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Reframing the perception of by-product water

Wednesday, 20 May 2015

Combining traditional engineering with ecological principles for sustainable development to the management of by-product water in oil, gas and mining developments can provide superior environmental and community outcomes at significantly lower cost, with the performance rigour of hard engineering approaches.

On a number of fronts around Australia, oil, gas, mining and other industries are working in collaboration with land managers and communities on sustainable water management approaches to realise direct cost savings in an environmentally sustainable way, signaling a new era of co-existence with regional communities.  Verterra has played a key role in a number of these projects. 

Globally, water resulting from a wide variety of oil, gas, mining, industrial and municipal processes is treated as a waste product that requires processing via a water treatment plant prior to impoundment in storage ponds or discharge to the environment.  

Successful treatment isn’t just about “moving pollutants around”

While water treatment by desalination to a standard suitable for discharge solves one issue, it creates another by producing a concentrated brine by-product.  As stated by noted environmental scientist, Bill Mitsch, technological solutions to waste water treatment simply “move pollutants around in a kind-of shell game” resulting in secondary problems of a larger scale.  

For example, tailings dams and evaporative processes are frequently used to concentrate dilute waste waters from mining.  Nitrogen and phosphorous are stripped from municipal wastewaters prior to discharge to the environment (though residual concentrations generally remain).  Similarly, concentered brine, generally with limited commercial value or disposal options, is the product of desalination processes.

The fact that we can’t create or destroy matter means that we can’t completely eliminate pollutants by pure technological solutions.  As Bill Mitsch has observed, we need new approaches better in tune with our natural ecosystems.


Many technological solutions to pollution simply involve moving chemical substances around in an environmental shell game.

The challenge with blending Engineering and Ecology is that it requires an integrated understanding of the two disciplines.

The perception of risk may be amplified to engineers used to working with highly controlled systems, and limited understanding of biology or natural sciences.  However, ecological systems behave in predictable and quantifiable ways.  A scientifically based understanding of ecology and engineering allows integrated process systems to be designed with quantifiable performance, reliability and rigour.

Unitywater saved $18m over the service life of a treatment plant

Recognizing this problem, Unitywater on Queensland’s Sunshine coast reframed the issue of nitrogen and phosphorous in effluent as an opportunity rather than a problem.  This led to the design and construction of an irrigated rainforest and wetland as the final “process treatment” step to the newly constructed Maleny Sewage Treatment Plant.  The rainforest and wetland exploit the water and nutrients for growth, create habitat for wildlife and provide a valuable community recreation asset while comfortably meeting the final nutrient discharge specifications.  The integrated approach to water management is estimated to save $18m over its service life.


Ulan Coal, Rio Tinto and Santos incorporate ecological engineering solutions

Similarly, produced water from resource development and operations in various parts of Australia is being sustainably managed by being re-used for irrigation of fodder crops.  In each case, system design has relied on a detailed understanding of the water chemistry and its interaction with soils, combined with regional catchment and hydrogeological modelling, plant water demand modelling, solute modelling, and an understanding of plant nutrient requirements and environmental toxicity thresholds.

At Ulan Coal in NSW, a commitment to minimise untreated off-site discharge of low salinity water led to the establishment of the Bobadeen Irrigation Scheme as a component of the mine water management system.  The scheme irrigates 242 hectares of land planted with vigorously growing perennial pastures as livestock fodder to ensure there is no net increase in the salinity load in the Macquarie and Hunter Rivers catchment areas.  The scheme has been operating since 2003.

In the Pilbara, Rio Tinto has embarked on an even larger project incorporating 17 centre pivots to irrigate Rhodes grass pastures to produce hay for both Rio Tinto’s own extensive pastoral holding and sale to other local graziers, as well as native seeds for future mine site rehabilitation.  The project avoids continuous discharge to streams that are adapted to intermittent flows.  It provides a reliable supply of water, effectively drought-proofing local cattle operations and allowing year-round, local production of fodder to support grazing operations.  Additionally the project provides commercial opportunities for traditional owners through provision of contracting services, transport, local employment and training.

In southern central Queensland, Santos GLNG is also taking a leading approach to the sustainable management of co-produced water.  In certain areas of their project, coal seam water is typically fresh to brackish (100 to 4,000 uS/cm) sodic, and high in bicarbonate.  The conventional approach to managing this water involves desalination of all water, irrespective of its starting quality and end beneficial use.  While this produces a single source of higher quality water suitable for almost any beneficial use, desalination requires significant energy (with a higher greenhouse gas footprint), and results in production of a concentrated brine that requires responsible management and disposal.  Through a detailed scientific understanding of the complex interaction between water chemistry, soil, plants and landscape processes, a bespoke management approach was developed to chemically amend the water to agricultural irrigation standards in line with strict regulatory requirements, converting it from a waste to a resource with no generation of brine. This water is used for the irrigation of more than 350 hectares of legume forage feeding 1,500 cattle, and over one million locally adapted native trees sequestering carbon and producing and a future timber crop.  


In addition to the production of cattle and plantation timber, the project sequesters carbon and contributed to enhanced biodiversity. 

The project also offers opportunities for education, training and skills development and technology transfer of broader benefit to the region.

By bringing a rigorous, quantitative and integrated scientific understanding, combined with an approach that reframes the perception of by-product waters from a waste to a resource, significant opportunities exist to blend ecology with engineering to safely and sustainably manage water in a cost-effective way.

 Verterra is Australia’s leading expert in the conceptualization, design, implementation and ongoing management of water reuse projects.  For further details of Verterra’s water re-use services that deliver on the triple bottom line of economic, environmental and community benefits click here.

References

William Mitsch and Sven Jørgensen (2003).  Ecological engineering: A field whose time has come.  Ecological Engineering 20 (2003) 363–377.

Bobadeen irrigation scheme.  http://www.ulancoal.com.au/En/Biodiversity/Pages/BobadeenIrrigationScheme.aspx

New Maleny Sewage Treatment Plant Officially Opened.  http://viewnews.com.au/new-maleny-sewage-treatment-plant-officially-opened-459441/

Rio Tinto set to make hay. http://www.farmweekly.com.au/news/agriculture/agribusiness/general-news/rio-tinto-set-to-make-hay/2338321.aspx

Feasibility of salt production from inland RO desalination plant reject brine: A case study.  https://www.researchgate.net/publication/222702279_Feasibility_of_salt_production_from_inland_RO_desalination_plant_reject_brine_A_case_study