This feels somewhat specific for this site, but since I can answer, I will. Plus, I think this is a good way to think about creating a resume anyway.
As you already know, the skill set of an electrical engineer vs a civil engineer is very different, so basically the only thing you can really sell are those skills that are less engineering-related. Think about what issues a civil engineer on a wastewater treatment project is likely to be dealing with--project siting, environmental factors, grading, etc. They will need to know land use codes, etc. so the best things for you to highlight are previous projects where, for example, you needed to take site elements into consideration as you were working on the electrical plans. In other words, try to think about the concerns you made get face as a civil engineer, and pull out elements of your previous work that touched on these same concerns.
Also, try to think through whether your knowledge of electrical engineering might impact on civil considerations; maybe you have done work on complex electrical systems and have learned things that could impact whether they should be placed underground or not--heat buildup vs limited vault spacing, etc.
Then more generally, there are issues that all engineers face, regardless of their specialty--working on a collaborative team with other design professionals, project management, budget management, etc. Whenever you can, highlight your accomplishments related to skills that are consistent across various disciplines.
As for moving to a different country, the best way to overcome that issue is to make sure to define things that people may not know. For example, if I said that I had worked on the new terminal at LAX, people in Los Angeles know that this is a big, complex project, and likely so do many people who know about airport construction around the US, would also know the relative scale of the project. But, to someone in a foreign country, the project name alone might be relatively meaningless, so you want to be sure and include quantifiers, like "provided engineering services for low-voltage system for a 300,000 sf facility" so that people can understand the scope of your prior experience more readily.
TL;DR. In order to optimize the value of unrelated experience, try to anticipate the issues you will face in this new position, and see what elements of your previous work addresses similar situations, or has provided you with insights you might bring to bear on your new role.
Hope this is helpful...