Page 84 - Water and wastewater engineering

GENERAL WATER SUPPLY DESIGN CONSIDERATIONS 2-27

The two protozoa of most concern are Giardia lamblia and Cryptosporidium parvum. Both
pathogens are associated with gastrointestinal illness. The dormant Giardia cysts and Cryptosporidium
oocysts are carried in animals in the wild and on farms.

Radiological Characteristics
The use of atomic energy as a power source and the mining of radioactive materials, as well as
naturally occurring radioactive materials, are sources of radioactive substances in drinking water.
Drinking water standards have been established for alpha particles, beta particles, photons emit-
ters, radium-226 and - 228, and uranium.
Although no standard has been established for radon, it is of concern because it is highly
214
218
214
volatile and is an inhalation hazard from showering. Its decay products ( Po, Po, and Bi)
release alpha, beta, and gamma radiation.
Raw Water Characteristics
The quality of the raw (untreated) water plays a large role in determining the unit operations
and processes required to treat the water. A comparison of the source water quality with the
desired finished water quality provides a basis for selecting treatment processes that are capable
of achieving the required treatment efficiency.
In addition to the regulated constituents discussed under “Water Quality Standards” in the
next section there are a number of other common analyses used to assess the characteristics of
the water with respect to potential treatment requirements. That is, the need for treatment, the
difficulty of treatment, and the unit operations and processes that may be required. These are
listed in Table 2-12 by the test used for their determination.
If the client’s water quality objectives include a soft finished water and the source water is a
groundwater or a surface water with a large groundwater contribution, the dissolve cations and
anions as well as alkalinity, carbon dioxide, pH, and total hardness are of particular interest. For
surface water that will not be softened, sodium, alkalinity, conductivity, pH, and total organic
carbon provide useful information beyond the regulated compounds.
For expansion of existing plants, these data may be readily available. Because groundwater
quality is not highly variable, annual grab samples provide sufficient data for plant design. Because

TABLE 2-12
Common analyses to characterize raw water
Alkalinity Iron
Bicarbonate Manganese
Carbonate Magnesium
Total pH
Ammonia Nitrate
Arsenic Nitrite
Calcium Silica
Carbon dioxide Sodium
Chloride Total hardness
Conductivity Total Kjeldahl nitrogen
Hydrogen sulfide Total organic carbon
Hydroxide Turbidity