Novel Method Using Phycoremediation to Reduce Toxic Metals in Surface Waters

United States
Environmental
Protection Agency

A Novel Method Using Phycoremediation to
Reduce Toxic Metals in Surface Waters

N. Craft1, W. Canady1, E. Malcolm1, P. Rock1, M. Howard1, K. Henry1, X. Wang2 & M. Reese1
Virginia Wesley an University, 2 Old Dominion University

VIRGINIA
WESLEYAN
UN IVE RS ITY

Project Goal

Constructed wetlands (CWs) and stormwater management ponds (SWMPs) are popular
best management practices for reducing flood risk and removing pollution from
stormwater runoff. The challenge this project addresses is how to effectively manage
CWs and SWMPs to provide the known benefits of flood prevention and pollutant
removal, while also minimizing the potential for unintended consequences such as
methylmercury production and excessive algae growth.

CWs and SWMPs can increase property values by providing water views (Sander and
Polasky, 2009); however, these ponds are often plagued by algal blooms, which are
considered an eyesore and malodorous nuisance (Monaghan et al., 2016). Excessive algae
growth can also exacerbate the potential for methylmercury production if the pond
becomes eutrophic. Algae growth is most commonly combatted by algaecide application.
This project provides a viable alternative control strategy (eliminating the need for
algaecides), which is cost effective and simple to implement, with the added benefit of
removing pollutants as well as the excess nutrients which cause the blooms.

Figure 1. Filamentous algae growth in stormwater ponds on the campus
of Virginia Wesleyan University.

The research and design goals of the project are to

1) Evaluate phycoremediation as a strategy for reducing nutrient and metal pollution from
CWs and SWMPs.

2) Design and demonstrate a vermicomposting method for freshwater algae.

To our knowledge, this is the first study to evaluate phycoremediation for nutrients and
metals in stormwater ponds and the first study to use freshwater algae as a vermicompost
amendment.

Supporting Metal Decontamination
Research

It is well documented that mercury is a persistent and toxic pollutant of global concern
due to its neurological, immunological and cardiovascular effects. Atmospheric
deposition can bring mercury into watersheds via wet and dry deposition (Pirrone et al.,
2010). Once in a watershed, Hg can be methylated to methylmercury (MeHg), its more
toxic form which bioconcentrates and bioaccumulates in organisms (Selin, 2009). This
bioaccumulation is capable of damaging species populations, as well as local fisheries and
anyone who consumes seafood.

Cadmium has the ability to replace calcium in bones, which if present in enough
quantities, can cause brittle bone structure. Excess cadmium intake can also cause kidney
damage and is also thought to be a carcinogen (Morel and Malcolm, 2005). Lead has a
similar ability to replace calcium in bones, and it affects the development of the brain in
children (Baird and Cann, 2012).

When present in sufficient quantities, copper and zinc also act as toxins in the human
body. High intake of copper can create liver complications and problems with
reproductive health. While zinc is less toxic, excess quantities still can damage the
immune system and negatively affect cholesterol.

Waters that are polluted with mercury or other heavy metals pose a serious threat to
wildlife and humans alike.

The remediation of water through algae rather than vascular plants has multiple benefits.
Algae is often naturally present in ponds and bodies of wastewater, and is more often
that not removed instead of put to use. Algae has a fast growth rate with higher
photosynthetic capabilities than vascular plants, and it's renowned for its ability to
uptake nutrients and heavy metals from highly-polluted waters. Algae is tolerant to a
wide variety of conditions, and there exists multiple potential uses for harvested algal
biomass (Renuka et al., 2015).

This project aims to develop and demonstrate an innovative, cost-effective solution to
improve water quality outcomes from stormwater infrastructure by:

1) Reducing aquatic pollutants such as nutrients, heavy metals and mercury; thus,
minimizing harmful effects including eutrophication, metal toxicity and mercury
exposure by harvesting algae from CWs and SWMPs.

2) Producing high quality compost from vermicomposting waste algae to create a
valuable product through the application of sustainable principles, with the potential
for economic benefit.

Evaluation of Phycoremediation for Stormwater Ponds

A mesocosm experiment was used to evaluate the uptake of metals
and nutrients by filamentous algae collected from stormwater ponds.

3 + Nutrients
3 + Metals
3 No Spikes

Figure 5. Mesocosm tanks with
filamentous algae saw a more rapid
decrease in total mercury and other
heavy metals from the water column
than tanks with no algae. Algae
measurements confirmed that the
metals were taken up by algae.

Figure 2. Experimental design for mesocosm experiment:
Tanks were filled with lakewater; half received filamentous
algae, one third were spiked with nutrients, one third with
metals, and one third were not spiked.

Figure 3. Filamentous and microscopic green algae present,
includes: Mougeotia, Oedogonium, Spirogyra, Desmidium,
Hydrodictyon, Micrasterias

Figure 4. Mesocosm tanks
with filamentous algae
initially showed a more
rapid decrease in
phosphorous compared to
those without algae.

% Removed from the Water Column

P (P043 )

With
algae

26%

~50%

76%

63%

46%

Without
algae

16%

34%

27%

44%

35%

46%

Vermicompost from Filamentous Freshwater Algae

1.5x10"2 mg Hg, 2x10"2 mg Cd,
0.18 mg Cu, 0.51 mg Zn,
0.46 mg Pb in added algae
(per ~3 kg food waste)

4.3x10-4 mg Hg, 2x10^ mg Cd;
less than 5x10-3 mg Cu, Zn or
Pb in added algae
(per ~3 kg food waste)

Finished Compost Metal cone us Treatment

aziH iii

Figure 9. Heavy metal
concentrations in vermi-
compost with high metal
algae treatments appear
slightly elevated; however,
the difference from other
treatments is not
statistically significant.

Figure 6. Vermicompost was created in nine bins, all of which
contained cafeteria food waste. Six of the bins received
filamentous algae from the mesocosm tank experiment (half of
which had been spiked with metals).

Figure 7. Vermicompost
bins were stored in a
climate controlled
environment throughout
the composting process.
Finished compost and
leachate produced were
collected for further
analysis.

Heavy metals limits (ug/g) for European countries
which do have compost rules

Metal

Austria

Belgium

Canada

Germany

Netherlands

1.5

100

150

600

150

120

0.8

0.7

400

1000

500

400

280

Compost Standards and Guidelines, Brinton, Ed. 2000.

% 1

sEllEli

jRjBra&.v&i/"- .. Hi

Finished Compost Total N, P, Kvs

Treatment

gr 4

-j-

¦ No metal algae

¦ High metal algae

s „

Figure 10. Nutrient levels
in finished vermicompost
are consistent across
treatments and higher
than typical compost NPK
ratios: 1-5% : 0.3-0.5% :
0.4-0.8% (B.C. Agricultural
Composting Handbook. 1998).

Figure 8. The vermicomposting process successfully decomposed
the filamentous algae (dark green in image on left) as well as the
food waste (brown in image on left; eggshells can also be seen).

Values for total N, P, Kfrom Agricultural Analytical Services
Laboratory, Penn State University.

Algae was effectively decomposed with food waste to produce finished
vermicompost (Fig. 8).

Metai concentrations in finished compost, including high-metal algae
treatment, are well within limits laid out by European compost rules,
except for mercury. Primary source of the mercury is unknown, but
appears to be from the food waste.

Metal concentrations in vermicompost leachate was negligible.
Vermicompost is nutrient-rich compared to typical expectations for
compost, and is consistent across all three treatments.

Conclusions

First study to evaluate phycoremediation for nutrients and metals in
stormwater ponds.

Filamentous algae enhanced initial reduction of nutrient phosphorous from
mesocosm tank water.

Filamentous algae successfully removed total Hg, Cu, Cd, Zn, and Pb from
mesocosm tank water, demonstrating its potential for bioremediation of
stormwater and wastewater ponds.

First study to use algae as a vermicompost amendment.

The vermicomposting process successfully degraded freshwater filamentous
algae with food waste, demonstrating the potential for larger scale composting
of waste algae.

Future Work

Experimental successes showing significant reduction of metals in mesocosm
tank water will be followed up with further metals analysis of algae and
sediments collected to determine final fate of pollutants.

Preliminary success with vermicomposting algae will be repeated with higher
algae content while making efforts to optimize the vermicompost process
conditions.

Further experiments with finished compost will investigate germination and
plant growth. In addition to studying the success as a soil amendment, the
levels and fate of metals and potential uptake into plants will be explored.
Economic viability of widespread application of these practices across campus
will be investigated in terms of feasibility, cost/benefit analysis.

Thus far, this project has involved over 36 undergraduate students and lesson
plans on environmental science implemented for local 4th grade students.

We are currently replicating the vermicompost experiment using higher algae
percentages in each compost bin. Our current compost bins contain 18%
algae (by mass) or ~ a 1:5.5 ratio of algae to food waste. The bins in this
original experiment contained 1% algae, or ~ a 1:83.2 ratio of algae to food
waste. The algae we have chosen for this secondary experiment was all
sourced from local wastewater ponds on the Virginia Wesleyan campus.

Through adding more than five times the mass of algae that was added in this
original experiment, we hope to get a better picture of the ramifications of
using large percentages of algae in the vermicomposting process.

Cited References

Sander HA, Polasky S. 2009. Land Use Policy 26:837-845.

Monaghan P, etal. 2016. Environmental Management, 58:843-856.

Brinton, WP. 2000. Compost Standards and Guidelines. Woods End Research Laboratory, Inc.
1998, B.C. Agricultural Composting Handbook. BC Ministry of Agriculture, Food and Fisheries.
Pirrone, N, Cinnirella S, Feng X, Finkelman RB, Friedli HR, Leaner J, Mason R, Mukherjee AB,
Stracher GB, Streets DG, Telmer K. 2010. Global mercury emissions to the atmosphere from
anthropological and natural sources. Atmospheric Chemistry and Physics. 10:5951-5964.

Selin NE. 2009. Global Biogeochemical Cycling of Mercury: A review. Annual Review of
Environment and Resources. 34:43-63.

Morel FMM, Malcolm EG. 2005. The Biogeochemistry of Cadmium. Metal ions in Biological
Systems. 43:195-218.

Baird C, Cann M. 2012. Environmental Chemistry. New York, NY: W.H. Freeman and Company.
National Research Council (US) Committee on Copper in Drinking Water. Copper in Drinking
Water. Washington (DC): National Academies Press (US); 2000. 5, Health Effects of Excess
Copper.

Renuka N, Sood A, Prasanna R, Ahluwalia AS. 2015. Phycoremediation of wastewaters: a
synergistic approach using microalgae for bioremediation and biomass generation.
International Journal of Environmental Science and Technology. 12:1443-1460.

Fosmire, GJ. 1990. Zinc Toxicity. The American Journal of Clinical Nutrition. 51: 225-227.

Acknowledgements

Dr. William McConnell, Dr. Maynard Schaus; VWU students including: Arika Marosi,
Elizabeth Hippie, Gavin Steel, Phillip Venanzi, Michael Class, Kalli Koehn, Kat
Vanden Berg, Val Williams, Breanna Kokes, Marcos Davila-Banrey, Robert Jones,
Cassandra Caldwell, Kimberly Robillard, Emily Purdin and Christy Hendricks;
SOLIitude Lake Management and Norfolk Botanical Gardens.

Funding provided by U.S. E.P.A. P3 Student Design Competition and Virginia
Wesleyan University Undergraduate Research Program.

This presentation was developed under Assistance Agreement No. 66.516 awarded by the U.S. Environmental Protection
Agency to VWU. It has not been formally reviewed by EPA. The views expressed in this presentation are solely those of the
authors and do not necessarily reflect those of the Agency. EPA does not endorse any products or commercial services
mentioned in this publication.

-------