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More Efficient Wastewater Treatment Looms

July 15, 2016
New technologies could lead to greener, less-expensive manufacturing processes

Two advances in wastewater treatment technology promise to save significant amounts of energy and improve processing efficiency.

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The first, by scientists at Nanyang Technological University (NTU), Singapore, involves a new type of nanofilter that could reduce up to five times the energy needed to treat wastewater.

Typically in a wastewater treatment process, an ultrafiltration (UF) membrane removes small particles from the water before it goes to a reverse osmosis (RO) membrane for final purification. The high pressure needed for RO means the pumps require a lot of energy.

However, NTU’s proprietary nanofiltration hollow-fiber membrane combines both processes into one step. It also requires only two bars of water pressure, yet produces water almost as pure as the RO process.

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Researchers at NTU’s Nanyang Environment and Water Research Institute (NEWRI) have spent two years developing the new membrane; it’s now being commercialized by NTU spin-off company De.Mem, Singapore.

Single-Step Process

Figure 1. NTU’s nanofiltration hollow fiber membrane combines both ultrafiltration and reverse processes into one step. Source: NTU.

De.Mem, which owns more than a dozen water treatment plants in Vietnam and Singapore, will be building a pilot production plant in Singapore to manufacture the new membranes.

“With the increasing urbanization of cities and fast growing global population, more cities and communities will face an unprecedented challenge to meet growing demand for clean water and wastewater treatment,” notes professor Ng Wun Jern, executive director of NEWRI.

NTU professor Wang Rong, director of NEWRI’s Singapore Membrane Technology Centre, says his team designed the new membrane for commercial scale-up and production.

“Our new membrane is also easy to manufacture using low-cost chemicals that are 30 times cheaper than conventional chemicals, making it suitable for mass production,” he adds.

Andreas Kroell, chief executive officer of De.Mem, says the new membrane fills a gap in the current market for water treatment: “Such an effective and efficient technology has significant market potential and can be used in many of De.Mem’s projects that involve the treatment of industrial wastewater, too.”

De.Mem’s next step is to test the new membrane technology in a number of its treatment plants to verify its effectiveness and efficiency at an industrial scale. If this goes well, the company will then scale up its membrane production plant, too.

Meanwhile, researchers from the Universitat Autònoma de Barcelona (UAB) and technicians at water treatment company Depuración de Aguas del Mediterráneo (DAM), Valencia, Spain, will soon put into operation an experimental plant at the Rubí-Valldoreix wastewater treatment plant, with the objective of making the treatment process generate more energy than it consumes.

The technology has been developed as part of a project that focuses on the radical redesign of wastewater treatment plants to make them more efficient. Of the €1,169,068 budget, the European Union’s LIFE Programme is funding 58%. This is the EU’s only funding devoted exclusively to the environment; its general objective is to contribute to sustainable development and other important strategies related to climate and the environment.

Biogas

Figure 2. UAB researchers are attempting to develop a wastewater treatment process that generates more energy than it consumes. Source: UAB.

UAB researchers say present-day wastewater treatment plants require a minimum energy consumption of 8–15 kWh/inhabitant/year to meet legal requirements on effluent discharge in terms of organic matter, nitrogen and phosphorus. This means considerable greenhouse gas emissions and high costs. Eliminating these costs could save €500 million to 1 billion/yr in EU countries, they say.

This new treatment plant will use all organic matter in wastewater to produce biogas for heat and electricity. In addition, the nitrogen in the wastewater will be eliminated autotrophically, i.e. without the need for organic matter, by means of a new technology based on two biological stages: an aerobic partial-nitration reactor and an anaerobic ammonium oxidation (anammox) reactor.

The system has been laboratory tested; the pilot plant at Rubí-Valldoreix will treat 3m3/d of wastewater.

Compared with current urban wastewater treatment systems, UAB researchers predict the new process could consume 40% less energy, reduce nitrogen compound disposal by 10% and greenhouse gases emission by 20%, and increase biogas production 50%.

Pilot plant operation is expected to start in the first quarter of 2017, with the first experimental results due at the end of next year. Ongoing validation of the process will continue into 2018.

Seán Ottewell is Chemical Processing's Editor at Large. You can email him at [email protected].

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