Abstract
Microalgal-based wastewater treatment and CO2 sequestration from flue gases with subsequent biomass production represent a low-cost, eco-friendly, and effective procedure of removing nutrients and other pollutants from wastewater and assists in the decrease of greenhouse gas emissions. Thus, it supports a circular economy model. This is based on the ability of microalgae to utilise inorganic nutrients, mainly nitrogen and phosphorous, as well as organic and inorganic carbon, for their growth, and simultaneously reduce these substances in the water. However, the production of microalgae biomass under outdoor cultivation is dependent on several abiotic and biotic factors, which impact its profitability and sustainability. Thus, this study’s goal was to evaluate the factors affecting the production of microalgae biomass on pilot-scale open raceway ponds under Northern Sweden’s summer conditions with the help of a mathematical model. For this purpose, a microalgae consortium and a monoculture of Chlorella vulgaris were used to inoculate outdoor open raceway ponds. In line with the literature, higher biomass concentrations and nutrient removals were observed in ponds inoculated with the microalgae consortium. Our model, based on Droop’s concept of macronutrient quotas inside the cell, corresponded well to the experimental data and, thus, can successfully be applied to predict biomass production, nitrogen uptake and storage, and dissolved oxygen production in microalgae consortia.
Highlights
The development and intensification of human activities, such as agricultural practices, urbanisation, and industrialisation, has led to excessive production of wastewater and greenhouse gases (GHG)
In pond 2, which was inoculated with a monoculture of a local strain of C. vulgaris on the 18th of May, had its microalgae population changed substantially due to contamination a few weeks later, i.e., 13th of June
The pond inoculated with the local microalgae consortium kept its dominance through the season, while the pond inoculated with C. vulgaris monoculture was rapidly overtaken by other microalgae present in the environment
Summary
The development and intensification of human activities, such as agricultural practices, urbanisation, and industrialisation, has led to excessive production of wastewater and greenhouse gases (GHG). The continuous disposal of wastewater without adequate treatment into water bodies has resulted in severe water pollution (O’Neil et al, 2012). To tackle the negative effects of wastewater on water bodies, a combination of physical, chemical and biological methods, i.e. conventional wastewater treatment (CWWT), has been employed. Since CO2 represents approximately 77% of the total GHGs, a reduction in CO2 levels would directly affect total GHG emissions (Cheah et al, 2015; Lopez et al, 2013). Several CO2 sequestration strategies have been implemented, they are not environmentally sustainable and require considerable space and investment (Cheah et al, 2015; Lage et al, 2018; Lopez et al, 2013)
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