Water Pollution

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Browsing Water Pollution by Subject "Jomo Kenyatta University of Agriculture and Technology"

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  • Publication
    Publication
    Assessing the Impact of land-use types on the groundwater quality: a case study of Mid River Njoro Catchment, Kenya
    (acque sotterranee, 2020-12-22) Rendilicha, Halake; Home, Patrick; Raude, James; M'Erimba, Charles; Muthoka, Stellamaris
    The study assessed the impact of land-use types on the groundwater quality of the mid River Njoro catchment, Kenya. Groundwater samples were collected from eight boreholes between the period of October 2017 to February 2018 and analyzed for pH, temperature, electrical conductivity, dissolved oxygen, nitrate, ammonium, and total phosphorus. These parameters were used to calculate the Groundwater Quality Index (GQI) value of the study area. The concentration maps (“primary maps I”) were constructed using Kriging interpolation of ArcGIS software from the seven groundwater quality parameters. The “primary maps I” were standardized with the KEBS and WHO standards to the “primary maps II” for ease of integration into a GIS environment. The “primary maps II” were then rated and weighted using a polynomial function to generate “rank maps” before calculating the GQI using spatial analyst tools of ArcGIS software. The land use map was prepared from a high-resolution Google earth satellite imagery of 2015. The mean GQI values for the different land use polygons were calculated and compared using GIS techniques. The GQI ranged from 68.38 to 70.92, indicating a high groundwater quality of mid River Njoro catchment. The major land-use types identified include settlement area, forest cover, agricultural land and mixed area. The agricultural land dominated the study area, followed by settlement area, forest cover and finally mixed area. The mean GQI value in each land use type varied minimally and this could be because of the diffuse nature of the land use types of the study area. Settlement area had low GQI, followed by agricultural land, mixed area and the forest cover had the highest mean GQI value, which corresponds to good quality of groundwater. Even though the variation is insignificant in this particular study, it somehow indicates the adverse effects of different land use on the quality of groundwater.
  • Publication
    Publication
    Simulation of the Hydraulics and Treatment Performance of Horizontal Subsurface Flow Constructed Wetland Treating Greywater
    (Science Publishing Group, 2018-05-10) Raude, James Messo; Mutua, Benedict Mwavu; Kamau, David Ngugi
    Constructed wetlands (CWs) have evolved as some of reliable wastewater treatment technologies. Various types of CWs differ in their main design characteristics and in processes responsible for pollutant removal. Classification of CWS is based on the type of vegetation used and hydrological parameters involved and can thus be classified as free water surface or subsurface flow systems. Further, subsurface flow systems can be classified according to flow direction as vertical or horizontal. This study considers horizontal subsurface flow constructed wetlands (HSFCWs) which introduces the mechanistic, dynamic compartmental model-Constructed Wetlands 2D (CW2D). The model has successfully been utilized to evaluate the performance of vertical flow constructed wetlands and is being tested on HFCWs. An outdoor pilot scale HSFCW system was established in Nakuru, Kenya. CW2D was calibrated, validated and used to simulate hydraulic performance of HSFCW system. The model was used in predicting effluent concentrations of the main greywater pollutants. In general, the results obtained showed a good match with the measured data. CW2D is an effective tool for evaluating the performance of CWs and can provide insights in treatment problems at an existing CW. The same methodology can be used to optimize existing systems.
  • Publication
    Publication
    The Effect of Groundwater Recharge and Abstraction on Groundwater Quality in Nairobi Aquifer System
    (International Journal of Engineering Trends and Technology, 2022) Mwangi, Rael Mongu2019ina Nyakundi, Maurice Nyadawa, John
    Using standard procedures, the study analysed water samples from 100 boreholes from Nairobi Aquifer System (NAS) for selected water quality parameters. Data from eleven monitoring boreholes from 2013-2019 was obtained from Water Resources Authority (WRA). The parameters were weighted, and their concentrations were used to develop Water Quality Indices (WQI). Abstraction data was obtained from WRA while recharge was estimated using SWAT Model. A Multiple regression model for WQI, abstraction and recharge variables was developed, and maps were created. Results showed the highest WQI of 0.4001 when recharge was 666,980.16 m3/year and abstraction 54,963,200 m3/year, and lowest WQI of 0.2861 when recharge stood at 346,483.20 m3/year and abstraction 41,586,600 m3/year. A strong correlation between abstraction, recharge, and WQI of R2 0.86was observed. Areas with high recharge and low abstraction exhibited a low WQI of 0.2, while areas with high abstraction rates and low recharge showed relatively high WQI of 0.6. Therefore, it was concluded that water quality improved with decreased abstraction and recharge and deteriorated with increased abstraction and reduced recharge. It was recommended that abstraction be regulated in line with recharge rates and recharge be improved to maintain high water quality suitable for human consumption.