Environmental Engineering

Hello Dipak,
As per my knowledge, I think you want to apply for Mtech in Environmental Engineering after doing your Btech in Civil Engineering. You need to appear for the GATE examination for that. But our University does not provide such courses. You can check from this site the list of technical courses provided by our University: https://nehu.ac.in/school/5/School-of-Technology
But if you want to apply for MSc in Environmental science, it is under the school of Human and Environmental science. The Candidates with a Bachelor's degree (Majors) in Environmental Science /Botany /Zoology /Chemistry / Biotechnology /Biochemistry /Geography /Geology/Forestry are eligible to apply. You need to apply for the NEHU Entrance examination. Last year the last date to apply for MSc in environmental science was 16th July 2019 but this year it hasn't started yet. You can frequent;y check their website for further admission related details: https://nehu.ac.in/Admission-Announcements
But I am not sure whether you are eligible or not for this course, you can search for further information from google but surely you can apply for Mtech in Environmental engineering but in other colleges, because it is not provided here.
Just a suggestion I think you should apply since it depends on the university because an engineering degree is a bit enough for this course.
Hopefully, my answer help you a little bit
Regard