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Global Synthetics’ Bentofix GCL safeguards Australian bay

News | December 20, 2017 | By:

Preparation to line the wastewater treatment pond at Broome, Australia. Photograph courtesy of Global Geosynthetics

Situated on the southern coastline of the Broome Peninsula in Western Australia, the southern wastewater facility of Water Corporation, which supplies water, wastewater and drainage services in Western Australia, has been under the spotlight in recent years following reports of contamination of the sensitive Yawuru Nagulagun/Roebuck Bay Marine Park. Outbreaks of blue-green algae in the bay have been linked to excessive nutrient levels, possibly caused by groundwater pollution in the vicinity of the wastewater treatment ponds (WWTPs) of the facility. The Water Corporation has taken steps to mitigate the risk associated with the WWTPs, including environmental studies under the direction of the Australian Department of Water and Environmental Regulation (DWER), modification of Broome’s wastewater processing and relining one of the main waste ponds.

Utilizing geosynthetic clay liners (GCLs) as a barrier system for WWTPs is nothing new to the Water Corporation, but the Broome site presented concerns in regard to preexisting groundwater chemistry. Water Corporation engineers chose a GCL capable of providing sealing capabilities in the presence of calcites (with high electrical conductivity). GCLs carrying low-grade sodium bentonite generally suffer elevated ionic exchange in such soil conditions, which in turn leads to high permeability (or poor sealing potential).

Global Synthetics’ Bentofix® GCLs carry high-grade sodium bentonite, which has been tested in chemical solutions with electric conductivities of up to 10,000 μS/s (much higher than those levels found at the Broome site) without any significant increase in permeability. It is widely recognized that GCLs with “enhanced or altered” bentonites have no track record of long-term performance in benign environments let alone those exhibited at Broome WWTP.

Installation of approx. 30,000 m2 of Bentofix® NSP 5100 was completed at Broome South by lining experts Jaylon, under a subcontract arrangement to energy services group Valmec. Third-party testing of the Bentofix® GCL was completed by BTTG. All rolls passed independent quality assurance and were approved for installation by quality auditors Bowman & Associates.

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