#2 DT Water Based experiments

Design Thinking Laboratory: Water Usage

Experimental Handouts for Undergraduate Civil Engineering Students

Experiments

Course Overview Experiment 1 – Smart Tap Experiment 2 – Greywater Reuse Experiment 3 – Rainwater Harvesting Student Report Guide

Course Overview

Theme: Applying Design Thinking to real-world water conservation problems.

These experiments combine Civil Engineering measurements with user-centred problem solving. Students are expected not only to obtain numerical results, but also to understand the user problem, develop alternatives, build a prototype and test the proposed solution.

1. Empathize

2. Define

3. Ideate

4. Prototype

5. Test

Target groupUndergraduate Civil Engineering students

ModeSmall teams of 3–5 students

AssessmentMeasurements + prototype + reflection

Core skillEvidence-based water conservation

General Instructions

1. Work in teams and assign roles such as team leader, measurement lead, user-observation lead, prototype lead and recorder.
2. Record all raw measurements with units. Do not replace measured data with assumed values.
3. Repeat measurements where practical and report the average.
4. Identify assumptions clearly.
5. Compare the prototype against a baseline condition.
6. Discuss technical performance, cost, user acceptance and environmental impact.
7. Follow laboratory safety instructions and use only approved, non-hazardous water sources.

Experiment 1 – Smart Water-Saving Tap/Fixture

AreaWater supply & plumbing

Duration2–3 hours

Team3–5 students

Main outputWater-saving fixture prototype

1. Title

Design and Testing of a Low-Cost Water-Saving Tap Intervention

2. Objective

To measure water consumption from a conventional tap, identify user-related wastage, develop a low-cost intervention and experimentally determine the reduction in water use.

3. Design Challenge

How might we reduce water consumption during hand washing without significantly reducing user convenience?

4. Learning Outcomes

• Measure tap flow rate and water consumption.
• Identify water-wasting behaviour and system-level causes.
• Generate and compare alternative design ideas.
• Construct a simple prototype.
• Evaluate percentage water savings and user acceptance.

5. Apparatus / Materials

• Existing tap or laboratory water outlet
• Measuring bucket or graduated container
• Stopwatch
• Measuring cylinder
• Flexible hose, connectors and suitable low-cost prototype components
• Optional: tap aerator/flow restrictor or push-button mechanism
• Notebook/data sheet

6. Design Thinking Procedure

Stage A – Empathize

1. Observe a typical hand-washing activity without interfering with the user.
2. Record when the tap is opened and closed.
3. Identify possible wastage points, such as leaving the tap running while applying soap.
4. Interview 2–3 users, if permitted, about convenience and acceptable water flow.

Stage B – Define

Write a one-sentence problem statement based on observations. Example: “Students leave the tap running during part of hand washing, resulting in unnecessary water use.”

Stage C – Ideate

Generate at least five solutions. Examples include:

• Flow restrictor
• Aerator
• Push-to-open tap
• Timed valve
• Sensor-operated tap

Rank the ideas using effectiveness, cost, ease of fabrication and user convenience.

Stage D – Prototype

1. Select one feasible solution.
2. Install or construct the prototype safely.
3. Check for leakage.
4. Operate the fixture several times before taking final measurements.

Stage E – Test

1. Measure the baseline flow rate of the original tap.
2. Repeat the measurement at least three times.
3. Install the prototype.
4. Repeat the same measurements using the same measurement method.
5. If possible, conduct a standardized hand-washing simulation.
6. Record user feedback on flow, convenience and acceptability.

7. Measurements

Trial	Baseline volume (L)	Baseline time (s)	Prototype volume (L)	Prototype time (s)
1
2
3

Flow rate: Q = V / t
where Q = flow rate (L/s), V = collected water volume (L), t = collection time (s).

Percentage saving: Water saving (%) = [(Baseline − Prototype) / Baseline] × 100

8. Questions for Students

1. What was the main source of water wastage?
2. Which design alternative did your team reject and why?
3. What percentage reduction was achieved?
4. Did reducing flow affect user satisfaction?
5. How could the prototype be improved for large-scale use?

Safety: Keep electrical components away from water. Ensure all temporary plumbing connections are secure and do not create trip or slip hazards.

Experiment 2 – Greywater Reuse for Landscape Irrigation

AreaEnvironmental Engineering

Duration3–4 hours + observation period

Team3–5 students

Main outputSmall-scale greywater treatment/reuse prototype

1. Title

Design and Evaluation of a Small-Scale Greywater Reuse System

2. Objective

To develop a simple treatment arrangement for suitable greywater and evaluate its potential for non-potable applications such as landscape irrigation.

3. Design Challenge

How might we safely recover and reuse water that would otherwise be discharged?

4. Learning Outcomes

• Understand the concept of greywater segregation and reuse.
• Design a simple treatment train.
• Measure basic water-quality indicators.
• Compare alternative treatment arrangements.
• Evaluate reuse potential and limitations.

5. Apparatus / Materials

• Approved simulated or non-hazardous greywater source
• Transparent bottles/columns or laboratory filter unit
• Gravel
• Washed sand
• Activated carbon
• Collection containers
• pH meter or pH strips
• Turbidity meter or turbidity tube
• TDS meter, if available
• Measuring cylinder

Important safety note: Do not use sewage, toilet wastewater, or unknown contaminated wastewater. For undergraduate laboratory work, use simulated greywater or a source specifically approved by the laboratory instructor. Treated water from this experiment must not be used for drinking.

6. Suggested Treatment Train

Greywater → Settling → Gravel → Sand → Activated Carbon → Storage → Non-potable reuse

7. Design Thinking Procedure

Stage A – Empathize

1. Identify water uses in a college building that do not require potable-quality water.
2. List possible sources of reusable greywater.
3. Interview users or facility staff, if permitted, about concerns regarding odour, hygiene, maintenance and acceptance.

Stage B – Define

Prepare a problem statement that identifies the user, water source, intended reuse and major constraint.

Stage C – Ideate

Design at least three treatment configurations. Consider treatment performance, footprint, material availability, maintenance and cost.

Stage D – Prototype

1. Prepare the filter media.
2. Arrange the media in the selected sequence.
3. Secure the column to prevent tipping.
4. Pass a small quantity of water through the system to stabilize the media.
5. Collect the treated water in a labelled container.

Stage E – Test

1. Collect a representative sample of the influent.
2. Measure pH, turbidity and TDS where instruments are available.
3. Run the greywater through the prototype.
4. Measure the same parameters in the treated water.
5. Record volume treated and approximate filtration time.
6. Discuss whether the resulting water is appropriate for the intended non-potable use based on your measured results and applicable institutional requirements.

8. Observation Table

Parameter	Raw greywater	Treated water	Change
pH
Turbidity
TDS (mg/L)
Volume (L)
Filtration time (min)

Removal efficiency (%) = [(C_in − C_out) / C_in] × 100

9. Questions for Students

1. Which treatment stage contributed most to the observed improvement?
2. What contaminants may remain even when turbidity decreases?
3. Why should greywater be kept separate from blackwater?
4. What maintenance would the prototype require?
5. Would users accept the proposed system? What evidence supports your answer?

Experiment 3 – Rainwater Harvesting Optimization

AreaWater Resources Engineering

Duration3–4 hours

Team3–5 students

Main outputOptimized rooftop harvesting model

1. Title

Design and Experimental Evaluation of a Small-Scale Rainwater Harvesting System

2. Objective

To design and test a model rainwater harvesting system and investigate how roof characteristics, rainfall intensity, first-flush arrangements and storage influence collection efficiency.

3. Design Challenge

How might we capture and store more rainwater from a building while keeping the system simple, affordable and maintainable?

4. Learning Outcomes

• Relate rainfall intensity to runoff generation.
• Measure collected runoff from a model roof.
• Calculate collection efficiency and runoff coefficient.
• Evaluate the effect of design modifications.
• Develop an evidence-based harvesting recommendation.

5. Apparatus / Materials

• Miniature roof model with interchangeable surfaces, if available
• Water sprinkler/rain simulator
• Measuring cylinder or graduated container
• Storage tank/container
• Gutter and downpipe
• Simple filter/mesh
• Stopwatch
• Measuring scale

6. Design Thinking Procedure

Stage A – Empathize

1. Identify the potential rainwater harvesting opportunities on a typical college building.
2. Identify user needs such as low maintenance, low cost, ease of cleaning and adequate storage.
3. List constraints such as roof area, rainfall variability and available storage space.

Stage B – Define

Write a specific problem statement. Example: “Design a compact harvesting arrangement that captures a high fraction of simulated rainfall while minimizing overflow and maintenance.”

Stage C – Ideate

Develop alternative arrangements by changing one or more of the following:

• Roof slope
• Roof surface
• Gutter arrangement
• Filter configuration
• First-flush volume
• Storage capacity

Stage D – Prototype

1. Measure the effective roof area of the model.
2. Install the selected gutter and downpipe.
3. Connect the outlet to a collection container.
4. Check all joints for leakage.
5. Calibrate the rainfall simulator if possible.

Stage E – Test

1. Apply a known quantity of simulated rainfall over a fixed period.
2. Measure the water reaching the collection point.
3. Repeat the experiment for different design configurations.
4. Keep rainfall intensity and test duration constant when comparing configurations.
5. Record overflow, leakage and first-flush losses.
6. Identify the configuration that provides the best overall performance.

7. Observation Table

Trial	Roof configuration	Rainfall input (L)	Collected water (L)	Overflow/loss (L)	Efficiency (%)
1
2
3
4

Collection efficiency (%) = (Collected water / Rainfall input) × 100

Runoff coefficient = Runoff volume / Rainfall volume over the same effective area

8. Questions for Students

1. Which configuration produced the highest collection efficiency?
2. What caused the major losses?
3. How did roof slope influence collection?
4. What is the role of first-flush diversion?
5. How would you scale your model results to an actual building?
6. What additional information would be needed to size a real storage tank?

Student Report Guide

Each team should submit a concise report containing the following sections:

1. Problem identification: What water-use problem did you investigate?
2. Empathy findings: What did users/observations reveal?
3. Problem statement: State the final “How might we…” question.
4. Ideation: Show at least three alternative concepts.
5. Concept selection: Explain the criteria used to select the final idea.
6. Prototype: Include a labelled sketch or photograph and describe construction.
7. Experimental method: Give enough detail for another student to reproduce the test.
8. Results: Present raw observations, calculations and graphs where appropriate.
9. Discussion: Explain what the results mean and identify limitations.
10. User evaluation: Discuss convenience, acceptance and practical usability.
11. Environmental/economic evaluation: Discuss water saving, materials, maintenance and approximate cost.
12. Conclusion: State whether the design challenge was successfully addressed.
13. Reflection: What would your team change if given another prototype cycle?

Suggested Assessment Rubric

Criterion	Marks
Empathy and problem definition	10
Ideation and engineering reasoning	15
Prototype quality	20
Experimental procedure and data quality	20
Analysis and calculations	15
User/environmental considerations	10
Report and reflection	10
Total	100

Instructor suggestion: Require students to test at least one failed or rejected idea and explain why it was not selected. This makes the Design Thinking process visible rather than turning the activity into a conventional laboratory experiment.

Design Thinking Laboratory • Water Usage • Undergraduate Civil Engineering