Applied Biochemistry and Biotechnology April 2012, Volume 166, Issue 7, pp 1661-1673

Applied Biochemistry and Biotechnology

April 2012, Volume 166, Issue 7, pp 1661-1673

Influence of Exogenous CO2 on Biomass and Lipid Accumulation of Microalgae Auxenochlorella protothecoides Cultivated in Concentrated Municipal Wastewater

Bing Hu, Min Min, Wenguang Zhou, Yecong Li, Michael Mohr, Yanling Cheng, Hanwu Lei, Yuhuan Liu, Xiangyang Lin, Paul Chen, Roger Ruan

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Abstract

The effects of exogenous CO2 on the growth and lipid accumulation of a local screened facultative heterotrophic microalgae strain Auxenochlorella protothecoides (UMN280) as well as nutrient removal from concentrated municipal wastewater stream (centrate) were examined in this study. A 12-day batch experiment was conducted with CO2 aeration at three levels, namely, 0%, 1%, and 5% (v/v) CO2 mixed with air, under light intensity of 60 μmol/(m2 @@s). A two-stage growth pattern was observed. The first stage (first–fifth day) was dominated by heterotrophic growth in which organic carbon was the main carbon source. The second stage (6th–12th day) was dominated by autotrophic growth in which exogenous CO2 had a positive effect on algal biomass accumulation. The addition of 5% CO2 was better than that of 1% CO2 on the biomass and lipid production. The uptakes of nutrients were similar between injection and no injection of CO2, except on phosphorus removal which was affected by the acidification of CO2.

Applied Biochemistry and Biotechnology

September 2011, Volume 165, Issue 1, pp 123-137

Cultivating Chlorella sp. in a Pilot-Scale Photobioreactor Using Centrate Wastewater for Microalgae Biomass Production and Wastewater Nutrient Removal

Min Min, Liang Wang, Yecong Li, Michael J. Mohr, Bing Hu, Wenguang Zhou, Paul Chen, Roger Ruan

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Abstract

This study is concerned with a novel mass microalgae production system which, for the first time, uses “centrate”, a concentrated wastewater stream, to produce microalgal biomass for energy production. Centrate contains a high level of nutrients that support algal growth. The objective of this study was to investigate the growth characteristics of a locally isolated microalgae strain Chlorella sp. in centrate and its ability to remove nutrients from centrate. A pilot-scale photobioreactor (PBR) was constructed at a local wastewater treatment plant. The system was tested under different harvesting rates and exogenous CO2 levels with the local strain of Chlorella sp. Under low light conditions (25 μmol·m-2s-1) the system can produce 34.6 and 17.7 g·m-2day-1 biomass in terms of total suspended solids and volatile suspended solids, respectively. At a one fourth harvesting rate, reduction of chemical oxygen demand, total Kjeldahl nitrogen, and soluble total phosphorus were 70%, 61%, and 61%, respectively. The addition of CO2 to the system did not exhibit a positive effect on biomass productivity or nutrient removal in centrate which is an organic carbon rich medium. The unique PBR system is highly scalable and provides a great opportunity for biomass production coupled with wastewater treatment.