# Microalgae Water Bioremediation: Trends and Hot Topics
## 3 Bibliometric Performance Analysis
### Content Analysis
This framework also launched the environmental goal of developing alternative WWT in detriment to the traditional WWT, aiming at nutrient recovery and recycling [84]. Furthermore, in the European Union, the Water Framework Directive, published in 2000, addresses and encourages the improvement of urban wastewater treatment with biological methods. More recently (2016), the Government of the Republic of Lithuania has, inclusively, approved a management plan in order to reduce the nutrient input in the Baltic Sea [47]. Microalgal biomass is a valuable resource with potential applications in several industries and is a key factor in the blue economy because of the value of its commercial applications and for being an alternative to land-based products or non-renewable resources. Hence, microalgae have gained increasing attention by the academia, industry and policy makers, especially since 2001. In the last analyzed decade (2011-2018) (Figure 3d), the main motor-themes were: \"cultivation\", \"aqueous-solution\", \"diatoms\", \"fatty-acids composition\", \"high rate algal-ponds\" and \"pharmaceuticals\". Advances of more sensitive analytical equipment and methods led to the determination and identification of emerging water pollutants in aquatic ecosystems [85] resulting from human activities, such as pharmaceuticals, personal hygiene products, chemical cleaning agentsand natural or synthetic hormones [86]. Under the scope of the European framework of the Water Directive and Wastewater Treatment Directive, numerous projects have been funded to overcome the challenge of water-emerging contaminants. Networks among reference laboratories, research centers and related organizations were created to monitor emerging environmental substances (NORMAN) and develop a database of geo-referenced monitoring and bio-monitoring data on emergent substances in water [87]. Studies regarding the use of microalgae as bioremediators of contaminated effluents were, as previously mentioned, conducted. Furthermore, ecotoxicological studies have been carried out with diatoms or other microalgae, which are primary producers and present higher sensitivity in the marine environment in comparison to other organisms [17]. The toxicological effects of fossil fuels [88], organophosphorus compounds [89] and polycyclic aromatic hydrocarbons [90], easily found in water, on microalgae were also studied. Nevertheless, some strains of microalgae were shown to be resilient with acclimatization capability through biochemical and physiological modifications [6]. High-rate algal ponds (HRAPs) have demonstrated feasibility at an operational and economical level for bioremediation of a secondary effluent from a wastewater treatment plant. [PERSON] and [PERSON] (2017) obtained a 60%-80% and 60%-70% nitrogen (N) and phosphorous (P) removal, respectively, in a HRAP system [16]. Furthermore, a mixed freshwater population, in which _Tetradesmus dimorphus_ (Chlorophyta) dominated, was shown to successfully grow in a HRAP system and to deplete different types of pharmaceuticals. Removal rates higher than 90% on pharmaceuticals, namely atenol, atracurium, bisoprolol, bupropion, citalopram, diltiazem and metoprolol were reported [11; 91]. The production of microalgal biomass into bioproducts is also a current theme of research and will promote the manufacture of innovative biological products as well as the creation of employment [47]. Photosynthetic microorganisms are efficient producers of high-value compounds, like polyunsaturated fatty acids (PUFAs) [92]. Studies showed that n-3 PUFAs have therapeutic properties, namely in cardiovascular and mental diseases [93]. Furthermore, it is important to characterize microalgae lipidic and protein content in order to understand the range of bio-products that can be developed.