Now, as we have a long list and various scales of water treatment technologies, sustainability goals require their careful assessment in terms of environmental, economic, and social effectiveness. LCA analysis is a very common tool to select specific technologies for a particular sustainability system. Note that specific location, hydrological profile, and available infrastructure are pivoting factors in such assessment. LCA cannot be general - it has to be case specific. Therefore, it would be best for us to consider a specific example that would describe LCA for a particular prospective water treatment technology.
The LCA study referred below is on a novel membrane-based technology for drinking water treatment. It compares conventional existing practice with a new method using comprehensive lifecycle inventory for both and applying LCA software for data interpretation. This article is a good example to follow when designing an LCA project:
This article is available online through PSU library system - copy / paste the title into LionSearch to find it.
This article contains significant amount of technical details and chemistry data, which some of you may find hard to digest. You do not have to understand it all - your goal will be to follow through the methodology and understand the main steps that lead to authoritative conclusions. While reading, pay attention to the following aspects:
- The goal for this LCA study
- Motivation to consider the new water treatment method. Was there a problem with the existing practice?
- What is "functional unit" and how it is chosen?
- Criteria (metrics) chosen for assessment
- Software was used for the analysis
- Results and conclusions: Can you read and explain the diagrams?
As you can see from this real-life LCA project, proper assessment requires a great deal of technical details and significant amount of data. For instance, the authors had to perform autopsy of system components to enlist all included chemical components that have a potential environmental impact at the stage of system manufacturing. Also, operational stage data are have to be closely tied to the specific demographic and geographic setting and the scale of application.
An additional thought on LCA: this type of analysis is always used to compare things - different products, systems, technologies, or methods. It has much less value if performed for just a single product or a single technology. The output of LCA is quantified environmental impact. And one needs a baseline, a reference point, to tell if that impact is big or small. Zero impact is probably not a good reference because no such ideal technology virtually exist. LCA also allows identifying relative magnitude of various impacts. For example, we can determine if there is more contribution to greenhouse gas emissions or to potential soil contamination, etc. In turn, this would help direct the mitigation measures (actions to reduce impact by redesigning the system, improving the process, or searching an alternative) towards the highest impact found.
Here is another example of comparative LCA (in the form of slide presentation), which is related to three wastewater treatment strategies. This reading is optional, but also provides you with a good illustration of the approach.
Lyons, E et al., Life Cycle Assessment of Three Water Scenarios: Importation, Reclamation, and Desalination (Arizona State University)
Check Your Understanding
What are the main four stages of technology lifecycle that are typically considered in LCA?
Click for answer.
1. Extraction of raw materials; 2. Manufacturing; 3. Operation / maintenance; 4. Waste management / disposal
What are the main four recommended steps in LCA project?
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1. Defining goal and scope; 2. Life cycle inventory; 3. Impact assessment; 4. Interpretation of results
In the end of this lesson, one of your assignments will be to work on the technical review for individual course project. The above sources can be helpful in orienting you in the part related to lifecycle inventory for the technology of your choice. Refer to the Summary and Activities page for more details.