Removal of Nitrogen and Phosphorus from Thickening Effluent of an Urban Wastewater Treatment Plant by an Isolated Green Microalga

Abstract

Microalgae are photosynthetic microorganisms and are considered excellent candidates for a wide range of biotechnological applications, including the removal of nutrients from urban wastewaters, which they can recover and convert into biomass. Microalgae-based systems can be integrated into conventional urban wastewater treatment plants (WW-TP) to improve the water depuration process. However, microalgal strain selection represents a crucial step for effective phytoremediation. In this work, a microalga isolated from the effluent derived from the thickening stage of waste sludge of an urban WW-TP was selected and tested to highlight its potential for nutrient removal. Ammonium and phosphate abatements by microalgae were evaluated using both the effluent and a synthetic medium in a comparative approach. Parallelly, the isolate was characterized in terms of growth capability, morphology, photosynthetic pigment content and photosystem II maximum quantum yield. The isolated microalga showed surprisingly high biomass yield and removal efficiency of both ammonium and phosphate ions from the effluent but not from the synthetic medium. This suggests its clear preference to grow in the effluent, linked to the overall characteristics of this matrix. Moreover, biomass from microalgae cultivated in wastewater was enriched in photosynthetic pigments, polyphosphates, proteins and starch, but not lipids, suggesting its possible use as a biofertilizer.

Chlorophyta microalgae as dietary protein supplement: a comparative analysis of productivity related to photosynthesis

“…Cell density was evaluated using a Thoma haemocytometer (HBG, Giessen, Germany) and plotted on a logarithmic scale to obtain growth kinetics. Cell density was also employed to estimate the specific growth rates during the exponential phase (μ, day −1 ) (Giovanardi et al 2013;Baldisserotto et al 2020). Parallelly, growth of samples was also estimated by measuring the OD 750 .…”

Characterization of Neochloris oleoabundans under Different Cultivation Modes and First Results on Bioactivity of Its Extracts against HCoV-229E Virus

“…Cell densities were plotted on a base 2 logarithmic scale to obtain the growth kinetics. On the basis of cell densities, growth rates (µ; d −1 ) were calculated, as well, using the following formula: µ (d −1 ) = (log 2 N 1 − log 2 N 0 )/(t 1 − t 0 ) where µ is the growth rate, N 1 the cell number at time t 1 , N 0 the cell number at time 0 and t 1 − t 0 the time interval (days) [ 72 ].…”

“…Algae samples were harvested by centrifugation (8000× g , 10 min), and the extraction of photosynthetic pigments was performed with absolute methanol according to [ 10 , 72 ]. The methanolic extracts were manipulated under dim green light to avoid photo-degradation.…”

“…Then, cells were dehydrated in acetone series and embedded in Araldite resin. Ultrathin sections were finally stained with lead citrate and uranyl acetate [ 72 ]. For observations, a Zeiss EM910 (Electron Microscopy Center, University of Ferrara, Ferrara, Italy) was employed.…”

A new Desmodesmus sp. from the Tibetan Yamdrok Lake

“…Studies have shown that microalgae can remove various pollutant from wastewater, such as oxygen consuming pollutants, nitrogen, phosphorus, heavy metals, organic matter, and absorb harmful gases such as NO X , SO X , and H 2 S at a certain concentration. The biomass harvested from wastewater treatment can also be utilized as raw materials for biofuel, feed, and chemical compounds [4][5][6][7][8][9]. Microalgae can use CO 2 during photosynthesis as the only carbon source for heterotrophic growth and can use external carbon sources for heterotrophic growth to improve the biomass and oil content of microalgae [10,11], which can greatly reduce global emissions of greenhouse gases such as CO 2 [12].…”