Removal of Cadmium from Controlled Water Systems using Spirulina platensisCarmen Cowo and Jim Bidlack

Department of Biology, University of Central Oklahoma, Edmond, OK 73034

Figure 3: The molecular effects in cells in conjunction with cadmium exposure (Waisberg et al. 2003).

LITERATURE CITED

Ahmad, A., Grufran, R., and Z. Wahid. 2010. Cd, As, Cu, and Zn Transfer through Dry to Rehydrated Biomass of Spirulina platensis from Wastewater. Polish Journal of

Environmental Studies. 19; 887- 893.

Lu, X. et al. 2004. Removal of Cadmium and Zinc by Water Hyacinth Eichhornia crassipes. Science Asia. 30: 93- 103.

Rangsayatorn, N. et al. 2002. Phytoremediation potential of Spirulina (Arthospira) platensis: biosorption and toxicity studies of cadmium. Environmental Pollution. 119: 45- 53.

Solosio, C. et al. 2008. Bioresource Technology. 99: 5933-5937.

Waisbrg, M. et al. 2003. Molecular and cellular mechanisms of cadmium carcinogenesis. Toxicology. 192: 95-117.

ACKNOWLEDGEMENTS

Funding for this project was provided by Office of Research & Grants at the University of Central Oklahoma (UCO). Many thanks to Jim Bidlack, Jocelyn Bidlack and Dr. Bidlack’s research group. The biology and chemistry department at UCO are also appreciated in providing materials and equipment during experimental processes.

RESULTS AND DISCUSSION

 The amount of microalgae biomass will affect the amount of cadmium that can be adsorbed from the water systems. A constant accumulation during exposure time is expected. Results should conclude that a low biomass of Spirulina platenis will remove more cadmium than a high biomass. However, that is also dependent on the concentration of cadmium that S. platensis is exposed to. The maximum sorption capacity will be calculated (Rangsayatorn et al. 2002). To determine the effective uptake for each exposed sample, biological concentration factors (BCF) will be calculated. This is determined by dividing the concentration of metal in the microalgae tissue by the initial concentration of the metal added to the water tanks (Lu. et al. 2004). To ensure the variability of data retrieved, two- way analysis of variance tests (ANOVA) will be used. Significant differences will be determined as well.

The results of these experiments will provide further knowledge on the uptake capacity of Spirulina platensis for cadmium and its optimal tolerance to the metal. These efficient methods can be introduced to expand development in phytoremediation strategies involving this species for projects of a larger scale.

MATERIALS AND METHODS

After receiving shipments of Spirulina platensis from UTEX Culture Collection of Algae, culturing and acclimation to the simulated water system will need to take place. S. platensis will be easy to maintain within these systems in that it is an easily adaptable species. An algae- growth medium will be added along with to deionized water to fill the tanks to 6-L. Water levels will be maintained (pH at 7.5) every day in that water loss will likely occur due to evaporation, sampling, and transpiration. The environmental chamber, which will house the tanks, will remain at a constant optimal temperature and humidity. Water oxygenation will be maintained by two air pumps which will supply all five tanks with oxygen using split- airline tubing.

Preliminary experiments will determine the optimal biomass at which Spirulina platensis will be able to remove cadmium from the experimental tanks without becoming nonviable. Once an optimal biomass has been determined, that amount will be cultured within each tank. Before cadmium addition, all five tanks will hold the same amount of algal biomass (will be weighed). Various concentrations of cadmium will be added to four of the tanks. The fifth tank will have no addition of cadmium and serve as a control. The concentrations of cadmium added will include the following: 1.0 mg/ mL, 1.5 mg/ mL, 2.0 mg/ mL and 2.5 mg/ mL. The cadmium used will be provided by a mixture of CdCl2 and H20. S. platensis will be exposed for 20 days with four replications.

Upon completion of the 20 day period, the biomass will be removed from all tanks by a filtration process and the use of Millipore membrane filters. Biomass will be weighed once again to determine final fresh weight. Water samples will be taken from each tank for metal content analysis. Concentration of cadmium present in the water after exposure period and concentration of cadmium accumulated within the Spirulina platensis biomass will be determined using atomic absorption spectrophotometry (Figure 2).

INTRODUCTION

Water pollution is clearly detrimental to the stability of ecosystems. There are numerous contributors to pollution (i.e. urbanization and industrialization). Human populations are rising and pollution control is an area of study that must be persistently addressed and refined. Waters can become contaminated by organic and inorganic substances in a variety of ways. The heavy metal cadmium is carcinogenic to human cells as shown in Figure 3 (Waisberg et al. 2003). One way cadmium can be introduced to environments is by the improper disposal of batteries.

Phytoremediation describes the use of living plants to bio absorb organic and inorganic pollutants from contaminated environmental sites, such as soil or water, and remain viable (Ahmad et al. 2010). Phytoremediation is a more environmentally friendly method for pollution clean- up. Another benefit it provides is that it is normally a low- cost process.

S. platensis is a microalgae, and more specifically, a cyanobacteria (blue- green algae). The surface of cells in cyanobacteriums are composed of various polysaccharides, proteins, and lipids. These molecules contain the functional groups necessary for heavy metals to bind with. S. platensis thrives worldwide. It is easy to culture and is known to withstand harsh environmental conditions. It has also been shown that even dried biomass of S. platensis can be rehydrated and still remain able to remove cadmium from simulated water systems and actual waste water (Ahmad et al. 2010). S. platensis is a worthy candidate for phytoremediation involving heavy metal contaminants (Rangsayatorn et al. 2002). Because it has been shown in literature that Spirulina platensis can remove cadmium from water systems and remain viable, it is my organism of choice for this project. Cultures of S. platensis will be obtained from the University of Texas Culture Collection of Algae (Figure 1). Cultures will be grown and inspected before experimentation begins.

Figure 1: Photo of Spirulina platensis provided by UTEX Culture Collection of Algae.

Figure 2: Atomic absorption spectrophotometer used in cadmium concentration analysis in Spirulina and “waste water.”