The company said his “expertise will help to further strengthen the board” as it looks to build on its “success” in the UK-wide retail water market.
Wallace joined Forth Ports as financial controller for the Scottish operation in 2002. He has since taken on operational and commercial roles throughout Scotland, the Port of Tilbury London and London Container Terminal, the UK’s fourth largest container terminal.
He also led the team responsible for integrating London Container Terminal into the Forth Ports Group post acquisition.
Susan Rice, chair of Business Stream, who was made a Dame in the Queen’s New Year Honours list for 2018, said: “Stuart has years of experience working in an organisation that has undergone significant transformation and growth in recent years, making him the ideal candidate to join our board.
“His expertise and experience will be invaluable to Business Stream and I’m sure he’ll play a key role as we aim to retain our position as the market leader in Scotland, whilst continuing to grow our business in England.”
Wallace added: “I am very much looking forward to joining the board of Business Stream at a time when the business is going through a period of development and growth, with new markets becoming available.
“Business Stream is an exciting business with a strong board and executive team and I aim to add to this through my experience to date at Forth Ports.”
The English water retail market marked its first anniversary on 1 April, while Scotland’s non-domestic market is celebrating a decade of competition this month.