to allow flow of 2 amp current in water for killing bacteria

[Externet]

how is it possible practically !!!!......using ac may be harmful!!! . what can we do instead to get 1amp of current

Yes, AC can be harmful when improperly handled. The 'brute force' method is not isolated and dangerous as told in post #7 which you should read again s l o w l y. Isolation or a transformer is convenient. The density of current in the water is to be taken in account for the size of batch/flow. "Practically" ? you have not disclosed your practical needs/method nor setup or much else in order to make recommendations.
Where from did you get your obsessive figures of 2 Amperes or 1 Ampere ?

Yes, this worked for me
120VAC ---------switch--------light bulb-------->water to be treated<-------grounded metal container.
Brute force method not for a careless ignorant infant to do it.
The current depends on the water conductivity and the light bulb 'power'. < and > are obviously the electrodes.

can I have more details

Details? OK. Enjoy an article with 24 references in the subject, read ALL s l o w l y :

----> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC154785/