Discolouration in drinking water systems - TU Delft

Propositions
1. Managing discoloured water events in the distribution system demands a multi stage approach incorporating
all aspects of the drinking water system.
This thesis.
2. Dynamic water quality processes in the drinking water distribution systems can only adequately be
analysed using continuous monitoring.
This thesis; Chapter 2.
3. Particles in the drinking water leaving the treatment plant are in most cases the dominant source for
deposits in the network that may cause discolouration.
This thesis, Chapter 3 and 6.
4. The particle load from the treatment plant to the network can drastically be reduced if peaks as a result
of for instance backwashing are avoided. To measure the performance of a treatment plant towards the
peaks, analysis of at least 48 hours of continuous monitoring of particle volume concentration or turbidity
should be considered, characterised with a combination of the average value, the ratio of the 90
and 99,5 percentile values and possibly with the newly developed Surf+90% value.
This thesis, Chapter 2, 3 and 4.
5. Restrictions on the amount of soluble iron in the drinking water leaving the treatment plant, should
limit the consequence of network flocculation.
This thesis, Section 6.2.
6. The reaction of network operators on self-cleaning velocity based networks is almost universal: First
unbelief that it is possible followed by reserved enthusiasm. The reaction of managers is universal: It’s
cheaper, let’s do it.
This thesis, Chapter 4.
7. The lack of a standard procedure for taking sediment samples from networks, makes it difficult to
compare literature data.
(Carriere et al., 2005; Barbeau et al., 2005; Zacheus et al., 2001; Torvinen et al., 2004;, this thesis,
section 6.4.4.)
8. The role of particles as a potential surface for biofilm attachment should not be ignored in the quantitative
assessment of biofilms in drinking water systems.
This thesis, Chapter 3.
9. Fire fighting and fire prevention should be more to water companies than supplying fire flows and
charging fees for fire hydrants. Hydraulic innovations on domestic sprinkler installations leading to a
reduction in required flow would increase the application possibilities within self cleaning velocity
based networks and potentially enhance public health in the same order as total prevention of drinking
water induced Legionellosis.
Experience in Scottsdale Arizona, USA with universal domestic sprinkler ordinance.
10. The primary goal of the governing board of a foundation for (primary) schools should be to facilitate
local school managers to totally focus on the wellbeing of the school, its teachers and children.
11. The introduction of the graphical calculator in the secondary schools seriously frustrated both teachers
and pupils in the joy of mathematics.
12. Raising children is repaying an old debt.
Proposition with the dissertation
“Discolouration in drinking water supply systems: a particular approach”
By ir. J.H.G. Vreeburg and approved by the promoter prof. ir. J.C. van Dijk