Salt Tolerance and Desalination Abilities of Nine Common Green Microalgae Isolates

Abstract

In recent years, decline of freshwater resources has been recognized as one of the main environmental problems on global level. In addition to the increasing extent of primary salinization due to climate change, secondary salinization caused by human interventions is also a significantly increasing problem, therefore, the development of various chemical-free, biological desalination and removal procedures will become increasingly important. In the present study, the salinity tolerance, salinity, and nutrient reducing ability of nine common freshwater microalgae species from the genera Chlorella, Chlorococcum, Desmodesmus, Scenedesmus, and Monoraphidium were investigated. Our results proved that the studied green microalgae species are halotolerant ones, which are able to proliferate in environments with high salt concentrations. Furthermore, most of the species were able to reduce conductivity and remove significant amounts of chloride (up to 39%) and nutrients (more than 90% nitrate). The results proved that nitrate removal of the studied species was not influenced by salt concentration, only indirectly via growth inhibition. However, the results also highlighted that N:P ratio of the medium has primarily importance in satisfactory phosphorous removal. It can be concluded that assemblages of the studied microalgae species could be able to adapt to changing conditions even of salt-rich wastewaters and improve water quality during bioremediation processes.

Periphytic Algae and Cyanobacteria from the Rio Doce Basin Respond Differently to Metals and Salinity, Showing Different Potential for Bioremediation

“…For instance, the growth of Chlorococcum sp. was only significantly inhibited in NaCl concentrations higher than 10 g L −1 [39]. Similarly, S. elongatus cells tolerate NaCl at concentrations up to 23.37 g L −1 (0.4 M) [40,41].…”

“…Cell density and photosynthesis did not statistically change, even when cells were exposed to the highest NaCl concentration found in water of the Rio Doce Basin, demonstrating the salt-tolerance of S. elongatus and C. infusionum. Synechococcus elongatus and species of the genera Chlorococcum have been previously characterized as halotolerant and able to proliferate in environments with high salt concentrations [39,40]. For instance, the growth of Chlorococcum sp.…”

Effects of Nutrient Content and Nitrogen to Phosphorous Ratio on the Growth, Nutrient Removal and Desalination Properties of the Green Alga Coelastrum morus on a Laboratory Scale

“…However, the optimal N:P ratio for the treatment of municipal wastewater using microalgae is not well described. High nutrient concentrations with unfavorable N:P ratios could lead inadequate growth or nutrient removal: e.g., in our recent study all the tested nine green algae isolates showed poor phosphate removal from Bold's Basal Medium [20].…”

“…The experiments were carried out in model solutions with slightly different nitrate and phosphate concentrations and N:P ratios to represent how usual, not harsh fluctuations in wastewater composition could effect on biomass production and removal characteristics. On the basis of literature data and our previous findings [20] we hypothesized that:…”

Enhancement of Biomass and Calcium Carbonate Biomineralization of Chlorella vulgaris through Plackett–Burman Screening and Box–Behnken Optimization Approach

“…Temperature was the sole exogenous factor chosen. Since C. vulgaris is also halotolerant with recognizable desalination ability [ 30 ], the impact of salinity was included by adding sodium chloride to mimic the conditions from freshwater to the marine environment.…”