Evaluation the effectiveness of in sewer purification system and its application in vietnam condition

18 Figure 2.9 Results of BOD removal effectiveness of the system at Kim Lien Data provided by Sekisui Chemical Co.. 21 Figure 2.11 Results of BOD removal effectiveness of system at Coto

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY -

DUONG THU THUY

EVALUATION THE EFFECTIVENESS OF IN-SEWER PURIFICATION SYSTEM AND

ITS APPLICATION IN VIETNAM

CONDITION

MASTER'S THESIS

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

- -

DUONG THU THUY

EVALUATION THE EFFECTIVENESS OF IN-SEWER PURIFICATION SYSTEM AND

ITS APPLICATION IN VIETNAM

ACKNOWLEDGMENT

Foremost, I would like to express my sincere gratitude to my supervisor Associate Professor Hiroyasu Satoh for his support of my master thesis, for his patience, motivation, enthusiasm, and immense knowledge His guidance helped me in all the time of research and writing of this thesis

I would also like to thank the experts who were involved in the validation survey for this research project: Professor Jun Nakajima, Associate Professor Cao The Ha, Dr Nguyen An Hang and Dr Vu Ngoc Duy Without their passionate participation and input, the validation survey could not have been successfully conducted

I would also like to acknowledge Mr.Mastubara and Mr.Matsuzaka at Sekisui Chemical Co.,LTD and Mr.Nguyen Van Toan at VAST (Vietnam Academic of Science and Technology) for offering me the filed trips and useful materials They also shared to me their useful knowledge and research to help me improve my understanding in this research topic

Finally, I must express my very profound gratitude to my parents for providing me with unfailing support and continuous encouragement throughout my years of study and through the process of researching and writing this thesis This accomplishment would not have been possible without them

Sincerely thank

TABLE OF CONTENT

ACKNOWLEDGMENT i

TABLE OF CONTENT ii

LIST OF TABLES iv

LIST OF FIGURES v

LIST OF ABBREVIATIONS vii

INTRODUCTION 1

CHAPTER 1 STATE OF WATER ENVIRONMENT AND WASTEWATER MANAGEMANT IN VIETNAM 3

1.1 Characteristics of domestic wastewater 3

1.2 Impact of domestic wastewater on the environment 3

1.3 The status of water environment in Vietnam 4

1.3.1 Big city 4

1.3.2 Rural area 6

1.3.3 Coastal place 6

1.4 The status of wastewater management in Vietnam 7

1.4.1 The status of drainage infrastructure 7

1.4.2 Policy management 9

1.5 Status of domestic wastewater treatment in Vietnam 9

1.5.1 Current wastewater treatment technologies 10

CHAPTER 2 REVIEW ON IN-SEWER PURIFICATION TECHNOLOGY 11

2.1 In - sewer purification systems 11

2.2 In-sewer purification technology 12

2.3 Pilot studies on in-sewer purification 13

2.3.1 Basic characteristics of the pilot (3 case studies: Kim Lien, Phu Ly and Coto Island in Vietnam) 13

2.3.2 Outline of the results of pilot studies at Kim Lien, Coto Island and Phu Ly 20

2.4 Potential advantage of in-sewer purification 27

CHAPTER 3 LABORATORY SCALE STUDY (IN SUGANO, JAPAN) 28

3.1 Introduction 28

3.2 Materials and methods 29

3.2.1 Experimental setup 29

3.2.2 Sampling procedure 33

3.2.3 Water quality analyses 34

3.3 Results and discussion 34

3.3.1 BOD removal performance 34

3.3.2 NH4+ removal performance 36

3.3.3 Results of other parameters 37

3.3.4 Discussions 38

CHAPTER 4 CASE STUDY IN HANOI 39

4.1 Introduction 39

The reasons why in-sewer purification system should be applied for 4.1.1 Hanoi 40 4.2 Application principle of in-sewer system 40

4.2.1 Principle of choosing the suitable length of in-sewer purification pipe 42

4.2.2 Principle of choosing the suitable type of in-sewer purification pipe 42

4.2.3 No conflict principle with the future sewer systems 43

4.3 Case study in three districts: Tu Liem, Hoang Mai 44

4.3.1 My Dinh District: My Dinh I 44

4.3.2 Hoang Mai District: Linh Dam peninsula 49

CONCLUSION 52

REFERENCES 53

APPENDIX 1 Site visit to in-sewer purification system in Coto Island 55

1 Basic information of Coto Island 55

2 Status of water drainage and in-sewer purification system 56

3 Sampling and monitoring result of the field trip 57

APPENDIX 2 QCVN 14:2008/BTNMT 60

LIST OF TABLES

Table 2.1 Basic information of pilot studies in Vietnam, installed by Sekisui

Co.Ltd,Japan 14

Table 2.2 Flow conditions in the pilot study at Kim Lien 15

Table 2.3 Flow conditions in the pilot study at Phu Ly 17

Table 2.4 Flow conditions in the pilot study at Coto Island 19

Table 2.5 BOD removal rate of three in-sewer system 23

Table 2.6 BOD removal of Phu Ly pilot on 11th Jan, 2018 (Data provided by Sekisui Chemical Co Ltd.) 23

Table 2.7 SS, COD, T-N and T-P removal performance of pilot at 3 pilots (Data provided by Sekisui Chemical Co Ltd.) 26

Table 2.8 Removal efficiency of in-sewer system at three pilots 26

Table 3.1 Dimensions of the purification pipe at Sugano 29

Table 3.2 pH of influent and water in recirculation tank at Sugano pilot 33

Table 3.3 Method of analysis the water parameters 34

Table 3.4 BOD removal results of pilot at Sugano 34

Table 3.5 Comparison of structure of two kinds of pipe 35

Table 3.6 Ammonia removal results of pilot at Sugano 36

Table 3.7 Result of other water parameters 38

Table 4.1: Caption of diagrams of in-sewer purification systems 41

Table 4.2 Information of BOD removal by in-sewer purification in Zone 1 47

Table 4.3 Information of BOD removal by in-sewer purification in Zone 2 48

Table 4.4 Information of BOD removal by in-sewer purification in Linh Dam 50

Table 0.1 Water samples analysis results of in-sewer system at Coto Island on 28th March, 2018 58

Table 0.1 Value of K coefficient corresponding to type of service facilities, public facilities, apartment buildings 61

LIST OF FIGURES

Figure 1.1 BOD 5 concentration of some lakes, which are inner cities in Vietnam

period 2012-2016 5

Figure 1.2 Ammonia concentration of some rivers, channels cannels in Hanoi and Hochiminh city in period from 2012-2016 6

Figure 1.3 The status of wastewater management in Vietnam [9] 7

Figure 2.1 Pipe in conventional sewerage system 12

Figure 2.2 In-sewage treatment - Developed by Sekisui Co.Ltd, Japan 12

Figure 2.3 Schematic of the pilot plant at Kim Lien WWTP (re-draw by using data of Sekisui Co.Ltd,Japan) 15

Figure 2.4 Water temperature of in-sewer system at Kim Lien 16

Figure 2.5 Map of the purification system in Phu Ly 16

Figure 2.6 Water temperature of in-sewer system at Phu Ly 17

Figure 2.7 Map of the purification system in Coto 18

Figure 2.8 The road in Coto island where the system is underground 18

Figure 2.9 Results of BOD removal effectiveness of the system at Kim Lien (Data provided by Sekisui Chemical Co Ltd.) 20

Figure 2.10 Results of BOD removal effectiveness of system at Phu Ly (Data provided by Sekisui Chemical Co Ltd.) 21

Figure 2.11 Results of BOD removal effectiveness of system at Coto Island (from May – August 2017, data provided by Sekisui Chemical Co Ltd ) 22

Figure 2.12 Results of ammonia removal performance of pilot at Kim Lien (Data provided by Sekisui Chemical Co Ltd.) 24

Figure 2.13 Results of ammonia removal performance of pilot at Phu Ly (Data provided by Sekisui Chemical Co Ltd.) 25

Figure 2.14 Results of ammonia removal performance of pilot at Coto Island (Data provided by Sekisui Chemical Co Ltd.) 25

Figure 3.1 Field laboratory at Sugano (outside and inside) 28

Figure 3.4 Cooler box (left) and Auto-sampling system (right) 33

Figure 3.5 Ammonia removal performance of pilot at Sugano 37

Figure 4.1 Regular combined sewer system –pipe in Vietnam 41

Figure 4.2 Separate sewer system (in the future) 41

Figure 4.3 Individual in-sewer purification system 42

Figure 4.4 Public in – sewer purification system 42

Figure.4.5 Separated in-sewer purification system in the future 43

Figure.4.6 Case study area in My Dinh I 44

Figure 4.7 A channel along Nguyen Co Thach road in My Dinh I ward 44

Figure 4.8 Status of manholes in My Dinh I 45

Figure 4.9 The road is small to consider rebuild new drainage system 46

Figure 4.10 A concrete manholes in Zone 3 in My Dinh I 46

Figure 4.11Application of in-sewer system for Zone 1 47

Figure 4.12 Application of in-sewer system for Zone 2 48

Figure 4.13 Linh Dam peninsula – Hoang Mai District, Hanoi 49

Figure.4.14 Application of in-sewer system for Linh Dam peninsula 50

Figure 0.1 Equipment to measurement at Coto pilot 57

Figure 0.2 Samples collected at 4pm on 24th Jan (From left to right: (1) Raw water – (2) water after running inside pipe – (3) water after settling 59

LIST OF ABBREVIATIONS

BTNMT Ministry of Environment and Natural Resources ICOP Intermittent contact oxidation process

JICA Japan International Cooperation Agency

MDGs Millennium Development Goals

QCVN National technical regulation of Vietnam

SDGs Sustainable Development Goals

SNV Smart development works in Vietnam

INTRODUCTION

Vietnam is now striving for global integration in both economic and cultural activities, education, which are the global development trend, including the implementation of the Sustainable Development Goals (SDGs) 2030 According to the report of Vietnam Ministry of Planning and Investment in 2016, Vietnam has achieved many achievements after 15 years of implementing the Millennium

Development Goals (MDGs) (Country report, 2015), the program United Nations

organized before SDGs However, the objective of ensuring the sustainable environment is currently quite difficult and faces many challenges One of them is the reduction of environmental pollution caused by domestic wastewater

Being a developing country with a young economy and human resources, there are many challenges for Vietnam The population growth rate in Vietnam is quite high This puts pressure on the environment (including water environment) Increase in the generation of domestic wastewater overloads pollutants to existing drainage system in Vietnam that is still not modern and advanced Majority of the drainage and sewerage are the combined systems, which have been constructed in different development stages of the country, they are not consistent, synchronous with deteriorating facilities causing incapacity Rapid urbanization causes the uncontrolled wastewater volume, which directly pours into environment or the incapacity drainage systems without treatment; therefore, this is one of four main objectives to focus in Vietnam water field vision to 2030 (WRG, 2017)

Currently, Vietnam is striving to achieve 70% of urban wastewater treatment by

2030 (Bộ Xây dựng, 2011) In the context mentioned above, I conducted the present

study to evaluate the applicability of a new sewer pipeline technology, called sewer purification The technology, once realized, is expected to bring about the advantage of saving time on construction, saving energy for wastewater treatment acting as a preliminary treatment step before wastewater is transported into WWTPs (Wastewater treatment plants)

in-Here, I conducted following studies to evaluate the applicability of the in-sewer purification technology with the particular objectives below:

-To review the pilot studies on in-sewer purification technology conducted by Sekisui Chemical Co Ltd (Chapter 2)

-To examine the mechanisms of water quality improvement using a laboratory scale in-sewer purification system (Chapter 3)

-To evaluate the feasibility by a primitive sewer design study (Chapter 4)

CHAPTER 1 STATE OF WATER ENVIRONMENT AND WASTEWATER

MANAGEMANT IN VIETNAM

Domestic wastewater is the spent water originating from all aspects of human sanitary water usage It typically constitutes a combination of flows from the kitchen, bathroom and laundry, toilets, baths, kitchen sinks, garbage grinders, dishwashers, washing machines and water softeners Domestic wastewater, as the name implies, principally originates in residences and is also referred to as sanitary sewage As such, commercial, institutional and industrial establishments contribute

a domestic wastewater component to the sewer system resulting from human sanitary activity As it is derived from human activities, domestic wastewater has high levels of organic matter and nutrients

The amount of domestic wastewater depends on the population, the water supply standard and the characteristics of the drainage system The increase in population and the need to improve the quality of life has led to an increase in the amount of domestic wastewater generated in urban areas In urban centers, the amount of domestic wastewater is large because using combined drainage system In rural and suburban areas, due to lack of drainage system, wastewater is usually drained naturally into ponds, lake or drained by permeating the ground

According to the standard of daily-life water supply of Vietnam, the average water supply is about 100 - 125 liters/person based on the specific living standards of each residential area Of which, the daily-life wastewater is estimated to be about 80% of the supplied water volume (80 - 100 liters/person)

The main pollutants in domestic effluent are solid suspended solids (SS), biochemical oxygen demand (BOD5), nitrogen of ammonium salts (N-NH4+),

phosphate, chloride (Cl-) and total surface-active substances In addition, domestic wastewater contains inorganic components, microorganisms and other pathogenic microorganisms Environmental impacts of wastewater caused by contaminated components in wastewater

- COD, BOD: mineralization, stabilization of organic matter consumes a large amount and causes oxygen deficiency of the receiving source leading to ecological water environment

- Excessive pollution of anaerobic conditions may occur In the process of anaerobic digestion produces products such as H2S, NH3, CH4, etc make the water smell bad and reduce the pH of water

- SS (suspended solids): sedimentation at the receiving source, causing anaerobic conditions

- Temperature: The temperature of domestic wastewater usually does not affect the aquatic life of aquatic animals

- Pathogenic germs: causing waterborne diseases such as diarrhea, food poisoning, etc

- Ammonia, P: These are the macronutrients If the concentration in the water

is too high leading to eutrophication (the development of algal blooms, resulting in very low oxygen levels in the water at night causing choking and killing of organisms, During the day the oxygen content is very high due to the respiration of the algae

- Color: loss of beauty

- Grease: odor, preventing diffusion of oxygen on the surface

1.3.1 Big city

Surface water pollution of rivers, lakes, and canals in inner cities is still a major problem in most provinces and cities Most of the parameters for organic pollution

Vietnam QCVN 08-MT: 2015/BTNMT (B1) (will be showed in appendix) The main reason is that these areas have to receive untreated urban wastewater Especially Hanoi and Ho Chi Minh City, these cities have the highest level of pollution of rivers, lakes and canals (MONRE, 2016).

For lakes in the inner city, the main functions are water regulation, water treatment and urban landscapes function However, due to urban population development, some lakes have been encroached and deposited, these affected to the drainage and wastewater capacity There is no sewage collection system for the residential areas surrounding the lakes so municipal wastewater is discharged directly into the lake

In many cities, some lakes have the function as wastewater reservoirs with no circulation

The characteristics of surface water quality of some rivers in Vietnam are showed

Figure 1.1 and Figure 1.2 (Bộ Tài nguyên Môi trường, 2016)

Figure 1.1 BOD 5 concentration of some lakes, which are inner cities in Vietnam

period 2012-2016

Figure 1.2 Ammonia concentration of some rivers, channels cannels in Hanoi and

Hochiminh city in period from 2012-2016

1.3.2 Rural area

Most of the reservoirs, ponds and canals of rural areas in Vietnam have relatively good water quality Surface water in most areas can be used for irrigation purposes, many of which still meet the requirements for domestic water supply However, there is decreasing of surface water quality in river downstream areas where receiving the domestic water from residential areas of cities Aggregate impacts from agricultural development such as cultivation, livestock and industrial production, handicraft villages are also putting pressure on the rural environment

(Bộ Tài nguyên Môi trường, 2016)

1.3.3 Coastal place

Vietnam has about 130 coastal cities with 3,260 km of coastline, which belongs 28 provinces It means more than 50% of its population living along the coastline The sea environment in coastal areas is directly affected by socio-economic development such as seaport and tourism Between 70% and 80% of marine waste

originates in the country (Bộ Tài nguyên Môi trường, 2016) However, due to

organic matter and grease are also problems The problem of pollution by organic matter in coastal seawater has taken place in some coastal cities The content of monitoring parameters such as COD, NH4+ in the period 2011 - 2015 in some areas

is high above the level of QCVN 10-MT: 2015/BTNMT (the purpose of aquaculture and beach), especially the urban areas with seaports and crowed tourism

1.4 The status of wastewater management in Vietnam

1.4.1 The status of drainage infrastructure

The status of wastewater management in Vietnam is showed in Figure 1.3

Figure 1.3 The status of wastewater management in Vietnam (World Bank 2012)

Most of the domestic wastewater in Vietnamese cities flows through the septic tank before flowing into the public drainage system However, most of the wastewater is released into the environment such as ponds, lakes, and rivers Only a small fraction

of wastewater goes to the WWTPs Besides wastewater, sludge is also an important target that needs to be treated Sludge in conventional septic tanks is not routinely

drawn because the households manage these septic tanks Households generally do not pay attention to the discharge of sludge until there is a blockage or fullness

Sewer systems

Urban sewer systems have been built over different periods so they are not complete and synchronous Combined drainage system is the main method to collect domestic wastewater in Vietnam This method continues to be used in ongoing drainage projects The reason is this system is cheaper and easier to implement because it can be done with fewer sewers and less construction affect on human life

At present, there are about 60% of households are connected to public drainage systems, which are combined drainage systems The use of combined drainage systems is one of the major challenges as it often leads to overload for wastewater treatment plants and polluted surface water (World Bank, 2012)

Septic tank and Biogas system (On-site treatment)

On-site sanitation facilities such as septic tanks are still the main wastewater treatment facility in Vietnam, even when households are connected to the public sewerage system The drainage system in Buon Ma Thuot city, Da Lat city, and other new urban areas, as designed, households, which are connected to separate sewerage systems, will not have septic tanks Wastewater after flowing through septic tank has the decrease of BOD concentration about 30 - 40% (World Bank, 2012)

The other on-site wastewater treatment system is biogas system At the household level, there are now about 500,000 biogas decayers However, most of these tunnels are small (less than 10m3) built by households According to a report of SNV Vietnam (Smart development works in Vietnam), particularly for the “Biogas Program for the Animal Husbandry Sector” in Vietnam, funded by the Dutch government, 15,688 small scale

Wastewater treatment plants

According to the report of Vietnam Ministry of Construction, by the end of 2016, Vietnam has 802 urban areas, of which two are urban with an average urbanization rate of 36.6% Most of urban in Vietnam do not have centralized wastewater treatment plants Many urban centers are currently constructing or no domestic wastewater treatment plants therefore wastewater is pre-treated through septic tanks

or biogas system and then drains and discharged directly into the environment There are currently 37 urban WWTPs with a total capacity of 890,000m3/day The

processing rate is around 12-13% (Bộ Xây dựng, 1999)

1.4.2 Policy management

Vietnam's regulation for urban wastewater discharged into the environment

Currently, the management of the quality of wastewater discharged into the environment is carried out according to the environmental law of Vietnam In particular, the standard of domestic wastewater is based on the regulations of the Ministry of Environment and Natural Resources with the standard QCVN

1.5 Status of domestic wastewater treatment in Vietnam

The wastewater treatment industry in Vietnam is relatively young with the first wastewater treatment plant operated in 2005 The situation of domestic wastewater treatment in recent years has made positive changes, thus contributing to limiting the increase of environmental pollution in general and the water environment in particular However, the rate of wastewater treatment is still low (it is about 12-13%

as mentioned in the section 2.4.1) Although the number of urban water supply projects has increased over the years, however, this figure is very small compared to the actual requirements to be treated

According to figures from the Ministry of Construction in 2015, 52 urban areas undergoing ODA projects for drainage and wastewater treatment have been

developed with a total of around 77 WWTPs systems with a total designed capacity

of about 2,400,000m3/day (World Bank, 2012)

Currently, 37 WWTPs are standardized to be built in urban areas of grade III or higher that are already in operation However, the construction of the wastewater treatment plant has been completed, but there is no synchronized wastewater collection network As a result, some wastewater plants are not operating at full capacity due to inadequate input water

1.5.1 Current wastewater treatment technologies

Currently, wastewater treatment technologies in Vietnam are mainly variants of secondary processing technology with activated sludge, such as Conventional activated sludge (CAS) technology, Anaerobic – anoxic – oxic(A2O), oxidative dewatering (OD) and Sequencing batch reactor treatment (SBR, ASBR) Sludge treatment technology is widely applied in JICA-financed plants such as Kim Lien, Truc Bach, Thang Long (in Hanoi) and Binh Hung (in Ho Chi Minh City) Activated sludge treatment technology in ASBR, which has been widely applied in recent years In the next five years, at least 10 new urban wastewater treatment plants will adopt this technology Some of the advantages of SBR technology, such

as small area requirements and the ability to remove nutrients, make this technology suitable for urban conditions and areas where nutrient management is critical

CHAPTER 2 REVIEW ON IN-SEWER PURIFICATION TECHNOLOGY

Sewer systems play an integral role to transport sewage to WWTPs During the transportation of wastewater through sewer pipes, pollutants in sewage go through chemical or biological processes Biological process involves the activities of microorganism living in sewage and on the inner wall of sewer pipe If the retention time is long enough, the quality of water will be improved, as significant part of organic pollutants can be removed by microbial activities The present study focused to explore the activities of microorganisms live in sewer pipes to enhance water quality improvement in the sewer pipe A number of related studies have already been conducted to evaluate the activity of microorganisms in the pipe Yet, the studies to utilize microbial activity to improve water quality in sewer pipe are still scares

The first study on biological process in sewer pipe was conducted by Pomeroy and Parkhurst (1972) Since then, a number of studies have shown the role of the biofilm attached on the inner wall of sewer pipe in conversion of organic pollutants

in wastewater Even in a conventional drainage system, thanks to microorganisms

on the walls, water quality is improved to some extent Huisman et al (2004) stated that there was a decrease of at least 30% of COD in wastewater in a full-scale gravity sewer

Recent studies are making new progress to improve the efficiency of water quality improvement by introducing biomass-attached media Tanji et al (2006) showed that the larger surface area of exposure, the higher the self-purification effect, in which the grain and porous surface have the highest cleaning efficiency Shoji et al (2016) reported a study on a novel sewer pipe with double-decker structure with sponge media installed in the lower layer and demonstrated a promising potential of in-sewer purification The study was conducted with Sekisui Chemical Co Ltd.,

Japan as a collaborator In the following section, studies conducted with the decker pipe are reviewed

Figure 2.1 illustrates a conventional sewer, being widely used today to perform

wastewater transport Figure 2.2 shows the sectional views of the novel sewer pipe

developed by Sekisui Chemical Co Ltd The novel sewer pipe secures the sewage transport function on the upper layer, while the lower layer is intended to enhance purification of wastewater The pipe itself has a diameter of 250mm and is made of polyvinyl chloride (PVC) In the lower deck, sponge made of polyethylene media is fixed to provide stable habitat for microorganism As the sponge media can retain high biomass, the microbial density of the pipeline is increased and biochemical processes are promoted

Figure 2.1 Pipe in

conventional sewerage system

Figure 2.2 In-sewage treatment - Developed

by Sekisui Co.Ltd, Japan

The mechanisms of the pollutant removal by the novel pipe are explained as follows With high flow, sewage introduced to the upper layer spills to the lower layer The sponge media with significant microbial density in the lower layer will

be submerged in wastewater Microorganisms in the sponge can access and absorb organic pollutants in sewage, and as a result, organic pollutants in sewage can be removed from sewage The sponge may also physically entrap some part of particulate organic pollutants Up to this point, the organic pollutant removed from sewage has not been oxidized but remains on the sponge: the organic pollutant needs to be oxidized Oxygen required for this purpose is supplied in two ways One is from dissolved oxygen in sewage In this regard, the double-decker structure

is beneficial to enhance surface aeration Another mechanism is the direct exposure

of sponge media to air when the water flow is low That is, when water flow is low, all sewage can run on the upper layer, thus sponge media is exposed to the air in the pipe

2.3.1 Basic characteristics of the pilot (3 case studies: Kim Lien, Phu Ly and Coto Island in Vietnam)

Sekisui Chemical Co.Ltd conducted a series of pilot studies of in-sewer treatment from 2017 to 2018 in Vietnam under the sponsorship of JICA The pilot studies are grouped into two: the surface experiments with short pipes extending from 32 to 48

m with recirculation of, and underground experiments extending a couple hundreds

of meters

Surface pilot studies were conducted at three wastewater treatment plants: Kim Lien

in Hanoi, Qui Luu in Phu Ly, and Ha Khanh in Ha Long Underground pilot studies were conducted in Phu Ly City, and Coto Island, Quang Ninh Province

Here, I report three of their studies: surface study in Kim Lien, and the two underground studies Some basic information of the pilots installed at Kim Lien, Coto Island and Phu Ly are shown in Table 2.1

Table 2.1 Basic information of pilot studies in Vietnam, installed by Sekisui

Co.Ltd,Japan

These systems were installed in different locations in Vietnam in order to monitor the stability of the system and assess their applicability for wastewater conditions in Vietnam The detailed information of the in-sewer systems and their effectiveness are reviewed in the following sections

Pilot in Kim Lien

Figure 2.3 shows the schematic of the pilot plant at Kim Lien WWTP in Hanoi

Input water was pumped to the received tank (1m3 volume) from wastewater collection tank of the WWTP Wastewater run through the purification pipe was collected to a circulation tank (1.8m3 volume) then a part of it was recycled to the system before flowing to the settling tank (2.54m3 volume) After settling, treated water overflew into the final settling tank then flew back to the Kim Lien WWTP The sludge was removed manually by pump

Island Underground 290 3/2017 – 3/2018 Combined sewer from households

Figure 2.3 Schematic of the pilot plant at Kim Lien WWTP (re-draw by using data

of Sekisui Co.Ltd,Japan)

Flow conditions of the inflow and the recirculation pumps were as shown in Table 2.2 The pump was operated intermittently The influent load was initially set higher, and then lowered, as in this pilot study influent strength was higher than

expected Figure 2.4 shows water temperature The temperature was as high as almost 30°C during June to September, then it gradually lowered to around 20°C by December

Table 2.2 Flow conditions in the pilot study at Kim Lien

Aug.2 – Aug.25 1.2 7.9 60 30 146 Aug.25 - Sep.22 0.6 7.6 60 30 131 Sep.22 - Oct.20 0.8 7.8 60 20 155 Oct.20 - Nov.11 0.6 7.5 60 20 146 Nov.11 - Dec.15 0.4 9.2 60 20 173 Dec.15 - Dec 29 0.4 9.5 60 20 178 Dec 29 - Feb.9 0.4 9.5 60 60 119

Figure 2.4 Water temperature of in-sewer system at Kim Lien

Pilot in Phu Ly

Figure 2.5 illustrates the location of the purification system in Phu Ly It receives

domestic wastewater from a small residential community who live near Day River The system is installed underground of Ngo Quyen street The total length of the pipeline is about 474m with 15 manholes Structure of system in Phu Ly is similar

to the system of Coto Island Water after settling was discharged to Day River

The condition of flow of in-sewer system at Phu Ly is showed in Table 2.3 The pump was operated intermittently The pumps were control automatically base on the level of water in the collecting tanks Therefore, daily flow varied at different dates but overall, daily flow remained at 15 - 26 m3 Figure 2.6 shows water temperature (Data provided by Sekisui Chemicals Co.Ltd) In general, the wastewater temperature in the system during the survey ranged from 23oC to 31oC There were temperature differences between rainy and dry seasons The temperature was mostly constant when water flowed throughout the system

Table 2.3 Flow conditions in the pilot study at Phu Ly

Date

Flow rate

11/2 26.0 11/16 20.1 11/30 26.2 12/14 15.0 12/28 22.7 1/11 353.8 2/8 19.2

Figure 2.6 Water temperature of in-sewer system at Phu Ly

Pilot in Coto Island

Figure 2.7 and Figure 2.8 illustrate the location of purification system at Coto in

Vietnam This system is put underground of the pedestrian with 8 manholes, which

is along the coastal The total length of pipe is 290m The settling tank (4.7m3 of volume) near Coto wharves has the depth of 2.5m from the ground to the bottom of the tank There is a pump located in the 4th manhole The slope is 0.004 (m/m) for each segment and the average slope including steps is around 0.006 (m/m) The steps here mentioned are to introduce water from lower layer of the upstream segment to the upper layer of the downstream segment

Figure 2.7 Map of the purification system in Coto

The influent was domestic wastewater intercepted from an existing sewer Influent was pumped from the collecting tank then supplied to the purification system Wastewater goes through the pipe by gravity, lifted by the pump at the 4th manhole, again goes by gravity, pumped at the last manhole into the settling tank at the end of the pipeline, and finally discharged into the sea The sludge in the settling tank was removed manually by using a pump

The condition of flow from May 2017 to March 2018 at Coto Island is showed in Table 2.4 (Data provided by Sekisui Chemical Co.Ltd.) Pumps are installed for automatic pumping base on the level of water in collecting tank and receiving tank Therefore, daily flows were varying at different dates

Table 2.4 Flow conditions in the pilot study at Coto Island

Date (MM/DD)

Daily flow

5/23 53.3 5/30 63.5 6/13 33.3 7/3 252 7/4 20.9 7/4 (8:50) 39.2 7/4 (16:05) 46.2 7/18 45.1 8/1 37.6 8/28 29.6 11/8 75.0 11/9 63.5 11/23 39.6 12/6 27.0 12/21 30.9 1/24 24.0 2/6 25.9 2/7 26.8 3/1 35.6 3/12 44.6 3/13 58.2

2.3.2 Outline of the results of pilot studies at Kim Lien, Coto Island and Phu Ly

a BOD removal performance

Kim Lien: Figure 2.9 shows the BOD removal effectiveness of the system at Kim

Lien It ranged from 40 - 170mg/L, with an average of 142 mg/L Concentration of

BOD after settling was about 50 -70mg/L with an average of 58.6 mg/L The BOD

removal rate was about 52 %

Figure 2.9 Results of BOD removal effectiveness of the system at Kim Lien (Data

provided by Sekisui Chemical Co Ltd.)

Phu Ly: Figure 2.10 is the results of BOD removal effectiveness of system at Phu

Ly Regardless of the inflow BOD concentration, which sometimes reached higher

than 100mg/L, the BOD concentration of the effluent was mostly lower than 30

mg/L, satisfying the effluent standards of QCVN Vietnam Even when the flow rate

was high, the BOD removal efficiency remained quite high At times, the BOD

concentration of effluent was high at nearly 120 mg/L but after flowing through the

system, this value dropped to below 30 mg/L The data on 11th Nov 2017 at 9:30 am

showed an irregular increase at the end of the pipeline: the input BOD level was

the water quality is strongly affected by the discharge pattern of sewage by the local community, and the water quality fluctuation at the same location can be high Secondly, accumulated solids in the pipe may be detached in the last section and made BOD concentration increase

Figure 2.10 Results of BOD removal effectiveness of system at Phu Ly (Data

provided by Sekisui Chemical Co Ltd.)

Coto Island: Figure 2.11 illustrates the results of BOD removal effectiveness of

system at Coto Island during the season when higher influent BOD concentration was observed BOD concentration was high during the period from May to August (tourism season in Vietnam) Most of data showed the amount of BOD in this period is more than 150 mg/L Concentration of BOD after settling were around100 mg/L and average BOD removal rate reach about 54%

Figure 2.11 Results of BOD removal effectiveness of system at Coto Island (from

May – August 2017, data provided by Sekisui Chemical Co Ltd )

Conclusions: In general, the BOD removals of three pilot systems were effective

In the case of in-sewer purification, Sekisui has been using the mass of BOD removed per a unit length of pipe per a unit time as the key parameter showing the BOD removal efficiency In this thesis, I tentatively name this parameter “length-based removal rate (LBR) of BOD” The mass of BOD loaded to the system within

a day (MBOD,in [gBOD/d]) is calculated by multiplying the concentration of influent BOD by the inflow volume within a day Similarly, the mass of BOD discharged

from the system as effluent within a day (MBOD,eff [gBOD/d]) is calculated by multiplying the concentration of effluent BOD by the effluent volume (which is essentially the same as influent volume) within a day When the length of the pipe

in the system is L(m), LBR of BOD is calculated as follows

(Equation 1) Table 2.5 shows the removal of BOD in % and LBR in g/m/d in the three pilot studies All three systems had the BOD removal of more than 50% The removal

Sekisui initially expected before the pilot study The removal of BOD in % of Phu

Ly got the highest value but LBR in g/m/D was low The reason for the lower LBR can be attributed to the low flow rate of influent

Table 2.5 BOD removal rate of three in-sewer system

BOD % 56 63 54

g/m/day 18.7 2.6 12.9 Flow rate of Phu Ly pilot ranged mostly within 15 – 26 m3/day except 11th Jan On this day, the flow rate was 353 m3/day and data of BOD removal were recorded on Table 2.6 shows that the higher amount of BOD of influent, the higher value of LBR On this day at 9:35 am, BOD concentration was the highest at 176.5 so the LBR was 94 g/m/day BOD This shows that the potential for BOD removal in the system is very high Assuming BOD-capital in Vietnam is 45g/cap/day and the desired treatment efficiency is 50% of BOD, this system can treat wastewater of

1980 people This value is calculated as follows:

Number of people = LBR × Length of pipe × (100%/50%) / 45

(Equation 2) Table 2.6 BOD removal of Phu Ly pilot on 11th Jan, 2018 (Data provided by Sekisui

LBR (g/m/D)

11-Jan

9:35 176.5 52.3 70% 94 13:45 54.1 18.7 65% 26 16:00 16.9 8.6 49% 6.3

The results from this will be used for Chapter 5 on the theoretical calculation of sewer system application for Vietnam Because of this result, it is possible to predict the minimum length of the self-purification system needed to install based on the amount population

in-b NH 4 -N removal performance

Kim Lien pilot: Figure 12 shows the results of ammonia removal performance of pilot at Kim Lien The NH4-N concentration of the influent was rather high, ranging from 30 mgN/L to 65 mgN/L In general, the amount of NH4 removed was not much in the period from August to November In the period from November to December, NH4 removal efficiency of the system was the most effective

Figure 2.12 Results of ammonia removal performance of pilot at Kim Lien (Data

provided by Sekisui Chemical Co Ltd.)

Phu Ly pilot: Figure 2.13 shows the reduction of NH4-N concentration of domestic water after treatment by in-sewer purification pilot at Phu Ly In general, the NH4-N concentrations of influent flow were not high Most of samples had the amount of

NH4-N from 20 to 55 mg/L There was no significant change in NH4-N concentration in influent and after settling However, the data of December showed the high NH4-N removal efficiency Partially, on 14th Dec NH4-N concentration decreased from 50mg/L to about 35mg/L and on 28th Dec this value decreased dramatically from about 75mg/L to 40mg/L

Figure 2.13 Results of ammonia removal performance of pilot at Phu Ly (Data

provided by Sekisui Chemical Co Ltd.)

Coto Island: Figure 2.14 shows the concentration of NH4-N observed at Coto island Compared to the other two pilots, the NH4-N concentration of the wastewater supplied for this system was significantly higher The highest concentration was up to about 140 mg/L The average removal rate for influent and

effluent comparisons was only 14-15%

Figure 2.14 Results of ammonia removal performance of pilot at Coto Island (Data

provided by Sekisui Chemical Co Ltd.)

c Results of the other water parameters:

The results of SS, COD, T-N and T-P removal performance by in-sewer system at

Kim Lien, Phu Ly and Coto island are showed in Table 2.7 and Table 2.8

Table 2.7 SS, COD, T-N and T-P removal performance of pilot at 3 pilots (Data

provided by Sekisui Chemical Co Ltd.)

Aver 64 46 37 348 213 197 77.6 66.5 67.6 5.7 4.6 4.0

Inf: influent, Eff: effluent, AS: after settling of the effluent

Aver: average, Min: Minimum, Max: Maximum

Table 2.8 Removal efficiency of in-sewer system at three pilots

Removal Efficiency