Читать книгу Introduction to Desalination - Fuad Nesf Alasfour - Страница 25

Potable water (freshwater) is characterized with salinity less than 500 ppm.

Table 1.2 shows water classification based on salinity, and the standards of WHO for freshwater limit is 500 ppm (0.05 mg/kg).

Table 1.2 Water classification based on salinity content.

Type	Total dissolved salts (TDS)
Freshwater	<1500
Brackish water	1500–10 000
Salt water	>10 000
Seawater	10 000–45 000
Standard seawater	35 000

The chemical concentration in fresh water with 500 ppm are shown in Table 1.3.

Table 1.3 Secondary drinking water regulation [5].

Chemicals	SDWR
Aluminum	0.05–0.2 mg/l
Chloride	250 mg/l
Color	15 color units
Copper	1.0 mg/l
Corrosivity	Non‐corrosive
Fluoride	2.0 mg/l
Foaming agents	0.5 mg/l
Iron	0.3 mg/l
Manganese	0.05 mg/l
Odor	Three threshold odor numbers
pH	6.5–8.5
Silver	0.1 mg/l
Sulfate	250 mg/l
Total dissolved solids (TDS)	500 mg/l
Zinc	5 mg/l

Tables 1.3 and 1.4 show the 2018 Drinking Water Standards and Health Advisories, Secondary Drinking Water Regulations.

Table 1.4 WHO standards for potable water [5].

Constitutes	Concentration (ppm)
Limited values	Max allowed values
Total dissolved salts (TDS)	500	1500
Cl	200	600
SO42+	200	400
Ca2+	75	100
Mg2+	30	150
F−	0.7	1.7
NO3−	<50	100
Cu2+	0.05	1.5
Fe3+	0.10	1.0
NaCl	250	—
pH	7–8	6.5–9

Table 1.5 Thermo‐physical properties of typical seawater at 40 000 ppm and 20 °C.

Density	1.0288 kg/m3
Specific heat capacity	3.973 kJ/(kg °C)
Boiling point elevation, at 20 °C	0.344 K
Boiling point elevation, at 90 °C	0.565 K
Thermal conductivity	0.601 W/(m K)
Dynamic viscosity	1.089 × 10−3 kg/(m2 s)
Kinematic viscosity	10.58 × 10−7 m2/s
Latent heat of vaporization	2355.4 kJ/kg