Glasgow Airport managing director Amanda McMillan and former ScottishPower executive Willie MacDiarmid are joining the non-domestic water supplier as it eyes up a move to England.
The Edinburgh business already has the biggest market share in Scotland and is hoping to capitalise when the English non-domestic water sector is opened up to competition.
Although that could be as long as four years away Business Stream is already trying to snap up contracts in the part of the market which is open and is preparing the ground for potential joint ventures and acquisitions.
Ms McMillan has run the airport since 2008 and is also a director of Glasgow Chamber of Commerce, a council member of the Institute of Chartered Accountants in Scotland and sits on the advisory board of the Glasgow University Business School.
Mr MacDiarmid spent almost 20 years with ScottishPower but left in 2009 to become chief operating officer of FTSE-250 energy services company, Eaga.
Mark Powles, chief executive of Business Stream, said: "Amanda and Willie have an enormous amount of experience at the highest levels in customer-focused businesses which operate under very tight market and regulatory scrutiny.We're very excited to have them join us and I know they'll have a lot to offer as we continue to prepare for full market opening in England, which we expect to happen over the next few years.
"We've made some excellent progress in that direction and we'll benefit further from the invaluable input of two very talented and experienced individuals who have been successful in extremely challenging markets."
Business Stream chairman Ronnie Mercer said: "Amanda and Willie will be tremendous assets in the next stage of the business's development and bring with them the right skills and experience to help us achieve the growth we're looking for in the coming years, both in our core market in Scotland and into new markets such as England."
The outgoing non-executive directors are former Edinburgh Chamber of Commerce chief executive Ron Hewitt and telecoms executive Andrew Taylor who have both served five-year terms on the board.