Microalgal process for treatment of high conductivity concentrates from inland desalination

Abstract

Desalination concentrate contains high levels of dissolved ions such as alkalinity, sulfate, and synthetic chemicals. Microalgal species that have ability to grow in the presence of these ions can be used to treat concentrates. A natural indigenous microalgal consortium originally grown in the concentrate of an evaporation pond was selected, cultured, and seeded in the growth medium for treatment of concentrates. Fed-batch experiments were performed with five different conductivities of concentrates in five reactors, with duplicates. Supernatants or leachates from anaerobic digested sludges were supplied as nutrients. Energy was supplied by sunlight during regularly scheduled office hours. Artificial light was supplied as energy during the weekend and all holiday hours. Environmental air was supplied as carbon during the office hours, weekend, and holidays. Water quality from treated concentrate in reactor R1 at 20 d of treatment was sufficiently pure to be given to sheep. Overall mass conductivity reductions from concentrate and supernatant or leachate were 54.7, 53.4, 45.8, 37.3, and 40.4% at 110 d for reactors R1–R5, respectively. These reductions depend on the initial conductivity of concentrate. Mass reduction percentage is inversely proportional to initial mass conductivity, with a variation of the coefficients “a” and “b” as a second-order of polynomial function of the treatment time.

Keywords:

• Natural microalgal consortium
• Alkalinity
• Anaerobic digested sludge
• Brackish Groundwater National Research Facility microalgal species
• Dissolved conductivity reduction

Acknowledgment

This project was supported in part by the United States Office of Naval Research (ONR) (Contract # N00014-08-1-0304), Tier I: Reclamation Cooperative Agreement Program through Bureau of Reclamation GR0002841-GHASSEMI BOR COOP, NSF Engineering Research Centre: RenuWIT, and Ed & Harold Foreman Endowed Chair. We also thank anonymous editors and reviewers for their constructive professional advice. PI for Contract # N00014-08-1-0304 and GR0002841-GHASSEMI BOR COOP is Prof. Dr. Ghassemi. PI for NSF Engineering Research Centre: RenuWIT is Prof. Dr. Nirmalakhandan Khandan, Ed & Harold Foreman Endowed Chair.