JULY 2013 RESEARCH SUMMARY

JULY 2013 RESEARCH SUMMARY

Triple Bottom Line: You Can’t Stop at Just “Number Two”? I am a small cog in a much larger WERF sponsored project to use triple bottom line (TBL) analysis to optimize biosolids management options for a group of agencies that have stepped up to fund the project. As is typical these days, there is a heavy focus on energy from biosolids. As has been typical for a long time, the decision was made to focus this project starting on what happens from the time solids are removed from the clarifier. Most of the people that read this library are tasked with focusing on biosolids, or what happens with the stuff from the clarifier on down. My first task with this project was to identify and go through literature on use of TBL for wastewater treatment. Triple Bottom Line analysis is similar to life cycle assessment (LCA) in that it looks at more than a direct dollar cost of a system. LCAs have been the subject of two prior libraries (Sept 08 and Oct 09). It differs in that it includes a social aspect. This social aspect is a little tricky. As a previous WERF project pointed out, not all that many people have any idea of what happens after you flush the toilet, let alone the difference between Class A and Class B biosolids. My reading did turn up a few TBL analyses on wastewater treatment. These were often limited as a result of the wide spread public ignorance of the process. What I found more informative and impressive were the papers that included discussions of sustainability. These substituted the discussions of what biosolids mean to you with a broader discussion of the different components of wastewater and wastewater treatment and how these can be viewed with a broader lens of societal sustainability. This month’s library is an attempt to share some of that reading. It is hard to take off our blinders and realize that the biosolids are just one part of a larger process. It is my opinion though, that if you are able to do that, you not only get a broader understanding, you may potentially also get a wider range of biosolids management options, and potentially over time, a different type of biosolids product to manage. The library starts with an overview paper on energy requirements for water management in general. I found this to be a fascinating summary. Among other things, it goes into details on how much energy is used to pump water and how much water is used for washing dishes and showering in different parts of the world. When we focus on energy and biosolids, it might be informative and helpful to understand energy use at the different stages of the water cycle. The second paper is an LCA with a focus on sustainability indicators. Here, the authors have done an excellent job of dividing up the different considerations that factor into sustainability re wastewater treatment. They provide a template for different levels of sustainability and the priorities that characterize those levels. They apply this to two case studies; a site in Africa and one in Scandinavia. The primary goal of the municipality in Africa is reliable provision of clean water. In Scandinavia, the system is more developed and so the community has a wider range of options for development of a sustainable system. The third paper provides a clear case in point of options if energy recovery is really your primary focus. The authors here show what the energy balance for WWTPs would look like if anaerobic systems replaced aerobic systems. They argue that this is a viable option to both become energy positive and meet regulatory requirements. If you focus only on what happens after the clarifier, this option would not be considered. Next we move on to a paper that focuses on options for developed urban water systems. The authors note our aging infrastructure and outline possible ways to reinvent these systems. This includes development of different levels and types of treatment and a range of different products. Products are discussed more in terms of types of reclaimed water, but you can also start thinking of this from the solids perspective. The final paper in the library is one that NBMA and King County funding helped to fund. Here, Andrew Trlica (a former student) and I have broadened the perspective even further. Andrew looked at soil carbon storage in sites restored with biosolids in comparison to conventional restoration. He then used that data to model what happens to a restored hectare of land if you let it become forest or let it become houses. Here, we show how land use and residuals use, two traditionally distinct fields, are in fact, interrelated. Understanding the potential synergy is a potentially critical piece for both fields. Biosolids are what we focus on. It is very easy to lose sight of how biosolids are part of a larger process. That process can include our whole water distribution and treatment infrastructure. It can also include our municipal systems. Considering these larger processes can impact how we manage biosolids. I hope that you find this as interesting as I have. Sally Brown