Environmental pollution in Nigeria presents an urgent need to assess wastewater treatment facilities in various industries. This article presents an assessment of dissolved air flotation (DAF) operation in a dairy industry. The industry was visited, wastewater treatment facilities were assessed (based only on efficacy to remove selected environmental health-related pollutants) and measurements of essential design and characterization parameters were taken. The study revealed that the averages of flow rate, biochemical oxygen demand at 5 days (BOD 5 ), chemical oxygen demand (COD), suspended solids (SS) and total solids (TS) of the influent wastewater into the plant (DAF) were 3.45 L/s, 1652.37, 3304.67, 2333.82, and 4396.10 mg/L compared to effluent quality of 560. 37, 1127.33, 172.33, and 1866.67 mg/L for BOD 5 , COD, SS, and TS, respectively. The pH of the wastewater is being adjusted by addition of lime before the effluent equalization tank and individual efficacies of the system were 66. 09, 65.89, 65.89, 57.54, 8.68, and 94.49% for BOD 5 , COD, SS, TS, DS, and total nitrogen, respectively, with overall efficacy of 38.10%. It was concluded that failure (lower overall efficacy) of the system can be attributed to setting of lime in the oversized equalization tank (50 m 3 instead of 16.82 m 3 per 8 h shift), the lack of application of standardized engineering code and practices (provision of underground tank in the process, lack of complete coagulation processes, coagulation and flocculation units), lack of adequate aeration unit and lack of reliable systems for automatically adjusting dosage of coagulant and flocculant. Although, DAF unit is the centerpiece of a DAF-based system design, there are several other supporting systems important to optimal DAF operation. These observations, coupled with the analysis in this report, demonstrate that the facilities necessary to minimize continuous environmental pollution are lacking. Pollution will become an increasing problem unless pollution preventing codes and standards are developed; incorporated into government regulations and the regulations are enforced.

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The study was carried out to investigate the different groundwater resources and to generate the temporal differences over the different seasons in Ilesa West Local Government, Osun State, Nigeria. The LGA has not been provided with municipal pipe-borne water supply for over 30 years, hence they are exclusively using groundwater in form of boreholes, dugwells and springs. The physico- chemical and heavy metal parameters were determined over a period of one year covering the rainy and dry seasons. A total of 69 drinking water points which comprises of 63 dugwells, 5 boreholes and 1 spring were used for the study and they were selected to represent the built-up part of the entire study area adequately. Parameters analysed were pH, electrical conductivity (EC), temperature, total dissolved solids (TDS), chloride, sulphate, nitrate, sodium, potassium (K), calcium, magnesium, hardness, alkalinity, bicarbonate using standard methods. Analysis of heavy metals (Fe, Cr) was carried out with atomic absorption spectrophotometer (AAS) and microbiological analysis was conducted using most probable number (MPN) of counting coliforms. The data generated were subjected to descriptive statistics and line graph. The analysis of the different groundwater resources revealed a good water quality but the values of pH, TDS, EC, K, were higher than the permissible range. The concentration of Fe and Cr is very high and could constitute some health hazards in some sources. The temporal variation of the water quality parameters did not follow any definite trend but the pH, NO3, TDS, HCO3, SO4, Fe, Cr were highest in the dry months of April and December, while Ca, Mg, K, Na, hardness, and alkalinity were highest in the rainy months of June and August. The percentage of microbial distribution was highest in the months of June in the boreholes and the spring but the distribution in the dugwells was entirely different. The water from the boreholes and dugwells were generally soft and should be checked for plumbo-solvency. It is recommended that a routine monitoring of all the sources should be carried out and a treatment that will reduce the heavy metals concentrations be enforced. Keywords: Groundwater resources, physico-chemical parameters, temporal variations, dugwells, boreholes and spring.

Abstract. The inherent havoc caused by scarcity of potable water and transmission of water-borne diseases in some parts of Nigeria have created a public health concern. This study seeks to investigate water purification of four different water samples (namely: water from flowing river; freshly dug well or groundwater; rainwater from the rooftop; and heavily polluted dirty water) consumed by the people in the local community using solar desalination method. A single basin solar still was constructed and experimental studies were carried out to determine the influence of solar insolation and temperature variations on the yield of the distillate. The quality of the distillate was tested by measuring the total dissolved solid (TDS) and electrical conductivity. These were compared to World Health Organization (WHO) standard for drinkable water. These parameters were measured for each water sample before and after desalination to determine the efficiency of the solar still. Results showed a wide gap between the values of TDS and EC before and after desalination of the water samples. The values obtained were in accordance with the requirement of World Health Organization for quality drinkable water. The water becomes clear and less turbid after desalination.

This study examined the spatial and temporal variation of dissolved oxygen (DO) concentration in Asoro stream, the self-recovery ability of the stream of the effluent discharges with a view to providing a baseline information on quality of water in Asoro stream. DO is a measure of the ability of water to sustain aquatic life, it is important in water pollution control and waste water treatment process control. Samples were collected from fifteen sampling points along the Asoro stream at 500 m intervals over a 5000 m stretch for twelve-months. The DO, Biochemical Oxygen Demand and some other physico-chemical parameters of water were determined using standard methods. The hydrographic characteristics of the stream were; width (0.8 to 5.8 m), depth (0.1 to 0.55 m), discharge (0.30 to 0.52 ms-1), flow rate 0.07 to 0.0.73 m 3 /s. The temporal variation in DO concentration in Asoro stream fluctuated from the first week of sampling to 25th week after with a peak range of concentration (7.46 mg/L to 10.12 mg/L) between 27th week and 39th week of sampling suggesting high level of organic pollution. The mean spatial distribution of DO at each station changed slightly between the point of brewery effluent discharge and 5000 m away. Regression analysis showed that there was no significant relationship (P≥ 0.05) between time (weeks) and DO concentration along Asoro stream. The study concluded that release of organic matter from industrial effluent affects the DO and BOD concentrations of Asoro stream.