School of Science, Technology and Engineering

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Knowledge is Power: An Exploratory Study on Information Sources for Prostate Cancer among Men in Nairobi County, Kenya
(African Journal of Urology, 2022) Osewe, Ann; Shivachi, Taji Isindu; Sibuor, John Odero
Investigation of Wood Chips as Internal Carbon Source Supporting Denitrification Process in Domestic Wastewater Treatment
(International Journal of Environmental and Ecological Engineering, 2016) Lorivi, Ruth; Li, Jianzheng; Ambuchi, John Justo; Deng, Kaiwen
Microbial community analysis in a combined anaerobic and aerobic digestion system for treatment of cellulosic ethanol production wastewater
(2015-06-22) Shan, Lili; Yu, Yanling; Zhu, Zebing; Zhao, Wei; Wang, Haiman; Ambuchi, John Justo; Feng, Yujie
This study investigated the microbial diversity established in a combined system composed of a continuous stirred tank reactor (CSTR), expanded granular sludge bed (EGSB) reactor, and sequencing batch reactor (SBR) for treat ment of cellulosic ethanol production wastewater. Excellent wastewater treatment performance was obtained in the com bined system, which showed a high chemical oxygen demand removal efficiency of 95.8 % and completely eliminated most complex organics revealed by gas chromatography–mass spectrometry (GC–MS). Denaturing gradient gel electropho resis (DGGE) analysis revealed differences in the microbial community structures of the three reactors. Further identifica tion of the microbial populations suggested that the presence of Lactobacillus and Prevotella in CSTR played an active role in the production of volatile fatty acids (VFAs). The most diverse microorganisms with analogous distribution patterns of different layers were observed in the EGSB reactor, and bacteria affiliated with Firmicutes, Synergistetes, and Thermotogae were associated with production of acetate and carbon dioxide/hydrogen, while all acetoclastic methanogens identified belonged to Methanosaetaceae. Overall, microor ganisms associated with the ability to degrade cellulose, hemicellulose, and other biomass-derived organic carbons were observed in the combined system. The results presented herein will facilitate the development of an improved cellulos ic ethanol production wastewater treatment system.
Simultaneous algae-polluted water treatment and electricity generation using a biocathode-coupled electrocoagulation cell (bio-ECC)
(Elsevier, 2017-06-21) Donga, Yue; Qub, Youpeng; Li, Chao; Hana, Xiaoyu; Ambuchi, John Justo; Liua, Junfeng; Yua, Yanling; Fenga, Yujie
How to utilize electrocoagulation (EC) technology for algae-polluted water treatment in an energy-efficient manner remains a critical challenge for its widespread application. Herein, a novel biocathode-coupled electrocoagulation cell (bio-ECC) with sacrificial iron anode and nitri- fying biocathode was developed. Under different solution conductivities (2.33 ± 0.25 mS cm−1 and 4.94 ± 0.55 mS cm−1), the bio-ECC achieved almost complete removal of algae cells. The maximum power densities of 8.41 and 11.33Wm−3 at corresponding current densities of 48.03A m−3 and 66.26A m−3 were obtained, with the positive energy balance of 4.52 and 7.44Wm−3. In addition, the bio-ECC exhib- ited excellent NH4 +-N removal performance with the nitrogen removal rates of 7.28 mg L−1 h−1 and 6.77 mg L−1 h−1 in cathode chamber, indicating the superiority of bio-ECC in NH4 +-N removal. Pyrose- quencing revealed that nitrifiers including Nitrospira, Nitrobacter, Nitrosococcus, and Nitrosomonas were enriched in biocathode. The removal mechanisms of algae in anode chamber were also explored by AFM and SEM-EDX tests. These results provide a proof-of-concept study of transferring energy-intensive EC process into an energy-neutral process with high-efficiency algae removal and electricity recovery.
Hematite and multi-walled carbon nanotubes stimulate a faster syntrophic pathway during methanogenic beet sugar industrial wastewater degradation
(2017-09-22) Ambuchi, John Justo; Zhang, Zhaohan; Dong, Yue; Huang, Linlin; Feng, Yujie
The quest to understand and subsequently improve the role played by bacteria and archaea in the degradation of organic matter both in natural and engineered anaerobic ecosystems has intensified the utilization of nanoparticles. Microbial communities are known to syntrophically cooperate during the anaerobic conversion of substrates into methane gas via the direct exchange of electrons. In this study, the role of hematite (Fe2O3—750 mg/L) and multi-walled carbon nanotubes (MWCNTs—1500 mg/L) during the degradation of beet sugar industrial wastewater (BSIW) in a batch experiment was investigated. Hematite and MWCNTs enhanced methane gas generation by 35 and 20%, respectively. Furthermore, microbial syntrophic communities might have exchanged metabolic electrons more directly, with hematite and MWCNTs serving as electron conduits between the homoacetogens and methanogens, thereby establishing a direct interspecies electron transfer (DIET) pathway. Additionally, hematite and MWCNTs enriched the bacteria Firmicutes while Chloroflexi reduced in abundance. Scanning electron microscopy and confocal laser scanning microscopy demonstrated that extracellular polymeric substances had noticeable interactions with both hematite and MWCNTs. Our findings provide vital information for more understanding of the response of microbes to hematite and MWCNTs in a complex natural environment.
Integrated expanded granular sludge bed and sequential batch reactor treating beet sugar industrial wastewater and recovering bioenergy
(2016-07-21) Ambuchi, John Justo; Junfeng, Liu; Lili, Shan; Haiman, Wang; Lorivi, Moirana Ruth; Mohammed, Mohammed O. A; Xiangtong, Zhou; Yujie, Feng
The exponential rise in energy demand vis-à-vis depletion of mineral oil resources has accelerated recovery of bioenergy from organic waste. In this study, a laboratory- scale anaerobic (An)/aerobic (Ar) system comprising of ex- panded granular sludge bed (EGSB) reactor coupled to an aerobic sequential batch reactor (SBR) was constructed to treat beet sugar industrial wastewater (BSIW) of chemical oxygen demand (COD) 1665 mg L−1 while harnessing meth- ane gas. The EGSB reactor generated methane at the rate of 235 mL/g COD added, with considerably higher than previ- ously reported methane content of 86 %. Meanwhile, contam- inants were successfully reduced in the combined An/Ar sys- tem, realizing a removal rate of more than 71.4, 97.3, 97.7, and 99.3 % of organic matter as total phosphorus, total nitro- gen, biological oxygen demand (BOD), and soluble COD, respectively. Microbial community analysis showed that the bacterial genus Clostridium sp. and archaeal genus Methanosaeta sp. dominated the EGSB reactor, while Rhodobacter sp. dominance was observed in the SBR. The ob- tained experimental results indicate that the integration of ex- panded granular sludge bed and sequential batch reactor in treating BSIW obtained competitively outstanding performance.
Biogas enhancement using iron oxide nanoparticles and multi-wall carbon nanotubes
(International Journal of Chemical, Molecular, Nuclear, Materials and Metalurgical Engineering, 2016) Ambuchi, John Justo; Zhang, Zhaohan; Feng, Yujie
Investigation on decolorization of biologically pretreated cellulosic ethanol wastewater by electrochemical method
(Elsevier, 2017-04-25) Shan, Lili; Liu, Junfeng; Ambuchi, John Justo; Yu, Yanling; Huang, Linlin; Feng, Yujie
The biologically pretreated cellulosic ethanol wastewater poses a serious environmental concern because of its refractory and color compounds. The decolorization of electrochemical oxidation using Sb doped Ti/ SnO2 electrode for advanced treatment of cellulosic ethanol wastewater under different current density (5–30 mAcm2 ), initial pH (3–8.9) and supporting electrolyte (0–0.25 M NaCl) was investigated in this study. Complete decolorization, 8.5% chemical oxygen demand (COD) and 69.1% dissolved organic carbon removal efficiencies were achieved under the optimal conditions (20 mAcm2 , pH 5 and supporting elec- trolyte of 0.1 M NaCl) after 150 min. The energy consumption required to meet National Discharge Standard (GB 27631-2011) is 93.8 kWh kg COD1 . Further investigation revealed that hydroxyl radicals played a primary role in the degradation of organic contaminants, while active chlorine formed from chloride oxidation played a less important role. Direct anodic oxidation and indirect reaction via perox- odisulfate generated from sulfate oxidation could be negligible. The formation of chlorination by- products appeared to be low since the final total Trihalomethanes concentration detected was 263 mg L1 , with the detection of chloroform as the main Trihalomethanes.
Performance of CSTR–EGSB–SBR system for treating sulfate-rich cellulosic ethanol wastewater and microbial community analysis
(2017) Shan, Lili; Zhang, Zhaohan; Yu, Yanling; Ambuchi, John Justo; Feng, Yujie
Performance and microbial community composition were evaluated in a two-phase anaerobic and aerobic system treating sulfate-rich cellulosic ethanol wastewater (CEW). The system was operated at five different chemical oxygen demand (COD)/SO4 2− ratios (63.8, 26.3, 17.8, 13.7, and 10.7). Stable performance was obtained for total COD removal efficiency (94.5%), sulfate removal (89.3%), and methane production rate (11.5 L/day) at an organic loading rate of 32.4 kg COD/(m3 · day). The acidogenic reactor made a positive contribution to net VFAs production (2318.1 mg/L) and sulfate removal (60.9%). Acidogenic bacteria (Megasphaera, Parabacteroides, unclas sified Ruminococcaceae spp., and Prevotella) and sulfate reducing bacteria (Butyrivibrio, Megasphaera) were rich in the acidogenic reactor. In the methanogenic reactor, high diver sity of microorganisms corresponded with a COD removal contribution of 83.2%. Moreover, methanogens (Methanosaeta) were predominant, suggesting that these or ganisms played an important role in the acetotrophic methanogenesis pathway. The dominant aerobic bacteria (Truepera) appeared to have been responsible for the COD removal of the SBR. These results indicate that dividing the sulfate reduction process could effectively minimize sulfide y, which is important for the successful operation of sys tem treating sulfate-rich CEW
Cascade degradation of organic matters in brewery wastewater using a continuous stirred microbial electrochemical reactor and analysis of microbial communities
(Scientific Reports, 2016) Wang, Haiman; Qu, Youpeng; Li, Da; Ambuchi, John Justo; He, Weihua; Zhou, Xiangtong; Liu, Jia; Feng, Yujie
A continuous stirred microbial electrochemical reactor (CSMER), comprising of a complete mixing zone (CMZ) and microbial electrochemical zone (MEZ), was used for brewery wastewater treatment. The system realized 75.4±5.7% of TCOD and 64.9±4.9% of TSS when fed with brewery wastewater concomitantly achieving an average maximum power density of 304±31m W m−2. Cascade utilization of organic matters made the CSMER remove a wider range of substrates compared with a continuous stirred tank reactor (CSTR), in which process 79.1±5.6% of soluble protein and 86.6±2.2% of soluble carbohydrates were degraded by anaerobic digestion in the CMZ and short-chain volatile fatty acids were further decomposed and generated current in the MEZ. Co-existence of fermentative bacteria (Clostridium and Bacteroides, 19.7% and 5.0%), acetogenic bacteria (Syntrophobacter, 20.8%), methanogenic archaea (Methanosaeta and Methanobacterium, 40.3% and 38.4%) and exoelectrogens (Geobacter, 12.4%) as well as a clear spatial distribution and syntrophic interaction among them contributed to the cascade degradation process in CSMER. The CSMER shows great promise for practical wastewater treatment application due to high pre-hydrolysis and acidification rate, high energy recovery and low capital cost
A combined microbial desalination cell and electrodialysis system for copper-containing wastewater treatment and high-salinity-water desalination
(Journal of Hazardous Materials, 2017) Donga, Yue; Liua, Junfeng; Sui, Mingrui; Ambuchi, John Justo; Qub, Youpeng; Wanga, Haiman; Fenga, Yujie
A new concept for heavy metal removal by forming hydroxide precipitation using alkalinity produced by microbial desalination cell (MDC) was proposed. Four five-chamber MDCs were hydraulically connected to concurrently produce alkalinity to treat synthetic copper-containing wastewater and salt removal. There was nearly complete removal of copper, with a maximum removal rate of 5.07 kg/(m3 d) under the initial copper concentration of 5000 mg/L (final pH of 7). The final copper concentration met the emission standard for electroplating of China (0.5 mg/L, GB 21900-2008). XRD analysis indicated copper was precipitated as Cu2Cl(OH)3. The best performance of MDCs in terms of average power density, salt removal and COD removal rate achieved in stage 3 were 737.3 ± 201.1 mW/m2, 53.6 ± 0.8 kg/(m3 d), and 1.84 ± 0.05 kgCOD/(m3 d) respectively. For purposes of water recovery, an electrodialysis (ED) system was presented based on in-situ utilization of generated electricity by MDCs as post-desalination treatmentfor salt effluent after sedimentation. The maximum discharging voltage of 12.75 ± 1.26V at switching time (Ts) of 15 min using a capacitor-based circuit produced a maximum desalination efficiency of 30.4 ± 2.6%. These results indicatedthatthis combinedsystemholds greatpromise for real-worldtreatment of copper- containing wastewater and deep desalination of high-salinity-water.
Determination of Heavy Metal Levels in Surface Waters and Sediments of River Riana, Kisii County, Kenya
(2023-10) Mongare, Thomas Momanyi; Ambuchi, John Justo; Ngodhe, Steve Omari; Nyamai, Daniel; Ongachi, Francis Olal; Wanjara, Amos Otieno
In this paper, some trace metals were seasonally determined for six months between January -June 2021 (to cover both the wet and dry seasons) in surface water and sediments from River Riana in Kisii County. The river is an important source of drinking water and fisheries and receives an array of wastes from agricultural, industrial, commercial and sewage treatment. Consequently, this study evaluated the levels or concentrations of heavy metals (Pb, Cr. Ni, Mn, Cu and Zn) in surface water and surface sediments and the effect of seasonal variations on their concentrations. Samples were collected monthly from three sampling sites along the River and the results of heavy metal concentrations were compared with national and international guidelines including the Kenya Bureau of Standards, World Health Organization (KEBS/WHO) and WHO sediment quality guidelines (SQGs) respectively to establish pollution level. Metal concentrations in water and sediments were analyzed using inductively coupled plasma atomic emission spectroscopy (Shimadzu ICPE 9000) after nitric acid digestion. The results obtained showed that the mean range of heavy metals in water (ppm) were: Pb (0.031-0.196), Cr (<0.001-0.009), Ni (0.014-0.321), Mn (0.131-0.351). Cu (0.114-0.370) and Zn (0.132-0.326) while the mean range of metals in surface sediments (mg/kg) was; Pb (0.041-8.74), Cr (0.001- 1.31), Mn (276-692), Cu (1.35-9.74) and Zn (6.37-15.67) respectively. The heavy metals Cr, Cu and Zn complied with the WHO and KEBS drinking water recommended safe limits while the Pb and Mn concentrations exceed the recommended safe limits but Ni concentrations exceeded KEBS recommend safe limit for drinking water. The mean monthly concentrations for the heavy metals in surface water and surface sediments for the River decreased in the order Mn>Zn>Cu>Pb>Ni.>Cr and Mn>Zn>Cu>Ni>Pb.>Cr respectively. The heavy metal concentrations were generally higher during the dry season than the wet season in both surface water and sediments however, there were no significant seasonal differences (p>0.05) except for Cr and Mn in water. All the heavy metals complied with WHO fresh water SQGs and exhibited no significant seasonal variations (p ≥0.05) in water for surface sediments. The River Riana was contaminated by all the determined trace metals and this indicated potential toxicity risk, thus the need for regular monitoring. We recommended determination of other toxic metals in water, sediments and biota such as fish form this river
On Skew Class (BQ) Operators
(Iconic Research and Engineering Journals, 2022-12) Wanjala, Victor; Obiero, Beatrice Adhiambo
The class of Skew (BQ) operators acting complex Hilbert on an separable H is introduced in this paper. An operator if K ∈L (H) is said to belong to class Skew (BQ) if K commutes with a (BQ) operator, that is, [K∗2K2 (K∗K) 2] K = K [(K∗K) 2 K∗2K2]. We explore some properties that this class is enriched with. We then scan the relation of this class to other classes and then oversimplify it to the class of Skew (nBQ).
The Influence of Part-Time Lecturers' Payment Management on the Dons' Performance
(Journal of Emerging Technologies and Innovative Research (JETIR), 2021-07) Oguk, Charles; Imboga, Herbert
Kenya’s university student enrolment had risen in the year 2016 to around 23 percent following increased female enrolment, massive infrastructure development at the universalities, the introduction of new programs, lowering university entry grades as well as the opening of more campuses by the universities, (Wanjau, Okeyo, & Rimiru, 2016). In the period of 2015, the enrolment shot up from 361,379 to 443,783, and this has created more challenges for universities as they now have to reduce expenses and seek new funding avenues to expand facilities for coping with the surge, (Kenya National Bureau of Statistics, 2015). The university student enrollment has further risen with the recent lowering of the entry cutoff points, as those KCSE candidates scoring grade C+ are now eligible for government funded university admission. This puts competitive pressure on the universities and also on the understaffed academic members and thus necessitating the engagement of part-time lecturers.
Comparative Analysis of Compressive Strength of Bamboo Leaf and Baggash Ash Concretes
(MACHAKOS UNIVERSITY JOURNAL OF SCIENCE AND TECHNOLOGY, 2021) Shitote, Stanley
Billions tons of conventional concrete are produced yearly as well as cement which emit large tons of carbon dioxide due to huge millions of metric tons produced annually. Sequel to this, there is need to produce a sustainable product due to pollution from cement production, using agricultural waste materials which have recently been found to be of great interest to construction industries at large due to their ability to substituting cement will solve environmental and pollution related issues. Bamboo leaf ash and baggash ash are produced as a result of combustion which serves as supplementary cementitious materials and can be used for construction purposes. This study determines the compressive strength of concrete without ashes, bamboo leaf ash, and baggash ash concrete at varying percentage replacement of 5%, 10%, 15%, 20% respectively. Physical test, workability test, compressive strength test, and durability test was performed on concretes. A total of 138 cubes were produced using 100*100*100 size cube cured at 7, 28, 56 and 90 days, of which 108 cubes were to ascertain compressive strength for all the concretes, while 30 cubes were used for durability test. Based on experimental results obtained, BLA surpassed BA concrete, and concrete without ash in term of compressive strength at early and later age of curing using 10% as optimum level of replacement, thus, one way ANOVA indicated, that BLA concrete is statistically better than BA concrete and statistically the same at 56 and 90 days of curing for conventional, BLA, and BA concrete. Furthermore, BLA and BA concretes reduced durability. BA concrete increased the water absorption, permeable voids, and sorptivity. As a result, BLA and BA can be considered as a good pozzolanic material which can save cost of construction, improved concrete properties.
Predicament and Development Direction of Network Effectiveness Learning: Analysis and Research of Ergonomic Effectiveness
(Educational Research and Policies, 2022-08-31) Annes, Philip
Human Factors and Ergonomics play a key role in the design and development of computer applications and tools. This is a multidisciplinary approach used to ensure that systems and learning environments are designed to aid in user’s performance. This study aimed at analyzing the human factors and ergonomics, their effects on the effectiveness of e-learning platform at Rongo University. A descriptive research methodology was used to collect and analyze the data from a sample size of 150consisting of faculty and the students. Using stratified sampling technique from five schools, a questionnaire was the main data collection tool and data was analyzed using SPSS. It was observed that the level of e-learning platform at Rongo University is very low at less than 2%. The study found that, psychological effects such as, motivation, individual perception, self-regulation, course content, computer literacy and lack of discipline from the e-learning students, were the major contributing factors. Student and faculty correlated significantly with each other across schools with course content being the main factor at a mean score of 8.60 for faculty and 21.40 for students. The Activity Theory has been used as a theoretical background that guided the study.
Modelling the Deflection of Reinforced Concrete Plates Using the Symplectic Method
(Journal of Sustainable Research in Engineering, 2020) Shitote, Stanley; Saiyalel, Nakeel Matthew; Abuodha, Sylvester
This work aims to predict the flexural behavior of reinforced concrete slabs by combining a smeared finite element model derived from fracture mechanics for the simulation of the decline in the flexural rigidity of the concrete, and the symplectic theory of elasticity, which governs the bending of the structural element in question. Appropriate modifications have been carried out on the smeared finite element model to better reflect the compressive behavior of concrete. The loading is incremental such that in each load step, concrete behavior is treated as an elastic problem, and the response of the concrete slabs determined using the symplectic method, which provides exact bending solutions to thin rectangular plates. For the validation of the model thus proposed, congruent cases of concrete slabs in literature are studied. Evaluation of the results achieved from the proposed model demonstrated relatively good predictability of reinforced concrete slabs in flexure.
On class (n, mBQ) Operators
(World Journal of Advanced Research and Reviews, 2021-06-26) Obiero, Beatrice Adhiambo; Wanjala, Victor
In this paper, we introduce the class of (n, mBQ) operators acting on a complex Hilbert space H. An operator if T ∈ B (H) is said to belong to class (n, mBQ) if T ∗2mT 2n commutes with (T ∗mTn ) 2 equivalently [T ∗2mT 2n, (T ∗mTn)2] = 0, for a positive integers n and m. We investigate algebraic properties that this class enjoys. Have. We analyze the relation of this class to (n,m)-power class (Q) operators.
First-Principles Calculations Of Structural, Electronic And Elastic Properties Of Tysonite Lanthanum Fluoride (Laf3)
(Journal of Research in Environmental and Earth Science, 2018-06) Nyawere, P.W.O; Barasa, Daniel Bem; Nafulawabululu, Elicah
The structural, electronic and elastic properties of tysonite Lanthanum fluoride (LaF3) have been studied using Density Functional Theory. The lattice constants were calculated and then the values fitted into the energy volume relation using the Birch-Murnaghan third order equation of state. Lattice parameter in this calculations are as follows; a = 7.245Å, c = 7.388Å and c/a = 1.02Å against 7.128Å, 7.329Å and 1.028Å of CASTEP. A band gap of 7.78eV was obtained in comparison to the 9.0eV of experiment and this is because DFT-GGA/LDA is known to underestimate band gaps. The results for elastic constants for the directions C11 = 170.1, C12 = 76.26, C13 = 58.69, C14 = -1.66, C33 = 208.08 and C44 = 33.90. Compared to other theoretical and experimental values, these results are in good agreement.
On N-A-Metrically Equivalent and A-Metrically Equivalent Operators
(International Journal of Mathematics And its Applications, 2021) Wanjala, Victor; Obiero, Beatrice Adhiambo
A-metrically equivalent operators may be regarded as a generalization of metrically equivalent operators. This is realized when A= I and T ]= T ∗ . Definition 1.1. Two operators S ∈ BA(H) and T ∈ BA(H) are said to be: (1). A-metrically equivalent, denoted by S ∼A-m T, provided T ]A T = S ]A S equivalently; k T ξ kA=k Sξ kA ∀ ξ ∈ H. T ]A = A †T ∗A, in which A † is the Moore-penrose inverse of A. (2). n-A-metrically equivalent, denoted by S ∼n-A-m T, provided T ]A T n = S ]A S n for a positive integer n. Definition 1.2. An operator T ∈ B(H) is (1). A-Contraction if k T ξ kA≤k ξ kA for every ξ ∈ H ⇔ T ∗AT ≤ A. (2). A-Isometry if T ∗AT = A ⇔k T ξ kA=k ξ kA for every ξ ∈ H. (3). A-Unitary if T ∗AT = T AT ∗ = A ⇔k T ∗ ξ kA=k T ξ kA=k ξ kA for every ξ ∈ H. (4). A-Normal if T ∗AT = T AT ∗ ⇔k T ξ kA=k T ∗ ξ kA for every ξ ∈ H. (5). A-Partial isometry if k T ξ kA=k ξ kA for every ξ ∈ N(AT) ⊥A .

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