Phycoremediation of wastewaters: a synergistic approach using microalgae for bioremediation and biomass generation

Abstract

Discharge of untreated domestic and industrial wastewater into aquatic bodies is posing a serious eutrophication threat, leading to a slow degradation of the water resources. A number of physical, chemical and biological methods have been developed for the treatment of wastewaters; among these, the use of microalgae is considered as a more eco-friendly and economical approaches. Microalgae are versatile organisms which perform multiple roles in the environment-bioremediation of wastewater, gleaning of excess nutrients and in turn, generate valuable biomass which finds applications in the food, biofuel and pharmaceutical industries. They are currently being utilized to reduce the high nutrient load (especially N and P) from wastewaters, which fulfill the growth requirements of microalgae, making it a suitable cultivation medium for biomass production. The present review represents a comprehensive compilation of reports on microalgal diversity of wastewaters, followed by a critical overview of their utilization, suitability and potential in bioremediation vis-a-vis biomass production. This review also emphasizes the superiority of polyalgal and consortial approaches in wastewater treatment, as compared to the use of unialgal inocula, besides providing useful pointers for future research needs in this area.

Advanced nutrient removal from surface water by a consortium of attached microalgae and bacteria: A review

“…A new bioremediation approach is to use the consortia of attached microalgae and bacteria, which are ubiquitous at solid surfaces including plants, sediments and stones in surface water (Larned, 2010;Wu et al, 2014;Renuka et al, 2015). Microalgae have the ability to assimilate inorganic nitrogen and phosphorus down to very low concentrations (e.g., less than 0.5 and 0.03 mg L À1 for TN and TP, respectively) (Boelee et al, 2011;Renuka et al, 2013;Liu and Vyverman, 2015), while bacteria can remove nutrients via assimilation, anaerobic ammonia oxidation, nitrification and denitrification for nitrogen (Yao et al, 2013;Fitzgerald et al, 2015) and regular and luxury uptake of phosphorus (Schmidt et al, 2016).…”

“…Liu et al (2016c) installed microalgae-bacteria consortium under a planted floating treatment bed to improve the in-situ remediation efficiency of deep and static river water. Overall, the large number of existing photobioreactor configurations facilitate the application of attached microalgae-bacteria consortium for the treatment of polluted surface waters (Mulbry et al, 2008;Renuka et al, 2015). Additionally, the simultaneous action of the diverse nutrient removal pathways present in attached microalgae-bacteria consortium support the reduction of nitrogen and phosphorus in surface water as well as other kinds of wastewater to low levels (e.g., less than 2 and 0.1 mg L À1 for TN and TP, respectively, Table 4).…”

“…To date, a large number of studies have investigated the habitat and pollutant removal capacity of various attached microalgal and bacterial species in monoculture as well as in consortium (Renuka et al, 2015;van Kessel et al, 2015;Liu et al, 2016a). Great phylogenetic differences were observed in growth rate, nutrient removal capacity and preferred habitat among microbial groups (Beuckels et al, 2015;González-Camejo et al, 2017).…”

“…Similarly, the dominance of cyanobacteria and green algae with high affinity for nitrate will promote the removal of this oxidized nitrogen form (Renuka et al, 2013). Unfortunately, most studies conducted to date only monitored the consortium changes but without artificial intervention (Adey et al, 2013;Boelee et al, 2014;Renuka et al, 2015). In the future, more attention should be paid to the community control through genetic, ecological, chemical and physical approaches (Lindemann et al, 2016).…”

“…Since the middle of the 20th century, surface water pollution caused by excessive nutrient input from anthropogenic activities has become a severe threat to water resource sustainability and ecological safety worldwide (Renuka et al, 2015). In recent decades, nutrient discharge from point sources has been gradually reduced, but non-point sources are still poorly controlled (Xiang et al, 2017).…”