ESPA Series High Productivity Energy-Saving Polyamide Membranes The ESPA Product line includes: ESPA1 - The world's leading high productivity, energy-saving polyamide membrane ESPA2 - Combines high productivity, energy savings and less salt passage all in one element ESPA3 - One of the industry's leading brackish water RO elements ESPA4 - Highest productivity & rejection with next-generation performance