I.T. Tenebe

Estimation of longitudinal dispersion co-efficient: A review

Abstract Accurate determination of longitudinal dispersion coefficient in rivers or streams is necessary for pollution control and management. This can be achieved through tracer studies and has proven to be a reliable method for measuring pollution spread. However, tracer studies practise which is expensive, time gulping and requiring large labour input have been substituted with empirical approaches thereby reducing the applicability of the dispersion coefficient models generated. This study reviews the various models derived as well as methods associated in the collection of tracer concentration data (measurement) existing in the literature. A sustainable approach to this study was identified and research needs were also listed.

Fluoride contamination in groundwater sources in Southwestern Nigeria: Assessment using multivariate statistical approach and human health risk

The present study investigated the ionic and fluoride concentrations in tap water and its associated health risk to local dwellers of Ogun State (Abeokuta south), Nigeria. 63 samples were collected from twenty-one different locations. Results obtained revealed the mean concentration of fluoride (F-) as 1.23 mg/L. Other water quality parameters such as total dissolved solids (TDS), electrical conductivity (EC), F-, Fe2+, and SO42- surpassed the WHO guidance for drinking water. Strong positive correlation was observed between F- and TDS; F- and pH; TDS and EC; TDS and Mg2+; TDS and SO42-; TDS and HCO3-; EC and HCO3-; EC and SO42-; Na+ and Cl-; SO42- and Cl-. In addition, Empirical Bayesian Kriging (EBK) model was employed to spatially distribute the concentration of the analyzed elements within the study region. The chronic daily dose (CDD) and hazard quotient (HQ) were also used to evaluate the health risk associated with F-, considering dermal and ingestion as pathways. The results revealed that the associated HQ for infants between the age range of 6-12months within about 91% of the study region surpassed the accepted HQ limit. However, the HQ for age categories 11-16years; >65years; 18-21years; 21years; 16-18years within 95.2%, 90.5%, 80.95% and 100% of the study location were less than 1. Conclusively, the HQ values obtained in this study should serve as a baseline information for water management authorities, policymakers and the society at large towards addressing these pollution issues.

Prevalence of heavy metals and computation of its associated risk in surface water consumed in Ado-Odo Ota, South-West Nigeria

ABSTRACT Heavy metal contamination levels, their potential sources and associated health risk of River Balogun – a major source of water for daily domestic activities–were investigated using statistical techniques and some health risk indices. To achieve this, 51 samples from 17 stations (STs) along the river were collected in December 2016 and analyzed for the presence of Lead (Pb), Zinc (Zn), Nickel (Ni), Arsenic (As), and Copper (Cu). The results of the study revealed the presence of As, Ni, and Pb concentration levels exceeding or equal to World Health Organization standards. In addition, the application of both methods used revealed that low pH values measured from the river could emanate from leachate of agrochemicals and carbonic acid from decayed plants while high Nickel and Arsenic concentrations were from the overapplication of fertilizers used in farms surrounding the river and found their way into the river after precipitation. Health risk assessment showed that all the water sampled at different STs would pose a serious threat to the health of children and adults overtime especially due to elevated arsenic concentration measured in all STs.

ASSESSMENT OF DOSE INTAKE OF TOXIC ELEMENTS IN GROUNDWATER SAMPLES FROM ABUJA, NORTH CENTRAL NIGERIA

This study measured the concentrations of toxic carcinogenic and non-carcinogenic elements present in groundwater using Inductively Coupled-Plasma Mass Spectrometry (ICP-MS). The concentration values obtained were used to calculate the life average daily dose (LADD) exposure of the people whom rely on groundwater for consumption in Abuja, Nigeria. The highest LADD for the carcinogenic toxic element chromium (Cr) was 2.7 x 10-5 μg kg‒1 day‒1, whereas it was 3.3 x 10-4 μg kg‒1 day‒1 for the non-carcinogenic toxic element lead (Pb), identified in water samples collected by the Water Board. These LADD magnitudes of 10-5 and 10-4 for both carcinogenic and noncarcinogenic toxic elements in groundwater are far below the International Reference Dose according to the United States Environmental Protection Agency (USEPA) in 2008, which has a value of 10-1. The low magnitudes found in water samples may not pose significant health risks to the local population. The relevant authorities should, therefore, continue to monitor the impact of human activities on metal pollution in this area and take effective measures to control contamination of the public water supply

LIFE AVERAGE DAILY DOSE OF RADIUM-226 ON SOME WATER SAMPLES COLLECTED AT GIRI AND KUJE AREA OF ABUJA, NORTH-CENTRAL NIGERIA

226Ra concentrations were studied to represent the radiological risk of groundwater of the Giri and Kuje areas of Abuja, North-Central Nigeria. Two borehole water samples were collected from the Giri and Kuje areas of Abuja with a hand-dug well and Abuja Water Board as control. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to measure the concentrations of radionuclide of 226Ra exposed to the dwellers. The activity concentrations of 226R in groundwater supplies for drinking and domestic purposes ranges from 443

A laboratory assessment of the effect of varying roughness on dissolved oxygen using error correction method

Abstract Dissolved Oxygen (DO) is an important parameter to be monitored as far as water quality of rivers and streams are concerned. On the other hand, in rivers and streams, varying roughness occurs naturally but their contributions to DO availability is yet unknown. This paper examines the effects of varying roughness of different sizes and arrangement patterns on DO and also reveals how Error Correction Methodology as a modelling technique can be applied in river studies rather than using the traditional ordinary least square method with velocity (V), Froude number (Fr), roughness coefficient (K) and dispersion coefficient (d) captured as explanatory variables. The findings of this study revealed that roughness coefficient (K) had no effect on DO i.e. negative relationship with coefficient value of −0.796, with corresponding t-statistics (t = 0.615) suggesting its non-significance. In addition, Froude number (Fr) and dispersion coefficient (d) also showed negative relationships respectively (−77.71 and −2.039) with DO but with sharp significance as revealed by the corresponding t-ratio (t-ratio = −2.75 and −4.08). Thus, the study suggests that dispersion coefficient or its dimensionless number as a variable is important and should be included in the modelling, otherwise, the spread of pollutants (BOD) in the transverse and vertical directions rather than their single centre point values are essential to improve the outcome of DO and reaeration coefficient (k 2) modelling.

QUALITY ASSESSMENT OF A UNIVERSITY CAMPUS WASTEWATER RESOURCE

Vast volumes of freshwater can be conserved if the practice of re-using wastewater is encouraged. In this study, the quality of wastewater from the Covenant University campus was assessed to determine its suitability for landscape irrigation purposes. The university uses a constructed wetland (CW) method in treating both its black-water and grey-water (wastewater). An estimated 874,081 litres/day of wastewater was generated and treated as of 2013, with nearly all of this volume discharged without being re-used. To assess the suitability of the wastewater for reuse, duplicate grab samples of treated effluent from the CW and from the grey water outlet were assessed for physical parameters such as pH, Temperature, Total Dissolved Solid (TDS), Salinity, Conductivity were analysed using handheld Hanna multi-meter instrument (model HI2040). Also, chemical parameters such as Nitrate, Nitrite, Lead, Nickel, Cadmium, Zinc and Copper were tested using Palintest photometer (model 8000). Moreover, total coliform was checked, using standard laboratory methods. Results indicated that none of the tested parameters exceeded the specified limits by Food and Agriculture Organization (FAO) of United Nations and Environmental Protection Agency (EPA) standards for wastewater reuse. Thus, the treated wastewater in Covenant University was found to be a valuable resource for multiple purposes that can add value other than outright discharge. Thus, it was recommended that appropriate infrastructure be put in place to harness and reuse treated wastewater coming from Covenant University.

EXPERIMENTAL INVESTIGATION OF COPPER REMOVAL FROM AQUEOUS SOLUTION USING MUSA PARADISIACA AS A NOVEL ADSORBENT

The adoption of agricultural waste materials in the removal of heavy metals from contaminated waters has gained more recognition in recent times. This study capitalizes on the production of adsorbents from one of the predominant agricultural waste materials (Plantain Peel) in Ado-Odo Ota, to access its metal-removal efficiency. This work investigated Cu2+ adsorption using activated carbon processed from chemically modified unripe plantain (Musa paradisiaca) peel. Adsorption studies were performed using batch experiments wherewith the influence of pH of the solution, initial concentration, temperature and contact time have been cross-examined. The results displayed a 99.8% removal efficiency of Cu2+ at pH 7.5, 30°C and 150 mg/L concentration. The equilibrium adsorption capacity of unripe Musa paradisiaca peel has been obtained using linear models of Langmuir and Freundlich isotherms. The result is poised to elucidate the metal retention mechanism as a process involving ion exchange as the divalent metal ion binds to the activated unripe plantain peel.

PREDICTING DEGRADATION WITH BIOCHEMICAL OXYGEN DEMAND IN DISINFECTANT-POLLUTED SEWAGE

Most households frequently make use of disinfectants to annihilate infectious bacteria present in toilets and bathrooms. Unfortunately, some of these bacteria may be required for the degradation of sewage in the septic tank system (STS). This paper investigates how the performance (degradation capacity) of sewage will be affected by the inharmonious addition of disinfectants with biochemical oxygen demand (BOD) as the predictor. With a clean 50-litre container, a sewage sample was collected from a waste stabilization pond situated in a Nigerian Tertiary University, transported to the sanitary laboratory in the Department of Civil Engineering, University of Nigeria, Nsukka, and poured into five 4-litre white containers. Different doses of disinfectants – 0.5 ml, 1 ml, 1.5 ml, 2 ml, and 2.5 ml, were simultaneously added only at the initial day of experimental setup under aerobic conditions, and the pH, dissolved oxygen (DO), disinfectant dose, chemical oxygen demand (COD), and BOD were measured every three days for three weeks. Multivariate analysis was performed on the explanatory variable – pH, DO, disinfectant dosage, and COD – using e-Views 8.0, which revealed that the continuous addition of disinfectants to sewage inhibits its degradation, thereby resulting in increased organic loading within the STS, and may further lead to septic tank failure due to shock loading and a major source of ground water been polluted with emerging contaminants.

Assessment of KOH-activated unripe Musa paradisiaca peel for adsorption of copper from aqueous solution

Abstract Adsorption of copper ions out of aqueous solution by preparing activated carbon from unripe Musa paradisiaca peel (UmpP) with KOH was investigated. Estimation of the adsorption constants was achieved by adopting the Langmuir and Freundlich models. Results revealed that the adsorption process was fast and equilibrium was reached at 55 mins. The adsorption efficiency was highly influenced by the pH of the solution, and the maximum adsorption was attained at pH 7.5. In addition, an increase in adsorption capacity was observed with increase in contact time and initial copper concentration. The adsorption process was explained by both Langmuir and Freundlich models having R2 value of 0.9977 and 0.9959 at 303 K respectively and R2 value of 0.9922 and 0.9904 at 308 K respectively. The maximum adsorption capacity of KOH-modified UmpP at the specified conditions was found to be 9.980 and 9.766 mg/g at 303 and 308 K respectively. Sequel to modelling the kinetic data, the Pseudo-second-order model gave the best fit with R2 = 0.9990 and 0.9977 at 303 and 308 K respectively, indicating that the adsorption process is restricted to chemisorption. KOH-modified UmpP can serve as an economically and environmentally viable sorbent for the removal of copper from contaminated waters.