Water Treatment Technologies and Their Costs - Global Drinking Water Management and Conservation - page 47

sediment removal are included. We would argue that where primary disinfection
is absolutely necessary, UV would compare favorably with chlorine for primary
disinfection. Of course in North America, for the distribution system the law
requires chlorine residual, and perhaps that is why many small systems continue
to rely on chlorine as a primary disinfection for surface water systems. The
concern over disinfection byproducts (DBPs) might tip the scale in favor of UV
for primary disinfection. But again site-speci c considerations need to be taken

into account. Furthermore, when the source water is groundwater, which is
otherwise free of contaminants, the only cost is the cost of residual chlorine for
the distribution system. In this case, chlorine may be cheaper than UV.
4. If a community is concerned with the removal of micro-pollutants, then a UV-
based Advanced Oxidation Process would be cheaper than ozonation, provided
the

flow rate is not too small. (For example, the City of Cornwall in Canada uses
AOP for 2 months of the year for taste and odor issues.)
5. Our results indicate that ozonation is competitive (2008 CDN $), and so there
are number of ozonation plants in Saskatchewan and Manitoba. We estimate
that at the beginning of 2011, there were 30 small systems using this technology
in the two provinces (Table 3.8 ).
6. In general,manufacturers

'

rated costs tend to be lower than actual plant-level average
costs as they do not include some plant-speci c costs, such as higher labor, energy,

and transportation costs due to remoteness from large urban areas (Table 3.9 ).
7. It should be noted that some of the estimations are based on limited data.
Needless to add that the costs estimates cannot be treated for predictive pur-
poses, as all useful predicted costs must also take into account a number of
location-speci c costs (Table 3.10 ).

c water treatment facility will
need to take account of raw source water quality, the actual target quality for small
systems seems to be to meet only the minimum regulatory requirements. Our results
show that for surface water, unless the raw water is high in color and in turbidity, a
UV-based plant would be economical and cost-effective even when the additional
cost of sediment removal is added. This conclusion is especially true for small
plants producing less than 100 cubic meters per day. Such a plant could obtain the
same or better quality water with UV for less than 8 cents per cubic meter per day.
Our

Our general conclusion is that while any speci

finding of the cost-effectiveness of UV is in agreement with USEPA ( 1996 ),
Gadgil ( 1998 ) and Parrotta and Bekdash ( 1998 ).

Appendix A

Estimation results for Table 3.4 based on the model: yi i ¼ b 1 X b 2

þ e i where y i is the
average cost per cubic meter, Xi i is the capacity in cubic meters and

i

e i is the error

term, which satis es the standard Gaussian assumptions