Chromium-6 and Chromium-6 and BioremediationBioremediation

OO

HO-Cr-OHHO-Cr-OH

OO

Paula Warren

What is Cr-6?What is Cr-6?Cr-6Cr-6 is one of the most commonly occurring toxic pollutants is one of the most commonly occurring toxic pollutants

present in present in wastewaters wastewaters discharged from electroplating, dye discharged from electroplating, dye and pigment manufacturing, wood preserving and leather and pigment manufacturing, wood preserving and leather tanning industries. Cr-6 is not only tanning industries. Cr-6 is not only highly toxichighly toxic, but also is, but also is mobilemobile and has a and has a long residence timelong residence time in surface and in surface and groundwater. It poses a health risk to humans and animals, groundwater. It poses a health risk to humans and animals, and impairs the development and growth of most plants. and impairs the development and growth of most plants.

The main chemical dealt with in the Erin Brockovich toxic water The main chemical dealt with in the Erin Brockovich toxic water case was Cr-6. case was Cr-6.

OO O O O = Cr – O + oxidizing agent = O = Cr = OO = Cr – O + oxidizing agent = O = Cr = O OO O O

The StudyThe StudyChoo T P; Lee C K; Low K S; Hishamuddin O Choo T P; Lee C K; Low K S; Hishamuddin O Accumulation of chromium Accumulation of chromium

(VI) from aqueous solutions using water lilies (Nymphaea (VI) from aqueous solutions using water lilies (Nymphaea spontanea)spontanea). Chemosphere (2006), 62(6), 961-7. Journal code: . Chemosphere (2006), 62(6), 961-7. Journal code: 0320657. ISSN:0045-6535. PubMed ID 16081131 AN 2006069706 In-0320657. ISSN:0045-6535. PubMed ID 16081131 AN 2006069706 In-process for MEDLINEprocess for MEDLINE

Water lilies were found to be able to Water lilies were found to be able to survive in waters containing heavy survive in waters containing heavy metals. They are aesthetically metals. They are aesthetically pleasing, and do not interfere with pleasing, and do not interfere with crops on irrigated land or with fish crops on irrigated land or with fish production.production.

Using Water Lilies for Using Water Lilies for BioremediationBioremediation

The The night bloomer tropical water lilynight bloomer tropical water lily ( (Nymphaea Nymphaea spontaneaspontanea) have extensive roots and provide large surface ) have extensive roots and provide large surface area for the biofilm formation (the slimy layer) and thus area for the biofilm formation (the slimy layer) and thus enhance the enhance the microbial activities. microbial activities.

Water lilies are able to extract the Cr-6 from the wastewater. Water lilies are able to extract the Cr-6 from the wastewater. The study shows how effective this method is. The study shows how effective this method is.

How is the metal How is the metal absorbed?absorbed?

-Plasma membrane and Passive -Plasma membrane and Passive DiffusionDiffusion

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.

ResultsResults

Cr-6 solutions at [ ] of 1, 2.5, 5, and 10 mg/l were Cr-6 solutions at [ ] of 1, 2.5, 5, and 10 mg/l were used in the study to assess the metal accumulation used in the study to assess the metal accumulation of water lilies. pH=6.0-6.5. Also used a metal of water lilies. pH=6.0-6.5. Also used a metal solution with Cu and Cr-6, since Cu commonly solution with Cu and Cr-6, since Cu commonly occurs with Cr-6 in electroplating wastewater. occurs with Cr-6 in electroplating wastewater.

With an increasing metal [ ], the water lily increased With an increasing metal [ ], the water lily increased the amount of Cr-6 it took up. ~16% uptake of its the amount of Cr-6 it took up. ~16% uptake of its dry weight!dry weight!

% uptake= (C% uptake= (Co o – C– Cee/C/Coo) x 100%) x 100%

CCoo = [initial] , C = [initial] , Ce e = [remaining Cr-6]= [remaining Cr-6]

Removal of Cr-6 by water Removal of Cr-6 by water lilies after 7 days exposure lilies after 7 days exposure

(Table 1)(Table 1)Table 1.Table 1.

Removal of Cr(VI) by water lilies after seven days’ exposureRemoval of Cr(VI) by water lilies after seven days’ exposureInitial Cr(VI) concentration Initial Cr(VI) concentration Cr(VI) concentration in plants Cr(VI) concentration in plants Concentration factorConcentration factor

(mg/l)(mg/l) (mg/g dry weight) a(mg/g dry weight) a

1.01.0 0.775 ± 0.0220.775 ± 0.022 9469462.52.5 1.374 ± 0.0991.374 ± 0.099 6556555.05.0 1.467 ± 0.0631.467 ± 0.063 31931910.010.0 2.119 ± 0.0932.119 ± 0.093 225225

a= Mean of three replicates ± standard error.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.

Amount Cr Uptake in Plants from Inital Solution Concentrations

0

0.5

1

1.5

2

2.5

1 2.5 5 10

Initial Concentration (mg/l)

Rem

ove

d b

y P

lan

t (m

g/g

)

Uptake of Cr-6 by water Uptake of Cr-6 by water lilies exposed to different lilies exposed to different

initial [Cr-6]. Fig. 1initial [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 Cr-6 uptake increased in all the treatments (Cr-6 alone, both Cr-6 treatments (Cr-6 alone, both Cr-6 and Cu-2(bianary metal), and and Cu-2(bianary metal), and electroplating waste) for the first 5 electroplating waste) for the first 5 days and then remained constant for days and then remained constant for the binary metal and the waste the binary metal and the waste solutions, but continued to increase solutions, but continued to increase uptake in the singe metal solution. 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 Using water lilies could be an effective, aesthetic way to reduce the harmful substance of Cr-6 from to reduce the harmful substance of Cr-6 from wastewater and electroplating refuge. Water lilies wastewater and electroplating refuge. Water lilies were observed to assist in bioremediation of this were observed to assist in bioremediation of this toxic chemical while still remaining healthy. toxic chemical while still remaining healthy.

May not be the Most effective resource for May not be the Most effective resource for bioremediation, but it does not creep up on crops bioremediation, but it does not creep up on crops like duckweed does. like duckweed does.

Would be worth investing a small amount of $$ in to Would be worth investing a small amount of $$ in to help reduce the amount of heavy metals in the help reduce the amount of heavy metals in the wastewater, and to help reduce other, more costly wastewater, and to help reduce other, more costly methods of removed these metals. methods of removed these metals.

The Study:The Study:Choo T P; Lee C K; Low K S; Hishamuddin O Choo T P; Lee C K; Low K S; Hishamuddin O Accumulation of chromium (VI) Accumulation of chromium (VI)

from aqueous solutions using water lilies (Nymphaea spontanea)from aqueous solutions using water lilies (Nymphaea spontanea). . Chemosphere (2006), 62(6), 961-7. Journal code: 0320657. ISSN:0045-Chemosphere (2006), 62(6), 961-7. Journal code: 0320657. ISSN:0045-6535. PubMed ID 16081131 AN 2006069706 In-process for MEDLINE6535. PubMed ID 16081131 AN 2006069706 In-process for MEDLINE

Conclusion