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

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 Hanoi, 2018 VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY  DUONG THU THUY EVALUATION THE EFFECTIVENESS OF IN-SEWER PURIFICATION SYSTEM AND ITS APPLICATION IN VIETNAM CONDITION MAJOR: ENVIRONMENTAL ENGINEERING SUPERVISORS: Assoc Prof HIROYASU SATOH Assoc Prof TRAN THI VIET NGA Hanoi, 2018 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 i TABLE OF CONTENT ACKNOWLEDGMENT i TABLE OF CONTENT ii LIST OF TABLES iv LIST OF FIGURES .v LIST OF ABBREVIATIONS vii INTRODUCTION CHAPTER STATE OF WATER ENVIRONMENT AND WASTEWATER MANAGEMANT IN VIETNAM 1.1 Characteristics of domestic wastewater 1.2 Impact of domestic wastewater on the environment .3 1.3 The status of water environment in Vietnam 1.3.1 Big city 1.3.2 Rural area .6 1.3.3 Coastal place 1.4 The status of wastewater management in Vietnam 1.4.1 The status of drainage infrastructure 1.4.2 Policy management 1.5 Status of domestic wastewater treatment in Vietnam 1.5.1 Current wastewater treatment technologies .10 CHAPTER 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 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 ii 3.3.1 3.3.2 3.3.3 3.3.4 BOD removal performance 34 NH4+ removal performance 36 Results of other parameters 37 Discussions 38 CHAPTER CASE STUDY IN HANOI 39 4.1 Introduction 39 4.1.1 The reasons why in-sewer purification system should be applied for 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 Site visit to in-sewer purification system in Coto Island .55 Basic information of Coto Island .55 Status of water drainage and in-sewer purification system .56 Sampling and monitoring result of the field trip 57 APPENDIX QCVN 14:2008/BTNMT .60 iii 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 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 47 Table 4.3 Information of BOD removal by in-sewer purification in Zone 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 iv LIST OF FIGURES Figure 1.1 BOD5 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 Figure 1.3 The status of wastewater management in Vietnam[9] 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 3.2 Diagram of purification system at Sugano pilot 30 Figure 3.3: List of material and equipment of experiment in Sugano 31 v 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 in My Dinh I 46 Figure 4.11Application of in-sewer system for Zone 47 Figure 4.12 Application of in-sewer system for Zone 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 vi 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 vii 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 insewer 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) Figure 4.12 Application of in-sewer system for Zone Table 4.3 Information of BOD removal by in-sewer purification in Zone A C D E Kind of No system Number of pipe Number of house Total of pipe length (m) How to calculate Count on the map Count on the map Calculate on Google map D*45*5 E*15.8 H/F 58 58 464 13050 7331 56% 109 752 24525 24 157 5400 16 114 3600 38 265 8550 31 216 6975 Average BOD removal rate (%) 11881 2480 1801 4187 3412 48% 46% 50% 49% 49% 51% B Individ ual system Public system Yellow Brown Blue Green 48 F G H Total Total BOD BOD BOD removal loading removal rate rate (g/day) (%) (g/day) In general, although the calculation is only assumed, the results show that Zone achieve the goal of treating 50% of BOD in domestic wastewater with the assumptions given in this report Meanwhile, in Zone 1, the removal efficiency of BOD was 48% It can be seen that if there is only one type of in-sewer purification pipe, in the case of Zone 1, was a public system, consideration of population density is necessary If space for public pipes is not enough to eliminate the desired BOD, the combination of two types of piping is necessary Some households will use individual type to reduce the organic loading on the public in-sewer purification system 4.3.2 Hoang Mai District: Linh Dam peninsula Linh Dam peninsular is one of the largest peninsulas in Hanoi It is the first modern urban area to be established over a decade ago This peninsula has an area of 200 and is surrounded by Linh Dam Lake with over 70ha of surface area Figure 4.13 Linh Dam peninsula – Hoang Mai District, Hanoi In this area, as well as other areas in Hanoi, the drainage system is combined system The principle of applying the in-sewer purification system is the same as that applied to the My Dinh I in the previous section However, I am merely 49 designing a system based on theory There is no factual data on the status of drainage facilities such as in the residential area in My Dinh I The calculated results are shown in Figure.4.14 and Table 4.4 Figure.4.14 Application of in-sewer system for Linh Dam peninsula Table 4.4 Information of BOD removal by in-sewer purification in Linh Dam A B No Kind of system How to calculate Individ ual system Public system Yellow Brown Blue C D E Number of house Total of pipe length (m) Count on the map Count on the map Calculat e on Google map 39 39 1 Number of pipe G H Total BOD removal (g/day) BOD removal rate (%) D*45*5 E*15.8 H/F 312 8775 4930 56% 122 546 27450 14805 57% 10 19 88 94 129 2250 2025 4275 1390 1485 2038 62% 73% 48% 50 F Total BOD loading rate (g/day) Green Red Purple 37 235 8325 24 168 5400 23 223 5175 Average BOD removal rate (%) 3713 2654 3523 45% 49% 68% 57% Potential BOD removal rate is quite high at about 57% of average value Population density is sparse compared to My Dinh I area, so the space for traffic is quite comfortable Therefore, the installation of new tubes is feasible for this peninsula The high buildings in this area are not suitable to use this system because the population in each building is crowded In my opinion, setting a site-treatment system for big building is better 51 CONCLUSION From this study, following results were obtained The in-sewer system is effective in treating organic pollution in domestic wastewater The system can eliminate at least 50% BOD, as has been demonstrated in Chapter and Chapter experimentally, and in Chapter with a primitive sewer design study 
However, it seems that the efficiency of nutrient treatment of this technology was not high: polishing treatment would be needed to remove nutrients, depending on the discharge regulation It should be studied in the future to achieve higher efficiency including nutrients removal Thanks to less power consumption, simple installation and maintenance, this technology will become a promising technology in the future to reduce the load on centralized wastewater treatment systems in the future.
Finally, the application of this system in wastewater drainage situation of Vietnam is very suitable Applying this system is expected to solve the surface water pollution issues in urban areas in short-term with without conflicting with Vietnam government planning in improving the system of wastewater collection and treatment in the future 52 REFERENCES Vietnamese 2030 WRG (2017), Khuôn kh kinh t v nư c ngành nư c nh gi c c th ch th c c a Bộ Tài nguyên Môi trường (2016), Báo cáo trạng môi trường Quốc gia (chuyên đề 1: Môi trường đô thị chuyên đề 2: Môi trường nơng thơn) Bộ Xây Dựng (1999), Định hướng nước đô thị đến năm 2020 Bộ Xây Dựng (2011), Quy ho ch chung x y dựng th nh n n n m 2050 ô Hà Nội n n m 2030 t m Country report (2015) 15 years achieving the Vietnam Millennium Development Goals QĐ 1929, 1930/QĐ-TTg ngày 20/11/2009, Định hư ng phát tri n cấp, tho t nư c ô thị Khu công nghiệp (KCN) Việt Nam n n m 2025, t m nh n n n m 2050 Tổng cục du lịch tỉnh Quảng Ninh (2016), Cô Tơ (Quảng Ninh) lộ trình phát tri n thành ô thị sinh thái bi n Tổng cục thống kê TP.Hà Nội (2018), Báo cáo: năm 2018 nh h nh inh tế - xã h i tháng M t World Bank (2012), Đ nh gi ho t ộng quản lý nư c thải ô thị t i Việt Nam English Huisman J L., Weber N and Gujer W (2004) Reaeration in sewers Water Res., 38, 1089-1110 Joshua N Edokpayi, John O Odiyo and Olatunde S Durowoju (2017), Impact of Wastewater on Surface Water Quality in Developing Countries: A Case Study of South Africa Water Quality, Chapter18, 402 -416 Koch C M and Zandi J (1973) Use of pipelines as aerobic biological reactors J Water Pollut Control Fed., 45, 2537-2548 Nielsen P H., Raunkjær K., Norsker N H., Jensen N A and Hvitved-Jacobsen T 53 (1992) Transformation of wastewater in sewer systems – a review Water Sci Technol., 25(6), 17-31 Pomeroy R D and Parkhurst J D (1972) Self-purification in sewers Proc 6th Int Conf on Water Pollut Res., Jerusalem, Israel, June 18-23, 1-16 Shoji T., Matsubara Y., Tamaki S., Matsuzaka K., Satoh H., Mino T (2015) Insewer Treatment System of Enhancing Self-Purification: Performance and Oxygen Balance in Pilot Tests Journal of Water and Environment Technology, 13(6), 427439 Suffolk County Department of Public Works and In-Pipe Technology Company, Report of Sewer Collection System Bio-augmentation Reduces Energy Use in WWTPs Tanji Y., Sakai R., Miyanaga K and Unno H (2006) Estimation of the selfpurification capacity of biofilm formed in domestic sewer pipes Biochem Eng J., 31, 96-101 54 APPENDIX Site visit to in-sewer purification system in Coto Island I visited Coto Island in January and March 2017 to observe the pilot system installed there This fieldtrip was conducted to observe one of the in-sewer systems installed in Vietnam by myself and to carry out field sampling to measure the quality of wastewater after treated by in-sewer system The parameters measured were pH, DO, ORP, temperature and COD Besides, I surveyed the natural and social characteristics of Coto Island to assess the suitability of the system for coastal areas The basic information and analysis results are shown below Basic information of Coto Island Location Coto Island is located at coordinates 20°10 'to 21°15' north latitude and 107°35 'to 108°20' east longitude 60 nautical miles from mainland Coto is bordered by the coastal areas of Mong Cai and Quang Ha Especially in the east, it is bordered by international sea area and further by the sea area of Hainan Island, China Natural feature Coto Island has a natural land area of 4,179 ha, a fishing area of over 300 km2 and the forest area of is 2,200 Coto Island has hilly terrain The middle areas of this island are high and surrounded by low hills and narrow fields, beaches and small bays Soil is mainly phelarite on sandstone Coto does not have many rivers and streams so the surface water reserve is not much Groundwater here has abundant reserves and good quality Flora and fauna on this island are very diverse, which is characteristic of the tropical forest ecosystem Economic and social features The population of Coto Island is approximate 6,000 people (T ng cục du lịch Quảng Ninh, 2016) Until now, fisheries, agriculture and tourism are the three key economic sectors of this island Of which, fishery and seafood processing accounted 55 for the highest proportion of GDP of the island However, according to statistics of Quang Ninh Tourism department, the tourism is growing rapidly with the average number of tourists being about 300,000 visitors every year (T ng cục du lịch Quảng Ninh, 2016) Therefore, the future direction of economic development is focused on tourism and services Status of water drainage and in-sewer purification system Coto Island has no wastewater treatment plant The drainage system is a combined system and wastewater is discharged into the environment or ocean with stormwater through the drainage system This causes the water environment of this island become polluted In general, the drainage system in this island requires improvement Many of its pipelines need improvement to meet the drainage of island As mentioned above, Quang Ninh provincial authorities have a strategy to develop the tourism industry for Coto in the future The number of tourists coming to the island increases year by year, especially in the summer This means the amount of domestic wastewater, which is now discharged into the ocean, also increases This really puts pressure on the capacity of the natural environment Increasing pollutant load in the context of current uncompleted drainage system will be a big issue for local authorities to meet the goals of sustainable development In order to meet the current demand of domestic wastewater treatment, the in-sewer purification system was introduced to the local government with its advantages in installation and maintenance Therefore, this system was installed in March 2017 (by Sekisui Chemical Co Ltd and with financial support by JICA) to evaluate the feasibility of system for Coto Island The result of the pilot study of the system was described in the previous section In the following section, I report the sampling and the water quality monitoring results done by myself 56 Sampling and monitoring result of the field trip Sampling Samples were collected times The first time was at 9:40 am on 28th March,2018 The other was at 2:40 pm on the same date In each timing, three kinds of samples were collected: influent sample, effluent sample and after settling sample The parameters measured were pH, DO, ORP, temperature and COD ORP and temperature of samples were measured by using ORP meter (Model RM-20P TOA DKK) DO was estimated by a DO meter (Model: DO-24P, TOA DKK) pH was measured using a pH meter, CODCr was measured by means of a commercially available kit (COD HR, Hach, CO, USA) The equipment, which were used for this fieldtrip, are showed in picture (a) (b) and (c) of Figure 0.1 (a) Water collecting equipment (b) DO, ORP and pH meters (c) COD measurement HACH kit Figure 0.1 Equipment to measurement at Coto pilot 57 Sample analysis results: The samples were taken twice on March 28 Due to the inadequate condition, water samples can only be measured for pH, ORP, temperature, DO and COD (results is showed in Table 0.1) The results of this field trip show some of the following: First, the temperature of water was around 24o C pH values ranged from 7.7 to 8.3 The DO concentration in wastewater increases after flowing through the system COD concentrations of these samples in this time were low The COD removal rate when calculated in % by taking COD value of after settling sample divided by that of influent was 22% This value is lower approximately by twice compare with data mentioned in the previous section Table 0.1 Water samples analysis results of in-sewer system at Coto Island on 28th March, 2018 Time 9:40 AM 2:40 PM Sample pH Temp Influent Effluent After settling Influent Effluent After settling 8.33 7.74 7.95 8.25 7.94 8.03 23.8 24.1 23.9 24.3 24.4 24.7 DO (mg/L) 0.03 0.52 2.87 0.76 0.85 1.94 ORP -256 -187 -185 -244 -182 -156 COD (mg/L) 312 270 236 298 256 240 In addition, the physical characteristics of wastewater such as color and turbidity were observed and the results are shown in Figure 0.2 The samples were taken in the afternoon on 24th Jan 2018 with beaker number was influent sample, beaker number was effluent sample and beaker number was after settling sample Based on the color change of each 1-3 water samples, it can be seen that the water quality after the treatment was significantly improved 58 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 Color (From to 3): Water turned from light black to light yellow Turbidity (From to 3): Water became clearer Some incidents (1) Pump broken On March 28th, the second day of the field trip, the system was discovered stopping at 4pm After checking the power source, water level sensor and pumps, the cause of incident identified was the pump motor failure There were some solid waste (nylon bag, rag, etc.) which obstructed the motor of pump therefore this led to the pump be broken It can be seen that the screening equipment is necessary to maintain the stability of the pumps (2) Pipe connections are not reliable, leakage In the first trip, the pipe, which leads water from collecting tank to receiving tank, had been broken The water level control float could not work and no water flowed into the system Thanks to the help of an environmental worker, the broken pipe was replaced 59 APPENDIX QCVN 14:2008/BTNMT In cording to National technical regulation of Vietnam (QCVN 14:2008/BTNMT) the parameters of wastewater quality assessment are shown in Table Permissible maximum value of pollution parameters in domestic wastewater as being discharged into the water resource receiving wastewater must not exceed Max value calculated as follows Cmax = C x K In which: Cmax is the permissible maximum concentration of pollution parameters in domestic wastewateras being discharged into the receiving water resource calculated by milligram per liter ofwastewater (mg/l); C is the concentration values of pollution parameters specified in Table K is a coefficient taking into account the size and type of services facilities, public facilities andcondominium specified in Table (Do not apply the formula for calculating the permissible maximum concentration in effluent forparameter pH and total coliforms) (a) Value of C Table Value of pollution parameters as a basis for calculating the permissible maximum value in domestic wastewater No Parameters Unit mg/l mg/l mg/l mg/l pH BOD5 (20*C) TSS TDS Sulfur (H2S) 60 Value C A B 5-9 5-9 30 50 50 100 500 1000 1.0 4.0 10 11 Ammonium (as N) Nitrate Animal fat and vegetable grease Total surface-active substances Phosphate (PO4-) (as P) Total coliforms mg/l mg/l mg/l mg/l mg/l MPN/100ml 30 10 3000 10 50 20 10 10 5000 Column A specifies value of pollution parameters as a basis for calculating the permissible maximum value in domestic wastewater as being discharged into water resources used for the purpose of domestic water supply (with water quality equivalent to that in column Al and A2 of the national technical Regulation on surface water quality) Column B specifies C value of pollution parameters as a basis for calculating the permissible maximum value in domestic wastewater as being discharged into water resources not used for the purpose of domestic water supply (with water quality equivalent to that in column B1 and B2 of the national technical Regulation on surface water or coastal water quality) (b) Value of K coefficient Depending on the type, size and area of use of service facilities, public facilities, apartment buildings and residential areas, businesses, the K value is applied under Table Table 0.1 Value of K coefficient corresponding to type of service facilities, public facilities, apartment buildings Size and area of use of facilities From 50 rooms or hotel rated stars or higher Less than 50 rooms Value of K Agencies, offices, schools, research institutions Greater than or equal to 10.000m2 1.0 Less than 10.000 m2 1.2 Department stores, Greater than or equal to 5.000 m2 1.0 Type of facilities Hotel, rest house 61 1.0 1.2 supermarkets Markets Restaurants, food stores Production facilities, armed force barracks Condominiums residential areas Less than 5.000 m2 Greater than or equal to 1.500 m2 Less than 1.500 m2 Greater than or equal to 500 m2 Less than 500 m2 From 500 people or more Less than 500 people From 50 apartments or more 62 1.2 1.0 1.2 1.0 1.2 1.0 1.2 1.0 ... 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. .. because the size of the pipe is small compared to that of Sekisui’s pilots The difference in the volume of the sponge layer and the amount of oxygen in the sewer pipe of Sekisui and the pipe in the. .. visit to in- sewer purification system in Coto Island .55 Basic information of Coto Island .55 Status of water drainage and in- sewer purification system .56 Sampling and monitoring result