applied sciences Article  
Moringa oleifera Lam. as a Biofloculant for Harvesting Microalgae Grown on Agricultural Wastewaters for Feed Production  
[PERSON],*\({}^{\copyright}\), [PERSON], [PERSON]\({}^{\copyright}\), [PERSON]\({}^{\copyright}\) and [PERSON]  
Footnote 12  
membrane filtration and lower energy expenditure than centrifugation, even if associated with these operations for further dewatering of the harvested biomass [6]. The use of flocculation for harvesting algae grown on agricultural wastewaters has the further advantage of improving the quality of the spent growing medium to dischargeable levels. Chemical salts such as aluminium sulfate, iron (III) chloride, and iron sulfate are the most widely used for coagulation/flocculation in water treatment [7]. However, when used for the harvesting of microalgae, chemical salts can result in high metal contents in the final biomass [8; 9].Therefore, the choice of flocculant is very important and depends on the intended end-use of the biomass, as the flocculant/coagulant to be used should not contaminate or affect algae biomass quality; otherwise, this may result in additional costs for the purification of the produced biomass [9]. Bio-flocculants are naturally sourced flocculants of biological origin and are considered a sustainable alternative to commonly used chemical products due to their eco-friendly aspects for algae harvesting [9; 10; 11], especially for food and feed applications. One such bio-flocculant is the powder obtained from the seed of _Moringa_, a plant originally from South Asia that is capable of growing in arid regions. The _Moringa_ genus has 13 species known in the literature, and more than one of the species has coagulation/flocculation activity that has been tested in previous studies [12; 13; 14]. _Moringa oleifera_ Lam., the most cultivated and known species of the _Moringa_ genus, is called \"Miracle Tree\" since every part of the plant can be used in different fields such as wastewater treatment, pharmacy, food, and feed [15; 16; 17]. It has also been shown to be effective for microalgae harvesting, as its seeds contain a protein that can be used as a natural organic flocculant [18; 19]. In addition, it was shown to reduce bacterial content by 99.9% [20], an important aspect of the food and feed industry. Various studies have been conducted indicating that _Moringa oleifera_ seed can be used for harvesting different microalgae species. The study by [PERSON] et al. (2012) [18]_Chlorella vulgaris_ found a flocculation efficiency of 89% when 1000 mg L\({}^{-1}\)_Moringa oleifera_ seed flour was used. [PERSON] et al. (2021) [21] obtained a harvesting efficiency of around 95% for _C. vulgaris_ and _Scenedesmus obliquus_ upon addition of, respectively, 600 mg L\({}^{-1}\) and 400 mg L\({}^{-1}\) of _Moleifera_ seed powder. [PERSON] et al. (2016) [22] evaluated _Moringa oleifera_ seeds before and after oil extraction to harvest _Nanochloropsiscultata_. By adding 5000 mg L\({}^{-1}\) of _Moleifera_ seed after oil extraction, a 93.77% flocculation efficiency was obtained, while 70.56% was obtained with 4000 mg L\({}^{-1}\) using the non-extracted seeds. Even though several studies have evaluated _M. oleifera_ for microalgae flocculation with harvesting efficiencies above 80% [10; 18; 21; 22; 23], the lack of important information, such as the ratio of flocculant to algal biomass and the use of different methodologies for powder preparation, hamper the comparison of these works and the drawing of more general conclusions about the efficacy of this flocculant. Moreover, only a couple of studies have been carried out using _M. oleifera_ as a flocculant for harvesting microalgae grown on digestate [24; 25] and these have observed the need for a lower amount of flocculant than usually reported for _M. oleifera_ for microalgal harvesting.