DESIGN OF A RECIRCULATING HYDROPONICS SYSTEM FOR A …ebe.uonbi.ac.ke/sites/default/files/cae/engineering/ebe/Kahehu... · university of nairobi school of engineering department of

UNIVERSITY OF NAIROBI SCHOOL OF ENGINEERING

DEPARTMENT OF ENVIRONMENTAL AND BIOSYSTEMS ENGINEERING

PROJECT TITLE:

DESIGN OF A RECIRCULATING HYDROPONICS SYSTEM FOR A TOMATO GREENHOUSE

(A CASE STUDY OF HM CLAUSE FARM IN NANYUKI, KENYA)

CANDIDATE NAME: KAHEHU CHRISTINE WAIRIMU

CANDIDATE REG.No.: F21/1700/2010

SUPERVISOR’S NAME: MR. J.O AGULLO

A Report Submitted in Partial Fulfillment for the Requirements of the Degree of Bachelor of Science in Environmental and Biosystems Engineering, of the University Of Nairobi

MAY, 2015

FEB 540: ENGINEERING DESIGN PROJECT 2014/2015 ACADEMIC YEAR

UON, B.Sc. Engineering Design Project by: F21/1700/2010 i

Declaration

I declare that this engineering project design is my work and has not been submitted for a degree

program in any other university.

SIGNATURE: DATE:

KAHEHU CHRISTINE WAIRIMU

This engineering project design has been submitted for examination with my approval as

University supervisor.

SIGNATURE: DATE:

MR. J.O.AGULLO

UON, B.Sc. Engineering Design Project by: F21/1700/2010 ii

Dedication

This design project is dedicated to my mum Mrs. Teresia Naserian Naimodu, My sister Catherine

Njeri Kahehu, and My brother Timothy Mwangi for always believing in me and for their tireless

encouragement, support and prayers. I also dedicate this project to my Uncle, Kennedy

Konchella who once told me that the “sky is the limit” and to my late father James Mwathi

Kahehu from whom I got the inspiration to take on a career in Engineering.

UON, B.Sc. Engineering Design Project by: F21/1700/2010 iii

Acknowledgement I am immensely grateful to the Almighty God for his guidance throughout the project design and

also having kept me this far in the pursuit of my career.

I would especially like to express my sincere gratitude to my supervisor at University of Nairobi,

Environmental and Bio-systems Engineering Department, Mr. J.O Agullo for his support,

guidance, encouragement, positive criticism that contributed to the preparation of this report. I

thank him for his patience in providing assistance despite his busy schedule.

I would also like to thank all my lecturers and technicians from who have patiently taught me the

Engineering Discipline.

I am very grateful to Engineer Rono of Irrico International Ltd for providing all the information

that was helpful for the design process. I am also thankful to all the staff of Irrico International

for their support and concern during the design process. I am grateful to HM Clause Co. for

allowing me to have their farm as a case study and for their support throughout the design

project.

In conclusion, I extend my sincere thanks to my family, colleagues and friends for their constant

encouragement, prayers and best wishes.

UON, B.Sc. Engineering Design Project by: F21/1700/2010 iv

Abstract

Green house soils are prone to acidity, salinity and root borne diseases. This is due to the reuse of

the soils season in season out which results in lack or limited availability of nutrients for the

crops. This reduces the yield of the crop. With the increasing adoption of the greenhouses in

Kenya due to the controlled environment achieved in the greenhouses, soil problems are a major

setback. One way of alleviating these problems is to adopt hydroponics which isolates the crop

from the soil. Hydroponics is a technology for growing plants in nutrient solutions (water and

fertilizers) with or without the use of artificial medium (e.g. sand, gravel, vermiculite, rockwool,

peat, coir, sawdust). The site of this engineering project was Nanyuki which has black cotton

soils thus poor drainage on irrigating resulting to loss of the plant due to root rot. These soils also

crack when dry exposing the plant roots thus loosing the crop thus hydroponics would provide

the ultimate solution. This project sought to increase the crop yield and also offer environmental

management strategy by recirculating nutrient solution in the hydroponics system.

The objective of this project was to design a recirculating hydroponics system for a 3 hectare

green house intended to grow tomatoes at HM Clause farm located in Nanyuki, Kenya. The

specific objectives were to identify pertinent parameters required in the design of a recirculating

hydroponics system, sizing the system components using the pertinent parameters and finally to

carry out a cost benefit analysis of the design.

The methodology involved a feasibility study, data acquisition and sizing system parameters.

Feasibility study involved the consideration of the yield of hydroponics as compared to open

field, the amount of fertilizer that is recycled and also by analyzing the demand of tomatoes.

Some of the data that was considered was the geology of the area which was determined from

existing documents of the Kenya Soils survey, climatic data which was obtained from ClimWat

and crop data which was obtained from CropWat. Observations were made at the site in order to

determine the layout of the hydroponic troughs. In sizing the system parameters various

equations such as volume, discharge, crop water requirement and Hazen William’s equations

were used. Softwares such as the Google earth, hydro calc, were also used in the design project.

The pertinent parameters were identified which included the crop data i.e. tomato planting

spacing which is 20cm x 20cm and the crop water requirement which was 5mm/day. The total

flow required for each section of the blocks of the farm was determined as 25.344m3/hr for the 3

UON, B.Sc. Engineering Design Project by: F21/1700/2010 v

bay sections and 8.448m3/hr for the 1 bay sections using the total drip line length. This flow was

used in Hydro calc to determine the size of the multi-mains i.e. a main line for each section and

the sub-mains, select the pump for a total head of 45.84m, size valves to control the flow to each

section and also in the selection of gravel filters, media filters and U.V. cylinders. The irrigation

tank was sized depending on the discharge per section and also the irrigation schedule. The

irrigation schedule was obtained as 12.12min/day/section. The irrigation tanks were obtained as

steel tanks of 150m3 sized to 2.5 days of irrigation. The fertigation system was sized to

fertigation requirement of 5L/m3. The drainage system was sized depending on the flow drained

per trough which was 211.2lph. The capacity of the drainage tank was obtained as 10,000L. The

booster pump that was placed in the drainage tank was selected to a head of 34.08m and a

discharge of 5m3/hr. The treated water tank was sized to 15 days thus tank capacity was found to

be 150m3. Design drawing of the irrigation, hydroponics and drainage collection and

recirculation were produced. The cost of materials of the hydroponics system was found to be

Ksh.13, 195,838.26.

The hydroponics system will enable the production of consistent high yield of tomatoes. This

will in turn result in high returns to the farmer in that the farmer will be able to cater for the cost

of the installation of the system within a year of tomato production and sales. The effect will be

the reduction of the cost of tomatoes to consumers. In general the livelihood of Kenyans would

improve since with increased tomato production and even other vegetables there is increased

food security.

UON, B.Sc. Engineering Design Project by: F21/1700/2010 vi

Table of Contents

Declaration ....................................................................................................................................... i

Dedication ....................................................................................................................................... ii

Acknowledgement ......................................................................................................................... iii

Abstract .......................................................................................................................................... iv

LIST OF TABLES ......................................................................................................................... ix

LIST OF FIGURES ........................................................................................................................ x

1.0 INTRODUCTION ............................................................................................................... 1

1.1 Background ...................................................................................................................... 1

1.2 Statement of the problem and problem analysis .............................................................. 5

1.3 Justification ...................................................................................................................... 6

1.4 Site analysis and inventory ............................................................................................... 7

1.5 Objectives ....................................................................................................................... 12

1.6 Statement of Scope ......................................................................................................... 12

2.0 LITERATURE REVIEW .................................................................................................. 13

2.1 Brief History of Hydroponics ......................................................................................... 13

2.2 Hydroponics Technology ............................................................................................... 13

2.3 Benefits of Hydroponics Systems .................................................................................. 14

2.4 Types of Hydroponics Systems ...................................................................................... 16

2.4.1 Closed Hydroponic Systems ................................................................................... 16

2.4.2 Open Hydroponic Systems .......................................................................................... 17 2.5 Open versus closed hydroponics systems ...................................................................... 17

2.6 Fertigation ...................................................................................................................... 18

2.6.1 Fertigation Approaches ........................................................................................... 19 2.6.2 Fertigation Systems ...................................................................................................... 19

2.7 Treatment of Irrigation Water ........................................................................................ 22

2.7.1 Pre-treatment or Filtration............................................................................................ 22

2.7.2 Treatment of Irrigation water to remove pathogens .................................................... 24 2.8 Recirculating Hydroponics system................................................................................. 27

2.9 Design of Irrigation and Drainage lines ......................................................................... 30

2.10 Irrigation Hydrants ..................................................................................................... 31

2.11 Pump Selection ........................................................................................................... 32

2.12 Softwares used in the product design of this project .................................................. 33

2.12.1 CROPWAT 8.0 .......................................................................................................... 33 2.12.2 CLIMWAT 2.0 .......................................................................................................... 34

UON, B.Sc. Engineering Design Project by: F21/1700/2010 vii

2.12.3 HydroCalc .................................................................................................................. 34 3.0 THEORETICAL FRAMEWORK ..................................................................................... 36

3.1 Evapo-transpiration (ETO) .............................................................................................. 36

3.2 Crop water requirement .................................................................................................. 37

3.3 Net Irrigation Requirement (NIR) .................................................................................. 38

3.4 Gross Irrigation Requirement (GIWR) .......................................................................... 39

3.5 Irrigation Scheduling ...................................................................................................... 39

3.6 Calculation of head losses n the pipes by Hazen Williams equations ........................... 41

3.7 Crop electrical conductivity and Ph requirements for fertigation unit ........................... 42

3.8 Pump Design .................................................................................................................. 43

3.9 Drip Irrigated Hydroponics Design .................................................................................... 45

4.0 METHODOLOGY ............................................................................................................ 47

4.1 Feasibility Study ............................................................................................................. 47

4.2 Data Acquisition ............................................................................................................. 47

4.3 Assessment of Existing Greenhouse .............................................................................. 48

4.4 Sizing of System Components ....................................................................................... 48

4.4.1 Selection of drip lines and hydroponic troughs ...................................................... 48

4.4.2 Determination of hydroponic Layout ...................................................................... 48 4.4.3 Sizing the irrigation lines ........................................................................................ 48 4.4.4 Sizing the valves or hydrants ....................................................................................... 49

4.4.5 Selecting Irrigation Pump, filters and U.V cylinders ................................................... 50 4.4.6 Sizing and selection of the fertigation system ............................................................. 50

4.4.7 Sizing the tank for Irrigation ........................................................................................ 51 4.4.8 Sizing the Drainage system .......................................................................................... 51

4.4.9 Sizing the Drainage tank .............................................................................................. 52 4.5.0 Sizing the recirculation System ................................................................................... 52 4.5.1 Sizing the treated water tank ........................................................................................ 53

4.5.2 Sizing the valves for drainage water ............................................................................ 53 4.5.3 Cost benefit Analysis ................................................................................................... 53

5.0 RESULTS AND DISCUSSION ........................................................................................ 55

5.1 Design Criteria .................................................................................................................... 55

5.2 Identification of pertinent parameters ................................................................................. 56

5.2.1 Selecting the drip lines from manufacturer’s catalogue .............................................. 58

5.2.2. Flow required per fertigation zone/section ................................................................. 59 5.2.3 Time clock Irrigation scheduling ................................................................................. 60 5.2.4 Fertigation Requirements ............................................................................................. 61

5.3 Design of main lines, sub-mains and valves ....................................................................... 62

5.3.1 Sizing of the sub-mains ................................................................................................ 62

5.3.2 Sizing of the main line ................................................................................................. 64 5.3.3 Sizing of the irrigation hydrants or valves ................................................................... 65

5.4 Selecting the Irrigation Pump ............................................................................................. 66

5.5 Selecting the irrigation water U.V. cylinders and Filters.................................................... 66

UON, B.Sc. Engineering Design Project by: F21/1700/2010 viii

5.6 Sizing the fertigation system ............................................................................................... 67

5.7 Tank sizing for Irrigation .................................................................................................... 68

5.8 Sizing of the drainage system ............................................................................................. 68

5.8.1 Sizing of the outlet of the troughs to the drainage pipe ............................................... 68

5.8.2 Sizing the drainage pipe for the blocks vertical and across where the drain water is

directed to a drain tank .......................................................................................................... 69 5.8.3 Sizing the Drainage tank .............................................................................................. 71

5.9 Design of the recirculation System ..................................................................................... 71

5.9.1BoosterDrainage Pump selection .................................................................................. 72 5.9.2 Selecting media filter for drain water .......................................................................... 73 5.9.3 Selecting of U.V. Cylinders for drain water ................................................................ 73 5.9.4. Sizing the treated water tank ....................................................................................... 73

5.9.5 Selecting of injection valves ........................................................................................ 73 5.10 Cost benefit Analysis ........................................................................................................ 74

5.11 Design Drawing ................................................................................................................ 76

6.0 CONCLUSION AND RECOMMENDATIONS .............................................................. 78

7.1 Conclusions ......................................................................................................................... 78

7.2 Recommendations ............................................................................................................... 79

7.0 REFERENCES .................................................................................................................. 81

8.0 APPENDICES ................................................................................................................... 85

9.1 Appendix A .................................................................................................................... 85

9.2 Appendix B .................................................................................................................... 91

9.3 Appendix C .................................................................................................................. 103

9.4 Appendix D .................................................................................................................. 106

UON, B.Sc. Engineering Design Project by: F21/1700/2010 ix

LIST OF TABLES

Table 1: Hydroponic Production in various countries ................................................................... 2

Table 2: Climate data for Nanyuki .................................................................................................. 8

Table 3: Coordinates of the points of the farm along the outside boundary of the farm as shown

on the google earth image in site analysis .................................................................................... 57

Table 4: Rainfall data from ClimWat, (2015) ............................................................................... 58

Table 5: Nutrient required at each stage growth of a tomato plant. Source: Pelemix’s experience,

Fertigation on wikipedia ............................................................................................................... 62

UON, B.Sc. Engineering Design Project by: F21/1700/2010 x

LIST OF FIGURES

Figure 1: Location of Nanyuki Kenya Source: Google images ...................................................... 7

Figure 2: Location of Nanyuki Kenya ............................................................................................ 7

Figure 3: Existing Greenhouse structure taken during a visit to the Nanyuki Farm, (2015) .......... 9

Figure 4: Aerial location of the 3ha farm. Source: Google Earth ................................................. 10

Figure 5: Layout of HM Clause farm, (2015) ............................................................................... 11

Figure 6: Fertigation Injectors. Source: Pressurized irrigation techniques, FAO 2015 ................ 21

Figure 7: Fertigation Systems. Source: Google images on fertigation systems ........................... 22

Figure 8: Media filters e.g. gravel filters. Source: Google images. .............................................. 24

Figure 9: A chlorine injection system. Source: Van der Gulik. T, 2003. .................................... 25

Figure 10: A pilot scale UV disinfection system. Source: Van der Gulik. T, 2003. ................... 26

Figure 11: Ultraviolet treatment unit. Source: Van der Gulik. T, 2003. ....................................... 27

Figure 12: Typical layout of a (hydroponics) substrate soilless growing system. Source: Pardossi,

(2011). Fertigation and Substrate Management in Closed Soilless Culture. Pg.45 ...................... 28

Figure 13: Fertigation Scheme option 1 Source: Pardossi, (2011). Fertigation and Substrate

Management in Closed Soilless Culture. Pg.47 ............................................................................ 29


Management in Closed Soilless Culture. Pg.50 ............................................................................ 29

Figure 15: Hydroponics troughs layout with 2 drip lines per trough. Source: Irrico International

Ltd Images .................................................................................................................................... 30

Figure 16: Automatically operated hydrant. Source: Google images. .......................................... 31

Figure 17: Manually operated hydrant. Source: Google images. ................................................. 32

Figure 18: Valve Source: Google images ..................................................................................... 32

Figure 19: Conceptual framework of irrigation scheduling in soilless culture. Source: Pardossi,

(2011). Fertigation and Substrate Management in Closed Soilless Culture. Pg.28 ...................... 40

Figure 20: Total Pump head for an Irrigation system. Source Google images ............................. 45

Figure 21: Generation of Concept Design .................................................................................... 54

Figure 22: Crop water requirement from CropWat, (2015) .......................................................... 57

Figure 23: Summary of the bill of quantities attached in the Appendix D ................................... 75

Figure 24: Irrigation layout ........................................................................................................... 76

Figure 25: A.1 Sub-mains layout .................................................................................................. 85

Figure 26: A.2 Hydroponics Layout ............................................................................................. 86

UON, B.Sc. Engineering Design Project by: F21/1700/2010 xi

Figure 27: A.3 Fertigation Layout ................................................................................................ 87

Figure 28: A.4 Drainage Collection .............................................................................................. 88

Figure 29: A.5 Hydrant fittings ..................................................................................................... 89

Figure 30: A.6 Reservoir fittings .................................................................................................. 90

Figure 31: B.1 Drip line selection ................................................................................................. 91

Figure 32: B.2 pressure head along the sub-main for 3 bay section that was used in the design of

the sub-main .................................................................................................................................. 92

Figure 33: B.3 pressure head used in design of sub-main for 1 bay section................................. 93

Figure 34: B.4 pressure head used in the mainline design ............................................................ 94

Figure 35: B.5 pressure head used in the design of trough drainage pipe .................................... 95

Figure 36: B.6 pressure head used in the design Block drainage 1 .............................................. 96

Figure 37: B.7 pressure head used in the design of Block drainage 2 .......................................... 96

Figure 38: B.8 pressure head used in the design of main drainage pipe 1 .................................... 97

Figure 39: B.9 pressure head used in the design of main drainage pipe 2 .................................... 97

Figure 40: B.10 pressure head used in the design of the main drainage pipe 3 ............................ 98

Figure 41: B.11 pressure head used in the design of the main drainage pipe 4 ............................ 98

Figure 42: B.12 pressure head used in the design of the pipe that directs drainage water to treated

water tank ...................................................................................................................................... 99

Figure 43: B.13 Kc for tomatoes................................................................................................. 100

Figure 44: B.14 Etc requirement ................................................................................................. 100

Figure 45: B.15 Climatic data ..................................................................................................... 101

Figure 46: B.16 Irrigation Pump specifications .......................................................................... 101

Figure 47: B.17 Drainage pump specifications........................................................................... 102

Figure 48: C.1 FERTIJET, Source: Google Images on fertigation ............................................. 103

Figure 49: C.2 GALCON CONTROLLER, Source: Google images on Galcon controller ....... 103

Figure 50: C.3 Greenhouse structure on site ............................................................................... 104

Figure 51: C.4 Inside of Greenhouse structure on site................................................................ 104

Figure 52: C.5 Rain water harvesting reservoir .......................................................................... 105

Figure 53: D.1 BOQ for Drip irrigation ...................................................................................... 106

Figure 54: D.2 BOQ for Fertigation and Controllers .................................................................. 107

Figure 55: D.3 BOQ for hydroponic troughs .............................................................................. 108

Figure 56: D.4 BOQ for Recirculation and UV Treatment ........................................................ 109

Figure 57: D.5 BOQ for UV treatment ....................................................................................... 110

UON, B.Sc. Engineering Design Project by: F21/1700/2010 xii

Figure 58: D.6 BOQ for Drainage collection.............................................................................. 111

UON, B.Sc. Engineering Design Project by: F21/1700/2010 1

1.0 INTRODUCTION

1.1 Background

Recent global trends in hydroponics indicate that commercial hydroponics industry has grown

four to five times in the last decade. The area under hydroponics is currently approximated to be

between 20,000 and 25,000 ha with a farm gate value ranging between 6 and 8 billion USD. The

rapid growth is as a result of the quality of the product more than the fact that the product is

hydroponically grown. The Dutch are the world leaders in commercial hydroponics as

hydroponics accounts for 50% of the value of all fruit and vegetables produced in the country

(Carruthers, 2002). The hydroponic production area is about 10,000 ha. The industry was

necessitated by widespread soil depletion, a build- up of soil disease, salinization, high water

tables and favorable economic returns. Globally, the crops that are grown hydroponically are the

most important commercial crops and they are limited in number. They include tomatoes,

cucumbers, lettuce, capsicum and cut flowers. Hydroponics has in time embraced Integrated Pest

Management and is moving away from run-to-waste systems with their potential for

environmental problems.

Food safety is pertinent to Industries and governments all over the world and the harmonization

of agricultural production systems with the environment, thus production of food in enclosed

hydroponic production systems seems to offer many advantages. These systems offer hygienic

production of food. These systems also recycle more than 95% of the water used, thus the

hydroponics and greenhouse industry is renowned for low water use compared to other

agricultural and horticultural sectors. The adaption of recycling systems is however limited with

most farmers still using run-to- waste systems that have minimal disease problems. The yield in

closed and open systems has been proven to be the same for both and therefore the challenge is

to save on resources. The Netherlands hydroponics industry is miles ahead and therefore it is the

perfect model to strategically analyze the different hydroponics systems obtaining the pros and

cons from their experiences. The Netherlands has the most developed hydroponic and

greenhouse industry in the world thus best reference point.


Hydroponic production in various countries such as the Netherlands, Spain, Italy, Japan, Israel,

UK, USA, Canada, New Zealand and Australia is shown in the Table 1.

Table 1: Hydroponic Production in various countries

Country Date Area

(Ha)

Main Systems Major crops

The

Netherlands(Ho

lland)

1987 3,500 Rockwool and

other media

based systems

Tomato, Cucumber, Capsicum, Eggplant,

Cut flowers, Beans, Lettuce

2001 10,000 Rockwool Tomato, Cucumber, Capsicum, Eggplant,

strawberry, lettuce, chrysanthemum,

freesia, camation

Spain 1996 1,000 Perlite, sand, Lettuce, cucumber, capsicum,

2001 4,000 Rockwool Tomatoes

Canada 1987 100 Rockwool, Tomato, cucumber, lettuce

2001 1,574 Sawdust, NFT,

Rockwool,

perlite

Tomato, cucumber, capsicum

France 1996 1,000 Rockwool Cucumber, capsicum, tomato, eggplant,

cut flowers

Japan 1984 293 Water, rockwool

and NFT

Honewort, tomato, leaf onion, lettuce,

musk melon, cucumber

Israel 1996 650 Scoria, perlite,

sand, Aeroponics

Belgium 1996 600 Rockwool

Germany 1996 650 Rockwool

New Zealand 1996 200 NTF, Pumice, Cut flowers, strawberry,

2001 660 Sawdust Tomato, capsicum, cucumber, lettuce,

melon chilies, Asian vegetables

Australia 1996 500 NFT, rockwool,

sawdust, sand,

scoria, perlite

Tomatoes, lettuce, cucumbers, cut

flowers, herbs, strawberry

United

Kingdom

1988 392 Rockwool Tomato, cucumber, capsicum


South Africa 1984 75 Various media, Tomato, cucumber, lettuce,

1996 420 Sawdust & bark Flowers

Italy 1990 60 Roses, tomato, gerbera,

1999 400 Strawberry

USA 1984 228 Perlite, gravel, Tomato, cucumber, lettuce

1999 400 Sand, NTF

Finland 1996 370

Korea 1987 274 NFT, rockwool Tomato, cucumber, lettuce

1996 Perlite, NFT,

DFT, rockwool,

Aeroponics

Mexico 1996 15

1999 120

China 1987 5 Gravel bed Tomato, cucumber, lettuce, melon,

capsicum, pak choi, chive, flowers

Greece 1996 33 Rockwool,

perlite,

Tomato, cucumber, capsicum,

1999 60 NFT Lettuce

Brazil 1999 60 NFT Lettuce, arugula, water cress

Taiwan 1996 36

Singapore 1996 30 Aeroponics,

NFT

Total Production

Late 1980's - 5,000 to 6,000 ha

2001 - 20,000 to 25,000 ha

Source: Steven Carruthers, (2002). Hydroponics as an agricultural production system –Issue 63


Hydroponic farming utilizes 80% less water than conventional soil farming thus is a solution to

food production in the midst of changing climatic conditions in Africa. Drought and famine that

has resulted in food insecurity is heavily felt in the continent especially with the growing

population. In Kenya reduced farming acreage, soil problems and changing climatic conditions

have seen hydroponics as the trend in farming. The technology is fast gaining ground especially

in central Kenya. It’s a major boost to the Agricultural sector and is helping fight hunger and

poverty in the area. In central Kenya, where a majority of farmers own less than an acre of land,

the hydroponic system is renewing the hopes of many people who want to embark on farming

but are prohibited by the size of their land (Ngamau, 2013). Ngamau applauds the system as

cheap, efficient and highly productive and also claims that the final yields compensate the

challenges encountered in running the system.

Peter Chege one of the pioneers of hydroponic farming in Kenya has managed to train numerous

farmers in Kenya and Uganda on the intricacies of hydroponics on his farm thus the venture has

improved his financial status. The USAID has taken the front line under Feed the Future program

to support the hydroponics technology in Kenya. Under the program technology transfer is a

method used around the world to enlighten small scale farmers on effective technologies that can

be used on their farms such as hydroponics and thus transforming them from subsistence to

commercial enterprises. These efforts are seen when the USAID funded Rose Chelang’at

hydroponic farm in Kericho County a sum of USD 113. A hydroponics system is required to

have a recirculating system that encompasses the treatment unit in order to achieve the efficiency

and benefits therein. Some hydroponics systems are implemented in Kenya without the

recirculating aspects and this in turn results in waste of water and nutrients. The exceptions i.e.

the systems that have recirculating systems include the Lake Flower company in Kihoto estate

Naivasha and its neighbouring flower companies among others. The recirculating system is

costly and most farms in Kenya may not have it but it is essential.

HM clause farm in Nanyuki practices greenhouse farming for tomatoes on a commercial scale. It

utilizes greenhouse tunnels and heaped soils inside the greenhouse as the growing area. Nanyuki

soils which are also the greenhouse soils are black soils and thus water logged conditions occur


resulting in loss of the crops. There is also risk of the soils becoming unfavourable i.e. acidic due

to the large scale use of fertilizers and agro chemicals and would require that the soils be

changed at intervals. Such soils are also prone to root diseases. This project seeks to design a

recirculating hydroponics system for a greenhouse intended to grow tomatoes on a commercial

scale at HM Clause farm in Nanyuki in order to maximize on the scarce resource, water and also

manage the fertigation issues there in. It will also highlight the advantages of greenhouse

hydroponics over the conventional greenhouse that is adopted in Kenya.

1.2 Statement of the problem and problem analysis

Green house soils are prone to acidity, salinity and root borne diseases. This is due to the reuse of

the soils season in season out. Salinity and acidity result from accumulation of salts and

agrochemicals that are used in the irrigation water. Highly acidic soils prevent seed germination

and for alkaline soils seed germination may be slow or non-existent thus result in spindly plants.

Soil acidity also determines the availability of nutrients for the vegetables mostly grown in

greenhouses. In alkaline soils, phosphorous, iron and zinc are limited. In acidic soils calcium and

magnesium are less available. The lack or limited availability of these nutrients results in tomato

diseases reducing the yield. High salt levels burn the crop also reducing the yield. Nanyuki has

black cotton soils thus water logged conditions thus poor drainage on irrigating resulting to loss

of the plant due to root rot. These soils also crack when dry exposing the plant roots thus loosing

the crop.

Hydroponics offers hygienic conditions, monitoring of the pH of the nutrient and the medium

thus reduced probability of diseases, salinity and acidity. Tomatoes are highly sensitive crops

and thus would do well in hydroponics. Soilless mixes contain no diseases and are light enough

to allow air movement and balanced water distribution thus water logging conditions are non-

existent. Of importance a recirculating hydroponics system is appropriate in order to conserve

water and nutrients .Open hydroponic systems are prone to loss of water and nutrients with

environmental pollution i.e. pollution of ground water when waste nutrient solution is drained.

These systems resemble conventional open field agriculture in excessive water and nutrient

consumption.


In a recirculating irrigation system, drain water is treated to destroy pathogens and disease

causing organisms then recycled back to the irrigation laterals. The system prevents leaching of

drain water from greenhouses into the ground which pollutes ground water. The amount of water

and nutrients lost is greater on a commercial scale thus recycling is more viable.

1.3 Justification

The yield of tomatoes in hydroponics is 100 times more than the yield of tomatoes in open field

farming. Mbaka, et.al, 2013 also stated that in the past decade, tomato has gained importance as

an income generating crop in high potential and peri-urban areas. He also stated that the crop

was ranked first in a prioritization of vegetable crop value chains in Kenya from Kenya

Agricultural Research Institute report of 2011. In 2011, area under production was 19,000ha,

from which 600,000Million tones valued at Ksh14.2billion were produced as given in the report

of Horticultural Crops Development Authority. Production was mainly under open field

conditions until the adoption of modified high tunnels popularly known as ‘green houses’ in the

last five years. Greenhouses provide more farming area given that arable farm sizes have been

decreasing over the years due to increasing population. The use of greenhouses is also likely to

attract trained youths to practice farming since it’s perceived to be fashionable technology. The

labour requirements are reduced in greenhouses thus civil servants can retire to farming even in

old age.

The sustainability, however, of the wide spread greenhouse tomato farming in Kenya is

threatened by soil problems and excessive loss of water and fertilizers that leach into ground

water in conventional greenhouse hence need to adopt a hydroponics system. In addition the

recirculating hydroponics system is more sustainable since in the open system there is still

massive waste of water and nutrients with environmental pollution as occurs in conventional

agriculture although the yield of tomatoes in open and recirculating hydroponics systems is the

same.


1.4 Site analysis and inventory

The site of this design was HM Clause farm located in Nanyuki, Kenya. The description of

Nanyuki was obtained from Google Wikipedia as follows. Nanyuki is a market town in Laikipia

County of Kenya lying northwest of Mount Kenya along the A2 road and at the terminus of the

branch railway from Nairobi. It is situated just north of the Equator (0° 01' North).

Figure 1: Location of Nanyuki Kenya Source: Google images

Figure 2: Location of Nanyuki Kenya

Source: Google images


Nanyuki municipality had an urban population of 31,577 in 1999. Most members of the

population earn their money through trade. Shops in the town supply many farms, ranches and

game parks in a wide circle. Climbers and backpackers visit Nanyuki on their way to or from

Mount Kenya along the Sirimon and Burguret routes and many other tourists pass through the

town. Nanyuki therefore has many hotels, of which Mount Kenya Safari Club and Sportsman’s

Arms Hotel are the most prominent and best known.

Nanyuki has some of the cleanest water in Kenya since the water supply source is a river from

Mt. Kenya. The entire water system is gravity fed, from the supply to the sewer system. The

Geology of the area consist of volcanic soils, mainly basaltic lavas from which are derived the

black soils of the Laikipia plains (Shitakha, 1986)

Table 2: Climate data for Nanyuki

Climate data for Nanyuki

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year

Average high °C

(°F)

25

(77)

26

(79)

25

(77)

23

(74)

23

(73)

23

(74)

22

(72)

23

(73)

24

(76)

24

(75)

23

(73)

23

(74)

23.7

(74.8)

Average low °C

(°F)

7

(45)

8

(47)

9

(49)

11

(51)

10

(50)

9

(48)

8

(47)

8

(47)

8

(46)

8

(47)

9

(49)

8

(47)

8.6

(47.8)

Precipitation mm

(inches)

13

(0.5)

23

(0.9)

46

(1.8)

119

(4.7)

81

(3.2)

50

(2)

69

(2.7)

66

(2.6)

48

(1.9)

64

(2.5)

86

(3.4)

38

(1.5)

703

(27.7)

Source: "Weatherbase: Historical Weather for Nanyuki, Kenya". Weatherbase. 2014. Retrieved on October

31, 2014.

http://www.weatherbase.com/weather/weather.php3?s=49636&refer=wikipedia


Figure 3: Existing Greenhouse structure taken during a visit to the Nanyuki Farm, (2015)

The existing structure of the 3 ha farm greenhouse for tomato growing comprised of two units;

16 bays of 12.8m by 104m gutter length. The column height is 5m with a total height of 8.4m at

the centre and the columns are spaced at 4m apart.


Figure 4: Aerial location of the 3ha farm. Source: Google Earth

3ha

farm


Figure 5: Layout of HM Clause farm, (2015)

The greenhouse farm uses water from the main reservoir where rain water is collected. The

effective amount of rain water received in Nanyuki per year is 651.4mm per annum which is

sufficient to be harvested and used in irrigation. The rain water is harvested in an existing

reservoir in the farm of capacity 25,000m3. The water is then pumped to green house 1 as shown

in Figure 17.The demand in quantity and quality of tomatoes by the population and visitors of

Nanyuki and by the population of neighbouring cities such as Nairobi and Thika all year round

creates the need to produce quality vegetables including tomatoes in a closed hydroponic

greenhouse to achieve required tomato yield and quality. The concept implemented in the 3ha

farm can then be adopted by the farmers in the area and in Kenya.


1.5 Objectives

The overall objective of this study is to design a recirculating hydroponics system for a 3hectare

greenhouse for HM Clause farm located in Nanyuki to grow tomatoes in order to achieve

consistent high yield produce and environmental sustainability.

To achieve the above overall objective the following specific objectives have been set:

1. To identify pertinent parameters required in the design of a recirculating hydroponics

system for a greenhouse

2. To use the pertinent parameters in (1) to size the individual components of the design

3. To establish a Cost Benefit analysis of the recirculating hydroponic system.

1.6 Statement of Scope

This project sought to design a recirculating hydroponics system to minimize loss of water and

nutrients and achieve high consistent yield of tomatoes. It culminated into system components

specifications and design drawings that would enable the installation of the recirculating

hydroponics system. The hydroponics layout was determined depending on agronomists’

specifications. The irrigation and drainage layout depended on the discharge required or

expected and the slope. The design covered the sizing and selection of pumps, hydroponic

troughs, pipes and laterals depending on the crop water requirement, over-irrigation to prevent

accumulation of salts, and the irrigation scheduling. The drain water tank, UV treatment unit and

the treated storage water tank were sized according to the amount of drain water from each

trough. The amount of water and nutrients recycled was used to establish the efficiency of the

system. The constraint encountered was the availability of manufacturer’s catalogue in order to

select exact system components.


2.0 LITERATURE REVIEW

2.1 Brief History of Hydroponics

The use of solution culture for agricultural production was introduced to the public in 1929 by

William Frederick Gericke of the University of California. He grew tomato vines twenty-five

feet high in his backyard in mineral nutrient solutions rather than soil. In 1937 Gericke termed

the technology hydroponics which would enable countries to produce more food with fewer

resources. Gericke argued concerning the World War 1 that Nations such as Italy and Japan

which were worried by crowded populations and inadequate agricultural land could easily

increase their production of food through hydroponics getting rid of the need for territorial

expansion. One of the earliest successes of hydroponics occurred on Wake Island in the Pacific

Ocean that was used as a refueling stop for Pan American Airlines. Hydroponics was used in the

1930s to grow vegetables for passengers since there was no soil on the Island and it was

expensive to airlift fresh vegetables. In the USA the hydroponics industry was driven by the fact

that greenhouse soils had to be replaced at frequent intervals or be maintained year to year by

adding large quantities of commercial fertilizers.

2.2 Hydroponics Technology

Hydroponic systems consist of a soil-free plant growing system, where a controlled nutrient-rich

solution supplies plant roots with nourishment hence maximum yield and quality of produce as

compared to open field farming, (Government of Western Australia, Department of water, 2013).

It is a broad term that includes all techniques for growing plants in solid media other than

(substrate culture) or in aerated nutrient solution (water culture).The classification of soilless

culture considers the type of substrate and container, how the nutrient solution is delivered to the

plant (drip irrigation; sub-irrigation; flowing, stagnant or mist nutrient solution culture) and the

fate of the drainage nutrient solution: open (free-drain) or closed (recirculating water) systems.

The most widely used soilless techniques are container cultivation, while water culture systems

such Nutrient Film Technique (NFT), floating culture and Aeroponics are widely used for

research work, but much less on commercial scale with some exception, (Pardossi, 2009).


Pardossi described that water culture could be used only for crops with short growing cycles,

such as leafy vegetables. He also stated that container (substrate) culture is generally used for

row crops, such as fruit vegetables (solanancea, cucurbits), strawberry and cut flowers (rose,

gerbera, anthurium, etc.). Different containers (banquette, pots, bags, slabs) are used filled with

inorganic or organic substrate, or a combination of two or three different materials, such as the

peat-perlite or peat-pumice mixture. Coco peat is a regularly used plant support medium, as it is

economical and has no harmful environmental disposal problems.

2.3 Benefits of Hydroponics Systems

Hydroponics offers significant benefits over traditional farming which have resulted in increased

farming area under hydroponic production as more people turn to hydroponics.

Hydroponics offers people the ability to grow food in places where traditional agriculture is

impossible. Bambi, 2008 describes that in areas with arid climates, like Arizona and Israel,

hydroponics has been used to expand their food production and to enjoy locally produced food.

Similarly, he states that hydroponics is useful in dense urban areas, where land acreage is

reduced. In Tokyo, hydroponics is used as a substitute of traditional soil-based plant growth.

Hydroponics is also useful in remotes locales, such as Bermuda as described by Bambi, 2008.

With so little space available for planting, Bermudians have turned to hydroponic systems, which

take around 20 percent of the land usually required for crop growth. This allows the citizens of

the island to enjoy year-round local produce without the expense and delay of importation.

Finally, areas that don't receive consistent sunlight or warm weather can benefit from

hydroponics. Places like Alaska and Russia, where growing seasons are shorter, use hydroponic

greenhouses, where light and temperature can be controlled to produce higher crop yields

(Bambi, 2008).

There are also significant environmental benefits to hydroponics use. These are described as

follows by Bambi, 2008. Hydroponics systems require only around 10 percent of the water that

soil-based agriculture requires. This is due to the fact that hydroponic systems allow recycling

and reuse of water and nutrient solutions, and the fact that no water is wasted. This can have


quite an impact on areas where water is scarce, such as in the Middle East and parts of Africa.

Similarly, hydroponics requires little or no pesticides and only around 25 percent of the nutrients

and fertilizers required of soil-based plants. This represents not only a cost savings but also

benefits the environment in that no chemicals are being released into the air. Environmental

impacts of transportation are also reduced with the adoption of the hydroponics technology. As

hydroponics allows produce to be grown locally and requires fewer areas to import their crops,

there is a reduction in both price and greenhouse gas emissions due to reduced transportation

requirements (Bambi, 2008).

Hydroponics offers us the benefit of a shorter harvest time. Plants grown in this manner have

direct access to water and nutrients and therefore, are not forced to develop extensive root

systems to allow them to find the nutrients they need. This saves time and produces healthier,

lusher (succulent, juicy plants) in about half the time as traditional agriculture (Bambi, 2008).

Research has shown that hydroponics offers exceptional advantages in that the roots of the plant

have constant access to oxygen and the plants have access to as much or as little water as they

need (Bambi, 2008). This is important as one of the most common errors when growing is over-

and under- watering; and hydroponics prevents this from occurring as large amounts of water can

be made available to the plant and any water not used, drained away, recirculated, or actively

aerated, eliminating anoxic conditions, which drown root systems in soil. In soil, a farmer needs

to be very experienced to know exactly how much water to feed the plant. Too much and the

plant will not be able to access oxygen; too little and the plant will lose the ability to transport

nutrients, which are typically moved into the roots while in solution (Bambi,2008).


2.4 Types of Hydroponics Systems

According to Smart! Grow Intelligently, 2014, there are two main types of hydroponic systems -

closed hydroponic systems and open hydroponic systems. Hydroponic systems that do not

involve growing media are usually closed systems, while hydroponic systems that involve

growing media (container plants), may be closed or open systems.

2.4.1 Closed Hydroponic Systems

Smart! Grow Intelligently, 2014 states that in closed hydroponics systems the same nutrient

solution is recirculated and the nutrient concentrations are monitored and adjusted accordingly.

Keeping the nutrient balance in such hydroponic systems is a challenge and the hydroponic

nutrient solution has to be sampled and analyzed at least once a week. The nutrient solution

composition has to be adjusted according to the results. If not managed properly, the nutrient

solution might get out of balance.

Closed hydroponic systems include both simple hydroponic systems, as well as sophisticated

ones. The following is a short brief of some of these systems according to Smart! Grow

intelligently, 2014:

Deep Water Culture (DWC) hydroponic systems - This is the most simple type hydroponic

systems. In this type of hydroponic systems plants are suspended in an oxygen-enriched nutrient

solution.

The Wick hydroponic systems - This is a passive hydroponic system, in which wicks run from

the base of the plant container down to a reservoir and draw the nutrient solution upwards.

Ebb and Flow - This is the most popular hydroponic system due to its low maintenance and low

cost. It is widely used for plug production and potted plants. In this type of system the growing

bed is flooded with nutrient solution and then it is allowed to drain. The duration and frequency

of the flood depends on factors such as the type of growing medium used, size of containers

and plants water requirements.


NFT (Nutrient Film Technique) hydroponic systems - This system uses a continuous nutrient

solution flow over the roots. This results in a thin film of nutrient solution around the roots,

allowing them both aeration and access to nutrients.

2.4.2 Open Hydroponic Systems

In open hydroponic systems a fresh nutrient solution is introduced for each irrigation cycle. The

nutrient solution is usually delivered to the plants using a drip system. In open hydroponic

systems an adequate run-off must be maintained in order to keep nutrient balance in the root

zone (Smart! Grow Intelligently, 2014).

2.5 Open versus closed hydroponics systems

Both open and closed system may be set-up for drip-irrigated substrate culture. In closed

systems, the drainage water is captured and reused following the adjustment of pH and nutrient

concentration (namely, the electrical conductivity, EC) and, eventually, disinfection to minimize

the risks of root-borne diseases, (Pardossi,2011).

In substrate culture, an excess of fresh (newly prepared) nutrient solution is generally supplied to

overcome the difficulties associated with unequal transpiration of individual plants and to

prevent the salt accumulation and the imbalance in the nutrient solution. Typically, a drain

fraction of at least 20-25% is used in substrate cultivation to prevent root zone salinization.

Therefore, in open soilless systems there is a massive waste of water and nutrients, which is

responsible for an increase in running costs and in contamination of ground and surface water.

For instance, Pardossi reported that the annual drainage loss of water and nitrogen from open

substrate culture of rose was, respectively, 2123 m3/ha and 1477 kg ha-1. The application of

closed soilless systems is essential for sustainable protected horticulture. Unfortunately, the

application of these systems is scarce on a commercial scale and, with the exception of the

Netherlands where they are compulsory, open soilless cultures are commonly used for vegetable

and ornamental crops, as their management is much simpler. Along with the risks consequent to

the possible diffusion of root pathogens, the salinity of irrigation water represents the main


difficulty for the management of closed growing systems. When the use of saline water is

imposed, there is a more or less rapid accumulation of ballast ions, like sodium and chloride.

Under these conditions, the nutrient solution is normally recirculated till electrical conductivity

(EC) and/or the concentration of some potential toxic ion reach a maximum acceptable value,

afterwards it is replaced, at least partially (‘semi-closed’ systems), (Pardossi,2011)

Pardossi, 2011 tested the application of closed substrate culture to greenhouse tomato cultivation

in a commercial greenhouse in Tuscany, Italy. In the closed system, the plants were fed with a

slightly different nutrient solution (in general, it had lower nutrient concentration) with respect to

that used in the open culture, in order to maintain a constant nutrient concentration in the root

zone. In closed system, recirculating nutrient solution was periodically analyzed with

reflectometer in order to adjust the composition of the refill nutrient solution. Fruit yield and

quality were not significantly different in the two cultures. The application of closed system

reduced the use of water (-21%) and nutrients (-17 to -35%) and made it possible to carry out the

cultivation without any nutrient leaching, which instead was massive in open culture.

2.6 Fertigation

According to Smart! Grow Intelligently, 2014, fertigation is the process in which fertilizers are

applied with the irrigation water: Fertilization + Irrigation. The fertilizer solutions are prepared

in advance in stock tanks and the solution is then injected into the irrigation water. Fertigation

has various advantages over other fertilization methods, and when properly used, it saves time

and money. Some of the advantages are according to Smart! Grow intelligently, 2014:

Fertilizer application is more accurate and uniform

Fertilizers are applied to specific areas, where they are needed

Nutrient are immediately available to plants

Uptake of nutrients by roots is improved

It saves labor

It helps to save water, because plants develop a healthier root system

Nutrient losses are minimized


2.6.1 Fertigation Approaches

The most common fertigation approaches are the quantitative approach and the proportional

approach as described by Smart! Grow Intelligently, 2014.

The quantitative approach is commonly used in open fields. The grower first decides how much

fertilizer has to be applied per area (e.g. kg/ha, lbs/acre). This quantity of fertilizer is then

delivered through the irrigation water (Smart! Grow Intelligently, 2014).

The proportional approach is mostly used in soil-less media and sandy soils. Here, a defined

quantity of fertilizer stock solution is injected into each unit of water flowing through the

irrigation system (e.g. l/m3, lbs/gal) (Smart! Grow Intelligently, 2014).

Nutrient levels are determined by their concentration in the irrigation water. Most growers who

use proportional approach, use units of ppm (parts per million) or mmol/l.

2.6.2 Fertigation Systems

The process of fertigation is done with the aid of special fertilizer apparatus (injectors) installed

at the head control unit of the system, before the filter. The element most commonly applied is

nitrogen. However, applications of phosphorous and potassium are common for vegetables.

Fertigation is a necessity in drip irrigation, though not in the other micro-irrigation installations,

although it is highly recommended and easily performed.

Several techniques have been developed for applying fertilizers through the irrigation systems

and many types of injectors are available on the market. There are two main techniques: the

ordinary closed tank and the injector pump. Both systems are operated by the system’s water

pressure. The injector pumps are mainly either Venturi type or piston pumps. The closed tanks

are always installed on a bypass line, while the piston pumps can be installed either in-line or on

a bypass line.

Fertilizer (closed) tank is a cylindrical, epoxy coated, pressurized metal tank, resistant to the

system’s pressure, and connected as a bypass to the supply pipe of the head control. It operates


by differential pressure created by a partially closed valve, placed on the pipeline between the

inlet and the outlet of the tank. Part of the flow is diverted to the tank entering at the bottom. It

mixes with the fertilizer solution and the dilution is ejected into the system. The dilution ratio

and the rate of injection are not constant. The concentration of fertilizer is high at the beginning

and very low at the end of the operation (FAO, 2015).

Venturi type is based on the principle of the Venturi tube. A pressure difference is needed

between the inlet and the outlet of the injector. Therefore, it is installed on a bypass arrangement

placed on an open container with the fertilizer solution. The rate of injection is very sensitive to

pressure variations, and small pressure regulators are sometimes needed for a constant ejection.

Friction losses are approximately 1.0 bar. The injectors are made of plastic in sizes from to 2

inches and with injection rates of 40–2 000 liters/h. They are relatively cheap compared to other

injectors (FAO, 2015).

Piston pump is a type of injector that is powered by the water pressure of the system and can be

installed directly on the supply line and not on a bypass line. The system’s flow activates the

pistons and the injector is operated, ejecting the fertilizer solution from a container, while

maintaining a constant rate of injection. The rate varies from 9 to 2 500 liters/h depending on the

pressure of the system and it can be adjusted by small regulators. Made of durable plastic

material, these injectors are available in various models and sizes. They are more expensive than

the Venturi-type injectors (FAO, 2015).


Figure 6: Fertigation Injectors. Source: Pressurized irrigation techniques, FAO 2015

3


Figure 7: Fertigation Systems. Source: Google images on

fertigation systems

A Fertijet is a by-pass fertigation system. It adapts to any kind of flow line from 20m3/h up

wards. It is compact and very simple to install. It is good for EC/pH control. A Fertijet and a

Galcon Irrigation controller are shown in Appendices C1 and C2 respectively.

2.7 Treatment of Irrigation Water

As environmental issues are on the rise in hydroponics it necessitates farmers to recirculate the

nutrient solution. Disinfection systems are thus crucial since with the use of recirculation systems

the risk of root pathogens infecting the whole system is high. There are several methods to

disinfect the nutrient solution in order to kill water borne pathogens and thus avoid losses in

yield and quality. Surface water sources such as rivers, ponds and reservoirs for storing runoff

water are mostly contaminated with bacteria and pathogens yet they are used for irrigation. This

requires that the water is disinfested before use in irrigation.

2.7.1 Pre-treatment or Filtration

Pre-treatment or filtration of irrigation water is of necessity since large particles in the water are

likely to clog the irrigation system and also the effectiveness of pathogens treatment methods is

reduced in water that contains particulate organic matter. Ultra violet treatment requires clear


water for radiation wavelength to be transmitted through the pathogen walls while chlorine will

react with organic material and thus its treatment will be less effective. Filtration involves the

removal of organic and inorganic particulate matter i.e. debris, sediment, soil particles, algae, etc

from the dirty water prior to treatment to destroy pathogens.

Filters are categorized depending on the method used to filter the water. Screen filters have the

ability to remove hard particulate from water like sand but are limited in removing organic

materials such as algae, mold e.t.c. The organic material tends to stick in the screen thus difficult

to remove or they can actually slide through the mesh in the screen by temporarily taking a

different shape. Cleaning of the screen filters is done by flushing a stream of water through the

filters or by hand cleaning.

Media filters operate by forcing the water through a container with media which in most cases is

uniformly sized crushed sand. The water passes through the media and the debris is trapped in

the small spaces in the media. The media is usually sharp edged thus these filters are best in

removing organic matter since the edge traps the organic material that would otherwise slide

through the small spaces in the media. Cleaning of media filters is done by back flushing where

the water going backwards through the filter separates the media and thus the debris is freed and

is washed out through a flush valve. A small amount of media is washed out thus it is necessary

to refill the media occasionally. For cases where the water contains sand it is not appropriate

since the sand will not be flushed out thus it will fill up the filter. Media filters must be selected

to fit the system flow rate for proper operation. When the media used is gravel the filters are

known as gravel filters. Gravel filters are designed to be modular to cater for most flow

measurements and are used for primary filtration of water from reservoirs, dams, open canals,

rivers, sewage water and other types of contaminated water.


Figure 8: Media filters e.g. gravel filters. Source: Google images.

Disk filters have characteristics of both screen and media filters. They have the ability to remove

both sand and organic matter. This filter contains an array of round disks in which the face of

each disk has various sized bumps. The bumps are sharp pointed and when stacked together have

tiny spaces between them. Water flowing through the disks will leave behind particulates. The

organics are trapped by the sharp pointed bumps. In automatic cleaning the disks are separated

which frees the debris thus they are flushed. In manual cleaning the disks are removed and they

are hosed off.

Centrifugal filters also known as sand separators are particularly for removing particulates such

as sand from water. They are best fit for water that contains a lot of sand as compared to other

filters. This is because the mechanism of swirling the dirty water when it enters the cylinder a

centrifugal force causes the sand particles to move to the edge of the cylinder where they slowly

slide to a tank at the bottom. These filters are applied when pumping water from well or

reservoirs since in them there exist a lot of sand particles. The centrifugal filters are cheap,

simple and very efficient in removing sand particles from dirty water. The selection of the

centrifugal filter must be matched to the flow or GPM for it to function correctly.

2.7.2 Treatment of Irrigation water to remove pathogens

Disinfection methods that can be used to improve microbial irrigation water quality include

chlorination, ultraviolet radiation and ozonation. Chlorination hinders bacteria from increasing

by damaging their membranes. In this method, chlorine is injected into irrigation systems as

liquid by a metering pump as required and is controlled to meet variations in water quality.

Chlorination is cheap since the low required doses (2-3 mg/L) and also the capital cost as


compared to UV system is low. The effectiveness of this method is dependent on water quality

i.e. organic content, contact time, pH and temperature. This method requires proper management

of the chemicals since discharge of the chemicals to the environment is injurious.

Figure 9: A chlorine injection system. Source: Van der Gulik. T, 2003.

Ultra violet radiation systems allow exposure of irrigation water to UV radiation which

inactivates bacteria rendering them unable to reproduce. They are chemical free systems thus

will have no effect on plants unlike chemical treatments. The systems have no residual effect that

is they do not permanently alter the water outside pathogen destruction. These systems comprise

of cylindrical mercury arc lamps that are placed inside a cylindrical stainless steel chamber. The

lamps have different lengths and energy outputs and provide higher intensities than sunlight.

Water enters one end of the cylinder flows around the lamps and exits through the other end. The

amount of bacteria that is inactivated is depended on the applied UV dose which streams down

from the radiation intensity and the exposure time. These systems are sensitive to high turbidity

and organic matter content of which both reduce UV transmittance thus UV disinfection. In

order to remove excess turbidity and organic matter pre-treatment by filtration is required.

Filtration ensures adequate penetration of ultraviolet light through the entire flow profile.


The design criteria for an Ultraviolet treatment system requires that filters are provided for pre-

treatment of which after filtering the water the radiation transmission level is estimated to be

50%. Turbulent flow is required in the ultra violet units in order to enable enough contact time

of the radiation with the microorganisms. Standard UV dosages have being set for cropping

washing facilities as 40,000 and irrigation system treatment as 16,000. Chlorination is used with

the washing facilities but residual chlorine has to be checked before discharge. Irrigation treated

is required to start 30 days before harvest. The maximum required pressure in the treatment unit

is 100 psi thus a booster pump is usually required after the UV treatment unit in large scale

irrigation systems. The sizing of the ultraviolet treatment unit depends on the flow rate, light

intensity and the required water quality.

Figure 10: A pilot scale UV disinfection system. Source: Van der Gulik. T, 2003.


Figure 11: Ultraviolet treatment unit. Source: Van der Gulik. T, 2003.

Ozonation involves machines that produce ozone a strong oxidizing agent that kills bacteria in a

short time. It involves carbon filtration for complete water treatment as it does not protect the

water at initial dosing. It has the capability of achieving high disinfection levels that UV and

chlorination but the technology requires testing for irrigation applications.

2.8 Recirculating Hydroponics system

The recirculating hydroponics system includes water source, reservoir tanks, pump house, filters,

U.V. cylinder, fertilizer mixing tanks, fertiget, irrigation controller, Irrigation lines, drainage

lines, drainage collection tank, disinfection unit, treated water tank and valves (electronic flow

meters). The system mostly uses drip irrigation on the hydroponic troughs (Rono, 2015). The

dimensions of the hydroponic troughs are dependent on the plant spacing, plant population and

the length of the farm. The standard number of drip lines in drip-irrigated hydroponic troughs is

2 drip lines per tough (Rono, 2015). The size of the hydroponic troughs of the system is

depended also on the 2 drip lines per trough which determines the plant population. Once the

dimensions of the trough are specified they are selected from manufacturer’s catalogue. Large

greenhouse areas can be divided into ‘fertigation zones’ which can be managed individually with

their own nutrient strength and irrigation program.


40% of irrigation water supplied to the crops is drained (Rono, 2015). The drain water is filtered

to remove organic matter, disinfected using U.V, checked for fertigation requirements and then

recycled. The amount of EC and Na is monitored in the drain water and when maximum the

water is drained away but if less the drained water is recycled which is described as a semi-

closed system. The EC and Na can be regulated to obtain various options of substrate

management layouts. Below are layouts of the recirculating hydroponic system.

Figure 12: Typical layout of a (hydroponics) substrate soilless growing system. Source:

Pardossi, (2011). Fertigation and Substrate Management in Closed Soilless Culture. Pg.45



Management in Closed Soilless Culture. Pg.47


Management in Closed Soilless Culture. Pg.50


Figure 15: Hydroponics troughs layout with 2 drip lines per trough. Source: Irrico International

Ltd Images

2.9 Design of Irrigation and Drainage lines

The irrigation lines in an irrigation system include the mainline, the sub-mains, valves and

laterals. The mainline conveys water from the pumps to the valves in each of the fertigation

zones where the sub-mains then convey water to the laterals. The size of mainline is determined

by required flow rate through the pipe determined from emitter discharge, emitter spacing and

drip line/lateral length. Drip lines are selected from plant spacing. The size of the main line is

also determined by overall length of line, static height, flow velocity and factor of safety.

The sub-mains area sized depending on the no. of the drip-lines per section of the fertigation

zones, the slope, length of the line, flow velocity and the static head. The sub-mains are designed

to ensure that the last laterals get water. The laterals/drip lines are selected from the

manufacturer’s list depending the plant spacing, pressure requirements, length of the drip line


and cost. The valves are designed depending on the discharge required in each fertigation zone.

The sizing of the drainage lines is dependent on the 40% drained irrigation water and the slope.

In designing irrigation and drainage lines, the following factors should be kept in mind (Rono,

2015); maximum permissible velocity should not exceed 2.5m/s, maximum friction losses should

be limited to less than 3% along the length of the pipe, mainlines should follow the shortest

possible route and larger pipe diameters are more expensive thus it is important to manage the

discharge in each irrigation cycle in order to obtain lesser discharges thus less pipe diameters and

therefore less cost. Friction loss through pipelines can be calculated using the modified Hazen-

Williams formula.

2.10 Irrigation Hydrants

Hydrants define a combination of both a valve and a meter in one compact body. The meter is

included to calculate and indicate volumes of water. The hydrants are manually or automatically

operated to control the flow required for the irrigation area. They are fitted with electric

solenoids to make them automatic. In that case other accessories can also be fitted to control

other hydraulic parameters such as a pressure reducing accessory.

Figure 16: Automatically operated hydrant. Source: Google images.

http://www.irrigationhydrant.com/Hydrant-IDR-7r.jpg


Figure 17: Manually operated hydrant. Source: Google images.

Valves are used to control the flow required per given time. They are selected based on the flow

and manufacturer’s specifications.

Figure 18: Valve Source: Google images

2.11 Pump Selection

For ordinary pumping, the roto-dynamic pump is most commonly used as it provides satisfactory

and economic service. At very low flow rates the rotary pump is less costly if the water to be

pumped is free of grift.


The discharge of a centrifugal pump varies with the head and a variable-speed drive is necessary

if constant discharge is to be maintained under varying head. A reciprocating pump overcomes

this difficulty since its discharge depends only on the speed of the pump. Reciprocating pumps

are high in first cost and difficulty to maintain in efficient operating conditions. They are best

adapted for use under very high heads. Centrifugal pumps are well suited to pumping wastewater

and water containing solids, but displacement pumps are not generally used for such duty. The

hydraulic ram, although wasteful of water, finds occasional use where water is plentiful and

outside power unavailable.

The operating efficiency of any pump depends upon a combination of capacity, discharge

pressure and pump speed. A properly selected pump will have its highest operating efficiency

when delivering the system’s design output in gallons per minute (GPM) and head (pressure).

Changes in the system (e.g., pumping lift, discharge rate or pressure) that take place after a pump

has been selected and installed will usually reduce pumping efficiency.

Manufacturer’s pump performance curves are published for each model and size pump. These

curves indicate pump performance and efficiency at any combination of head and capacity

conditions and pump speed. They also show the pump’s required horsepower to meet the

system’s design conditions.

2.12 Softwares used in the product design of this project

2.12.1 CROPWAT 8.0

According to FAO, CROPWAT 8.0 is a computer program used for the calculation of crop water

requirements and irrigation requirements based on soil, climate and crop data. The program

allows the development of irrigation schedules for different management conditions and the

calculation of scheme water supply for varying crop patterns. It can also be used to evaluate

farmers’ irrigation practices and to estimate crop performance under both rain fed and irrigated

conditions.

All calculation procedures used in CROPWAT 8.0 are based on the two FAO publications of the

Irrigation and Drainage Series, namely, No. 56 "Crop Evapotranspiration - Guidelines for

computing crop water requirements” and No. 33 titled "Yield response to water".


FAO states that as a starting point, and only to be used when local data are not available,

CROPWAT 8.0 includes standard crop and soil data. When local data are available, these data

files can be easily modified or new ones can be created. Likewise, if local climatic data are not

available, these can be obtained for over 5,000 stations worldwide from CLIMWAT, the

associated climatic database. The development of irrigation schedules in CROPWAT 8.0 is

based on a daily soil-water balance using various user-defined options for water supply and

irrigation management conditions. Scheme water supply is calculated according to the cropping

pattern defined by the user, which can include up to 20 crops.

2.12.2 CLIMWAT 2.0

FAO defines CLIMWAT as a climatic database to be used in combination with the computer

program CROPWAT and allows the calculation of crop water requirements, irrigation supply

and irrigation scheduling for various crops for a range of climatological stations worldwide. It is

a joint publication of the Water Development and Management Unit and the Climate Change and

Bio-energy Unit of FAO. It offers observed agro-climatic data of over 5000 stations worldwide.

According to FAO, CLIMWAT provides long-term monthly mean values of seven climatic

parameters, namely:

Mean daily maximum temperature in °C

Mean daily minimum temperature in °C

Mean relative humidity in %

Mean wind speed in km/day

Mean sunshine hours per day

Mean solar radiation in MJ/m2/day

Monthly rainfall in mm/month

Monthly effective rainfall in mm/month

Reference Evapotranspiration calculated with the Penman-Monteith method in mm/day.

2.12.3 HydroCalc

NETAFIMTM is an Irrigation Company that has developed the HydroCalc Irrigation Planning

software for the irrigation community. It describes HydroCalc as a simple and easy calculation


tool to perform some basic hydraulic computations. The use of HydroCalc would allow the

designer, dealer or end-user to evaluate the performance of micro irrigation in-field components,

such as:

Drip laterals and micro sprinklers

Sub mains and manifolds

Mainlines (PVC, PE, etc)

Valves

Energy Calculation


3.0 THEORETICAL FRAMEWORK

3.1 Evapo-transpiration (ETO)

According to FAO, ETO is the reference crop evapo-transpiration or reference evapo-

transpiration, denoted as ETo. The reference surface is a hypothetical grass reference crop with

an assumed crop height of 0.12 m, a fixed surface resistance of 70 s m-1 and an albedo of 0.23.

The reference surface closely resembles an extensive surface of green, well-watered grass of

uniform height, actively growing and completely shading the ground. The fixed surface

resistance of 70 s m-1 implies a moderately dry soil surface resulting from about a weekly

irrigation frequency.

ETo can be computed from meteorological data using the FAO Penman-Monteith method which

is recommended as the sole standard method for the definition and computation of the reference

evapo-transpiration. The FAO Penman-Monteith method requires radiation, air temperature, air

humidity and wind speed data.

ETO =0.408∆(Rn−G)+ γ( 900

T+273)U2(es−ea)

∆+γ(1+0.34U2) 3.1

where

ETo is reference evapo-transpiration, mm/day,

Rn is net radiation at the crop surface, MJ/m2/day,

G is soil heat flux density, MJ/m2/day,

T is mean daily air temperature at 2 m height, °C,

U2is wind speed at 2 m height, m/s,

es is saturation vapour pressure, kPa,

ea is actual vapour pressure, kPa,

es-ea is saturation vapour pressure deficit, kPa,

∆ is slope vapour pressure curve, kPa/°C,

γ is psychometric constant, kPa/°C.


3.2 Crop water requirement

According to FAO, the crop water requirement is the amount of water needed to compensate the

evapo-transpiration loss from the crop field is termed as crop water requirement. The value of

crop water requirement is identical to evapo-transpiration. Crop water requirement varies with

time and space, as the evapo-transpirative demand varies with local climate and crop condition.

Crop water requirement represents the evapo-transpiration (ET) under ideal crop growth

condition.

ETc = Kc × ETo 3.2

where

ETc is crop evapo-transpiration,

ET0 is reference evapo-transpiration,

Kc is the crop coefficient

The crop evapo-transpiration differs distinctly from the reference evapo-transpiration (ETo) as

the ground cover, canopy properties and aerodynamic resistance of the crop are different from

grass. The effects of characteristics that distinguish field crops from grass are integrated into the

crop coefficient (Kc).

Crop water requirement can be calculated from the climate and crop data. Crop water

requirement for a given crop, i, for the whole growing season:

𝐶𝑊𝑅𝑖 = 𝐸𝑇𝑐 = ∑ =𝑚𝑡=0 (𝐸𝑇𝑜𝑡 × 𝐾𝑐𝑡) 3.3

where

CWRi is the crop water requirement for the growing period, mm,

ETc is the crop evapo-transpiration for the growing period, mm,

t is the time interval in days,


m is the days to physiological maturity from sowing or transplanting (total effective crop

growth period), in numbers,

ET0t is the reference crop evapo-transpiration of the location concern for the day t, mm,

Kct is the crop coefficient for the time t day.

N.B; Physiological maturity is the status of maturity after which the weight of the grains does not

change/increase. Normally it reaches a week (7 days) ahead of traditional harvest time in cereals,

and 3–5 days in pulses and oil seeds. Crop water requirement for a particular growth stage (or

period) of the crop can be calculated using the Kc for that growth stage (or period).

Crop water requirement (CWR) and irrigation water requirement (IWR) can be best described

with the following mathematical functions:

CWR = f (weather, crop)

IWR = f (weather, crop, soil, rainfall, irrigation method, depth to water-table or saturated

layer)

3.3 Net Irrigation Requirement (NIR)

According to FAO, it is given by:

NIR = ∑(Kc × ETo ) + P − (Re + GWC) 3.4

where

NIR is the net irrigation requirement for normal growth period (from

sowing/transplanting to last watering, i.e., excluding land preparation and pre-sowing

irrigation), mm,

GWc is the groundwater contribution during the period, mm,

P is the deep percolation loss during the period concerned, mm,

For a particular irrigation event, irrigation water requirement based on soil moisture deficit is

NIWRm = ∑(FCi–SMi ) ×di

100 (1 −LF)

ni=1 3.5


where

FCi is the field capacity (water holding capacity) of soil of i layer, in percent volume,

SMi is the present soil moisture content, in percent volume,

d is the depth of i layer, in cm,

LF is the leaching fraction. If leaching is not required LF = 0

3.4 Gross Irrigation Requirement (GIWR)

According to FAO, the Gross water requirement is the water required for irrigation considering

field application loss and conveyance loss. That is

𝐺𝑟𝑜𝑠𝑠𝑖𝑟𝑟𝑖𝑔𝑎𝑡𝑖𝑜𝑛𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡, 𝐺𝐼𝑊𝑅 = 𝑁𝐼𝑊𝑅

𝐸𝑎×𝐸𝑐 3.6

Where

Ec is the field conveyance efficiency,

Ea is the field application efficiency.

𝑇𝑜𝑡𝑎𝑙 𝐼𝑟𝑟𝑖𝑔𝑎𝑡𝑖𝑜𝑛 𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡, 𝑇𝐼𝑅 = 𝐺𝐼𝑅 × 𝐴𝑟𝑒𝑎 3.7

3.5 Irrigation Scheduling

The problem of irrigation consists of when to irrigate, and how much to irrigate. Efficient water

use depends on timely application of water at right amount at right time with right way or

method. Irrigation scheduling means when to irrigate and how much water to apply in crop field.

In other words, irrigation scheduling is the decision of when and how much water to be applied

in a crop field. The objectives of irrigation scheduling are to maximize yield, irrigation

effectiveness/efficiency, and crop quality by applying the exact amount of water needed by the

crop (or to replenish the soil moisture to the desired level). Irrigation scheduling can be

determined from the flow chart below;


Figure 19: Conceptual framework of irrigation scheduling in soilless culture. Source: Pardossi,

(2011). Fertigation and Substrate Management in Closed Soilless Culture. Pg.28


3.6 Calculation of head losses n the pipes by Hazen Williams equations

It was developed for water flow in larger pipes (D>5 cm, approximately 2 in.) within a moderate

range of water velocity (V<3 m/s, approximately 10 ft/s). Hazen-Williams equation, originally

developed for the British measurement system, has been written in the form

𝑉 = 1.318 𝐶𝐻𝑊𝑅ℎ0.63𝑆0.54 3.8

where

S= slope of the energy grade line, or the head loss per unit length of the pipe (S =hf

𝐿)

Rh = the hydraulic radius, defined as the water cross sectional area (A) divided by wetted

perimeter (P).

For a circular pipe, with A = 𝜋𝐷2

4 and P = π D, the hydraulic radius is

𝑅ℎ = 𝐴

𝑃 =

(𝜋 𝐷2 4⁄ )

(𝜋 𝐷) =

𝐷

4 3.9

The Hazen-Williams equation in SI units is written in the form of

𝑉 = 0.849 𝐶𝐻𝑊𝑅ℎ0.63𝑆0.54 3.10

Velocity in m/s and Rh is in meters.

Given;

𝑉 = 𝐵 × 𝐶 × 𝑅ℎ0.63 × 𝑆0.54

Where Rh = 𝐷

4

Slope,S = hf

𝐿

B = 1.318 in British system

B = 0.85 in S.I. units

C = Hazen William coefficient

𝐴 × 𝑉 = 𝑄 = 𝐴 × 𝐵 × 𝐶 × (𝐷

4)

0.63

× (ℎ𝑓

𝐿)

0.54

ℎ𝑓 = 𝐿

𝐶1.85× 𝐷4.87 × 7.88

𝐵1.85 × 𝑄1.85


𝑅𝐻𝑎𝑧𝑒𝑛 𝑊𝑖𝑙𝑙𝑖𝑎𝑚𝑠 = 𝐿

𝐶1.85× 𝐷4.87 × 7.88

𝐵1.85

Thus head loss,

ℎ𝑓 = 𝑅𝐻𝑎𝑧𝑒𝑛 𝑊𝑖𝑙𝑙𝑖𝑎𝑚𝑠 × 𝑄1.85 3.11

3.7 Crop electrical conductivity and Ph requirements for fertigation unit

According to Camberato, et.al, 2015, nutritional problems are one of the primary causes of poor

crop quality and plant losses in greenhouses and nurseries. Monitoring the pH and electrical

conductivity (EC) of growing substrates gives you the ability to correct tissues before they

become problems that damage crops.

The pH of the growing substrate or media affects the availability of nutrients, especially

micronutrients. EC is a measure of the dissolved salt concentration in a growing substrate. EC

values provide a measure of the amount of fertilizer available for plant growth or indicate an

accumulation of salts in the media. It is important to routinely monitor substrate pH and EC

levels before nutrition problems arise. Some of the methods to determine the EC and Ph

according to Camberato, et.al, 2015 are as follows:

PourThru Test

The PourThru extraction method has several advantages: it samples the solution from the entire

root zone, is nondestructive, and can be used with media that contain slow- or controlled-release

fertilizers. It also can be used to test the bark, coconut coir, orsphagnum moss media used to

grow orchids. The major disadvantage of this method is that results are variable. Sampling from

dry pots may result in greater EC because of higher salt concentration. Adding too much water

could dilute the sample and result in a lower EC. Irrigating the crop as usual (see step 1 below)

and monitoring the volume of water added (see step 4) will help minimize these sources of

variation. To sample using the PourThru test method:

1. Fertigate or irrigate the crop as usual for your production program and establish a specific

testing day if fertigation is conducted once a week.

2. Allow the substrate to drain for 30 to 60 minutes.


3. Place a saucer under the pot.

4. Apply enough distilled water (approximately 100milliliters (3.4 ounces) per 6.5-inch pot)

to collect as close to 50 milliliters (1.7 ounces) of leachate as possible. More than 70

milliliters (2.4 ounces)of leachate can dilute the salt content, while less than 50 milliliters

of leachate may not provide enough solution to cover the probe

5. Measure the pH and the EC of the leachate.

Saturated Media Extract Test

The saturated media extract test has the advantage of being an accurate test. However, it requires

removing substrate from the pot, which can be a disadvantage because this disturbs the roots, and

care must be taken to avoid breaking any fertilizer prills if the substrate contains slow-release

fertilizer. To sample using the saturated media extract method:

1. Obtain a 200- to 300-milliliter (7- to 10-ounce) sample of substrate from the root zone

(avoid sampling from the top inch and bottom inch of the pot because of the potential for

a higher salt content).

2. Place the sample in a 500-milliliter (17-ounce) beaker or container.

3. Add only enough distilled water to wet the sample to saturation — there should be no

free water on the sample surface

4. Let the sample stand for 30 minutes to equilibrate.

5. Pour the mixture into a clean funnel lined with a filter (such as a coffee filter, or a tea or

wire mesh strainer) to avoid getting substrate in the solution. Attaching a vacuum line or

squeezing the solution through the filter with a spatula or gloved hand, can help obtain

the sample more quickly.

6. Measure the pH and the EC of the leachate.

3.8 Pump Design

The pump is an electro-mechanical device that lifts a fluid from one level to another and delivers

it with a desired pressure. Pumps are selected based on the total head, h (pressure) and discharge,

m³/ hour (Rono, 2015).

Pump discharge is the required irrigation water or drain water per irrigation schedule. Total head


of the pump is a summation of the following parameters:

Suction – vertical distance between water level and pump center line

Delivery – vertical distance between pump center line and ground level

Frictional head loss in irrigation and drainage pipe lines– as a factor of coefficient of

friction. Different pipe materials have different coefficients of friction; roughness or

smoothness of the inner wall.

Operating pressure – operating pressure of the emitter of the drip line is determined and

specified by the manufacturer.

Frictional head loss in fittings – tees, bends, valves, reducers , gravel filters and other

fittings contribute to about 10 m friction loss in a system.

Ground elevation – this is the vertical distance between the lowest point on the ground

and the highest point on the field under consideration.

Total Pump head = Suction + delivery + frictional head loss in pipe + Operating pressure +

frictional head loss in fittings + Ground elevation

Power input to run the pump is usually indicated in the pump curve. If not indicated, power in

Horsepower can be calculated.

The power required, N, for driving a pumping unit can be calculated with the following formula:

N = 𝑄𝑥𝐻

102𝑥𝐸 kW 3.12

where

Q = Flow in 1/s

H = Pumping head in meter

e = pumping efficiency (will have a value between 0 and 1)

The energy demand can be calculated with the following formula:

E = 𝑄𝑥𝐻

𝑒kWh per year 3.13

where


Q = pumped quantity of water per day, m3/day

H and e = as above

In practice the efficiency of small-capacity pumps in particular is low. It can be assumed that the

efficiency is in the range of 30% for a 0.4 kW pump and 60% for a 4 kW or bigger pump.

Figure 20: Total Pump head for an Irrigation system. Source Google images

3.9 Drip Irrigated Hydroponics Design

For hydroponics 40% of the water is drained because of the porous characteristics of the medium

i.e. coco peat, 20% of the irrigation water is lost due to evaporation losses and other losses, thus

only 20% of the applied irrigation water is taken up by the plants, thus effective precipitation is

60% of the irrigation water. Therefore to obtain the effective crop water requirement;

Effective crop water requirement = 𝐶𝑟𝑜𝑝 𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡

0.6 3.14

The flow required in the drip irrigation area;

Flow required (m3/hr) = 𝐷𝑟𝑖𝑝𝑙𝑖𝑛𝑒𝑙𝑒𝑛𝑔𝑡ℎ∗𝑒𝑚𝑖𝑡𝑡𝑒𝑟𝑑𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒

𝑒𝑚𝑖𝑡𝑡𝑒𝑟𝑠𝑝𝑎𝑐𝑖𝑛𝑔∗1000 3.15


The irrigation schedule is determined from;

Depth of Irrigation water application required = 𝐹𝑙𝑜𝑤𝑑𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑/𝑠𝑒𝑐𝑡𝑖𝑜𝑛

𝐴𝑟𝑒𝑎𝑜𝑓 𝑡ℎ𝑒 𝑡𝑟𝑜𝑢𝑔ℎ𝑠

Irrigation schedule = 𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝑐𝑟𝑜𝑝𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡

𝐷𝑒𝑝𝑡ℎ𝑜𝑓𝑖𝑟𝑟𝑖𝑔𝑎𝑡𝑖𝑜𝑛𝑤𝑎𝑡𝑒𝑟𝑎𝑝𝑝𝑙𝑖𝑐𝑎𝑡𝑖𝑜𝑛𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑/𝑠𝑒𝑐𝑡𝑖𝑜𝑛 3.16

Sizing the valves;

Discharge in valves = Velocity * Area

Q = V * A 3.17

Area = 𝜋𝐷2

4 ; D2 =

𝐴𝑟𝑒𝑎∗4

𝜋

The slope is given by ;

Slope = ∆𝑦

∆𝑥 3.18


4.0 METHODOLOGY

4.1 Feasibility Study

In order to determine the technical feasibility of the project the yield of tomatoes in the field

grown crops and hydroponically grown crops including tomatoes were compared from previous

yields worldwide. The yield in open field was found to be approximately 69,231 kg/ha/yr and in

hydroponics the yield was found to be approximately 585,000 kg/ha/yr. I determined that with

the yield of tomatoes in hydroponics being 585,000 kg/ha/yr and with my case study farm being

3ha the cost of the installation would be recovered in the sale of the crop.

I also gathered from industrial consultation that 40% of irrigation water is drained in run-to-

waste hydroponics and therefore with recirculation, water and fertilizer are conserved. Also the

hydroponic troughs are over-irrigated by 60% allow for losses. Thus from equation 3.14


0.6 3.14

4.2 Data Acquisition

Some of the important data that was required for the design included Geological data, climatic

data, crop data and farm coordinates. Geological data of the area was obtained from record of

Kenya soil survey who had compiled data from the Nanyuki Railway meteorological station in

order to determine the soil structure thus conclude on the superiority of the hydroponics media.

Coordinates of the farm were collected using a GPS receiver in order to use them on Google

earth to generate the ground dimensions of the farm. The coordinates were used on Google earth

as shown in the site analysis. Climatic data of the area and crop data were obtained from

CropWat and ClimWat respectively. For CropWat the highest ETc obtained was taken as the

crop water requirement and since it is hydroponics 60% of the crop water requirement was

allowed for drainage and evaporation losses. Thus the crop was over-irrigated by 60%.


4.3 Assessment of Existing Greenhouse

Observations of the greenhouse farm were carried out to determine the slope of existing

structure, position of existing rain water harvesting reservoir, space for nurseries and main

growing areas. The physical structures were documented by taking photographs as shown in

Appendix C. A desk study of the area was carried out by analyzing the documentation kept by

the farm concerning the structure of the greenhouse.

4.4 Sizing of System Components

4.4.1 Selection of drip lines and hydroponic troughs

The drip lines were selected depending on the plant spacing, the length of the drip line and

operating pressure and also the crop water requirement. The discharge of the emitters must meet

the daily crop water requirement per irrigation schedule. The hydroponic troughs sizes were also

selected from the plant spacing and the length of the farm. They are then selected from

manufacturer’s specifications.

4.4.2 Determination of hydroponic Layout

The no. of bays of the greenhouse was obtained from desk study. The no. of bays was used to

divide the green house into fertigation zones. The fertigation zones were obtained by dividing the

bays into manageable sections for various irrigation and fertigation requirement. The tomato

bush spacing was allowed between the hydroponic troughs from agronomic specifications. The

section length was also divided into manageable blocks leaving paths for management practices.

The greenhouse structure also takes the design from manufacturer’s specifications.

4.4.3 Sizing the irrigation lines

The flow required per section was determined from the total drip line length per section, emitter

spacing and emitter discharge from equation 3.15.

Flow required (m3/hr) = 𝐷𝑟𝑖𝑝𝑙𝑖𝑛𝑒𝑙𝑒𝑛𝑔𝑡ℎ∗𝑒𝑚𝑖𝑡𝑡𝑒𝑟𝑑𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒



The flow required is used to size the main line and valves for each fertigation zone. This

discharge is also used in the selection of the irrigation pump selection of the gravel filters, and

U.V cylinders.

The irrigation schedule is determined from area by obtaining the depth of irrigation water

application. Using the effective crop water requirement and the depth of irrigation water

application the irrigation schedule is obtained from equation 3.16 as;


𝐴𝑟𝑒𝑎𝑜𝑓 𝑡ℎ𝑒 𝑡𝑟𝑜𝑢𝑔ℎ𝑠

Irrigation schedule = 𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝑐𝑟𝑜𝑝𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡


The main lines and the sub-mains were sized using hydro calc and the following parameters flow

required, length of the line, cumulative end pressure required from manufacturer’s specifications

for the drip line to the specific line, maximum flow velocity of 2.5m/s, cumulative pressure loss

of >3% and the Hazen Williams equation 3.10

𝑉 = 0.849 𝐶𝐻𝑊𝑅ℎ0.63𝑆0.54 3.10

4.4.4 Sizing the valves or hydrants

The valve or the hydrant for each fertigation zone was sized depending on the floe required in

those zones per irrigation schedule and the velocity in the main line determined from hydro calc.

The sizes of the valves for each fertigation zone was determined using equation 3.17 and

equation for area

Discharge = Velocity * Area

Q = V * A 3.17

Area = 𝜋𝐷2

4 ; D2 =


𝜋


4.4.5 Selecting Irrigation Pump, filters and U.V cylinders

The irrigation pump was selected by determining the total head from equation



Once the total head was obtained and the required discharge at the main line is known the pump

was selected from the manufacturer’s specifications.

The power required if not specified in the manufacturer’s pump curve is obtained from equation

3.12

Power required, N = (𝑄∗𝐻

102∗𝑒) 𝑘𝑊 3.12

where Q – flow in l/s

H – Pumping head in meters (static head + losses)

e – Pumping efficiency (30% - 85% for a centrifugal pump)

Irrigation water U.V. cylinders and Filters were selected from the manufacturer’s catalogue

depending on the discharge required at the mainline. For the filters 60% of the flow was allowed

for back flushing. Thus flow required to select filters was;

Flow used to select filters = 𝐹𝑙𝑜𝑤 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 𝑝𝑒𝑟 𝑖𝑟𝑟𝑖𝑔𝑎𝑡𝑖𝑜𝑛 𝑠𝑒𝑠𝑠𝑖𝑜𝑛

0.6

4.4.6 Sizing and selection of the fertigation system

The fertilizer system selected was a fertiget which uses venturi to discharge the fertilizer mixed

in irrigation water. The fertiget does the EC and Ph adjustments and determines the fertilizer

injected using the Galcon Controller.

Fertigation required per irrigation schedule = Fertigation required per m3 * flow required per

irrigation schedule

Fertigation required per irrigation schedule is determined from the tomato fertilizer requirements

per growing season. The fertigation required is used to size the injection venturi. The size of the

fertiget depended on the fertigation required and the irrigation schedule i.e.


Size of the fertiget = Fertigation required per irrigation schedule * Irrigation time

The Fertiget was the selected from manufacturer’s catalogue to cater for the obtained volume.

The fertilizer mixing tanks are recommended to be 2 tanks for fertilizer and 1 tank of acid. The

sizing of the fertilizer mixing tanks was done for 3.3 days and using the fertigation required per

days. The acid tank was half the size of the fertilizer tanks since it is used for ph control.

4.4.7 Sizing the tank for Irrigation

The size of the tank for irrigation depended on the discharge required on the 3 hectare farm per

day and was sized for two days in order to reduce the cost of a large tank and also to fit

manufacturer’s specifications.

4.4.8 Sizing the Drainage system

Drainage layout was done in order to allow drainage by gravity. The land slopes at 1% in

opposite directions from the 4 m path in the middle of the farm and along the length it slope

downwards. This is slope was obtained during the green house construction. Drainage pipe was

placed at the end of the troughs of 40% of the water is drained.

In order to size the drainage pipes the drainage from 1 trough was determined using equation

Total discharge in one trough = No. of emitters/lateral * No. laterals/trough * Discharge per

emitter

In sizing the drainage pipe under the hydroponic troughs the distance of the troughs was

considered and the pressure in the drip lines. The drainage pipes on each block was sized

cumulatively first 10 bays then next 16 bays since the drainage is flowing by gravity and down

slope there would be more water. The same consideration was taken in the design of the main

drainage pipe. In general the drainage pipe was sized using hydro calc and using parameters such

as length of the pipe, discharge and pressure. The pipes were designed to have a maximum

velocity of 2.5m/s and cumulative pressure losses of >3% and also using Hazen Williams

equation 3.10

𝑉 = 0.849 𝐶𝐻𝑊𝑅ℎ0.63𝑆0.54 3.10


Since drainage will be on gravity a velocity of 1m/s was required in the drainage pipes.

4.4.9 Sizing the Drainage tank

The drainage tank was sized depending on the drain per day and the time that the drain water will

take to drain. The assumption taken was that the pump will pump water half the drainage time.

4.5.0 Sizing the recirculation System

Booster pumps were placed in the drainage tanks to pump the water automatically when the tank

is full.



Theoretically maximum suction for the operation of a pump is 6m, the elevation head is

determined from 1% slope , frictional losses and operation pressure are determined from hydro

calc.

Calculating elevation head using 1% slope from equation 3.18

Slope = ∆𝑦

∆𝑥 3.18

0.01 = ∆𝑦

∆𝑥 =

∆𝑦

𝑒𝑙𝑒𝑣𝑎𝑡𝑖𝑜𝑛 𝑎𝑡 𝑙𝑜𝑐𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑑𝑟𝑎𝑖𝑛𝑎𝑔𝑒 𝑡𝑎𝑛𝑘−𝑒𝑙𝑒𝑣𝑎𝑡𝑖𝑜𝑛 𝑎𝑡 𝑡𝑟𝑒𝑎𝑡𝑚𝑒𝑛𝑡 𝑡𝑎𝑛𝑘

Thus ∆𝑦 = 𝑒𝑙𝑒𝑣𝑎𝑡𝑖𝑜𝑛 𝑎𝑡 𝑙𝑜𝑐𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑑𝑟𝑎𝑖𝑛𝑎𝑔𝑒 𝑡𝑎𝑛𝑘 ∗ 0.01

Once the total head was obtained and the required discharge at the main line is known the pump

was selected from the manufacturer’s specifications.

The power required if not specified in the manufacturer’s pump curve is obtained from equation

3.12


102∗𝑒) 𝑘𝑊 3.12

where Q – flow in l/s




The drainage water media filter and U.V. cylinders were selected based on the drain water per

day and the irrigation time i.e. the discharge that is re-used.

4.5.1 Sizing the treated water tank

The treated water tank was sized depending on the drain water per days and to 15 days storage

then selected from manufacturer’s catalogue.

4.5.2 Sizing the valves for drainage water

The valves were sized depending on the drain water per day and the irrigation time. Also if the

stored water was sufficient they were sized to the irrigation requirement.

4.5.3 Cost benefit Analysis

The cost of installation was obtained from the bill of quantities and was compared to the sale of

yield of tomatoes from a hectare of hydroponic production. Also the amount of fertilizer recycled

or obtained from drain water was determined by taking 40% of applied fertilizer per m3


Figure 21: Generation of Concept Design

Data Acquisition

Design of the drip irrigation

and hydroponic troughs layout.

Sizing of pipes and pumps

Sizing & selection of a

fertigation unit .

Sizing of the drainage and recirculating

system.

Development of a Bill of

Quantities

Output = A complete design of a

recirculating hydroponics system


5.0 RESULTS AND DISCUSSION

The design of the recirculating hydroponics system was to;

increase the yield of tomatoes from HM Clause farm

provide a recirculating system to enable efficient use of water and fertilizer thus prevent

pollution of environment by drain water from the commercial farming at HM clause farm

Design considerations that facilitated the calculations;

Some of the considerations in the design of the hydroponics system are that in the green house

there is maximum ventilation, fans to simulate the wind, radiation of about 85% - 90%, fogging

to simulate humidity and controlled for optimum conditions thus this allows for the use of

CropWat which calculates crop water requirement (ETc) using the climatic conditions, soil type,

radiation, wind speed and rainfall of the area. Also in the use of CropWat effective rainfall is not

considered since irrigation water is supplied from the reservoir.

The greenhouse has 16 bays each of 12.8m along the length. There is a path of 4m at the middle

of the greenhouse that separates the greenhouse into two units. The irrigation layout is done by

dividing the greenhouse layout into fertigation zones of 3 bays each and 1 section of 1 bay on

either side of the 4m path giving a total of 12 sections. This is from agronomic specifications to

cater for seed varieties, pollination and fertilizer requirements.

5.1 Design Criteria




60% of the irrigation water. Therefore to obtain the effective crop water requirement;


0.6 3.14


In the design of pipes, it is recommended that the velocity in the pipe should not be more than

2.5m/s and the pressure losses are not supposed to go beyond 3% losses. In the design of the

drainage system, the drainage is by gravity since there 1% slope is on opposite sides of the

blocks. The minimum velocity allowed in gravity flow is 1m/s.

5.2 Identification of pertinent parameters

The pertinent parameters include dimensions of the farm and the crop water requirement. The

dimensions of the farm were found to be 209.8m x 140m. The green house has 16 bays of 12.8m

which is a manufacture’s design. A manufacturer’s path of 2.5m is left on either side of the

length for support thus 209.8m – (2.5m * 2) = 204.8m. Along the width a path of 4m is left for

management practices thus on either side a width of 68m is left. These creates two unit of which

again the unit is divided by a 1m path at the center and 1.5m paths on either side of the unit thus

the actual length of hydroponic troughs is 32m i.e.68𝑚−1𝑚−(2.5𝑚∗2)

2=

64𝑚

2= 32𝑚 on

either side of the unit. The layout of the 32m hydroponic troughs along the length begins at 0.6m

from the 2.5m path and the distance between troughs is 1.2m thus there are 8 troughs in 1 bay of

12.8m. The layout is then again divided into sections of 3bays. This gives 5 sections on each

block but 10sections in each unit. There is also an extra bay to make 16 bays. This bay makes the

1 bay section in each block but 2 sections of 1 bay in each unit. The sizing of the sections was

determined from agronomists’ requirement in order to grow seed varieties of tomatoes and also

apply different fertigation requirements and also for the cause of difference in pollination.

The crop water requirement was taken from CropWat from the highest ETc. The highest ETc was

found to 50mm/dec. In order to find the crop water requirement per day; 50𝑚𝑚/𝑑𝑒𝑐

10𝑑𝑎𝑦𝑠 = 5mm/day

since decade in CropWat indicates 10 days. The effective rainfall was obtained from ClimWat as

651.4mm which is sufficient for rain water harvesting in the farm.


Table 3: Coordinates of the points of the farm along the outside boundary of the farm as shown

on the Google earth image in site analysis

POINTS NORTHINGS EASTINGS

A 00 03’ 06.93’’ N 370 07’ 51.03’’ E

B 00 03’ 09.97’’ N 370 07’ 55.34’’E

C 00 03’ 08.92’’ N 370 07’ 59.20’’ E

D 00 03’ 08.70’’ N 370 07’ 59.44’’ E

E 00 03’ 05.57’’ N 370 08’ 02.87’’ E

F 00 03’ 00.59’’ N 370 07’ 58.18’’ E

G 00 03’ 03.58’’ N 370 07’ 54.92 E

H 00 03’ 03.83’’ N 370 07’ 54.64’’ E

The crop water requirement was extracted from CropWat as shown below;

Figure 22: Crop water requirement from CropWat, (2015)


Table 4: Rainfall data from ClimWat, (2015)

5.2.1 Selecting the drip lines from manufacturer’s catalogue

Tomato plant spacing is 20cm x 20cm. From agronomic specifications the distance between the

different troughs is 1.2m to allow for tomato bush when the crop matures. The layout of drip

lines in hydroponics is that there are 2 drip lines in each trough. The hydroponics troughs were

selected from manufacturer’s specifications as 20cmx40cmx20cm since the tomato plant spacing

is 20cm x 20cm thus the selection of the 40cm trough.

The Drip lines are also selected considering tomato plant spacing of 20cm x 20cm, head pressure

and pipe diameter in relation to cost thus from John deer Hydro PCND specifications drip lines

were selected with emitter spacing of 20cm as follows;

Hydro PCND (No-drain-flow-regulated integral drip line): Emitter spacing = 20cm, Emitter

discharge = 1.65L/hr, Lateral diameter =16mm, Thickness = 35mils and operating pressure


ranges between 0.8 – 3.5bar. The diameter of 16mm has relatively low head pressure and also

the cost is favourable as compared to the 20mm and 12mm diameter drip lines from hydro calc.

The drip lines selected are pressure compensating drip lines. This means that they deliver a

uniform flow rate even in areas with difficult topographical conditions. They also have a unique

pressure differential mechanism that regulates flow and provides self-cleaning action, even while

irrigating - for a clog-resistant design and high emission uniformity. It is the most appropriate for

green house application.

5.2.2. Flow required per fertigation zone/section

Calculating the total drip line length:

1 bay has 8 troughs, a trough is 32 m, and there are 2 drip lines on each trough

For a section that includes either side of the 4 m path and has 3 bays the drip line length is;

Drip line length for a section with 3 bays = 8 troughs per bay * 32m*2 either sides of the 4m

path *2 drip lines per troughs *3bays

Drip line length/section of 3 bays = 3072 m

Flow required for one section of 3 bays (m3/hr) = 𝐷𝑟𝑖𝑝𝑙𝑖𝑛𝑒𝑙𝑒𝑛𝑔𝑡ℎ∗𝑒𝑚𝑖𝑡𝑡𝑒𝑟𝑑𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒


Flow required/section of 3 bays = 3072𝑚∗1.65𝐿/ℎ𝑟

0.2𝑚∗1000 = 25.344m3/hr

Drip line length for a section with 1 bay = 8 troughs per bay * 32m*2 either sides of the 4m path

*2 drip lines per troughs *1bay

Drip line length/section of 1 bay = 1024 m

Flow required for one section of 1 bay (m3/hr) = 𝐷𝑟𝑖𝑝𝑙𝑖𝑛𝑒𝑙𝑒𝑛𝑔𝑡ℎ∗𝑒𝑚𝑖𝑡𝑡𝑒𝑟𝑑𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒


Flow required/section of 1 bay = 1024𝑚∗1.65𝐿/ℎ𝑟

0.2𝑚∗1000 = 8.448m3/hr


5.2.3 Time clock Irrigation scheduling

In this technique of irrigation scheduling, irrigation applications are programmed at fixed

intervals and rates. Usually, it is known as “hourly irrigation” because the irrigation application

interval is generally one hour, although it can be changed. The main disadvantage of this method

is that it is difficult to satisfy varying crop water requirements during the day, and during

different periods in the growing season. Irrigation requirements depend upon plants, varieties,

the development stage of plants, and substrates. Therefore, this irrigation system can make the

roots too wet or too dry and result in unbalancing the plants. Scheduling using solar integrators

can be used to start irrigation at a set level of radiation during varying day conditions but must be

supplemented by time clock scheduling during dark hours.

Irrigation schedule per section:

Length of troughs = 8 troughs/section * 32m * 2 either sides of the 4 m path * 3 bays/section

Total Length of troughs = 1536m

Area of the troughs = Total length * width

Area of the troughs = 1536m * 0.4m =614.4m2

Thus the schedule can be obtained from:


𝐴𝑟𝑒𝑎𝑜𝑓𝑡ℎ𝑒𝑡𝑟𝑜𝑢𝑔ℎ𝑠

Depth of irrigation water application required =25.344∗1000

614.4 = 41.25 mm/hr/section

Crop water requirement for tomatoes from CropWat = 5mm/day




60% of the irrigation water

Effective crop water requirement = 5𝑚𝑚/𝑑𝑎𝑦

0.6 = 8.333mm/day

Thus the irrigation schedule = 𝐺𝑟𝑜𝑠𝑠𝑐𝑟𝑜𝑝𝑤𝑎𝑡𝑒𝑟𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡


Irrigation schedule = 8.333∗60

41.25 = 12.12 min/day


Irrigation time required for 10 sections with 3 bays each = 12.12𝑚𝑖𝑛/𝑑𝑎𝑦∗10𝑠𝑒𝑐𝑡𝑖𝑜𝑛𝑠

60 𝑚𝑖𝑛

Irrigation time required for 10 sections with 3 bays each = 2.02 hrs

Irrigation time required for 2 sections with 1 bay each = 12.12𝑚𝑖𝑛/𝑑𝑎𝑦∗2𝑠𝑒𝑐𝑡𝑖𝑜𝑛𝑠

60 𝑚𝑖𝑛

Irrigation time required for 2 sections with 1 bay each = 0.404 hrs

Thus the total irrigation time per day is 2.424 hrs.

Total discharge required for the 3 ha greenhouse farm per day = (Total irrigation time in 10

sections*discharge per section of 3 bays) + (Total irrigation time in 2 sections * discharge per

section in 1 bay)

Total discharge required for the 3 ha green house farm per day = (2.02 * 25.344) + (0.404 *

8.448)

Total discharge required for the 3 ha green house farm per day = 54.61m3/hr thus approximately

gives 60m3/hr for 2.424hrs

5.2.4 Fertigation Requirements

The fertigation requirement for hydroponics is approximately 5litres of fertilizer/m3 of water.

Fertigation design involves selection of fertigation system. In this case the fertigation system

used is the Fertiget which is automated. The fertiget uses a venturi and therefore the design

involves the selection of the venturi size which is dependent on the fertigation requirement of

tomatoes hydroponically grown and discharge required per irrigation schedule of which is also

the fertigation schedule since fertilizer is provided with irrigation water. The fertiget is sized

depending on the fertigation duration for the whole farm and also the requirement per irrigation

schedule.


Table 5: Nutrient required at each stage growth of a tomato plant. Source: Pelemix’s experience,

Fertigation on wikipedia

Nutrient

Stage of

Growth

N P K Ca Mg Fe Zn Mg Cu

Planting 80-90 45 120 100 40 1 0.4 0.65 0.02

Flowering 140 45 180 100 40 1.2 0.5 0.75 0.05

Production 160 45 250 120 40 1.2 0.55 0.75 0.05

Total

(ppm)

390 135 550 320 120 3.4 1.45 2.15 0.12

From the table above the fertigation supplied throughout the growth of tomatoes is a total of

1,522.12ppm which is 1.52212L/m3. Since 40% of irrigation water is drained, an excess of this

requirement is applied thus hydroponics fertigation requirement = 1.52212

0.4= 3.8𝐿/𝑚3.

Industrial approximation takes this value as 5L/m3 to cater for unprecedented losses.

5.3 Design of main lines, sub-mains and valves

5.3.1 Sizing of the sub-mains

In sizing the sub-mains, the pressure at the inlet must be sufficient to supply water to the end of

the drip lines. From the manufacturer the operating pressure in the drip line specified. Since the

connection of the drip lines to the sub-main is at the start of the drip lines the start pressure of the

drip lines is the required end pressure of the sub-mains. The sub-main was designed such that it

branches from the hydrant and supplies water to section halfway up and halfway down i.e. the

hydrant is at the middle of the section and thus the sub-mains take water from the hydrant in two

directions up and down from the hydrant thus the flow in the main line was halved for the sub-

mains in order to achieve smaller pipe diameters thus less cost and also to ensure that the

working pressure is not too high.

5.3.1.1 Obtaining discharge in the sub-main

Discharge required in each sub-main in the section with 3 bays = 𝑇𝑜𝑡𝑎𝑙𝑑𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒𝑝𝑒𝑟𝑠𝑒𝑐𝑡𝑖𝑜𝑛

2


Discharge required in each sub-main in the section with 3 bays = 25.344

2 = 12.672m3/hr

That is 8 troughs*3bays = 24 troughs

There are two sub-mains in a section therefore each sub-main supplies to 12 troughs each.

Thus discharge required in each sub-main =

12 troughs ∗ 2 drip lines ∗ 64m length of the troughs∗1.65L/hr

0.2𝑚∗1000

Discharge required in each sub-main for the 3 bay section = 12.672m3/hr

To be used in Hydro-Calc Length of the sub-main in 3 bay section = 12.8m*3 bays = 38.4

2 = 19.2

m

Discharge required in each sub-main in the section with 1 bay = 𝑇𝑜𝑡𝑎𝑙𝑑𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒𝑝𝑒𝑟𝑠𝑒𝑐𝑡𝑖𝑜𝑛

2

Discharge required in each sub-main in the section with 3 bays = 8.448

2 = 4.224 m3/hr

That is 8 troughs*1bays = 8 troughs

There are two sub-mains in a section therefore each sub-main supplies to 4 troughs each.

Thus discharge required in each sub-main =

4 troughs ∗ 2 drip lines ∗ 64m length of the troughs∗1.65L/hr

0.2𝑚∗1000

Discharge required in each sub-main = 4.224 m3/hr

To be used in Hydro calc; Length of the sub-main in 1 bay section = 12.8m*1 bay = 12.8

2 = 6.4 m

5.3.1.2 Using hydro calc to size the sub-mains

Drip line end pressure from manufacturer = 20m, the drip line start/head pressure from hydro

calc head pressure is 20.69 m, velocity is 0.45 m/s and cumulative pressure loss is 0.69. The end

pressure of the sub-main is therefore 20.69 m. Cumulative pressure loss should be >3% thus

𝐶𝑢𝑚.𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒

𝑑𝑟𝑖𝑝𝑙𝑖𝑛𝑒𝑙𝑒𝑛𝑔𝑡ℎ∗ 100% =

0.69

32∗ 100% = 2.1562% thus appropriate selection of drip line

head pressure.

For the sub-main in the 3 bay section, the parameters to be used in hydro calc are flow rate

required as 12.672m3/hr, PVC pipe, length of sub-main as 19.2 m, end pressure of 20.69m and


using the Hazen William’s equation; the results obtained are head pressure of the sub-main as

21.29 m, cumulative pressure loss as 0.60 m, velocity as 2.03 m/s and nominal diameter of

50mm Class B. Cumulative pressure loss should be >3% thus 𝐶𝑢𝑚.𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒

𝑠𝑢𝑏−𝑚𝑎𝑖𝑛𝑙𝑒𝑛𝑔𝑡ℎ∗ 100% =

0.60

19.2∗ 100% = 3.125% which is approximately 3% thus appropriate head pressure and

diameter of pipe.

For the sub-main in the 1 bay section the parameters to be used in hydro calc are flow rate

required as 4.224 m3/hr, PVC pipe, length of the sub-main as 6.4 m, end pressure of 20.69m and

using the Hazen William’s equation; the results obtained are head pressure of the sub-main as

20.78 m, cumulative pressure loss as 0.09 m, velocity of 1.09 m/s and nominal diameter of

40mm of Class B. Cumulative pressure loss should be >3% thus 𝐶𝑢𝑚.𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒


0.09

6.4∗ 100% = 1.40625% which is approximately 3% thus appropriate head pressure and

diameter of pipe.

Each section has 1 hydrant that is required to have a flow of 25.344m3/hr from the discharge

required per section of 3 bays and 8.448m3/hr for the 1 bay section. For the hydrant the end

pressure of the hydrant is the head pressure of the sub-main thus it is 21.29m which is the

maximum between the 3 bay section and 1 bay section head pressure of sub-main. The head

pressure for the hydrant is obtained from hydro calc on the valve icon; the parameters used are

valve type as Pressure Regulating Valve (PRV), regular flow as 25.344m3/hr, the result obtained

is frictional loss of 8.89 thus the head pressure of the hydrant is 21.29m + 8.89 = 30.18m which

the end pressure of the main line.

5.3.2 Sizing of the main line

The design of the main line involved having multi-mainlines i.e. each section had its own main

line due to the different requirements of the different sections i.e. different varieties and different

fertilizer injections. These multi-mainlines are connected to a manifold and each mainline has a

valve to control a flow of 25.344m3/hr for each section in an irrigation session.


Length of the main line to be used in hydro calc to size the diameter of the main line is given by

length to the last section plus length from the pump house to the start of the farm.

Thus; Length of main line = length of 1 bay + length of 12 bays + (Length of 3 bay*0.75) +

measured length from pump house

Length of the main line = 12.8m + (12bays*12.8m) + (12.8m * 3bays * 0.75) + 74m = 268.4m,

approximately 270m

For the main line the parameters to be used in hydro calc are flow rate required as 25.344m3/hr,

PVC pipe, length of main line as 270 m, end pressure of 30.18m and using the Hazen William’s

equation; the results obtained are head pressure of the main line as 35.84 m, cumulative pressure

loss as 5.66 m, velocity as 1.35 m/s and nominal diameter of 90mm Class C. Cumulative

pressure loss should be >3% thus 𝐶𝑢𝑚.𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒


5.66

270∗ 100% = 2.0963%

which is approximately 3% thus appropriate head pressure and diameter of pipe.

5.3.3 Sizing of the irrigation hydrants or valves

Each section has 1 hydrant that is required to have a flow of 25.344m3/hr from the discharge

required per section of 3 bays and 8.448m3/hr for the 1 bay sections. The velocity in the main

line is 1.35m/s. To obtain the size of the valves for each of the sections:

Discharge required in the section of the 3 bays = Velocity * Area

Q = V * A 3.17

25.344m3/hr = 1.35m/s * Area thus; Area = 25.344

1.35∗3600= 0.005215𝑚2

Area = 𝜋𝐷2

4 ; D2 =


𝜋 ; D = √


𝜋 = √

0.005215∗4

𝜋 = 0.0815m = 3.2”

Discharge required in the section of the 1 bay = Velocity * Area

Q = V * A 3.17

8.448m3/hr = 1.35m/s * Area thus; Area = 8.448

1.35∗3600= 0.001738𝑚2

Area = 𝜋𝐷2

4 ; D2 =


𝜋 ; D = √


𝜋 = √

0.001738∗4

𝜋 = 0.047m =1.85”


There are 16 bays each with 8 hydroponic troughs, each trough has 2 drip lines/laterals; the

valves are placed as per the sections designed for management practices. There are 10 sections of

3 bays and 2 sections of 1 bay. Thus depending on the irrigation cycle of 12.12min per section as

per required flow each section has a valve. For the 10 sections the valve size is 3” to serve 48

laterals and for the 2 sections the valve size is 2” valve to serve 16 laterals.

5.4 Selecting the Irrigation Pump



Theoretically maximum suction for the operation of a pump is 6m but the steel tanks are on a

higher ground than the pump house thus the suction is termed as flooded suction i.e. head due to

suction and delivery is 0m, also the elevation head is zero, frictional losses in the fittings

especially the gravel filters is approximately 10m

The total head of the irrigation pump = 0m + 0m + 10m + 35.84m = 45.84m

Total discharge required is 25.344m3/hr


102∗𝑒) 𝑘𝑊 3.12

Where Q – flow in l/s



Thus power required, N = (25.344∗1000∗45.84

102∗3600∗0.6) = 5.273kW

Pump of 5.273kW is selected from manufacturer’s catalogue. A Grundfos pump with the

specifications of 97839207 NB 32-200/190 50 Hz was selected. The irrigation pump curve is

attached on the Appendix. The power is supplied by the farm’s power system.

5.5 Selecting the irrigation water U.V. cylinders and Filters


U.V. treatment pipes or units are cylindrical in shape with a diameter between 20cm and 30cm

and length of 1.5m The U.V. are selected from the manufacturer’s catalogue to cater for a flow

of 25.344m3/hr. The U.V. and gravel filters are obtained from Israel’s, John Deere.

Gravel filters and UV components based on the discharge per irrigation schedule to filter the

water to prevent clogging in the distribution pipes and drip line and treat pathogens in the drain

water respectively were selected. This is to ensure hygienic conditions in the troughs to prevent

diseases.

Gravel Filters are selected from manufacturer’s list to cater for the required discharge per

irrigation session which is 25.334m3/hr. 60% the flow is allowed for back flushing from

theoretical background. Thus the filters are selected for a flow that allows for back flushing. The

flow is obtained by:

Flow used to select filters = 𝐹𝑙𝑜𝑤 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 𝑝𝑒𝑟 𝑖𝑟𝑟𝑖𝑔𝑎𝑡𝑖𝑜𝑛 𝑠𝑒𝑠𝑠𝑖𝑜𝑛

0.6 =

25.344

0.6 = 42.24 m3/hr

Filters are selected with a flow of 42.24 m3/hr from manufacturer’s catalogue.

5.6 Sizing the fertigation system Fertigation required per irrigation schedule = Fertigation required per m3 * flow required per

irrigation schedule

Fertigation required per irrigation schedule = 5L/m3 * 25.334m3/hr =126.67L/hr

Venturi is selected from manufacturer’s catalogue for a flow of 126.67L/hr

Size of the fertiget = Fertigation required per irrigation schedule * Irrigation time

Size of the fertiget = 126.67L/hr * 2.424hrs = 307.05L

Fertiget is selected from manufacturer’s catalogue to cater for the volume of 307.05L

The fertilizer mixing tanks are recommended to be 2 tanks for fertilizer and 1 tank of acid. The

sizing of the fertilizer mixing tanks was done.

Sizing the fertilizer tanks for 3.3 days;

(Fertigation per day which is for 2.424hrs) * 3.3 days =307.05L* 3.3 = 1,000L


The Tank capacity 1,000L thus the fertilizer tanks were selected to be 1000L each. The acid tank

was designed to have a capacity of 500L half of the fertilizer tanks since it is used to regulate the

pH of the fertilizer mix injected into the main line. The tanks are Kentank plastic tanks. They are

selected as the shorter tanks and are open at the top to allow mixing of fertilizers.

5.7 Tank sizing for Irrigation The discharge required for the 3 ha farm is 60m3/day. Sizing the tanks for 2.5 days gives:

Size of the Genap steel tank = 60m3/day * 2.5 days = 150m3 which is a size that fits the

manufacture’s specifications and is not too costly.

5.8 Sizing of the drainage system Drainage layout is done in order to allow drainage by gravity. The land slopes at 1% in opposite

directions from the 4 m path. This is slope was obtained during the green house construction.

Drainage pipe is placed at the end of the troughs of 40% of the water is drained.

5.8.1 Sizing of the outlet of the troughs to the drainage pipe

1 trough has 2 drip lines; emitter discharge is 1.65 lph, emitter spacing = 0.2m, length of drip

line = 32m, Thus; No. of emitters per drip line = 32𝑚

0.2𝑚= 160 𝑒𝑚𝑖𝑡𝑡𝑒𝑟𝑠/𝑙𝑎𝑡𝑒𝑟𝑎𝑙

Total discharge in one trough = 160 emitters/lateral * 2 laterals * 1.65lph =528 lph

Drainage from 1 trough = 0.4 * 528lph = 211.2 lph = 0.2112m3/hr

Since drainage will be on gravity a velocity of 1m/s is required in the pipe thus;

For the drainage pipe for the hydroponic troughs the parameters to be used in hydro calc are flow

rate required as 211.2 lph, P.E pipe, length of drainage pipe as 32 m, end pressure of 20.69m

and using the Hazen William’s equation; the results obtained are head pressure of the drainage

pipe as 21.41 m, cumulative pressure loss as 0.72 m, velocity as 0.63 m/s and nominal diameter

of 20mm Class B. Cumulative pressure loss should be <3% thus 𝐶𝑢𝑚.𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒


0.72

32∗ 100% = 2.25% which is approximately 3% thus appropriate head pressure and

diameter of pipe.


5.8.2 Sizing the drainage pipe for the blocks vertical and across where the drain water is directed to a drain tank

There are 4 blocks for the 3 ha farm. Each block will have a drainage pipe where the hydroponic

troughs slope. For 1 block the total drainage flow is; given that there are 16 bays each with 8

troughs and drainage from 1 trough is 211.2 lph

Total drainage flow for 1 block = 211.2 lph * 16bays * 8 troughs each = 27,033.6lph which is

also the drainage from 16*8*2 = 256 laterals assuming that all the blocks are irrigated at the

same time.

Sizing the drainage pipe using hydro calc for 1 block involves sizing for the sections

cumulatively. The drainage pipe for each block is divided into to the first four sections which

include the 1, 1 bay section and 3, 3 bay sections giving a total of 10bays thus the drainage pipe

collects water for 80 troughs. The parameters to be used for this part are 211.2lph per trough, No.

of drainage pipes from the hydroponic troughs in the first part of the drainage pipe in each block,

Length of drainage pipe for each block which is 12.8m * 10 bays = 128m, end pressure of

21.41m and using the Hazen William’s equation; the results obtained are head pressure of the

drainage pipe as 23.53 m, cumulative pressure loss as 2.12 m, velocity as 1.71 m/s and nominal

diameter of 63mm Class B. Cumulative pressure loss should be <3% thus 𝐶𝑢𝑚.𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒

𝑠𝑢𝑏−𝑚𝑎𝑖𝑛𝑙𝑒𝑛𝑔𝑡ℎ∗

100% =2.12

128∗ 100% = 1.6563% which is approximately 3% thus appropriate head

pressure and diameter of pipe. Each block will have a drainage pipe of diameter 63mm PVC pipe

Class B for the first 10 bays. The second part of the drainage pipe for each block include the last

two sections which include 3 bays each giving a total of 6bays thus the drainage pipe collects

water for cumulative 80troughs + (6bays*8troughs/bay) = 128 troughs. The parameters to be

used for this part are 211.2lph per trough, No. of drainage pipes from the hydroponic troughs in

the second part of the drainage pipe in each block, Length of drainage pipe for each block which

is 12.8m * 6 bays = 76.8m, end pressure of 23.53m and using the Hazen William’s equation; the

results obtained are head pressure of the drainage pipe as 24.8 m, cumulative pressure loss as

1.27 m, velocity as 1.71 m/s and nominal diameter of 75mm Class B. Cumulative pressure loss

should be <3% thus 𝐶𝑢𝑚.𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒


1.27

76.8∗ 100% = 1.6536% which is


approximately 3% thus appropriate head pressure and diameter of pipe. Each block will have a

drainage pipe of diameter 75mm PVC pipe Class B for the last 6 bays cumulative of 16bays.

Sizing the main drainage pipe using hydro calc for the 3 ha farm involves sizing drainage pipes

for each of the four blocks cumulatively. For the first block parameters to be used are 211.2lph

per trough, No. of drainage pipes from the hydroponic troughs in 1st block which is 128, Length

of drainage pipe for 1st block which is 32m, end pressure of 24.8m and using the Hazen

William’s equation; the results obtained are head pressure of the drainage pipe as 25.33 m,

cumulative pressure loss as 0.53 m, velocity as 1.92 m/s and nominal diameter of 75mm Class

B. Cumulative pressure loss should be <3% thus 𝐶𝑢𝑚.𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒


0.53

32∗

100% = 1.6563% which is approximately 3% thus appropriate head pressure and diameter

of pipe.

For the second block parameters to be used are 211.2lph per trough, Cumulative No. of drainage

pipes from the hydroponic troughs in 1st block and the 2nd block which is 256, Length of

drainage pipe for 2nd block which is 32m, end pressure of 25.33m and using the Hazen





0.27

32∗


of pipe.

For the third block parameters to be used are 211.2lph per trough, Cumulative No. of drainage

pipes from the hydroponic troughs in 1st block, the 2nd block and 3rd block which is 384, Length

of drainage pipe for 3rd block which is 40m, end pressure of 25.6m and using the Hazen





0.39

40∗



of pipe.

For the fourth block parameters to be used are 211.2lph per trough, Cumulative No. of drainage

pipes from the hydroponic troughs in 1st block, the 2nd block, 3rd block and 4th block which is

512, Length of drainage pipe for 4th block which is 40m, end pressure of 25.99m and using the

Hazen William’s equation; the results obtained are head pressure of the drainage pipe as 26.33

m, cumulative pressure loss as 0.37 m, velocity as 1.38 m/s and nominal diameter of 140mm

Class B. Cumulative pressure loss should be <3% thus 𝐶𝑢𝑚.𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒


0.37

40∗

100% = 0.925% which is approximately 3% thus appropriate head pressure and diameter of

pipe.

5.8.3 Sizing the Drainage tank

The discharge from the main drainage pipe is 1 trough = 211.2lph

The total drainage discharge per section of 3 bays = 211.2lph * 24 troughs = 5068.8lph =

5.0688m3/hr

The total drainage discharge per section of 1 bay = 211.2lph * 8 troughs = 1,689.6lph

=1.6896m3/hr

The irrigation time is 2.424 hrs per day thus the total drainage per day is:

Total drainage per day = (5.0688m3/hr * 2.02 hrs) + (1.6896m3/hr * 0.404 hrs) = 10.92m3/ day

Sizing the drainage tank for a day’s drain;

Size of the drainage tank = 10.92m3/day; Thus the drainage tank was sized to 10,000L capacity.

This is because it will take double the time of irrigation for water to drain in to the tank. Since

the irrigation time is 2hr the drain time is approximately 4hrs.

5.9 Design of the recirculation System

Sizing the pipe that takes the drain water from the drainage tank through the pump, the media

filters and U.V was done using hydro calc. The parameters to be used are flow rate required as

4.505m3/hr, PVC pipe, length of pipe as 270 m, end pressure of 15m and using the Hazen

William’s equation; the results obtained are head pressure of the sub-main as 18.34 m,



B. Cumulative pressure loss should be >3% thus 𝐶𝑢𝑚.𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒


3.34

270∗

100% = 1.237% which is approximately 3% thus appropriate head pressure and diameter of

pipe.

5.9.1BoosterDrainage Pump selection

Booster pumps are placed in the drainage tanks to pump the water automatically when the tank is

full.



Theoretically maximum suction for the operation of a pump is 6m, the elevation head is

determined from 1% slope , frictional losses and operation pressure are determined from hydro

calc.

Calculating elevation head using 1% slope

0.01 = ∆𝑦

∆𝑥 =

∆𝑦

𝑒𝑙𝑒𝑣𝑎𝑡𝑖𝑜𝑛 𝑎𝑡 𝑙𝑜𝑐𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑑𝑟𝑎𝑖𝑛𝑎𝑔𝑒 𝑡𝑎𝑛𝑘−𝑒𝑙𝑒𝑣𝑎𝑡𝑖𝑜𝑛 𝑎𝑡 𝑡𝑟𝑒𝑎𝑡𝑚𝑒𝑛𝑡 𝑡𝑎𝑛𝑘=

∆𝑦

2530−1890=

∆𝑦

640

Thus ∆𝑦 = 640 ∗ 0.01 = 6.4𝑚

From hydro calc the frictional head losses are 3.34m and the operational head is 18.34m thus;

The total head of the irrigation pump = 6m + 6.4m + 3.34m + 18.34m = 34.08m

Total discharge required is 4.505m3/hr


102∗𝑒) 𝑘𝑊

Where Q – flow in l/s



Thus power required, N = (4.505∗1000∗34.08

102∗3600∗0.6) = 0.697kW


Pump of 0.697kW and head of 34.08m was selected from manufacturer’s catalogue. The pump

was selected from Grundfos as 97839201 NB 32-160.1/139 50 Hz. The power is supplied from

the farm’s power system.

5.9.2 Selecting media filter for drain water

The drain water per day is 10.92m3/day. The fertigation time which is the irrigation time is

2.424hr / day. Thus the discharge that is re-used is = 10.92

2.424 = 4.505m3/hr. The media filters are

selected based on the flow of 4.505m3/hr. From John Deere an Israel manufacturer of media

filter the F2000 Media Filter, 2 inch connection diameter, 16 inch body diameter, Minimum flow

rate of 6m3/hr , Maximum flow rate of 11m3/hr, 10m3/hr back flush flow rate and Item no. BSP

101043070 was selected.

5.9.3 Selecting of U.V. Cylinders for drain water

The U.V. treatment pipes or units are cylindrical in shape with a diameter between 20cm and

30cm and length of 1.5m The U.V. are selected from the manufacturer’s catalogue to cater for a

flow of 4.505m3/hr.

5.9.4. Sizing the treated water tank

The drain water per day is 10.92m3 thus designing the treated water tanks for 15 days;

Tank capacity = 10.92m3/day * 15 days = 163.5m3. The tank was sized to 150m3 which is an

available capacity of the Genap steel tanks, a company of the Netherlands.

5.9.5 Selecting of injection valves

The drain water per day is 10.92m3/day. The fertigation time which is the irrigation time is

2.424hr / day. Thus the discharge that is re-used is = 10.92

2.424 = 4.505m3/hr. The valve was selected

based on the flow of 4.505m3/hr. When the water is enough in the treated water tank, the valves

could be sized to the requirement in irrigation that is 25.344m3/hr which is a 2” valve.


5.10 Cost benefit Analysis

Sizing the valve from treated water tank; given that 5L/m3 of water is supplied in fertigation

5L/m3 * 0.4 = 2L/m3

Total drainage per day = 10.92m3/day

Fertilizers in drain water = 10.92 * 2 =21.84 L/day which is recycled.

The cost of installation of the system is obtained from the bill of quantities attached in Appendix.

The prices used in the bill of quantities were obtained from Irrico International Limited. The

summary of the bill of quantities is as shown below in Figure 23. The bills of quantities with

specific parts are in the Appendix D.

The cost of installation of the system is approximately Ksh.13, 195,838.26 which is quite costly

but in comparison with the returns from the sale of produce the system design is profitable and

viable.

The yield from hydroponic farming is approximately 585,000kg/yr/ha. The cost of 1 kg of

tomatoes in Kenya is approximately Ksh.110.

Total sales from maximum yield of hydroponic tomatoes for 3 ha farm = 585,000kg/yr/ha *

Ksh.110/kg * 3ha = Ksh.193, 050,000

Thus the profit margin = Ksh.193, 050,000 - Ksh.13, 195,838.26 = Ksh.179, 854.161.7 per year.

This implies that the cost of installation is recovered within the first year of sales of produce.


Figure 23: Summary of the bill of quantities attached in the Appendix D

UNIVERSITY OF NAIROBICOLLEGE OF ARCHITECTURE AND ENGINEERING


F21/1700/2010

Date: May 4, 2015

HM-CLAUSE FARM NANYUKITOMATO PRODUCTION UNIT PROJECT FOR A 3HA FARM

PRICED BILL OF QUANTITIES

GREENHOUSE DRIP IRRIGATION SYSTEM

COST

DESCRIPTION OF GOODS AMOUNT

KSH

1 UV WATER TREATMENT FOR IRRIGATION WATER 1,679,042.20

2 DRIP IRRIGATION 2,505,699.13

3 FERTIGATION AND CONTROLLERS 1,287,330.91

4 DRAINAGE COLLECTION, 1,081,553.94

5 HYDROPONIC TROUGHS 5,130,548.70

6 RECIRCULATION AND TREATMENT 1,511,663.38

GRAND TOTAL 13,195,838.26


5.11 Design Drawing

Figure 24: Irrigation layout

In Fig. 24, water is pumped from the main reservoir in the farm to a second reservoir where

water is stored. The water is then pumped from the second reservoir through gravel filters and

then U.V. cylinders. The rain water requires filtering of organic and gravel matter in order to

achieve hygienic conditions required by hydroponics system. The water goes to Genap steel

tanks whereby it is stored for irrigation. From the Genap steel tanks the water is pumped through

gravel filters again to achieve hygienic conditions required in hydroponics. The water is then

passed through the fertigation then to the main line manifold. At the main line manifold there are

valves that control irrigation to each main line of the fertigation zones. The main lines also have

valves at the different fertigation zones. The sub-mains are connected to the valves and the drip


lines are connected to the sub-mains. The drainage pipes are on each trough and on each block

vertically and across to the drain tank.


6.0 CONCLUSION AND RECOMMENDATIONS

7.1 Conclusions

The overall objective of this design was achieved. A complete recirculating hydroponic system

for a 3 ha greenhouse was obtained. If installed this project would cost Ksh.13, 195,838.26 but

within a year the incurred cost of installation if recovered and high profits are also achieved with

the cost of a kg of tomatoes being 110 shillings given that the yield of hydroponics tomatoes is

585,000kg/yr/ha. This system will over the years ensure maximum yield and quality of tomatoes

all year round and at the same time ensuring protection of the environment that is minimal waste

of water and fertilizers. The result would be reduced food scarcity, improved quality of life, and

increased profit margin for tomato farming for the 3 ha farm in Nanyuki and generally Kenyan

farmers.

The pertinent parameters were identified which included the crop data i.e. tomato planting

spacing which is 20cm x 20cm, the crop water requirement which was 5mm/day. The

dimensions of the farm were obtained using GPS coordinates. The actual area in the greenhouse

that would have hydroponic troughs was obtained using a trough spacing of 1.2m, distance

between one section and the next of 0.6m and also the width of the toughs which was 40cm.

Hydroponic dimensions were selected from manufacture’s specifications and the plant spacing.

There were 2 drip lines in each trough from management practices thus with a plant spacing of

20cm the width of the trough would be 40cm thus the dimensions of the troughs were selected

are 20cm x 40cm x 20cm. The medium used in the troughs was coco peat. The drip line was

selected from manufacture’s catalogue and appropriate discharge and pressure considerations

done on the drip line using hydro calc. The pressure variation graph was generated and is shown

in the Appendices.

The total flow required for each section of the farm was determined which was 25.344m3/hr for

the 3 bay sections and 8.448m3/hr .for the 1 bay sections. This flow was used in Hydro calc to

determine the size of the multi-mains i.e. a main line for each section and the sub-mains. This

flow was also used with a total pump head of 45.84m to select the irrigation pump. The pump


selected has a power of 5.273kW. The valves to control the flow to each section were sized

depending on the discharge required per section. The flow was also used in the selection of

gravel filters and U.V. The irrigation tank was sized depending on the discharge per section and

the irrigation schedule. The irrigation schedule was obtained as 12.12min/day/section. The total

discharge required in the farm per day was 60m3/day. The irrigation tanks were steel tanks of

150m3 sized to 2.5 days of irrigation. The fertigation system was sized to fertigation requirement

of 5L/m3. This was obtained from the specific requirement of tomato for each stage of growth as

shown in the results. The fertiget was sized to 3.3days requirement of fertilizer thus it would

have a capacity of 307.05L per day of fertigation. The two fertilizer tanks were sized to 3.3 days

too and the sizes were obtained as 1000L each and the acid tank as 500L. The drainage system

was sized depending on the flow drained per trough which was 211.2lph and also cumulatively

the first 10 bays then total drain flow from 16 bays. The main drainage pipe that would drain the

water to the drainage tank was sized depending on the flow drained from each block

cumulatively as obtained in the results. The drainage tank was sized to a day’s drain flow in

order to allow the water to be treated before being recycled. The capacity of the drainage tank

was obtained as 10,000L. The media filters, U.V. treatment unit and control valves were selected

depending on the flow that is drained per irrigation schedule. The booster pump that was placed

in the drainage tank was selected to a head of 34.08m and a discharge of 5m3/hr. The treated

water tank was sized to 15 days thus tank capacity was found to be 150m3.

7.2 Recommendations

The design outcome is a milestone towards a recirculating hydroponics system however the

following are some of the recommendations that would ease the maintenance of the system and

also increase the efficiency of the system. The recommendations include;

I. Automation of the system which would help in management of the irrigation and

fertigation requirement. That is the cabling of the green house in order to meet the

specific water and fertilizer requirements for each section. It would also involve

incorporating sensors that determine when to irrigate and also when get rid of the

medium or the recirculation water i.e. when the concentration of chemicals and presence

of pathogens is harmful that the drain water cannot be re-used.


II. The cost of fittings can further be reduced to fit to small scale farms and also make the

design viable to these farmers.

III. Awareness should be created on the benefits of hydroponics and also more critically the

environmental effects so that in a few years we would not be repairing the damage caused

by draining hydroponics nutrient solution.


7.0 REFERENCES

Pardossi A., Carmassi G., Diara C., Incrocci L., Maggini R., Massa D.(2011). Fertigation and

Substrate Management in Closed Soilless Culture. Dipartimento di Biologia delle Piante Agrarie,

Università di Pisa, Pisa.

Alberto Pardossi, (2011). Fertigation Management in Greenhouse Hydroponics. Euphoros

Workshop, Szentes HU. Retrieved from

https://www.wageningenur.nl/upload_mm/1/c/f/26821c36-eb95-4fcb-9dbb-

d6c51639a253_Alberto_Pardossi_English_version.pdf

Christie Emerson, (2014). Water and Nutrient Reuse within Closed Hydroponic Systems.

Electronic Theses & Dissertations, Paper 1096. Georgia Southern University. Retrieved from

http://digitalcommons.georgiasouthern.edu/cgi/viewcontent.cgi?article=2154&context=etd

Government of Western Australia, Department of water,(2013). Hydroponic plant growing.

Water Quality Protection Note 19 (WQPN 19). Retrieved from

http://www.water.wa.gov.au/PublicationStore/first/84604.pdf

Jeremy Badgery-Parker, (2002). Managing waste water from intensive horticulture: a wetland

system. Journal of New South Wales Government, Department of Primary Industries,

Agriculture. Retrieved from

http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0005/119372/horticulture-waste-water-

wetland-system-eng.pdf

New South Wales Government, Department of Primary Industries, Agriculture (2009).

Greenhouse Hydroponics. Retrieved from

http://www.dpi.nsw.gov.au/agriculture/horticulture/greenhouse/hydroponics

Fisher. P, 2015. Water Treatment Guidelines. Environment Horticultural Department, University

of Florida: IFAS Extension.


Fisher. P, 2011. Water Treatment: A grower’s guide for nursery and greenhouse irrigation.

www.WaterEducationAlliance.org

Mebalds, M., Hepworth, A.G., van der Linden, A., and Beardsell, D, 1995. Disinfestation of

plant pathogens in recycled water using UV radiation and chlorine dioxide in: Development of

Recycled Water Systems for Australian Nurseries. HRDC Final Report No. NY320.

Van der Gulik. T, 2003. Treating irrigation and crop wash water for pathogens. British Columbia

Ministry of Agriculture, food and fisheries: Water quality Fact sheet, Order No. 512.000-3.

Rimol Greenhouse Systems, (2015). Hydroponic Systems. Retrieved from

https://www.rimolgreenhouses.com/greenhouse-series/hydroponic-systems

George J. Hochmuth and Robert C. Hochmuth, (2001). Nutrient Solution Formulation for

Hydroponic Perlite, Rockwool, NFT Tomatoes in Florida. Horticultural Sciences Department,

Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University

of Florida. Retrieved from http://edis.ifas.ufl.edu/pdffiles/CV/CV21600.pdf

Louisiana State University, College of Agriculture, Horticulture (2013). Greenhouse Tomato

Production Manual. Retrieved from

http://www.lsuagcenter.com/en/our_offices/research_stations/redriver/features/research/horticult

ure/greenhouse+tomato+production+manual.htm

George J. Hochmuth and Robert C. Hochmuth, (2013). Keys to Successful Tomato and

Cucumber Production in Perlite Media. Department of Horticultural Sciences Department,

Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University

of Florida. Retrieved from http://edis.ifas.ufl.edu/pdffiles/HS/HS16900.pdf

Government of Alberta, Agricultural and Rural development, (2015).Commercial greenhouse

vegetable production. Retrieved from

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex1443


Cornell University, Biological and Environmental Engineering, (2014). Controlled Environment

Agriculture. Retrieved from http://www.cornellcea.com/

University of Massachusetts Armhest Extension, (2013). Hydroponic Greenhouse Production

Resources. Greenhouse crops and Floricultural Program. Retrieved from

http://extension.umass.edu/floriculture/fact-sheets/hydroponic-greenhouse-production-resources

Turner, Bambi (2008). How Hydroponics Works. HowStuffWorks.com. Retrieved from

http://home.howstuffworks.com/lawn-garden/professional-landscaping/alternative-

methods/hydroponics.htm/printable

Smart! Grow Intelligently, (2014). Hydroponics systems. Retrieved from http://www.smart-

fertilizer.com/articles/hydroponic-systems

Smart! Grow Intelligently, (2014). Fertigation. Retrieved from http://www.smart-

fertilizer.com/articles/fertigation

Smart! Grow Intelligently, (2014). pH adjustment in Fertigation. Retrieved from

http://www.smart-fertilizer.com/articles/pH-in-fertigation

Ezgrow garden, (2015). Types of Hydroponics Systems. Retrieved from

http://ezgrogarden.com/hydroponics/types-of-hydroponic-systems/

Rick Donnan, (1994). Nutrient Management in Hydroponics Systems – Part 2, Issue 14. Practical

hydroponics and greenhouses. Retrieved from

http://www.hydroponics.com.au/issue-14-nurient-management-in-hydroponics-systems-part-2/

Macharia Mwangi, (2014). Hydroponics: Growing crops without soil. Smart Farm Magazine.

Retrieved from http://www.smartfarmerkenya.com/page/article/98-hydroponics:-growing-crops-

without-soil


Isaac Mwangi, (2015). Hydroponics Give Kenyan Farmers Fodder For Thought. AFK Insider.

Retrieved from http://afkinsider.com/10663/crops-grown-in-water-signal-sea-change-of-

fortunes-for-kenyan-farmers/2/

F.M.Shitakha, (1986). An Assessment of the Irrigation Suitability of the Soils of Mia Moja and

Matanya farms, Laikipia district. Site evaluation report No. P78. Ministry of Agriculture-

National Agricultural laboratories. Kenya Soil Survey.

GoK, Ministry of Water and Irrigation, (2005). Practice Manual for Water Supply Services in

Kenya. Kenya- Belgium Study Consultancy Fund.

Steve Carruthers, (2002). Issue 63: Hydroponics as an agricultural production system. Practical

hydroponics and Greenhouses. Retrieved from

http://www.hydroponics.com.au/issue-63-hydroponics-as-an-agricultural-production-system/

Mbaka, J.N., Gitonga, J.K., Gathambiri, C.W., Mwangi. B.G., Githuka, P. and Mwangi, M.,

(2013). Identification of Knowledge and Technology gaps in high tunnel (‘greenhouse’) tomato

production in Kirinyaga and Embu Counties. Presentation during the 2nd National Science,

Technology and Innovation week, 13th - 17th May 2013 ,K.I.C.C., Nairobi.

Diane M. Camberato, Roberto G. Lopez, and Michael V. Mickelbart, (2015). pH and Electrical

Conductivity Measurements in Soilless Substrates. Purdue Extension, Commercial Greenhouse

and Nursery Production, Purdue University.


8.0 APPENDICES

9.1 Appendix A

This Appendix has the Design drawings

Figure 25: A.1 Sub-mains layout


Figure 26: A.2 Hydroponics Layout


Figure 27: A.3 Fertigation Layout


Figure 28: A.4 Drainage Collection


Figure 29: A.5 Hydrant fittings


Figure 30: A.6 Reservoir fittings


9.2 Appendix B

This Appendix contains graphs generated from softwares such as Hydro calc and CropWat. Also

other drawings used in design.

Figure 31: B.1 Drip line selection


Figure 32: B.2 pressure head along the sub-main for 3 bay section that was used in the design of

the sub-main


Figure 33: B.3 pressure head used in design of sub-main for 1 bay section


Figure 34: B.4 pressure head used in the mainline design


Figure 35: B.5 pressure head used in the design of trough drainage pipe


Figure 36: B.6 pressure head used in the design Block drainage 1

Figure 37: B.7 pressure head used in the design of Block drainage 2


Figure 38: B.8 pressure head used in the design of main drainage pipe 1

Figure 39: B.9 pressure head used in the design of main drainage pipe 2


Figure 40: B.10 pressure head used in the design of the main drainage pipe 3

Figure 41: B.11 pressure head used in the design of the main drainage pipe 4


Figure 42: B.12 pressure head used in the design of the pipe that directs drainage water to

treated water tank


Figure 43: B.13 Kc for tomatoes

Figure 44: B.14 Etc requirement


Figure 45: B.15 Climatic data

Figure 46: B.16 Irrigation Pump specifications


Figure 47: B.17 Drainage pump specifications


9.3 Appendix C

Figure 48: C.1 FERTIJET, Source: Google Images on fertigation

Figure 49: C.2 GALCON CONTROLLER, Source: Google images on Galcon controller


Figure 50: C.3 Greenhouse structure on site

Figure 51: C.4 Inside of Greenhouse structure on site


Figure 52: C.5 Rain water harvesting reservoir


9.4 Appendix D

This Appendix has the BOQ

Figure 53: D.1 BOQ for Drip irrigation



F21/1700/2010

Date: May 4, 2015

HM-CLAUSETOMATO PRODUCTION UNIT PROJECT OF 3HA



COST COST

DESCRIPTION OF GOODS U.O.M. QTY PRICE AMOUNT

KSH KSH

1.0 DRIP IRRIGATION

1.1 MULTILINES TO VALVES

1 3'' END CAPS PCS 12 332.00 3,984.00

2 90MM X 3'' VALVE SOCKETS PCS 12 417.60 5,011.20

3 90MM PVC ELBOWS PCS 48 374.10 17,956.80

4 90MM PVC PIPE CLASS C MTS 2460 253.00 622,380.00

5 90MM X 1'' SADDLE CLAMPS PCS 12 261.00 3,132.00

6 1'' GI RISER X 40CM PCS 12 56.55 678.60

7 1'' BALL VALVES PCS 12 661.20 7,934.40

8 1'' AIR RELEASE VALVE PCS 12 4,404.38 52,852.50

9 TANGIT KGS 46 852.60 39,219.60

10 PTFE PCS 96 21.75 2,088.00

SUB TOTAL 755,237.10

1.2 SUBMAINS AND HYDRANTS

1 90MM X 2'' SADDLE CLAMPS PCS 12 348.00 4,176.00

2 63MM X 2'' VALVE SOCKETS PCS 36 152.25 5,481.00

3 2'' HYDRAULIC VALVES C/W SOLENOIDS PCS 24 12,180.00 292,320.00

4 63MM PVC ELBOWS PCS 48 149.64 7,182.72

5 63MM PVC TEES PCS 36 217.50 7,830.00


7 63MM X 50MM REDUCER BUSH PCS 48 78.30 3,758.40


9 50MM PVC ELBOWS PCS 48 87.00 4,176.00

10 50MM X 1 1/2'' VALVE SOCKETS PCS 48 143.55 6,890.40

11 1 1/2'' ENDCAPS PCS 48 65.25 3,132.00

12 TANGIT KGS 43 852.60 36,661.80

13 PTFE PCS 168 21.75 3,654.00


1.3 PCND DRIP AND FITTINGS

1 16MM HYDROGOL PCND 1.65LPH AT 20CM SPACING MTS 34900 35.67 1,244,883.00

2 16MM START CONNECTOR C/W RUBBERS PCS 600 34.80 20,880.00

3 16MM PE PIPE PN6 MTS 600 18.42 11,054.12

4 16MM PE ENDLINES PCS 600 26.61 15,967.06

5 16MM DRIP TO DRIP CONNECTORS PCS 300 26.61 7,983.53

SUB TOTAL 1,300,767.71

TOTALS 2,505,699.13


Figure 54: D.2 BOQ for Fertigation and Controllers



F21/1700/2010

Date: May 4, 2015

HM-CLAUSE FARM, NANYUKITOMATO PRODUCTION UNIT PROJECT OF 3 HA



COST COST


KSH KSH

2.0 FERTIGATION AND CONTROLLERS

2.1 TANKS AND FITTINGS

1 1000 LITRES FERTILIZER TANKS PCS 3 8,321.74 24,965.22

2 500 LITRES FERTILIZER TANKS PCS 1 5,041.99 5,041.99

3 1'' TANK CONNECTORS PCS 8 87.00 696.00

4 1'' SOCKETS PCS 16 65.25 1,044.00

5 32MM X 1'' PE MALE ADAPTORS PCS 4 78.30 313.20

6 32MM X 1'' BARDERED CONNECTOR PCS 4 104.40 417.60

7 32MM PE PIPE CLASS B MTS 20 31.90 638.00

8 1'' SCREEN FILTERS PCS 4 3,915.00 15,660.00

9 1'' BALL VALVES PCS 4 661.20 2,644.80

10 PTFE PCS 30 21.75 652.50

11 FITTINGS AND ACCESSORIES SET 1 26,100.00 26,100.00

SUB TOTAL 78,173.31

2.2 FERTIGATION SYSTEM AND GALCON CONTROLLER

1 PC COMPUTER AND SOFTWARES PCS 1 104,400.00 104,400.00

2 GALCON WEXX CONTROLLER 40 OUTPUT PCS 1 348,000.00 348,000.00

3 LOW FLOW FERTIGET C/W EC, PH MONITOR PCS 1 452,400.00 452,400.00

4 12M3/HR AT 60M HEAD BOOSTER PUMP PCS 1 250,000.00 250,000.00

5 CONNECTIONS TO THE MAIN LINE AND FITTINGS PCS 1 52,200.00 52,200.00

6 TANGIT KGS 1 852.60 852.60

7 PTFE PCS 60 21.75 1,305.00

SUB TOTAL 1,209,157.60

TOTALS 1,287,330.91


Figure 55: D.3 BOQ for hydroponic troughs



F21/1700/2010

Date: May 4, 2015

HM-CLAUSE FARM, NANYUKITOMATO PRODUCTION UNIT PROJECT FOR A 3HA FARM



COST COST


KSH KSH

3.0 HYDROPONICS TROUGHS

3.1 HYDROPONICS TROUGHS

1 20CM x 30CM X 20CM HYDROPONICS TROUGHS COMPLETE MTS 16900 114.99 1,943,353.04

2 COCOPEAT KGS 84500 36.17 3,056,695.65


TOTALS 5,130,548.70


Figure 56: D.4 BOQ for Recirculation and UV Treatment



F21/1700/2010

Date: May 4, 2015

HM-CLAUSE FARM, NANYUKITOMATO PRODUCTION UNIT PROJECT FOR A 3HA FARM



COST COST


KSH US $

4.0 RECIRCULATION & UV WATER TREATMENT

4.1 RECIRCULATION SYSTEM

1 5M3/HR AT 35M HEAD SUBMERSIBLE PUMP SET PCS 2 75,000.00 150,000.00

2 CABLINGS SET 1 10,440.00 10,440.00

3 PUMP FITTINGS SET 2 43,500.00 87,000.00

4 LOW LEVEL AND HIGH LEVEL CUT OUT SWITCH SET 2 7,500.00 15,000.00

5 PRESS CONTROL PCS 2 18,000.00 36,000.00

6 50MM PVC ELBOWS PCS 12 87.00 1,044.00

7 50MM PVC TEES PCS 1 126.15 126.15

8 1 1/2'' BALL VALVES PCS 2 1,392.00 2,784.00

9 50MM X 1 1/2'' VALVE SOCKETS PCS 4 143.55 574.20


11 TANGIT KGS 8 852.60 6,820.80

12 PTFE PCS 30 21.75 652.50



4.2 RECIRCULATION COLLECTION TANKS

1 10,000L WATER RESERVOIR LINED PCS 1 67,200.00 67,200.00

2 TANK CONNECTORS PCS 2 6,720.00 13,440.00

3 150M3 GENAP TANKS COVERED PCS 1 304,500.00 304,500.00

4 TANK FOUNDATIONS SET 1 45,675.00 45,675.00



4.3 WATER TREATMENT SYSTEM

1 SINGLE PHASE 5M3/HR AT 40M HEAD SURFACE BOOSTER PUMP PCS 1 65,000.00 65,000.00

2 PUMP SUCTION PCS 1 30,450.00 30,450.00

3 PUMP DELIVERY PCS 1 39,150.00 39,150.00


5 5M3/HR UV WATER TREATMENT SYSTEM SET 1 125,000.00 125,000.00

6 2'' X 20'' SAND GRAVEL FILTERS PCS 2 95,000.00 190,000.00



4.4 RECIRCULATION TO THE IRRIGATION LINE

1 SINGLE PHASE 5M3/HR AT 50M HEAD SURFACE BOOSTER PUMP PCS 1 65,000.00 65,000.00

2 PUMP SUCTION PCS 1 30,450.00 30,450.00

3 PUMP DELIVERY PCS 1 39,150.00 39,150.00



6 1 1/2'' BALL VALVES PCS 1 1,392.00 1,392.00


8 2 1/2'' BALL VALVES PCS 1 3,915.00 3,915.00

9 2 1/2'' X 1 1/2'' MIXING VALVES PCS 1 25,000.00 25,000.00

10 75MM X 2 1/2'' FLANGE AND STUBS PCS 2 565.50 1,131.00

11 50MM X 1 1/2'' FLANGE AND STUBS PCS 2 426.30 852.60

12 5/8'' X 2'' BOLTS, NUTS AND WASHERS PCS 16 208.80 3,340.80

13 90MM PVC TEES PCS 1 417.60 417.60

14 90MM X 50MM REDUCER BUSH PCS 1 278.40 278.40

15 50MM PVC ELBOWS PCS 12 87.00 1,044.00



TOTALS 1,511,663.38


Figure 57: D.5 BOQ for UV treatment



F21/1700/2010

Date: May 4, 2015

HM-CLAUSE FARM, NANYUKITOMATO PRODUCTION UNIT PROJECT OF 3 HA


UV WATER TREATMENT

COST COST


KSH. KSH.

5.0 DRIP IRRIGATION WATER TREATMENT

5.1 PUMPSET

1 ELECTRIC PUMPSET 26M3/HR AT 46M HEAD PUMP, GRUNDFOS PCS 1 450,000.00 450,000.00

2 CONTROL PANEL PCS 1 65,250.00 65,250.00

3 CABLINGS PCS 1 13,050.00 13,050.00



5.2 FILTRATION SYSTEM

1 2'' x 20'' SAND GARVEL FILTERS C/W BACKFLUSH PCS 4 95,000.00 380,000.00

2 110MM X 4'' PVC FLAGE AND STUBS PCS 8 957.00 7,656.00

3 4'' WATER METER PCS 1 51,500.00 51,500.00

4 110MM PVC UNION GLUE TYPE PCS 1 2,697.00 2,697.00

5 110MM PVC ELBOWS PCS 10 826.50 8,265.00

6 5/8'' BOLTS, NUTS AND WASHERS PCS 32 208.80 6,681.60

7 GASKETS PCS 4 435.00 1,740.00

8 TANGIT KGS 1 852.60 852.60


5.3 UV WATER TREATMENT

1 26M3/HR UV WATER TREATMENT SYSTEM PCS 4 150,000.00 600,000.00



TOTALS 1,679,042.20


Figure 58: D.6 BOQ for Drainage collection



F21/1700/2010

Date: May 4, 2015

HM-CLAUSE FARM,NANYUKITOMATO PRODUCTION UNIT PROJECT FOR A 3 HA FARM



COST COST


KSH KSH

6.0 DRAINAGE COLLECTION,

6.1 DRAINAGE SYSTEM FOR IRRIGATION WATER

1 20MM START CONNECTOR C/W RUBBER PCS 1100 65.25 71,775.00

2 20MM FLEIXIBLE PIPE MTS 550 53.22 29,272.94

3 75MM ENDCAPS PCS 8 187.00 1,496.00

4 75MM DRAINAGE PIPES MTS 850 337.50 286,875.00



7 110MM ELBOWS PCS 20 2,465.00 49,300.00



10 125MM PVC ELBOWS PCS 12 2,465.00 29,580.00

11 140MM X 125MM REDUCER BUSH PCS 10 1,020.00 10,200.00


13 140MM PVC ELBOWS PCS 5 700.00 3,500.00


TOTALS 1,081,553.94

Documents

DESIGN OF A RECIRCULATING HYDROPONICS SYSTEM FOR A …ebe.uonbi.ac.ke/sites/default/files/cae/engineering/ebe/Kahehu... · university of nairobi school of engineering department of