If you are looking for free course materials covering the same syllabus, many institutions provide open-access PDF lecture notes: Sk Garg Environmental Engineering PDF - Scribd
: You can search for the book in your local library or university library catalogs. Many libraries provide access to textbooks and reference materials, including "Water Supply Engineering Vol 2" by S.K. Garg. water supply engineering vol 2 by sk garg pdf free download
Copyright on older editions (pre-1990s) may have expired in some jurisdictions. However, Garg regularly updates his book (now in the 25th+ edition). The 10th or 12th edition can sometimes be found in (archive.org) for borrowing. These lack modern topics like MBBR, reverse osmosis, or recent CPCB norms, but cover 80% of the syllabus. If you are looking for free course materials