**3.16 Dissolved oxygen (DO)**

Dissolved Oxygen (DO) levels from the study revealed a range of 1.1 mg/l – 6.87 mg/l and 2.6–8.45, and mean range of 1.28 0.2–5.3 1.4 and 3.94 0.61–7.15 1.12 for dry and rainy seasons respectively. This is lower than the values of 6.51 1.47 mg/l – 8.43 0.21 mg/l reported by Bolarinwa, Fasakin and Fagbenro [23] in the analysis of the physicochemical parameters of coastal waters of Ondo State, Nigeria. The WHO permissible standard for DO is >6 mg/l. Most of the dissolved oxygen concentrations found in water from the sampled sites do not meet the WHO standard for quality drinking water. This could be as a result of the high concentrations of dissolved salts, suspended particles and hardness of the water that preclude the dissolution of oxygen in most of the water from the sampled sites.

The water samples for this study were collected from three main sources. These include well, borehole and pipewater. The taste of water samples from the different sources differ as the pipewater is objectionable as compared to well and borehole sources, which are unobjectionable. In terms of the odor, water from all the sources recorded no odor. The temperature difference across the water sources is not statistically significant. pH across the sources is not significantly different. There is significant difference in Total Dissolved Solids and Turbidity across the various water sources. All other variables are not significantly different across the all sources.

The selected metal ions in water from the three sources are presented in **Table 9**. There was significant difference recorded in fluoride (F¯) across the water sources. All other variables recoded no significant difference across the different water sources in the study area. This implies that, there is not marked difference between the composition and concentration of physicochemical parameters in water from all water sources.

#### **3.17 Discussion**

The water temperature from all sites ranges between 26.7°C – 33. The temperature values obtained from this study were within the WHO permissible limit of 40°C. This is in support of the work by Moerman, Blokker, Vreeburg, and Van Der Hoek [28] that water temperature within the range of 28 – 380c is consider safe for drinking.

pH measure the acidity or alkalinity of the water. The pH values from this range from (6.5–8.9) also reported by Ikhouriah and Oronsaye [19] in Ossiomoo river Ologbo - a tributary of Benin River, Southern Nigeria. All sites in the study area during the dry season were within the WHO permissible limit of 6.5–8.5 except sites SB1 (8.6) SD1 (8.8), SD2 (8.9) SD3 (8.9), MD, (8.6), KS1 (8.9) band KS2 (8.6) these high values indicates alkalinity, and it could be due to high concentration of basic cations, e.g. magnesium, calcium, potassium etc. in the sampled sites. Electricity conductivity values obtained in this study showed that all the sample sites contained an appreciable amount of dissolved ions (10.00–958.00 S/m). The EC of all sites falls within the WHO recommended limit of 500–1,500 ohm/cm.

Turbidity is the impurity status of the water caused by a variety of particles and is a key parameter in drinking water analysis. It is also related to the content of diseases causing organisms in water, which may come from surface runoff. The turbidity values obtained from the study sites range from 0.4–10.6. The standard recommended maximum turbidity limit set by WHO for drinking water is five nephelometric turbidity units (NTU). These results from the open nature of the water, making it easy for impurities that could block light reception to flow into it. All sites in the study area except for sites two sites were below the WHO permissible levels of 5NTU.
