ERII

The shares became fully vested and exercisable on June 23, 2017 and expire on June 23, 2026.

This amount represents the weighted average sales price of multiple trades ranging from $8.60 to $8.86 per share. The reporting person undertakes to provide the SEC Staff, Energy Recovery, Inc. or a shareholder of Energy Recovery, Inc. full information about the number of shares sold at each separate price upon request.

This amount represents the weighted average purchase price of multiple trades ranging from $8.535 to $8.93 per share. The reporting person undertakes to provide the SEC Staff, Energy Recovery, Inc. or a shareholder of Energy Recovery, Inc. full information about the number of shares purchased at each separate price upon request.

The restricted stock unit will fully vest on the 2027 Annual Meeting, anticipated to be on or around June 3, 2027.

The restricted stock unit will fully vest on the 2027 Annual Meeting, anticipated to be on or around June 3, 2027.

The restricted stock unit will fully vest on the 2027 Annual Meeting, anticipated to be on or around June 3, 2027.

The restricted stock unit will fully vest on the 2027 Annual Meeting, anticipated to be on or around June 3, 2027.

This amount represents the weighted average purchase price of multiple trades ranging from $8.335 to $8.35 per share. The reporting person undertakes to provide the SEC Staff, Energy Recovery, Inc. or a shareholder of Energy Recovery, Inc. full information about the number of shares purchased at each separate price upon request.

This total reflects the 20,000 shares purchased on May 13, 2026, as well as 17,362 shares the Reporting Person transferred in January 2026 to the Bruce-Tondreau Living Trust Dtd October 11, 2018, of which the Reporting Person and their spouse are beneficiaries. The Reporting Person may be deemed to have beneficial ownership of the shares held by the Trust.

The sales reported in this Form 4 were made by a broker, without instruction by the reporting person, to satisfy a margin call by the broker, to whom these shares were pledged as collateral for a margin account.

The sales reported in this Form 4 were made by a broker, without instruction by the reporting person, to satisfy a margin call by the broker, to whom these shares were pledged as collateral for a margin account.

This amount represents the weighted average sales price of multiple trades ranging from $10.83 to $11.11 per share. The reporting person undertakes to provide the SEC Staff, Energy Recovery, Inc. or a shareholder of Energy Recovery, Inc. full information about the number of shares sold at each separate price upon request.

This amount represents the weighted average sales price of multiple trades ranging from $10.71 to $10.7109 per share. The reporting person undertakes to provide the SEC Staff, Energy Recovery, Inc. or a shareholder of Energy Recovery, Inc. full information about the number of shares sold at each separate price upon request.

These transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person.

This amount represents the weighted average sales price of multiple trades ranging from $10.23 to $10.80 per share. The reporting person undertakes to provide the SEC Staff, Energy Recovery, Inc. or a shareholder of Energy Recovery, Inc. full information about the number of shares sold at each separate price upon request.

Payment of tax obligation by withholding securities incident to the vesting of securities in accordance with Rule 16b-3(e).

These employee restricted stock units were granted on the transaction date. 25% of the restricted stock units will vest on the first four anniversaries of the grant date.

Each restricted stock unit represents the right to receive, at settlement, one (1) share of the Company's common stock.

These employee restricted stock units were granted on the transaction date. 25% of the restricted stock units will vest on the first four anniversaries of the grant date.

Each restricted stock unit represents the right to receive, at settlement, one (1) share of the Company's common stock.

These employee restricted stock units were granted on the transaction date. 25% of the restricted stock units will vest on the first four anniversaries of the grant date.

Each restricted stock unit represents the right to receive, at settlement, one (1) share of the Company's common stock.

These employee restricted stock units were granted on the transaction date. 25% of the restricted stock units will vest on the first four anniversaries of the grant date.

Each restricted stock unit represents the right to receive, at settlement, one (1) share of the Company's common stock.

These employee restricted stock units were granted on the transaction date. 25% of the restricted stock units will vest on the first four anniversaries of the grant date.

Each restricted stock unit represents the right to receive, at settlement, one (1) share of the Company's common stock.

These employee restricted stock units were granted on the transaction date. 25% of the restricted stock units will vest on the first four anniversaries of the grant date.

Each restricted stock unit represents the right to receive, at settlement, one (1) share of the Company's common stock.

These transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person.

These transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person.

These transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person.

These transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person.

Payment of tax obligation by withholding securities incident to the vesting of securities in accordance with Rule 16b-3(e).

Payment of tax obligation by withholding securities incident to the vesting of securities in accordance with Rule 16b-3(e).

Payment of tax obligation by withholding securities incident to the vesting of securities in accordance with Rule 16b-3(e).

Payment of tax obligation by withholding securities incident to the vesting of securities in accordance with Rule 16b-3(e).

Payment of tax obligation by withholding securities incident to the vesting of securities in accordance with Rule 16b-3(e).

Payment of tax obligation by withholding securities incident to the vesting of securities in accordance with Rule 16b-3(e).

Payment of tax obligation by withholding securities incident to the vesting of securities in accordance with Rule 16b-3(e).

These transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person.

This amount represents the weighted average sales price of multiple trades ranging from $14.64 to $14.753 per share. The reporting person undertakes to provide the SEC Staff, Energy Recovery, Inc. or a shareholder of Energy Recovery, Inc. full information about the number of shares sold at each separate price upon request.

This amount represents the weighted average sales price of multiple trades ranging from $14.96 to $14.972 per share. The reporting person undertakes to provide the SEC Staff, Energy Recovery, Inc. or a shareholder of Energy Recovery, Inc. full information about the number of shares sold at each separate price upon request.

These transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person.

This employee stock option was granted on February 1, 2018. 25% of the shares fully vest on the 1st anniversary of the vesting start date; thereafter, the remaining 75%, vest 1/36th per month.

25% of these options fully vest on the 1st anniversary of the vesting start date of 02/02/2017; thereafter, the remaining 75% vest 1/36th per month.

These transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person.

These transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person.

This employee stock option was granted on February 1, 2018. 25% of the shares fully vest on the 1st anniversary of the vesting start date; thereafter, the remaining 75%, vest 1/36th per month.

These transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person.

This employee stock option was granted on February 1, 2018. 25% of the shares fully vest on the 1st anniversary of the vesting start date; thereafter, the remaining 75%, vest 1/36th per month.