Water. Desalination + reuse
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28 Far Site March 2019 Water. desalination + reuse Aquatech prepares membrane-thermal ZLD for Columbia gold mine The new hybrd membrane-thermal system is to be installed in April and commissioning is expected to be completed by Q4 2019 lation in the Andes: the mine site in Antioquia state is 2,000 metres above sea level at its highest point and two hours by car from Medellin city. Aquatech configured a mem- brane-based treatment system to meet the site's requirements. "The wastewater produced by the mining process is high in chlorides such as sodium chlo - ride, as well as sulfates sodium, magnesium and calcium, heavy metals arsenic, cadmium and zinc, and other constituents of emerging concern," explains Aquatech senior sales manager Ashwin Thakkar. "Conventional - ly, to do this type of wastewater treatment, you need high-den- sity sludge handling clarifiers. They take up a lot of space and are not adaptable to flow rate changes. A membrane-based ap - proach is light, flexible, and in terms of performance provides consistent, high-quality filtra- tion configured in a container offering." The system (see picture) first collects the mining pro - cess wastewater into a pond. Suspended solids are removed from the water by a multi-media filter in preparation for the first reverse osmosis (RO) step. A‰er the RO, the permeate goes for reuse and the concentrate is treated for hardness before being put through a ceramic micro-filtration (MF) system. The micro-filtered concentrate then continues through two more RO stages, with permeate going for reuse. Finally, the con - centrate goes to a crystalliser and is turned into solid waste for disposal in landfill. "The design does not push the RO to its limits. Convention- ally, MF and caustic lime dosing to take care of the heavy metals are done up-front - in this case the clarifiers will be large. We reduce that capacity down to 30 per cent. The MF is doing 30 per cent of the so‰ening work compared to a conventional clarifier footprint. Overall we have reduced the capacity that goes to the crystalliser to 6.8 m3/h," says Thankkar. First of a kind The system is entirely modular. Even the crystalliser is mounted onto a "super skid", says Th- akkar. Compared to a conven- tional set-up, the membrane- based approach aims to reduce footprint, cut energy consump- tion and minimise maintenance downtime. Once installed, the system will be the first of its kind operating in mining in South America. At first, Continental Gold was planning on discharging the treated wastewater into the local water system. (It meets all the requirements of the site's dis - charge permit under Resolution 631 of Columbia's environmen- tal laws.) However, the miner is now installing additional pipes to enable the water to be reused on the site. "We explained that with this system Buritica is a unique mine facility and should probably recycle. Continental Gold now sees how that could work," adds Thakkar. Aquatech specialises in a membrane-based approach to industrial wastewater treatment. The firm has 100 membrane- based zero liquid discharge Aquatech process The Aquatech process upends conventional wisdom by using micro filtration a er the first stage of reverse osmosis. REUSE AT BURITICA • $390.3 million development project at gold mining site in Buritica, Colombia • Clarifier reduced to 30 per cent compared to conventional • Capacity to crystalliser reduced to 6.8 m3/h Continental Gold won an envi- ronmental license to develop a gold mine at the village of Buritica, northwestern Co- lombia, in 2016. The firm was granted permission to turn an existing, small-scale mine into an integrated mining and mill - ing operation. Once complete, the $390.3 million development project will have constructed a mine site with capacity to pro - cess up to 3,200 tonnes a day. The miner wanted a solu- tion for managing water supply and treatment at the site. The system would need to meet Co- lumbia's wastewater discharge regulations and overcome the logistical challenges of instal- People think of ZLD as a brute force thermal application, but hybrid systems can be more efficient. Ashwin Thakkar, Aquatech senior sales manager