21st Century Sustainability Metrics: Wastewater Life Cycle Analysis
- Leah Teuber, Katya Bilyk, P.E., Joe Rohrbacher, P.E., Joyeeta Banerjee, P.E.
- Brian Henn, P.E., Sandeep Mehrotra, P.E., and Norman Bradley, P.E. - Hazen and Sawyer
Life Cycle Assessment (LCA), often referred to as “cradle-to-grave” analysis, evaluates the environmental impact of a given product or process throughout its lifespan. As it relates to water and wastewater treatment, LCA can provide a comprehensive picture of environmental impacts such as energy use, carbon footprint, and greenhouse gas emissions for a variety of alternatives. PRé Consultants of the Netherlands have developed impact modeling software, SimaPro 7.0, to perform LCAs. SimaPro is a robust product that leads the LCA market.
This presentation will explain how environmental impacts can be quantified using the following research questions as examples:
(1) What is the environmental impact of each unit process at a wastewater treatment plant?
(2) Among methanol, ethanol, corn syrup, and glycerin, which is the most sustainable?
(3) How do the environmental impacts associated with treating to the limits of conventional technology (TN=3 mg/L, TP=0.3 mg/L) compare to the impacts of complying with ultra-low nutrient standards (i.e., TN=1.5 mg/L, TP=0.006 mg/L)?
As a result of this exercise, defendable and quantifiable recommendations about energy savings and sustainability can be provided to municipalities.
In SimaPro, impact categories are used to quantify and compare the various ways in which a process can affect human health, ecosystem quality, or natural resources. These impact categories range from carcinogens and respiratory effects to climate change and land use impacts. The following are examples of some conclusions that were drawn from the LCA:
1) Among unit processes at one wastewater treatment plant, the most notable environmental impacts are caused by the activated sludge process, the anaerobic digester, and nutrient impacts to receiving waters.
2) Among methanol, ethanol, corn syrup, and glycerin, the overall environmental impacts were within an order of magnitude and are considered equivalent within the accuracy of the evaluation.
3) Although ultra-low nutrient standards may have a positive effect on receiving surface waters, the large amounts of power required by the advanced technologies can have a far greater negative impact on overall ecosystem quality, human health, climate change, and natural resources.
Summary and Conclusions
Results of each LCA analysis provide useful information in which every unit process in SimaPro represents an opportunity to reduce environmental damage. This presentation will show how LCA can be used as a powerful decision making tool for municipalities to aid in optimizing replacement of aging infrastructure, identifying better alternatives to existing technology, and master planning-level decisions.
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