective at high organic concentrations. Filtration – reduction of suspended solids required Spent GAC Clarification Removal of suspended solids via gravity/floatation Suspended solids and Well-suited for for subsequent filtration process and provides ad hoc removal of excessive suspended solids No reduction in salinity Captured solids and coagulant residuals Filtration Suspended solids removed by filtering media or membrane Suspended solids Well-suited as a to remove suspended solids for desalination No reduction in salinity Screening required for gross solids Waste backwash water with high suspended solids content
Wetland Biological removal and plant uptake of nutrients and minerals. Sorption by the sediments in the wetland Nutrients, organic matters and heavy metals Well-suited for product polishing to remove trace elements/nutrients prior to discharge Unfeasible for salinity reduction. Large footprint. primary treatment Vegetation clippings/ periodical removal of sediments
surface aquifers Poor quality water could contaminate aquifer. hydrocarbon content (10 mg/L). and in the Amadeus Basin (Northern Territory) (RPS 2011). Off-site disposal facility Risk partially transfers to licensed operator of disposal facility Transportation costs may be large. No beneficial use, unless the water is treated and sold on. Suitable depending on proximity to production areas and economics. In use. For example, AGL Camden Gas Project (AGL 2012). Agricultural use Livestock watering Beneficial use for regional industry May affect animal health and production if water quality is not suitable. Suitable for certain livestock depending on quality and proximity to production areas. In use. For example, Energy provides co-produced water to local beef cattle feedlots (Arrow Energy 2012a; RPS 2011). Irrigation Beneficial use for regional industry May affect soil structure and crop yield. Dependent on water quality. Treatment may make the water too expensive for farmers to use. In use (RPS 2011). Industrial use Coal mine use Beneficial use (e.g. dust suppression, truck washing, haul and pit road water) Transport costs may be shared transportation costs to coal operations. Suitable depending on proximity to production areas and economics. Opportunity to costs with coal operator. In use. For example, Arrow Energy provides untreated co-produced water to the Wilkie Creek coal mine for its coal washing plant (Arrow Energy 2012a; RPS 2011). Water cooling tower Beneficial use for regional industry Transport costs may be shared May require water treatment or capital expenditure for infrastructure conversion to accommodate lower water quality. Suitable depending on proximity to production areas and economics. In use. For example, at the QGC Condamine Power station water is used for cooling and steam production (RPS 2011). Fire protection Beneficial use for regional communities Requires storage facilities close to regional townships. Suitable depending on proximity to coal seam gas production areas and economics.
Urban use (town supply) Beneficial use for local communities Treatment required. Limited longevity of supply (20 years) may offset economic viability of investment. Suitable depending on proximity to coal seam gas production areas and economics. Proposed. For example, Chinchilla Weir and Dalby TWS. Surface waters Provides increased flows for waterways suffering depleting water flows Potential erosion of banks. Difficult to to natural flow rates. May contaminate soil, water course and ecology if not treated to an appropriate level. Limited due to sensitive nature of surface water systems. In use. For example, the Fairview operation in the Bowen Basin (RPS 2011; URS 2009a). Historical approvals have allowed a constant discharge to water courses. More recent assessments have considered a variable discharge, in order to maintain natural flow variability. Ocean outfall Almost unlimited capacity to receive water (depending on the quality) Poor quality water could contaminate the marine ecosystem. of treating water may make option unviable. Transportation costs may be large. No beneficial use. Suitable depending on proximity to coastline and economics. Dependent on quality. consideration as an emergency or alternative disposal option. Evaluation of this method of disposal is currently very limited.