SouthWest Water Co. will separate the role of chairman and chief executive, and adopt other corporate governance changes at a shareholders meeting next month, the company announced Wednesday.

Last month the Los Angeles-based water services company restated several quarters due to accounting errors,

Shareholders will meet Sept. 11 to approve the new corporate governance guidelines, which lower the mandatory retirement age of directors to 72 from 75 and split the roles of the two top executives. A new chairman will be named at the meeting.

The company, which owns utilities and provides water and related services to municipalities and companies, restated financial statements in July for its 2006 and 2007 fiscal years and quarters ended March 31, 2008 and June 30, 2008, with a cumulative reduction in net income of $10.2 million.

The accounting problems were uncovered by the company’s new auditors, PricewaterhouseCoopers LLP, which took over after a new management team led by Chief Executive Mark Swatek came on board in mid-2007.

“The board’s actions, including separating the chairman and chief executive officer roles, will strengthen the governance of SouthWest Water,” Swatek said in a statement, “Moreover, the transitional period leading to the 2010 annual meeting will ensure that the institutional knowledge of the retiring directors will be passed on to the new members.”

The company also added two directors with extensive corporate governance experience to the board, bringing the total to 10, although four directors are set to leave the board in May. Bruce C. Edwards and Kimberly Alexy joined the board on Monday.

Edwards, 55, teaches a graduate corporate governance and control course at Chapman University and is a director at Emulex Corp. and Semtech Corp. Alexy, 39 is a chartered financial advisor, the principal of Alexy Capital Management, and a director at CalAmp and Dot Hill Systems.

SouthWest Water shares were up 12 cents, or 3 percent, to $4.50 in midday trading on the Nasdaq.