I promised a third post to provide examples of innovations we have been able to discover and implement at DC Water. In considering this goal, I have decided to divide this part into three sections – there’s just too much great progress to cram in one post!One part I have already published here: Innovation in Action. This first example highlighted DC Water implementing innovations in response to a time critical flooding emergency. The solution, selected after devising at least several dozen alternatives, includes: policy and finance (backwater valve program and reimbursements); government collaboration (support of green infrastructure and rain barrels at the DC Departments of Transportation and the Environment); engineering creativity (reusing abandoned sand filters to store storm water and accelerating a tunnel to be used as a giant cistern); procurement (emergency design-build); and outreach (street-by-street meetings, with tailor made community benefit packages).
In this second part, I focus on an innovation project that was devised over more than a decade of advanced planning for a challenge that is very significant for DC Water, but has a long time horizon. The third post will provide a longer list of examples of innovation from all over DC Water.
CAMBI and Green Power
This second example of innovation represents the kind of advanced planning necessary to respond to an “emergency” with a long fuse. The emergency is the challenge that a facility as large as Blue Plains has with handling the solid material we have removed from the “waste” water. Blue Plains, which can handle 370 million gallons a day at full treatment – soon to be 515 million gallons, produces on average 60 tractor-trailers filled to the brim with “biosolids.” This aromatic byproduct of removing refuse from the water is classified Class B biosolids by US EPA regulations – which means the material is not fully sterilized. Under strict regulatory controls, Class B biosolids can be applied to lands as fertilizers, as long as the product being grown is not intended for human consumption.
The long-fuse emergency is at least three-fold. First, federal regulations governing Class B biosolids could change – and overnight our beneficial reuse costs for this huge amount of material could skyrocket. Second, state or local regulations in Maryland or Virginia could change yielding a similar result. Third, the
production of Class B biosolids at Blue Plains entails lime stabilization, centrifuges and long conveyors – processes prone to failure, and certainly in need of
significant and costly rebuild.Thus, without an imminent emergency – but a clear and identified long-term risk and liability – DC Water embarked on a multi-year effort to discover a resolution. Quickly, an effort mostly to reduce risk and avoid known and recurring maintenance costs, turned into something much more. Biosolids, like the wastewater they come from, are filled with valuable components. Biosolids are infused with energy, dripping with nutrients (that is what we are mainly removing after all) and perhaps other recoverable resources. DC Water realized that it not only has 60 tractor-trailers of potential risk every day, but also 60 tractor-trailers of valuable resources. This reality is why we now call the flow that comes to Blue Plains “enriched” water rather than “waste” water. The question: how to recover that enriched value?
For DC Water, this fundamental challenge ushered in a ten-year period of research and development focused on speeding the digestion process, reducing the footprint of the digesters and enabling power generation in a vertical orientation. The team discovered a process used at a few small facilities in Europe – called CAMBI – that promised to speed the process and improve the efficiency of methane generation. In short, high pressure cookers will break down the cell walls of the biosolids that have been reformatted into a slurry. Depressurization and cooling after the CAMBI vessels causes the cells to burst. A relatively standard digestion process thereafter generates more methane from the deconstructed biosolids, and faster too. Suddenly, a solution seemed possible.
From this initial identification of a technology, the DC Water team orchestrated a series of experiments to determine whether the technology could work for a first ever use in North America and by far the largest installation in the world.
Each of these areas was the subject of scientific and technical research projects, bench studies, and even scale evaluations at facilities using CAMBI in Europe. After ten years of trial and error refinement of a digester solution, we were ready to present the CAMBI digester project to our Board of Directors.
Many ask how we were able to attain such a mammoth investment by the Board, with no federal help, for a project that is not required by law or custom, but seems the best combination of ultimate savings, risk reduction and stewardship. The answer is that the Board was confident in the scientific and technical aspects of the proposal – due to the care and discipline of 10 years of research work. Convinced that this new approach would work, the remaining question was financial. The financial aspects of the project sold it to a unanimous Board.
By the way, I forgot to mention that the digestion process yields Class A biosolids – essentially a material that is sterilized by the high heat and pressure of CAMBI. That is generating our next research and analysis of innovation on this topic that could realize new sources of revenue for DC Water. Having recovered the valuable energy in our biosolids, how can we now realize the value of the nutrients that are still bound up there? We are also evaluating approaches to harvest even more energy in these Cambi digesters by accepting for a fee commercial food and organic ‘wastes’ to produce even more energy instead of needlessly filling up landfill space.
That is the substance of a future blog!