African Journals Online
Journal of Civil Engineering, JKUAT

Abstracts of papers in JCE-JKUAT 
VOLUME 6, MARCH 2001

Enzymatic Profiles of Activated Sludge from a Wastewater Treatment Plant with Foaming Incident

Mulugeta Kibret¹⁾, Walter Somitsch²⁾ and Karl-Heinz Robra²⁾

1) Bahir Dar University, Department of Biology, P.O Box 79, Fax: (08) 202025, Tel: 200143 Ext. 217, e-mail: [email protected] 

2) Institute for Environmental Biotechnology, Technical University of Graz, Petersgasse 12/I 8010 Graz, Austria

Abstract

Activated sludge samples collected from a treatment plant, with foaming experience in the month of July, was characterized enzymatically. Hexokinase, Glyceraldehyde-3-phosphate dehydrogenase and Adenylate kinase activity assays were conducted before, during and after the foaming episode. The spectrum of enzyme activities demonstrated change in the biochemical activity of the activated sludge, with peaks in the foaming month. Significant difference in enzyme activities was found between the foaming and nonfoaming months. The potential use of these enzymes in foam prevention and control is implied. Foaming incident was associated with increase in phosphate and lipid contents in the influent.

Sustainable Management of Domestic Solid Wastes in Developing Countries: Operations, Environmental Concerns and Community-Based Strategies in Kenya

F. N. Sira¹⁾, G. M. Thumbi ²⁾, H. M. Bwisa¹⁾, L. A. Oyugi¹⁾

1) Institute for Human Resources Development, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya

2) Department of Civil Engineering, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya

Abstract

This paper reports the results of an investigation into the problems of solid waste operations and disposal in Thika and Nakuru municipalities in Kenya. The objectives of the study were to estimate the quantity of waste generated per capita, determine the composition of wastes and assess the environmental concerns of the community and their participation in the management of domestic solid wastes. The waste generation per capita was estimated at 0.59 kg/person/day. Eighty five percent of the solid wastes consisted of food wastes. Some solid wastes contained hazardous household substances such as dry cells and discarded containers of health care products. The urban community was concerned about health and environmental effects of improperly managed solid wastes. On the basis of the findings of this study, it is concluded that community participation could be a feasible strategy to manage urban solid wastes, provided that the community is sensitised, educated and assisted in handling some solid waste operations.

The Relationship Between Windspeeds and Kijito Windpump Discharges in Rusinga Island, Lake Victoria

Kabok P.A.¹⁾ and Chemelil, M.C.²⁾

1) Lake Basin Development Authority, P.O. Box 1516, Kisumu, Kenya

2) Department of Agricultural Engineering, Egerton University, P.O. Box 536, Njoro, Kenya.

Abstract

A 6.1m rotor diameter Kijito wind pump was tested for the relationship of water discharge and wind speed in a micro-irrigation setup on Rusinga Island along the shores of Lake Victoria in Kenya. Wind speed measurements were recorded using an installed 10m-cup anemometer placed approximately two rotor diameters away from the wind pump. Discharge record measurements were made using an Arad water meter positioned immediately after the wind-pump air chamber. The objective was to establish a field relationship of the wind-pump discharge and the wind speed. The results indicate the performance of the wind-pump at site to be within the cut-in speed and mostly below the rated wind speed. The cubic model (Q = KV3) was not appropriate as the constant depended on arbitrary fitting or choice. A linear model was instead found to be a suitable relation between wind-speed and discharge for synchronous recording intervals greater than 3 hours.

Modelling of Unsteady Flow in Compound Channels

D.K. Tuitoek¹⁾ and F.E. Hicks²⁾

1. Department of Water and Environmental Engineering, Egerton University,
2. P.O. Box 536, Njoro, Kenya.
3. Department of Civil Engineering, University of Alberta, Edmonton, Canada. T6G 2G7

Abstract

A model based on the St. Venant equations of flow with incorporation of terms to account for the momentum transfer phenomenon, was developed to route unsteady flow in compound channels. For the main channel, the full dynamic equations were used while in the floodplains, a diffusive model was used. Both included mass and momentum transfer terms. The resulting equations called CCDG 1-D model were solved by the characteristic-dissipative-Galerkin (CDG) finite element method. Results from the CCDG 1-D model were compared to observed experimental data. The unsteady results also showed that the CCDG 1-D model showed improvement on discharge prediction when the apparent shear was included in the model.

Monthly water balance model for Ndarugu basin, Kenya

Maurice 0. Nyadawa¹⁾ and Evans M. Kamau¹⁾

1) Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000, Nairobi, Kenya

Abstract

Objective of this study is to evaluate the performance of a known monthly water balance model in Ndarugu river basin in Kenya. The model is slightly modified to suit hydrologic conditions in the basin. The study apart from establishing relevant model parameters has recommended optimum length of period for continuous simulation to reduce effect dynamic changes in the basin.

Development of a Simple Hydraulic Performance Model for Sasumua Pipelines of Nairobi Water Supply, Kenya

K.S. Makhanu¹⁾

1) Department of Civil Engineering, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000, NAIROBI

Abstract

Most of the major water supply systems in the modem cities of Eastern Africa are just within 50 years of operation. Due to the specific quality of raw water in the region, often with high concentrations of manganese, the treatment methods adopted and the type of conveyance systems in operation, there are unique operational problems. At certain periods in the life of their operations, these water systems need hydraulic performance assessments on the basis of which rehabilitation exercises may he undertaken. This paper describes hydraulic assessment after rehabilitation of Sasumua treated water mains of the Nairobi Water Supply system in Kenya. Swabbing or pigging was adopted as the most economical and cost effective method of rehabilitation under the prevailing circumstances. During and at the completion of the swabbing, the need for a simple and easy to apply hydraulic performance model became apparent. In this paper a simple hydraulic performance model is developed that utilizes local staff and equipment that should provide an affordable procedure not only for Nairobi but other upcoming urban centers in the East African region. A simple system uniformity coefficient that is based on the results of the model prediction is proposed. The procedure for conducting the field flow test in the determination of the Hazen William's friction factor is described by utilizing the set up and data of the field flow test carried out on 11^th August 1988 on completion of the swabbing exercise.

Geomorphological characteristics of upper athi basin and their effect on runoff

Maurice 0. Nyadawa¹⁾ and Sospeter K. Muiruri¹⁾

1) Department of Civil Eng., Jomo Kenyatta University of Agriculture and Technology,

P.O. Box 62000, Nairobi, Kenya.

Abstract

This study aims at comparing runoff response of two subbasins in upper Athi basin in Kenya on the basis of their geomorphological characteristics. The study revealed that the distribution of bifurcation ratios and form factors agree with the observed runoff variation in the two subbasins, however basin relief indicate the opposite.

Behavior of Skin Friction of Piles subjected to Top-downward and Base-upward compression Loadings

Kiptanui Jonah Arap Too¹⁾ and Wen Qingbo²⁾

1) Lecturer, Department of Civil Engineering, Jomo Kenyatta University of Agriculture and Technology, P. 0. Box 62000, Nairobi" KENYA

2) Asst. Prof, Institute of Geotech. Engrg, School of Civil Engrg, Tsinghua University, Beijing 100084 P.R. CHINA

Abstract

In situ results of Osterberg cell load test and the conventional static compression load test are compared. Finite Element Method (FEM) is used to study the effects of changes in boundary conditions, mechanism of pile-soil interaction and the accompanying change in soil stress, which are responsible for the difference in skin friction under the two loading modes. Pile-soil system is analyzed using Duncan-Chang E-B model while the interface material is modeled using Goodman element. Poisson effect affects the diameter of the loaded end (top or base) of the pile and on the radial stress in the soils around the pile. Changes in radial stress with the direction of loading contribute the major part of the different resistance of the soil-pile system. In-situ and FEM results show lower shaft resistance when the pile is subjected to base-upward compression than when it is compressed from the top. The ratio of skin friction of 0.85 is obtained, the ratio is expected to be different for different soils.

Finite element analysis of tubular joints in offshore structures

S. O. Abuodha¹⁾ F. M Burdekin²⁾

1) Part Time Lecturer, Department of Civil and structural Engineering , Jomo Kenyatta University of Agriculture and Technology, P.O. Box 6200, Nairobi Kenya

2) Professor, Department of Civil Engineering, University of Manchester, Instate of Science and Technology, P.O. Box 88, Manchester, England. M60 1QD

Abstract

This research work was involved in the finite element tool to determine the ultimate strength of initially uncorked joints, which fail by development of tearing fracture at the weld toe. The local approach methodology in contrast to classical fracture mechanics was used. Finite element analysis was done of T-joint plate geometries, representing a 2-D model of the joint between the brace and the chord walls. This was subsequently followed but finite element analysis of six tubular joints. A global analysis was initially undertaken, then the submodel analysis carried in the areas of stress concentration.

Performance of highway bridges during high intensity earthquakes

Kuo-Chun Chang¹⁾, Walter 0. Oyawa²⁾ and Eiichi Watanabe³⁾

1) Professor, Department of Civil Engineering, National Taiwan University, Taipei, Taiwan 10617, R.O.C.

2) Lecturer, Department of Civil Engineering, JKUAT, P.O.Box 62000, Nairobi, Kenya.

3) Professor, Department of Civil Engineering, Kyoto University, Kyoto 606-8501, Japan.

Abstract

Just when it was thought that it would take many years before a severe earthquake like the Hanshin-Awaji (Kobe) earthquake wrecked havoc, another catastrophic earthquake struck the central region of Taiwan in 1999, killing over 2,350 people and injuring 10,000 people. The earthquake incurred tremendous damage to infrastructure mostly highway bridges and buildings caused by fault ruptures, near-fault strong motion and inadequate unseating prevention mechanism. Damage to bridges included fault rupturing, collapsed spans, flexural and/or shear failures, liquefaction, slope failures, soil settlement, and landslides. Most urgent in mitigating the bitter experiences of such high intensity earthquakes is the revision of seismic design code to include elasto-plastic design for high intensity earthquakes taking into account dynamic response of structures, as well as improvement on the design of minor but important elements such as shear keys and concrete stoppers to prevent unseating of girders. In recognition of limited knowledge on structural response induced by near-fault earthquakes and fault ruptures, "easy to repair and reconstruct" concept should be a priority in bridge design and construction, and research should be intensified.

Simplified analysis of filled steel tubular stub columns under compression

Walter 0. Oyawa¹⁾ Kunitomo Sugiura²⁾, and Eiichi Watanabe³⁾

1) Lecturer, Department of Civil Engineering, JKUAT, Nairobi, Kenya.

2) Associate Professor, Department of Civil Eng. Systems, Kyoto University, Kyoto 606-8501, Japan.

3) Professor, Department of Civil Engineering, Kyoto University, Kyoto 606-8501, Japan.

Abstract

As a sequel to previous experimental studies, this paper gauges the applicability of available analytical formulations e.g. those specified in various national codes, for the evaluation of compressive strength of filled steel tubular stub columns (FST), filled with unconventional polymer-based fill materials. In conjunction with experimental results, it is deduced that current national codes either underestimate or overestimate the strength of filled steel stub columns. Instead, a simple summation of the strength of components forming the composite section is found to rationally predict the stub column strength. However, continued research is still required to accurately predict the effects of confinement, on the steel tube and on the fill material, hence expressions for the proportion of load resisted by each component.