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Issue link: http://wateronline.epubxp.com/i/501621
and commercial food waste and more than 14,000 tons of sewage sludge. By treating that waste with advanced anaerobic digestion, the value of the methane byproduct used in one of GE's Jenbacher gas engines would produce about 5MWe of electricity alone — enough to power 10,000 homes. The greatest demand for energy in wastewater treatment is for providing oxygen to a biological system, which is typically achieved via forced bubble aeration. In fact, approximately 60 percent of the energy used at wastewater treatment facilities is for aeration. To achieve energy-neutral — and ultimately, net-positive — wastewater treatment, facilities require low- energy treatment alternatives to the conventional aeration, as well as methods to enhance energy generation with existing infrastructure. New, low-energy technology solutions have become a focus of research and development activity. For its part, GE has developed a flowsheet to achieve energy-neutral wastewater treatment while removing nitrogen using the proven nitrification-denitrification metabolic pathway. Compatible with solid-liquid separation by conventional secondary clarification or membrane filtration, the flowsheet is based on a hybrid membrane-aerated biofilm reactor (MABR) process, which uses hollow fiber membranes arranged in modules and cassettes deployed in a way similar to immersed hollow fiber filtration membranes used for more traditional membrane bioreactor applications. Atmospheric air is fed down the lumen of hollow fibers, and oxygen is diffused to the biofilm growing on the outer surface of the membrane without the formation of bubbles. This technology significantly increases the efficiency of oxygen transfer, resulting in a 4x-reduction in energy consumption for aeration. This flowsheet has been compared to a conventional activated sludge system, including complete wastewater and sludge treatment with anaerobic digestion, and combined heat and power energy recovery. The results thus far are promising: with electricity consumption 40 percent lower and energy production 18 percent higher (as compared to the conventional system), leading to overall energy neutrality. The Future Of Energy And Water As water and energy demand and supply continue to shift, managing the two resources in tandem will help regions worldwide maintain reliable and sustainable supplies of both. This is of critical importance as the global economy continues to explore new energy and renewable energy sources. But to sustain energy production and a dependable water supply, we must all gain even more detailed understanding of the interdependencies of water and energy systems, balance the needs of all users, and continue to develop technologies that reduce water use and enable water recycling while neutralizing or even creating energy. wateronline.com ■ Water Innovations ENERGYANDRESOURCERECOVERY 25 Jeff Peeters, PE, is a senior product manager at GE Water & Process Technologies with more than 15 years of experience developing and commercializing innovative technologies, including ZeeWeed membrane technology. About The Author Energy-efficient aeration and the recovery of nutrients are two key elements to sustainable wastewater treatment.