Biosystems Engineering

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Development and appraisal of hand wash-wastewater treatment system for water recycling as a resilient response to COVID-19
(Elsevier, 2021-07-28) Olupot, Peter Wilberforce; Menya, Emmanuel; Jjagwe, Joseph; Wakatuntu, Joel; Kavuma, Tonny; Wabwire, Andrew; Kavuma, Steven; Okodi Mcmondo, Samuel; Nabuuma, Betty; Mpagi Kalibbala, Herbert
In this work, results from characterization of handwashing wastewater from selected stations in Kampala City, Uganda, revealed that handwashing wastewater did not meet permissible international standards for wastewater discharge to the environment. The ratio of BOD5 to COD of ˂ 0.5 implied that handwashing wastewater was not amenable to biological treatment processes. Turbidity of ˃ 50 NTU pointed to the need for a roughing filter prior to slow sand filtration. Subsequently, a handwashing wastewater treatment system consisting of selected particle sizes of silica sand, zeolite, and granular activated carbon as filtration and/or adsorption media was developed and assessed for performance towards amelioration of the physicochemical and biological parameters of the handwashing wastewater. Treated water from the developed wastewater treatment system exhibited turbidity of 5 NTU, true color of 10 Pt-Co, apparent color of 6 Pt-Co, and TSS of 9 mgL-1, translating to removal efficiencies of up to 98.5%, 98.1%, 99.7%, and 96.9%, respectively. The residual total coliforms and E. coli of 1395 and 1180 CFU(100 mL)-1 respectively, were totally eliminated upon disinfection with 0.5 mL NaOCl (3.5% wt/ vol) per liter of treated wastewater. The treated water was thus suitable for recycling for handwashing purposes as opposed to letting handwashing wastewater merely go down the drain. This approach provides a resilient response to COVID-19, where communities faced with water scarcity can treat and recycle handwashing wastewater at the point of washing. It thus enables more people to have the opportunity to practice handwashing, abating the high risks of infection, which could otherwise arise.
Effect of alkaline pretreatment on the thermal behavior and chemical properties of rice husk varieties in relation to activated carbon production
(Springer, 2019-07-19) . Menya, E; Olupot, P. W.; Storz, H.; Lubwama, M.; Kiros, Y.; John, M. J.
Thermal behavior and chemical properties of selected raw and NaOH-pretreated rice husk varieties were investigated. NaOH- pre treatment process involved soaking 5 g rice husk samples in 40 mL of 2%w/v NaOH, shaking (400 rpm) and heating (50 C) for 3 h. NaOH- pretreated samples were water-washed, oven-dried, and milled for use in the determination of their thermal behavior and surface functional groups. Alkaline wash water was also analyzed for sugar components. Thermal decomposition temperatures, degradation rates, and the subsequent mass losses varied from one rice husk variety to another. These thermal properties increased after NaOH pretreatment of the rice husk varieties, reducing their char yields (17.1–20.4% db). These changes mainly had to do with the lignin, hemicellulose, and ash removal from the rice husk varieties, as confirmed by their FTIR analysis, as well as by the sugar composition analysis of their alkaline wash-water. Consequently, the FTIR spectra differed between the raw and NaOH-pretreated rice husk varieties
Effects of Mulching on Soil Hydro-Physical Properties in Kibaale Sub-catchment, South Central Uganda
(Science and Education Publishing, 2015-10-11) Kakaire, Joel; Makokha, George L.; Mwanjalolo, Majaliwa; Mensah, Albert K; Menya, Emmanuel
Mulching is one of the major soil and water conservation measures applied for conserving soil moisture and modifying soil physical and chemical environment. The study aimed at assessing the effect of mulching on soil hydro-physical properties in Kibaale sub-catchment in South Central Uganda. Samples were obtained between 0-20 cm depths and under 0, 5, 10 and 15 cm mulch thickness levels. The experiment involved 3 farmers and 4 treatments of corn residue mulch thicknesses each replicated thrice on each of the farmer sites. The main parameters of study were; bulk density, saturated hydraulic conductivity (Ksat) and water retention. The parameters were determined using core method, constant head method and pressure plates’ method respectively. Laboratory data was statistically analyzed using Analysis of Variance (ANOVA) from Genstat software Edition 4 and the means differentiated using 5 % least significant difference (LSD). The application of mulch significantly improved all the soil hydro-physical properties that were studied (bulk density, Ksat, field capacity, wilting point, porosity, soil organic matter (SOM), mean weight diameter (MWD) after two seasons. The level of improvement was highest with 10 cm mulch thickness while Ksat, porosity and SOM varied significantly (P< 0.05) with mulch thickness. The study recommends the use of 10 cm mulch thickness. This study provides information to stakeholders such as agricultural experts, watershed managers, farmers and policy makers which will help in formulating guidelines on how to incorporate mulching as an effective method for soil and water conservation in the Sub-catchment
Effects of sawdust and adhesive type on the properties of rice husk particleboards
(Elsevier, 2022-11-17) Olupot, Peter Wilberforce; Menya, Emmanuel; Lubwama, Festo; Ssekaluvu, Lawrence; Nabuuma, Betty; Wakatuntu, Joel
This study set out to investigate the effects of adhesive type, rice husk and sawdust proportions on the properties of composite particleboards. Specimens of 200 × 200 × 24 mm were made by blending 500 g of rice husks with each adhesive type at a mass ratio of 1:1. The rest of the specimens of similar dimensions were prepared with addition of sawdust in the range of 10–40 wt%, while maintaining the ratio of biomass particles to adhesive at 1:1. Three commercial synthetic adhesives Fevicol (FV), Ponal (PA) and woodfix (WF) were used. The particle adhesive mixtures were molded into a mat which was subsequently cold pressed at 10 MPa and left to dry in air. Density, water absorption (WA), linear expansion (LE), thickness swelling (TS), modulus of elasticity (MOE), modulus of rupture (MOR) and screw holding capacity of the specimens were evaluated. Adhesives were found to have over 42% solid content, with similar liquid constituents but in varying proportions. FTIR library search for the spectra of FV, PA, and WF revealed correlations of 82.5%, 78.6%, and 50.2%, respectively with polyvinyl acetate. The developed boards had a density of 510–610 kg/m3, MOE 13–26 MPa, TS 9–31%, and LE 3–7%. These properties suit them for furniture boards and soundproofing. The properties improved with the increasing proportion of sawdust. FV and PA-bonded particleboards exhibited higher stability and strengths than WF-bonded particleboards due to higher concentrations of polyvinyl-acetate in the latter. Blending 40 wt% sawdust, 10 wt% rice husk with 50 wt% of either FV or PA showed better prospects.
Experimental evaluation of rice husk ash for applications in geopolymer mortars
(Keai publishing, 2021-02-26) Ogwanga, G.; Olupot, P.W.; Kasedde, H.; Menya, E.; Storz, H.; Kiros, Y.
Rice husks obtained from upland and lowland rice varieties were characterized by the composition and content of ash. Each of the rice husk varieties was fired at temperatures of 600, 800, and 900 °C for a soaking period of 3 h. The resultant rice husk ash was analyzed for oxide composition and crystallinity using X-ray fluorescence and diffraction techniques, respectively. The generated amorphous ash with the highest silica content, together with metakaolin, aggregate, water, and an alkaline activator was employed to formulate geo-polymer mortar prisms according to the standard EN 196–1. Results showed that the content of ash in the varieties ranged from 18.3% to 28.6% dry basis. Out of this, 89 wt%–96 wt% was silica, with amorphous and crystalline forms of silica obtained at 600 °C and 900 °C, respectively, regardless of the rice variety. However, at 800 °C, the silica in the generated ash exhibited both amorphous and crystalline forms. The amorphous ash generated at 600 °C was used in the formulation of geopolymer mortars. The compressive and flexural strength of the formulated mortar after 7 days of curing was 1.5 and 1.3 MPa, respectively. These results reveal the firing protocol to form pozzolanic ash, with potential applications in mortar production.
Factors affecting adoption of mulching in Kibaale sub-catchment, South Central Uganda
(International Journal of Sustainable Agricultural Management and Informatics, 2016) Kakaire, Joel; Mensah, Albert Kobinah; Menya, Emmanuel
Mulching is one of the major soil and water conservation measures applied for conserving soil moisture and modifying soil's physical environment. The study aimed at determining the factors which influence the adoption of mulching in the Kibaale sub-catchment, Uganda. 100 structured questionnaires; key informant interviews and observation were used to obtain the socio-economic and institutional data. To determine the factors affecting the adoption of mulching, descriptive statistics, and factor analysis were used. Chi-square (P ≤ 05) was used to establish the relationship between the identified factors and adoption. Using the chi-square test, the study also identified the Education level of household head, household size, accessibility to farmland, and marital status as the major factors that significantly affected adoption of mulching. The community leaders should ensure that the members attain some level of education and ensure that the land owned by individuals is within their periphery of management and control.
Investigating the effect of different loading densities on selected properties of dried coffee using a GHE dryer
(CIGR Journal, 2023-09) Menya, E.; Komakech, A. J.
Despite coffee being one of the leading cash crops in Uganda contributing 20%-30% of the total export earnings, it is mainly dried on bare earth surfaces hence its drastic decline in quality. A possible alternative solution is the utilization of the greenhouse effect (GHE) solar dryer. This research was aimed at investigating the effect of different loading densities on selected properties of dried coffee using a GHE dryer that was designed and constructed at Makerere University Agricultural Research Institute Kabanyolo (MUARIK). The research involved determining the drying time for the loading densities of 5, 10 and 20 kg m-2 as well as analyzing the coffee quality at the end of the drying period. Three experimental runs were set up in the months of June and July which experienced an average ambient temperature of 23.28 (±2.33)oC and an average dryer temperature of 35.68 (±13.85)oC. The average drying time for the freshly harvested Robusta coffee at 61.3 (±1.36)% wb was 10 days for 5 kg m-2, 11 days for 10 kg m-2 and 12 days for 20 kg m-2. The loading of 20 kg m-2 resulted in an even roast with fair+ for body and flavour, while 5 and 10 kg m-2 loadings resulted in a silver skin roast with fair body and flavour. For this particular research, the loading density of 20 kg m-2 yielded the best results from the coffee quality analysis. The loading densities of 5 kg m-2 and 10 kg m-2 could not yield the best results due to case hardening of the outer surfaces of the coffee beans which compromised the body and flavour of the coffee.
Optimization of pyrolysis conditions for char production from rice husks and its characterization as a precursor for production of activated carbon
(Springer, 2019-03-13) Menya, E.; Olupot, P. W.; Storz, H.; Lubwama, M.; Kiros, Y.; John, M. J.
Response surface methodology was employed to optimize pyrolysis conditions for the production of char with maximum yield, fixed carbon content, and minimum ash content from Uganda’s New Rice for Africa (NERICA) 1 rice husk variety. The aim was to obtain rice husk char with more suitable properties as an activated carbon precursor. Mathematical models were developed to explain the relationships between the experimental responses and the pyrolysis parameters of temperature (400–600 °C), heating rate (10–25 °C min−1), and heating period (60–120 min). The optimized rice husk char was further characterized for elemental and proximate compositions, thermal behaviour, specific surface area, as well as surface functional groups. Results from the analysis of variance (ANOVA) revealed that the quadratic model best fits each of the responses. Pyrolysis temperature had the greatest influence on each of the responses, followed by heating period, and lastly heating rate. Optimum pyrolysis conditions were found to be temperature (406 °C), heating rate (10 °C min−1), and heating period (60 min), resulting in char yield, fixed carbon, and ash contents of 35.26, 55.39, and 35.01% dry basis, respectively. Compared to raw rice husk, the resulting rice husk char was found more suited as activated carbon precursor, due to its enriched carbon content (60.35%) and specific surface area (123.9 m2g−1). Thermogravimetric analysis of the rice husk char revealed that thermal activation temperatures were higher than 400 °C may be required to considerably devolatilize the char, forming a more porous activated carbon.
Optimization of pyrolysis conditions for production of rice husk-based bio-oil as an energy carrier
(Elsevier, 2023-11-09) Wakatuntu, Joel; Olupot, Peter Wilberforce; Jjagwe, Joseph; Menya, Emmanuel; Okure, Mackay
Bio-oil is an eco-friendly energy source with potential to substitute fossil-derived fuels. This study optimized pyrolysis conditions for production of bio-oil from rice husks. Response surface methodology based on central composite design was employed to maximize bio-oil yield and high heating value (HHV) while minimizing water and ash contents. The pyrolysis process conditions were; temperature (400–650 ◦C), heating rate (6000–9750 ◦Ch-1), and holding time (600–1800 s). Analysis of variance revealed that the linear model best fits the responses of bio-oil yield and water content. On the other hand, the quadratic model best fits the responses of HHV and ash content. Pyrolysis temperature had the greatest influence on each of the studied responses, followed by holding time and lastly heating rate. Optimum pyrolysis conditions were found to be; temperature (650 ◦C), heating rate (9750 ◦Ch-1), and holding time (1800 s), leading to bio-oil yield, HHV, water, and ash contents of 38.13%, 23.40 MJ/kg, 18.27%db, and 0.16%db, respectively. These results fall in the range of standard quality values for bio-oil in published literature where >15 MJ/kg, 20–30%, 0.15–0.25% are the recommended ranges for HHV, water, and ash contents, respectively. Results from the FTIR spectroscopy revealed that phenolic compounds contributed the most to bio-oil composition. Phenolic compounds positively influenced the quality of bio-oil due to their high calorific values. Gas chromatograph and mass spectrometry results showed peaks continuing to spill up to the maximum retention time indicating good thermal stability and bio-oil quality.
Optimization of roughing filtration unit for a handwashing wastewater recirculation point-of-use system
(IWA PUBLISHING COMAPANY, 2022-11-22) Olupot, Peter Wilberforce; Menya, Emmanuel; Jjagwe, Joseph; Wakatuntu, Joel; Román, Franz; Hensel, Oliver
A downward roughing filter unit consisting of silica sand as the filter medium was optimized for performance towards removal of turbidity and suspended solids from handwashing wastewater. Design-Expert software was employed to optimize media particle size, filter depth, and flow rate. Linear and quadratic models were found to best fit the responses of turbidity and suspended solids removal, respectively. Particle size and flow rate were the only parameters with significant effects on the removal of turbidity and suspended solids. Optimal conditions were found to be media particle size 0.6 mm, filter depth 12 cm, and flow rate 0.3 Lmin 1 , corresponding to removal efficiencies of 62 and 67% for turbidity and total suspended solids (TSS), respectively, as predicted by the model. Validation of the model at optimal conditions resulted in turbidity and TSS removal of 55 and 53%, respectively. Additionally, removal efficiencies of the roughing filter towards apparent colour, true colour, biochemical oxygen demand (BOD5), and chemical oxygen demand (COD) from handwashing wastewater were 56, 20,32, and 5%,respectively. Overall, although the turbidity of filtered water was .50 NTU, the reduction achieved by roughing filtration is a significant step in enhancing the performance of water treatment processes downstream, including filtration and adsorption by slow sand filters and activated carbon, respectively.
Production and Characterization of Paper from Banana Stem Fibre: Optimization Using Box-behnken Design (BBD)
(Taylor & Francis, 2023-03-22) Yiga, Vianney Andrew; Lubwama, Michael; Opio, James; Menya, Emmanuel; Nono, Denis; Nalubega Lubwama, Harriet
Banana stem is a known alternative to wood for the production of pulp and paper. During the production of paper, it is extremely important to save costs and time while at the same time enhancing the quality of produced paper. In the present study, the paper was developed from banana stem fiber by optimizing its density. Response surface methodology (RSM) using Box-Behnken design (BBD) was used to determine the optimum blending parameters of the developed papers. The influence of banana stem fiber amount (250-1000 g), water amount (1-2 litres), and blending time (5-10 min) on paper density was analyzed using the software Stat-Ease 360, Version 13. The optimum conditions of banana stem fiber amount, water amount, and blending time to achieve a density of 675.75 g/m3 were determined as 461.83 g, 1.31 liters, and 8.53 min, respectively. ANOVA results revealed that the quadratic model best fits the density response, with blending time and banana stem fiber amount as the most significant model terms. Linear effects were more predominant than quadratic and interaction effects. The developed density model was in close agreement with experimental findings with an R2 value of 0.9748. The developed paper had cellulosic contents, with volatiles as high as 82.11%wb and 2.11%wb ash composition. Future works on the thermal properties of paper are encouraged.
Production and performance of activated carbon from rice husks for removal of natural organic matter from water:
(Elsevier, 2017-11-02) Menya, E.; Olupot, P.W.; Storz, H.; Lubwama, M.; Kiros, Y.
Adsorption by activated carbon has great potential to improve natural organic matter (NOM) removal from water. However, the high production and regeneration costs limit its wide scale application. To address these limitations, research efforts have been focused on finding low-cost materials that can be transformed into activated carbon. Rice husk is one of such material of research focus, especially in developing countries, where over 96% of rice husks are generated globally. Although numerous investigations have been made concerning the production of activated carbon from rice husks, the existing scientific information still remains widely scattered in the literature. Furthermore, the scientific information regarding the performance of rice husk-activated carbon during NOM removal from water still remains poorly documented. This review article, therefore, provides ample information on efforts made by various researchers concerning the production of activated carbon from rice husks and its adsorption performance in relation to NOM removal from water. The properties and pretreatment of rice husks in relation to the production of activated carbon are discussed. Activation of rice husks by physical and chemical methods under numerous conditions is reviewed. Factors affecting NOM adsorption by activated carbon are briefly discussed. The adsorption performance of rice husk activated carbon is also reviewed with respect to NOM removal from water, and where possible compared with other source-derived activated carbons. The data from the literature revealed that NOM removal by rice husk activated carbon can be as effective as commercial activated carbon. Consequently, rice husk-activated carbon has the potential to serve as an alternative to commercial-activated carbon.
Progress in deployment of biomass-based activated carbon in point-of-use filters for removal of emerging contaminants from water: A review
(Elsevier, 2023-03-01) Menya, Emmanuel; Jjagwe, Joseph; Mpagi Kalibbala, Herbert; Storz, Henning; Wilberforce Olupot, Peter
Emerging contaminants (ECs) are increasingly being detected in drinking water, posing numerous public health concerns. Granular activated carbon (GAC) offers good prospects for removing ECs at point-of-use (POU), enabling households to have access to safe water. This paper reviews the current advances in the deployment of biomass-derived GACs (B-GACs) for the removal of ECs at POU. It highlights key sources, pathways, and impacts of ECs on public health. It also reveals preparation routes and performance aspects of B-GACs for POU water purification. Knowledge gaps on the subject matter were identified. The review revealed that shells of nuts, which are typically hard and of high density are the most investigated for valorisation into GAC for POU water purification. To encourage the wide application of B-GACs for POU water purification, there is a need to tailor available soft, low-density biomass wastes and suit them as GAC precursors for the removal of ECs at the point of use. Future studies need to focus on tailoring the production of B-GACs for the removal of specific ECs from water. Additional future research insights include the identification of re-generation options for B-GACs, options for removal of residual nanoparticles from the filtrate, lifecycle analysis, and costing of various GAC-based POU water filters.
Synthesis and Application of Granular Activated Carbon from Biomass Waste Materials for Water Treatment :
(Keai publishing, 2021-04-06) Jjagwe, Joseph; Olupot, Peter Wilberforce; Menya, Emmanuel; Mpagi Kalibbala, Herbert
There is an increased global demand for activated carbon (AC) in the application of water treatment and purification. Water pollutants that have exhibited a greater removal efficiency by AC included but are not limited to heavy metals, pharmaceuticals, pesticides, natural organic matter, disinfection by-products, and microplastics. Granular activated carbon (GAC) is mostly used in aqueous solutions and adsorption columns for water treatment. Commercial AC is not only costly but also obtained from non-renewable sources. This has prompted the search for alternative renewable materials for AC production. Biomass wastes present a great potential for such materials because of their availability and carbonaceous nature. This, in turn, can reduce the adverse environmental effects caused by poor disposal of these wastes. The challenges associated with biomass waste-based GAC are their low strength and attrition resistance which make them easily disintegrate under the aqueous phase. This paper provides a comprehensive review of recent advances in the production of biomass waste-based GAC for water treatment and highlights future research directions. Production parameters such as granulation conditions, use of binders, carbonization, activation methods and their effect on textural properties are discussed. Factors influencing the adsorption capacities of the derived GACs, adsorption models, adsorption mechanisms, and their regeneration potentials are reviewed. The literature reveals that biomass waste materials can produce GAC for use in water treatment with the possibility of being regenerated. Nonetheless, there is a need to explore 1) the effect of preparation pathways on the adsorptive properties of biomass-derived GAC, 2) sustainable production of biomass-derived GAC based on life cycle assessment and techno-economic analysis, and 3) adsorption mechanisms of GAC for removal of contaminants of emerging concerns such as microplastics and unregulated disinfection by-products.
Techno-economic assessment of municipal solid waste gasification for electricity generation:
(CIGR Journal, 2015-10-14) Kivumbi, Bernard; Olwa, Joseph; Martin, Andrew; Menya, Emmanuel
This study was aimed at assessing the techno-economic potential of municipal solid waste (MSW) generated in Kampala City for electricity production through gasification. The quantity, characteristics, and gasification parameters were determined. In addition, the gasifier-engine system components were sized, and an economic analysis was conducted to obtain the net present value (NPV) and the payback period. This study found that 523 t/d of MSW is collected in Kampala City. The biomass component of MSW was found to be 459.5 t/d with a moisture content of 71.09% on an as-received basis. The physical characteristics of the gasified biomass included 11.8% moisture content, 88.2% total solids, 25.9% ash content and 57.7 kg/m3bulk density. The resulting normalized producer gas constituted 11.64% H2, 13.70% CO, 16.09% CO2, 54.12% N2, 4.45% CH4and a lower heating value (LHV) of 4.75 MJ/Nm3. The design fuel flow rate of 0.23 kg/s, specific gasification rate (SGR) of 5089.29 kg h-1m-2and specific energy demand of 42.75 GJ m-2h-1were obtained. This yields a net electrical power output of 425.17 kW with an overall efficiency of 15.6%. The net annual electricity generation from a single gasifier-engine system was found to be 2.97 GWh/a. The economic analysis for this system worth $887 333 of investment cost yielded a payback period of 6.57 years while the NPV at 6% interest rate was found to be nine years with a value of $316 47.

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