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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.


Join the conversation:

Photo of James

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. 

Photo of DFAatGT

What if we can add nutrition to the water from the weed or a supplemental plant that can coexist with the plant. The plant although have been used before are there any other plants that can also be used and replace the plant. Can the weeds survive in India? What are some the economic incentives to grow the seed? Can members of the community have jobs created from using the and growing the plants. Can the weed be used for other purposes such as consumption? This is from Design For America and OpenIDEO of Georgia Institute of Technology. 

Photo of Daniel Schuster

This sounds like a really great concept, Rachel. Are there any fishing communities in India that would benefit from the introduction of water hyacinth?

Photo of Rachel Chang

Fishing communities? Of course, they will benefit from having a clean supply of water too. According to the CMFRI Census 2010, there are 3,288 marine fishing villages and 1,511 marine fish landing centers in 9 maritime states and 2 union territories. The total marine fisherman population was about 4 million comprising in 864,550 families. According to the CMFRI Census 2010, there are 3,288 marine fishing villages and 1,511 marine fish landing centres in 9 maritime states and 2 union territories. The total marine fisherfolk population was about 4 million comprising in 864,550 families.

Other than for water treatment, according to Gaia Discovery, water hyacinth is also a good feed for fish. For instance, the Chinese grass carp is a fast growing fish which eats aquatic plants. It grows at a tremendous rate and reaches sizes of up to 32 kilograms. It is an edible fish with a tasty white meat. It will eat submerged or floating plants and also bank grasses. The fish can be used for weed control and will eat up to 18-40 percent of its own body weight in a single day.

Other fish such as the tilapia, silver carp, and silver dollar fish are all aquatic and can be used to control aquatic weeds. Water hyacinth has also been used indirectly to feed fish. Dehydrated water hyacinth has been added to the diet of channel catfish fingerlings to increase their growth. It has also been noted that decay of water hyacinth after chemical control releases nutrients which promote the growth of phytoplankton with subsequent increases in fish yield. 

Photo of Daniel Schuster

Hi Rachel,
That's really interesting - thanks for sharing details on the fisherfolk population and the fish that can consume water hyacinth.

Are there any estimates of how much damage dead zones are costing the 4 million fisherfolk?

For example, in the Gulf Coast region of the US, it is estimated that the dead zone is costing the seafood industry $38 million a year, according to the National Oceanic and Atmospheric Administration. (Whitworth, Joe S. (2015-09-08). Quantified: Redefining Conservation for the Next Economy (Kindle Locations 2845-2846). Island Press. Kindle Edition. )

Is it possible that the fisherfolk or downstream purchasers could help fund the purchase of the equipment that digs the oxidation ponds and benefit from improved yields?

Photo of Robert Guertin

Hey, awesome post regarding the use of existing amenities to help! As I'm not too familiar with bio-science, would these hyacinth weeds be strong enough to filter grey water for drinking, or would any further filtration be needed? 

Photo of Rachel Chang

I would suggest boiling water from the oxidation pond before consumption or using it to brush your teeth. Boiling water for 1 minute kills Cryptosporidium, Giardia, viruses, and bacteria. However treating water in the oxidation before boiling is necessary because boiling will not get rid of sediment, odor, or heavy metals from the water. 
However, treated water from oxidation pond is safe for household use such as bathing or laundry.

Photo of Shane Zhao

Fascinating post Rachel! In addition to being a natural purifier, you'll be curious to know that water hyacinth is also a great source of clean energy. Here's an article on how water hyacinth's potential is beginning to be explored in India: 

Photo of Rachel Chang

That's awesome! I'm so glad water hyacinth can be used for so many things. In Thailand, we also make baskets and furniture out of water hyacinth and I heard that in Taiwan people cook with it. It's amazing how we can turn such weeds into something useful for society!

Photo of Tracy Brandenburg

Great job, Rachel!   Very cool to learn about this solution that comes right from nature and even has multiple uses beyond water treatment.