Abstract
The potential of a wastewater treatment and biomass production process with the green microalgae Neochloris oleoabundans in a 45-L tubular photobioreactor was tested. In a stable and reliable alga-based process, wastewaters should undergo pre-treatment to remove colored substances. Our data show that further optimization steps may be required, such as adjustment of the N:P ratio and addition of essential metals. As a final result, parameters were established for a continuous-mode photobioreactor run with optimized wastewater for five times the hydraulic retention time (157 h) at the dry biomass concentration of 0.47 ± 0.03 g L−1. During that period, 75% and 99.6% removal efficiencies for NH4+ and PO43−, respectively, were achieved.
Highlights
In the past decade, microalga-based systems have gained interest as alternatives for wastewater treatment (Selvaratnam et al 2015)
Our research has shown that in order to establish a reliable and stable continuous process with N. oleoabundans and wastewaters, the heavy metal content and the N/P molar ratio need to be adjusted according to the requirements of the algal species
Even though the pH, according to the measurements done regularly by Helsinki Region Environmental Services Authority (HSY), is listed to be 7.4, our measurements indicated pH 8.2, indicating that anaerobic processes occurred in the transportation and storage barrels
Summary
Microalga-based systems have gained interest as alternatives for wastewater treatment (Selvaratnam et al 2015). Microalgae can be grown using wastewaters as growth media since wastewaters are rich in nutrients such as ammonium (NH4+), nitrate (NO3−), and phosphate (PO43−). Microalgae take up and utilize these compounds efficiently, incorporating them into their biomass (Shen et al 2017). Microalgae are a potential renewable source for a variety of valuable compounds with a broad range of commercial applications (Pulz and Gross 2004; Spolaore et al 2006). Implementation of microalgae for wastewater treatment might be combined with production of valuable compounds as by-products to improve the economical sustainability of the system (Kligerman and Bouwer 2015).
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