There are two sorts of jobs for an environment technologist
in the private sector, jobs in a company, or a job in a laboratory or service,
which is working for the town autorities, you could name it 'semi-public'
job sector. It could be food control or a laboratory.
The purely privately employed environment technologist often works with pollution control. Many companies develop methods to clean up old pollutions, or to investigate if an area is polluted.
He (or quite often, she) can also be leader of a laboratory, being responsible for a number of lab technicians' work. In that case he will have many years experience as lab technician before he became environment technologist.
You can also be responsible for the safety in a laboratory, or be sample taker for a pollution control company.
The 'semi-public' employment is not always so public as they sounds. The laboratory which analyzes the samples for the public autorities are organized as private companies. One of their tasks is to monitor thar the emmissions from factories and sewage works are no greater than their permits allow.