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The Future Of Energy-Neutral Wastewater Treatment Is Here Resource recovery during wastewater treatment is becoming essential. Thanks to new technologies, it's also achievable. By Jeff Peeters H istorically, interactions between water and energy have been considered on a regional or a technology- by-technology basis. And at the national and international levels, water and energy systems have been developed, managed, and regulated independently. But more recently, the world is recognizing that water and energy are not only connected, but tightly intertwined. It's about time. We all need water and energy, and we all need to take part in the efforts to secure them for generations to come. Water reuse, policies and partnerships, and emerging disruptive technology solutions are vital to the cause. Specifically, there is an urgent need to shift how we view wastewater treatment and move to sustainable, strategic infrastructure solutions. Wastewater treatment plants are not waste disposal facilities, but rather resource recovery facilities that have the potential to produce clean water, recover nutrients (such as phosphorus and nitrogen), and reduce the dependence on fossil fuels through the production of renewable energy. According to the U.S. EPA, community drinking water and publicly owned wastewater systems in the U.S. use 75 billion kWh of energy per year — as much as the pulp and paper and petroleum industries combined or enough electricity to power 6.75 million homes. The EPA also recognizes energy as the second-highest budget item for municipal drinking water and wastewater facilities, after labor costs, with utilities spending about $4 billion annually on energy. Energy consumption by drinking water and wastewater facilities can comprise 30 to 40 percent of a municipality's total energy bill. Water and wastewater utilities are highly regulated entities whose primary goals are to meet regulatory requirements for protecting public health and the environment for reasonable and fair rates. Energy efficiency has not historically been at the top of the list of priorities. Nevertheless, as populations grow and environmental regulations become more stringent, demand for electricity at water and wastewater plants is expected to increase by approximately 20 percent, according to the EPA. Moreover, as electricity rates increase, energy conservation and efficiency are issues of increasing importance for the budgets of municipalities. The Path Toward Energy-Neutral Wastewater Treatment The lingering effects of the global economic recession have placed additional financial burden on wastewater utilities as they strive to meet increasingly strict discharge requirements with aging infrastructure in need of repair and replacement. Energy conservation, on-site generation, and renewable energy are becoming increasingly important to wastewater utilities as energy policy, energy economics, and actions to mitigate climate change converge with the need to meet higher standards of wastewater treatment. Many utilities are beginning to reduce grid-connected energy consumption at their facilities through a variety of energy conservation and on-site energy production measures. Emerging, disruptive innovations in technology combined with operational best practices are bringing into focus the opportunity to achieve energy-neutral wastewater treatment. On-site generation of energy is achieved by extracting the energy content of the organics in wastewater and converting it into a useable form. For example, advanced anaerobic digestion biosolids and biowaste processing systems use bacteria in the absence of oxygen to break down organic matter to create biogas; the biogas can then be combusted or oxidized and used for heating or with a gas engine to produce electricity and heat. It can also be compressed and used as fuel for vehicles or sold for use in a natural gas grid, while additional nutrient-rich effluent can be used as fertilizer. Designed to recycle biosolids into methane and valuable byproducts, the advanced anaerobic digestion systems are key to offering a cost-effective, low- maintenance way to turn sludge into electricity — generating renewable energy that can be used to power the very facility producing the waste. The technology can also be used to treat biowaste, such as food waste, fats/oils/greases (FOG), etc. By combining the digestion of these external sources of organic matter with the digestion of organics in biosolids from wastewater treatment, the energy production potential of a wastewater treatment facility can be significantly increased. Consider this: A city of 500,000 people produces roughly 75,000 tons of household 24 wateronline.com ■ Water Innovations