A two-stage culture process using Chlorella vulgaris for urban wastewater nutrient removal and enhanced algal lipid accumulation under photoautotrophic and mixotrophic conditions

Abstract

Microalgae such as Chlorella vulgaris contain sufficient fatty acids to suggest their use as feedstocks for biodiesel production. Their capacity to remove nitrogen, phosphate, and other nutrients from a culture medium makes them a potentially useful element in urban wastewater treatment systems. A two-stage process was used to grow Chlorella vulgaris under mixotrophic and autotrophic conditions in artificial wastewater and urban wastewater media. Growth rate, nutrient removal, and lipids accumulation were quantified. Initially, the media were nitrogen-enriched (90 mg−1; Stage I), and then nitrogen limited (30, 20, and 10 mg l−1; Stage II). Growth was not inhibited under either of the culture conditions, and nitrogen uptake rates were above 90%. Total organic carbon removal was higher (56.2%–86%) under mixotrophic conditions than under photoautotrophic conditions (15.2%–69%). Lipids productivity was 2.7 times higher under mixotrophic conditions and nitrogen limitation than under photoautotrophic conditions and nitrogen limitation. Palmitic acid and linoleic acid accounted for 25.0% of total fatty acids contents, which is an adequate profile for biodiesel production. Culture of C. vulgaris in urban wastewater can improve the efficiency of nitrogen and total organic carbon removal, and water reuse, while simultaneously producing algal biomass with sufficient lipids content and an acceptable fatty acids profile for use as a biodiesel feedstock.

Productivity and Biodiesel Quality of Fatty Acids Contents from Scenedesmus obliquus in Domestic Wastewater Using Phototrophic and Mixotrophic Cultivation Systems

“…The transesterification of fatty acids was according to the methods by Sato and Murata [14]; and Canedo-Lopez et al [5]. The FAMEs profiles were generated with a Gas Chromatographer (GC) (Agilent Technology 7890).…”

“…Producing sufficient biomass with enhanced lipids contents can be done using a two-stage culture strategy [4]. In this strategy, an alga is first grown under nutrientsufficient conditions to allow maximum cell density, and then deprived of certain nutrients to trigger lipids accumulation [4,5].…”

Nutrient Removal Efficiencies of <i>Chlorella vulgaris</i> from Urban Wastewater for Reduced Eutrophication

“…The presence of various forms of nitrogen and phosphorous in wastewater leads to eutrophication [38]. C. vulgaris has a high potential to reduce nutrients in secondary waste water treatment plants effluents [39] [40] [41] while simultaneously producing algal biomass with sufficient lipids content and an acceptable fatty acids profile for use as a biodiesel feedstock [42].…”

Indoor and outdoor cultivation of Chlorella vulgaris and its application in wastewater treatment in a tropical city—Bangkok, Thailand

“…While there are many studies available on microalgae about nutrient removal from wastewater used in indoor PBRs in literature, limited studies on outdoor PBRs have been found. TN and TP removal were found maximum up to 90% and 100%, respectively, in indoor PBRs [20,29,30]. Several studies claim that algal systems integrated with different types of wastewater, i.e., brewery wastewater, swine wastewater, municipal wastewater, etc., 90-100% BOD, 60-99.9% COD, 99.96% TP, 100% total carbon and 40-90% ammonium nitrogen [31][32][33].…”