Case study on the effect continuous CO2 enrichment, via biogas scrubbing, has on biomass production and wastewater treatment in a high rate algal pond

Paul Young; Michael J Taylor; Neil Buchanan; Justin Lewis; Howard J Fallowfield

doi:10.1016/j.jenvman.2019.109614

Case study on the effect continuous CO₂ enrichment, via biogas scrubbing, has on biomass production and wastewater treatment in a high rate algal pond

J Environ Manage. 2019 Dec 1:251:109614. doi: 10.1016/j.jenvman.2019.109614. Epub 2019 Sep 26.

Authors

Paul Young¹, Michael J Taylor², Neil Buchanan³, Justin Lewis⁴, Howard J Fallowfield⁵

Affiliations

¹ Health and Environment Group, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia. Electronic address: paul.young@flinders.edu.au.
² Health and Environment Group, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia. Electronic address: michael.taylor@flinders.edu.au.
³ Health and Environment Group, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia.
⁴ Melbourne Water Corporation, 990 La Trobe Street, Docklands, Victoria, 3008, Australia. Electronic address: justin.lewis@melbournewater.com.au.
⁵ Health and Environment Group, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia. Electronic address: howard.fallowfield@flinders.edu.au.

PMID: 31563600
DOI: 10.1016/j.jenvman.2019.109614

Abstract

Microalgae grown in high rate algal ponds (HRAP) treating wastewater are considered a promising feed for biofuel production. Biomass productivity is often considered to be limited by carbon availability, with the addition of CO₂ being the proposed solution. Biogas from anaerobic wastewater treatment potentially provides a cheap, co-located CO₂ source. Two identical 223 m² HRAPs were constructed at Melbourne Water's Western Treatment Plant, where biogas from an anaerobic lagoon is used to generate electricity. One HRAP was fed secondary treated wastewater that had been enriched with CO₂ recovered from the biogas using industry standard biogas scrubbers, the Enriched HRAP, while the other HRAP was fed the same wastewater expect it had by passed the biogas scrubbers, the Control HRAP. The biomass production and wastewater treatment performance of the two HRAPs was compared over 12 months. The inlet to the Enriched HRAP had significantly higher free CO₂ and inorganic carbon, 175.00 ± 49.30 mg L^-1 and 110.00 ± 10.2 mg L^-1, than the inlet to the Control HRAP, 9.30 ± 7.08 mg L^-1 and 89.62 ± 5.12 mg L^-1. There were no significant differences in biomass production between the HRAPs as measured by dry matter, particulate organic carbon or nitrogen. Chlorophyll a was statistically higher in the Enriched HRAP, however, this measurement is potentially unreliable. Regarding wastewater treatment, only total nitrogen and ammonium removal differed significantly between the HRAPs, with the Control HRAP, 59.13 ± 21.13% and 76.46 ± 32.33%, slightly outperforming the Enriched HRAP, 53.52 ± 17.41% and 68.76 ± 31.17%. Overall, neither biomass production nor wastewater treatment was meaningfully improved by CO₂ enrichment, however, wastewater treatment was still effective in both HRAPs.

Keywords: Biogas scrubbing; CO(2) addition; High rate algal ponds; Microalgal biomass; Wastewater treatment.

MeSH terms

Biofuels
Biomass
Carbon Dioxide
Chlorophyll A
Microalgae*
Ponds
Waste Disposal, Fluid
Wastewater*

Substances

Biofuels
Waste Water
Carbon Dioxide
Chlorophyll A