SORPTION AND RELEASE OF NICKEL AND ZINC USING A MIXED ALGAE COMMUNITY COLLECTED FROM A MINE DRAINAGE PASSIVE TREATMENT SYSTEM
Abstract
Mine water from upwellings in Commerce Oklahoma is treated by the Mayer Ranch Passive Treatment System (MRPTS) to remove contaminants. The last treatment section of MRPTS is referred to as the polishing pond (also known as cell 6). Nickel and zinc, toxic to both plants and animals when present in elevated concentrations, are still detectable at the effluent of the system out of cell 6. Research on phytoremediation for contaminants in water or soils has been around for decades. Some more recent research examines algae for sorption of metal contaminants from water to improve water quality. Research shows that living algae are capable of both adsorption and absorption of metals, whereas dead algae can only adsorb metals due to the absence of metabolic processes. Previous exposure to metal contaminants influences the levels of uptake of metals by algae as well as growth rates when contaminants are present. Researchers have hypothesized that metals will be released from algae detritus as the algae decomposes, but not enough research has been published on desorption or release of metals due to decomposition.
In this research, nickel and zinc sorption and release by a community of mixed algae species collected from MRPTS were examined. Equal concentrations of nickel and zinc were used in solutions of 0.5, 2.0, 5.0, 10.0, and 20.0, mg/L Ni and Zn. A solution of MRPTS final cell effluent water with no addition of nickel or zinc was included, along with a no algae control solution with 10.0 mg/L Ni and Zn for comparisons of results. The samples were exposed to Photosynthetically Active Radiation (PAR) light at 20 °C for five days for the growth phase. The algae were then exposed to 0 °C without light for two days for the chilled phase which was used to promote algae death. Lastly, the algae were placed at 20 °C without the presence of light to promote decomposition of the algae material. The algae and solution of each sample at the end of each phase were processed using microwave assisted acid digestions to extract the metals present in the samples. The samples were then analyzed using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES).
The data obtained by this experiment showed that there was sorption of both nickel and zinc by the algae community during the growth phase. The algae released a portion of the previously sorbed metals during the chilled phase. Instead of the data showing release of metals during decomposition of the algae, the samples showed continued sorption under the conditions for decomposition. The greater concentrated solutions had greater levels of sorption by the algae. The data indicate that algae and its decomposing material are both capable of removing and retaining nickel and zinc from contaminated waters. Natural algae populations within passive treatment systems (PTS) can provide additional water treatment. Effects of seasonality on the potential of water treatment by algae, along with sorption and release of other metals by algae, still needs further study for definitive results.
Collections
- OU - Theses [2217]