A substantial insider activity was disclosed on August 21, as Buehler, Board Member at Energy Recovery (NASDAQ:ERII), reported the exercise of a large sell of company stock options. What Happened: A notable Form 4 filing on Wednesday with the U.S. Securities and Exchange Commission revealed that Buehler, Board Member at Energy Recovery, exercised stock options for 19,841 shares of ERII, resulting in a transaction value of $302,773. Energy Recovery shares are trading down 0.0% at $18.18 at the time of this writing on Thursday morning. Since the current price is $18.18, this makes Buehler’s 19,8…