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Use weeds in the river to treat water

Inspired by the royal project of King Bhumibol of Thailand, water hyacinth can increase oxygen in water by 51%

Photo of Rachel Chang

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According to the BioScience journal, The roots of water hyacinth naturally absorb pollutants, including lead, mercury, and strontium-90, as well as some organic compounds believed to be carcinogenic, in concentrations 10,000 times that in the surrounding water. Water hyacinth is found to remove 60-80% of nitrogen and 69% of potassium from the water.

In 1985, the royal project initiated by King Bhumibol of Thailand initiated the use of water hyacinth for water treatment along with the oxidization pond. An oxidation pond is a pond that contains partially treated wastewater which is then left to allow the growth of algae and bacteria which decompose the waste.

According to Principle of Microbiology by Mosby, within an oxidation pond, heterotrophic bacteria (bacteria that use organic carbon as food) degrade organic matter in the sewage which results in production of cellular material and minerals. The production of these supports the growth of algae in the oxidation pond. Growth of algal populations allows further decomposition of the organic matter by producing oxygen. The production of this oxygen replenishes the oxygen used by the heterotrophic bacteria.  The oxidation pond should be about 0.5-2 meters in dept and filled with the water hyacinth in the middle of the pond to treat water. The daily water treatment amount is 30,000-100,000 cubic meters.

During the day time, algae in the oxidation pond will go through the process of photosynthesis which created oxygen. Then, bacteria  will use oxygen to decompose waste in the water. This process will keep going until the water is cleaned. What to bear in mind is that there must not be too much of the water hyacinth in the water because it would block the sunlight which stops the process of photosynthesis. Therefore, it is important to control the overpopulated water hyacinth by removing it every 10 weeks. In the study done by the Thai king, the BOD in the water increased by 19-85% or 51% on average. 


How would you describe the stage of development of your idea?

  • Conceptual Development

How big or scalable is the potential of your idea?

This project has a very big potential for scalability because we are using what India already abundantly has. Water hyacinth is everywhere in the water in India and even considered pests and invasive, blocking the transportation in the water. Each village in India can even create their own oxidation pond and grow their own water hyacinth.

Explain the sustainability aspect of your idea

The cost to implement is very low due to the fact that water hyacinth is everywhere in the water in India. However, there needs to be investment in the machine dig the oxidation pond and the machine to remove the water hyacinth in order to prevent the water hyacinth from overpopulating.

What types of financing would be required for your idea to be successful?

I believe the idea can be self-funded by the local government in India. There is no huge investment in the technology or patent only for the machine to remove overpopulated water hyacinth. Also, water hyacinth can be used in numerous ways to recoup the initial investment. The following use has been applicable to the use of water hyacinth.
1. As biomass (fuel), according to Productivity and nutrient uptake of water hyacinth Eichhornia crassipes. by K.R. Reddy and J.C. Tucker. Bengali farmers collect and pile up these plants to dry at the onset of the cold season; they then use the dry water hyacinths as fuel. They then use the ashes as fertilizer. In India, a ton of dried water hyacinth yield circa 50 liters ethanol and 200 kg residual fiber (7,700 Btu). Bacterial fermentation of one ton yields 26,500 cu ft gas (600 Btu) with 51.6% methane, 25.4% hydrogen, 22.1% CO2, and 1.2% oxygen. Gasification of one ton dry matter by air and steam at high temperatures (800°) gives circa 40,000 ft3 (circa 1,100 m3) natural gas (143 Btu/cu ft) containing 16.6% hydrogen, 4.8% methane, 21.7% CO, 4.1% CO2, and 52.8% N.
2. Water hyacinth can be used to feed animals. Dried water hyacinth is rich in protein and fiber and low in fat. The composition consists of 14-20% of protein, 1-2.5% of fat, and 17-19% of fiber.
3. Fertilizer can be made from water hyacinth because the plant itself contains a lot of nitrogen, phosphorus, and potassium which are important nutrients for crops to grow.

In-country experience

  • Not yet

Is your organization currently legally registered in India?

  • No

Tell us a bit about yourself.

My name is Rachel. I am a second year MBA student at Cornell. I was born and raised in Thailand where I learned the importance of agriculture and water management. While growing up, I heard a lot about the royal project initiated by the king of Thailand to help solve the waste water problem in Thailand using the low-cost, natural method. Water is such a huge problem in Thailand because we are an agriculture-based country. I hope that my idea can be applied to the situation in India just like how it was applied to the situation in Thailand before.

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Would the land for these ponds have to be bought as well as renting the equipment? In my opinion, I think more of an incentive will be have to be present for the idea to really take off. The cost of the plant may be inexpensive, but the investment for the land, ponds, management, and the system to get the water in the pond may cost a lot (of course I have no numbers, and I could be wrong about this). If this could be implemented slowly in small communities, with funding provided by private donors, then data that could create a model would be gathered. This would give investors/government more details about a wide/long-term use of these ponds. This could also help establish a system for efficient harvesting of biofuel, food for animals, and fertilizer. Once there is a model that can be presented (a model that has been based in India), then I think this idea will have an easier time taking off. Anyway, this is my thought on this, but this is a neat idea on how to treat water! Best of luck with your idea. 

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