Exhibit 99.1

JOINT FILING AGREEMENT

We, the undersigned, hereby express our agreement that the attached Schedule 13G dated March 17, 2021 relating to the common stock, par value $0.001 per share, of Energy Recovery, Inc. is filed on behalf of each of us.

Dated: May 12, 2021

	Sundt AS

	By:	/s/ Jakob Iqbal

	Name:	Jakob Iqbal
	Title:	Chief Executive Officer

	CGS Holdings AS

	By:	/s/ Jakob Iqbal

	Name:	Jakob Iqbal
	Title:	Chief Executive Officer

	Helene Sundt AS

	By:	/s/ Jakob Iqbal

	Name:	Jakob Iqbal
	Title:	Chief Executive Officer

	/s/ Christian Gruner Sundt
	Christian Gruner Sundt

	/s/ Else Helene Sundt
	Else Helene Sundt

	/s/ Jakob Iqbal
	Jakob Iqbal