*3.2.12 Dissolved oxygen*

*Water Quality - Science, Assessments and Policy*

inductively coupled plasma (ICP) [10].

*3.2.9 Iron and manganese*

to most people [10].

*3.2.10 Copper and zinc*

measurements [10].

*3.2.11 Hardness*

types of hardness:

removed by boiling, and

sulfates and chlorides [10, 21, 22]

than 75 mg/L is considered to be soft.

[10, 11].

used method depends on the type of water sample [10].

There are four methods to determine ion fluoride in water; the selection of the

Although iron (Fe) and manganese (Mn) do not cause health problems, they impart a noticeable bitter taste to drinking water even at very low concentration

These metals usually occur in groundwater in solution as ferrous (Fe2+) and manganous (Mn2+) ions. When these ions are exposed to air, they form the insoluble ferric (Fe3+) and manganic (Mn3+) forms making the water turbid and unacceptable

These ions can also cause black or brown stains on laundry and plumbing fixtures [7]. They are measured by many instrumental methods such as atomic absorption spectrometry, flame atomic absorption spectrometry, cold vapor atomic absorption spectrometry, electrothermal atomic absorption spectrometry, and

Copper (Cu) and zinc (Zn) are nontoxic if found in small concentrations [10]. Actually, they are both essential and beneficial for human health and growth of plants and animals [25]. They can cause undesirable tastes in drinking water. At high concentrations, zinc imparts a milky appearance to the water [10]. They are measured by the same methods used for iron and manganese

Hardness is a term used to express the properties of highly mineralized waters [10]. The dissolved minerals in water cause problems such as scale deposits in hot

Calcium (Ca2+) and magnesium (Mg2+) ions cause the greatest portion of hardness in naturally occurring waters [9]. They enter water mainly from contact with

These ions are present as bicarbonates, sulfates, and sometimes as chlorides and nitrates [10, 26]. Generally, groundwater is harder than surface water. There are two

• *Temporary hardness* which is due to carbonates and bicarbonates can be

• *Permanent hardness* which is remaining after boiling is caused mainly by

Water with more than 300 mg/L of hardness is generally considered to be hard, and more than 150 mg/L of hardness is noticed by most people, and water with less

From health viewpoint, hardness up to 500 mg/L is safe, but more than that may cause a laxative effect [10]. Hardness is normally determined by titration with ethylene diamine tetra acidic acid or (EDTA) and Eriochrome Black and Blue

indicators. It is usually expressed in terms of mg/L of CaCO3 [10, 19].

water pipes and difficulty in producing lather with soap [11].

soil and rock, particularly limestone deposits [10, 27].

**12**

Dissolved oxygen (DO) is considered to be one of the most important parameters of water quality in streams, rivers, and lakes. It is a key test of water pollution [10]. The higher the concentration of dissolved oxygen, the better the water quality.

Oxygen is slightly soluble in water and very sensitive to temperature. For example, the saturation concentration at 20°C is about 9 mg/L and at 0°C is 14.6 mg/L [22].

The actual amount of dissolved oxygen varies depending on pressure, temperature, and salinity of the water. Dissolved oxygen has no direct effect on public health, but drinking water with very little or no oxygen tastes unpalatable to some people.

There are three main methods used for measuring dissolved oxygen concentrations: the colorimetric method—quick and inexpensive, the Winkler titration method—traditional method, and the electrometric method [10].

## *3.2.13 Biochemical oxygen demand (BOD)*

Bacteria and other microorganisms use organic substances for food. As they metabolize organic material, they consume oxygen [10, 22]. The organics are broken down into simpler compounds, such as CO2 and H2O, and the microbes use the energy released for growth and reproduction [22].

When this process occurs in water, the oxygen consumed is the DO in the water. If oxygen is not continuously replaced by natural or artificial means in the water, the DO concentration will reduce as the microbes decompose the organic materials. This need for oxygen is called the biochemical oxygen demand (BOD). The more organic material there is in the water, the higher the BOD used by the microbes will be. BOD is used as a measure of the power of sewage; strong sewage has a high BOD and weak sewage has low BOD [22].

The complete decomposition of organic material by microorganisms takes time, usually 20 d or more under ordinary circumstances [22]. The quantity of oxygen used in a specified volume of water to fully decompose or stabilize all biodegradable organic substances is called the ultimate BOD or BODL.

BOD is a function of time. At time = 0, no oxygen will have been consumed and the BOD = 0. As each day goes by, oxygen is used by the microbes and the BOD increases. Ultimately, the BODL is reached and the organic materials are completely decomposed.


**Table 2.**

*Classification of water according to its hardness.*

**Figure 3.** *BOD curve [22].*

A graph of the BOD versus time is illustrated as in **Figure 3**. This is called the BOD curve, which can be expressed mathematically by the following equation:

$$\mathbf{BOD\_t = BOD\_L \times \{1 - 10^{-kt}\}}\tag{10}$$

where BODt = BOD at any time t, mg/L; BODL = ultimate BOD, mg/L; k = a constant representing the rate of the BOD reaction; t = time, d.

The value of the constant rate k depends on the temperature, the type of organic materials, and the type of microbes exerting the BOD [22].

#### *3.2.14 Chemical oxygen demand (COD)*

The chemical oxygen demand (COD) is a parameter that measures all organics: the biodegradable and the non-biodegradable substances [22]. It is a chemical test using strong oxidizing chemicals (potassium dichromate), sulfuric acid, and heat, and the result can be available in just 2 h [10]. COD values are always higher than BOD values for the same sample [22].

#### *3.2.15 Toxic inorganic substances*

A wide variety of inorganic toxic substances may be found in water in very small or trace amounts. Even in trace amounts, they can be a danger to public health [11]. Some toxic substances occur from natural sources but many others occur due to industrial activities and/or improper management of hazardous waste [22]. They can be divided into two groups:


**15**

*3.3.1 Bacteria*

*Water Quality Parameters*

ric methods [10].

*3.2.16 Toxic organic substances*

*3.2.17 Radioactive substances*

to the living tissues [34, 35].

specified pollutant [17].

**3.3 Biological parameters of water quality**

microorganisms in wastewater is likely to occur [38].

*DOI: http://dx.doi.org/10.5772/intechopen.89657*

binding the hemoglobin sites and prevents the red blood cell from carrying the oxygen [11]. This causes a blue skin color syndrome, which is called cyanosis [33]. It also causes chronic effects on the central nervous system and thyroid [33]. Cyanide is normally measured by colorimetric, titrimetric, or electromet-

There are more than 100 compounds in water that have been listed in the literature as toxic organic compounds [11, 22]. They will not be found naturally in water; they are usually man-made pollutants. These compounds include insecticides, pesticides, solvents, detergents, and disinfectants [11, 21, 22]. They are measured by highly sophisticated instrumental methods, namely, gas chromatographic (GC), highperformance liquid chromatographic (HPLC), and mass spectrophotometric [10].

Potential sources of radioactive substances in water include wastes from nuclear

Radon gas is of a great health concern because it occurs naturally in groundwater and is a highly volatile gas, which can be inhaled during the showering process [35]. For drinking water, there are established standards commonly used for alpha particles, beta particles, photons emitters, radium-226 and -228, and uranium [34, 35]. The unit of radioactivity used in water quality applications is the picocurie per liter (pCi/L); 1 pCi is equivalent to about two atoms disintegrating per minute.

One of the most helpful indicators of water quality may be the presence or lack of living organisms [10, 15]. Biologists can survey fish and insect life of natural waters and assess the water quality on the basis of a computed species diversity index (SDI) [15, 19, 36, 37]; hence, a water body with a large number of wellbalanced species is regarded as a healthy system [17]. Some organisms can be used as an indication for the existence of pollutants based on their known tolerance for a

Microorganisms exist everywhere in nature [38]. Human bodies maintain a normal population of microbes in the intestinal tract; a big portion of which is made up of coliform bacteria [38]. Although there are millions of microbes per milliliter in wastewater, most of them are harmless [37]. It is only harmful when wastewater contains wastes from people infected with diseases that the presence of harmful

Bacteria are considered to be single-celled plants because of their cell structure and the way they ingest food [10, 37]. Bacteria occur in three basic cell shapes: rodshaped or bacillus, sphere-shaped or coccus, and spiral-shaped or spirellus [19]. In less than 30 min, a single bacterial cell can mature and divide into two new cells [39].

power plants, industries, or medical research using radioactive chemicals and mining of uranium ores or other radioactive materials [11, 21]. When radioactive substances decay, they release beta, alpha, and gamma radiation [34]. Exposure of humans and other living things to radiation can cause genetic and somatic damage

There are many sophisticated instrumental methods to measure it [35].

#### *Water Quality Parameters DOI: http://dx.doi.org/10.5772/intechopen.89657*

binding the hemoglobin sites and prevents the red blood cell from carrying the oxygen [11]. This causes a blue skin color syndrome, which is called cyanosis [33]. It also causes chronic effects on the central nervous system and thyroid [33]. Cyanide is normally measured by colorimetric, titrimetric, or electrometric methods [10].

## *3.2.16 Toxic organic substances*

*Water Quality - Science, Assessments and Policy*

A graph of the BOD versus time is illustrated as in **Figure 3**. This is called the BOD curve, which can be expressed mathematically by the following equation:

where BODt = BOD at any time t, mg/L; BODL = ultimate BOD, mg/L; k = a

The value of the constant rate k depends on the temperature, the type of organic

The chemical oxygen demand (COD) is a parameter that measures all organics: the biodegradable and the non-biodegradable substances [22]. It is a chemical test using strong oxidizing chemicals (potassium dichromate), sulfuric acid, and heat, and the result can be available in just 2 h [10]. COD values are always higher than

A wide variety of inorganic toxic substances may be found in water in very small or trace amounts. Even in trace amounts, they can be a danger to public health [11]. Some toxic substances occur from natural sources but many others occur due to industrial activities and/or improper management of hazardous waste [22]. They

namely, cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), silver (Ag), arsenic (As), barium (Ba), thallium (Tl), and selenium (Se) [22, 28]. They have a wide range of dangerous effects that differ from one metal to another. They may be acute fatal poisons such as (As) and (Cr6+) or may produce chronic diseases such as (Cd, Hg, Pb, and Tl) [21, 29–32]. The heavy metals concentration can be determined by atomic absorption photometers, spectrophotometer,

<sup>−</sup>) and cyanides

• *Metallic compounds:* This group includes some heavy metals that are toxic,

or inductively coupled plasma (ICP) for very low concentration [10].

(CN<sup>−</sup>), nitrate has been discussed with the nitrogen in the previous section. Regarding cyanide, as Mackenzie stated [11] it causes oxygen deprivation by

• *Nonmetallic compounds:* This group includes nitrates (NO3

constant representing the rate of the BOD reaction; t = time, d.

materials, and the type of microbes exerting the BOD [22].

*3.2.14 Chemical oxygen demand (COD)*

**Figure 3.** *BOD curve [22].*

BOD values for the same sample [22].

*3.2.15 Toxic inorganic substances*

can be divided into two groups:

BODt = BODL × (1 − 10−kt) (10)

**14**

There are more than 100 compounds in water that have been listed in the literature as toxic organic compounds [11, 22]. They will not be found naturally in water; they are usually man-made pollutants. These compounds include insecticides, pesticides, solvents, detergents, and disinfectants [11, 21, 22]. They are measured by highly sophisticated instrumental methods, namely, gas chromatographic (GC), highperformance liquid chromatographic (HPLC), and mass spectrophotometric [10].
