Question 19N.3.SL.TZ0.a
| Date | November 2019 | Marks available | [Maximum mark: 3] | Reference code | 19N.3.SL.TZ0.a |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Compare and contrast | Question number | a | Adapted from | N/A |
Ensuring the delivery of water to homes requires a pressure to be maintained in the pipes. Biofilm formation will reduce the pressure in the pipes. Three experimental water piping systems were set up and the water was treated before entering the system in one of the following three ways:
• untreated water (Control)
• ultrafiltration (UF) filters particles <500 nm
• nanofiltration (NF) filters particles <1 nm.
The drop in pressure of the water coming out of the tap at the end of the system compared to the pressure of water entering the system was measured.
[Source: reprinted from Water Research, 47(8), G. Liu, M.C. Lut, J.Q.J.C. Verberk, J.C. Van Dijk, A comparison of additional
treatment processes to limit particle accumulation and microbial growth during drinking water distribution, pp 2719–2728,
Copyright (2013), with permission from Elsevier ]
Compare and contrast the effect of ultrafiltration and nanofiltration on the drop in pressure.
[3]
a. both cause pressure to drop ✔
b. pressure always higher in both compared to control ✔
c. nanofiltration causes least drop in pressure
OR
ultrafiltration causes the most drop in pressure ✔
d. the drop in pressure for ultrafiltration is more irregular than for nanofiltration ✔
