**2.3 Physicochemical analysis**

### *2.3.1 pH*

The pH values of the samples were determined at the point of sampling using a portable pH meter after calibrating against buffer solution (pH 4.7 and 9.2).

### *2.3.2 Turbidity*

The turbidity of the samples was determined using the turbidity meter (Labtech digital model), and EPA 180 was selected as the measurement mode.

### *2.3.3 Total dissolved solids (TDS)*

TDS was determined by an electrometric method using a TDS meter (Jenway, model 4076).

### *2.3.4 Dissolved oxygen (DO)*

DO is the amount of gaseous oxygen dissolved in the water. It was determined using a dissolved oxygen meter (Model H1 9146, HANNA) as described by AOAC [16].

### *2.3.5 Biological oxygen demand (BOD)*

BOD measures the amount of dissolved oxygen used by microorganisms in the oxidation of organic matter in a water sample. The BOD was determined by collecting the water sample in a sealed bottle, incubating for a standard period in the dark (usually 5 days at 200°C), and determining the residual oxygen in the water at the end of incubation (Model H1 9146, HANNA). BOD was determined using the following formula as described by AOAC [16].

$$\text{BOD} = (\text{DO}\_1\text{-DO}\_5) \text{ mg/l} \tag{1}$$

Where: DO1 = Sample before incubation. DO5 = Sample after 5 days of incubation.

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

COD is the amount of oxygen consumed under specified conditions of organic and oxidizable inorganic matter in water and wastewater. The COD is determined first by pipetting 10 ml of the water sample into a conical flask and adding 5 ml of 0.025 N potassium dichromate (K2Cr207). 15 ml of sulfuric acid (H2S04) was added to it, and the solution was diluted with 40 ml of distilled water to get a 70 ml solution. Seven drops of phenolphthalein ferrous sulfate indicator were added, and the solution was allowed to cool. The solution was titrated with 0.025 N ferrous ammonium sulfate. A blank solution was also titrated. COD was determined by using the following formula: *Pollution Evaluation of Industrial Effluents from Consolidated Breweries: A Case Study… DOI: http://dx.doi.org/10.5772/intechopen.105955*

$$\frac{(T\_1 - T\_2) \times N \times 8000 \times C}{\text{Volume of water sample used}} (\text{mg/l}) \tag{2}$$

Where:

T1 = Titer value for blank.

T2 = Titer value for effluent sample.

N = Normality of the ferrous ammonium Sulfate used is 0.025.

C = Chloride correction which is in Milligram per liter of chloride � 0.03.

8000 = Milliequivalent weight of oxygen x 1000 mL/L.

*2.3.7 Chloride*

Ten ml of the water sample was pipetted into a conical flask with 3 drops of potassium chromate (K2Cr02) and the solution was titrated with 0.1 N silver nitrate (AgNO3). Chloride was determined by using the following formula:

$$\frac{(T\_v \ge 0.003546 \ge 105) \text{mg}}{\text{l}} \tag{3}$$

Where:

Tv = Titer value of sample. 0.003546 = equivalent weight of chloride

### *2.3.8 Sulfate*

Ten ml of water sample was pipetted into a conical flask plus 5 ml of 2 N HCl and 0.05 N BaCl2. The solution was boiled for 5 minutes and allowed to cool. Two ml of ammonium (NH4 + ) and 5 ml of 0.01 N EDTA were added to the solution and boiled for 5 minutes. Five ml of pH buffer 10 and 3 drops of Eriochrome black) indicators were added. The solution was titrated with 0.01 N MgCl2. Sulfate was determined by using the following formula:

$$\left(\frac{10 - (T\_v \times 0.93) \times 96.01484}{10}\right) \text{mg/l} \tag{4}$$

Where: Tv = Titrate value of the sample. 96.01484 = molecular weight of sulfate. 0.93 = Constant. 10 = Volume of water sample used.

### *2.3.9 Analysis of effluent samples for heavy metals concentration*

An effluent sample of 200 mL was measured into a 500 mL beaker, and 5 mL of concentrated nitric acid was carefully added. This solution was concentrated to 20 mL by heating in a water bath for a few hours. The concentrated extract was cooled and transferred into a 50 mL standard flask, then made up to mark with distilled water. Heavy metal (Pb, Cd, Zn, As, Cr, Fe, Mn, Co, and Ni) contents of the samples were determined using atomic absorption spectrophotometer (Spectra AA Varian 400 plus) involving direct aspiration of the aqueous solution into air-acetylene flame. A

reagent blank was prepared and analyzed. Heavy metal concentrations of a series of standards were determined and a calibration graph was developed. From the graph, the concentrations of heavy metals in the sample were calculated as described by Braid *et al.* [17].

### **2.4 Ecological risk assessment**

### *2.4.1 Contamination factor (CF)*

CF is the extent of pollution of the contaminant of interest, it is expressed:

$$\text{CF} = \frac{\text{chemical contaminant of interest}}{\text{background value using WHO standard}} \tag{5}$$

The following terminology was used to describe the contamination factor:

i. CF < 1: low contamination factor;

ii. 1 ≤ CF < 3: moderate contamination factor;


### *2.4.2 Degree of contamination (Cdeg)*

This is the summation of the contamination factor of all chemical contaminants in the study site. It is calculated as follows:

$$\mathbf{C\_{deg}} = \sum (\mathbf{CF}) = \mathbf{CF\_1} + \mathbf{CF\_2} + \mathbf{CF\_3} + \dots + \mathbf{CF\_n} \tag{6}$$

For the description of contamination degree (Cdeg), the following terminologies have been used:


### *2.4.3 Modified degree of contamination (mCdeg)*

This is the average effect of all chemical contaminants of interest, the advantage of mCdeg is that it quantifies the chemical contaminants into a composite aggregate to derive salient information about the study site using the formula:

*Pollution Evaluation of Industrial Effluents from Consolidated Breweries: A Case Study… DOI: http://dx.doi.org/10.5772/intechopen.105955*

$$m\mathbf{C}\_{\text{deg}} = \frac{1}{n} \sum (\mathbf{CF}) \tag{7}$$

Where: n is the total chemical contaminant and CF is the contamination factor. mCdeg is classified as:

i. mCdeg <4: low moderate contamination;

ii. 4 ≤ mCdeg <16: medium moderate contamination;

iii. 12 ≤ mCdeg <20: high moderate contamination;

iv. mCdeg ≥20: extreme moderate contamination.

*2.4.4 Pollution load index (PLI)*

This is the geometric mean of CF value to the nth number of chemical contaminants of interest, it is given as described by Tomlinson *et al.* [18]:

$$\text{PLI} = \left(\text{CF}\_1 \times \text{CF}\_2 \times \text{CF}\_3 \times \dots \times \text{CF}\_n\right)^{1/n} \tag{8}$$

Where: n is the total chemical contaminant. CF is the contamination factor. The PLI gives the level of pollution classified as:

i. PLI < 1: no pollution;

ii. 1 < PLI < 2: modest pollution;

iii. 2 < PLI < 3: high pollution;

iv. 3 < PLI: extremely high pollution.

### *2.4.5 Potential ecological risk index (PERI)*

Assesses the toxicity factor of a particular chemical contaminant of interest, where the definite contamination status is evaluated concerning the ecosystem. It is expressed as shown in Eq. (9) and (10). A methodology to assess ecological risks for aquatic pollution was developed by Hakanson [19]. The ecological risk index (RI) is calculated as a sum of eight elements of heavy metals (As, Cd, Cr, Ni, Mn, Pb, Co, and Zn).

$$\text{PERI} = \sum \mathbf{E\_r} = \mathbf{TF} \times \mathbf{CF} \tag{9}$$

$$\mathbf{R}\_{\mathbf{i}} = \sum \mathbf{E\_r} \tag{10}$$

Where:

Er is the ecological risk index of different chemical contaminants,

TF is the toxicity factor of each chemical contaminant of interest as described by Hussain et al. [20] and Umeh et al. [21].

CF is the contamination factor in Eq. (5),

RI is the risk index calculated as the sum of the potential ecological risk factors for heavy metals in the wastewater.

Er and RI values are categorized using:

i. Er <40 and RI <150: low ecological risk;

ii. 40 < Er ≤80 and 150 < RI <300: moderate ecological risk;

iii. 80 < Er ≤160, appreciable ecological risk;

iv. 160 < Er ≤320 and 300 < RI <600: high ecological risk;

v. Er > 320 and RI ≥ 600: extremely high ecological risk.
