**4. Discussion**

Water quality in an aquatic environment is very important for the survival of its flora and fauna. Water pH can affect aquatic organisms as their metabolic activities are pH-dependent [22, 23]. The pH across the sampling points ranges from 6.20 in sample A to 6.98 in sample B, indicating slight acidity. A significant (P ≤ 0.05) difference was observed between the pH values for each sampling point, although, B and D were within the WHO [24] guideline regulatory limit of 6.5–8.5 set for drinking water, while samples A and C were a little below the standard limit. The slight acidity could be attributed to the chemicals used in the treatment processes and the water may serve as a sink for various wastes and chemical preservatives used in the brewery such as oxides of sulfur, nitro, carbon, and phosphor in turn form sulfuric, nitric, carbonic and phosphoric acid on reaction with water leading to microbial bloom from rich nutrients source thereby causing reduction in dissolved oxygen, increase turbidity, conductivity, odor and diminish aquatic esthetic respectively. Water pH helps to control metal solubility, and water hardness and serves as an indicator of water pollution [7, 9].

Nitrate in the present study was all below-recommended limit when compared to the WHO [24] standard for safe drinking water. Nitrate is alleged to be an indicator of pollution in the public water supply [25]. It is the stable form of nitrogen that plays a significant role in the process of eutrophication. The conductivity range of the various sampling points varied considerably across the study area. Point B showed the highest value and, therefore, decreased along with the sampling points, most likely due to the effect of dilution and removal of soluble salts by biological utilization.

The biological oxygen demand (BOD) and chemical oxygen demand (COD) are useful parameters in water quality analysis. The highest and lowest BOD values were recorded at sampling points A and B, respectively. Biological oxygen demand is the amount of oxygen required by aerobic microorganisms to stabilize the organic material of wastewater at a standardized temperature (20°C) and time of incubation (usually 5 days). It is used to indicate the organic strength of water. When BOD is less than 4 mg/l, water is deemed to be reasonably clean and unpolluted, while a BOD level greater than 10 mg/l indicates pollution [26].

Chemical oxygen demand is a measure of organic contamination in water. It is the amount of dissolved oxygen required to cause chemical oxidation of the organic material in water and is a key indicator of the environmental health of surface water [18]. There was a gradual increase in chemical oxygen demand from point B to point D. Chemical oxygen demand values were below the WHO recommended value of 200 mg/l [24]. High chemical oxygen demand COD values indicate pollution due to oxidizable organic matter [27].

Phosphate concentration was high in all sampling points and greater than the WHO recommended value of 2.0 mg/l. Phosphate is known as a limiting nutrient in the aquatic ecosystem [28]. There is little variation in dissolved oxygen values of effluent samples across the study areas. The dissolved oxygen concentration is a function of temperature, pressure, salinity, and biological activities in the water body. The tropical aquatic ecosystem should have a dissolved oxygen concentration of at least 5 mg/l in other to support diversified biota, including fish [29–32]. The level of 4.70 mg/l for point B was within the WHO, [24] standard value of 5 mg/l necessary for aquatic productivity, while other points were above the standard limit of 5 mg/l.

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

The highest value of sulfate was observed in point C (35.39 mg/l). This value is far below the permissible limit stipulated by World Health Organization WHO, [24]. The present work was in line with the work of Alao [30], who also reported low sulfate levels in the water receiving brewery effluent in Majawe Ibadan.

The values of chloride and iron obtained from point B, C, and D falls below the WHO permissible limit, while point C was within the 1 mg/l desirable level from WHO. The result of chloride agrees with Imoobe and Koye [33], who reported the value of chloride in Eruvbi Stream to be below the permissible limit stipulated by the World Health Organization [24]. The discharge of industrial effluents into receiving water bodies invariably results in the presence of a high concentration of pollutants in the water and sediments.

The pollutants are present in concentrations that may be toxic to different organisms [34–36]. The concentration of Cadmium across the study area ranged from 0.001 at sampling points B and D to 0.007 at sampling point C. The values recorded were lower than (0.043 mg/l) and (0.072 mg/l) in the water reported by Oguzie and Okhagbuzo [37]. The value of all samples assessed was above the permissible limit of 0.003 ppm set by WHO [24] for drinking water except for sampling points B and D. High concentrations of Cadmium (Cd) have been reported to inhibit the bio-uptake of Phosphorus and Potassium by plants [38].

Specific industries involved in electroplating, pigments production, chemicals, and alloy processing are sources of cadmium to the urban environment. Chromium (Cr) levels in the effluents were relatively low across the different sampling points. The concentrations of chromium in effluents were below the 0.050 mg/l value recommended by the World Health Organization (WHO) [24] in industrial effluents except for sampling point B.

A high concentration of nickel (Ni) was recorded in the effluent samples ranging from 0.114 ppm in point D to 0.246 ppm in point A. The concentrations of nickel in effluents are higher than the <1 mg/l value recommended by the WHO [24] in industrial effluents. Ni has wide applications in the manufacture of batteries, fertilizer, welding products, electroplating, and household appliances and has essential functions in every area of industrial activity [2].

Lead (Pb) and Arsenic (As), a major environmental pollutant is a multi-organ poison that, in addition to well-known toxic effects, depresses immune status and causes damage to the central nervous system, kidney, and reproductive system [39]. The lead (Pb) values were quite low in all the sampling points except in point E where it was not detected. All the points showed a lead value above the maximum acceptable concentration.

### **4.1 Contamination factor/pollution index**

The contamination factor (CF) values were revealed in **Table 2**. Arsenic (As) can be categorized as a very high contamination factor across all the sampling locations. The highest values of CF of As at location C (48.46) and the lowest at location B (33.12), indicating severe anthropogenic contribution to the contamination load of rivers at this site. The CF of Cd (Cadmium) can be categorized as low to moderate. Two locations (B and D) can be categorized as having low CF of Cd, and two locations (A and C) can be categorized as having moderate CF of Cd. Lead (Pb) can be categorized as a very high CF across all the sampling locations. The highest values of CF of Pb at location A (32) and the lowest at location B (12.1). The CF of Ni (Nickel) can be categorized as considerable to very high contamination. Two locations


*\*A-un treated effluent, B- treated effluent, C- contact point of the treated effluent with the river and D- 10 kilometers away from the contact point. PLI: pollution load index; C.deg.: degree of contamination; M-C.deg.: modified degree of contamination.*

### **Table 2.**

*Contamination factor, pollution index and contamination index.*

(C and D) can be categorized as having considerable CF of Ni, and two locations (A and B) can be categorized as having very high CF of Ni. The CF of cobalt and Zinc can be categorized as low contamination factors of Co and Zn, respectively. Other elements such as Cr (0.26–2.48), Mn (0.29–1.035), and Fe (0.62–3.42) can be categorized as low to moderate CF. The result indicates that contamination of effluents from Nigeria Brewery contributed to As and Pb [21].

The pollution Load Index (PLI) is a resourceful tool to measure and compare contamination. Analyzed effluents samples discharged into rivers at locations A (2.1), B (1.25), and C (1.16) displayed higher PLI values (PLI > 1) and progressive deterioration in quality. Location D was observed to have a low pollution index value of 0.7. The order for PLI was A > B > C > D. Higher PLI values in rivers demonstrated substantial anthropogenic impacts on the river quality signifying the need for immediate intervention to prevent pollution. In contrast, lower PLI values pointed to no considerable anthropogenic activities, signifying no need for intervention but requiring constant monitoring [31].

Degrees of contamination (Cdeg) values of effluents from Nigeria's brewery are revealed in **Table 2**. The degree of contamination across the sampling locations can be categorized into four categories according to the Patil *et al.* [28] classification. Sampling locations A, C, and D can be categorized as having a very high degree of contamination (Cd value = 94.7, 71.50, and 50.54, respectively), this indicates very severe anthropogenic pollution at these sampling sites. Location B indicates a considerable degree of contamination with a Cd value of 25.137. The present study revealed Pb and Ni as the most severe component causing moderate to very high river contamination. A similar pattern was noted for contamination degree (Cdeg), where sampling locations having dominant anthropogenic activities displayed a high Contamination degree. Regular monitoring of the river for the presence of trace elements, especially Arsenic, lead, and nickel, is required [34].

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


*A- un treated effluent, B- treated effluent, C- contact point of the treated effluent with the river and D-10 kilometers away from the contact point.*

### **Table 3.**

*Potential ecological risk index.*

### **4.2 Potential ecological risk index method**

The evaluation results on the potential ecological risk factor (Eir) and the potential ecological risk index (RI) are summarized in **Table 3**. The order of potential ecological risk coefficient (Eir) of heavy metals in discharge effluents was As > Pb > Cd > Ni > Cr > Mn > Co > Zn. The mean potential ecological risk coefficient of Cd, Cr, Mn, Ni, Co, and Zn were all lower than 40, which is low ecological risk. At the same time, the mean potential ecological risk coefficient of Pb and As were greater than 80 and 320, respectively, which indicates moderate to extremely high ecological risk. All the sampling locations were at High to very high-risk levels where the RI values were much greater than 600. However, because most samples are contaminated with As, Pb, and Ni, their impact on the ERI became very obvious and predominant. Therefore, the present study indicates that As, Pb, and Ni were the major heavy metal posing an ecological risk in the study area [21, 31, 35].
