Development of a novel urban rural relationship for sustainable nitrogen cycle casestudy in hai phong city

According to SDG 6 Ensure availability and sustainable management of water and sanitation for all, The Ministry of construction mentioned that Vietnam currently has 37 concentrated WWTPs

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

NGUYEN THU HOAI

DEVELOPMENT OF A NOVEL URBAN-RURAL RELATIONSHIP FOR SUSTAINABLE NITROGEN CYCLE: CASE-STUDY IN HAI PHONG CITY

MASTER’S THESIS

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

NGUYEN THU HOAI

DEVELOPMENT OF A NOVEL URBAN-RURAL RELATIONSHIP FOR SUSTAINABLE NITROGEN CYCLE: CASE-STUDY IN HAI PHONG CITY

MAJOR: ENVIRONMENTAL ENGINEERING

My gratitude is extended to all my teachers in the Master’s Programme in Environmental Engineering, Vietnam Japan University for their enlightening lectures and instructions in many fields of Environment and Sustainability Science I would like to thank all of the staffs working in VJU for their wonderful assistant during my study and their support for field exercises Under VJU sponsorship, I would able to learn from the field and to exchange knowledge with other scholars working for the sake of sustainable development My thank is extended to all the friends in VJU, we have been working hard for our own project but also working as a team in each subjects and field exercises, and we enjoy the good times as well as overcome hardships

Last but not least, I would like to thank my family for their encouragement and trust Their constant love and caring enable me to complete this research

TABLE OF CONTENTS

TABLE OF CONTENTS 1

LIST OF TABLES 6

LIST OF FIGURES 8

LIST OF ABBREVIATIONS 10

INTRODUCTION 11

1.1 Background 11

1.1.1 Problem statement 11

1.1.2 Wastewater management in Vietnam 12

1.1.3 Organic fertilizers in Vietnam 14

1.2 Research objective 18

1.3 Scope of study 18

1.4 Thesis structure 18

CHAPTER 1 LITERATURE REVIEW 20

1.1 Nitrogen in the environment 20

1.1.1 The essential of Nitrogen and its cycle 20

1.1.2 Sources of nitrogen 22

1.2 Waste sludge and its recovery and reuse 30

1.2.1 Definition and classification of sludge 30

1.2.2 Characteristics 32

1.2.3 Impacts of sludge to environment and human health 34

1.2.4 Technical of reusing sludge 37

1.3 Nitrogen in Hai Phong city 40

CHAPTER 2 MATERIAL AND METHODS 43

2.1 Hai Phong city 43

2.1.1 Natural and Socio-Economic features 43

2.1.2 Social-economic features 44

2.2 Methodologies 44

2.2.1 Data collection method 44

2.2.2 Feasibility assessment 47

CHAPTER 3 ESTIMATION OF THE PRODUCTION AND CONSUMPTION OF NITROGEN 49

3.1 The production of nitrogen 49

3.1.1 Septage sludge 49

3.1.2 Animal manure 51

3.1.3 Aquaculture 53

3.1.4 Industry 54

3.1.5 Total loading of nitrogen in sludge 56

3.2 The consumption of Nitrogen through fertilizer 57

3.2.1 The nitrogen fertilizer consumption 58

3.3 Nitrogen consumption and production 58

CHAPTER 4 ASSESSMENT OF CITIZENS AND FARMERS FOR

WASTE-BASED FERTILIZER 60

4.1 Urban area 60

4.1.1 Drainage system 62

4.1.2 Septage management 63

4.1.3 Assessment of citizens for three type of fertilizer 66

4.2 Rural area 69

4.2.1 Paddy farm 70

4.2.2 Animal farm 72

4.2.3 Aquaculture 72

4.2.4 Assessment of farmers for three type of fertilizer 73

CHAPTER 5 SUSTAINABLE AND INTEGRATED WASTE-BASED NITROGEN MANAGEMENT IN HAI PHONG CITY 76

5.1 Sustainable and integrated waste-based nitrogen management 76

5.1.1 Scenario 1 (Baseline scenario) 76

5.1.2 Scenario 2 (Government contribution) 78

5.1.3 Scenario 3 (Public Private Partnership) 79

5.2 Feasibility assessment 80

5.2.1 Financial analysis 80

5.2.2 Feasibility assessment 83

CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS 91

6.1 Research significance 91

6.2 Recommendations 92

REFERENCES 94

APPENDIX 101

LIST OF TABLES

Table 1-1 The production and consumption of nitrogen in fertilizer around the world

from 2016 to 2022 (thousand tons) [20] 24

Table 1-2 The concentration of nitrogen in precipitation across United Kingdom from 2000 to 2002 27

Table 1-3 Waste management and treated in selected cities [32] 28

Table 1-4 Selected technologies for resources recovery in waste sludge [49] 37

Table 2-1 General information of Hai Phong city 43

Table 2-2 General information of surveyors living in urban area of Hai Phong 45

Table 2-3 General information of surveyors in Ang Duong hamlet 46

Table 2-4 Agriculture land and total number of selected animal in Hai Phong city [4] 46

Table 2-5 Agriculture land and total number of selected animal in Ang Duong hamlet 47

Table 3-1 The total nitrogen generated from human excreta in Hai Phong city and Ang Duong hamlet 51

Table 3-2 Daily manure production and characteristics (per head per day) [56] 51

Table 3-3 The loading of nitrogen generated by animal manure in Hai Phong city and Ang Duong Hamlet 52

Table 3-4 The total number of animal farms in Ang Duong hamlet 52

Table 3-5 The loading of nitrogen generated in aquaculture in Hai Phong city and Ang Duong Hamlet 54

Table 3-6 List of industrial parks and its wastewater facility [59] 55

Table 3-7 Total loading of Nitrogen from different sources of excreta in Hai Phong

city and Ang Duong Hamlet 56

Table 3-8 The fertilizer consumption and the percentage of nitrogen fertilizer [60], [61] 57

Table 3-9 The total fertilizer consumption and nitrogen fertilizer consumption in Hai Phong city 58

Table 3-10 The nitrogen in fertilizer consumption and nitrogen in waste sludge of Hai Phong city and Ang Duong hamlet 59

Table 4-1 Emptying septage sludge activity of SADCO (unit:m3) 61

Table 4-2 The number of survey questionnaires by districts 61

Table 4-3 Occupation percentage of the interviewer 61

Table 4-4 The number of farmers in Ang Duong hamlet 69

Table 4-5 The amount of fertilizer which farmers use in different types 70

Table 5-1 Inflow-out flow financial of three scenarios 80

Table 5-2 Financial analysis of three scenarios (VND/year) 82

Table 5-3 Feasibility assessment of 3 scenarios 83

Table 5-4 Summary the feasibility assessment for three scenarios 89

LIST OF FIGURES

Figure 1-1 Sources of Nitrogen 22

Figure 1-2 The meat production by meat type (2028 vs 2016-18) 25

Figure 1-3 The process of manure-N production [28] 26

Figure 1-4 Nitrogen cycle in Hai Phong city 41

Figure 2-1 Administrative map of Hai Phong 43

Figure 2-2 Location of households surveyed in urban area of Hai Phong 45

Figure 3-1 Percentage of different type of factories in the industrial parks of Hai Phong 55

Figure 3-2 Fertilizer consumption and the percentage of nitrogen in fertilizer in Vietnam [60], [61] 57

Figure 4-1 Process Flow diagram of sludge treatment in Trang Cat plant 60

Figure 4-2 Response of citizens in the on-site and off-site drainage system 62

Figure 4-3 The connection of indoor and outdoor drainage system 62

Figure 4-4 Assessment of citizens for the emptying septic tank activity 64

Figure 4-5 Unit in charge in emptying septic tank activity 64

Figure 4-6 The emptying septic tank cost 65

Figure 4-7 Location discharging septage sludge 65

Figure 4-8 Trang Cat sludge treatment plant 66

Figure 4-9 The assessment for chemical and organic fertilizers by citizens 67

Figure 4-10 The assessment of citizens for waste-based fertilizers 68

Figure 4-11 Fertilizer cost per year 71

Figure 4-12 Fertilizer distribution places 71

Figure 4-13 Paddy field in Ang Duong hamlet 72

Figure 4-14 The assessment for chemical and organic fertilizers by farmers 73

Figure 4-15 The assessment of farmer for waste-based fertilizers 74

Figure 5-1 Four main step of waste treatment and disposal 76

Figure 5-2 Scenario 1 (Baseline scenario) 77

Figure 5-3 Scenario 2 (Government contribution) 78

Figure 5-4 Scenario 3 (Public Private Partnership) 79

LIST OF ABBREVIATIONS

SDG Sustainable development goals

WWTP Wastewater treatment plant

MARD Ministry of Agriculture and Rural Development RRR Resources recovery and reuse

PPP Public private partnership

FAO Food and Agriculture Organization

IRR Internal rate of return

GLOBAL GAP Global Good Agricultural Practice

A loose and inconsistent structure of Vietnam’s management system can be one of the reasons when 90% of fertilizer products used in Vietnam are chemical products, and farmers in Vietnam mostly overuse the fertilizer amount The sustainable development goals 2 (SDG 2) for the End hunger, ensure food security, improve nutrition and promote sustainable agriculture development has implemented many Decisions and projects towards sustainable agriculture, though very few results recorded at this time The trendy production in the world and in Vietnam is organic products in which organic fertilizers substitute for chemical fertilizers Nowadays, Vietnam has many projects and models of production and use of organic fertilizers in crops but they are small and prone to failure Nutrient resources management has not paid much attention in Vietnam, and the concept of resource recovery and reuse has been currently unpopular

In the other hand, there are many sources that can exceed nutrient like nitrogen in our environment such as human waste, animal manure, industry waste while most of these sources in Vietnam are having discharged into the environment without the treatment According to SDG 6 (Ensure availability and sustainable management of water and sanitation for all), The Ministry of construction mentioned that Vietnam currently has

37 concentrated WWTPs in urban areas with a total capacity of about 890,000m³/day,

it is estimated that around 80% of the generated wastewater discharged directly into

the water bodies without any collection and treatment or partially treated by simple on-site treatment facilities such as septic tanks, and moreover most of sludge generated from wastewater have not paid much attention The management of sludge has only been noticed in recent years, and it has been mentioned with wastewater management in Vietnam's legal system In waste sludge, nitrogen exists mostly in the form of organic nitrogen, which can be recovered and reused for organic fertilizer However, the recovery and reuse of sludge in Vietnam have just stopped at the research step and has not been put into actual operation Most studies only focus on analyzing the properties, characteristics of sludge, and the ability of waste-based fertilizer in the laboratory Therefore, it is certain that research for sludge waste management with the purpose of waste-based fertilizer production is necessary

1.1.2 Wastewater management in Vietnam

1.1.2.1 Wastewater management in urban areas of Vietnam

In major cities in Vietnam, most of the drainage network has been built centuries ago and is now degraded Most of the wastewater system in Vietnam is a centralized system, collecting both wastewater and rainwater, only a few new urban areas have the separated drainage systems

Major cities such as Hanoi, Quang Ninh, Da Nang have drainage network and wastewater treatment system in the city area However, there is still a complete construction of a WWTP but no drainage network has been built yet Therefore, some WWTPs (WWTPs) do not operate at full capacity because there is not enough input wastewater [1] According to the report, by 2018, Vietnam has about 37 centralized WWTPs with a total design capacity of 890,000 m3/day It is expected that by 2020 there will be more 50 WWTPs with a total capacity of about 2 million m3/day and operation, and the rate of collected and treated wastewater will increase to about 20% Although the number of urban WWTPs have increased over the years, however, this number is still very small compared to the actual requirements to be treated Wastewater collection and treatment services are still quite low compared to water

supply systems, so in many places, wastewater and rainwater are still discharged directly into rivers and lakes [2]

1.1.2.2 Wastewater management in rural areas of Vietnam

According to Center for Rural Water Supply and Sanitation (CERWASS), only 50%

of households have typical latrines when compared to the national target of 60% of rural areas, and only 25% of households are able to equipped with standard meeting facilities [3]

The infrastructures in remote areas are mostly funded by the Ministry of Agriculture and Rural Development (MARD) in decentralized level under the responsibilities of provincial or commune People’s Committee [2] The sanitation coverage in rural areas is still low because the main focus now is on the provision of drinking water According to statistics, in the period of 2010-2016, the percentage of households using hygienic toilets increased from 75.7% to 83.3% [4]

The Prime Minister has signed many important policies with many contents related

to SDG 6 such as: National strategy on water resources to 2020, National Environmental Protection Strategy to 2020, vision to 2030, National Program to ensure safe water supply for the period 2016-2025, National Action Plan to improve the effectiveness of management, protection and use of water resources synthesis in the period of 2014-2020, National Target Program built new rural construction in the period 2016-202 With the goal of increasing water use efficiency, in addition to the

Law on Water Resources approved in 2012, the Government approved 04 Decrees

52

Policies and resolutions were issued from the central government and brought to the ministries and departments, from there to be transferred to the departments of the localities In the local areas, appropriate policies will be enforced and brought to the communities The main tasks of communities is monitor and protection water resources; response to water related incidents

Sewage sludge and hazardous sludge are the only two types of sludge currently regulated in Vietnam's Environmental Protection Law In particular, sewage sludge

is identified and managed as solid waste and hazardous sludge is considered as hazardous waste The current standard of sewage sludge management in Vietnam is still in the process of development and drafting, National Technical Regulation Technical Infrastructure Works Sewerage (QCVN 07: 2009 / BTNMT) is the only set

of standards on limits of hazardous sludge wastes in water treatment facilities In addition to the specific regulations on hazardous sludge, the management and treatment of general sludge in the whole country is currently vacant and has not been given adequate attention

1.1.3 Organic fertilizers in Vietnam

According to the Ministry of Agriculture & Rural development, by the end of 2017, the total amount of organic fertilizers being produced, traded and used was 182 products, accounting for 1.3% of total fertilizer products, the remaining 93.7% were inorganic fertilizers and 5% is organic fertilizers [5]

The total capacity of organic fertilizer production facilities is 2.5 million tons/year, accounting for 8.5% of the total domestic fertilizer production capacity (29.5 million tons/year), and equal to nearly 1/10 of the inorganic fertilizer production capacity (26.7 million tons/year) [5]

Fertilizer utilization efficiency is currently very low due to the imbalance of inorganic and organic fertilizers Another issue in using organic fertilizer is that people use traditional organic fertilizers based on their experience, habits and industrial organic fertilizer use according to the principal instructions of the seller and label of product

It is clarified that there is currently no orientation and training for farmers on the effects of organic fertilizers, how to coordinate the balance between inorganic and organic fertilizers Farmers also have very few opportunities to approach and learn about effective balance of organic fertilizer use

During 2015-2017, Vietnam exported organic fertilizer to 34 different countries with

a total volume of approximately 76,000 tons However, the volume of imported organic fertilizer into Vietnam is nearly three times larger than the export (about 220,000 tons) [5] The main reason for this big gap is the domestic under-developed organic fertilizer processing industry The technology and technique of domestic fertilizer production is still slower than other countries, leading to high production costs, making it difficult to compete with foreign fertilizer

1.1.3.1 The production of organic fertilizers

In Vietnam, organic fertilizer is currently produced domestically in two ways: traditional composting and industrial production

The traditional method of composting is mainly used at the farm level based on the source of waste materials or crop residues collected from livestock and cultivated at the household level The organic by-products are mixed well, at the same time can add mineral elements and microbial preparations then compost in the purpose of maintaining the temperature to accelerate the decomposition of organic matter, accelerate the mineralization process and destroy disease-causing organisms for humans, domestic animals and plants

Currently, there are many different annealing methods, such as hot annealing, cold annealing, pre-cooling hot annealing, or advanced annealing methods using EM, quick annealing, etc The time and method of composting affects the composition and

activity of microorganisms that decompose and convert organic matter into humus, thereby affecting the quality and volume of composting compost The centralized and mechanized livestock production in cultivation has led to a small amount of cattle raising in households, which has significantly reduced the amount of organic fertilizer produced by the traditional composting method and instead, the amount of fertilizer Organic industrial production tends to increase in recent years

The mode of industrial production applied at fertilizer production establishments is invested in infrastructure, chains of equipment and machines with different sizes of large and small capacities (from 20,000 to 500,000 tons) Currently, Vietnam has 180 enterprises that have been granted licenses to produce organic fertilizers, accounting for 24.5% of the total production permits granted by the MARD and the Ministry of Industry and Trade (735 License) The total capacity of organic fertilizer production facilities is 2.5 million tons/year, accounting for 8.5% of the total domestic fertilizer production capacity (29.5 million tons/year) and nearly 1/10 of the inorganic fertilizer production capacity (26.7 million tons/year) [5]

1.1.3.2 Legal framework

By the end of 2016, 24 Vietnamese standards (TCVN) were issued related to organic fertilizers, which focused primarily on testing methods to determine the density and activity of microorganisms and content of limiting factors in compost In addition, there are a number of standards that mention the technical requirements for organic fertilizers such as TCVN 7185: 2002 on microbial organic fertilizer

Basically, the standard system of fertilizers in general and organic fertilizers in particular has been developed since the 1990s of the last century until now, but there

is still a shortage of quantity, quality and no response The application is actually required Some biological supplements added to fertilizers, especially foliar fertilizers such as amino acids, vitamins, growth regulators, etc., do not have standards for testing and controlling the quality of fertilizers For microorganisms in microbiological fertilizers/probiotics, only methods for testing groups of

microorganisms such as nitrogen fixation, cellulosolysis, phosphate solubility, the test method for each strain/species of microorganism still have not been available yet The number of standards, especially those related to microorganisms, have not been reviewed, updated or revised to suit the reality and the development of science and technology of production and use of organic fertilizers

The use of useful strains/species of microorganisms to decompose agricultural products and waste in the production of organic fertilizer are becoming an urgent trend nowadays This is one of the important factors contributing to the development

by-of organic fertilizer in particular and organic agricultural production in general State management agencies need to make certain investments in the development of testing methods and techniques to check the quality of organic fertilizers/probiotics using these microorganisms In addition to density testing, attention should also be paid to checking the activity of these microorganisms

The Department of Food Protection, MARD has reviewed and planned the development of test method standards for nutrition, limited and microbiological criteria in faeces Fertilizers, of which special attention is given to groups of organic fertilizers, probiotics, microorganisms, etc The goal is to basically improve standards

on testing methods to check fertilizer quality by 2019

Recently, the development of technical standards for fertilizers in general and organic fertilizers in particular is entirely dependent on the state budget In future, it is necessary to promote the socialization of technical standards to improve efficiency in terms of quality, quantity and progress

No technical standards in the field of fertilizers have been developed at that time Plant Protection Department, Ministry of Agriculture and Rural Development is urgently developing and perfecting technical standards on fertilizer quality, including specific regulations on quality of organic fertilizers and biological products and probiotics products

1.2 Research objective

The research goal is to propose the integrated mechanism of sludge waste management to build a novel urban-rural relationship for sustainable nitrogen cycle The proposed mechanism is expected to recovery and reuse the nitrogen component

in the sludge generated by various sources in the urban and rural area of Hai Phong city

The objective of this study has been three-fold First, to explore the nitrogen cycle in Hai Phong city Second, to determine the potential of nitrogen fertilizer production in waste sludge Finally, to propose the sustainable and integrated waste-based nitrogen management in Hai Phong city

1.3 Scope of study

This study investigates the potential for recovering and reusing nitrogen in various waste sludge sources to produce waste-based fertilizer Sludge management system from source to distribution is mentioned and evaluated in the study Various assessment factors for the three perspectives of Economic-Environment-Social were assessed through the management system to examine the feasibility of implementing the waste-sludge management

1.4 Thesis structure

The remainder of master thesis is structured into six chapters as described below:

- Chapter one highlights the literature review, where the origin of nitrogen in ecosystem, the definition of waste sludge and the sludge recovery systems were introduced

- Chapter two highlights the general information of Hai Phong city and the methodology of the research that explains detail the data collection and analyzing process

- Chapter three highlights the potential of recovery and reuse nitrogen to produce waste-based fertilizer

- Chapter four: The assessment of citizens and farmers in waste-based fertilizer were surveyed and the situation of emptying septage sludge and agriculture activities were determined

- Chapter five: Three Sustainable and integrated waste-based nitrogen management scenarios were examined, as well as the baseline scenario, to verify the potential of recovery and reuse nitrogen from waste sludge The series guideline of resource recovery and reuse (RRR) in developing countries which is reported by the International Water Management Institute were the assessment tools for three scenarios

- Chapter six gives the conclusions and recommendations

- Apart from main chapters, annexes were embedding to give detail information of questionnaire

CHAPTER 1 LITERATURE REVIEW

1.1 Nitrogen in the environment

1.1.1 The essential of Nitrogen and its cycle

Nitrogen has an important role in plant growth and supply [6] It is noticeable that around 80% of Nitrogen is presented as N2 gas which is stable and non-reactive form

in the atmosphere Whereas, the reactive forms of Nitrogen are NH4+, NO3, and NO2

generated from lightning (2%) and biological fixation (98%) are critical for growth and reproduction of all living organisms [6]–[8] In the soils, ammonium (NH4) and nitrate (NO3) will be taken up by plants and transform into plant nutrition by the nitrogen fixation process In natural ecosystems, the most popular process is biological fixation, and a minor degree comes from lightning and biomass burning The nitrogen in atmosphere (N2 gas) will be converted to ammonia (NH3) by bacteria, the nitrogen fixation process takes places in the root systems where bacteria access the atmospheric nitrogen sources Certain plant families, such as legumes, have establish symbiotic relationship with nitrogen fixing bacteria, but the majority of plants use the reactive nitrogen present in soils and it leads to the limitation of growth factor [8] In environment, nitrogen will return back to the soil after organisms dead, and the soil microorganisms will provide again the reactive nitrogen to plants and then to animals and humans Some amount of fixed nitrogen will return to the atmosphere in elemental form [9]

The nitrogen cycle that takes place continuously between atmospheres is the biosphere and the hydrosphere [8], [9] These processes depend on the environmental factors like humidity, oxygen concentration or temperature, on soil properties such

as texture, and clay mineralogy In the natural ecosystems, reactive nitrogen does not accumulate because of the equilibrium and the nitrogen cycle will be closed when these elements return the atmosphere as non-reactive nitrogen gas through the denitrification process [10] Soil organic matter, and particularly the microorganisms

it supports, relates to nutrient sources directly through the provision of nitrogen

compounds and indirectly through the conservation of good soil structure leading to higher soil water storage capacity and stable aggregation to reduce soil erosion Most nitrogen in the soil is not directly available for plant uptake and must be converted into reactive nitrogen (i.e mineralization) [8]

Human activities like the production and consumption of chemical fertilizers, fossil fuels have altered nitrogen cycle and caused the disturbance of the environment [11] Furthermore, the population has increased significantly, resulting in high demand for food which leads to mass-produced synthetic nitrogen fertilizers [9] The fertilizer production activities contribute a part to the nitrogen cycle through the Haber-Bosch process [8]–[10], [12] Erisman et al estimated that nearly 50% of the word population were fed by the Haber-Bosch process in 2008 [12] In 2003, Galloway had calculated that the production of ammonia (170Mt) had grown to exceed the fixation of nitrogen

by microbes [10] However, the industrial fertilizer production causes serious environmental drawbacks like impacting human health, bio-diversity, soil, water and air [7], [13]–[15] In 2002, Smil V et al reported that only 2% of reactive nitrogen accumulated in crop and the rest was lost through air and water pathways [16] In additional, 2% of the reactive nitrogen generated annually transforms to N2O gas affecting to the ozone layer and contributing to the global warming [14], and 12% escapes as NOx and NH3 which affects the atmosphere in many ways [17]

1.1.2 Sources of nitrogen

Figure 1-1 Sources of Nitrogen

The main source of nitrogen is atmosphere where nearly 78% of nitrogen come from

N2 gas [7], the other natural source is geology where organic matter and death microorganisms deposit sediments for many years to form mineral nitrogen such as

NO3 and NO2 [9] Human activities are the biggest contributor of nitrogen and three main sources of excess nitrogen are urban sources, agricultural sources and industrial sources The contribution of sources to nitrogen production is presented in Figure 1-1

1.1.2.1 Environment

a Atmospheric precipitation

It is reported that 99% of molecular form in atmosphere is N2 [6]–[9], and the rest is ammonia as various nitrogen oxides and nitric acid (HNO3) [8] Most of the atmospheric nitrogen compounds are contributed by industrial air pollution, and certain amounts are released in the soil by the organic matter decomposition and in the atmosphere by the photochemical reactions [8], [9]

Recently, N2O, which is one of the main greenhouse gases, has become one of the biggest concerns in the world Recent researches suggested that the production of

N2O mostly comes from the agriculture activities [9], [12]–[16] The emission of N2O can be considered by the agriculture activities, synthetic nitrogen fertilizer, and the animal production system In the atmosphere, nitrogen release back to the environment mostly through the mechanisms of volatilization, runoff and leaching [9], [10]

b Geological source

The plateau of Tarapacá, Atacama Desert, Chile where that has the sediments of nitrate of soda is a example of the geological sources The nitrate has deposited in Chile since the ancient times Atacama Desert has been known as the driest places on the Earth [9], [18], Ghaly AE et al stated that the soluble nitrate in water was deposited in caliche layers which is a sedimentary rock containing sodium nitrate layers [9] The other geological sources of nitrogen include metamorphic rocks, igneous rocks, and coal Most of them are nitrate form and the amount of those nitrate

is 50 times as much as the amount of fixed nitrogen in the atmosphere [9]

The formation of nitrogen in soil mostly is the fixed nitrogen such as NO3 and NO2 Most of them come from organic matter which is buried in marine and freshwater sediments Blatt et al suggested that the amount of fixed nitrogen in sedimentary at the Earth’s surface (1021g) is much more than the amount of fixed nitrogen in total biosphere (1019g) [19]

1.1.2.2 Agricultural sources

a Agricultural cultivation

The production and consumption of fertilizer in the world has rapidly increased since

2016 and the trend is expected to increase further [20] The balance between the production and consumption for the nitrogen has also increased (Table 1-1) [20]

Table 1-1 The production and consumption of nitrogen in fertilizer around the

world from 2016 to 2022 (thousand tons) [20]

Total

production 153,645 155,253 157,819 16,1504 160,492 161,572 163,219 Total

consumption 105,148 105,050 105,893 107,424 108,744 110,193 111,591 Surplus 48,497 50,203 51,926 54,080 51,748 51,379 51,628 Organic and inorganic nitrogen is usually used as a source of nutrients for crops in agriculture The industry of synthetic nitrogen fertilizer is significantly developed based on low cost input (80% of atmosphere is nitrogen) However, it is reported that only 20% of the nitrogen reaches food consumers, whereas 80% remaining is released into the environment (soil, water) [8] Every year air and surface water environment received huge amount of nitrogen (N) which mainly originated from rice paddy fields Over 75% of nitrogen emission in Day-Nhue river basin was released to the air per year due to the usage of chemical fertilizers Additionally, over 84% of N runoff annually leachate to the river from chemical fertilizers [21] Nga Do-Thu et al resulted that the agriculture is the most significant source excess of nitrogen In the rural area

of Vietnam, chemical fertilizers are the most popular excess sources of nitrogen in which more than 103 ton nitrogen released into the atmosphere and nearly 25 ton nitrogen leached to the water stream [22]

b Aquaculture

Urea or ammonium nitrate in nitrogen fertilizers are applied to the fish ponds to stimulate the growth of phytoplankton and increase aquatic plants which are the natural food for fish or shrimp [23]

When the fertilizer applied to the ponds, urea in fertilizer will be hydrolyzed in water, and it leads to the yielding ammonia and carbon dioxide The total ammonia nitrogen (TAN) is analyzed for the existing of ammonia in water Ammonia toxicity appeared

at high feeding rates Aquatic plants absorb the ammonium and converted to organic nitrogen, but when the plants die and decay, the ammonia will be released and

transform to nitrate and nitrite by nitrification bacteria In aquatic animal, nitrite can

be toxic because the ability to transport oxygen in blood is interfered [23]

The growth of aquatic animals can be increased significantly by using the fertilizer that contain 25 to 40 percent of crude protein [24] Claude E Boyd reported that around 40% of nitrogen fertilizer is converted into the biomass, and the rest which are the uneaten feed and faces is converted to ammonia by microorganisms In the North of Vietnam, the amount of nutrients from fertilizer for aquatic animal is lower than the amount of nutrients in chemical fertilizers However, the amount of aquatic fertilizers is significant with the input flows more than 15 tons per year, and the amount of nitrogen accumulated in sludge from fish ponds is 32 tons per year [22]

c Livestock and poultry operations

Figure 1-2 The meat production by meat type (2028 vs 2016-18)

Note: c.w.e is carass weight equivalent

Source: OECD/FAO (2019), “OECD-FAO Agricultural Outlook”, OECD Agriculture statistics (database)

doi: dx.doi.org/10.1787/agr-outl-data-en

According to Food and Agriculture Organization (FAO), the meat production in the world is projected to 12% higher in 2028, with more than 50% of production is come from developing countries (Figure 1-2) Pig and poultry are expected the main

World Developed countries

production in developing countries with the production of these meat accounted for 38% each type In developed countries, the meat production will be predicted 8% higher by 2028 compared to the base period

Due to the significantly increase of meat production, the excessive manure application has become one of the biggest concern in the world Many researchers showed that manure discharged into environment can pollute the water and soil resources at local and regional level, and the emission of greenhouse gas will appear globally [25], [26] The amount of those manure will affect to the water and soil resources by different ways such as leaching and runoff, which poses a serious threat

to the environment For example, if nitrate leach to the groundwater, there will be a eutrophication or overload of NO3 in water resources causing harmful factors to human health [9], [27] Nitrogen is one of the vital elements for animals for living activities like metabolic activity and body gain The metabolic activity of animal which is various by different factors like species, sex, age, and living conditions determines the amount of nitrogen excreted While most nitrogen is absorbed into the body, unused nitrogen which is consumed by feed and feed supplements is excreted via urine and manure (Figure 1-3) [28]

Figure 1-3 The process of manure-N production [28]

Normally, there are two way to excrete manure which are directly excreted to the fields or collected and stored in a biogas tank to transform fuel and fertilizers Nga Do-Thu [22], [29] estimated that approximately 25% of pig manure, which accounting for 58% of the Nitrogen source was freely discharged to the drainage system causing difficulties in wastewater treatment

1.1.2.3 Urban sources

a Rainwater run-off

Ammoniac nitrogen is the most popular form of non-reactive nitrogen in rainwater [9] In the UK, Cape et al suggested that 24-40% of dissolved nitrogen in precipitation is organic nitrogen (Table 1-2) In late summer, it is reported that the concentration of water-soluble organic nitrogen is more higher, whereas the maximum concentration of NH4 and NO3 is calculated in spring [30]

Table 1-2 The concentration of nitrogen in precipitation across United

winter Coal combustion and vehicle exhausts were the main sources causing nitrate

in the precipitation

b Municipal waste/wastewater

Municipal solid waste now has become “one of the biggest challenges in urban cities” [32] World Bank projected that by 2025 the generated municipal solid waste (MSW) will increase to 4.3 billion tons, and it will continuously and dramatically raise up with the increase of population [33]

Table 1-3 Waste management and treated in selected cities [32]

City, Country

Coverage of waste collection and sweeping

(%)

Controlled disposal/ incineration of total disposed/incinerated (%)

China, Philippines was accounted for 70-100%, and nearly 100% of the waste is treated by landfill and incinerator except India and Peru with the rate of 78% and 81%, respectively Furthermore, Jokela state that [34] the end-up productions of food are solid waste and sludge produced by wastewater treatment In wastewater, the nitrogen concentration ranges from 20 to 85 mgN/L [4], [27], and most of them is transformed into other form of nitrogen and released to the atmosphere or contained

in the sludge

Mostly, the MSW is disposed in landfills which leads to the contamination of soil and water resources, and also the emission of greenhouse gases [8], [9], [33], [34] Jokela [34] estimated that landfill can release N2O to more than 0.04 tons of CO2 equivalent per ton of solid waste Additionally, recycling of materials and incineration recently have been popular waste treatment in the world with the percentage of these treatment

in 2013 was 27% and 15%, respectively [8] As a reference, Park et al [35] suggested that in Korea case, the incineration can yield between 71 to 153g N2O per ton of waste Composting and digesting of biodegradable matter in MSW has been researched for many year, and the products as fertilizers has been applicate around the world [8], [36] Although the application of waste-based fertilizer are very promising as the potential of nutrients recovery and the effective management of compostable waste [36], this fertilizer is still frightened by consumers due to the toxic content and potential pathogens in the fertilizer as well as the efficiency of the usage

of waste-based fertilizer

1.1.2.4 Industrial sources

The amount of nitrogen in industrial wastes and its impact to the environment is of little concern Several forms of nitrogen are found in industrial waste such as ammonia and cyanide (CN-) [10], [13] In Hai Duong, Ta et al reported that in 2012, more than 2000 tons of total nitrogen was released to the surface water from the industrial parks [37] The manufacturing of coke, gas manufacturing, metal cleaning, plating, case hardening and other chemical are sources of ammonia, and cyanide [10] However, it is reported that nearly 50% of nitrogen in raw materials is transform to

gas and release into the atmosphere [38] Haber Bosch process is known as a fertilizer manufacturing process, but it also provide the nitrogen compound (ammonia) as a raw material to other productions like the production of nylon and plastics [13]

In additional, the concentration of nitrogen normally present in the food processing wastewater, especially the fisheries wastewater, but Gonzalez stated that their concentration is minimal in most cases [39] The large amount of protein content on fish and marine invertebrate (15-20% of wet weight) leads to the high level of nitrogen [40] Furthermore, sometime the high concentration of ammonia detected because of the high blood and slime content in wastewater According to the report

of FREMP in some fish manufacturing plants, the ammonia concentration ranged from 0.7 mg/L to 69.7 mg/L [41]

1.2 Waste sludge and its recovery and reuse

1.2.1 Definition and classification of sludge

1.2.1.1 Definition

Sludge is a homogeneous composition of solids and water with the water content (moisture) greater than 70% The particle size of sludge is less than 2mm There are many sources generated sludge in the urban areas such as domestic WWTP, septic tank, river and lake, sewer drainage, and industrial activities [42]

Currently the concept of "sludge" has not been defined in Vietnamese legal documents US-EPA (US Environmental Protection Agency) defines the sludge as the final semi-solid product generated from the treatment of civil and industrial wastewater from a mixed WWTP The term is sometimes also used as a general term for solids separated from suspension in water, which often contains significant amounts of water between voids of solid particles Wastewater treatment processes lead to the removal of pollutants and transfer them to a smaller volume phase (slurry) Thus, after the process of treatment and cleaning of wastewater, clean water can be reused and the resulting sludge will be discharged Sludge disposal and treatment is difficult due to the large amount of sludge, different components, high humidity and

sludge that are difficult to filter Waste treatment and sludge costs account for about 25-50% of total waste management costs [43]

Sludge from urban domestic sewerage system is a liquid, solid or slurry residue generated by the process of transporting and converting wastewater in sewers, which

is a mixture of organic and inorganic substances This includes all types of sludge collected from urban drainage pipes as a by-product of this process Sludge consists mainly of water, minerals and organic matter

Sludge can contain volatile substances, pathogenic organisms, bacteria, heavy metals, inorganic ions along with toxic chemicals from industrial wastes, household chemicals and pesticides The amount of sludge increases with the level of population growth and production growth The amount of sludge is often very large and pollutes the environment if not handled well [43]

1.2.1.2 Classification

Sludge is classified based on their origin and composition The composition of the sludge depends on the nature of the initial pollution of the water and the cleaning method: physical, chemical, biological and biological treatment [43], namely:

- Hydrophilic organic sludge: It is the most common type, the difficulty of drying sludge is due to the presence of most hydrophilic colloids The sludge usually comes from wastewater sludge, which volatiles content can reach 90% of all dry matter (wastewater of food industry, organic chemistry)

- Hydrophilic inorganic sludge: These sludge contains metal hydroxides formed by physicochemical methods by precipitating metal ions in the treated water (Al, Fe, Zn, Cr) or by using infinite flocculants (Ferrous or ferrite salts, aluminum salts)

- Oil-containing sludge: It is characterized by the presence of small amounts of oil or mineral grease (or animal) in the waste These substances are either emulsified or absorbed by hydrophilic sludge particles Partial bio-sludge may also be present in the event of final treatment with activated sludge (For example, oil refinery wastewater treatment)

- Hydrophobic inorganic sludge: Those sludge are characterized by a predominant proportion of special substances with small water holding content (sand, silt, slag, forged scales, and crystallized salt)

- Fibrous sludge: this type of sludge is generally very easy to dry unless the sludge recovery causes the fibers to turn into a hydrophilic type due to the presence of hydroxyl or biological sludge

1.2.2 Characteristics

1.2.2.1 Sources of sludge

Sludge is generated from many sources [43]:

- Sludge from wastewater treatment system: Urban wastewater includes household wastewater, industrial wastewater Thus, wastewater is formed during human activities Urban: high levels of organic matter (55-65% of total contaminants), many microorganisms including pathogenic, organic decomposing bacteria necessary for the process of metabolism wastewater Urban wastewater is rich in organic matter and nutrients, which is the source for the growth of bacteria (including pathogenic bacteria) as one of the major sources of pollution to the water environment Municipal wastewater through sewer networks, is transferred to municipal WWTPs and urban drainage systems Sludge generated by this process is the result of sediment-deposited material in sewer systems and the activity of microorganisms living in these systems, turning sand into mud This sludge is often contaminated with toxic organic and inorganic compounds, depending on the source of the effluent, due to the concentration of the materials in the remaining solids as a result of water treatment waste

- Waste sludge from septic tanks;

- Waste sludge from animal manure: Animal manure is waste products of the digestive process of cattle and poultry that are excreted from the digestive tract Therefore, animal manure is a good nutritional product for plants or other organisms such as fish, worms, etc Due to the rich composition of organic matter, they are easily

decomposed into toxic products, when released into the environment that can pollute pets, humans, and other organisms

- Aquaculture sludge: is a source of sediment deposited into the square of shrimp farming, a source of extremely dangerous waste spreading problems and environmental pollution After 3-4 months of sedimentation on these squares, shrimp ponds can be up to 20-30 cm thick covering the bottom of the shrimp farming area Some research results on shrimp waste sludge composition have shown extremely complex components, residues and chemical materials used in shrimp farming processes such as lime, chemicals, sulfur, mud deposition alum in soil contains environmental toxins, pathogenic bacteria that raise shrimps, green algae and fungal pathogens and especially anaerobic decomposition products such as NH3, H2S, CH4

are harmless agents The same danger for the shrimp

1.2.2.2 Characteristics

More than 60,000 chemical toxins have been found in sludge Stephen Lester (CHEJ) gathered information from Cornell University researchers and the Association of Civil Engineers who determined that the waste sludge contains the following toxins [44]:

- Polychlorinated biphenyls (PCBs)

- Chlorine insecticide including DDT, dieldrin, aldrin, endril, chlordane, heptachlor, Lindan, mirex, kepone, 2,4,5-T, 2,4-D

- Chlorination of compounds like dioxin

- Aromatic polycyclic hydrocarbons

- Heavy metals: arsenic, cadmium, chromium, lead and mercury

- Bacteria, viruses, protozoa, parasitic worms and fungi

- Other toxins include: asbestos, petroleum products and industrial solvents

In 2009, US-EPA published a national report on sludge, including reports on levels

of metals, chemicals and other materials contained in a statistical sample of sewage sludge Some highlights include:

- Ag: 20 mg/kg of sludge, some sediments have a particularly high content of up to

200 mg of Ag/kg of sludge, Ba: 500 mg/kg, while Mg is present at the rate of 1 g/kg

of research on sludge characteristics in Indiana (USA) show that sludge contains about 50% organic matter and 1-4% inorganic carbon Organic nitrogen and are major components of N in the sludge However, the largest variation is the composition of heavy metals such as Cd, Zn, Cu, Ni, Pb in the sludge [45]

1.2.3 Impacts of sludge to environment and human health

Sludge is identified by US-EPA as a pollutant In 2011, US-EPA commissioned a study at the National Research Council of America (NRC) to determine the risk to the health of animals and human In this paper, the NRC points out that many of the dangers of sludge have not been clarified or given adequate attention, especially when urban sludge is used as a useful fertilizer or wastewater is used as a source of irrigation water

Sludge contains pathogenic bacteria, viruses and protozoa along with other parasitic helminths that can increase the potential risk to human, animal and plant health Adding fresh mud to the soil caused the level of E coli bacteria to rise to a much greater value [46] According to the World Health Organization -WHO (1981), a

health risk report has identified Salmonella and Taenia as major pathogenic microorganisms as the greatest concern

Sludge from WWTPs, though treated through complex processes of reduced pollution levels, does not eliminate pathogens and hazardous substances at low levels of components such as PAHs, PCBs, dioxins, heavy metals Other studies conclude that plants absorb large amounts of heavy metals and toxic contaminants stored products, which are then consumed by humans [47]

Sludge impact on human health can be divided into visible effects immediately after exposure (such as: odor, infection due to inhalation / swallowing bacteria) or arising from long-term exposure (exposure to metal dispersed from the treatment of sludge), has a gradual effect, not immediately noticeable Those most at risk are those who are frequently exposed to the sludge such as sewage treatment workers, sludge dredging workers, composting facilities, farmers and households [44]

In Vietnam, there is currently no specific statistics on the harmful effects of sludge

on the environment However, in reality, a large amount of sludge is sucked from drainage systems, septic tanks, rivers and lakes and sludge from water treatment plants discharged into the environment, causing serious consequences Sludge from drainage systems and from sewage treatment plants is pre-treated or untreated, transported to landfills or dumped at unspecified locations, affecting the environment surrounding, and causing air pollution and especially osmosis, polluting groundwater and surface water, leading to the decrease of water quality

The composition and properties of sludge are important in studying the ability to utilize mud for different purposes (used as fertilizer, improving agricultural land, leveling, producing construction materials construction, etc.), it also allows to identify the causes of the accumulation of contaminants in the mud of each canal as well as the toxic pollution components in the mud Therefore, the potential impacts

of waste sludge on the environment include:

- Pollution of groundwater: In the sludge component contains a large amount of water,

in the dry season this water is not enough to penetrate into the aquifer and easily evaporate However, in the rainy season, it can mix toxic substances in mud and seep into groundwater, contaminating groundwater

- Pollution of surface water: There is a certain balance between sediment environment and water environment, when environmental properties change, pollutants accumulated in sediment can be mixed back into polluting water which will cause the contamination

- Air pollution: Anaerobic decomposition of sludge will create odorous gases such as

H2S, CH4, NH3 causing greenhouse effects and affecting humans

- Pollution of soil environment: Pollution of the soil is mainly caused by toxic components in sludge in high concentrations, including organic matter, heavy metals and even persistent substances such as nylon bags, Iron cans in sludge will pollute the soil and be difficult to overcome

- Impact on the ecosystem: Losing the urban landscape, affecting aquatic life in the country

- Impacts on animals: Sludge is also the habitat of thousands of species such as microorganisms and through the food chain, sludge can affect higher animals including humans , especially heavy metals containing in sludge

The amount of KLN in the sludge is the first concern when dredging canals, closely related to the purpose of sludge reuse or the improper dumping impacts such as affecting ecosystems in the landfill Heavy metal components are easily absorbed on the surface of organic and inorganic suspended substances When these substances settle to form sediment, heavy metals will also accumulate in the mud Some heavy metals are trace elements that are indispensable to organisms in their metabolism, but others are toxic There are 6 basic elements (Fe, Zn, Mn, Cu, Mo, Co) called essential micronutrients for plants Other metals such as Ca, Si, Ni, Se, Al are necessary for plant assimilation but not needed for other organisms For Hg and Pb, metal

components are absolutely not necessary for plants, microorganisms and are toxic to humans [44]

1.2.4 Technical of reusing sludge

1.2.4.1 Sludge treatment technologies

A few decade ago, landfill was the main treatment in Europe In 1999, 57% of urban sludge (MSW) was landfilled, compared to 67% in 1995 in Western Europe, and 83%

in Central and Eastern Europe [48] During the 1990s and until later, important research, development and commercialization of the biogas composting system appeared in Europe At the same time, the designers and suppliers of biogas composting systems are combining the preliminary treatment process of waste, biogas composting and composting techniques to simultaneously reduce the volume and percentage of organic matter However, landfill is becoming a much more costly disposal option for a number of reasons, such as population growth and changing regulations that require new landfill investments in technology and strict management (Millner et al., 1998), increases in emissions of greenhouse gases CH4, CO2 and the introduction of heavy metals into water and soil from landfills, most importantly the disposal of landfills in landfills Landfills do not take advantage of the nutritional value and nature of biological solids, and occupying landfill space can be better used for other types of waste making this option less attractive Table 1-4 listed some selected technologies for resources recovery in waste sludge which is popular in the world

Table 1-4 Selected technologies for resources recovery in waste sludge [49]

Type of treatment Purposes Treatment process Final products

Aerobic/anaerobic

digestion

Stabilizing the biodegradable fraction of organic matter to reduce the putrefaction risk and the pathogen

concentrations

Specific bacteria promote the stabilization of the biodegradable fraction of the organic matter

Bio-solid used as organic fertilizers in agriculture with a limited quantity and further treatment like disinfection

Type of treatment Purposes Treatment process Final products

Chemical treatment

(alkaline

stabilization)

Stabilizing the biodegradable fraction of organic matter to reduce the putrefaction risk and the pathogen

concentrations

Chemical oxidation

of the organic matter

accomplishes sludge stabilization

Bio-solid used as organic fertilizers in agriculture with a limited quantity and further treatment like disinfection

Composting Stabilizing the

biodegradable fraction of organic matter to reduce the putrefaction risk and the pathogen

concentrations

An aerobic decomposition process of organic matter achieved through controlled conditions of temperature, moisture, oxygen and nutrients

Using for nurseries, horticulture, and landscaping

Thermal drying

(palletization)

Reducing the water content in sludge, stabilized the sludge, and reducing the pathogen

concentrations

Heat stabilizes the volatile fraction of sludge in

hermetically sealed containers

Pellets for agriculture reuse, sanitary landfills disposal or incineration

Landfill disposal Safe disposal of

solid refuse onto soil without the damage

of public health and environmental impacts

Sludge incubated in enclosed cells will ferment,

decompose and produce gas The essence of

technology is turning waste and sludge into gas to run generators

Non nutrient recovery in the process The energy generated in the process will be carried out under the gas recovery

mechanism from the landfill and

generating under the Clean Development Mechanism (CDM-Clean Development Mechanism)

1.2.4.2 Application of reusing and recovery sludge in some countries

Nowadays, sludge is becoming a burden even in countries with advanced economies, science and technology in the world According to the US Environmental Protection Agency (US-EPA), sludge disposal costs account for up to 50% of the system