Annex A - Group Research Proposal

Research Proposal
SCHOOL OF SCIENCE AND TECHNOLOGY, SINGAPORE

INVESTIGATIVE SKILLS IN SCIENCE

Names:

Johanna Lim Ziyun (3)
Kok Li Ying (4) 
Chong Yong Liang (10)
Ng Wei Jie (24)

Class:

S2-09

Group Reference:

A


Type of research:

[  ] Test a hypothesis: Hypothesis-driven research

[  ] Measure a value: Experimental research (I)

[  ] Measure a function or relationship: Experimental research (II)

[  ] Construct a model: Theoretical sciences and applied mathematics
[  ] Observational and exploratory research

[X] Improve a product or process: Industrial and applied research

________________________________________________________________________

Title of project

Development of an automated aquaponics system (temperature sensor) 


Question or Problem Being Addressed/Engineering Problem

As the world population is increasing daily, (just in Singapore, it has hit up to a population of 6.9 million!), more space is used for residential areas, factories or even for recreation! (i.e. shopping malls etc). Agriculture and aquaculture take up a lot of space and its quality is dropping even more. Just like the oil palm cultivation in Malaysia, they have poor farming practices, such as monoculture where one single crop is planted over again and again. This reduces soil fertility and causes soil leaching and severe soil erosion.

Agriculture and aquaculture is thus becoming more expensive as the product requires heavy transport and preservation in order to deliver them into the urban areas where the consumers are. Agriculture has shaped society and without it, we would not have food to survive. Thus, this project aims to solve this problem on a smaller scale.


Engineering Goal

Development of an automated aquaponics system for the production of fish meat, as well as the production of mint. Mint has many uses and it could benefit the people, it includes reducing the symptoms related to digestion, clear sinuses, fight infection, act as an insect repellent, quick and effective remedy to nausea, clears up congestion of nose, throat or lungs and many more! Other than that, the automation of the system will give us the convenience as it will monitor the temperature and pH levels; in this way, we are able to change the following factors accordingly, saving time and benefitting the fishes’ growth.

Specify Requirements

  1. In modern world context (so that not only urban residents will be able to utilise it, but also the people living in the city etc)
  2. Space-saving
  3. Time-saving
  4. Effective, able to produce product in a short period of time (like around 3-6 weeks)
  5. Cost-saving (not that expensive)
Alternative Solutions

Aquaponics

Aquaponics is a sustainable food production system that consists of conventional aquaculture of breeding aquatic animals and hydroponics, which is a water-based method of cultivating plants. Effluents which are gases and slightly polluted water from the waste of the aquatic animals will accumulate in the water, and increase the toxicity level for the fish. As such, these by-products will be broken down by nitrogen-fixing bacteria, then filtered out by the hydroponics plants. Finally, the clean water will then be recirculated back to the fish and this cycle will repeat itself. (Rakocy, Bailey, Shultz & Thoman, 2013)

The advantage is that this system produces protein (fish) and vegetables in one system and it produces 4 to 10 times more vegetables than the conventional urban agriculture. Other than that, it is uses up to 90% less than conventional agriculture and furthermore, as water is constantly being recirculated back to the fish, water usage is minimal and reuse of water is highly efficient. They are also naturally organic, with no chemicals. (Jed Davis, Lucas Davis, David Buckley & Ruth, 2014) 

Unfortunately, a major disadvantage would be that it is usually expensive to set up, inclusive of the cost wirings, housing, tank plumbing and budget for the fish and plants. Tubes and water supply needs constant monitoring to see if they are still functioning properly. (Leah Moore, 2012) 

Water pH level will also have to be monitored closely, as one faulty component can cause the whole system to break down easily. It is also not advised to grow root crops. Leafy vegetables are advised instead. The water needs to be free of toxins such as ammonia and nitrates and have sufficient oxygen levels for aquatic organisms to survive. (McCarthy, 2013).

Hydroponics

Hydroponics is a method of crop cultivation which uses the method of soilless growth of plants. The nutrients that are normally found in soil are dissolved into water, creating nutrient solutions.  Roots are usually submerged or suspended to be able to absorb the nutrients found in the solution. Since arable land is on the decline, hydroponics is seen as a solution where plants can be cultivated using water which is abundant, hence it is versatile. (Turner, 2008)

Hydroponics has several advantages. It has almost no pollution as most of the nutrients are all absorbed by the plants. Soil is not required for hydroponics and there is no need for huge farming as it allows the crops to be produced in greenhouses, even in the desert sands. It is a stable technology for growth of plants and ensures high yields. Other than that, desired nutrient environment can be easily provided for plant growth and since water stays in the system, reusing of water is efficient. Lastly, there is no chemicals involved! (Sharmila Saheed, 2013)

However, everything has its advantages and disadvantages. It has a high set-up cost as it requires meticulous planning when designing and constructing. (Hydroponics Center, 2011) Hydroponic conditions, especially the presence of high humidity, would create a hot bed for salmonella growth. (Department of Agriculture, Forestry and Fisheries, 2011) Salmonella can then be transmitted through human consumption and cause food poisoning. Since hydroponics are soilless, diseases are able to spread quicker as they are not contained. (Black, 2009) 

Aeroponics

Aeroponics is a method where plants are grown in a humid environment without the use of any growing medium, making it suitable for indoor gardening or greenhouses. (True Aeroponics™, 2013) It stimulates rapid plant growth as the plants will rapidly develop root systems. (D’Gardener, 2008)

The plants are suspended in a growing chamber. A pulsed sprayer will release a fine, high pressure mist which consists a mixture of water, nutrients and growth hormones into the enclosed environment of the growing chamber at a time interval and duration for the plants. (True Aeroponics™, 2013)

Aeroponics, when compared to the traditional method allow plants to grow faster, as the roots are exposed to more oxygen, and thus obtain higher yields from the plants. It has been proven that it can aid growers to optimize rooting on most plants. Aeroponics is beneficial to the environment in a sense that the water used in aeroponics can be reused. The water loss of an aeroponics system is cut by 99% when compared to the traditional farming methods. When compared to hydroponics, aeroponics offers more control over the root system as the roots aren’t immersed in any liquid. (True Aeroponics™, 2013)

If needed, the aeroponics system can be moved around easily. A main drawback of the aeroponics system is that the root chamber, the one containing the dangling roots, attract lots of bacterial growth due to its semi-moist environment, so it has to be cleaned regularly. The entire system depends on the pumps, sprinklers and timers, so if any one of these break down and are not fixed in time, the plants can wither and maybe even die. One must also be proficient in knowledge about plants, such as nutrition amount as there would be no soil to soak up excess nutrition (D’Gardener, 2008). All these may make the system a meticulous one that requires time and effort.

Best Solution
Our best solution would basically be aquaponics. We plan to develop an aquaponics system but also incorporate the automation of the system such that the temperature, pH level, calcium levels etc. This would be automated via the use of Arduinos so that we would be able to tell the pH levels etc more conveniently (via lighted bulbs etc) 

Other than that, aquaponics has the most advantages from the rest and it has the highest yield among all. It is also able to produce fish and plants in one system and the reuse of water is high but efficient too. 

Lastly, we honestly believe that with the automation of the system, it will not only save us precious time measuring the variables; but also helps us to ensure the healthy growth of the fishes and plants, as well as the success of the system. 

Information About Plant (Peppermint)

Peppermint is a hybrid between Mentha aquatica (water mint) and Mentha spicata (spearmint) and is a member of the Lamiaceae (Mint family). Mentha comes from the Greek Mintha, meaning mint and piperita comes from the Latin piper, meaning pepper. Peppermint grows in the wild throughout Europe, North America, and Australia and has a long history of being widely cultivated in northern and southern temperate regions along stream banks and in other moist areas. Evidence shows and some believe that peppermint was cultivated in ancient Egypt, although its first definite cultivation was near London in 1750. In the late 1600's and early 1700's it was first recognized as a distinct species by John Ray, a botanist. Peppermint is cultivated in two main varieties, black mint, which has violet-colored leaves and stems, and white mint, which has pure green leaves. (Dustin Bond, 2000)

Peppermint plants are characterized by the small purplish or lilac-pink blossoms, or flowers, which grow in circles around the stem, forming dense many-flowered spikes or heads. These flowers can be seen July through September. Peppermint, a perennial with its erect and branching smooth, square, hairy stem can grow between one and three feet tall. The plant has a long running root system which supports the stem and numerous toothed leaves. The leaves, which are normally dark green, can sometimes be purple tinged; the stem is usually purplish. The many green or purple-tinged, pointed, toothed leaves are between one and two inches long, and are about half as wide as they are long. The presences of volatile essential oils in the leaves and other parts of the plant, gives the plant a very appealing scent, and fills the surrounding air with a pleasant aroma of mint. (Dustin Bond, 2000)

The peppermint plant and its many parts are used throughout the world in many different ways and for many different purposes. The production of peppermint oil by distillation of the cultivated herb is an extensive industry in the United States and around the world. Cultivation of the plant is required because the plants found in the wild are not suitable for the distillation process and the cultivated plant contains much more and better quality oil. The United States is the leading producer of peppermint oil in the world, with Michigan, California, Washington, Oregon, Idaho, Indiana, and Wisconsin leading the way. (Dustin Bond, 2000)

Figures and Information for Reference

Figure A - Peppermint’s nutritional information (United States Department of Agriculture, 2013)

Diagram of tank 

Methodology
Equipment List

Sensors
  • Ammonia sensor x1
  • Nitrate sensor x1
  • Dissolved Oxygen sensor x1
  • pH sensor x1
  • Salinity levels x1
  • Temperature sensor x1
  • Chloride sensor x1
  • Calcium chloride sensor (hardness of water) x1
  • Data loggers x3


Breeding system
  • Food timer x1
  • Gourami fish food x1
  • Fish tank x1 (0.5m x 0.35m x 0.8m)
  • Water pump x1
  • Air pump x1
  • Air tubes
  • Bacteria life solution x1
  • Gourami x7

Hydroponics
  • Hydroponics tray x1 
  • Board x1
  • Net pots x8
  • Peppermint seedlings x9
Filter system
  • 1.25 litre plastic bottle x1
  • Small pebbles
  • Filtering medium x1
  • Bio-filtration
Automation
  • Arduino Leonardo x1
  • Relay system x1
  • Chiller x1
  • Light bulbs (red- 6 and below, green- 7 (neutral),  blue- 8 and above x3
  • Battery x2
  • Wires x8
Equipment for safety precautions
  • Safety goggles (pairs) x4
  • Woollen gloves (pairs) x4
  • Bin for disposal of sharp objects x1
  • Lab coats x4

Procedures

Fish tank
  1. Pour tap water into the fish tank and fill in 3/4 full.
  2. Submerge the water pump into the fish tank.
  3. Connect the water pump with the connectors using a water hose.
  4. Connect the connectors to the 1.25 litre bottle using a water hose.
  5. Switch on the water pump.
  6. Connect the oxygen pump to the fish tank using air pipes.
  7. Switch on the oxygen pump and turn the air pressure to high.

Hydroponics 
  1. Measure the diameter of each net pot (7.5cm), and cut 10 holes from the foam board accordingly.
  2. Put the 9 net pots into the holes that were cut out in the foam board and leave one empty.
  3. Place the foam board with the pots on top of a container.
  4. Drill a hole at a height of 7cm from the bottom of the container. (overflow method)
  5. Pour water into the container until it is 3/4 full.
  6. Tape a piece of string below the hole to guide the water into the fish tank.
  7. Wash away the soil from the peppermint seedlings’ roots.
  8. Put the peppermint into the net pots.
  9. Fill up the net pots that have the peppermint with Leca beads to support it. 
Breeding system
  1. Put 7 gourami into the fish tank.
  2. Feed the gourami with the fish food. (feeding times to be advised)
Filter system
  1. Cut the bottom of a 1.25 litre bottle.
  2. Turn the bottle upside down.
  3. Poke two holes through the cap and cap the bottle.
  4. Pour the bacteria cultivating balls into the bottle.
  5. Pour pebbles on top of the bacteria cultivating balls.
  6. Place a filter medium on top of the pebbles.
  7. Poke a hole at the height of 14 cm from the bottom of the cap. (overflow method)
  8. Place the filter bottle above the empty hole in the foam board.
  9. Connect a water hose to the hole for the water to flow out into the tank.

Sensor system
  1. Place the chloride sensor into 1/2 of the depth of water to check the chlorine level. 
  2. Turn on a data logger.
  3. Connect the chloride sensor to the data logger and observe the chlorine levels of the tap water in the fish tank over a few days. Fishes cannot survive in waters of high chlorine levels, therefore the water should have a chlorine level as low as possible before we put in the fishes.
  4. Put the nitrate and ammonia sensors into 1/2 of the depth of water in the fish tank.
  5. Connect the sensors to the data logger.
  6. We will not feed the fish for two days and observe for any changes in the ammonia level and nitrate level. 
Instructions for usage of sensors

For Ammonia, Nitrate, Calcium chloride, pH sensors
  1. Recalibrate the sensors. 
  2. Insert the tip of the sensor into the water.
  3. Connect the sensors to the data loggers for data collection. 
For Temperature Probe (does not require calibration)
  1. Insert the tip of the sensor into the water. 
For Dissolved Oxygen Sensor: 
  1. Remove the membrane cap from the tip of the probe. 
  2. Using the pipet, pour 1 ml of the DO Electrode Filling Solution into the membrane cap. 
  3. Carefully screw the cap back into the electrode. 
  4. It is necessary to warm up the probe for 10 minutes before taking readings. To warm up the probe, leave it in the water and connect it to the data logger, and leave it running for 10 minutes.
Instructions for calibration of sensors
*Temperature Probe and Salinity probe does not require any calibration. 

For Calcium sensors:
1. Wash the tip of the sensor thoroughly with tap water/deionised water.
2. Dry the sensor with a paper towel.
3. Connect the sensor to the data logger.
4. Switch to the calibration mode.  
5. Dip the sensor into the 1000 mg/L chloride/calcium solution.
6. Make sure that the ISE is not resting on the bottom of the container containing the solution.
7. Wait for 30 secs for the live voltage to stabilise.
8. Take out the sensor.
9. Wash the tip of the sensor with tap water/deionised water.
10. Wipe it dry with a paper towel. 
11. Enter the calibration route on the data logger. 
12. Dip the tip of the sensor into the 10 mg/L chloride/calcium solution.
13. Make sure that the ISE is not resting on the bottom of the container containing the solution.
14. Wait for 30 secs for the voltage to stabilise. 
15. Take out the sensor.
16. Wash the tip of the sensor with tap water/deionised water.
17. Wipe it dry with a paper towel. 

For Ammonium and Nitrate sensors:
1. Wash the tip of the sensor thoroughly with tap water/deionised water.
2. Dry the sensor with a paper towel.
3. Connect the sensor to the data logger.
4. Enter the calibration route on the data logger.  
5. Dip the sensor into the 100 mg/L ammonium/nitrate solution.
6. Make sure that the ISE is not resting on the bottom of the container containing the solution.
7. Wait for 30 secs for the live voltage to stabilise.
8. Take out the sensor.
9. Wash the tip of the sensor with tap water/deionised water.
10. Wipe it dry with a paper towel. 
11. Switch it to the calibration mode again. 
12. Dip the tip of the sensor into the 1 mg/L ammonium/nitrate solution.
13. Make sure that the ISE is not resting on the bottom of the container containing the solution.
14. Wait for 30 secs for the voltage to stabilise. 
15. Take out the sensor.
16. Wash the tip of the sensor with tap water/deionised water.
17. Wipe it dry with a paper towel.           
    
For pH sensor:
1. Wash the tip of the sensor thoroughly with tap water/deionised water.
2. Dry the sensor with a paper towel.
3. Connect the sensor to the data logger.
4. Enter the calibration route on the data logger.  
5. Dip the sensor into the pH 4 solution.
6. Make sure that the ISE is not resting on the bottom of the container containing the solution.
7. Wait for 30 secs for the live voltage to stabilise.
8. Take out the sensor.
9. Wash the tip of the sensor with tap water/deionised water.
10. Wipe it dry with a paper towel. 
11. Switch it to the calibration mode again. 
12. Dip the tip of the sensor into the pH 7 solution
13. Make sure that the ISE is not resting on the bottom of the container containing the solution.
14. Wait for 30 secs for the voltage to stabilise. 
15. Take out the sensor.
16. Wash the tip of the sensor with tap water/deionised water.
17. Wipe it dry with a paper towel. 

Arduino automation
1.  Launch the ‘Arduino’ application (you can search spotlight)
2.  Use the Arduino Leonardo and connect it to your Macbook
3.  Once you have connected, you would be able to program the Arduino Leonardo (using the codes etc)
4. You then connect the system such that it will create a circuit between the battery, relay system and chiller.
5. From the battery, connect 3 wires. 
6. At the end of each wire, connect one bulb. (red, blue and green)
7. Once you have set up the system, you need to put the pH sensors and temperature sensors halfway through the waters. 
8. Connect the sensors to the Arduino too! 
9. As you can see it is all linked together; the temperature sensor will activate the relay system and in turn, the relay system will activate the chiller; which would be able to turn the temperature down. 
10. For the pH sensor, it will be connected to the Arduino which will be connected with the battery and the battery is connected the the 3 bulbs so if it is neutral (7), green bulb will blink, if it has a pH level of more than 8, it will blink blue and if it has a pH level of less than 7 then it will turn red.
11. This way, we would be able to change the necessary variables accordingly. 

Approximate Calibration Voltages 
  1. Ammonia sensor has a 2.1 voltage for high solution (100 mg/L) and 1.3 voltage for the low solution (1 mg/L)
  2. Calcium sensor has a voltage of 1.9 voltage for high solution (1000 mg/L) and 1.5 voltage for low solution (10 mg/L) 
  3. Chloride sensor has a voltage of 2.0 for high solution (1000 mg/L) and 2.8 voltage for low solution (10 mg/L)
  4. Nitrate sensor has a voltage of 1.6 for high solution (100 mg/L) and 2.4 voltage for low solution (1 mg/L)

Risk Assessment

List/identify the hazardous chemicals, activities, or devices that will be used.
We will be using the Arduino Leonardo device that will be connected to our Macbooks and then that will be connected to the aquaponics system that connects the relay, chiller and the bulbs together. In the process, we might experience a short-circuit, resulting in us getting electrocuted. 

Other that that, we would be using the temperature sensors, calcium sensors, ammonium nitrate sensors etc. Through this process, we need to work with chemicals (calcium solution, ammonia nitrate solution- high and low), thus, we might get burnt or harmed.

Lastly, the last hazard would be the glass tank as it is fragile and brittle, thus it can break anytime. As we will be using the tank regularly, if it happens to break at our hands, we will get scarred and possibly cut ourselves (hands etc)

Identify and assess the risks involved. (tables below is a referencing guide on how to classify the risks)

Source: (Workplace Safety Health Council, 2012)
 Source: (Workplace Safety Health Council, 2012)

Source: (Workplace Safety Health Council, 2012)


Risk #1: Short circuit can cause electrocution.

Risk #2: The glass tank could break and cause injuries.

Risk #3: If the tank is too heavy it could cause the support to break and destroy the system.

Risk #4: If water spills it can cause people to slip .
Risk #5: Chemicals are used in the sensors and if spilled, it might cause serious consequences.

Risk #6: Error with the Arduino Leonardo could cause error in the systems and cause sparks and maybe fires. 

Risk #7: Usage of Macbook near bay could cause it to short circuit and due to it being so close to user, it can injure him/her.

pastedGraphic_3.png

Describe the safety precautions and procedures that will be used to reduce the risks.

Risk #1 : Make sure to use insulated tools and rubber gloves when working with the electrical systems.

Risk #2 :  Be cautious when working near the tank and maybe use a plastic tank instead. 

Risk #3: Use stronger or more supports in order to support the weight.

Risk #4: Make sure to clean up water when it spills or wear sandals to avoid slipping.  

Risk #5: Exercise caution when using the sensors and wear a labcoat and gloves in order to avoid getting the solutions/chemicals into your hands.

Risk #6: Program the Arduino Leonardo and connect the relay system and chiller with it so as to avoid fires that may outbreak. 

Risk #7: Place your Macbook further away from the bay to prevent electrocution.

Describe the disposal procedures that will be used (when applicable).
- Chemicals
1. While handling with chemicals, put on safety goggles and gloves to prevent getting the chemical into contact with your bare skin or eyes.
2. After using the chemicals, dispose the chemicals into the sink and wash your hands. 3. If any spillage occurs, do inform the teacher immediately. If the spillage is minor, clean the area up immediately.

- Dead gourami/plants
  1. Take a fishing net and fish out the deceased fish.
  2. Dispose of it by a few different ways:
    1. Flush it down the toilet.
    2. Seal it in a plastic bag and throw it into a garbage bin.
List the source(s) of safety information.

Hauter,  S. & Hauter, D. (n.d.) How to Dispose of Deceased Fish. Retrived 11 July, 2014, from http://saltaquarium.about.com/od/fisheuthanasia/a/aadeceasedfish.htm
Princeton University (2014) Chemical Spill Procedures. Retrived 10 July, 2014, from http://web.princeton.edu/sites/ehs/emergency/spills.htm
Sharpe, S. (n.d.) Are Aquariums Safe? - Aquarium Safety. Retrived 10 July, 2014, from http://freshaquarium.about.com/od/beginnerfaqs/a/aquariumsafety.htm
Wikihow (n.d.) How to prevent electrical shocks. Retrived 10 July, 2014, from http://www.wikihow.com/Prevent-Electrical-Shock


Data Analysis

Data Collection

  1. Using the sensors, we will record down the water parameters of the water in the fish 
tank. We will dip all the sensors into the water in the fish tank and then connect them to
the dataloggers. The dataloggers will be record down the data of different water
parameters over a period of time and then, we will export the data into the Logger Pro 3
application into our learning devices. After that, we will analyse the data and the graphs.
Over time, we will find that our ammonia level has decreased and our nitrate levels has
increased, which shows a sign of the experiment working well. 

pH sensors: 
powered by the battery and Arduino to light up the various bulbs (green, blue and red); as shown in
the diagram above, to indicate whether the pH level needs to be increased and decreased. Thereafter,
we will adjust the levels such that it is suitable for the fish to live in.

Temperature sensors: 
powered by Arduino which powers the relay and chiller. From the relay system, we will be able to
tell whether the temperature needs cooling or not (since fish lives in a cold environment). We would
then lower the temperature if necessary. (until these two sensors are stabilised, we will then use
Arduino to automate the rest of the sensors; Ammonium Nitrate etc)

2.
Measure the length of the fishes, height of the plants and number of leaves at the start
of the experiment. Every Monday, Wednesday and Friday, we will do the same
measurements and plot graphs using the data collected. Two separate graphs for fishes
and the plants. Graph 1, Y axis will be the length of fishes (cm) and X axis will be the
number of days. Graph 2, height of the plants (cm) and number of leaves, while X axis will
be the number of days. Looking at the growth and rates of the fishes and plants, and that
they survive, then we can determine if the experiment is working well. 

3. 
We also can use video clips to explain our system and to show how it works. (show 
how the automation of the system will be able to instil convenience and effectiveness at
the same time) We can also plot a graph to show the height of water level in the
hydroponics tray against the time, with Y axis for the height (cm) and X axis for the time
(minutes). 

Bibliography

Agricultural Research Service: United States Department of Agriculture (n.d.) Nutrient facts about Peppermint. Retrieved 9 July, 2014 from

Anderson, G (2003). Abalone: Introduction 

Black, K. (2009). The disadvantages of hydroponics. Retrieved  9 July, 2014 from http://www.gardenguides.com/75433-disadvantages-hydroponics.html

Bond, D, Radford University (2000). All about peppermint 

Davis, J, Davis, L, Buckley, D & Buckley, R (2014). The advantages of aquaponics Retrieved 8 July, 2014 from

Department of Agriculture, Forestry and Fisheries. (2011). Hydroponic vegetable production. Retrieved 9 July, 2014 from http://www.nda.agric.za/docs/Brochures/prodGuideHydroVeg.pdf

Garderner, D. (2008). The advantages and disadvantages of aeroponics 
Retrieved 8 July, 2014 from 

Haunter, S. & Haunter. D. (n.d.) How to Dispose of Deceased Fish. Retrived 11 July, 2014 from http://saltaquarium.about.com/od/fisheuthanasia/a/aadeceasedfish.htm

Hydroponics Center (2011). Disadvantages of hydroponics. Retrieved 8 July, 2014  from http://www.hydroponics-center.com/2011/01/disadvantages-of-hydroponics.html

McCarthy, M. (2013). The disadvantages of aquaponics. Retrieved 8 July, 2014 from https://sites.google.com/site/aquapanaponics/4-project-updates/advantagesanddisadvantagesofaquaponics

Moore, L. (2012). The disadvantages of Aquaponics. Retrieved 8 July, 2014 from

Princeton University (2014) Chemical Spill Procedures. Retrived 10 July, 2014, from http://web.princeton.edu/sites/ehs/emergency/spills.htm

Saheed, S. (2013) Advantages and disadvantages of hydroponics
Retrieved 8 July, 2014 from

Sharpe, S. (n.d.) Are Aquariums Safe? - Aquarium Safety. Retrived 10 July, 2014 from http://freshaquarium.about.com/od/beginnerfaqs/a/aquariumsafety.htm

True Aeroponics™. (2013). How aeroponics work - questions and answers about aeroponics. Retrieved 9 July, 2014 from http://www.aeroponics.com/aero17.HTM

Turner, B. (2008). How hydroponics works. Retrieved 8 July, 2014 from http://home.howstuffworks.com/lawn-garden/professional-landscaping/alternative-methods/hydroponics.htm

Wikihow (n.d.) How to prevent electrical shocks. Retrived 10 July, 2014 from http://www.wikihow.com/Prevent-Electrical-Shock


WSH Council., & Ministry of Manpower, Ministry of Manpower, (2011). Code of practice on workplace safety and health (wsh) risk management. Retrieved 9 July, 2014 from http://statutes.agc.gov.sg/aol/search/display/view.w3p;ident=424fe219-0674-4888-aa4f-62bef7cd9604;orderBy=numUp;page=0;query=DocId:cd9437b7-419b-40de-99a3-09f2e7b8c90a%20Depth:0%20Status:inforce;rec=0

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