Dear Balagula,

In order to become a environmental engineer you have to appear for the entrance exams of engineering. You can appear in JEE (Main+advanced). For private colleges you can appear in VITEEE, SRMJEEE and COMEDK

You can check the colleges below for environmental engineering

Indian Institute of Technology Madras

Indian Institute of Technology Bombay

Indian Institute of Technology Delhi

Indian Institute of Technology Kharagpur

Indian Institute of Technology Kanpur

Delhi Technological University, Delhi

VIT University, Vellore

To check the complete list you can refer below link

https://engineering.careers360.com/colleges/list-of-engineering-colleges-in-India?f%5B0%5D=sm_college_course_level%3AUG&f%5B1%5D=sm_college_degree%3AB.E%20/Btech&f%5B2%5D=sm_course_offered%3AEnvironmental%20Engineering

Good luck!!