Browsing by Author "Ojok, Walter"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Assessment of Seasonal Variation in Water Quality in River Rwizi Using Multivariate Statistical Techniques, Mbarara Municipality, Uganda
    (Journal of Water Resource and Protection, 2017) Ojok, Walter; Wasswa, John; Ntambi, Emmanuel
    Assessment of seasonal variations in surface water quality characteristics is an essential aspect for evaluating water pollution due to both natural and anthropogenic influences on water resources. In this study, temporal variations of water quality in river Rwizi section within Mbarara municipality, Uganda, were assessed using multivariate statistical methods. This river section is a major source of water for the inhabitants of Mbarara municipality. Water samples from five sites were analyzed for physicochemical parameters such as pH, EC, turbidity, temperature, TSS, TDS, alkalinity, salinity, colour, NH3-N, 24 SO − , total hardness, BOD, COD, DO, Ca, Mg, Fe, and Mn. About 50% of sites recorded colour above 800 Pt Co, 60% of sites recorded turbidity above maximum permissible limit of 100 mg/l, attributable to erosion and mineral matter. pH for dry season ranged between 6.5 and 8.5 whereas for rainy season was below 6.0. All study sites recorded total Fe above 0.3 mg/l and Mn below 0.5 mg/l, attributable to chemical weathering of host rock materials as well as from industrial effluent. About 60% of sites recorded COD above 100 mg/l, 40% and 80% of study sites showed BOD above 50 mg/l in dry and rainy seasons respectively. Hardness ranged between 50 and 100 mg/l indicating that the water is moderately soft. Colour, turbidity, alkalinity, TSS, TDS, salinity, pH, hardness, Fe, Mn, NH3-N, BOD, COD, and DO were higher in rainy season, as a result of erosion, discharge of domestic and industrial waste. Mg, Ca, and 2 4 SO − were higher during dry season due to high evaporation of water from the river. PCA/FA determined that 81.2% of the total variance was explained by the first factor for the dry season and 69.2% for rain season. These results revealed that water pollution resulted primarily from domestic waste water, agricultural runoff and industrial effluents.
  • Thumbnail Image
    Item
    Hydrochemistry and fluoride contamination in Ndali-Kasenda crater lakes, Albertine Graben: Assessment based on multivariate statistical approach and human health risk
    (Groundwater for Sustainable Development, 2021) Ojok, Walter; Wanasolo, William; Wasswa, John; Bolender, James; Ntambi, Emmanuel
    Hydrochemistry of crater lakes (n = 15) in the Ndali-Kasenda cluster was deciphered using standard methods of the American Public Health Association to understand the major ion chemistry; spatial distribution, occurrence, and non-carcinogenic health risks due to exposure to fluoride levels in the lakes in Ndali- Kasenda cluster, Albertine Graben. Numerous economic activities take place in and around the crater lakes which serve as major sources of domestic water whose origin of potential contaminants is ambiguous. In this study, WHO (2017) regulatory limit exceedance included F􀀀 , pH, Ca2+, Fe2+, Mn2+, and TDS. A strong positive correlation was observed between F􀀀 and TDS; F􀀀 and pH; F􀀀 and EC; F􀀀 and HCO3􀀀 . However, concerning hydrogeochemical signature, the lakes are mainly of Ca–HCO3 type and low in Na–K–HCO3 type due to rock water interaction in the geology of the area. Principal component analysis (PCA) performed on Ndali-Kasenda hydrogeochemical data resulted in six principal components (PCs) explaining 88.6% of the total variance. The PCs represented the primary processes that control the crater lake hydrogeochemistry in the Ndali-Kasenda area which include; weathering of rocks reactions, ion exchange, and evaporation processes. The hazard quotient (HQ) for noncarcinogenic health risks associated with exposure to Ndali- Kasenda fluoride levels via ingestion revealed that HQ for infants surpassed the acceptable HQ limit for all the lakes studied, while 86.67 % of the sampled lakes exceeded the HQ value for children via ingestion. Based on the hydrogeochemical parameters analyzed, aside from L. Murigamire and L. Wankenzi, water from the other studied lakes is chemically not acceptable for drinking purposes. An urgent need to take ameliorative action in this area to protect the inhabitants from exposure to excess fluoride in drinking water was recommended.
  • Thumbnail Image
    Item
    Mobility of Chromium, Copper and Arsenic in Amended Chromated Copper Arsenate Contaminated Soils
    (Asian Journal of Applied Chemistry Research, 2020) Kiwanuka Nakiguli, Caroline; Ojok, Walter; Omara, Timothy; Wasswa, John; Ntambi, Emmanuel
    The use of copper-based preservatives such as chromated copper arsenate (CCA) and creosote to prolong the life of lumber present environmental concerns because they contain heavy metals and polycyclic aromatic hydrocarbons which are toxic to humans. The aim of this study was to investigate the effects of sewage sludge biosolid amendment on the distribution and mobility of chromium, copper and arsenic in chromated copper arsenate contaminated soils subjected to phytoremediation using maize (Zea mays L.). Place and Duration of the Study: Random composite soil samples from Kitetika wood factory, Wakiso, Uganda and sewage sludge biosolid from National Water and Sewerage Corporation plant in Bugolobi, Kampala, Uganda were collected and prepared. Maize grains were obtained from FICA Seeds Limited (Uganda). The pot experiments and analysis of samples were done at Mbarara University of Science and Technology (Mbarara) and Directorate of Government Analytical Laboratory, Kampala (Uganda), respectively. Methodology: The fresh CCA contaminated soils and sewage sludge biosolid were analyzed for physicochemical parameters and heavy metals (chromium, copper and arsenic). Sewage sludge biosolid was added to 1 kg of the contaminated soils at 5-25% (w/w) in 2 L plastic containers, watered and maintained at 25 ℃ for 14 days to stabilize. Controls were set up with unamended soils. Thereafter, maize was planted in the potted soils for 40 days. The concentrations of the trace metals in the soils were determined after 20 and 40 days of maize growth by atomic absorption spectroscopy. Results: The concentrations of chromium, copper and arsenic in fresh CCA contaminated soils were 365.8 ± 6.18 mg/kg, 109.72 ± 14.04 mg/kg and 28.22 ± 3.8 mg/kg, respectively. Basing on mobility factor, bioavailability of the trace metals followed the chemical sequence copper (8.9%) < chromium (17.1%) < arsenic (30.2%). Conclusion: The maize variety experimented could be used to phytoextract or phytostabilize the trace metals in the CCA contaminated soils without or with 5-25% amendment. Amendment with sewage sludge biosolid improved the phytoremediation potential of maize. Arsenic was the most mobile and bioavailable metal in CCA contaminated soils. Further studies should use other local maize varieties such as Longe series.
  • Thumbnail Image
    Item
    Synthesis and characterization of hematite biocomposite using cassava starch template for aqueous phase removal of fluoride
    (Carbohydrate Polymer Technologies and Applications, 2022) Ojok, Walter; Ntambi, Emmanuel; Bolender, James; Wasswa, John; Wanasolo, William; Moodley, Brenda
    In this study, facile synthesis of α-Fe2O3 biocomposite was mediated by cassava starch as a soft template. Batch mode evaluated its sorption behavior for fluoride removal from aqueous media. Characterization studies using analytical techniques confirmed the existence of porous α- Fe2O3 biocomposite with heterogeneous surfaces having a varied affinity for fluoride. The sorption process was optimized using central composite design (CCD) in response surface methodology (RSM) with a good model prediction (R2 = 0.9066). A study of the interaction effect showed the synergy of process variables on fluoride removal with the result’s intensity indicated by the nature of contour plot curvature. Based on the RSM optimization, an optimum fluoride removal efficiency of 85.26 % can be achieved at an initial fluoride concentration of 55 mg/L, α- Fe2O3 biocomposite dose of 0.55 g, pH of 7.5, and contact time of 95 min. Sorption equilibrium data were well modeled by Freundlich isotherm (0.9916), indicating multilayer sorption on a heterogeneous surface of the sorbent with a varied affinity for fluoride. Presence of co-existing anions reduced fluoride removal efficiency in the order PO43􀀀 > HCO3􀀀 > SO4 2 􀀀 > NO3􀀀 > CƖ􀀀 . At the same time, its kinetics was better modeled by pseudo-second-order kinetics (R2 = 0.9764), showing that the sorption process is rate-limiting. The sorption thermodynamics study showed that the process was spontaneous, exothermic, and entropy-driven physisorption. Hence, the results signify that the green synthesized α- Fe2O3 biocomposite could be a potential sorbent for sustainable defluoridation.