The former Mwatate MP garnered 49,901 votes against the incumbent's 23,703.
Stanley Muiruri Muthama and Ruweida Mohamed Obo have clinched the Lamu West and Lamu East seats respectively.
Achani beat ODM's Hamadi Boga who came second with 53,972 votes.
MP promises to help better lives of constituents through more projects.
Mr Mungatana, who vied on a United Democratic Alliance Party ticket, was declared the Tana River Senator-elect on Friday.
Dado accuses IEBC officials of rigging elections in favour of Dhadho.
Mungatana won Tana River senate seat with 34,129 votes.
He replaces Mr Abdulswamad Nassir who is vying for governor seat in elections set for August 23,2022.
Chome won with 9,418 votes.
Jomvu MP Badi Twalib garnered 13, 850 votes against his closest rival Renson Thoya who got 9,407 votes.
Mr Mohamed Ali garners 32,988 votes to beat Said Abdalla of ODM who had 18,642 votes
Suspects had ben found with a Kiems kit, IEBC stamps and empty ballot papers.
The battle is expected to become tighter, even as vote tallying continues.
Mr Bwire garnered 18,742 votes, defeating Ms Shaban, who was Taveta MP for 20 years.
Two people in Matuga were reportedly found in possession of form 34As, seals and other poll material.