Page 17 - Shaping A Sustainable Future

Figure 4: Washing and rinsing of dishes.

Detergent Residue Removal Efficiency could be used to determine if there was any residual
detergent left on the rinsed dishes. To achieve this,
1. Measure the conductivity of a 10-litre pail of clean we soaked the rinsed dishes in another 5-litre pail of
water. clean water. Refer to Figure 5 for the measurement of
detergent residue in the experiment.
2. Place the cleaned dishes into the 10-litre pail of
clean water for 10min.

3. Measure the conductivity of the 10-litre pail of
clean water again.

As we used less detergent in our experiment, we
hypothesized to rinse the dishes using less water. A test
to validate if we could rinse off the detergent from the
dishes thoroughly using only 5 litres of water, i.e. 50 %
less than what was used by the staff.
Figure 5: Measuring the conductivity of water
The conductivity of the solution was found to increase before and after rinsing.
proportionally with the amount of detergent used in
the solution. Hence, the conductivity of the rinse water

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