ORGANIC CARBON SUPPLEMENTATION OF STERILIZED MUNICIPAL WASTEWATER IS ESSENTIAL FOR HETEROTROPHIC GROWTH AND REMOVING AMMONIUM BY THE MICROALGA CHLORELLA VULGARIS¹

Abstract

Heterotrophic growth of the microalga Chlorella vulgaris Beij. in synthetic as well as sterilized municipal wastewater of a nonindustrialized city was measured. The city wastewater contained high levels of ammonium and nitrate, medium levels of phosphate, and low levels of nitrite and organic molecules and could not support heterotrophic growth of C. vulgaris. Evaluation of 11 known carbon sources for this microalga that were added to standard synthetic wastewater containing the same levels of nitrogen and phosphorus as the municipal wastewater revealed that the best carbon sources for heterotrophic growth were Na-acetate and d-glucose. These provided the highest growth rates and the largest removal of ammonium. Growth increased with concentration of the supplement to an optimum at 0.12 M Na-acetate. This carbon source was consumed completely within 10 d of incubation. Higher concentrations inhibited the growth of C. vulgaris. The microalgal populations under heterotrophic growth conditions were one level of magnitude higher than that under autotrophic growth conditions that served as a comparison. No growth occurred in the dark in the absence of a carbon source. Na-acetate was superior to d-glucose. In municipal wastewater, when Na-acetate or d-glucose was added, C. vulgaris significantly enhanced ammonium removal under heterotrophic conditions, and its capacity was equal to ammonium removal under autotrophic growth conditions. This study showed that sterilized wastewater can be treated by C. vulgaris under heterotrophic conditions if supplemented with the appropriate organic carbon source for the microalgae.

Use of fermentative metabolites for heterotrophic microalgae growth: Yields and kinetics

“…As an illustration, it was previously reported that C. vulgaris could not use lactate for growth in mixotrophic conditions, and its presence was inhibitory to biomass growth . In contrast, the use of lactate by the same microalgal species was observed in heterotrophic conditions by Perez-Garcia et al (2011a). Therefore, the influence of lactate on biomass growth and on other substrates removal remains unclear for Chlorella sp.…”

Enhancement of FAME productivity of Scenedesmus obliquus by combining nitrogen deficiency with sufficient phosphorus supply in heterotrophic cultivation

“…Acetate, which can be derived from wastewater, is able to serve as an efficient carbon source for specific algae for heterotrophic cultivation [9]. Previous studies had demonstrated that the green microalga Scenedesmus obliquus was capable of assimilating acetate for biomass growth [10].…”

The effect of carbon source on nitrate and ammonium removal from drinking water by immobilised Chlorella sorokiniana

“…Some research claims that microalgae do not have invertase to assimilate sucrose; then, others in contrast to them indicated positive results when using sucrose. For instance, Perez-Garcia et al (2011a) found that supplementation with sucrose, Ca-acetate and vinegar supported meagre multiplication of C. vulgaris, whilst the absence of a carbon source completely inhibited multiplication. In contrast, during research into hydrogen production by immobilised C. vulgaris, sucrose produced the greater amounts of hydrogen from all carbon sources (Rashid et al 2013).…”

“…In accordance with the above reactions, carbon skeletons in the form of keto acids and energy in the form of ATP and NADH are required for this process (Perez-Garcia et al 2011a). Moreover, it was also reported that ammonium ions could interact with the carboxyl groups of the alginate beads (without microalgae) and chemically bound to it, which could also be reflected in the reduction of ammonium as they infiltrated continually through alginate into the cells (Ruiz-Marin et al 2010).…”

“…Algal treatment in the presence of carbon source was extensively studied by Kim et al (2013a) and some other researchers (Prathima Devi et al 2013) who reported promising results obtained with glucose. Sugars such as fructose and sucrose were also commonly used for the cultivation of microalgae (Ngangkham et al 2012;Perez-Garcia et al 2011a;Sun et al 2008). Only limited articles report about alternative carbon sources, such as molasses (Leesing and Kookkhunthod 2011;Olguín et al 2008;Vidotti et al 2014) and sweet sorghum (Gao et al 2010).…”