Water Purification using Ozone

When choosing their science project, Emma Grotto and Sophie Kirkman could not decide whether to do ozone water purification or making biodiesel from used vegetable oil. They researched both topics and eventually chose the water purification project because it seemed more relevant and necessary in Africa.

 How it worked

1. A series of transformers stepped up the voltage to about 20 000V.

2. They cut a glass tube from a fluorescent light to 20cm long, and lined it with Aluminium net.

3. They put an aluminium rod in the middle, lined it with aluminium net, and held it in place with silicone rubber.

4. They attached one wire of the circuit to the outer coil, one to the aluminium rod.

As a result of the high voltage, electrons are stripped out of the oxygen molecules in the air between the gap resulting in a purple discharge, and the formation of ozone gas.

A small fish tank pump was used to pump air through the sealed tube, and the ozone rich air leaves the other side of the glass tube through a silicon pipe and is bubbled through the water to purify it. Ozone is a highly oxidising gas which will deactivate viruses, kill bacteria, destroy organic matter and precipitate inorganic compounds hence purifying the water.

Aquaponics

Abigail and Eden Putterill were inspired to do this topic when they visited their uncle who used a similar set up.

Benefits of aquaponics

-Two products are produced by the system: fish and food from the plants.

-There is no soil borne diseases.

-There is no extra labour required to till.

-The plants remain hydrated and will not have the problem of wilting.

-The system uses 60-70% less energy than agriculture.

-The plants are healthier and there are increased growth rates

-Lettuce can be grown in 3 weeks instead of 3 months.

-This system does not depend on seasons.

-It is very cost efficient once it is set up because a large profit can be earned.

Fish in an aquarium produce waste. This waste (containing ammonia) can be used to grow vegetables efficiently. The water from the aquarium is pumped by a water pump through a pipe into a gravel grow bed which the plants grow in. The fish efficient ammonia filters through granite chips in the grow bed. Bacteria convert ammonia to nitrites and then to nitrates. This is the basic form of plant protein. It is absorbed by the plants and the water flows back into the aquarium.

Ammonia is toxic to fish, but after it has been through the natural filtration system in the grow bed the ammonia is removed by the plants. This water is clean and can be recycled. This is a self-sustaining system.

The Impact on Africa

Aquaponics does not depend on location so it is used in urban and rural areas. People in Kenya have benefited from using aquaponics to gain a greater income by setting up a system similar to this one. They grow plants in their spare time and can sell the fish and food produced. It is also a cheaper and healthier diet so anyone that uses this system can benefit from it. Poor children in less economically developed countries can go to school because they will not have to search for food. Aquaponics does not depend on soil quality so it can be used anywhere in Africa.

Pig Manure as an Energy Source

Amanda Kane, Brittany King and Avina Trivedi chose 'Generating Electricity from Pig Manure' as their topic for the science fair because they were intrigued by the way in which it works and believe it to be capable of becoming a main source of renewable energy if implemented on a larger scale. Upon visiting a farm in Zimbabwe which has implemented this method of producing energy, they realised that this method is self-sustainable, eco-friendly, effective and once implemented, does not cost much.

With future power shortages and many rural areas existing without access to power, this method should prove to be a reliable source of electricity for many. They were pleased to have been placed third in the science fair and hope that in the future this method is implemented.

A summary of the model on which they based their project is illustrated in the picture above.

They particularly liked this method because it is:

ü  -Eco-friendly as the digestive fluid produced in the separation and fermentation processes can be sprayed as liquid fertilizer. It is also converted into solid fertilizer and can then be sold and therefore this method produces a minimal amount of waste.

ü  -Self-sufficient as the waste heat from the engines of the generator can often be used to run the digester.

The science fair this year, themed 'Celebrating science in Africa', was a huge success. It is always interesting to see all the different ideas coming from all the different students. Students from across Harare gathered together to show the different things that they believe has the potential to influence Africa or has already influenced the continent. The judges had a hard time deciding the final winners because there were so many brilliant ideas. These ranged from aquaponics to different water purification systems and even worm farming! The students put in hours of work towards making a physical experiment to display. 

The judges final decision were:

·         1st- water purification using ozone

·         2nd- aquaponics

·         3rd- pig manure as an energy source.

Well done to these groups for the great presentations.