After successfuly completing your diploma you will be eligible for B.tech through lateral entry process in this process you would be get admissions directly into 2 nd year or 3rd semester of trade you have selected 

You will not have to study applied sciences and mathematics 

There are different process to get admissions in different institutes 

For regional colleges and some private colleges state entrance examination is considered To make merit 

Some deemed universities will conduct theor own entrance exams 

If not able to come in merit in entrance exam you still can enroll through management seats but for higher fees 

Related to C.E and Env engineering 

Both fields have their merits in a developing country like India Construction of Highways Dams Buliding is going on continously so civil engineering has brighter future but due to development environmental degradation is also taking place that makes env engineering a brighter prospect 

Ultimately its upto you and your interest furthermore the stream in which you have done your Diploma and gained knowledge will be best suitable 

Rest is upto you to decide.  Every field has oppurtunities its upto you to explore  them

Hello Arko!

You can get admission directly in the second year of your b.tech course by lateral entry as Diploma students are eligible for that. You will be able to complete your B.tech in 3 years in this way.

If you are interested in Construction and Planning then Civil Engineering is a good branch. Also in various public sectors there is demand for Civil Engineers.

If you are more inclined towards vegetation and Environmental studies, then only go for Environmental Engineering. CHOOSE WISELY.

Hope that helps!