Risk Assessment for Safe Drinking Water Supplies - Global Drinking Water Management and Conservation - page 142

ii. Nonhealth or esthetic quality performance

The esthetic quality refers to the taste, color, and odor of drinking water. For
example, iron and manganese residues within the distribution systems can cause
water discoloration, which many consumers find unacceptable. Australian con-

sumers were also dissatis ed with the use of chlorine as it leaves a metallic taste in

the water. In 2011/12, around 68 percent of localities complied with all of the
esthetic guidelines, while 92 percent of esthetic analyses for aluminum, color, and
chloride met with the esthetic guidelines (Fig. 6.7 ). The remaining concerns could
perhaps be attributed to (a) lack of alternative sources, (b) the impact of climate
change on groundwater, and (c) groundwater abstraction near the coast (Water
Corporation of Western Australia 2012 ).
It is a challenge to achieve the esthetic requirements of the Guidelines when
there is limited availability of sources for drinking water and the cost of treatment is
high (Water Corporation of Western Australia 2012 ).

6.5 Conclusions

The above review of the methods and tools of risk assessment for drinking water as
well as the case studies show some interesting lessons. First, in the light of repeated
outbreaks of waterborne disease even in developed countries, it is important to
determine risk and decide on what level of risk public authorities are willing to accept,
as there is no such thing as completely riskless water supply; there will always be
unforeseen events and even accidents that can compromise water safety. Thus public
policy should be guided by what are judged to be minimally acceptable risks in all
sectors of public life. In drinking water, reducing pathogens by as much as
99.99 percent (4-log reduction) may be safe only if the source water is of suf

ciently
good quality. If the source water quality is poor to start with, then higher log
reductions may be necessary. A multibarrier approach indicates that increasing
source water protection can go a long way in reducing overall risks. In most countries,
point source pollution control is the easiest to handle, provided there is political will
and available financial resources. In many developing countries, point source pol-

lution control either does not exist or the legislation is not being enforced adequately.
Second, nonpoint source pollution remains a signi

cant threat to water supplies
globally, and it is essential to establish some risk assessment framework, like that
recommended by the U.S. EPA. For developing countries, the WHO-style “ water

safety plans could work in principle, but as the case studies show, a precondition is

the required education of the community and also an adequate administrative
infrastructure to implement water safety plans. The WHO-style water safety plan
must identify the control point, at which the right intervention can be carried out.
Without the knowledge of the control point, there can be no action taken. Without
the corrective action, water safety cannot be enhanced.

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