New Paradigms for Energy

A WERF research project looks beyond energy efficiency, aiming to begin identifying pathways to energy self-sufficiency for clean-water plants.

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Energy is a big item on clean-water plant agendas: More and more plant teams are striving to make their facilities energy neutral or even net energy producers.

Now the Water Environment Research Foundation (WERF) has launched an 18-month research project to explore energy balance, reduction, recovery and production in treatment plants, with the vision of helping facilities achieve net zero energy.

The project goes by the long-winded name of "Energy Balance and Reduction Opportunities: Case Studies of Energy-Neutral Wastewater Facilities and Triple Bottom Line Research Planning Support." Its aim is to help transfer knowledge and experience among utilities and provide guidance for achieving energy self-sufficiency.

WERF contracted for the project with Black & Veatch, in partnership with AECOM, the North East Biosolids and Residuals Association, Hemenway Inc. and American Water. Co-sponsored by the New York State Energy Research and Development Authority, the study will involve 23 utility partners from the United States and Australia.

The research team, under co-principal investigators Lori Stone, biosolids global practice and technology leader for Black & Veatch, and Paul Kohl, energy program manager at the Philadelphia Water Department, will identify ways for utilities to reduce demand, increase energy efficiency, recover energy, and produce energy on site.

Stone and Lauren Fillmore, WERF senior program director, talked about the project in an interview with Treatment Plant Operator.

: Why is WERF undertaking this research project?

Fillmore: Starting about five years ago, we began looking at the issue of optimizing wastewater systems, and energy efficiency was one way to do that. At the time we had some very modest goals: We wanted to achieve a 20 percent reduction in costs or improvement in energy demand.

After five years of research, we really started to embrace the idea that there is a lot of energy in wastewater in a number of forms. The goal we've set now is to look at what research needs to be done to help our subscribers, mostly from the wastewater sector, to become energy producers or at least meet the net zero energy goal. This is a goal that the industry is starting to embrace.

What actual forms of energy do we find in wastewater?

Fillmore: First of all, wastewater comes into the treatment plant at a warmer temperature than the ambient water would, because of the heat that goes into the water from activities like washing and showering. That heat can be extracted by various technologies. This is not lab-scale or pilot-scale research — it has been implemented.

Second, there is the energy of flowing or falling water. San Diego has been using this for years because their discharge is on a bluff. They have a drop of 90 feet, and they use turbines to capture that energy. There is also newer hydro power equipment that will take energy from low-head applications, or just flowing water.

The biggest energy component is chemical. A variety of microbial and biochemical processes have potential to produce energy or heat from wastewater, and a lot of work is being done toward improving production of biogas and other combustibles.

Another phase of work is developing processes that can operate with less energy input. The activated sludge process demands significant energy, primarily for oxygen transfer. As we look at innovative microbial processes and new ways to manage carbon and nitrogen in wastewater, we may find significant opportunities for efficiency.

How does this effort differ from historic energy initiatives?

Stone: Much of the focus in the past has been on energy efficiency — how to conserve energy based on the way the plant was operating. Now we need to start looking at demand reduction and then at the other side of the equation, which is how to produce power from biosolids or biogas to reach the energy neutral goal. You start with energy efficiency and add energy production to get to energy neutrality.

We've tried to enlist some utilities that already have lessons learned and have demonstrated progress toward becoming energy neutral. East Bay Municipal Utility District in California is one; the Gloversville-Johnstown Joint Wastewater Treatment Facility in New York is another.

: What do you see as the key outcomes of this research?

Stone: This research program includes three basic tasks. The first is to look at some common configurations of wastewater treatment plants on the liquid and solids sides, try to model their processes, and demonstrate what energy neutrality could look like in those settings.

The second is to identify case studies that show the challenges and the successes utilities have had. Many utilities today are truly progressive — in particular they have seized opportunities for co-digestion and biogas production. We want to be able to document what they've done and how they did it.

Third is to develop a decision-making tool — a triple-bottom-line model focused on energy from a programmatic perspective, versus a project-by-project approach.

Fillmore: Because this is part of a research program that encompasses several years, we hope to use that triple-bottom-line analysis to inform where we could make the most environmentally sustainable investment of research dollars in the future. The elements we've pre-selected include improving biogas production, developing low-energy alternatives to the activated sludge process, and finding integrated ways to recover energy from either the solid or the liquid side of a facility.

: Based on what we know today, is it easier for larger plants than for smaller plants to achieve energy neutrality?

Fillmore: We feel that in the next 10 or 20 years, the greatest potential lies in plants with flows of 5 mgd and larger. Admittedly, that is a somewhat arbitrary cutoff.

Stone: Because of the cost of biosolids processes, from having enough solids to produce a significant volume of biogas, to cleaning up the biogas for combustion, the ability to make those investments would be severely limited at smaller facilities. We've seen some facilities around the 5 mgd mark having successes, particularly in the area of co-digestion and biogas utilization.

In your experience, is the up-front investment required to make major energy improvements a substantial barrier to completing projects?

Fillmore: Our previous work has shown that one of the major barriers is financial. We found that different utilities would make very different decisions even with the exact same set of concrete financial numbers. One reason is that there are different kinds of financial analysis.

For energy efficiency projects, the one that's commonly used — but is probably not the best one — is simple payback. And even within simple payback we found wide diversity in what agencies would use as a threshold to go forward. Some would say projects had to pay back in two years; others didn't care how long the payback took as long as it was within the term of the bonds that would finance the project.

We found that if they looked at the more sophisticated forms of economic analysis, such as net present value and internal rate of return, they would be more inclined to go forward with projects. It is important to move these projects forward because the cash savings can be significant.

Stone: Utilities have many competing demands: dealing with the public, meeting regulations, being good stewards of funds, protecting the environment. Energy projects are often viewed as discretionary items as opposed to being part of the core mission. The tendency is to look at simple payback, which lacks the perspective of the full life-cycle benefit of the project. By using other approaches to evaluate energy projects, you can come up with a strong justification for proceeding.

As a practical matter, how do you see clean-water agencies benefiting directly from the products of this 18-month research program?

Stone: Besides synthesizing the core information and putting it into a final report, we'll provide some outreach and information pieces about energy balance and the models that work in representative wastewater treatment plant configurations. We envision being able to use social media for more dynamic delivery of the information in the case studies.

We would profile the various utilities not only in the report, but also in a video we could post on the WERF Web page or on Facebook. We could even tweet links to short videos that highlight the utilities and their progress toward energy neutrality.

Fillmore: WERF's sister organization, the Water Environment Federation, provides manuals of practice and other guidance to professionals in the industry. They're looking to develop a process utilities would go through in trying to reach a net zero energy goal. The information and the case studies that come out of this research will complement what WEF is doing. Often, people need to see something concrete in terms of what other utilities are doing. Just seeing something that's a little more than conceptual really helps people move to the next level.


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