Treatment and reuse of greywater for rye grass irrigation dissertation committee appointed by the scientific council of the discipline environmental engineering

Effect of the main factors on the total dry mass yield of ryegrass after 3 harvests without fertilizer supply .... Total dry mass yield of ryegrass after 6 harvests for all treatment com

POZNAŃ UNIVERSITY OF LIFE SCIENCES

FACULTY OF ENVIRONMENTAL ENGINEERING AND SPATIAL MANAGEMENT

MSc Eng Thanh Hung Nguyen

TREATMENT AND REUSE OF GREYWATER FOR

RYE-GRASS IRRIGATION

(OCZYSZCZANIE I PONOWNE WYKORZYSTANIE ŚCIEKÓW

SZARYCH DO NAWADNIANIA ŻYCICY TRWAŁEJ)

TREATMENT AND REUSE OF GREYWATER FOR

RYE-GRASS IRRIGATION

(OCZYSZCZANIE I PONOWNE WYKORZYSTANIE ŚCIEKÓW

SZARYCH DO NAWADNIANIA ŻYCICY TRWAŁEJ)

Doctoral dissertation THANH HUNG NGUYEN

Dissertation Committee appointed by the Scientific Council of the Discipline:

Environmental Engineering, Mining and Energy

to be defended in public

on Thursday 28 November 2019

at 11:00 a.m in Rada Wydzial room, Faculty of Environmental Engineering

and Spatial Management

Acknowledgements

I would like to extend my sincere thanks to my supervisor, Prof dr hab inż Ryszard Błażejewski, for his valuable support and supervision His advice, guidance, encouragement, and inspiration have been invaluable over the years Professor always keeps an open mind in every academic discussion I admire his critical eye for important research topics This dissertation would not have been completed without his guidance and support

Additionally, I would like to thank dr hab Marcin Spychała, for supporting supervisor and his cooperative work He gave me valuable help whenever I asked for assistance I have learnt many useful things from him

Further, I would like also to take this opportunity to thank the governments

of Poland and Vietnam through Agreement between the Government of the Republic of Poland and the Government of Vietnam giving the opportunity to study

in Poland and grant scholarships for my entire course

The warmest thank to my colleagues at Department of Hydraulic and Sanitary Engineering, Poznań University of Life Sciences, for the stimulating discussions, supporting my works, and for providing the friendly environment in which we have learnt and grown during the past 4+ years Special thanks to Mrs Jolanta Zawadzka for her help in laboratory measurements

Last but not least, I would like to thank my family and friends, for their constant love, encouragement, and limitless support throughout my life

CONTENTS

LIST OF FIGURES iv

LIST OF TABLES viii

Abbreviation x

ABSTRACT 1

1 INTRODUCTION 4

1.1 Background 4

1.2 Definitions of terms 5

1.3 Sustainable water resources management principles 6

1.4 Current and threatening water shortages 7

1.5 Importance of water reclamation and reuse 7

1.6 Justification for the study 8

2 LITERATURE REVIEW 10

2.1 Composition of greywater 10

2.1.1 Quantity of greywater 10

2.1.2 Quality of greywater 12

2.1.3 Characterisation of greywater usability 13

2.2 Greywater treatment 15

2.3 Greywater reuse for irrigation 16

2.3.1 Standards and guidelines 16

2.3.2 Potential of greywater reuse for irrigation 19

2.3.3 Storage and diversion of greywater for reuse 21

2.3.4 Impacts of greywater reuse for irrigation 23

2.3.4.1 Human health 23

2.3.4.2 Soil 23

2.3.4.3 Groundwater 25

2.3.4.4 Yields 26

2.4 Economics of greywater reuse 27

2.5 Perennial ryegrass and its characteristics 29

2.6 Observed gaps in the literature 30

3 PURPOSE, SCOPE AND RESEARCH METHODS 31

3.1 Purpose and scope of the research 31

3.2 Hypotheses 31

3.3 Research methods 32

3.3.1 Material 35

3.3.2 Design of experimental with ryegrass 38

3.3.3 Research process 40

3.3.4 Experimental process on ryegrass 40

3.3.5 Collecting data and analysis 44

4 RESULTS OF THE STUDY 46

4.1 Study on greywater reuse for ryegrass irrigation without fertilizer supply 46

4.1.1 Balance of substances in all treatment combinations 46

4.1.2 Main and interaction effects among factors influencing the dry mass yield of ryegrass without fertilizer supply 49

4.1.2.1 Total dry mass of ryegrass after 3 harvests without fertilizer supply 49

4.1.2.2 Total dry mass of ryegrass after 6 harvest without fertilizer supply 57

4.1.3 Regression model for dry mass yield of ryegrass 64

4.1.4 Effect of irrigation water factors on soil pH 65

4.1.5 Effect of irrigation water factors on soil EC 70

4.1.6 Potential contaminant removal from greywater by planted ryegrass 75

4.2 Study on greywater reuse for ryegrass with fertilizer supply 79

4.2.1 Main and interaction effects among factors of irrigation water on dry mass yield of ryegrass with fertilizer supply 79

4.2.1.1 Total dry mass of ryegrass after 3 harvests with fertilizer supply 79 4.2.1.2 Total dry mass of ryegrass after 6 harvests with fertilizer supply 82 4.2.2 Effect of irrigation water factors on soil pH 87

4.2.3 Effect of irrigation water factors on soil EC 90

5 DISCUSSION 95

5.1 Effect factors on total dry mass yield of ryegrass 95

5.2 The leachate quality 97

5.3 Effect factors on the change in soil pH and EC 98

5.4 Selecting factor settings for yield efficiency and reducing risk for planted soil irrigated with tap and greywater 100

6 CONCLUSIONS AND FUTURE RESEARCH 112

6.1 Conclusions 112

6.2 Future research 113

References 114

LIST OF FIGURES

Figure 1.1 Overview of greywater terms 5

Figure 2.1 Choosing methods for greywater treatment to reuse 16

Figure 3.1 Photo of experimental ryegrass in laboratory 33

Figure 3.2 The process of conducting the research 34

Figure 3.3 Compositions of raw and treated greywater used for irrigation 35

Figure 3.4 The lab-scale stand for greywater treatment 36

Figure 3.5 Particle size distribution of planted soil (sand) 37

Figure 3.6 The pot for experiment 37

Figure 3.7 Scheme of investigation with three factors (A, B, C) 38

Figure 3.8 The whole process of the study 40

Figure 3.9 Flowchart describing the entire experimental process on ryegrass 41

Figure 3.10 Schedule of experiment: (a) without fertilizer supply (Stage II); (b) with fertilizer supply (Stage III) 43

Figure 3.11 Flowchart for analysis from experimental design of the study 45

Figure 4.1 Balance of COD mass on all treatment combinations from irrigation water (Total mass matter = Uptake + Outlet) 46

Figure 4.2 Balance of total nitrogen mass on all treatment combinations from irrigation water 47

Figure 4.3 Balance of total phosphorus mass on all treatment combinations from irrigation water 48

Figure 4.4 Total dry mass yields of ryegrass after 3 harvests of all treatment combinations without fertilizer supply 50

Figure 4.5 Effect of the main factors on the total dry mass yield of ryegrass after 3 harvests without fertilizer supply 52

Figure 4.6 Two-way interaction of two factors affecting the total dry mass yield of ryegrass after 3 harvests (83 days) without fertilizer supply 53

Figure 4.7 The two-way interaction effects of the factors in the low and the high level of another factor after 3 harvests without fertilizer supply 54Figure 4.8 Response surface as a function: (a) of tap water and treated greywater (at raw greywater 5 mm/week); (b) of tap water and treated greywater (at raw greywater 15 mm/week); (c) of tap water and raw greywater (at treated greywater

5 mm/week); (d) of tap water and raw greywater (at treated greywater 15

mm/week); (e) of treated greywater and raw greywater (at tap water 5 mm/week); (f) of treated greywater and raw greywater (at tap water 15 mm/week) 56Figure 4.9 Total dry mass yield of ryegrass after 6 harvests for all treatment

combinations without fertilizer supply 57Figure 4.10 Effect of the main factors on the total dry mass yield of ryegrass after

6 harvests (179 days) without fertilizer supply 60Figure 4.11 Two-way interaction of two factors on the effects of the total dry mass yield of ryegrass after 6 harvests (179 days) without fertilizer supply 60Figure 4.12 The two-way interaction effects of the factors in the low and the high level of another factor after 6 harvests without fertilizer supply 61Figure 4.13 Response surface of total dry mass yield of ryegrass as a function: (a)

of tap water and treated greywater (at raw greywater 5 mm/week); (b) of tap water and treated greywater (at raw greywater 15 mm/week); (c) of tap water and raw greywater (at treated greywater 5 mm/week); (d) of tap water and raw greywater (at treated greywater 15 mm/week); (e) of treated greywater and raw greywater (at tap water 5 mm/week); (f) of treated greywater and raw greywater (at tap water

15 mm/week) 63Figure 4.14 Correlation between irrigation water and total dry mass yield of

ryegrass 64Figure 4.15 pH of soil before initial and after experiment for all treatment

combinations without fertilizer supply 66Figure 4.16 Effect of main factors on soil pH without fertilizer supply 68Figure 4.17 The two-way interaction of two factors on effect of the change in soil

pH after finishing experiment (179 days) without fertilizers‘ supply 69

Figure 4.18 Two-way interaction for all combinations of levels for the two factors

on effect of the change in the soil pH after finishing experiment without fertilizer supply 70Figure 4.19 Soil EC of all treatment combinations before initial and after

conducted experiment 71Figure 4.20 Effect of main factors on the change in soil EC 73Figure 4.21 The two-way interaction of two factors influencing soil EC after

finishing experiment (179 days) without fertilizer supply 73Figure 4.22 Two-way interaction for all combinations of levels for the two factors

on change in the soil EC after finishing experiment 74Figure 4.23 The average pH of irrigation water and leachate of all treatment

combinations during experiment 75Figure 4.24 The average EC of irrigation water and leachate of all treatment

combinations during experiment 76Figure 4.25 COD of leachate from all treatment combinations for mean COD influent of raw greywater and treated greywater were 320 and 120 mg.dm-3,

respectively 77Figure 4.26 Total nitrogen concentration of leachate from all treatment

combinations 78Figure 4.27 Total phosphorus concentrations of leachate from all treatment

combinations 78Figure 4.28 Total dry mass yield of ryegrass after 3 harvests of all treatment

combinations with fertilizer supply 80Figure 4.29 Main factors affect on the total dry mass yield of ryegrass after three harvest times with fertilizer supply 81Figure 4.30 The two-way interaction of two factors on the total dry mass yield of ryegrass after three harvest times with fertilizer supply 82Figure 4.31 Total dry mass yield of ryegrass after six harvests for all treatment combinations 83

Figure 4.32 Main factors affect on the total dry mass yield of ryegrass after six harvests with fertilizer supply 85Figure 4.33 The two-way interaction of two factors on the total dry mass yield of ryegrass after six harvests with fertilizer supply 86Figure 4.34 Two-way interaction for all combinations of levels for the two factors

on the total dry mass yield of ryegrass with fertilizer supply 86Figure 4.35 Soil pH for all treatment combinations after experiment with fertilizer supply 87Figure 4.36 Two-way interaction of two factors on the change in soil pH after six harvests with fertilizer supply 89Figure 4.37 Two-way interaction for all combinations of levels for two factors soil

pH with fertilizer supply 89Figure 4.38 Soil EC for all treatment combinations before and after finishing

experiment with fertilizer supply 90Figure 4.39 Main effects of factors influencing soil EC 92

Figure 4.40 Two-way interaction of two factors influencing soil EC after six

harvests with fertilizer supply 93Figure 4.41 Two-way interaction impact for all combinations of levels for two factors on change in the soil EC with fertilizer supply 94

LIST OF TABLES

Table 2.1 Water consumption and generated greywater in countries in the world

11

Table 2.2 Greywater quality in chosen countries 12

Table 2.3 Quality of greywater from household devices and appliances 13

Table 2.4 Some regulations/guidelines of water reuse for irrigation 18

Table 2.5 Costs for greywater treatment systems 29

Table 3.1 Model matrix for full factorial experimental design 38

Table 3.2 The matrix of experimental design (Full factorial experimental design) 40 Table 3.3 Volumes of irrigation water for each irrigation time interval (3 days) 42

Table 4.1 COD and nutrient uptake by pots during whole experiment 49

Table 4.2 ANOVA table for effect of all factors on total dry mass yield of ryegrass after three harvests without fertilizer supply 51

Table 4.3 ANOVA for fitting model with 6-effect to the total dry mass yield of ryegrass after 3 harvests without fertilizer supply 52

Table 4.4 ANOVA table for effect of all factors on total dry mass yield of ryegrass after six harvests without fertilizer supply (intercept not shown) 58

Table 4.5 ANOVA for fitting model with 5-effect to the total dry mass yield of ryegrass after six harvests without fertilizer supply 59

Table 4.6 Final model parameters 65

Table 4.7 ANOVA table for all factors on effect of the change in soil pH (with transformed exp(pH)) 67

Table 4.8 Results from fitting model of 3-effects on soil pH describing by transformed soil pH after experiment (179 days) without fertilizer supply 67

Table 4.9 ANOVA for effect of all factors on changing EC of planted soil 71

Table 4.10 ANOVA for fitting model with 6-term effects describing the change in soil EC after experiment without fertilizer supply 72

Table 4.11 ANOVA for effect of all factors on total dry mass yield of ryegrass after

3 harvests (after 83 days) with fertilizer supply (intercept not shown) 80Table 4.12 ANOVA for effect of all factors on total dry mass yield of ryegrass after six harvests with fertilizer supply 83Table 4.13 ANOVA for fitting model with 2- effects to total dry mass yield of

ryegrass after 6 harvests with fertilizer supply 84Table 4.14 ANOVA for effect of all factors on soil pH with fertilizer supply 88Table 4.15 ANOVA for fitting model with 1-effect on soil pH after experiment with supply fertilizer 88Table 4.16 ANOVA for effect of all factors on soil EC on transformed soil EC 91Table 4.17 ANOVA for fitting model with 4- effect on the change in soil EC

(transformed EC) after experiment with supply fertilizer 92Table 5.1 Matrix for selecting factor settings for yield efficiency for ryegrass and reducing risk of planted soil (for only main factors) 101

- TSS: Total suspended solids

- WHO: World Health Organization

ABSTRACT

Greywater combined with tap water and raw greywater from laundry, bath and washbasin was studied to evaluate effect of the irrigation water factors on the total dry mass yield of ryegrass and soil The greywater was treated in lab-scale set-up constructed out of lamella settler and filters The full factorial experiment with two levels (low level 5 mm/week, and high level 15 mm/week) for three factors

of irrigation water was designed After preliminary tests (stage I), the experiment was carried out for two cases: without fertilizer supply (stage II) and with fertilizer supply (stage III) lasting 186 days each Ryegrass was harvested 6 times during experiment, the total dry mass yields of 3 and 6 harvests were evaluated Soil pH and EC were measured before and after finish of each experimental stage

The results of study show that all main factors (tap water, treated greywater, raw greywater) influenced significantly the total yield of ryegrass after three and six harvests in stage II The most important factor influenced the total yield was treated greywater Moreover, all interactions between two factors had significant effect on the total yield, except for interaction between treated greywater and raw greywater after 6 harvests The experiment of stage II showed that tap water, treated greywater and their interaction had significant effect on soil

pH, similarly all factors of irrigation water and their interactions influenced on soil

EC Treated greywater was the most important factor influencing on soil pH, while tap water was decisive in the case of soil EC

In the experimental stage III, there were no significant effects of any factors and their interactions on the grass yield after 3 harvests However, interaction between tap water and raw greywater as well as between treated greywater and raw greywater had significant effects on the total yield after six harvests Soil pH was significantly influenced by interaction between tap water and raw greywater while soil EC by all main factors and interactions between tap water and treated greywater as well as between tap water and raw greywater, in which tap water was the most important factor

In addition, the quality of leachate have tended to improve after 51 days of ryegrass growth till the end of stage II, indicating high treatment efficiency of greywater in the root zone

Keywords: greywater, irrigation, tap water, greywater reuse, perennial ryegrass

STRESZCZENIE

Badania miały na celu ocenę wpływu nawadniania mieszaniną wody wodociągowej, ścieków szarych surowych (z pralni, wanny i umywalki) i ścieków szarych oczyszczonych na plon suchej masy życicy trwałej oraz na glebę Ścieki szare były oczyszczane w układzie laboratoryjnym, zbudowanym z osadnika lamelowego i filtrów Zaplanowano i zrealizowano pełne doświadczenie wieloczynnikowe dla dwóch poziomów nawadniania (poziom niski: 5 mm/tydzień i poziom wysoki: 15 mm/tydzień) dla trzech czynników Po ukończeniu badań wstępnych (etap I) przeprowadzono doświadczenie dla dwóch wariantów: bez nawożenia (etap II) i z nawożeniem (etap III), trwającymi 186 dni każdy Życicę ścinano sześciokrotnie w trakcie doświadczenia, oceniano plony suchej masy całkowitej dla trzech i sześciu zbiorów Pomiar pH i przewodności elektrycznej gleby wykonywano przed i po zakończeniu każdego etapu doświadczenia

Wyniki badań wykazały, że wszystkie główne czynniki (woda wodociągowa, ścieki szare surowe i ścieki szare oczyszczone) istotnie wpływały na całkowity plon życicy po trzech i sześciu zbiorach w II etapie badań Najistotniejszym czynnikiem wpływającym na plon życicy były oczyszczone ścieki szare Ponadto wszystkie oddziaływania między dwoma czynnikami miały istotny wpływ na plon, z wyjątkiem oddziaływania między ściekami szarymi oczyszczonymi a ściekami szarymi surowymi po sześciu zbiorach Doświadczenie II etapu wykazało, że woda wodociągowa, ścieki szare oczyszczone i ich wzajemne oddziaływanie miały istotny wpływ na pH gleby; podobnie wszystkie czynniki i ich wzajemne oddziaływanie miały wpływ na przewodność elektryczną gleby Ścieki szare oczyszczone były najistotniejszym czynnikiem wpływającym na pH gleby, natomiast woda wodociągowa miała decydujące znaczenie dla przewodności elektrycznej gleby

W III etapie doświadczenia nie stwierdzono istotnego wpływu poszczególnych czynników i ich wzajemnych oddziaływań na plon życicy po trzech zbiorach Jednak oddziaływania między wodą wodociągową i ściekami szarymi surowymi oraz między ściekami szarymi oczyszczonymi i ściekami szarymi surowymi miały istotny wpływ na plon po sześciu zbiorach Oddziaływanie między wodą wodociągową a surowymi ściekami szarymi miało istotny wpływ na pH gleby, natomiast wszystkie główne czynniki oraz ich interakcje, a także interakcje

między wodą wodociągową i ściekami szarymi surowymi miały wpływ na przewodność elektryczną gleby, a najistotniejszym czynnikiem okazała się woda wodociągowa Ponadto jakość odcieku uległa poprawie po 51 dniach wzrostu życicy i utrzymywała się do końca etapów II, co wskazuje na dużą skuteczność doczyszczania ścieków szarych w strefie korzeniowej

Słowa kluczowe: ścieki szare, nawadnianie, woda wodociągowa, wykorzystanie

ścieków, życica trwała

1 INTRODUCTION

1.1 Background

Water is essential for all life, and freshwater is one of the most important resources in all human activities However, it is becoming shortage because of urbanization, population growth, climate change, etc Recently, water shortage is happening not only in some countries but also expending over worldwide According to the World Water Assessment Programme (WWAP), about three billion people in parts of Asia and Africa will be faced with water shortages in 2025 (WWAP, 2012) Mekonenn and Hoestra (2016) reported that two-thirds of the global population (4.0 billion people, mainly in India and China) live under conditions of severe water scarcity at least one month of the year, and half a billion people face severe water scarcity all year round (Mekonnen and Hoekstra, 2016)

In order to reduce water shortage stress, one of the ways that has potential

is wastewater treatment reuse for some human activities Hence, greywater is emerging and considering as an alternative resource if we have a reasonable treatment for reuse It looks a resource and has the potential to cope with water scarcity because of low concentration of contaminants and pathogens, accounting for a significant volume of wastewater discharge from household Moreover, greywater containing some nutrients has potential to stimulate for developing plant (Ghaitidak & Yadav, 2013) In addition, treated greywater is applied for toilet flushing that can save from 40 to 60 litres/p.day (Gross et al., 2015) However, the reuse of treated greywater depends on many factors as living cost, technology, available resources, water scarcity level, regulatory policies and environmental concerns Treated greywater reuse is a method to save water resource which is closely linked due to the greywater accounts for two-thirds of the total domestic wastewater from households Moreover, it contributes to decrease in wastewater flow into central wastewater treatment plant (Morel & Diener, 2006)

Greywater reuse for irrigation has to treat ensures reducing health risk, soil, aesthetic, odour Especially, greywater reuse will be beneficial and efficient when applying a suitable treatment method for a specific purpose of reuse However, at present, this issue is still ambiguous and there have not been many studies published

1.2 Definitions of terms

Greywater is defined as wastewater from households which includes many

flows from baths, showers, tubs, washbasin and laundry machines without kitchen (kitchen sinks, dishwashers), and toilets (AL- Jayyousi, 2003; Roesner et al., 2006) However, some different definitions of greywater that include all sources from a household, excepting that from toilets exist (Gross et al., 2015, Ludwig, 2007) In addition, Gross et al (2015) distinguished two categories: light greywater (generated from bath, shower and wash basin), and dark greywater (generated from kitchen sink and washing machine) Overview of greywater terms is shown in figure 1

Wastewater from household

Light greywater

Dark greywater

Bath and shower

Washbasin

Toilets

(with water closets)

Figure 1.1 Overview of greywater terms For the purpose of this study, greywater is defined as a household wastewater from bath and shower, laundry machine, hand basin; excluding that from kitchen

Greywater reuse means using raw greywater or treated greywater for other

consumptions of human In more detail, treated greywater is used to substitute tap water for an active purpose which is not required for drinking water such as irrigation, washing street, toilet flushing, etc Greywater reuse has a potential to remarkedly reduce using tap water and water costs in households

Reclaimed water is a term synonymous with recycled water; it is

wastewater that is treated by many processes to meet specific water quality criteria (Asano et al., 2007)

In addition, some terms were defined by Asano et al (2007) such as potable reuse, directly potable reuse, indirectly potable reuse Non-potable reuse that means all water applied for reuse from wastewater treatment processes does not associate with directly and indirectly potable reuse In here, directly potable reuse that is advancing wastewater treatment supplies directly into the source of a water treatment plant while water for indirect potable reuse is stored in lake, reservoir, or groundwater before using

non-1.3 Sustainable water resources management principles

Water demand is increasing because of population growth and human activities while water resources are deteriorating in quality and water scarcity over the world Therefore, humankind needs a strategy for the sustainable management of water resources It plays a crucial role to ensure current water demand and safeguard water resources for future generations

One of the criteria for sustainable water resources management is a sustainable water resources system It was defined by American Society of Civil Engineers as ―Sustainable water resources systems are those designed and managed to fully contribute to the objectives of society, now and in the future, while maintaining their ecological, environmental, and hydrological integrity.‖ (Asano et al., 2007) According to Asano (2017), to ensure the sustainability of water resources management one needs to conduct water conservation, water reclamation and reuse and many different managements as preserve ecosystems, encourage water reclamation and reuse, or design for resilience and adaptability (Asano et al., 2007)

Doubtless, water reclamation and reuse are important ways to contribute to sustainable water resources management The AWWA research foundation report (1999) showed that total water uses in a single-family home with water conservation was lower by 32% than without water conservation Besides, greywater reuse is also an essential factor for sustainable water resources management because it is not only improving the state of water shortage but also water conservation sources

1.4 Current and threatening water shortages

Water shortage is not a new issue in dry continents that often face it as Australia, Southwest America, Africa, Middle East However, it is becoming more frequent and long-lasting not only in arid or semi-arid regions but also expanding

to cover the world in the context of global climate change and the steady population growth Many countries in the Middle East and North Africa are facing severe water scarcity which is also spreading to Asia and South Africa (Lazarova and Akica, 2005) This problem is increasing because water availability is limited

by agricultural activities, urbanization together with climate change, threatening ecosystems over the globe Indeed, the areas where two-thirds of the world‘s population lives are always facing water shortages for at least one month in the year (WWAP, 2017) Moreover, one half of the population living in India and China facing water shortages (WWAP, 2017) In the Global Risks Report of the World Economic Forum (2015), water supply crisis was identified as the highest top for risk level for our current times and future (Forum, 2015) With the current threat level, the World Wide Fund for Nature (WWF) predicts that two-thirds world‘s

(https://www.worldwildlife.org/threats/water-scarcity)

1.5 Importance of water reclamation and reuse

Water reclamation and reuse is one of the crucial ways for sustainable water resources management On-site treated wastewater reuse reduces burden for conveyance system to centralized waste water treatment plants Water supply

of high quality can be supplemented by alternative reclaimed water According to Gross et al (2015), potable water was saved from 10-30% of the urban water demand if greywater in the household has been reused

Water reuse plays an important role to reduce water shortage stress and is

a sustainable water resource management method To cope with water scarcity, many countries as Australia, the United States (US), and many countries in the Middle East have applied greywater reuse Moreover, they are interested in developing policies and encouraging the development of technology to greywater reuse effectively and safely (Pinto et al., 2010, Reichman et al., 2013) Guidelines for reuse of greywater have been issued in the United Kingdom (UK), Australia,

Israel, and California (US) (Oron et al., 2014) The World Health Organization (WHO) also issued a guideline that only required control of microorganisms (the number of helminth eggs and E coli) for restricted and non-restricted greywater reuse for agricultural irrigation (WHO, 2006) Besides, many technological solutions have also been applied as physical, chemical, biological process for greywater treatment to increase its quality and safety for reuse (Li et al., 2009) Depending on the purposes of reuse that raw greywater can use direction, dilution with freshwater, or combined with freshwater for irrigation; or treatment achieves a standard for reuse in household such as flushing toilets, irrigation

Raw greywater or primarily treated greywater in a single household can be applied for on-site reuse to irrigate grass, landscape/plants in gardens Irrigation for grass or landscape plants does not need high-quality water as potable water so greywater is easily accepted because of enough the amount of irrigated water, presence nutrients, and no requirements of high quality (Matos et al., 2012) According to Pinto and Maheshwari (2010), using the water for irrigation of gardens and grass around home was consumed about 30% of total tap water in many cities in Sydney (Australia) Therefore, an appropriate irrigation design for greywater reuse in the gardens can save 38% of potable water (AL- Jayyousi, 2003) Greywater treatment for reuse has potential benefits because of water saving and water availability However, to achieve high efficiency, it is necessary

to determine the degree of reasonable treatment as well as the object and effect of the application Many challenges present in treatment and greywater reuse in the household as technology, operation, investment costs Therefore, the technologies

of treatment and greywater reuse must be affordable cost and simple operation

1.6 Justification for the study

Greywater reuse is an example of closing the loop of water and energy circulation ―at the source‖ Such approach is welcomed by many countries all over the world, including Poland and Vietnam However, many related phenomena are not well recognized and many practical problems remained unsolved

The aim of this study is to assess the grass yields of a chosen species

(ryegrass) when greywater reuse after a reasonable treatment process (treated greywater) is adopted for irrigation Additionally, impact of the applied greywater (raw and treated) on the planted soil and potentially on groundwater (by determining leachate quality) will be assessed

day-1 and 60%-70% of this water supply become greywater (Adi et al 2014) while in developing countries it was about 20–30 dm3.

p-1.day-1 of greywater generated (Li et al., 2009) Indeed, in the USA, greywater was generated from laundry, baths and shower reached 127 - 151 dm3.p-1.day-1 (Yu et al., 2013) Moreover, following Guidelines for residential properties in Canberra 2007, average greywater of a household generated from laundry and bathroom was 300

dm3.house-1.day-1 (Australian Capital Territory, 2007) However, Polish study by Dobrzański and Jodłowski (2014) conducted on single houses during six months recorded average volume 24.6 dm3.p-1.day-1 of greywater which was collected from washing basin, shower, and washing machine on average 4.7 dm3.day-1, 13.8

dm3.day-1, and 6.1 dm3.day-1, respectively Merc and Stępniak (2015) reported that the daily water consumption per person in Poland was approximately 95 dm3 Moreover, Hotloś (2010) reported that unit volume of consumed water was consumed equal to 101 dm3.p-1.d-1, (another study in 2008 showed 112.6 dm3.p-1.

day-1 in summer, 96.8 dm3.p-1.day-1 in winter) and 86 -112 dm3.p-1.day-1 (in 2008), respectively (Bugajski and Kaczor, 2005) Furthermore, according to the study of Bugajski and Kaczor (2005), the water (hot and cold water) volume used in bathroom including bath, laundry, and toilet flushing was 73.2 dm3.p-1.day-1 (accounting for 73% of water consumption in the household) (Bugajski and Kaczor, 2005)

Following Matos et al (2012), the average greywater from bath, washing basin, and washing machine in Portugal was 38,2 dm3.p-1.day-1, 10,4 dm3.p-1.day-1, and 7,5 dm3.p-1.day-1 (total greywater was generated 56,1 dm3.p-1.day-1), respectively (Matos et al., 2012) Furthermore, in a water scarcity country, Israel,

40, 15, and 13 dm3.p-1.day-1 the volume of greywater were generated from bath

and shower, washing basin, and washing machine, respectively (Friedler, 2004) The contribution of greywater generated from many sources in some countries is shown in table 2.1 The percentage contribution of greywater from sources of water consumption per person.day in the household of three studies separately of Jadłowski and Mucha (2010), Ghaitidak and Yadav (2013), and Gross et al (2015) is not significantly different.

Table 2.1 Water consumption and generated greywater in countries in the world

Country Water use

Washing basin

Kitchen sink

Dish washer

2014) Poland 101 73.2 (**) 27.8 (Bugajski,

Kaczor 2005)

Moreover, the ratio between water consumption and greywater generation

is also different in many countries These ratios are from 0.49 to 0.77 (Gross et al.,

2015, Dobrzański and Jodłowski, 2014)

Additionally, the amount of greywater production from households fluctuates greatly in hours From 7:00 to 9: 30 and between 17: 30 and 20:00, the flow rate of generated greywater was the maximum due to many activities in the households (Eriksson et al., 2009) Likely, water usage hourly maximum in household in Perth, Western Australia occurred at 6 – 8 a.m and 6 - 8 p.m during summer (Coghlan and Higgs, 2003) Furthermore, the amount of water consumed varies by month of the year, day of the week, and hour of the day A study of Bugajski and Kaczor (2005) has shown that the highest amount of water was consumed in August, and the lowest in April; the highest on Saturday, Sunday, and the lowest on Thurday Specially, maximum daily peak factor laid between 1.4 and 2.4, the highest on days of May and the lowest on days of December (Bugajski and Kaczor, 2005) Thus, building a reservoir to ensure the flow of greywater for reuse and the uniformity of its composition is essential

2.1.2 Quality of greywater

Greywater quality is highly variable It depends not only in living standards, social and cultural area of residents, water shortage level but is also related to the trace of many categories and production materials of soap, toothpaste, salt, shampoos, detergents (Gross et al., 2015) The greywater quality is different in many countries, which is shown in table 2.2

Table 2.2 Greywater quality in chosen countries

Parameters India 1 Jordan 2 Germany 3 Israel 4 UK 5 USA 6 Poland 7

pH 7.3-8.1 6.4-7.9 7.6 6.3-8.2 6.6-7.6 6.4 7.33 Turbidity (NTU) 49 29 23-35 26.5-164 31.1 114

EC (mm.S-1) 89-703 64.5 120-170 32.7 23 675

TS (mg.dm-3) 497 659-2653 777-2891 TSS (mg.dm-3) 100-283 94-845 30-298 37-153 17 360 COD (mg.dm-3) 250-375 58-1712 109 840-1340 96-587 1240 BOD 5 (mg.dm-3) 100-188 36-942 59 74- 890 39-155 86 305 Total oil (mg.dm-3) 7 164 Tot.N (mg.dm-3) 6.44-52 15.2 10-34.3 4.6-10.4 13.5 6.2 Nitrate (mg.dm-3) 0.67 0.68 0.7-3.5 3.9 Tot P (mg.dm-3) 0.012 0.69-52 1.6 1.9-48 0.4-0.9 4 MBAS (mg.dm-3) 39 0.3 3.3-61 150 Na+ (mg.dm-3) 32-50 70-302 89-641 Ca2+ (mg.dm-3) 0.13 15.1-23 79.6 Mg2+ (mg.dm-3) 0.11 24-60 47.6

FC (CFU/100.cm3) 13-3.105 1.4.105

3.5.104-4.106

(1) (Parjane and Sane, 2011), (2) (AL-Hamaiedeh, 2010), (3) (Merz et al., 2007), (4) (Gross

et al., 2015), (5) (Jefferson et al., 2004; Birks and Hill, 2007; Pidou et al., 2008), (6) (Jokerst et al., 2011), (7) (Dobrzański and Jodłowski, 2014)

The quality of greywater depends on sources of generation, the contamination components are greatly variable as shown in table 2.3 following study of Ghaitidak (2013) (Ghaitidak and Yadav, 2013) In table 2.3, the quality of greywater from bath, shower, washing basin, or washing machine source is lower than from kitchen sink and dishwasher Although, kitchen sink and dishwasher account for 31% of total volume of domestic greywater, the concentration of contaminants in kitchen sink account for a higher ratio of total load of COD, total oil, and methyl blue active substances (MBAS) were 42%, 43%, and 40%, respectively (Friedler, 2004) Moreover, the greywater from dishwasher contributed to the increase sodium adsorption ratio (SAR) because the way that

dishwasher salt works is by providing sodium for the dishwasher‘s ion exchange resins Analysis of greywater characteristics from many sources shows that the nutrients (nitrogen, phosphorus) are present in all sources However the concentration of nutrients and pathogens in the greywater from bathroom, laundry, and washing basin is lower than after mixing with kitchen flow because these sources do not contain food, and meat (Eriksson et al., 2002)

Table 2.3 Quality of greywater from household devices and appliances

Source: Gross et al., 2015

In addition, the microorganisms numbers in bathroom and laundry greywater are lower than in other streams (Fanggyue et al., 2009)

2.1.3 Characterisation of greywater usability

The characteristics of domestic greywater depend on many factors as user lifestyle, living standards, the number and age of residents, culture, type of chemicals used, quality of tap water, etc Greywater generated from bath and wash basin contains personal care products including soap, shampoo, toothpaste, shower gel, and substances removed from personal cleaning process as hair, shaving waste, lint, dust, skin epidermis trace of urine and faeces and pathogenic microorganisms (Nolde, 1999, Morel and Diener, 2006) Laundry greywater discharged from washing machines contains compositions from powder soap (sodium, phosphorous, surfactants and nitrogen), laundry detergent, dirt,

bleaches, oils, paints, solvents, and non-biodegradable fibres from clothing (Morel and Diener, 2006)

Raw greywater may cause odour from household chemicals as detergent or other production Moreover, the bad smells release from decomposition processes

of organic matter in anaerobic processes when stored in the tank (Gross et al., 2015) In addition, total suspended solids (TSS) and turbidity in the greywater should be considered and treated because they affect to the disinfection and aesthetic TSS in greywater is lower than in domestic wastewater Its concentration always fluctuates during day because depended on household activity TSS in greywater contains hair, soil, dust, skin from person, fibre (Eriksson et al., 2002) (Birks and Hills, 2007) (Gross et al., 2015) According to Jefferson, the solid size in the greywater ranges from 10–100m in which greywater generates from bathroom, shower, and hand basin are 29.6±2.7, 33.2±4.9, and 27.1±0.1m, respectively (Jefferson et al., 2004) Besides, the suspended solids depend on dirt and dust from clothes and zeolite used in the detergents, the suspended solids concentration from laundry greywater ranged 170-330 mg.dm3 (Eriksson et al., 2002)

Especially cations Na+, K+, salt, at high concentrations are harmful to soil and plants The salinity of greywater depends the composition of sodium, nitrogen, phosphorus-based soap existed in powder detergents and washing powders (Morel and Diener, 2006) The salinity in the greywater is showed by electrical conductivity (EC) indicators which depend on originating source A high EC level originated from washing machines 2457 S/cm (Friedler, 2004), laundry 190-1400

S/cm (Christova-Boal et al., 1996), which was higher than in bathroom 82-250

S/cm (Christova-Boal et al 1996) and showers 1565 S/cm (Friedler, 2004) Growth of plants and biological treatment processes depend also on pH The pH

of greywater depend on the products are used in the household The pH value of greywater originating from laundries was 9.3-10 (Christova-Boal et al., 1996), 8-10 (Eriksson et al., 2009) and 7.5 (Friedler, 2004) 

Greywater contains typically a low level of nutrients (nitrogen and phosphorus) The nutrient compositions in greywater compare to domestic wastewater are 9-14%, 20-32%, 18-22%, and 29-62% of N, P, K, and organic

matter, respectively (Kujawa-Roeleveld and Zeeman, 2006) The nitrogen in the greywater equals a tenth in the household sewage (Gross et al., 2015) The significant source of nitrogen in greywater is urine which is contributed by pass urine in the bathroom The phosphorus in the greywater originates from washing powders, detergents (Jefferson et al., 2004) However, addition of phosphates to detergent has been forbidden in many countries in Europe in recent years (Gross

et al., 2015)

2.2 Greywater treatment

The presence of organic matter, surfactant, pathogen, and other compounds in the greywater has a potential effect on air, soil and plants (Dalahmeh et al., 2011) Hence, greywater should be treated to meet reuse‘s requirements However, depending on the specific purpose of reuse, a proper treatment method should be chosen to achieve economic and environmental efficiency

One of the most popular and efficient methods in water and wastewater treatment is sand filtration (Dalahmeh et al., 2012) The advantages of it are low cost, efficiency and simple technique Moreover, the sand filtration is operated as

a passive process without stringent control (Hendricks, 2011) Indeed, a system was designed by one rack with 6 perforated drawers of sand filter achieved efficiency removal for 69–98%, 76-95%, 78-98% of TSS, COD, BOD5, respectively Treated greywater of this study was to meet irrigation requirement standards for restricted irrigation area in Jordan (Assayed et al., 2015) The efficiency of sand filter depends on some factors as hydraulic conductivity and hydraulic gradient According to the study by Santos et al., (2012), treatment efficiency greywater from washing basin increased when decreasing size of filter material Indeed, TSS, COD, BOD5 decreased from 34 mg.dm-3, 88 mg.dm-3, 20

mg.dm-3 to 15 mg.dm-3, 46 mg.dm-3, 22 mg.dm-3 when size of filter material decreased from 0.13 mm to 0.025 mm, respectively (Santos et al., 2012)

In addition to traditional sand filtration methods, greywater can be treated

by membrane filters, filter material capable to adsorb pollutants and combined methods to improve processing efficiency The low strength greywater may achieve high treatment efficiency with ultrafiltration, nanofiltration membrane

According to Malarski (2014), efficiency removal of COD and turbidity fluctuated from 45–70% and 92-97%, respectively when applying ultrafiltration membrane Nanofiltration membrane has higher removal efficiency, e.g 90% of the soluble organic matter and 50% of ionic species were removed (Malarski, 2014) However, investment and maintenance costs for membrane filter have to be considered when applying for reuse of greywater

To achieve high economic efficiency for greywater reuse, treatment methods must be chosen not only based on the composition and characteristics but also on the object receiving water reuse Appropriate alternatives for greywater treatment and reuse were summarized by Li et al (2009) as shown in figure 2.1

Low strength greywater

Medium and high trength

greywater

Sedimentation, screening

Biological treatment (aerobic: RBC, SBR, )

Sand filtration

Membrane filtration

Membrane bioreactor (MBR)

Restricted potable reuses

non-Disinfection (UV, chlorine)

Unrestricted non-potable urban reuses

Figure 2.1 Choosing methods for greywater treatment to reuse (Li et al., 2009)

2.3 Greywater reuse for irrigation

2.3.1 Standards and guidelines

Greywater reuse has been applied long-time in the past and is strongly developing in recent years not only in high-income countries such as USA, Australia, UK, Sweden or Germany but also in many low-to-middle income

countries such as Malaysia, Jordan, Srilanka, Vietnam (Gross et al., 2015, Morel and Diener, 2006) However, many standards and quantitative guidance to greywater reuse for irrigation are still not popular and specific According to Kordana (2014), a few regulations and guidelines on treatment of greywater for reuse exist which are mostly established by local authorities and mainly concerning health and environmental impacts

Currently, some standards and guidelines have been established to safe reuse of treated wastewater over the world However, scarce standards have been published for greywater reuse Before, some countries as some USA states (Arizona, New Mexico, New Jersey, California), Australia (Queensland, New South Wales), China (Beijing, Tianjin) have issued greywater-specific regulations (Morel and Diener, 2006) The World Health Organization (WHO) in 2006 has published guidelines for greywater reuse for restricted and non-restricted agricultural irrigation, however only microbiological parameters are regulated in this guideline Besides, some standards/ regulations consider also some physical and chemical parameters

Almost important indicators associated with greywater reuse like COD, BOD, turbidity (aesthetic), total Coliforms, Fecal Coliform (hygienic) and suspended solids were issued in these standards However, the quality levels were different such as the water quality requirements for irrigation by Jordanian standards are much lower than by the US Environment Protect Agency (USEPA) (Boyjoo et al., 2013) A short review of regulations/ guidelines on greywater reuse for irrigation is shown in table 2.4

Table 2.4 Some regulations/guidelines of water reuse for irrigation

Type of reuse Physico-chemical criteria Microbial criteria

pH=6–9,

FC=no detectable US-EPA (2004)

Restricted access area

dm-3, Cl 2 =1 mg.dm-3 residual (minimum)

FC≤200 US-EPA (2004)

Discharge into in land

surface water

SS<100 mg.dm-3, pH=5.5 to 9.0, Oil and grease<10 mg.dm-3, ammonical nitrogen (as N)<50 mg.dm-3, BOD<30 mg.dm-3, COD<250 mg.dm-3, As<0.2 mg.dm-3

Ghaitidak and Yadak (2013)

Discharge into land for

irrigation

SS<200 mg.dm-3, pH=5.5 to 9.0, Oil and grease<10 mg.dm-3, BOD<30 mg.dm-3, As<0.2 mg.dm-3,

Ghaitidak, Yadak (2013)

Restricted irrigation Helminth

.

dm-3

Thermotolerant coliforms <10

Australian Capital Territory (2007)

dm-3

FC≤1000 TC≤10000 Li et al (2009) Urban reuses and

dm-3, Residual chlorine≤1 mg

dm-3

FC≤1000 TC≤10000

Fecal coliform (FC): 25 CFU/100ml (low standard);

FC: not detection (high standard)

BSI: Greywater systems BS 8525- 1&2:2010 2010

2.3.2 Potential of greywater reuse for irrigation

General considerations on quantity and quality of greywater show that it has been useful for irrigation Indeed, the quantity of greywater from a household ensures enough irrigation for the lawn and garden area In a study conducted by Edwin (2014) in urban residential in India, it was shown that the average water consumption for gardening irrigation was 2.5 ± 0.6 dm3.p-1.day-1 (Edwin et al., 2014).Specifically, amount of irrigated water for lawns or landscape in the garden depends on many factors as the type of plants, area, type of soil, geographic location, and weather According to a study in Portugal by Matos et al (2012), the houses that had garden areas or lawn of average area 40 m2 accounted for 30%

of the total 64% of homes taken into account And the quantity of greywater from a typical household would ensure to supply 11.5 mm irrigation water/day for an area

20 m2 during months of the dry season

The amount of irrigation water for plant requirements is calculated using equation in the form:

For example, many studies (Fu et al., 2004, Xinmin et al., 2007, Demirel et al., 2013, Bastug et al., 2003) have shown that the total seasonal irrigation water requirements of lawn were 244 – 1085 mm season-1

(about 26 weeks) While the total volume of greywater production was 71±17.03 dm3.p-1.day-1 (59±14.15 dm3.p-1.

day-1 when not including kitchen and dishwashing), and 98.4±11 dm3.p-1.day-1(68±10.4 dm3.p-1.day-1 when not including kitchen and dishwashing) were reported

by Edwin (2014) and Noutsopoulos (2017), respectively Consequently, the

greywater production (not including kitchen and dishwashing) from a person can suffice to meet irrigation water requirements for an area of lawn from 10–55 m2

In addition, it allows saving around 34% of the household water budget for 6 months

a year in houses with highly seasonal irrigated in the gardens in Melbourne (Christova-Boal et al., 1996)

Although greywater contains many pollutants having potential risk for soil, plants, and human such as pH, salt, SAR, organic matter, nutrient, detergent, heavy metal or pathogens, it also has the potential to be reused for irrigation because the concentration of contaminants is not severe

As table 2.3, the greywater from bathroom, washing basin, and laundry sources has high organic matter concentration (COD: 230-339 mg.dm-3; BOD5: 44–426 mg.dm-3) however the organics from these sources are decomposed faster than those of black water, especially in the root zone of plants where the irrigated greywater is assimilated and further biodegraded (Oron et al 2014) The organic matter is considered to be good for soil as it improves soil structure and moisture, helps the soil to activate better (WHO, 2006) Physical and chemical characteristics of greywater without kitchen sink are the same as of diluted wastewater, which becomes a source of appropriate household reuse options (Mohamed, 2011)

Greywater reuse for irrigation with excessive concentration of salt can have negative impacts on soil, plants, groundwater and surface water The TDS, EC in the soil increase when salt is accumulated in soil It can affect microbiological activity and fertility The characteristic effect of these factors relates to the sodium adsorption ratio (SAR) SAR in the soil will change because of receiving sodium cation (Na+) from greywater (Elgallal et al., 2016) Sodium has relatively high concentration level in the greywater because it is common in domestic use (especially from the dishwasher) (Gross et al., 2015) SAR is the ratio between sodium ion concentration and magnesium with calcium ions in the form:

In which: , , and are the cation concentrations of sodium, calcium, magnesium, respectively, in (mmol.dm-3)

When SAR value is too high it deteriorates soil structure, decreases the hydraulic conductivity of soil and reduces yield and growth of plants The value of SAR recommended for irrigation is less than 5 (Gross et al., 2015), and according

to Decree-law No 236/98 (Portugal), this value is 8 (Matos et al., 2012) According

to Gross (2015), many studies have been cited with the largest SAR of greywater about 6 (Gross et al., 2015)

In addition, boron is a metal in the ingredient of detergent which has potential risk for soil and plant at a high concentration level, however, it is also an essential element to plant growth It is sensitive with slightly higher than benefit level its can pose injury or death to plants Following Guidelines for water reuse (2012), the concentration of boron for optimum yields is about a few –tenths

mg.dm-3, it becomes toxic for the plant at 1 mg.dm-3 but most grasses can withstand at 2 – 10 mg.dm-3 (US-EPA, 2012) Besides, greywater also contains some trace elements and heavy metals, however, they often exist in the trace form and do not require treatment for nonpotable reuse (Edwin et al., 2014)

The nutrients such as nitrogen and phosphorus, potassium are present in greywater at relatively low concentrations Nitrogen is a nutrient source for plant

up take, however excess of nitrogen for plants leads to potential risk because of leaching to groundwater (US-EPA, 2012) Besides, phosphorus and potassium at low concentration in the greywater have no harmful impacts on the environment and harmful plants (WHO, 2006)

The detergent surfactant that exists in greywater is capable of accumulating

in the soil which can change some the physical properties of the soil (Maimon et al., 2017) The detergent is a salient feature in greywater, however its presence is not a severe problem because it is biodegraded quickly (less than an hour) and do not pose potential risk on plants (AL-Mashaqbeh et al., 2012; Oron et al., 2014)

In addition, greywater reuse to irrigate the garden is not only saving water but also money (Christova-Boal et al., 1996)

2.3.3 Storage and diversion of greywater for reuse

Storage of water is a basic task for irrigation However, the raw greywater storage for irrigation encountered many problems Although, it can reduce suspended solids and turbidity, raw greywater is not suitable for storage in tank for

more than 48 hours because organic matters in greywater are decomposed in anaerobic conditions, releasing the odours, creating aesthetic problems, and breeding ground for numerous pathogenic bacteria (Pinto and Maheshwari, 2015) Following Australian Capital Territory (2007), greywater contained a high concentration of organic matter which must not be stored for more than 1 day as creating odours because of the growth of micro-organisms However, treated greywater can be stored for more than one day to irrigate when applying subsurface (underground level 100–300 mm); or soil-surface irrigation (underground level >300 mm) with treated greywater quality up to 20 mg.dm-3 of BOD5 and 30 mg.dm-3 of SS Covered surface drip, surface irrigation with treated and disinfected greywater is applied to quality of 20 mg.dm-3 of BOD5, 30 mg.dm-3

of SS and 10 CFU thermo-tolerant Coliforms per .100.cm-3 (Australian Capital Territory, 2007)

Various types of irrigation are usually applied, including surface irrigation, sprinkler irrigation, drip irrigation in which surface irrigation is one of the most common forms of irrigation throughout the world The irrigation water of surface irrigation method is distributed over the soil surface by gravity, while sprinkler irrigation distributes the water by a system-connecting pump with pipes With the drip irrigation, the water is supplied onto the soil close to plants at very low rates (2

- 20 dm3.hour-1) by many small holes on the pipe More specifically, the irrigation for plants/ lawn in the garden is usually realized using normal sprinkler, subsurface, on the surface, flood, or hosing methods (Gross et al., 2015) Each method has its advantage and disadvantage Basing on type of soils, weather, category of plant one can choose the proper method To avoid human contact with greywater for garden lawn watering, the irrigation method that restricts exposure to air is safer (Rodda et al., 2010) Sprinkler or spray methods are not recommended for applying greywater for garden lawn watering because many aerosols contain bacteria and virus easily exposing on the environment (WHO, 2006) Furthermore, time interval between consecutive irrigations and dose for irrigation is important factors which can affect plants and groundwater level The drip distribution system

is effective in the treatment and distribution of greywater even under condition of cold weather if it is designed and installed properly (Bohre and Converse, 2001)

2.3.4 Impacts of greywater reuse for irrigation

2.3.4.1 Human health

A lot of studies have shown that the greywater can be used for irrigation of plants or lawn in the garden or expanding outside garden However, it poses some risks for human health because some types of irrigation can make pathogens in greywater to disperse into the environment

Greywater reuse has acknowledged potential benefits for irrigation, however, greywater may contain pathogens which can harmfully impact on environmental health if methods are unreasonable According to Hawaii State Department of Health (2009), greywater contains many contaminants which can

be harmful to human health For example, bacteria can exist and develop inside supply and storage system of greywater Hence, greywater reuse for lawn in the garden, golf yard should minimize direct contact The method of subsurface drip irrigation was recommended in some states of USA (Oron et al., 2014) Furthermore, irrigation of greywater needs a monitor to avoid leading to runoff, mosquito breeding, affect groundwater, and plants by ponding (Hawaii State Department of Health, 2009)

A reported study of Maimon (2014) has shown that kitchen effluent was one

of the main factors which created a high pollution level in greywater and potential risk when its reuse Furthermore, the study suggested that greywater should be disinfected, or methods of limited contact with air, such as drip irrigation, wearing gloves when maintenance to reduce risk for human health must be applied (Maimon et al., 2014) Since greywater reuse is limited it is wise to exclude kitchen flow to reduce many risks

2.3.4.2 Soil

The planted soil can be deteriorated when the irrigated water has a high concentration level of boron (B) and surfactants, which are common in detergents for washing machines, in long–term (Gross et al., 2015) To reduce risk for soil in greywater reuse one can apply a friendly production with in environment or dilution with freshwater for irrigation reuse (Mcilwaine and Redwoood, 2010) The high concentration of surfactants may reduce hydraulic conductivity, however, it depends on the structure of soil, surfactant characteristics and their concentration

(Abu-Zreig et al., 2003) Furthermore, the capillary force in soil decreases when increasing surfactant concentration because of reduction of water surface tension (Wiel-Shafran et al., 2006)

Moreover, pH, EC, salinity, sodium adsorption ratio (SAR), and organic content of soil were significantly increasing during long-term raw greywater reuse because of detergent components in the greywater (Sawadogo et al., 2014), (Al-Hamaiedeh and Bino 2010) However, Alfiya et al (2012) conducted a study on ryegrass with three categories of irrigation water as freshwater, light greywater (from shower and washbasin), and treated greywater The results of the study showed that the soil characteristics and plant (ryegrass) were not impacted harmfully, and there were not significant differences between applying separately the three categories of irrigation water Furthermore, the study concluded that ryegrass did not detect any signs of disease of phytotoxicity when irrigated with light greywater However, the study found that the surfactant accumulated in the soil planted, caused the soil to become hydrophobic (Alfiya et al., 2012) Indeed, when surfactant-rich greywater (range from 0.7 – 70 mg.

dm-3) was irrigated, it increased water repellency of soils, and affected the flow and productivity of soils because of surfactant accumulation (Wiel-Shafran et al., 2006) However, (Negahban-azar et al., 2012) also concluded that the surfactants and salts from greywater accumulated in the top soil layer 0-15 cm and is not harmful to plant growth

The study Reichman and Wightwick (2013) has shown that irrigation with greywater containing a detergent marketed as ―minimal environmental impact‖ laundry detergent or greywater from standard (conventional) laundry detergent affected the soil by increasing pH soil, salt build in the soil, enzyme activity, and worm avoidance, however, greywater from low environmental impact laundry detergent was safer for soil and plant than from standard laundry detergent Furthermore, the pH, EC, SAR of soil planted with tomatoes and green bean and irrigated with raw greywater were higher than that irrigated with greywater which was treated by volcanic tuff filter (Al-Zou et al., 2017)

Similarly, Pinto, Maheshwari (2010) have conducted a study on silver beet

(Betavulgaris.) with four irrigation regimes including tap water, raw greywater,

mixed raw greywater with tap water (1:1 ratio), and irrigating alternately with tap

water and raw greywater next time The result of the study showed values close to those given in other studies with increasing EC, pH of soil when irrigated with raw greywater, but the irrigating alternately with tap water and raw greywater next time resulted in that the change EC and pH was the same as by irrigation water with tap water This mean has a potential to reduce impact on soil depending on the quality of greywater and regime of irrigation As suggested by (Al-Hamaiedeh and Bino, 2010) that is leaching of soil with freshwater which maintains soil suitable for growing plants when applying greywater reuse

Indeed, greywater reuse has both negative and positive impact on planted soil (Reichman and Wightwick, 2013, Rodda et al., 2011, Travis et al., 2010, Pinto and Maheshwari, 2010) The nutrients in greywater may increase yield of plants, however long term irrigation with high phosphorus concentration easily generate disease because accumulated in soil it is becoming toxic to plants (Siggins et al.,

2016, Stevens et al., 2011)

2.3.4.3 Groundwater

The potential risk for groundwater is an inevitable consequence because the leaching salts, pathogens, and nutrients from the root-zone can penetrate the groundwater when the soil was irrigated with greywater The potential risks of groundwater quality depend on soil structure, type of soil, contaminant constituents in the greywater, and dose of irrigation water Moreover, it depends

on the depth of the groundwater table level which is affected the time delay after dosing of irrigation water or rainfall in the area

Particularly, nitrate (NO3-) is a pollutant which is always interested in the quality of groundwater Nitrate in the wastewater or greywater has possible impact

on groundwater quality when an excess amount is applied for soil Indeed, the results of study by Lazarova and Akica (2005) reported that the concentration of nitrate in groundwater in the area with irrigation using wastewater was higher than with freshwater irrigation Potential leaching nitrate from irrigation greywater to groundwater was low in case of excluded greywater from kitchen, and urine from toilet because the total nitrogen concentration in greywater was not high as it ranged from 0.6 to 21 mg.dm-3 (Eriksson et al., 2002) Also leaching salt, boron

and other contaminants to groundwater is associated with the quality and method

of wastewater reuse for irrigation (Lazarova and Akica, 2005)

2.3.4.4 Yields

Some studies have shown decreasing biomass yield or disease by irrigation with greywater, while other studies showed that biomass yield (statistically significant at 95% confidence interval) was not significantly different or health of plant applying irrigation greywater compared to irrigation with treated greywater or freshwater The causes of different results obtained by (Maimon and Gross, 2018) were due to differences in the composition, characteristics and origin of greywater, soil characteristics, and the type of crops were observed More specific, salinity, high pH, surfactants, and others are causing negative effects on plants while nutrients and organic matters stimulate growth (Gross et al., 2015)

Decreasing biomass yield was demonstrated in the study by Reichman

(2013) where in the lettuces (Letuca sativa) were irrigated with the standard

greywater from laundry what resulted in the lowest biomass compared to tap water, or nutrient solution, or greywater from low environmental impact laundry detergent Moreover, lettuces were irrigated with raw greywater which had negatively impacted on plant growth, and increase in content of Cu, Fe in plants (Reichman and Wightwick 2013) Besides, chlorosis appears on lettuce plant irrigated with raw greywater because of the elevated salinity and boron levels in the leaves (Gross et al., 2015)

In contrast, Alfiya (2012) conducted a study on ryegrass (Lolium perenne)

with three different types of irrigation water including tap water, raw light greywater, treated greywater (effluent from rotating biological contactor) The results have shown that raw light greywater did not have detrimental effects on plants The biomass yield was not significantly different (confidence interval 95%) between ryegrass irrigated with tap water and with raw light greywater However, biomass yield and the growth rate by irrigation with treated greywater from rotating biological contactor was higher than the above mentioned (Alfiya et al., 2012)

Similarly, another study on the silver beet (Betavulgaris.) showed that the biomass

yields were not significantly different (p ≥ 0.05) when having different four categories of irrigation water (tap water, raw greywater, mixed tap water with raw

greywater at 1: 1 ratio), and irrigating alternately with tap water and greywater next time (Pinto and Maheshwari, 2010)

Meanwhile, Al-Zou et al (2017) concluded that different effects on type of crops were irrigated by raw greywater, treated greywater (outlet of volcanic tuff

filter), or tap water Al-Zou et al (2017) conducted study on tomato (Lycopersicon

esculentum) and green bean (Phaseolus vulgaris) showed that no statistically

significant differences (p ≥ 0.05) were observed when irrigated water were tap water, raw greywater, or treated greywater concerning number of fruit per pot, weight of fruit, circumference of fruit, number of leaves, plant height, and biological yield of tomato Similarly, number of beans, number of leaves, and number of branches of green bean was not statistically significantly different (p ≥ 0.05), however the significant differences (p ≤ 0.05) were shown on fruit weight, circumference, and biological weight of green beans

2.4 Economics of greywater reuse

Successful greywater reuse depends on many factors as technology, policy, public acceptance, econonic profit in which economic and technical harmonization plays the crucial role Greywater reuse for irrigation is charged by some money invested to greywater treatment system which can cost from 4,000 to 20,000 USD

A technical and economic analysis is carried out by calculation of the total annual expected costs, according to the formula (Gross et al., 2015):

in which: – investment expenses; - annual annuity instalment calculated as: