CANDIDATE NAME: BRIGHT N SIBANDA
CENTER NUMBER: 090100
CANDIDATE NUMBER: 5001
SCHOOL: CYRENE HIGH
LEARNING AREA: CHEMISTRY
PROJECT TITLE: Construction of a Low-Cost Water
Purification System Using Locally Available Materials
STAGE 1: Problem Identification
Statement of Intent
This project aims to design and construct a simple, low-cost
water purification system using locally available and
sustainable materials. The solution must be suitable for
rural communities in Zimbabwe where access to clean
drinking water is limited.
Description of the Problem
In many rural areas in Zimbabwe, access to clean water is a
significant challenge. People often depend on unprotected
water sources, which may be contaminated with
microorganisms, chemicals, and particulate matter. This
poses health risks, especially to children and the elderly.
The lack of affordable water purification methods
necessitates a sustainable, indigenous-knowledge-based,
chemistry-driven solution.
Design Specifications
The purification system must be made using locally
available materials (e.g., charcoal, sand, gravel,
moringa seeds).
The model should remove visible impurities, reduce
microbial contamination, and be reusable.
It must be safe, affordable, and easy to construct.
The system should include a demonstration model and
a simplified chemistry explanation.
Environmental friendliness and cultural relevance must
be considered.
STAGE 2: Investigation of Related Ideas
Idea 1: Boiling Water
Merits: Kills microorganisms effectively; simple.
Demerits: Energy intensive (wood, firewood, electricity),
does not remove sediments or chemical contaminants.
Idea 2: Chlorination
Merits: Effective against bacteria; easy to apply; low
cost.
Demerits: Unpleasant taste; may not remove turbidity or
chemical contaminants; misuse can be harmful.
Idea 3: Commercial Filters (e.g., ceramic, activated carbon)
Merits: Effective at removing particles and
microorganisms; long-lasting.
Demerits: Expensive and not readily available in rural
areas.
Idea 4: Indigenous Filtration with Sand and Charcoal
Merits: Materials are readily available; uses indigenous
knowledge; multi-layer filtration effective at removing
sediments and some bacteria.
Demerits: May not eliminate all pathogens; needs
maintenance; efficiency depends on construction
quality.
STAGE 3: Generation of Ideas
Idea A: Moringa Seed Coagulation and Sand Filter
Explanation: Moringa seeds contain natural coagulants
that help settle dirt. Followed by sand filtering to
remove fine particles.
Pros: Local knowledge; moringa trees are common.
Cons: Less effective on microbes unless used with
further disinfection.
Idea B: Charcoal-Sand-Gravel Filtration System
Explanation: A vertical filtration column layered with
gravel, coarse sand, fine sand, and activated charcoal
from burnt maize cobs or wood.
Pros: Good for sediment and odor removal; charcoal
adsorbs impurities.
Cons: Does not guarantee full disinfection without
further treatment.
Idea C: Solar Disinfection and Filtration Hybrid
Explanation: Water is filtered through a sand-charcoal
system, then exposed to solar UV in transparent
bottles.
Pros: Effective microbial kill via UV; no chemicals
needed.
Cons: Dependent on weather conditions.
Selected Idea: Idea B – Charcoal-Sand-Gravel Filtration
System.
STAGE 4: Development of the Selected Idea
Materials Required
2-litre plastic bottles
Gravel (local river or quarry)
Coarse and fine sand (washed)
Activated charcoal (made from burnt maize cobs or
hardwood)
Cloth/muslin
Knife/scissors
Bucket for unfiltered and clean water
Construction Steps
1. Cut the bottom off a plastic bottle and invert it to act as
a funnel.
2. Add a cloth layer at the mouth of the bottle to prevent
particle leakage.
3. Add layers from bottom to top:
o Fine sand
o Coarse sand
o Gravel
o Activated charcoal (topmost)
4. Pour water through the filter and collect in a clean
container.
5. Test clarity and basic quality using indicators (e.g.,
potassium permanganate solution, smell, clarity).
Chemical Explanation
Filtration: Physical process where particles are trapped
in sand layers.
Adsorption: Organic materials and odors adhere to the
surface of charcoal (a form of carbon).
Possible chemical improvement: Use of alum
(KAl(SO₄)₂·12H₂O) as a coagulant.
STAGE 5: Presentation of the Final Solution
Artefact: Water Purification Model
You will build a working model using a transparent bottle to
show:
Clear layering of filtering materials.
Demonstration of cloudy vs. clear water output.
Label each layer and explain its purpose.
Poster Design Content (for presentation)
Title: "Low-Cost Rural Water Purification System Using
Charcoal and Sand"
Sections:
o Problem Statement
o Diagram of the Model
o Materials Used (local sources)
o Filtering Process Explanation (with arrows)
o Scientific Principles (adsorption, filtration)
o Benefits (affordable, sustainable, eco-friendly)
o Test Results (before and after filtration clarity)
STAGE 6: Evaluation and Recommendations
Evaluation
Relevance to Intent: The final solution met the original
goals—it's low-cost, effective in improving water clarity,
uses local materials, and is easy to construct.
Successes: Water clarity improved; odors removed;
accessible materials used.
Challenges: Time taken to wash sand; limited testing
tools to confirm microbial safety; charcoal dust clouded
water if not washed well.
Cultural Consideration: Indigenous knowledge about
charcoal and filtration was incorporated.
Recommendations
Incorporate a final boiling step or solar disinfection for
microbe control.
Community education on model maintenance and
hygiene.
Encourage planting of moringa trees as a
supplementary water treatment aid.
Future development could include clay or ceramic
filters for microbial removal.
