Multipurpose Agricultural Reuse of Microalgae Biomasses Employed for the Treatment of Urban Wastewater

Abstract

The pollution of water caused by the excessive presence of organic and inorganic compounds, such as nitrates, phosphates, heavy metals, antibiotics, agrochemicals, etc., is one of the major environmental problems in many countries. Various approaches to remediate wastewater are available, and this review mainly provides the state of the art about the possible adoption of microalgae-based treatments (phycoremediation), which may represent a good alternative to conventional purification methods. Because of its composition, wastewater can provide several nutritional compounds (e.g., carbon, nitrogen, and phosphorus), which represent the essential nutrients for microalgae growth. Microalgae are also attracting the interest of worldwide researchers due to their multipurpose applications; in particular, microalgae cells can represent a useful feedstock for various sectors, among these, the agricultural sector. This review proposes a detailed description of the possible application of microalgae in the process of remediation of wastewaters of different sources, highlighting their possible advantages. Moreover, the review aims to report the application of the microalgae biomasses and their extracts in agriculture, as microalgae-based products can represent a valid alternative to traditional agrochemicals, offering sustainable solutions to improve agricultural technologies. Therefore, since the recently developed wastewater depuration technology based on phycoremediation may directly provide valuable microalgae biomasses, it can be used as a powerful starting means to produce agricultural products able to improve yield and quality of crops (biostimulants, biofertilizers), as well as induce pest and disease resistance (biopesticides).

Effects of microalgae and compost on the yield of cauliflower grown in low nutrient soil

“…on tomato (Solanum lycopersicum) crops, where DW was increased by 32% (Jimenez et al, 2020). Similarly, the use of microalgae as biofertilizer has been tested in lettuce, rice, eggplant, cucumber, resulting in improved plant growth, among other benefits (La Bella et al, 2022).…”

“…The most relevant results in this study were obtained with the microalgae plus compost mixture and its application is recommended. In some cases, microalgae-based amendments may have a higher production cost (La Bella et al, 2022). However, scientific advances to reduce costs are growing by leaps and bounds and it has been reported, for example, the production of microalgae using wastewater as a source of nutrients, to improve the production process from nutrient recovery and water recovery from these effluents (La Bella et al, 2022).…”

Comparative Phycoremediation Performance of Three Microalgae Species in Two Different Magnitude of Pollutants in Wastewater from Farmhouse

“…The high concentration of pollutants, such as excess nitrogen and phosphorus, may cause an important alteration in the health of the water system [4,5]. Furthermore, conventional treatment methods, such as activated sludge systems or chemical coagulation, are still very expensive and often unable to completely eliminate microcompounds or inorganic nutrients [6,7].…”

“…In this context, the exploitation of microalgae is emerging as an interesting alternative green source with a low carbon dioxide (CO 2 ) footprint [15,16]. Microalgae are also attracting the interest of worldwide researchers, mainly due to their multipurpose applications as raw materials for the development of new agricultural products [7,17,18]. Moreover, microalgae are taken into account as important sustainable sources of valuable chemicals, pharmaceuticals, and other products [19][20][21].…”

Screening of several microalgae revealed biopesticide properties of Chlorella sorokiniana against the strawberry pathogen Phytophthora cactorum

“…In recent years, scientists suggested using microalgae as biopesticides to reduce or even replace the use of synthetic chemicals for pest control (Righini and Roberti 2019; La Bella et al 2022). It is known that many microalgae are capable of producing allelopathic chemicals with antimicrobial or antifungal activity (Ördög et al 2004; Le aive and TenHage 2007; Shishido et al 2015;Falaise et al 2016; Swain et al 2017).…”