Chromium-6 and Bioremediation OHO-Cr-OHO Paula Warren

What is Cr-6? Cr-6 is one of the most commonly occurring toxic pollutants present in wastewaters discharged from electroplating, dye and pigment manufacturing, wood preserving and leather tanning industries. Cr-6 is not only highly toxic, but also is mobile and has a long residence time in surface and groundwater. It poses a health risk to humans and animals, and impairs the development and growth of most plants. The main chemical dealt with in the Erin Brockovich toxic water case was Cr-6. O O O O O = Cr – O + oxidizing agent = O = Cr = O O O O O

The Study Choo T P; Lee C K; Low K S; Hishamuddin O Accumulation of chromium (VI) from aqueous solutions using water lilies (Nymphaea spontanea). Chemosphere (2006), 62(6), Journal code: ISSN: PubMed ID AN In-process for MEDLINE Water lilies were found to be able to survive in waters containing heavy metals. They are aesthetically pleasing, and do not interfere with crops on irrigated land or with fish production.

Using Water Lilies for Bioremediation The night bloomer tropical water lily (Nymphaea spontanea) have extensive roots and provide large surface area for the biofilm formation (the slimy layer) and thus enhance the microbial activities. Water lilies are able to extract the Cr-6 from the wastewater. The study shows how effective this method is.

How is the metal absorbed? -Plasma membrane and Passive Diffusion Passive diffusion is the simplest transport process as molecules moves across membrane without the help of any specific transport system. Molecules move across membrane and set up an equilibrium of concentration (driven by entropy considerations) Metal ions are adsorbed on the cell walls via passive diffusion or moved from the roots to the apex of the plant.

Results Cr-6 solutions at [ ] of 1, 2.5, 5, and 10 mg/l were used in the study to assess the metal accumulation of water lilies. pH= Also used a metal solution with Cu and Cr-6, since Cu commonly occurs with Cr-6 in electroplating wastewater. With an increasing metal [ ], the water lily increased the amount of Cr-6 it took up. ~16% uptake of its dry weight! % uptake= (C o – C e /C o ) x 100% C o = [initial], C e = [remaining Cr-6] C o = [initial], C e = [remaining Cr-6]

Removal of Cr-6 by water lilies after 7 days exposure (Table 1) Table 1. Removal of Cr(VI) by water lilies after seven days’ exposure Initial Cr(VI) concentration Cr(VI) concentration in plants Concentration factor (mg/l) (mg/g dry weight) a (mg/l) (mg/g dry weight) a ± ± ± ± a= Mean of three replicates ± standard error. So, there was an increased amount of Cr-6 a cumulated by the water lily with the increase of metal concentration. As the plant was introduced to more metal and Cr-6, it was able to continue to absorb at a higher amount.

Uptake of Cr-6 by water lilies exposed to different initial [Cr-6]. Fig. 1 Uptake of Cr(VI) by water lilies exposed to different initial Cr(VI) [ ]s. --initial [ ] 1.0 mg/l; --initial [ ] 2.5 mg/l; --initial [ ]5 mg/l; --initial [ ] 10 mg/l.

Cr-6 uptake increased in all the treatments (Cr-6 alone, both Cr-6 and Cu-2(bianary metal), and electroplating waste) for the first 5 days and then remained constant for the binary metal and the waste solutions, but continued to increase uptake in the singe metal solution. Cr(VI) accumulation by water lilies subjected to different treatments. ** single metal solution containing 2.5 mg/l Cr(VI); ** binary metal solution, ** waste solution, both containing 2.5 and 0.5 mg/l Cr(VI) and Cu(II), respectively; ** metal free control.

Using water lilies could be an effective, aesthetic way to reduce the harmful substance of Cr-6 from wastewater and electroplating refuge. Water lilies were observed to assist in bioremediation of this toxic chemical while still remaining healthy. May not be the Most effective resource for bioremediation, but it does not creep up on crops like duckweed does. Would be worth investing a small amount of $$ in to help reduce the amount of heavy metals in the wastewater, and to help reduce other, more costly methods of removed these metals. The Study: Choo T P; Lee C K; Low K S; Hishamuddin O Accumulation of chromium (VI) from aqueous solutions using water lilies (Nymphaea spontanea). Chemosphere (2006), 62(6), Journal code: ISSN: PubMed ID AN In-process for MEDLINE Conclusion