Towards Clean Water Combining Multiple Filtration and Disinfection Techniques
D. Anable, A. Davenport-Herbst, D. Riddle,
J. Robinson, T. Roy, R. Sanchez, ,M. Smith, J. Blandon
Abstract
Results and Discussion – E-F
Filtration
Conclusions
We are working on a research project in which we are
designing and building a water treatment system for an underprivileged community in Colombia. Our plan is to implement a
2-stage system in which we will filter and disinfect water from
a flowing stream to provide safe water for people in this
community for everyday use. Right now, our plan involves
introducing bleach into the water, using a multi-layer filtration
system, which includes using sand-like media of various sizes
to filter the water, reverse osmosis, and a UV source with a
proper setup to disinfect it. We will also be creating a
generator specifically for this stream in which we will use the
flow of the water from the stream to produce our own source
of electrical energy in order to provide power to our UV setup.
We will be using 3-D printing techniques to produce parts for
this system. We will construct a sensor that will focus on
testing the turbidity levels of the water. In addition, we will also
create teaching modules for grade school kids as well as do
some K-12 educational work with electro-flocculation along
with Elequatech from San Antonio, TX.
The water was tested after flocculation but before filtering
by using a pipet to take water from the middle of the batch
and in an area free of flocculated material. Because of
time restraints with the Biological Tester, after initial
testing, a sample of each voltage batch was filtered and
tested again while the other sample was filtered and sent
for biological testing. The water hardness was tested
using a Hach hardness testing kit. All equipment was
cleaned with deionized water between tests.
The filter we used was of sand and zeolite coal that was
backwashed using tap water before each tested batch
was filtered.
We have designed and tested several filtration prototypes.
The image on the bottom left, the latest prototype, shows
results that are useful in the removal of inorganic material.
This filter uses a combination of course sand of various sizes
along with activated carbon. We got optimal results when the
filter contained ¾ activated carbon (left chamber all activated
carbon) and ¼ course sand (right chamber ½ activated
carbon and ½ course sand). By putting the activated carbon
first, we can add a bleach system to this filtration system to
help the disinfection process since activated carbon has a
property that absorbs bleach. This pressurized up flow filter
shown on the bottom right image has one chamber in which
water flows upward due to the pressure created by the pump.
This design is crucial because it helps prevent media from
cementing together during the up flow process. Once the
water passes through chamber one, the water then flows
down chamber two since the design of the filter is vertically
resting.
As shown in our post flocculation results, Electrode
Coagulation is a very effective means to remove hardness in
the water. Also, an interesting thing to note is that after
filtration the hardness of the water increased instead. We
believe this is most likely caused by the backwashing of the
filter using tap water which is very hard. When testing the UV
system, we exposed water with colonies of bacteria directly to
the UV-C light. Since FEP tubing allows a high percentage of
UV-C light to pass though it, exposing the water with bacteria
colonies directly to the UV light should have similar results as
placing the water in the FEP tube then exposing it to UV light.
Table 1 shows the number of colonies counted for each
exposure trial and an average for each time was recorded for
a fixed distance of 10cm from the UV light. The average
values for each time was placed into a scatter plot and an
exponential trend line was added as shown in Figure 1.
Goals
• Design a multistage system that will eliminate
contaminants not suitable for human consumption.
• Build the system based on our design and water source
Post Flocculation, Pre filtration:
Note: The test is accurate to 17.1 mg/L.
Note: Batch 2 was not used because there was not an
area that was adequately free of floc. The floc prevented
the test from working properly.
UV Disinfection
• Test our design to make sure it provides water that
meets world standards for safe consumption
3-D Printing
We have been testing and idealizing the production of parts
capable of fitting our project needs from the method of 3-D
printing. At this point, we have investigated and produced
parts using printer filaments, which are a mixture of plastic
and metals. The parts created using the 3-D printing process
are durable and have antimicrobial properties since the
filament can be a mixture of plastic, brass, and silver.
Electro-Flocculation
• Electro-Flocculation: We flocculated the water using the
Electrode Coagulation method by putting a current
through two parallel strips of a metal alloy attached to
the lid and submerged in the water and placed slightly
apart at various voltages for 45 minutes. The metal alloy
rusts as coagulation happens because the metal ions
donate themselves as a particle for coagulation to
happen on.
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Table 1
Note: The test is accurate to 17.1 mg/L
Power Generator
Since our system will require a power source and the
community this project is aimed for has little available
electricity, we constructed power generator that uses the flow
of a water in a stream to provide energy. Water will enter a
PVC pipe and then be forced out of 4 smaller PVC pipes. The
water leaving the smaller PVC pipes will have higher pressure
due to Bernoulli's principle. This water will be aimed towards
propellers in order to make them spin and start the alternator
for power. We are also looking into using solar panels to
power the UV system and Electro-Flocculation process.
Thus far, we focused on UV irradiation as our prime method of
disinfection. During an early prototype, image shown below,
we used clear plastic tubing to hold the water hoping that the
water would be exposed to maximum UV light and would be
disinfected efficiently. We also used Aluminum foil around the
inside of the cylinder to reflect the UV-C light. To make sure
the water was exposed to UV light long enough, we formed a
circular pattern using the tube going down a cylinder. From
the results after running test, we found that UV-C light can not
penetrate through most plastics and that Aluminum foil does
not reflect UV-C rays. We also found out the distance we
wanted our UV-C source to be from the water was 10 cm or
less. In addition, test showed optimal disinfection of the water
when the water was exposed to the UV-C source for
approximately 50 seconds. With that given information, we
designed a new prototype similar to the one below. The only
difference was using FEP tubing, which is UV-C transparent
instead of regular plastic tubing, and using Tyvek house wrap,
which reflects UV-C rays instead of Aluminum foil. In addition,
we scaled the porotype larger for exposure time concerns.
References
City of San Angelo Water Quality Management.
http://www.cosatx.us/departments-services/water-quality.
American Public Health Association, American Water Works
Association, and Water Pollution Control Federation, 2004,
Standard methods for the analysis of water and wastewater
(21st ed.): Washington, D.C. American Public Health
Association, Section 9223.
Acknowledgements
This project was supported by Angelo State University's
Undergraduate Research Center, Water Quality Plant
Manager, Tymn Combest, and Ryan Beltran at Elequatech in
San Antonio, TX.