Design suggestions for improvements of the Kendu Bay Adventist Hospital sewage system and

111 Pages·2008·3.65 MB·English

Emil Martinsson
Erik Martinsson
Sören Säf

Bachelor’s of Science Thesis
Level ECTS: 30 credits
Spring Term 2007

School of Technology and Society
Development Assistance Engineering
University of Skövde
Sweden
Supervised by:
Programme director Mr. Per Hellström, Development Assistance Enginering Programme
School of Technology and Society, University of Skövde, Sweden and Dr. Okumo Odira,
Department of Civil and Construction Engineering, University of Nairobi, Kenya.

Examinator:
Dr. Tobias Andersson, School of Technology and Society, University of Skövde, Sweden

ISBN 978-91-633-2366-9
© Emil Martinsson, Erik Martinsson, Sören Säf 2007

Printed by Sören Säf, Jönköping, Sweden, 2007
Abstract

The process of allocating necessary resources like clean water, fuel/energy and food have
resulted in an unsustainable use of natural resources causing problems with Soil erosion, soil
fertility, desertification, deforestation, eutrophication and global warming. The purpose of this
study was to gain information on the functional design of a waste management system
enabling the organic components of domestic waste to be processed as useful resources while
at the same time allow them to be re-circulated. The main part of this study was carried out at
the Kendu SDA Hospital in the Rachyonyo district in western Kenya. For the case of this
study two main objectives where chosen. The first was to develop a principal technological
solution using three classed “appropriate technologies” found suitable for the purpose namely
biogas, ecological water treatment systems and slow sand filtration. The second was to further
analyse each included technology to further develop their potential to fit the concept. Results
from the pilot facilities where then to be retrieved from the actual component selection and
construction process itself, with performance analysis left for future studies.

The main purpose of the biogas system study has been to evaluate the original ideas of overall
concept, details, materials and construction methods. The 1 m3 biogas system has improved
significantly during the development process and is today not far from an implementation, i.e.
construction on a slightly larger scale. The biogas system developed during the project has
proven to have potential for digestion of both latrine and kitchen waste. Using the two as fuel
for the process does not only remove a problem – it grants several benefits.

The ecological waste water treatment system main objective was to design and construct a
pilot SSF-wetland. Results show that the construction process for smaller scaled SSF systems
is simple and does not require trained personnel or specialized equipment and that significant
cost reduction can be made by using locally available materials.

The slow sand filtration sub system concept is called PT SCX and though still in the stage of
development proved to have great potential concerning both efficiency and sustainability. The
PT SCX comprises the advantages of slow sand filtration with further development of
individual system solutions. It was adapted to enable both integration to the IWESS solution
and stand alone installations purifying even highly turbid surface water sources to drinking
water quality.

The result from the study confirms the suitability of the three included technologies,
ecological waste water treatment, biogas and slow sand filtration to work in an integrated
system called IWESS- Integrated Water Energy and Sanitation Solution. The combined
subsystems can together with source separated sewage offer full resource recovery enabling
recirculation of both nutrients and water. In addition the system can be designed as a net
producer of renewable and emission free energy.

Keywords: ecological waste water treatment, slow sand filtration, biogas, source separation,
nutrient re-circulation, waste water reuse, waste to resource, soil erosion, soil fertility,
desertification, deforestation, eutrophication, global warming, appropriate technologies,
anaerobic process.
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ACRONYMS

BOD Biochemical oxygen demand
COD Chemical oxygen demand
CW Constructed wetland
EPDM Ethylene propylene diene monomer rubber
FWS Free water surface
GRP Glass fibre reinforced plastic
IWESS Integrated water energy and sanitation solution
MDG Millenium development goals
NTU Nephelometric turbidity units
PE Poly ethylene
RWH Rain water harvesting
SSF Slow sand filtration
TS Total solids
TSS Totally suspended solids
VS Volatile solids
WSP Waste stabilization pond

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This study has been carried out within the framework of the Minor Field Studies Scholarship
Programme, MFS, which is funded by the Swedish International Development Cooperation
Agency, Sida.

The MFS Scholarship Programme offers Swedish university students an opportunity to
carry out two months’ field work, usually the student’s final degree project, in a country
in Africa, Asia or Latin America. The results of the work are presented in an MFS report
which is also the student’s Master of Science Thesis. Minor Field Studies are primarily
conducted within subject areas of importance from a development perspective and in a
country where Swedish international cooperation is ongoing.
The main purpose of the MFS Programme is to enhance Swedish university students’
knowledge and understanding of these countries and their problems and opportunities.
MFS should provide the student with initial experience of conditions in such a country.
The overall goals are to widen the Swedish human resources cadre for engagement in
international development cooperation as well as to promote scientific exchange
between unversities, research institutes and similar authorities as well as NGOs in
developing countries and in Sweden.

The International Office at KTH, the Royal Institute of Technology, Stockholm, administers
the MFS Programme for the faculties of engineering and natural sciences in Sweden.

Sigrun Santesson
Programme Officer
MFS Programme

International Office, MFS
KTH, SE-100 44 Stockholm. Phone: [phone]. Fax: [phone]. E-mail: [email protected]
www.kth.se/student/utlandsstudier/examensarbete/mfs
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Acknowledgements

Mr. Wycliffe Odhiambo Osumba, Kendu Bay SDA Hospital, Kenya
Mr. Erick Agembe with staff, business manager, Kendu Bay SDA Hospital, Kenya
Dr. Odira Patts M. Akumu, University of Nairobi, Kenya
Mr. Orodi Odhiambo, University of Nairobi, Kenya
Mr. Paul Mboya, University of Nairobi, Kenya
Mr. Justin Onyango, University of Nairobi, Kenya
Mr. Björn Martén, GEIST, Sweden
Mr. Jørgen Løgstrup, Transform Danish Root Zone, Denmark
Mr. Folke Günther, Holon Ecosystem, Sweden
Mr. Per Hellström, University of Skövde, Sweden
Mrs. Karin Ekman, University of Skövde, Sweden
Prof. Gunnel Dalhammar, KTH the Royal Institute of Technology, Sweden
Ms. Sigrun Santesson, KTH the Royal Institute of Technology, Sweden

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Table of contents

Abstract ...................................................................................................................................... i 
ACRONYMS ............................................................................................................................ ii 
Acknowledgements .................................................................................................................. iv 
Table of contents ....................................................................................................................... v 
1 Introduction ........................................................................................................................... 1 
1.1  Background ................................................................................................................ 1 
1.2  Objectives ................................................................................................................... 2 
2  Current sanitary waste management, disadvantages and appropriate improvements
3 
2.1  The drop and store principle ....................................................................................... 3 
2.2  The Flush and discharge/MIFSLA system principle .................................................. 4 
3 IWESS - Integrated Water Energy and Sanitation Solution ............................................ 6 
3.1 An IWESS design for the Lake Victoria basin, Kenya .................................................... 6 
4 Biogas system for the IWESS concept ................................................................................. 9 
4.1 Biogas plants made for the third world ............................................................................ 9 
4.2 Individual Benefits ......................................................................................................... 10 
4.2.1 Removal of waste .................................................................................................... 10 
4.2.1.1 Bacteria ................................................................................................................ 10 
4.2.1.2 Virus ..................................................................................................................... 11 
4.2.1.3 Fungi .................................................................................................................... 11 
4.2.1.4 Parasitic protozoa and helminths ........................................................................ 11 
4.2.1.5 Odour ................................................................................................................... 11 
4.2.2 Energy ..................................................................................................................... 11 
4.2.3 Effluent .................................................................................................................... 12 
4.3 Biogas in an integrated system ....................................................................................... 13 
4.4 Pilot site in Kendu Bay, Kenya ...................................................................................... 14 
4.4.1 Background ............................................................................................................. 14 
4.4.2 Overview of plant .................................................................................................... 14 
4.4.3 Operation ................................................................................................................. 14 
4.4.3.1 Start-up Procedure ............................................................................................... 14 
Start-up procedure of the pilot plant ................................................................................ 15 
4.4.3.2 Feeding ................................................................................................................. 16 
Kitchen waste ................................................................................................................... 16 
Toilet waste ...................................................................................................................... 16 
4.4.3.3 Feeding of the pilot plant ..................................................................................... 17 
4.4.3.2 Calculated loading rate for pilot plant ................................................................ 20 
4.4.5 Construction materials and methods ....................................................................... 20 
4.4.5.1 Plastic ................................................................................................................... 20 
HDPE ............................................................................................................................... 21 
Plastic Welding ................................................................................................................ 21 
4.4.5.2 EPDM-rubber ....................................................................................................... 21 
4.4.6 Detailed description ................................................................................................. 22 
4.4.6.1 Latrine .................................................................................................................. 22 
4.4.6.2 Mixing chamber .................................................................................................... 22 
4.4.6.3 Digester ................................................................................................................ 23 
4.4.6.4 Storage bladder .................................................................................................... 24 
4.4.6.5 Distribution of Gas and Water Seals .................................................................... 25 
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4.4.6.6 Stove ..................................................................................................................... 25 
4.4.6.7 Insulation .............................................................................................................. 26 
Cradle with walls ............................................................................................................. 26 
Roof .................................................................................................................................. 26 
Bags of grass .................................................................................................................... 27 
4.4.7 Measuring modifications and analyses ................................................................... 27 
4.4.9 Performance of the pilot plant ..................................................................................... 27 
4.4.9.1 Overall .................................................................................................................. 27 
4.4.9.2 Latrine .................................................................................................................. 28 
4.4.9.3 Mixing chamber .................................................................................................... 28 
4.4.9.4 Digester ................................................................................................................ 28 
4.4.9.5 Storage bladder .................................................................................................... 29 
4.4.9.6 Distribution of Gas and Water Seals .................................................................... 29 
4.4.9.7 Stove ..................................................................................................................... 29 
4.4.9.8 Roof ...................................................................................................................... 29 
4.4.9.9 Cradle with walls ................................................................................................. 30 
5 Design and construction of the Kendu SDA Hospital Pilot SSF wetland system .......... 31 
5.1 Introduction .................................................................................................................... 31 
5.1.1 Background ............................................................................................................. 31 
5.1.2 Objectives ................................................................................................................ 32 
5.2 Design and construction of the Kendu SDA Hospital Pilot SSF wetland system. ......... 32 
5.2.1 Introduction ............................................................................................................. 32 
5.2.1.1 Background .......................................................................................................... 32 
5.2.1.2 Objectives ............................................................................................................. 33 
5.2.2 Waste water Source details ..................................................................................... 33 
5.2.2.1 Design flow meassurement ................................................................................... 33 
5.2.2.2 Chemical analysis ................................................................................................ 34 
5.2.3 Process/physical design ........................................................................................... 35 
5.2.3.1 Site selection ......................................................................................................... 35 
5.2.3.2 Basin lining .......................................................................................................... 35 
5.2.3.3 Substrate ............................................................................................................... 36 
Substrate choices/ availability ......................................................................................... 36 
5.2.3.4 Macrophytes, Bamboo .......................................................................................... 40 
5.2.3.5 Airation tubes/natural airation ............................................................................ 42 
5.2.3.6 Calculating wetland surface-area ........................................................................ 43 
5.2.3.7 Aspect ratio configuration .................................................................................... 45 
5.2.3.8 Theoretical hydraulic retention time .................................................................... 47 
5.2.3.9 Hydrological budget ............................................................................................. 47 
5.2.4 Physical design/construction of pilot system .......................................................... 48 
5.2.4.1 Grey water separation and conveyance ................................................................ 48 
5.2.4.2 Basin construction ................................................................................................ 49 
5.2.4.3 Inlet structures ...................................................................................................... 50 
5.2.4.4 Substrates ............................................................................................................. 52 
5.2.4.5 Outlet structures ................................................................................................... 52 
5.2.4.6 Airation tubes ....................................................................................................... 53 
5.2.4.7 Sampling tubes ..................................................................................................... 53 
5.2.4.8 Planting ................................................................................................................ 54 
5.2.5 Costs ........................................................................................................................ 54 
6 Small scale decentralised slow sand filtration for the IWESS concept .......................... 57 
6.1 Introduction .................................................................................................................... 57 
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6.1.1 Background ............................................................................................................. 57 
6.1.2 Objectives ................................................................................................................ 58 
6.2 Introduction to slow sand filtration ................................................................................ 58 
6.2.1 System dimensioning .............................................................................................. 59 
6.2.2 The characteristics of the sand ................................................................................ 64 
6.3 SSF maintenance and operation ..................................................................................... 66 
6.4 Pre-treatment of raw water ............................................................................................. 67 
6.4.1 Roughing filters ....................................................................................................... 67 
6.4.2 Chemically enhanced coagulation/flocculation/sedimentation ............................... 68 
6.5 Areas of use/applications for traditional SSF systems ................................................... 69 
6.6 Limitations of traditional SSF systems .......................................................................... 69 
6.7 The PT SCX system solution ......................................................................................... 70 
The decentralised out reaching water purification system ............................................... 70 
6.8 Initial evaluation in Kendu bay, Kenya. ......................................................................... 71 
6.8.1 Surface water quality ............................................................................................... 71 
6.8.2 System appropriateness/sustainability in relation to operation and maintenance ... 73 
6.8.3 Local financial survey ............................................................................................. 74 
6.9 Second prototype evaluation .......................................................................................... 75 
6.10 PT SC(X) system principle description ........................................................................ 76 
6.11 PT 2000SCX system production capacity .................................................................... 77 
6.12 Operation scheme ......................................................................................................... 77 
6.13 System cost and cost recovery plan .............................................................................. 79 
6.14 Further development .................................................................................................... 80 
6.15 The PT SCX system role in the IWESS principle. ....................................................... 81 
7  Conclusions and recomendations .................................................................................. 82 
8  References ....................................................................................................................... 85 
Appendix A ............................................................................................................................. 89 
Appendix B .............................................................................................................................. 95 

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