South African sustainable water and wastewater specialist Talbot has more than three decades of experience in delivering industrial water management solutions across the African continent. What is not generally realised, however, is that the company’s expertise extends beyond the ambit of water itself.

Dealing with sludges and waste streams, typically with high suspended loads, is often required to provide a total water management solution and is viewed as being both a complex and expensive process.

But this needn’t be the case.

“A leading highveld coal producer recently called on us to provide a solution for the removal of gypsum generated as a by-product of its coal mine water purification process,” says Talbot consulting services general manager Claire Lipsett.

Lipsett explains that the waste stream flowing out of the treatment process into a downstream holding dam contained a high content of gypsum, to the extent that it significantly reduced the facility’s finite storage capacity.

Pilot testing during live operations

Following an on-site examination of the processes involved, Talbot proposed a simple and well-known technology that would provide an effective solution and could be proven on site during live operations through pilot testing.

In this case, a hydraulic filter press was selected to dewater the solids, dry and press them into briquette form for transportation to end-use customers while the filtrate – minus the extracted solids – was directed to the evaporation dam before returning to site processes via a blend line.

The effectiveness of the solution was proven during a two-week trial in March and achieved impressive results. “We reduced the waste solids from around 2 900 milligrams per litre (mg/l) to just 84mg/l. We also demonstrated that the technology would extract gypsum at a rate of 100 kilograms per hour on a full-scale site operation,” she says.

The trial, Lipsett explains, showed that effective solids removal could be achieved in a single-step process, without the use of flocculants or coagulants, and offered the client an easy-to-operate, appropriate solution to achieve total water management for the site. 

Innovative trial options

Lipsett makes the point that pilot trials conducted by Talbot on a client’s behalf generate several benefits that enable them not only to fully understand the short-term implications of investing in a new technology but how they will positively impact on the future operation of a business.

“Before making any form of commitment, the client has the opportunity to engage with the technology and equipment in terms of look and feel, its effectiveness and ease of operation, all the while receiving technical and commercial guidance from a supplier that is a leader in its class and is committed to providing long-term support, not just a one-off sale.”

Economic life-cycle projections

Financial projections prepared by Talbot of conceptual models prepared during the piloting process include not only the original capital cost of the equipment but anticipated expenditure on items like membrane replacement, operational and maintenance costs.

This provides potential users with a comprehensive set of economic life-cycle projections, thus enabling them to make informed decisions on the short, medium and long-term benefits and implications with no hidden extras.

Lipsett cites the results obtained in a similar process employed by a South African platinum producer where the recovery of precious metals from a wastewater stream was achieved using the same technology and significantly exceeded initial design expectations. Pilot trials had a substantial impact on the business case and ultimately enabled the client to invest in the solution. While this may be an extreme case, there are many instances in which the materials recovered have significant intrinsic value so that solids recovery projects not only pay for themselves but deliver sustainable economic value into the future.