U. G. Wali

Removal of Heavy Metals from Industrial Wastewater Using Rice Husks

Heavy metals are widely used in textile industries and significant losses occur during the manufacture and processing of textiles, and these lost heavy metals are discharged in the effluent. Adsorption of heavy metals is a new technology for treatment of wastewater containing different types of selected heavy metals. In this study, adsorbents Carbonized Rice Husk (CRH) and Activated Rice Husk (ARH) made out of rice husks, available as agriculture waste, are investigated as viable materials for treatment of Pb, Cd, Cu, and Zn containing industrial wastewater at controlled pH. The results obtained from the batch experiments revealed a relative ability of the rice husk in removing some heavy metals at pH 7. One hand one, the CRH adsorption capacity decreases in the order of Cu > Pb > Zn > Cd in batch adsorption whereas during Rapid Small Scale Column Tests the adsorption capacity decrease as follow Cu> Zn> Pb> Cd. On the other hand, ARH adsorption capacity performance is similar to CRH. However, during Rapid Small Scale Column Tests the adsorption capacity decreases in the order Zn>Cu>Pb>Cd. The kinetic removal in batch experiment shows that the net uptake of Pb, Cd, Cu, Zn was 54.3%, 8.24%, 51.4% and 56.7%, respectively whereas using CRH, while it varied as 74.04%, 43.4%, 70.08% and 77.2% for the same dosages of ARH. Therefore, it is concluded that as regards to CRH, ARH demonstrated higher potential to remove relatively all selected heavy metals.

Assessment of Water Pollution Levels in the Nyabugogo Catchment, Rwanda

This study aims to develop a comprehensive system of pollution monitoring and control in the Nyabugogo catchment of Rwanda, which also includes the capital city, Kigali, through locating and highlighting pollution and its sources. Pollution hotspots were identified, covering areas of both anthropogenic and natural pollution. The study focused on water quality assessment especially the identification of the critical points of pollution (hotspots), by measuring selected physico-chemical parameters in the Nyabugogo River system. An extensive monthly water quality monitoring study was conducted from October 2008 to May 2009 and covered nutrients, organic and heavy metal pollutants. The parameters covered are Ammonium-Nitrogen (NH4 + -N), Nitric-Nitrogen (NO2 — N), Nitrate-Nitrogen (NO3 — N), Sulphates (SO4), Phosphates (PO4-P), Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD5), Dissolved Oxygen (DO), Total Dissolved Solids (TDS), Chromium (Cr), Iron (Fe), Lead (Pb), Manganese (Mn), Zinc (Zn), Conductivity (EC), pH, and Turbidity. The samples were collected, preserved and analyzed in the laboratory using standard methods whilst TDS, conductivity, turbidity and pH were measured in the field using HACH field kits. The water quality study revealed that both urbanized and rural sub-catchments have serious but different types of pollution. For example, the water from rural areas is heavily contaminated with nutrients, suspended sediments (due to a lot of erosion upstream) and organic materials whilst from urban areas the predominant pollutants are heavy metals and some nutrients. It was therefore concluded that the Nyabugogo River system is very heavily polluted and urgent action to control both rural and urban pollution is required. Further studies are required to isolate and quantify the sources of this pollution.

Modelling the Impact of Land Use Changes on Sediment Loading Into Lake Victoria Using SWAT Model: A Case of Simiyu Catchment Tanzania

This study aimed at characterising the land use in the Simiyu catchment of Lake Victoria and using land-uses of 1975 and 2006 and comparing the relative impact of land-use change on sediment loading into the Lake. Remote sens- ing using the package ILIWIS 3.0. was used to identify and characterize the land-use while Soil and Water Assessment Tool (SWAT) was used to quantify sediment loading from the 1975 and 2006 land-use scenarios. The results of this study indicate that there was an expansion of agricultural land from 19.33% to 73.43% of the catchment at an annual change rate of 2.9%. Furthermore, the land-use of 1975-yielded less sediment loading compared to that of 2006. Model simulation at the catchment outlet for sediment reported a total yield of 98,467 tons/yr while the actual measured sediment loading had the value of 2,075,114 tons/yr. Hence, the model underestimated sediment yield in the catchment. With good model perform- ance, developing management plans to control sediment loading into Lake Victoria can be achieved using the SWAT model.

Modelling of Non-Point Source Pollution Around Lake Victoria Using SWAT Model: A Case of Simiyu Catchment Tanzania

Pollutant loading in Lake Victoria is resulting from a wide range of anthropogenic activities. This study fo- cused on Non-Point Sources (NPS) of pollution and it was carried out to identify and characterize land-use activities and to quantify the sediment and nutrient loads (nitrogen and phosphorus). The study was conducted in Simiyu catchment of Lake Victoria using land-use data of 1975 and 2006 and comparing the relative impact of land-use change on sediment and nutrient load (P and N) into the lake. Possible best management practices were also identified for those sub-basins with the highest pollution yield. Remote sensing using the package ILIWIS 3.0 was used to identify and characterize the land-use and the Soil and Water Assessment Tool (SWAT) model was used to quantify sediment and nutrient load from these two different land-use scenarios. Land use classification according to the SWAT model shows that Agricultural Land-Generic (AGRL) contributes about 73.43%, Range-brush (RNGB) contributes 24.42%, Pasture (PAST), 2.10% Sa- vanna (SAVA) 0.03% and Water (WATR) 0.02% of the total catchment area of Simiyu. It was also found out that there was an expansion of agricultural land from covering 19.33% of the catchment to 73.43% at an annual change rate of 2.9%. However, average Nitrate load was higher for 1975 than 2006. The P load of 1975 was less compared to that in 2006. Model simulation at the catchment outlet for N gave 77.2 kg/km 2 .yr while observed values were 146 kg/km 2 .yr, simulated P was 47 kg/km 2 .yr while observed was 164 kg/km 2 .yr. Hence, the model underestimated nutrient yield in the catchment. Therefore, the applicability of the SWAT modelling tool in studying NPS pollution yields poor model per- formance due to the scantiness of data used for model calibration. More rigorous data campaigns have to be carried out along the two rivers of Duma and Simiyu for purposes of gaining enough information for model calibration and valida- tion. With good model performance, developing management plans to control NPS pollution around Lake Victoria could be achieved using the SWAT model.

Development of Best Management Practices for Controlling the Non-PointSources of Pollution Around Lake Victoria Using SWAT Model: A Case ofSimiyu Catchment Tanzania

Recent studies carried out in Lake Victoria Basin have identified major sources of Non-Point Source (NPS) of pollution in the Simiyu catchment of Lake Victoria using land-uses of 1975 and 2006 and compared the relative impact of land-use change on sediment and nutrient load (P and N) into the Lake. The main aim of this study was to identify and develop Best Management Practices to control NPS pollution in the Simiyu Catchment. The SWAT model was used to stimulate and assess the Best Management Practices Scenario for the catchment. The catchment was divided into seven (7) sub-basins. The results show that there was no intensive use of artifical fertilisers in the catchment and manure is the major type of fertiliser in use. Simulation was done for the period 2000 to 2005. High nutrient concentration was observed in Sub-basin 6; 0.558-0.779 kgN/ha/yr than in Sub-basin 7; 0.018-0.115 kgN/ha/yr, despite the larger area of coverage by the latter. This is also irrespective of the fact that Sub-basin 7 covers a larger area, 3,426.52 km 2 compared to Sub-basin 6 (72.97 km 2 ) and Sub-basin 4 (618.16 km 2 ). Relatively, considering their size, Sub-basin 6 produces higher pollution than Sub-basin 7. It was also observed that the sediment yield from the whole catchment reduced from 81,222 ton/yr to 98,400ton/yr.It was observed that to control the NPS pollution problem, Best Management Practices like reduced manure application rate, tillage and contour yielded a decrease of 1.4% in N load and 1.57% in sediment load. As a result, it was concluded that the SWAT modelling tool can be used in developing Best Management Practices because pollutant proc- esses per sub-catchment had been fully understood. With good model performance, developing management strategies to control NPS pollution around Lake Victoria can be achieved using the SWAT model. The BMPs have been devised de- pending on the sub-basin, which has a big collective reduction and control in NPS pollution in the whole catchment.

Distribution of Heavy Metals in Lake Muhazi, Rwanda

The pollution of lakes is mainly conceived in terms of nutrient levels and eutrophication with the consequent development of algal blooms and fish kills. However, heavy metals are increasingly becoming prominent especially for water bodies closer to urban and mining areas. This study focuses on heavy metal pollution in lakes using a case study of Lake Muhazi in Rwanda. The study characterized the horizontal and vertical distribution of heavy metals in the Lake, with the research conducted from July to October 2007. The parameters studied are cadmium, chromium, copper, iron, lead, manganese, zinc, pH and temperature. The samples were collected at different depths in the Lake using a Van Dorn Bottle water sampler, and were analyzed using standard methods. The temperature and pH were measured in the field us- ing HACH field testing kits. The findings indicated that the mean concentration of Zn was 0.041±0.045 mg/L, Cd 0.026±0.029 mg/L, Pb 0.292±0.442 mg/L, Fe 0.756±0.734 mg/L, and Mn 0.340±0.336 mg/L. Chromium and copper were not detected in the water samples. The findings indicate that the concentrations of Cadmium, Iron and Lead far exceeded the recommended levels for aquatic life at all sampling points. The high levels of heavy metals are attributed to the ripar- ian landuse practices such as uncontrolled agriculture, urban runoff and mining activities around the Lake. It is recom- mended that a detailed study of the catchment be carried out to identify and isolate the main sources of heavy metals in the Lake so that appropriate control measures could be developed.

Modeling Diffusive Flux of Non Point Source Pollutants in Lake Victoria: A Comparison Study of Fick's Law and the Fokker-Planck Law

Mathematical models have the potential to conceptually quantify, link and simulate the interactive processes of nature. In this study 68 samples were collected at Gaba landing site in Uganda during a rainy season and were analyzed for nutrients, namely, Ammonia, Nitrite, Nitrate, and Phosphate. In addition, portable meters were used to measure Total Dissolved Solids (TDS) and Dissolved Oxygen (DO) instantaneously at point of sample collection. Within the lake, sam- ples were taken at for horizontal transects of 10 metres (m) interval over a distance of 50 m from the shore where surface runoff was released. At each 10 m sampling point, three samples were drawn at vertical distances of 0.5 m, 1.0 m and 1.5 m from water surface using a hand pump with graduated delivery pipe. This paper presents the results obtained from the application of two alternative expressions, ficks law and Fokker-Planck law to gain insight into the pollutants diffusive flux patterns within the lake. We conclude that in general the Fokker-Planck model should be given preference, in model- ling Ammonia and Phosphate flux profiles while Fickian model should be deployed in modelling DO, TDS, Nitrites and Nitrates.

Modelling of Nonpoint Source Pollution in Akagera Transboundary River in Rwanda

In this paper, we to assess the level of pollution in the Akagera Transboundary River. The followings parame- ters namely NH4-N, NO3-N, PO4-P, Total Dissolved Solids (TDS), conductivity, pH, Temperature, and Turbidity were identified and quantified. Sampling was conducted a monthly basis from March 2008 to February 2009 at eleven sampling points on the Akagera River system. The landuse and land form characteristics were studied using satellite imagery and ground truthing. From this pollution reduction factors in terms of kg/ha.yr of pollution load were developed for each lan- duse type and used for developing the model. Rainfall and river flow data were obtained from gauging stations in and around the river. Water quality parameters particularly values of NH3-N changed from 0 to 2.36 mg/l, NO3-N from 1.8 mg/l to 314.4 mg/l and PO4-P from 0.02 mg/l to 19.3 mg/l. Field observations supported with computed export coefficient values showed that bare soils are the most influencing negative factor on water quality in the Akagera River.

Qualitative Determination of Methane Gas at Selected Sites in Kampala City, Uganda

Solid Waste (WS) sorting at primary source, collection, transportation and disposal are a challenge in many cities in the developing world. Experiences from the developed world indicate that planning, education, enforcement and resources are needed to effectively manage SW. Poor SW management is responsible for many diseases especially in the developing world. Taking Kampala as a case study, with a population of 1.2 million people, SW is deposed off in public landfills, and open dumps near and/or burnt in residential areas. SW in landfills emit significant amounts of a potent greenhouse gas, methane. Studies from elsewhere have demonstrated that this contributes to the greenhouse effect and global warming. However, most of the developed methods to determine methane gas are expensive and requirement cumbersome sample preparation procedures. More often than not, such equipments are not present in many developing countries. As such data on methane gas emissions in Kampala city and Uganda as a whole are scarce and those that are available are models based on other country estimates A Gas chromatography equipped with a Flame Ionization Detector (GC-FID) method was used to make a qualitative study of methane gas generated from SW in Kampala City so as to in- form the relevant decision makers on the need to take appropriate measures to reduce open environment methane emis- sions at dumping sites.

Heavy Metals Inflow into Lake Muhazi, Rwanda

Most tropical African lakes are facing pollution problems due to the rapid population growth and industrializa- tion in their riparian communities. Lake Muhazi in Rwanda is one of such lakes which has experienced a dramatic decrease in fish production since the eighties, with also reports of low water transparencies and high turbidities. The lakeshores are now being developed for ecotourism and this requires sound environmental management to make the planned activities viable. The purpose of this study was to assess heavy metal pollution in the tributary rivers of Lake Muhazi. The concentration of heavy metals in major tributaries was monitored for the period July to October 2007. The parameters studied are cadmium, chromium, copper, iron, lead, manganese, zinc, pH and temperature. Fourteen sampling stations on the Inflow Rivers and the spillway were monitored fortnightly. The samples collected for heavy metal analysis were preserved and stored in cooler boxes and analyzed in the laboratory using Standard Methods. Temperature and pH were measured in the field using HACH field testing kits. The concentration (mean ± standard deviation) of Zn was found to be 0.040±0.103 mg/L, Cd 0.031±0.007 mg/L, Pb 0.487±0.452 mg/L, Fe 7.53±13.34 mg/L, Mn 1.01±1.31 mg/L, chromium 0 mg/L and copper 0 mg/L. The concentrations of measured parameters deviate much from the recommended ones thus posing serious problems to aquatic life. It has also been shown that the high metal concentration levels in Lake Muhazi are related to landuse activities in the catchment. It is thus recommended that farming practices and erosion be controlled in the catchment to contain pollutant discharges into the lake. Lead is the main anthropogenic pollutant which has been found in the watershed of Lake Muhazi.