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.
Highlights
The rise in the world population and the increasing use of natural resources which have occurred during the last century have caused strong alterations to the environment
The aim of this work was to isolate promising autochthonous microalgae from the effluent derived from the thickening step of the wastewater treatment plants (WW-TP) located in Ferrara (Italy) to be employed in an eco-friendly phytoremediation treatment to improve the performance of the WW-TP
The most abundant lower layer of material grown in the urban wastewater (UWW) allowed us to obtain a mixture of not-flagellate and relatively small-size algal cells: some of the microalgal material was formed by almost spherical cells (10–15 μm in size) with an external evident envelope (Figure 1e), while small, spherical cells
Summary
The rise in the world population and the increasing use of natural resources which have occurred during the last century have caused strong alterations to the environment. As it is known, the world overpopulation is gradually increasing the demand for freshwater, especially in cities, leading to a consequent increase in wastewater production [1,2]. Phosphorus (P); it cannot be directly released into natural environments or reused As a consequence, it is normally recirculated in the WW-TP for N and P abatement before discharge.
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