Wong Guok Loon Crescendo HELP International School
Complete by 20th March, Friday
Water contamination involves multiple contaminants, such as dissolved heavy metals and organic pollutants .
Conventional treatment methods often require many resources and complex infrastructure, which creates an obstacle in poorer communities.
I’m ___ (self introduce 1 by 1)
And we will be using a multi-layered treatment model to tackle this problem.
In our system, sedimentation is integrated as an initial step, where reduced flow velocity allows pollutant-bound particles to settle, lowering the contaminant load before biological treatment.
To enhance performance, we implement reverse flow by periodically switching the direction of water movement. This redistributes sediment, prevents buildup, minimizes clogging, and ensures more uniform contact between pollutants and treatment zones, improving overall efficiency.
*Animation can be included to illustrate the reverse flow process more clearly ( forcing water to flow from point B to point A instead of conventional direction of flowing from point A to point B by installing valves at both ends and control which end acts as inlets and outlets periodically )*
The first filtration stage uses a lignocellulose matrix composed of water lettuce, coconut coir and palm oil fibres. Coconut coir contains cellulose, hemicellulose, and lignin, which provides hydroxyl and carboxyl functional groups that adsorbs heavy metal ions.
Acid treatment protonates these groups and removes pre-bound metals, increasing the number of available active binding sites. Additionally, the fibrous structure of the coconut coir improves absorption from large surface area and enhances retention time, while palm oil fibres contribute macroporosity, imaintaining flow distribution and preventing compaction.
Water lettuce, a hydroponic plant, exhibits extensive root systems that facilitate Rhizofiltration, Phytoaccumulation and Nutrient uptake.
So, how do hydroponic plants sustain phytoremediation processes?
For a hydroponic absorption to occur, contaminants must exist as either free ions, hydroxide complexes or chelated forms. This is due to the cell walls of the roots themselves containing carboxyl, hydroxyl and phosphate groups that provide primary binding sites for the metal ions. In addition, these roots consist of ligands that wrap around metal ions to form stable, soluble complexes that could be absorbed into the plant system.
Within the plant system, hydroponic plants can self-create phytochelatins and metallothioneins, which are rich in cysteine that allows binding with toxic heavy metals. (slide 35) Additionally, substances such as citrate and malate can further assist in detoxifying metals within the plant.(slide 36)
Notes ( include in presentation, redact from speech)
Definitions for Rhizofiltration: where metals bind to root surfaces ; Phytoaccumulation, where contaminants are absorbed into biomass; Nutrient uptake, reducing nitrogen and phosphorus concentrations, preventing eutrophication
Examples of compounds/ions
free ions (Cd2+)
hydroxide complexes ( Cu(OH)+)
chelated forms ( Fe-EDTA)
Toxic metal (Hg)
Pre-bonded metal (K)
Mention that ligands act as a chelating agent.
Mention that phytochelatins (PCs) are heavy-metal binding peptides
Mention that metallothioneins (MTs) are cysteine-rich proteins produced by the hydroponic plants to manage heavy metal homeostasis
Citrate is an organic acid that can also act as a chelating agent
Malate is a substance that exists as a salt or ester derived from malic acid; also chelating agent
Step 3-4 : Biochar
Building on this, the next stage introduces a way to treat our water to ensure it is safe to drink. First, biochar is added for additional adsorption of residual chemicals and toxins. Biochar attaches to heavy metal and other visible organic residues, holding them from flowing to further steps.
The water is then passed through a slow sand filter which consists of sediments such as sand and gravel. The slow sand filter naturally forms a biological layer called ‘Schmutzdecke’, which is a layer that filters microorganisms. This natural biological layer removes excess pathogens, preventing waterborne diseases.
Step 5: UV Treatment (Guok Loon)
Finally, we will put the treated water in a transparent container, letting the sunlight pass through the water. This process is called solar disinfection, which uses the sterilizing characteristic of ultra-violet rays in the sunlight to ensure that any remaining microorganisms are inactivated and the water is sterile.
This will be a very innovative hack for all future generations!
