Disadvantages

- Form significantly higher disinfection by-products.

- Form higher trihalomethanes (THMs) than chloramination.

- Form higher haloacetic acids (HAAs) than chloramination.

- Take longer to implement than chloramination (eight to ten years).
Note: Both THMs and HAAs are suspected carcinogens.

Ozonation
Advantages

~ Very effective primary (source w>'er) disinfectant.
- Ozone and biological filtration: ice highest quality water and minimize the use of chlorine or chloramine.

Disadvantages

Not suitable as a secondary disinfectant because it does not maintain a residual beyond a few minutes.
- Must be used in conjunction with filtration and is followed by a chlorine-based secondary disinfectant.
- May magnify the bacterial regrowth problem by breaking down naturally occurring organics,
- Produce more bacterial food, which in turn may require greater amounts of secondary disinfectant to control

increased bacterial regrowth.

In summary:

Chioramine has advantages with respect to health issues, palatability to consumers, and overall costs of
implementation. However, the disadvantage of chloramine is that it h1s a higher risk of impact to the aquatic
environment. This impact could have significant legal ramifications  -elease of chloraminated water would

contravene the Federal Fisheries Act.

Rechlorination (higher chlorine levels) is more acceptable from an environmental perspective because the
frequency and magnitude of its impacts will be less than those from use of chloramine. The risk of contravening
the Fisheries Act with spills, although present, is much less with rechlorinate water than with chloraminated
water. B.C, Health Act's requirements can also be met with rechlorination, however, filtration of all sources may

be required to satisfy future drinking guidelines.

Filtration to a small degree and ozone with biological filtration to treater degree will reduce or minimize the
amount of secondary disinfectant required in.the drinking water but will not eliminate it altogether.

Six options have been developed to comply with the B.C. Health Act requirements (See Table 2).

Options {and Option 2 assume chloramine is used and that filtration of all sources is not needed specifica
because disinfection by-products are less than proposed standards.