Enhancement of nutrient removal from anaerobically digested swine wastewater using hybrid constructed wetlands with foamed waste glass and external carbon source

VIETNAM NATIONAL UNIVESITY, HANOI VIETNAM JAPAN UNIVERSITY PHAM THI KIEU CHINH ENHANCEMENT OF NUTRIENT REMOVAL FROM ANAEROBICALLY DIGESTED SWINE WASTEWATER USING HYBRID CONSTRUCTED WET

VIETNAM NATIONAL UNIVESITY, HANOI

VIETNAM JAPAN UNIVERSITY

PHAM THI KIEU CHINH

ENHANCEMENT OF NUTRIENT REMOVAL FROM ANAEROBICALLY DIGESTED SWINE WASTEWATER USING HYBRID CONSTRUCTED WETLANDS WITH FOAMED WASTE GLASS AND EXTERNAL CARBON

SOURCE

MASTER’S THESIS

VIETNAM NATIONAL UNIVESITY, HANOI

VIETNAM JAPAN UNIVERSITY

PHAM THI KIEU CHINH

ENHANCEMENT OF NUTRIENT REMOVAL FROM ANAEROBICALLY DIGESTED SWINE WASTEWATER USING HYBRID CONSTRUCTED WETLANDS WITH FOAMED WASTE GLASS AND EXTERNAL CARBON

SOURCE

MAJOR: ENVIRONMENTAL ENGINEERING

CODE: 8520320.01

SUPERVISORS:

Assoc Prof Dr SATO KEISUKE

Dr NGUYEN THI AN HANG

Hanoi, 2020

ACKNOWLEDGMENT

First of all, I would like to express my profound and sincere gratitude to my Principal Supervisor, Associate Professor Dr SATO Keisuke, JICA Expert, a lecture of Master’s Program in Environmental Engineering, VNU Vietnam Japan University for giving me excellent guidance and reviewed the dissertation of my thesis He always gives me various advisement to help me overcome many challenges and completes this dissertation I also would like to thank to Dr Nguyen Thi An Hang, my Co-supervisor for giving me deep insight in the field of constructed wetlands and profound comments on my experimental results

I would like to express my warm and sincere thanks to Prof Jun Nakajima, Assoc Prof Dr Cao The Ha, Assoc Prof Dr Ikuro Kasuga and Dr Tran Thi Viet Ha and MEE staffs, Department Master’s Program in Environmental Engineering, VNU Vietnam Japan University for their teaching and their kind supporting during my studying, their wonderful guidance and valuable remarks to improve my knowledge related to my thesis

I would like to express my warm and sincere thanks to Prof SODA Satoshi, Department of Civil and Environmental Engineering, Graduate School of Science and Engineering, Ritsumeikan University for his wonderful guidance and valuable remarks to improve my knowledge related to my thesis during my internship

I am warmly thankful Mrs Makiko Mishina and Ritsumeikan students for their enthusiasm, friendliness and kind help me during internship

I would like to thanks to Japan International Cooperation Agency (JICA), VNU Vietnam Japan University (VJU) and Ritsumeikan University (RITs) and special the collaboration between Vietnam and Japan government for giving me valuable experiences as studying at international environment

The last but not least, I would like to express my whole-hearted to all of my family and my friends This thesis could not have been done without their supporting and encouragement

Hanoi, 14th August, 2020 Pham Thi Kieu Chinh

TABLE OF CONTENTS

ACKNOWLEDGMENT i

TABLE OF CONTENTS iii

LIST OF TABLES v

LIST OF FIGURES vi

LIST OF ABBREVIATION viii

INTRODUCTION 1

CHAPTER 1 LITERATURE REVIEW 5

1.1.Swine wastewater in Vietnam 5

1.1.1 Characteristics of Swine Wastewater 5

1.1.2 Characteristics of the Anaerobically Digested Swine Wastewater 5

1.1.3 Treatment technologies of the AD SWW 8

1.2.Constructed Wetlands 8

1.2.1 Definition and classification of Constructed Wetlands 8

1.2.2 Nutrients removal by Hybrid Constructed Wetlands 9

1.2.3 The role of plant 13

1.3.Strategies for enhancing the nutrient removal of the AD SWW 14

1.3.1 Utilization of Foamed Waste Glass 14

1.3.2 Utilization of external carbon source 15

CHAPTER 2 MATERIAL AND METHODOLOGY 17

2.1.Material of Hybrid CWs components 17

2.1.1 Substrate 17

2.1.2 Plant 18

2.1.3 External carbon source 19

2.2.Experiment set-up 20

2.2.1 Elution tests of carbon and nutrients from CCF 20

2.2.2 Adsorption tests of phosphorus to filter materials 20

2.2.3 Wastewater treatment by Lab-scale Hybrid CWs 23

2.2.4 Filter materials and plants characteristic 27

2.3.Analytical methods 28

2.3.1 Characterization of filter materials 28

2.3.2 Apparatus 30

2.3.3 Analysis methods 31

2.4.Calculation and statistical analysis 31

CHAPTER 3 RESUTLS AND DISSCUSION 36

3.1.Filter materials characterization and its adsorption tests 36

3.1.1 Filter materials characterization 36

3.1.2 Adsorption experiment 38

3.2.CCF characterization and its elution tests 44

3.3.Treatment performance by Hybrid CWs 46

3.3.1 pH 46

3.3.2 DO 47

3.3.3 COD treatment performance 48

3.3.4 TP treatment performance 50

3.3.5 PO43- treatment performance 51

3.3.6 Nitrogen concentration treatment performance 52

3.3.7 NH4+-N treatment performance 53

3.3.8 NO3--N treatment performance 55

3.3.9 NO2--N performance treatment 56

3.4.Nutrient mass balance 56

CONCLUSION AND RECOMMENDATION 60

REFERENCES 62

LIST OF TABLES

Table 1.1 The characteristics of anaerobically digested swine wastewater 7

Table 1.2 The advantage and disadvantage of Hybrid CWs 10

Table 1.3 Comparison of treatment performance of different plant in CWs systems 14

Table 1.4 External carbon source using in constructed wetlands 16

Table 2.1 The Isotherm models using in batch studies 22

Table 2.2 Kinetic models used in batch studies 23

Table 2.3 The layer of lab-scale Hybrid CWs Systems 24

Table 2.4 The methods of water parameters analysis 31

Table 3.1 Comparison of the chemical composition between Super Sol, Porous Alpha, and Limestone in this study and other materials 37

Table 3.2 The Langmuir model and Freundlich model in P adsorption capacity of filter materials 43

Table 3.3 The kinetic model of Super Sol (SS) 43

Table 3.4 The elemental fraction of Coconut Fiber (CCF) 44

LIST OF FIGURES

Figure 1.1 Principle of anaerobic digestion 6

Figure 1.2 The schematic of classification constructed wetlands 9

Figure 1.3 Nitrogen removal mechanism in Constructed Wetlands 11

Figure 1.4 Phosphorus cycle of soluble and particulate phosphorus 12

Figure 1.5 Foamed Waste Glass (a Super Sol; b Porous Alpha) 15

Figure 2.1 The manufacturing process of Super Sol 17

Figure 2.2 The manufacturing process of Porous Alpha 18

Figure 2.3 Filter materials (a Super Sol (SS); b Porous Alpha (PA); and c Limestone (LS)) 18

Figure 2.4 Cyperus alternifolious 19

Figure 2.5 Coconut Fiber 19

Figure 2.6 Schematic diagram of experiment laboratory-scale hybrids constructed wetlands 25

Figure 2.7 Lab-scale Hybrid CWs 26

Figure 2.8 X-ray fluorescence spectrometer (XRF) JSX 1000s, USA 28

Figure 2.9 Rigaku MiniFlex 600 Power X-ray diffractometer 29

Figure 2.10 NC-22F 29

Figure 3.1 X-ray diffraction patterns of filter materials: (a) Super Sol (SS), (b) Porous Alpha (PA), and (c) Limestone (LS) 37

Figure 3.2 The effect of adsorbent dosage on P adsorption capacity of Super Sol (SS), Porous Alpha (PA), and Limestone (LS) 39

Figure 3.3 The effect of pH on P removal efficiency of Super Sol (SS), Porous Alpha (PA), and Limestone (LS) 40

Figure 3.4 The effect of contact time on P adsorption capacity of Super Sol (SS), Porous Alpha (PA), and Limestone (LS) 41

Figure 3.5 The effect of initial concentration on P adsorption capacity of Super Sol (SS), Porous Alpha (PA), and Limestone (LS) 42

Figure 3.6 The COD, N, and P releasing in Coconut Fiber 46

Figure 3.7 pH value in hybrid CWs 47

Figure 3.8 DO concentration in the period operation 48

Figure 3.9 COD removal in hybrid CWs 49

Figure 3.10 TP concentration and removal efficiency in hybrid CWs 50

Figure 3.11 PO43- -P concentration and removal efficiency in hybrid CWs 52

Figure 3.12 NH4+ -N, NO3- -N and NO2- -N concentration variations of influent and effluent in Hybrid CWs 53

Figure 3.13 NH4+ -N concentration and removal efficiency in hybrid CWs 54

Figure 3.14 The concentration of NO3--N in Hybrid CWs 55

Figure 3.15 The concentration of NO2--N in Hybrid CWs 56

Figure 3.16 TP accumulated in plant 57 Figure 3.17 TP accumulated in filter materials 58 Figure 3.18 Phosphorus mass balance in whole Hybrid CWs 59

INTRODUCTION

In Vietnam, industrial livestock production in Vietnam plays a significant role Vietnamese farmer’s income According to General Statistic Office of Vietnam (2017) has reported the number of pigs in Vietnam approximately 31.4 million pigs

in 2017 and is expected to increase to 33.32 million by 2020 With the growing number of livestock farms are generated enormous amount of solid waste and wastewater, resulting in negative environmental consequences and threatening human health Dinh et al., (2020) reported that 1000 kg of pork are generated 39 kg

of manure, 84 kg of urine, 11 kg of total solids (TS), 0.027 kg of suspended solids (SS), 3.1 kg of biochemical oxygen demand (BOD5) and 0.29 kg of ammonia-nitrogen NH4+− N Dinh et al., (2017) reported that 36% of all animal manure is discharge directly into the environment, with the rate ranging from 16% at intensive farms to 40% at small-scale farms Therefore, Swine wastewater (SWW) contains high levels of nitrogen, phosphorus and organic matter (Nagarajan et al., 2019) The quality of the effluent barely meets the requirement of QCVN 40: 2011/BTNMT There are several technologies for being treated swine wastewater such as microbial fuel cells (MFCs) with flocculation (Ding et al., 2017), trickling filter (Saucedo Terán et al., 2017), duckweed ponds (Dinh et al., 2020; Mohedano et al., 2012) In Vietnam, anaerobic digestion is considered an appropriate solution to convert organic matter into biogas (Nagarajan et al., 2019) However, the anaerobically digested swine wastewater still remains high level of organic matter and nutrient This technology results in the negative health and environmental consequences such

as deterioration of water quality and eutrophication of the lake

Over the past few decades, constructed wetlands (CWs) have attracted attention because of their capacity to remove pollutants such as nitrogen, phosphorus, BOD, COD, heavy metal and pathogen; and their low construction, operation, and maintenance costs (Li et al., 2014; Vymazal, 2013; Wu et al., 2015) Recently, CWs have shown the major process affecting the organic compound loads in wetlands

chemical (oxidation, reduction, cation exchange, hydrolysis, photolysis), biological (plant absorption and metabolism), and biochemical process (microbial degradation) (Vymazal and Brezinova, 2015) In addition, Hybrid constructed wetlands (CWs) is

a combination of Vertical flow and Horizontal Flow, can be increasing employed for the treatment of wastewater (Vymazal, 2013) However, one of the issues with regards to the extensive use of CWs is the inadequate phosphorus (P) removal ability (Vohala et., 2011); and other problems that negatively affect the nitrogen removal efficiency due to a lack of carbon source (Wu et al., 2015)

In order to solve the problem, this study aims at improvement of nutrient removal from anaerobically digested swine wastewater by using Foamed Waste Glass (e.g Super Sol and Porous Alpha) and external carbon source in hybrid constructed

wetlands To achieve this ultimate goal, a research titled “Enhancement of

Nutrient Removal from Anaerobically Digested Swine Wastewater Using Hybrid Constructed Wetlands with Foamed Waste Glass and External Carbon Source”

was carried out with the specific objectives as follows: (i) Evaluation of the effect

of Foamed Waste Glass on phosphorus removal; (ii) Evaluation of the denitrification process improvement by external carbon source in Hybrid CWs; and (iii) Clarification the mechanism of nutrient removal by using Foamed Waste Glass and external carbon source in Hybrid CWs;

This thesis comprises of 3 main Chapter with the following major contents:

Introduction This part shown the research background, objective, scope and scale,

and research significance

Chapter 1 Literature review: This Chapter outlines the brief background,

describes the outline of the status of anaerobically digested wastewater, constructed wetlands, the nutrient removal method by Hybrid Constructed Wetlands Especially, this study focuses on the strategies for enhancing the nutrient removal anaerobically digested swine wastewater using Foamed Waste Glass and external carbon source

Chapter 2 Materials and methodology: This Chapter illustrates the material and

methodology that was used to in this study Especially, this study describes the experiment set-up

Chapter 3 Results and discussion: This Chapter illuminates the results of Foamed

Waste Glass (e.g Super Sol and Porous Alpha) and Limestone characteristics, the results of phosphorus removal by Foamed Waste Glass and Limestone, nutrient treatment performance of the Hybrid CWs, and evaluation of the nutrient removal mechanism by mass balance

Conclusion and recommendations: This Chapter represents the summary of this

study and the further implementation of this research

Introduction

Chapter 1 Literature review

Chapter 2 Materials and Methodologies

Swine wastewater

in Vietnam

Constructed Wetlands

Strategies for enhancing the nutrient removal of AD SWW

Material for

Hybrid CWs

components

Experiment set-up

Analytical methods

Calculation and statistics analysis

Chapter 3 Results and Discussion

Filter materials

characteristics and

adsorption test

Coconut Fibre characterization and elution test

Treatment performance by Hybrid CWs

Nutrient mass balance

Conclusion and Recommendations

CHAPTER 1 LITERATURE REVIEW

1.1 Swine wastewater in Vietnam

1.1.1 Characteristics of Swine Wastewater

In Vietnam, industrial livestock production in Vietnam plays a significant role Vietnamese farmer’s income According to General Statistic Office of Vietnam (2017) has reported the number of pigs in Vietnam approximately 31.4 million pigs

in 2017 and is expected to increase to 33.32 million by 2020 (General Statistical Office, 2017) With the growing number of livestock farms are generated enormous amount of solid waste and wastewater, resulting in negative environmental consequences and threatening human health The swine wastewater from pig farm is

an emerging problem in many rural areas of Vietnam Swine wastewater (SWW) is

a combination of components such as urine, rinse, and bathing water for cattle and several parts of animal manure Bui et al., (2011) reported that 1000 kg of pork are generated 39 kg of manure, 84 kg of urine, 11 kg of total solids (TS), 0.027 kg of suspended solids (SS), 3.1 kg of biochemical oxygen demand (BOD5) and 0.29 kg

of ammonia-nitrogen NH4+− N SWW consist of a wide range of pollutants such as

955 – 2753 mg.L-1 volatile suspended solids (VSS), 1528 – 4521 mg.L-1 suspended solid (SS), 873 – 1690 mg.L-1 biochemical oxygen demands (BOD), 1794 – 3871 mg.L-1 chemical oxygen demands (COD), 421 – 778 mg.L-1 Total Kjeldahl Nitrogen (TKN) and 131 - 512 mg.L-1 total phosphorus, respectively (Nguyen et al., 2012) Pollutants have high potential to cause significant environment pollutant The quality of the effluent cannot reach the requirement of QCVN 40: 2011/BTNMT

1.1.2 Characteristics of the Anaerobically Digested Swine Wastewater

There are several technologies for being treated swine wastewater such as microbial fuel cells (MFCs) with flocculation (Ding et al., 2017), trickling filter (Saucedo Terán et al., 2017), duckweed ponds (Mohedano et al., 2012) In Vietnam, anaerobic digestion is considered an appropriate solution to convert organic matter into biogas (Nagarajan et al., 2019) Biogas contains methane in addition to CO2,

H2S, and H2 as gaseous products along with a COD rich liquid digestate (Nagarajan

et al., 2019) The liquid digestate generated by anaerobic digestion is still rich in organic carbon, nitrogen and phosphorus, which should be treated before environment release

Figure 1.1 Principle of anaerobic digestion (Lin at al., 2018)

There are four phases of biological process such as hydrolysis, acidogenesis, acetogenesis and methanogenesis Throughout hydrolysis, polymers such as liquids, polysaccharides, proteins and nucleic acids and soluble organic compounds (e.g amino acids and fatty acid) is converted into monomers by extracellular enzymes In the acidogenesis, volatile fatty acids (VFAs) are produced by acidogenic bacteria

At the acetogenesis stage, acetogens are produced mainly acetic acid as well as CO2and H2 At the methanogenesis stage, CH4 and CO2 are produced approximately 55

- 80 % and 20 - 45 %, respectively (Bernet and Béline, 2019)

The anaerobically digested swine wastewater consists of organic compounds, inorganic and nutrient There are many forms of nitrogen in wastewater such as

organic nitrogen, NH4+, NO3−and NO2− Phosphorus exist many kinds of form such as orthophosphate (HPO42−, H2PO4, PO43−), polyphosphate and organic phosphorus It creates by-product such as NH3, H2S , CH4 and CO2, causing air pollutants and greenhouse effect

Table 1.1 The characteristics of anaerobically digested swine wastewater

1.1.3 Treatment technologies of the AD SWW

Nowadays, there are various technologies for treating anaerobically digested swine wastewater such as duckweed (Dinh et al., 2020; Zhou et al., 2018), AAO (Nguyen

et al., 2017), and constructed wetlands (Han et al., 2019a; Han et al., 2019b)

Nguyen et al., (2017) reported the treatment of pollutants from anaerobically digested swine wastewater using AAO technology with coconut fiber media The results showed that the concentration of TP cannot reach the discharged standard In addition, AAO technology requires the high technical controlling and supporting carbon source to treat nutrient

Han et al., 2019 studied a pilot-scale partially saturated tidal flow constructed wetlands (TFCW) based on in-situ biological regeneration of zeolite The results showed that the treatment efficiency was 73,79% COD, 72,99% NH4+-N and 70,71% TN at 16 oC, respectively (Han et al., 2019) Han set al., 2019 reported that comparation between tidal flow and intermittent flow in constructed wetlands to treat anaerobically digested decentralized swine wastewater The finding showed that constructed wetlands using tidal operation achieved 85,94% COD, 61,20%

NH4+-N, 57.47% TN, respectively (Han et al., 2019) However, the concentration of COD, NH4+-N and TN in the effluent cannot achieve the discharge standard

1.2 Constructed Wetlands

1.2.1 Definition and classification of Constructed Wetlands

Constructed wetlands (CWs) are artificial technology because of their capacity to remove pollutants such as nitrogen, phosphorus, BOD, COD, heavy metal and pathogen; and their low construction, operation, and maintenance costs (Li et al., 2014; Vymazal, 2013; Wu et al., 2015) Recently, CWs have shown the major process affecting the organic compound loads in wetlands such as physical (volatilization, photochemical oxidation, sedimentation, sorption), chemical (oxidation, reduction, cation exchange, hydrolysis, photolysis), biological (plant absorption and metabolism), and biochemical process (microbial degradation) (Hussain et al., 2018; Vymazal and Brezinova, 2015) CWs has been used to treat

wastewater such as organic matter, nitrogen, phosphorus, heavy metal and pathogens (Hussain et al., 2018; Vymazal, 2007) Constructed wetlands are used to handle various wastewater types such as domestic wastewater (Cuong et al., 2016), stormwater wastewater (Ventura et al., 2019), agricultural wastewater (Wang et al., 2019), pig farm wastewater (La Mora-Orozco et al., 2018)

Among the various types of CWs, free surface flow (FSF) and subsurface flow (SSF) CWs are the most commonly used varied types for wastewater treatment According to the flow direction the SSF CWs can further be classified into vertical-flow (VF) and horizontal-flow (HF) type (Wu et al., 2015) Recently, step feed CW, artificially aerated CW, and baffled flow CWs have been reported by Wu et al., (2015) Another variety, Hybrid CWs which is defined a combination of vertical flow (VF) and horizontal flow (HF) (Vymazal, 2013)

Figure 1.2 The schematic of classification constructed wetlands (Wu et al., 2015)

1.2.2 Nutrients removal by Hybrid Constructed Wetlands

Vymazal (2013) has reported that hybrid constructed wetlands is the combination of vertical flow and horizontal flow systems which increases the effectiveness of treatment in systems One of the features is that after the oxidation treatment in the

VF wetlands, the nitrogen removal by denitrification is performed by anaerobic treatment in the HF wetland (Vymazal, 2013)

Table 1.2 The advantage and disadvantage of Hybrid CWs

Advantage Disadvantages

Low-cost and friendly environment; Insufficient removal of nutrient;

Sufficient removal of organic matter,

Harvesting biomass periodically to

maintain consistent performance;

a Nitrogen removal

nitrification/denitrification by microorganisms, ammonia-volatizing, N2 fixation, absorption of plants, microbial uptake, mineralization, adsorption, fragmentation, desorption, landfilling, leaching, etc (Vymazal, 2013)

Nitrification

During nitrification, ammonium is oxidized to nitrate in a biologically mediated, aerobic reaction The rate of nitrification is temperature dependent, with the reaction rate increasing as water temperature increases 1g NH4+-N requires 4.3 mg.L-1 O2 Therefore, increased levels of dissolved oxygen increase the rate of nitrification occurring in a wetland (Norton, 2014)

Figure 1.3 Nitrogen removal mechanism in Constructed Wetlands (Zigler, 2016)

First step is the oxidation of ammonium to nitrite by ammonium oxidizing bacteria through the following stoichiometric equation:

Second step is further oxidation of nitrite to nitrate by nitrite oxidizing bacteria through the following stoichiometric equation:

𝑁𝑂2−+ 𝐻2𝑂 𝑁𝑖𝑡𝑟𝑜𝑏𝑎𝑐𝑡𝑒𝑟→ 𝑁𝑂3−+ 2𝐻+ (1-2) Heterotrophic bacteria utilize carbon for formation of new biomass, responsible for BOD removal Autroheterotrophic bacteria utilize carbon from carbon dioxide for formation of new cells It also utilizes ammonia as the electron donor for formation

of nitrite and nitrate

Denitrification

Denitrification involves the biological reduction of nitrate and or nitrite to nitrogen gas in the absence of dissolved oxygen (anoxic conditions)

𝑁𝑂3−+ 𝐶𝐻2+ 𝐻+ 𝐷𝑒𝑛𝑖𝑡𝑟𝑖𝑓𝑦𝑖𝑛𝑔 𝑏𝑎𝑐𝑡𝑒𝑟𝑖𝑎→ 𝑁2 ↑ + 𝐶𝑂2+ 𝐻2𝑂 (1-3)

Denitrification is undertaken under anaerobic or anoxic conditions by microorganisms such as Pseudomonas, Micrococcus Achromobactor and Bacillus Two types of denitrification bacteria are heterotrophic and autotrophic Heterotrophic bacteria utilize organic matter to the growth of biomass Denitrification is microbially mediated by heterotrophic bacteria that require availability of a readily degradable carbon source Denitrification consumes 2.86 g

of COD reduced as organic carbon is consumed (Norton, 2014)

b Phosphorus removal

Phosphorus is one of the most polluting contaminants in wastewater treatment Phosphorus presents in three kinds of forms such as orthophosphate, polyphosphate and organic phosphorus Phosphorus removal mechanisms in wetlands mainly include peat/soil accretion, media adsorption, precipitation, plant/microbial uptake, leaching, mineralization, and burial (Hussian et al., 2018; Wu et al., 2014) In addition to chemical methods for being treated phosphorus such as precipitation and exchange of ions, biological treatment of phosphorus is conducted by annual crop processing (Andrés et al., 2018) Removal phosphorus by the adsorption-precipitation reactions with aluminium, iron, calcium and the minerals characteristic

of materials (Arteaga-Cortez et al., 2019)

Figure 1.4 Phosphorus cycle of soluble and particulate phosphorus

(Reddy et al., 1999)

1.2.3 The role of plant

Plant plays an important role in absorbing several pollutants such as phosphorus and nitrogen Plant is a good place for attaching microorganism and releasing oxygen from the root system (Jethwa and Bajpai, 2016)

There are various wetland plants such as emergent plants, floating leave macrophytes, submerged plants, and freely floating macrophytes (Vymazal, 2007;

Wu et al., 2015) There are various plants for removal nutrient such as Arachis duranensis Evovulus alsinoides, Cyperus alternifolius Linn, Philidendron hastatum, and Melampodium paludosum (Thanh et al., 2014; Van et al., 2015)

Cyperus alternifolious (commonly known as umbrella papyrus, umbrella sedge or umbrella palm) is a perennial herb and grows in humid areas or swamp land (Yan et al., 2016) It grows fast with strong root system and it can form a good landscape Cyperus alternifolious has been widely used in various CWs in many parts of the world for landfill leached, domestic wastewater, industrial wastewater treatment (Van et al, 2015; Vymazal, 2013) Cyperus alternifolious are based on the advantage of plant such as large plants to provide more biomass; strong adaptability

to environment; high removal efficiency of pollutants; high resistance to pest and diseases; tolerance of hyper-eutrophic conditions and salinity (Jia et al., 2018; Luo

et al., 2017; Van et al., 2015) Vu et al., (2016) has studied Cyperus alternifolious in Vertical flow to treat anaerobically digested swine wastewater The results showed that the removal efficiency of COD, TN and TP were 71.66%, 79.26% and 69.65%

at loading rate 47.35 (m.d-1), respectively Ebrahimi et al., (2013) studied Cyperus alternifolious in constructed wetlands to treat municipal wastewater treatment The results showed that the removal efficiency of COD, NO3−− N , NH4+− N were 72%, 88%, 32%, respectively Van et al., (2015) has studied nutrient removal from domestic wastewater using Cyperus alternifolius in constructed wetlands and results showed that phosphorus and nitrogen removal efficiency were 89% and 92%, respectively

Table 1.3 Comparison of treatment performance of different plant in CWs systems Plant HLR (m 3 ha -1 d -1 ) TN (%) TP (%) Reference

1.3 Strategies for enhancing the nutrient removal of the AD SWW

The aim of this study was to evaluate the efficiency of a hybrid constructed wetland packed with Foamed Waste Glass and coconut fibre for the treatment of effluents with high nutrient from anaerobic digester effluents from pig farms Additionally, Foamed Waste Glass is selected as high P removal efficiency while coconut fibre is

an external carbon source for denitrification process

1.3.1 Utilization of Foamed Waste Glass

Several studies in the world have proven the material containing calcium have the ability to treat phosphorus In addition, several studies reported that Foamed Waste Glass (FWG) contain calcium In this study, Foamed Waste Glass is used to CWs as substrate to test the adsorption potential of Phosphorus Substrate plays an important role in adsorption-precipitation reactions with aluminium, iron, calcium and the minerals characteristic of materials (Arteaga-Cortez et al., 2019) There are

various substrates such as natural materials, industrial by-product and man-made product (Vohla et al., 2011)

Foamed Waste Glass is by-produced from combustion of glass at high temperature

a range of 700 to 900 oC Then, foaming agent is added in the oven and heat it in the blocks when the temperature reaches up to 900 oC (Limbachiya et al., 2012)

The P-retention characteristics are likely to vary widely, depending on the glass waste and combustion process The main chemical components of Foamed Waste Glass used by Bai et al., (2014) were SiO2 (71.50%), Al2O3 (3.38%), Fe2O3 (0.31%), CaO (8.96%), and MgO (4.22%), while the main components of that used by Khamidulina et al., (2017) were SiO2 (70.5 – 73.5%), Al2O3 (1.4 – 3.4%), and

Fe2O3 (0.1%)

Foamed Waste Glass contains calcium oxide and silicon dioxide The main mechanism for P removal is through chemical precipitation of calcium phosphate as hydroxyapatite

Figure 1.5 Foamed Waste Glass (a Super Sol; b Porous Alpha)

1.3.2 Utilization of external carbon source

In this study, carbon source is added in the process of denitrification Insufficient carbon source is a factor influencing nitrogen treatment in CWs Therefore, it is necessary to supplement the external carbon source to enhance the removal of TN Several studies have shown that external carbon sources such as methanol, fructose, and glucose that play an important role in the treatment of wastewater with low C/N

ratios However, agriculture materials have paid attention as carbon source to improve the removal of TN

In order to select the carbon source for nitrogen removal, there are a variety of ways

to select the carbon source such as low cost, denitrification rate and effective nitrogen removal (Jia et al., 2018)

Coconut fiber is extracted from coconut husk Coconut fiber which is naturally fibrous, is removed from shell of coconut Coconut fiber which is abundantly available in Vietnam, is an agricultural residue used in the process of manufacturing coconut Coconut fiber (Cocos nucifera L.) can be defined as an organic matter with great specific area and high humidity, mostly used as biological filter material (Henryk et al., 2016) Nguyen et al., (2017) reported that the ability of coconut fiber

as media is in the treatment wastewater

Table 1.4 External carbon source using in constructed wetlands

Carbon

source

Wastewater type

Removal efficiency (%) System Reference

71.9% NO3--N

Horizontal subsurface flow constructed wetlands

(Yu et al., 2019)

Wheat

straw

Synthetic wastewater

NH4+-N, 96.9% TN

Vertical flow constructed wetlands

(Jia et al., 2018)

CHAPTER 2 MATERIAL AND METHODOLOGY

2.1 Material of Hybrid CWs components

Figure 2.1 The manufacturing process of Super Sol

Porous Alpha is also the type of Foamed Waste Glass which was purchased from Tottori Resource Recycling Additionally, foamed waste glass is produced by burning of mixture of crushed glass and shells Porous Alpha is a soda-lime glass consisting mainly of silicon dioxide, calcium oxide, iron oxide, sodium oxide, potassium oxide, calcium oxide and other oxides

Furnace

Continuous

Grinding Device

Glass Crushing Device

Material Input Hopper

Figure 2.2 The manufacturing process of Porous Alpha

Limestone was purchased from Ninh Binh coal Limestone is a sedimentary rock which contains more than 50% of calcium carbonate (CaCO3) Limestone is abundant in Vietnam Limestone provide a low-cost, widely available and effective material for P removal

Figure 2.3 Filter materials (a Super Sol (SS); b Porous Alpha (PA); and c

Limestone (LS))

2.1.2 Plant

In this study, Cyperus alternifolious was selected to plant in hybrid CWs 6 months

of age With a stem length of 27 - 40 cm on average and a root length of 17 - 20 cm The plants were purchased from Buoi market, Hoang Hoa Tham Street, Tay Ho, Hanoi

Figure 2.4 Cyperus alternifolious

2.1.3 External carbon source

Coconut Fiber was purchased from Buoi market, Hoang Hoa Tham Street, Tay Ho, Hanoi Coconut Fiber was derived from Ben Tre, Vietnam

Figure 2.5 Coconut Fiber

2.2 Experiment set-up

2.2.1 Elution tests of carbon and nutrients from CFF

The Coconut Fiber (CCF) was washed by distilled water and dried at 80 oC in 12h CCF was added to the flask and 500 mL DW was poured to the flask and then placed on sharking machine for 20 days at 120 rpm at room temperature 100 mL CCF of the supernatants were extracted from each flask and stored at 4oC before analysis (Ramírez-Godínez et al., 2015)

2.2.2 Adsorption tests of phosphorus to filter materials

a Media preparation

Super Sol (SS), Porous Alpha (PA) and Limestone (LS) were washed with distilled water to remove pollutants adhered to particles and any soluble materials which could dissolve during batch experiments, crushed and sieved through 0.212 mm – 1.4 mm and kept in the tight bottle glass

b Influential factors

This study was conducted four influential factor such as adsorbent dosage, pH, contact time and initial concentration

Adsorbent dosage: In order to conduct the effect of adsorbent dosage on P

adsorption of filter materials, various amount of filter materials was used from 1 – 5

g was added into 75mL solution of phosphorus (50 mgP.L-1) 24 hours for shaking time, 120 rpm for shaking speed, 25 oC for room temperature were the same as adsorption condition After sharking, the suspended solids were filtered using Qualitative Filter Paper, Grade 102, 15 ~ 20 𝜇 m The filtrated was measured phosphorus by using a UV-VIS spectrophotometer at a wavelength of 710nm All samples were triplicated (n=3)

pH: In order to investigated the effect of pH on P adsorption of filter material, pH

value ranging from 3 to 11 was adjusted and transferred in the flask containing 75

mL solution of phosphorus (50 mgP.L-1) 24 hours for shaking time, 120 rpm for shaking speed, 25 oC for room temperature were the same as adsorption condition

Adsorbent dosage was obtained from the above experiment After sharking, the suspended solids were filtered using Qualitative Filter Paper, Grade 102, 15 ~20

𝜇m The filtrated was measured phosphorus by using a UV-VIS spectrophotometer

at a wavelength of 710nm All samples were triplicated (n=3)

Contact time: In order to conduct the contact time on P adsorption of filter material,

the various time from 1 to 96 hours was conducted in the flask containing 75 mL solution of phosphorus (50 mgP.L-1) 24 hours for shaking time, 120 rpm for shaking speed, 25 oC for room temperature were the same as adsorption condition Adsorbent dosage and pH value were obtained from the above experiment After sharking, the suspended solids were filtered using Qualitative Filter Paper, Grade

102, 15 ~ 20 𝜇 m The filtrated was measured phosphorus by using a UV-VIS spectrophotometer at a wavelength of 710nm All samples were triplicated (n=3)

Initial concentration: In order to investigate the initial concentration of filter

concentration on P adsorption, the various initial concentration from 5 to 100 mg.L

-1 24 hours for shaking time, 120 rpm for shaking speed, 25 oC for room temperature were the same as adsorption condition Adsorbent dosage, pH value and contact time were obtained from the above experiment After sharking, the suspended solids were filtered using Qualitative Filter Paper, Grade 102, 15 ~20

𝜇m The filtrated was measured phosphorus by using a UV-VIS spectrophotometer

at a wavelength of 710nm All samples were triplicated (n=3)

c Isotherm study

The phosphorus concentration was varied in the range of 0 – 1000 mgP.L-1 The adsorption condition was obtained from influential factor The Langmuir and Freundlich isotherms are conducted to describe the equilibrium of adsorption systems The Langmuir and Freundlich adsorption isotherm were used to describe

the characteristics of phosphorus adsorption onto filter media as describe Table 2.1

Table 2.1 The Isotherm models using in batch studies Model Equation Linear form References

d Kinetic study

Kinetic study was conducted to understand the mechanisms including during adsorption process and provides useful information for large scale application (Letshwenyo and Sima, 2020) The adsorption kinetic experiments were studied a range of 1 – 96 hours in the flask containing 75 mL solution of phosphorus (50 mgP.L-1) The adsorption condition was obtained from influential factor In the present work, the adsorption rate was analysed based on two different models such

as pseudo-first-order and pseudo-second-order as following this equation:

Table 2.2 Kinetic models used in batch studies Model Equation Linear form References

where k1 and k2 are rate constants for pseudo-first-order (min-1) and order (g.mg-1.min-1), respectively; while qt and qe are the amount of phosphorus adsorbed (mg.g-1) at any time t and at equilibrium, respectively

pseudo-second-2.2.3 Wastewater treatment by Lab-scale Hybrid CWs

a Simulated wastewater

This study investigated the treatment performance of Hybrid CWs with synthetic anaerobically digested wastewater, simulating the anaerobically digested swine wastewater from a commercial pig farm in Bui Huy Hanh Pig Farm in Hai Duong Province The pig farm covered an area of 1220 m2 with 1400 pig heads It is estimated that approximately 80 m3.d-1 of wastewater was generated and discharged into the surrounding environment from anaerobically digester Kato et al., (2019) reported that anaerobically digested swine wastewater was characterized as flows: TSS 155 - 1600 mg.L-1, pH 6.99 – 7.72, BOD5 428 - 990 mg.L-1, COD 520 - 1856 mg.L-1, total nitrogen (TN) 590 - 713 mg.L-1, NH4+ -N 347 - 670 mg.L-1, total phosphorus (TP) 34.13 – 136 mg.L-1, PO43+-P 17.56 - 122 mg.L-1 In this study, synthetic anaerobically digested swine wastewater (ADSWW) was prepared by dissolving C6H12O6, NH4Cl and KH2PO4 in tap water The concentration of COD,

NH4+ -N, and PO43+-P in synthetic ADSWW were 680 - 1860 mg.L-1, 256 - 457 mg.L-1, and 34 - 82 mg.L-1, respectively; the pH was 6.04 – 6.75; and the DO

b Design of lab-scale Hybrid CWs systems

The lab-scale Hybrid CWs was located in the laboratory of Master’s Program in Environmental Engineering (MEE), VNU Vietnam Japan University The CW units were built of Cylindrical Transparent Acrylic Column Clear with the dimensions of

66 cm in height and 15 cm in diameter, respectively

Table 2.3 The layer of lab-scale Hybrid CWs Systems

Plant density

15 cm of coconut fiber (approximately

154 g coconut)

20 cm of super sol (10 – 20

mm in diameter)

Figure 2.6 Schematic diagram of experiment laboratory-scale hybrids constructed wetlands

Figure 2.7 Lab-scale Hybrid CWs

c Operational and monitoring conditions of Hybrid CWs

The lab-scale Hybrid CWs were operated in a continuous flow regime, the average flow rate of VF 2.6 (L.d-1) The hydraulic loading rate (HLR) of each reactor is 0.036 (m.d-1) for HF1, 0.034 (m.d-1) for HF2, 0.039 (m.d-1) for HF3, 0.038 (m.d-1) for HF4, respectively The hydraulic retention time (HRT) was 7 day for each of CWs This study was conducted from 15th May to 15th July, 2020

d Wastewater characteristic

Water samples were taken from the influent and effluent every 3 days There were 6 water samples including 1 synthetic ADSWW, 1 effluent of VF and 4 effluent of HF1 Gravel, HF2 FWG (PA), HF3 FWG (SS), and HF4 FWG (SS) + (CCF) In order to evaluate the removal efficiency of Hybrid CWs at VF, HF1, HF2, HF3, and HF4 such as pH, DO, COD, TP, PO43+, TN, NH4+, NO3- and NO2-

2.2.4 Filter materials and plants characteristic

a Preparing samples

In order to evaluate the nutrient removal from hybrid constructed wetlands The concentration of N and P was identified in plants and filter materials Plant samples were collected from 5 columns VF, HF1, HF2, HF3, and HF4 including leaf, stem and root The plants were washed with tap water to remove pollutants (Dibar et al., 2020) Then, the plants were air-dried and cut into various parts such as leaf, stem and root and weighed the fresh weight using a precision balance (MS3002TS/00, Mettler Toledo, China) Then the plant samples were dried at 70 oC in 48 hours by using mechanical convection oven (PR305220M, Thermo Scientific, USA) After being dried to constant weight, the plant samples were weighed the dried weight Finally, the dried plant samples were crushed and ground using mortar and sieved through 0.15 mm sieve and kept in plastics bag (Dibar et al., 2020)

Filter material samples were collected in each of layer from 5 columns such as VF, HF1, HF2, HF3, and HF4 Then filter material were washed with tap water to remove pollutants and dried at 105 oC in 30 min and then dried at 80 oC using the mechanical convection oven (PR305220M, Thermo Scientific, USA) (Liu et al., 2016) After being dried to constant weight, the filter material was weighed the dried weight using a precision balance (MS3002TS/00, Mettler Toledo, China) Finally, the dried filter materials were crushed and ground using mortar and sieved through 0.15 mm sieve and stored in plastics bag (Dibar et al., 2020)

b Plant analysis

Taken 0.5 g dried plant samples were mixed with 10 mL of mixture of

H2SO4:HClO4 (1:2 in volume), kept overnight and then digested in Kjeldahl Digestion Unit (DK6, Velp, EU) at 200 oC for 60 minutes and then up to 300 oC in

60 minutes The solution was kept in the room temperature (25 oC), made up to 100

mL, centrifuged and then filtered Finally, total phosphorus (TP) and total nitrogen (TN) in the dried plants were measured by following the Method 365.3, EPA and TCVN 6638 – 2000 (ISO 10048 – 1991), respectively

c Filter material analysis

Taken 0.5 g dried filter materials were mixed with 10 mL of mixture of

H2SO4:HClO4 (1:2 in volume), kept overnight and then digested in Kjeldahl Digestion Unit (DK6, Velp, EU) at 200 oC for 60 minutes and then up to 300 oC in

60 minutes The solution was kept in the room temperature (25 oC), made up to 100

mL, centrifuged and then filtered Finally, total phosphorus (TP) and total nitrogen (TN) in the dried filter materials were measured by following the Method 365.3, EPA and TCVN 6638 – 2000 (ISO 10048 – 1991), respectively

2.3 Analytical methods

2.3.1 Characterization of filter materials

a X-ray fluorescence (XRF)

X-ray fluorescence (XRF) is a method for the analysis of the chemical composition

of materials based on the recording of X-ray diffractometer emitted by that material due to interaction with incident radiation (Letshwenyo and Sima, 2020) It used to measure all the chemical elements from sodium to uranium in the periodic table of the elements

X-ray fluorescence spectrometer (XRF) JSX 1000s was performed at Key Laboratory of Advanced Materials for Green Growth, Vietnam National University

Figure 2.8 X-ray fluorescence spectrometer (XRF) JSX 1000s, USA

b X-ray diffractometer (XRD)

X-ray diffractometer (XRD) provides information on the composition and structure

of the material (Letshwenyo & Sima, 2020)