Microalgal Activity and Nutrient Uptake from Wastewater Enhanced by Nanoscale Zerovalent Iron: Performance and Molecular Mechanism

Abstract

Microalgae-based bioremediation presents an alternative to traditional biological wastewater treatment. However, its efficiency is still challenging due to low microalgal activities and growth rate in wastewater. Iron plays an important role in microbial metabolism and is effective to stimulate microbial growth. In this study, a novel approach was proposed to simultaneously promote microalgal activity and nutrient uptake from wastewater using nanoscale zerovalent iron (nZVI), and the underlying molecular mechanism was explored. Compared to the control, 0.05 mg/L of nZVI significantly enhanced biomass production by 113.3% as well as NH4 +-N and PO4 3–-P uptake rates by 32.2% and 75.0%, respectively. These observations were attributed to the enhanced metabolic pathways and intracellular regulations. Specifically, nZVI alleviated the cellular oxidative stress via decreased peroxisome biogenesis as indicated by reduced reactive oxygen species, enzymes, and genes involved. nZVI promoted ammonium assimilation, phosphate metabolism, carbon fixation, and energy generation. Moreover, nZVI regulated the biosynthesis and conversions of intracellular biocomposition, leading to increased carotenoid, carbohydrate, and lipid productions and decreased protein and fatty acid yields. The above metabolisms were supported by the regulations of differentially expressed genes involved. This study provided an nZVI-based approach and molecular mechanism for enhancing microalgal activities and nutrient uptake from wastewater.

Effects of Light Energy with Different Densities on Denitrification: Metabolic Intermediates, Electron Behavior, Enzyme Activities, and Sludge Settleability

“…The SBR had been operated for over two years prior to experiments with stable nitrogen removal performance. The compositions of SMW shown in the SI Text1 . The LED light board used here had 80% similarity to solar irradiance to provide various light required in experiments (Kesheng Laboratory Instruments Co. LTD, NingBo, China).…”

“…The compositions of SMW shown in the SI Text1. 14 The LED light board used here had 80% similarity to solar irradiance to provide various light required in experiments (Kesheng Laboratory Instruments Co. LTD, NingBo, China).…”

Instant Inhibition and Subsequent Self-Adaptation of Chlorella sp. Toward Free Ammonia Shock in Wastewater: Physiological and Genetic Responses

“…The shift from nutrient removal to resource recovery has been attracting increasing attention in the field of municipal wastewater (MW) treatment. Microalgal bioremediation is one of the promising alternatives to conventional technologies due to its competitive advantages such as nutrient recycling with simultaneous production of value-added biomass. − However, its industrialization was largely limited by unstable microalgal activities in the MW treatment plant (MWTP), which experienced an abrupt change in nutrient loadings due to the fluctuations in both wastewater quality and quantity. Particularly, the periodic high-ammonium (NH 4 + -N) strength accompanied by the influent would lead to unsatisfactory microalgal growth and even the failure of the entire system. , …”

“…Moreover, one-sided explanations were reported that FA might suppress microalgal photochemical activities by destroying the oxygen-evolving complex (OEC) (through uncoupling the Mn cluster) and disordering non-photochemical quenching (through disturbing the internal pH of the thylakoid lumen). , Other metabolic activities (e.g., nutrient recycling) and multiple physiological resistances (e.g., antioxidant system and photoprotection process) were rarely investigated. For instance, photoprotection pathways [e.g., cyclic electron transport (CET) and decreased light harvesting] have been identified to ensure the continuation of photosynthetic activities. , All these metabolic and physiological responses to FA shock require further investigation.…”

“…For instance, photoprotection pathways [e.g., cyclic electron transport (CET) and decreased light harvesting] have been identified to ensure the continuation of photosynthetic activities. 8,16 All these metabolic and physiological responses to FA shock require further investigation. Insights into the subsequent microalgal self-adaptation after the FA shock inhibition are of practical importance for maintaining the operating stabilities of microalgae-based wastewater treatment systems.…”