However, based on your query, here is the most likely explanation and a guide to help you locate the document. "Pedro López Alegría" is a well-known author of technical manuals on water supply and sanitation in Spanish. You are likely looking for a specific page (page 15) or item number 15 within one of his books.
Search for the full book PDF by Pedro López Alegría without the "15", then navigate to page 15 or item 15 inside that file. abastecimiento de agua potable pedro lopez alegria pdf 15
I was unable to find a specific PDF titled exactly in public or academic databases. However, based on your query, here is the