Transcript Los Angeles Department of Water and Power

ENVS 001: INTRODUCTION TO ENVIRONMENTAL SCIENCE, FALL 2013
Rice Husks as an Effective Means of Denitrification
BRENDA CAM, PEDRO CHANG, WARREN HE, KEVIN LAU, ERIC LEE and RUSSELL E. DI FIORI
Pasadena City College, Pasadena, CA USA
Introduction
Discussion
Figure 1
Figure 1a. A model of our design. In order for our bacteria to survive, they must dwell on a
nutritious carbon source (rice husks) and have a second source of nutrition. In essence, the main
Based on the data collected from this project, it can be concluded that
food source for our bacteria is oxygen because it is so abundant and nutrient-dense; when we
regarding the health of individuals as well as other living organisms,
rice husks are in fact effective in removing nitrates from water. In our
starve the bacteria of oxygen (by keeping it enclosed and sealed), its secondary food source
such as the use of genetically modified crops or what to do with
data, it is seen that there was slight increase in nitrate levels on Day 9
becomes nitrate (NO3-). When nitrate-filled water passes through our system, the bacteria will
electronic waste; however, one important issue that is often
and 10. This may be because the tube responsible for water flow was
take the nitrate in the water, break it down, and convert it to N2 gas. In doing so, nitrate breaks
overlooked is the cleanliness of the water being used by everyone in
clogged, which affected our results. Future research can implement
free from the water, thus reducing the amount of nitrates in the water6.
larger husk-filled systems or multiple husk-filled components to observe
Living in Los Angeles today, there are many issues that arise
A.
B.
the city. It may be difficult to believe, but there are an abundance of
Figure 1b. A plastic bottle was cut into four sections, and each section was tightly packed with rice
contaminants in L.A.'s drinking water, which in effect cause a
number of different ailments in those who drink the water. In 1974,
husks. Each section was separated by a platform of Gorilla Tape (punctured with a small hole for
the Environmental Protection Agency passed the Safe Water
water to pass through); the Gorilla Tape was sealed with the sectioned bottle using a hot glue
Drinking Act (SWDA) which, over the years, has worked to disinfect
gun. This method of sealing minimizes oxygen exposure to the rice husks. Three more layers
water from various waterborne pathogens1. Although effective, there
D.
C.
and test quicker flow rates. Also, other organic compounds such as
charcoal, sawdust, or wood chips can be used in conjunction with rice
husks to test for denitrification efficacy. We are confident that rice husks
are capable of greatly reducing the amount of nitrates in water, and can
be used in actual storm water runoff treatments.
were then stacked onto the existing platform.
are still a number of disease-causing chemicals present in today’s
Figure 1c. An additional layer of metal mesh was added to the top and bottom of the bottle to
water supply. In this project, one particular contaminant – nitrate – is
prevent leakage of the rice husk. We inverted our system for convenience.
studied extensively and treated accordingly from water. According to
a fact sheet posted by Colorado State University, nitrate (a chemical
Figure 1d. The husk-filled system was placed over a bottle containing nitrate-filled water, and both
commonly found in fertilizer and feces) is known to cause
systems were connected via a tube and a pump to allow for a cyclical flow of water. Water flowed
methemoglobinemia, a disorder that afflicts red blood cells and
through the system at around 8.2 liters per day, 24/7. We measured this using a graduated
causes oxygen deprivation over time2. Also, increased nitrate intake
cylinder and stopwatch. The denitrifying bacteria in the system (present in the rice husks) were
cause individuals to be at a greater risk of thyroid disease and
given 18 days to cultivate (occasionally switching out the nitrate-filled water with a new batch of
thyroid cancer3. Other symptoms include (but are not limited to)
water containing 50 mg/L nitrate), and samples were collected from that point.
4.
Figure 2
In order to reduce/eliminate nitrates in water, we created a
miniature system to simulate a real-life application of water treatment.
Because the general movement of water is a continuous directional
flow, we used a pump to simulate a continuous flow of water into our
Day
Nitrate
Concentration
(mg/L)
1
50
3
16
4
13.4
8
1.32
Denitrification Using Rice Husks
B.
60
Nitrate Concentration (mg/L)
A.
Methods
9
2.5
medium by which water passes through, which is highly applicable to
10
2.4
40
6.
30
20
"Fact Sheet: Stage 2 Disinfectants and Disinfection Byproducts Rule ."
United States Environmental Protection Agency. Office of Water, n.d.
Web. 23 Nov. 2013.
<http://www.epa.gov/safewater/disinfection/stage2/pdfs/fs_st2_finalrule
.pdf>.
Self, J.R., and R.M. Waskom. "Nitrates in Drinking Water." Nitrates in
Drinking Water. Colorado State University, 13 Nov. 2013. Web. 24 Nov.
2013. <http://www.ext.colostate.edu/pubs/crops/00517.html>.
Ward, MH, et al. "Nitrate intake and the risk of thyroid cancer and
thyroid disease." NCBI. U.S. National Library of Medicine, 21 May
2010. Web. 26 Nov. 2013.
<http://www.ncbi.nlm.nih.gov/pubmed/20335813>.
"Los Angeles Department of Water and Power." Los Angeles
Department of Water and Power. KPMG LLP, 30 June 2012. Web. 23
Nov. 2013. <http://www.ladwp.com>.
Shao, L, et al. "Rice Husk as Carbon Source and Biofilm Carrier for
Water Denitrification." Polish Journal of Environmental Studies. N.p., 8
Dec. 2008. Web. 1 Dec. 2013. <http://www.pjoes.com/pdf/18.4/693699.pdf>.
"Bioreactors, Water Table Management, and Water Quality." How
Bioreactors Work. University of Illinois Extension, 2013. Web. 1 Dec.
2013. <http://web.extension.illinois.edu/bioreactors/bioreactors.cfm>.
10
Acknowledgements
Time
the many lakes and streams scattered throughout Southern
nitrates from our water because it is highly productive. It works two-
5.
50
0
system. In our model, our system acts as a filter and a porous
California. We used rice husks as the main component in removing
2.
Results
purification for Los Angeles, so it is imperative to find cheap but
effective alternatives to the city’s overall water management4.
1.
3.
shortness of breath, dizziness, and stomach aches. Currently, it
costs over $6 billion in water investment, conservation, and
References
We would like to thank Professor Di Fiori for attentively assisting us
throughout the poster process and providing much needed insight on
Figure 2a. A numeric representation of the
Figure 2b. After 18 days of allowing the bacteria present in the rice husks to
our project. We would also like to thank Matthew Cui, Lizzie Beuyukian,
efficacy of the rice husks. Within 10 days,
cultivate, there is a noticeable decrease in the amount of nitrates in our
and Natalie Melgoza for tremendously helping us get started with our
fold: rice husk serves as both a carbon source (where bacteria is
nitrate levels decreased from 50 mg/L to
water. It is clear that rice husks are effective in removing nitrates from
design and our search for an efficacious carbon source.
cultivated) and a source of denitrifying bacteria5.
2.4 mg/L.
water.