Sweet Harmony

Water and energy are two of our most crucial resources and their interdependence is unquestionable. Water and wastewater utilities need a substantial amount of energy to conduct processes and operations. Faced with tightening budgets and high energy costs, the U.S. water sector is slowly starting to gain a foothold in waste-to-energy practices and considering alternative energy options to reduce dependence on traditional sources. Unfortunately, there is a lack of incentive for utilities to be energy efficient or generate energy. Water & Wastes Digest Editorial Director Neda Simeonova spoke with Water Environment Federation Director, Water Science & Engineering Center, Barry Liner and Danfoss Vice President of Sales John Masters about overcoming the barriers to energy efficiency in the water sector and adopting new sustainable energy solutions. 

Neda Simeonova: As energy becomes increasingly critical for water and wastewater facilities, why is it important for more facilities to implement sustainable energy practices and become responsible energy consumers and producers?

Barry Liner: Studies have shown that treating and moving water and wastewater represent roughly 4% of U.S. electricity consumption. At the local level, water and wastewater facilities are typically the largest energy consumers, accounting for 30% to 50% of the total municipality electricity demand. With the pressures that local utilities are under to keep service rates down, it is imperative that they sustainably manage their energy usage.

John Masters: Today, water and wastewater activities—together with irrigation—jointly use more than 55 billion kWh per year. This makes water and wastewater treatment the third largest energy consuming sector in the U.S. For many municipalities, this translates to high, costly energy use in water and wastewater facilities.

For the municipality, the implementation of energy-efficient practices and technologies means reduced operating costs. While optimizing energy use, some technologies, however, also can help reduce water loss. When a facility treats, uses and delivers water more efficiently, it also improves its sustainability and customer service. 

Simeonova: WEF advocates that wastewater treatment plants should be regarded as water resource recovery facilities. Why is it important to shift perception from waste treatment and disposal to water resource recovery? 

Liner: WEF believes that wastewater treatment plants (WWTPs) are not waste disposal facilities, but rather water resource recovery facilities (WRRFs) that produce clean water, recover nutrients (such as phosphorus and nitrogen), and have the potential to reduce the nation’s dependence on fossil fuel through the production and use of renewable energy. With constrained resources in water (droughts and increasing demand), energy (rising electricity and oil costs), and nutrients (phosphorus demand for agriculture), WRRFs can truly be considered “green factories,” manufacturing needed products. By focusing on the valuable end products (nutrients, energy and water) instead of the inputs, WRRFs can be seen as “steel mills” as opposed to “iron ore processing facilities.”

Simeonova: What actionable steps can be taken to drive energy efficiency? 

Masters: In the U.S. today, there are several readily available, proven technologies to reduce energy use in water and wastewater facilities; however, because energy is comparatively cheap here, deployment rates of these technologies have been low. Furthermore, strained municipal budgets in recent years have forced a greater focus on the first-cost investment for these high-efficiency technologies. 

Overcoming these challenges and driving energy efficiency, therefore, requires structured financing models and incentive programs for municipalities, as well as regulatory acceptance and defined regulatory mandates for the implementation, use and maintenance of these new systems.  

Critical to this are the price signals, rebates and credits to retrofit existing buildings and, of course, standards, promotion and education that encourage the development of new facilities with high-efficiency equipment. 

Liner: The WEF Energy Roadmap identifies four themes for demand-side management: electricity costs and billing, power measurement and control, energy management, and source control. These themes cover specific practices such as peak shaving and performing energy audits, which can lead to optimizing aeration and pumping processes with equipment such as variable-frequency drives and using SCADA to optimize energy-intensive processes.

Simeonova: What policy barriers exist in implementing energy efficiency and generation best practices? 

Masters: Consistency in state energy service company (ESCO) legislation and financing mechanisms is needed.

Liner: Energy generated from biosolids and biogas is not consistently included in federal renewable energy portfolio standards. If it were, calls for 80% renewable energy by 2035 coupled with market forces could boost energy generation in the water sector. Standardization of eligible sources is needed. 

Anaerobic digesters often are only cost-effective if you can sell electricity back to the grid or use the gas for vehicle fuel. Often, selling electricity back to the grid is hindered by electric companies through tariffs and interconnection policies. There is a lack of incentive for anaerobic digestion partners such as dairy farmers, because it is cheaper to take their waste to a landfill. Policy could incentivize or require feedstock to go to WRRFs. 

Regulations are not streamlined and often mandate other priorities over energy efficiency and power generation from anaerobic digestion in combined heat and power systems. Sometimes regulations even present barriers to innovation. Integrated planning (water quality, energy savings, air quality, etc.) is needed. In addition, there is little guidance from the federal level down to the state. A framework that is useful for local officials, operators and others is needed. This framework should be interwoven with the permit process, and there should be a streamlined approach to approving new technology. Utilities need the flexibility to innovate while meeting permit requirements.  

Incineration of biosolids to fuel steam turbines to generate power is also used. This underutilized waste-to-energy method is hindered by the emissions standards set by the U.S. Environmental Protection Agency (EPA) in 2011 that make it significantly more expensive for WRRFs to invest in innovative biosolids incineration/energy production technologies.

Gasification and pyrolysis applications can be used to create liquid fuel. For example, Los Angeles has operated a pilot project for the past four years that uses a thermo-chemical process to convert biosolids into market-ready, drop-in No. 2 diesel fuel. KORE Infrastructure won a 2012 EPA Region 10 award for Green Chemistry for this project. The process uses pyrolysis to reduce biosolids by 90% and then utilizes the Fischer-Tropsch process to transform syngas into advanced biofuel without the use of outside energy. 

Fuel cells also can be used, both from the biogas from anaerobic digestion as a hydrogen source to microbial fuel cells. The Orange County Sanitation District (OCSD) generates electric power and steam from wastewater using central generation units and hydrogen fuel cells. The central generation units are a reciprocating and traditional technology, but the use of fuel cells at a WWTP is cutting edge. OCSD is piloting technologies to raise digester gas production using co-digestion of food waste and cell lysis technology. 

A number of emerging technologies have the potential to further enhance the renewable energy contribution from wastewater. Naturally, research remains to be conducted to develop stable and cost-effective processes, and standards must be developed to bring the technologies to industry so that they are cost-effective, predictable, controllable, and capable of achieving regulatory compliance.

Pyrolysis. This is a thermal process that uses high temperature and pressure in the absence of air to decompose organic material in the biosolids into gas, liquid and solid (or char). The process yields a product that can be pelletized into solid fuel, which can be used with coal in power plants. Currently, pyrolysis has limited application for biosolids, but the future for potential energy recovery is promising.

Gasification. This is the process that powered coal gas lights in the 1700s. It has been used for decades in Europe and Japan for converting biosolids to energy in the form of heat and electricity, and is an emerging technology in the U.S. New gasification technologies are emerging, and demonstrations of these using biosolids to generate electricity or hydrogen fuel are underway. 

Algae. Research has shown that algae can recover nutrients from wastewater and use the biogenic carbon to generate biomass with high energy content. Algae-based wastewater solutions have the potential to manage carbon, phosphorus, and nitrogen life-cycle issues and make significant net energy gains.

Anaerobic systems. These systems can be engineered to produce electrical energy by using microbial fuel cell technology to take advantage of the electrical potential in wastewater. Research shows that other microbial conversions of wastewater constituents to biofuel are possible, including butanol and methanol. 

Simeonova: What are the top methods for successful onsite energy generation? 

Liner: The most common generation method is anaerobic digestion, which is used to create biogas. Biogas can be used to generate heat, electricity, or in combined heat and power configurations. Anaerobic digestion is used at about 1,238 WRRFs in the U.S. Only about 292 facilities generate energy, while many others flare the biogas without a way to harness its potential. In the U.S., WRRFs that generate large quantities of energy generally do not use municipal waste alone. Cooperation with food or agricultural entities is often an important source of organic material; however, there are utilities in Europe and Canada that are energy neutral and use only municipal waste.

Simeonova: What existing technologies play a key role in achieving sustainable energy goals for the water sector? 

Masters: By utilizing variable-speed technology, variable-frequency drives (VFDs) directly address the interdependency of water and energy. 

Serving as an intermediary between the electrical grid and a motor, a VFD can adjust a motor’s rotational speed to precisely match the workload and reduce energy consumption. In many cases, compared to fixed speed operation, a VFD can help treatment plants save up to 20% on electrical costs annually. 

VFDs also can save up to 30% on annual water usage by controlling water pressure, which can reduce losses through holes or leaks that are often costly and unrealistic to repair. Not only is this water loss critical to the environment and a facility’s sustainability, but energy, too, is wasted during pumping and treating water that ultimately does not make it to the customer. 

In WWTPs, VFDs contribute to improved aeration control, further slashing energy costs when compared to manual aeration control. 

In addition to variable-speed technologies, process implementation such as anaerobic digestion, cogeneration and combined heat and power all are quickly becoming viable solutions for changing how the water sector consumes and produces energy. Other solutions, however, include off-grid pumping via solar or wind power, and smart grid technologies that utilize off-peak power.

Simeonova: What are key barriers in the way of investing and implementing intelligent energy technologies in the water sector?

Masters: Many of the hurdles to improving energy use in the water sector stem from either the availability of funding or financing, or the lack of federal and local policies and regulatory mandates that encourage the use of these technologies and make it easier for facilities to implement them.

Simeonova: How can private financing assist in the implementation of new energy processes and technologies?  

Liner: There is a lack of incentive for utilities to be energy efficient or to generate energy, which is critical because water and wastewater utilities are typically risk averse. While private capital is available, most municipal projects do not attract private investors due to project size and upfront cost and regulatory barriers to public-private partnerships. For example, standardization is needed for the state definitions of ESCO, and WRRFs and their energy streams should be included. 

Masters: Private financing, like ESCO financing, removes the risk associated with large capital investments. An ESCO will do a thorough audit of the wastewater treatment plant to identify savings opportunities and provide the upfront funding, so it is mutually beneficial. Municipalities also can look at leasing programs offered by some companies where, in many cases, the energy savings will offset the cost of the lease program.  

Simeonova: What should be done to engage the public and promote sustainable energy practices? 

Liner: This is a complex question and messages need to be focused on a diverse set of stakeholders. In fact, communication and outreach is one of the six core topics of the WEF Energy Roadmap. This focuses on developing communication strategy, developing the message and continuously evolving efforts. These steps should be taken for five main stakeholder classes: customers and community, regulatory and legislative, media, environmental advocacy groups and water sector professionals. 

Barry Liner, Ph.D., P.E., is director, Water Science & Engineering Center, for the Water Environment Federation. Liner can be reached at bliner@wef.org or 703.684.2435. John Masters is vice president of sales, Water, for Danfoss. Masters can be reached at jmasters@danfoss.com or 414.371.8457.

Neda Simeonova is editorial director of Water & Wastes Digest. Simeonova can be reached at nsimeonova@sgcmail.com or 847.391.1011.

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