Growth, nitrogen utilization and biodiesel potential for two chlorophytes grown on ammonium, nitrate or urea

Abstract

Nitrogen removal from wastewater by algae provides the potential benefit of producing lipids for biodiesel and biomass for anaerobic digestion. Further, ammonium is the renewable form of nitrogen produced during anaerobic digestion and one of the main nitrogen sources associated with wastewater. The wastewater isolates Scenedesmus sp. 131 and Monoraphidium sp. 92 were grown with ammoni-um, nitrate, or urea in the presence of 5 % CO 2 ,and ammonium and nitrate in the presence of air to optimize the growth and biofuel production of these chlorophytes. Results showed that growth on ammonium, in both 5 % CO 2 and air, caused a significant decrease in pH during the exponential phase causing growth inhibition due to the low buffering capacity of the medium. Therefore, biological buffers and pH controllers were utilized to prevent a decrease in pH. Growth on ammonium with pH control (synthetic buffers or KOH dosing) demonstrated that growth (rate and yield), biodiesel production, and ammonium utilization, similar to nitrate-and urea-amended treatments, can be achieved if sufficient CO 2 is available. Since the use of buffers is economically limited to laboratory-scale experiments , chemical pH control could bridge the gap encountered in the scale-up to industrial processes.

Photoautotrophic Microalgae Screening for Tertiary Treatment of Livestock Wastewater and Bioresource Recovery

“…Regression analyses on growth kinetics also revealed that rapid growth in photosynthetic batch reactors is not that strongly associated with nitrogen condition, which was different from the findings of prior works [16,20]. In this study, obtained biomass productivity data evidenced that Chlorella emersonii is one of the promising candidates for the polishing of the secondary effluent of a livestock wastewater treatment plant.…”

Cultivation of marine microalgae using shale gas flowback water and anaerobic digestion effluent as the cultivation medium

“…Growth inhibition from high effluent concentrations is believed to be dependent on a combination of abiotic factors, such as free ammonia concentrations and the degree of turbidity (Eustance et al, 2013;Wang et al, 2010), as well as biotic factors, such as the presence of pathogenic or competitive bacteria (Ma et al, 2014). Additionally, these results suggest that either tolerance to these inhibitory factors or the ability to utilize effluent for cellular growth is algal strain-dependent.…”

“…Growth inhibition from high concentrations of ammonium can arise from the disassociation of ammonium into free ammonia (NH 3 ), a known inhibitory compound to microalgae (Eustance et al, 2013). A possible explanation for the lower average biomass productivity in the 6% AD + CS medium for D. tertiolecta is the lower ionic strength of the commercial salts compared to the flowback water.…”

Characterization of newly isolated oleaginous microalga Monoraphidium sp. for lipid production under different conditions

“…Purging of high concentration of CO 2 in the media converts NH 4 + to NH 3 and the cells are not able to control its introduction since it is a gas. This leads to an internal imbalance and further medium acidification, which triggers the degradation of chlorophyll and the resulting bleaching effect [29].…”