Nghiên cứu ứng dụng công nghệ khai thác nước thấm lọc từ sông phục vụ cấp nước sinh hoạt và sản xuất ttta

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT THUY LOI UNIVERSITY NGUYEN TRUNG HIEU RESEARCH ON RIVERBANK FILTRATION TECHNOLOGY APPLICATION FOR WATER SUPPLY FOR DOMESTIC AND PRODUCTION ACTIVITIES Major: Ref number: Water supply and Sanitation Engineering 9580213 DOCTORAL DISSERTATION SUMMARY IN ENGINEERING HANOI, 2023 The Doctoral Dissertation is completed at Thuy Loi University Supervisors: Assoc.Prof Dr Doan Thu Ha Reviewer 1: Assoc.Prof.Dr Tran Thanh Son, Hanoi University of Architecture Reviewer 2: Assoc.Prof.Dr Pham Quy Nhan, Hanoi University of Natural Resources and Environment Reviewer 3: Assoc.Prof.Dr Luong Tho Bach, Hanoi University of Civil Engineering This dissertation will be defensed at the Dissertation Judging Committee in Thuy Loi University, Hanoi, 175 Tay Son, Dong Da, Hanoi at hour, 2023 This dissertation could be found at: - National Library - Library of Thuy Loi University INTRODUCTION Rationale of the study In the face of increasing demand on water supply for domestic, production use and economic development activities, water sources become scare, depleted and polluted Thus, it is essential and urgent to find out water source solutions The River Bank Filtration (RBF) Technology has been popularly used in European countries as Switzerland, France, the Netherlands, Hungary, Germany, and the Netherlands over the past 100 years In USD, this technology has been applied over 50 years Besides, India, China and Korea have started using it to provide drinking water RBF is a technology which uses river surface water through filtering sand, gravel layers in the riverbank, river terrace, creating exploitation efficiency with large volume and high quality In Vietnam, this technology has not been studied and applied widely and has not been considered to be a water source exploitation solution Recently, studies on RBF exploitation application have been carried out in some countries worldwide, but most of these studies focused on the exploitation capacity in specific positions and mainly in terms of water quality and water treatment In this context, the author carried out the “Research on riverbank filtration technology application for water supply for domestic and production activities” Research objectives - Assess the riverbank filtration exploitation potential and technology application for supplying water for domestic and production activities; - Assess the cleaning effectiveness of the riverbank filtration layer Research subjects and scope Research subjects: Riverbank filtration water, infiltration water quality, riverside stratigraphy, infiltrability, cleaning effectiveness, technological application process etc Research contents - - Study the riverbank filtration technology applicability; Analyze theorical basis, propose scientific basis, research methods and establish database for applying riverbank filtration technology in water supply for domestic and production activities; Assess riverbank filtration exploitation potential and technology application in water supply for domestic and production use; Assess infiltration water exploitation potential in typical research areas; Study, identify positions and flow rate of infiltration water to be exploited; Simulate groundwater flow and quality; Assess the cleaning effectiveness thanks to the riverbank filtration layer; Study, propose riverbank filtration treatment technology for water supply; Propose RBF technology application procedures; Research methods: In this dissertation, research methods used include: Data collection survey method; Data analysis, assessment, and synthesis; Inheritance method; Theoretical research methods; Mathematical modeling methods; Soil, water sample analysis method; Drilling method; Expert methods Scientific and practical significance of the research results Provide an engineering solution for effective water exploitation with highly applicability and low cost; Supply water for domestic and production activities, applicable in both rural and urban areas Reduce groundwater exploitation, protect groundwater resources Exploit water with stable quality thanks to the permeable layer, respond to current reduced quality and complicated situation of surface water Help to seek for more reasonably water supply and treatment solutions to handle shortcomings regarding water, water treatment cost, serving for the extension and improvement of water supply system, and enterprise development CHAPTER OVERVIEW 1.1 Overview of infiltration water uses as water supply source Over the past 100 years, the riverbank filtration technology has been applied widely in European nations such as Switzerland - 80% of drinking water is obtained from RBF wells, 50% in France, 48% in Netherlands, 40% in Hungary, 16% in Germany, USD, India In Vietnam, several groundwater exploitation works have been constructed near rivers which have large reserve thanks to surface water recharged from rivers as in Phu Tho, Tuyen Quang; Vinh Phuc; Quang Ngai; Quy Nhon., etc In Hanoi city, Red riverside groundwater has been exploited by treatment plants of Bac Thang Long, Gia Lam, Cao Dinh, Yen Phu, etc It is observably seen that, very few studies in Vietnam could provide proper assessments in nature, significance and scientific basis of riverbank filtration phenomenon, as well as the exploitation technology and engineering to provide water for economic and domestic activities 1.2 Riverbank filtration research works and projects Many studies on the exploitation of seepage water from rivers have been carried out by experts, proving the efficiency of river water extraction, using riverine permeable strata, allowing large-scale extraction with concentrated scale, good, stable water quality, low extraction and treatment costs (T Grischek; P Cady; N Tufenkji) The research results also show that there are 04 processes related to RBF technology, including: hydrodynamic, chemical, biological, and physicochemical The hydrodynamic process includes convection-dispersion transport, and dilution The aquifer acts as a filter for possible pollutant compounds in the river, where, due to the connection between the river and the aquifer, the groundwater is at risk of contamination Studies on the ability to remove organic pollutants have been performed Proven RBF technology can pre-treat organic pollutants The research results also demonstrate the high treatment efficiency of inorganic compounds of RBF technology In addition to variations in river water quality, the dilution that occurs when river water mixes with groundwater, which is usually of better quality, further helps to improve infiltration quality The biological processes that occur during leaching are directly dependent on the type of microorganisms living in the aquifer The metabolism of these microorganisms mainly determines the final quality of the permeable water Finally, there are physico-chemical processes involving absorption, precipitation, flocculation, coagulation and redox reactions These processes control the removal of particles from the porous medium, influence the concentration and activity of metals and inorganic compounds, and thus play a role in changing the chemistry of the water Currently, there has no specific research on RBF technology for assessing the effectiveness, potential and applicability of this technology in water supply service of Vietnam However, there are some RBF-related studies, scientific publications but mainly involving in the determination of flow rate and water exploitation capacity such as: Nguyen Van Dan, assessing groundwater resources in Hanoi Region and orienting research, exploitation for use; Pham Quy Nhan carried out research in Hanoi Region on the relationship between Red river water and groundwater; Nguyen Minh Lan conducted study on the relationship between river water and ground water, proposing method system on identification of the groundwater exploitation reserve in Red riverside, section from Son Tay Town to Hung Yen 1.3 Current status of water supply and water use demand in Vietnam Water supply in urban area: Surface water is the major source provided to urban and industrial areas while ground water contributed a small amount in these areas with around 2,000,000 m3/day, accounting for more than 20% total annually water supply volume It is forecasted that water demand for urban areas nationwide in 2020 is nearly 4.98 billion m3/year; and increases by 8.9 billion m3/year in 2030 Water supply in rural area: According to the Department of Water Resources’ data about water supply for rural area, by 2020, 88.5% population nationwide can access hygiene water, in which 51.7% use water quality meeting QCVN 01-1:2018/BYT with 60 l/person/day Water demand for domestic use in rural areas of Vietnam will be 4,783 million m3/year in 2030 1.4 Overview of surface, ground water, characteristics of water quality, reserve and exploitability Surface water source in Vietnam is relatively abundant with about 3,450 rivers, streams, a length of 10km or more, including 13 large rivers and 310 interprovincial rivers in 08 large basins with an area of about 270,000 km2 (making up 80% total large river basins) However, the surface water in several areas has been contaminated According to water storage structure, the mainland of Vietnam is divided into hydrogeological regions (hydrogeology), including 17 sub-regions Groundwater quality in Vietnam is relatively good However, recent survey findings show that both water level and quality nationwide tend to decrease: Groundwater in many places is of poor quality, with high iron and ammonium content, even many areas have arsenic-contaminated underground water sources but are still being exploited for domestic water supply Surface water exploitation plants mainly take water from rivers, streams, lakes, canals through treatment system to the consumption sources Groundwater exploitation plants exploit water from drilling wells with large diameter (D90-D325) Concentrated water supply treatment plants have technology lines of completed water exploitation, treatment and supply network, providing water for urban or rural residential areas and industrial, production zones which are independent from or interlaced with residential areas 1.5 Research orientation Contents to be studied consist of: 1) Assessing water sources, quality, reserves, exploitability, water scarcity situation; Assessing hydrological, hydrogeological conditions, water source situation in general zones within the research area as Red river Delta; Preliminarily assessing the applicability and necessity of RBF solution 2) Assessing the riverbank filtration exploitation potential (in typical research areas) 3) Studying, identifying positions and infiltration water reserve (in typical research areas) 4) Simulating groundwater flow and quality 5) Assessing the cleaning effectiveness thanks to the riverbank filtration layer 6) Analyzing to propose riverbank filtration technology 7) Propose RBF technology application procedures CHAPTER SCIENTIFIC BASIS AND STUDY METHODS OF RIVERBANK FILTRATION TECHNOLOGY APPLICATION 2.1 2.1.1 Theoretical and practical basis of RBF technological solutions Description of RBF technology Riverbank Filtration is a water exploitation technology using wells to extract water infiltrated from surface water sources as rivers, lakes These wells are equipped with water collecting and filtering pipes placed in aquifer Seepage water can be exploited in shallow aquifers that are non-pressurized It is replenished directly from aquifers There are 04 RBF technology related processes: hydrodynamics, chemistry, biology, and physico-chemistry The principle of infiltration water recharge is displayed in the (Figure 2.1) The infiltration water is also exploited in the pressurized aquifer where river directly cuts the pressurized aquifer, or riverside areas in which river water is recharged in the non-pressurized aquifer, then running through pressurized aquifer via hydrological windows Infiltration water collecting well Sand and sludge Sand Infiltration water Aquifer Filtering pipe of filtration wells Confined aquifer Figure 2.1 Principle of infiltration water replenishment Structure of wells used in RBF system could be vertical or horizontal which both bring different advantages Vertical wells could produce a better water quality meanwhile the horizontal ones bring higher reserve There are 04 processes related to RBF technology, including: hydrodynamics, chemistry, biology, and physical chemistry Particle deposition Drilled wells Recharge aeration due to water surface oscillation River bed (sediment layer) Mixing Mixing Filtering Biodegradation Absorption and Desorption Precipitation and disintegration Redox reaction Riverbank filtration Oxygen shortage (GW) Oxygen shortage (GW) Mixing Limited layer Figure 2.2 Summary of pollutant removal processes in RBF 2.1.2 Water quality improvement RFB removes pollutants by filtering, absorbing them into soil particles, decomposing microorganism, creating chemical precipitation and ion exchange, redox processes Pathogens, nutrients are also removed through the inactivation and adhesion, dissolved oxygen and biological process At the same time, RBF gets rid of heavy metals out of water sources by adsorption, precipitation and ion exchange processes 2.1.3 Clogging and self-cleaning issues in RBF RBF exploitation yield depends on several factors such as hydraulic conductivity and the contact between river and static aquifer Temperature is related to the viscosity in water; Clogging could happen due to physicochemical and biological processes, of which the blockage is mainly attributable to physical process as clay particles follow the water flow infiltrating into wells and retained in the aquifers’ voids, contributing to reduction of permeable coefficient and well exploitation capacity 2.1.4 Infiltration restoration thanks to the flow The RBF system’s rinsing or self-cleaning capacity depends on features of the riverbed’s particle and the stress caused by river water velocity 2.2 Selection, characteristics of research areas and influencing factors 2.2.1 Selection of research areas Locations where RFB technology pilot is studied must have: i) Suitably hydrological and hydrogeological conditions, seepage water can be obtained from the river; ii) Appropriate correlation of surface and groundwater that RBF technology could be effectively applied; iii) Area, infrastructure and topographical condition appropriate for developing experimental well system and monitoring boreholes; iv) Be capable of management and operation during the experiment Areas in Red River Delta include: Red Riverside areas from Minh Chau of Ba Vi, Hanoi to Tam Xa commune, Dong Anh, Hanoi and Cam Giang riverside in Tan Truong commune, Cam Giang district with suitable hydrological and hydrogeological conditions and good correlation regarding surface water and groundwater were selected for the Research on assessment of infiltration water exploitation potential Ghe pump station area, Cam Giang riverbank in Tan Truong commune, under the management of Hai Duong Water JSC with an area that is favor for the management and operation was selected by the author for the Research on pilot RBF technology 2.2.2 Characteristics of Red River flow in the research area In Red River system, there is a large difference of water level between flood reason and dry season The average flow in dry season through years in the Northern Region reaches 1,200 m3/s, while in the territory is 811 m3/s Water quality of Red River: High alluvium content, concentration of BOD, COD, NH4+, NO2, Ecoli, Coliform is many times as higher as QCVN 08MT:2015/BTNMT 2.2.3 Hydrogeological characteristics of the research area 2.4.2 Bases for identification of exploitation reserve Figure 2.26 Basis for identification of exploitation reserve 2.5 Forms of riverbank filtration works and infiltration well calculation methods 2.5.1 Forms of riverbank exploitation filtration works Basically, the form of riverbank filtration works is similar to that of normal groundwater exploitation ones, but only riverbank filtration wells are placed in the allowable positions where seepage water has the best reserve and highest quality Among riverbank filtration works, vertical wells are used the most with the various advantages Vertical wells in the (Figure 2.28) consist of main types: A Uncompleted, non-pressurized drilling wells C Uncompleted, pressurized drilling wells B Completed, non-pressurized drilling wells D Completed, pressurized drilling wells Figure 2.28 Forms of vertical wells 2.5.2 Method for calculation of infiltration wells 11 The calculation of infiltration well design is similar to that of normal groundwater exploitation wells Parameters related to the calculation of seepage wells: Static water level = water level of aquifer; seepage coefficient of aquifer; diameter of wells; pumping reserve; Thickness of aquifer, etc 2.6 Scientific basis and feasibility study methods on the removal of iron, manganese and ammonium from the groundwater by RBF 2.6.1 Diagram of experimental well field Figure 2.33 Diagram of experimental borehole beam in Tan Truong commune, Cam Giang district, Hai Duong province 2.6.2 Structure of experimental wells The well is designed based on parameters, stratigraphic data obtained from monitored wells and drilled stratigraphic samplings 2.6.3 Assessment of water seepage quality in comparison with river water in the research area 2.6.3.1 Parameters for assessing water quality Temperature; Conductivity; Iron; COD; NH4 2.6.3.2 Sampling positions On the river, at the research area; infiltration water from experimental wells and observed wells 2.6.4 Sampling method and analysis In accordance with Standard TCVN 6663-6:2018 Guidance on sampling of rivers, streams 2.7 Conclusion of Chapter Chapter analyzes scientific basis and research methods summarized from related studies and develops research method of the dissertation 12 CHAPTER STUDY ON RFB TECHNOLOGY FOR WATER SUPPLY 3.1 Assessment of RFB potential in typical research area 3.1.1 Position selected for the study of RFB potential Minh Chau commune, Ba Vi to Nhat Tan bridge- Tay Ho, Hanoi with the coordinates at 21°12′5″N 105°27′7″E, to Tam Xa commune, Dong Anh district, Hanoi city at the coordinate 21°06′34″N 105°50′37″E is selected to identify RFB exploitation capacity 3.1.2 Results of geological, hydrological structure study According to the study on hydrogeological cross-sections of the Red River in the research area, almost all positions in the Red River have a relation with qh and qp aquifers at different levels 3.1.3 Riverbank filtration potential in the research area To assess the riverbank filtration potential in the research area, analyze hydrological relationship between Red River water and groundwater, the author divided research areas and 04 zones in each area were selected: - Zone 1: The middle area of Red River coast in Minh Chau commune – Ba Vi - Zone 2: The South of Red River Coast in Son Tay town - Zone 3: The South and the middle area of the Red riverside in Thuong Cat commune - Zone 4: The North and the middle area of the Red riverside in Tam Xa commune 3.1.4 Contents to be implemented to identify the exploitation reserve in 04 zones for finding out the exploitation potential in research areas The findings show that when initial water level on the model is set and the correction will stop when the water level fluctuation over the time is reestablished with an error between actual and model level at boreholes observed while experimental pumping meeting allowable value 13 3.1.5 Assessment results of Red River filtration exploitation potential in typical research areas Legend Area with exploitation potential of 3,000 m3/day/1 borehole Figure 3.9 Map of Red river bank exploitation potential in research areas 3.2 Identification of riverbank filtration positions and reserve in research area in Tan Truong, Cam Giang, Hai Duong 3.2.1 Assessment of stratigraphic conditions, riverside permeability in Cam Giang, Hai Duong Qh aquifers in Cam Giang coast, including river sediments in Thai Binh stratigraphy (aQ23tb) and river – sea – lagoon sediments of Hai Hung formation (ambQ21-2 hh1) are distributed widely in the research area The thickness of the largest aquifer is in LK Ford (30m), LKTD30 (>17m) 3.2.2 River water and groundwater quality Quality of Cam Giang river water: Parameters of NH4+ - N is 1.06 – 9.72 times as higher as allowable standard; COD (1.13 – 2.43 times); NO2- - N (exceeding by 1.04 – 21.5 times) Quality of Cam Giang groundwater: Groundwater in this area is freshwater, with chemical form of HCO3-, content of chlorine ion is 32.79mg/l, of ion HCO3- is 344.76mg/l 3.2.3 RBF positions in Cam Giang river in Hai Duong province Cam Giang river belongs to the branch system, connecting Thai Binh river to Bac Hung river The research area is located in Trang Ky village, Tan Truong Commune, Cam Giang district, Hai Duong province, Cam Giang river banks 3.2.4 Research targets Identify: (i) Max reserve to be exploited in a well; (ii) max reserve of each well with different distance from wells to river; (iii) max reserve of well field with 14 various distance between wells (iv) time and water amount permeable from river 3.2.5 Model statement Figure 3.14 Model scope limit Layer 1: Clay Layer 2: qh aquifer Layer 3: Clay Layer 4: Clay Figure 3.15 Layers simulated model according to surveys in Tan Truong The model simulates a scale of 1700m x 1500m surrounding the construction of pilot section route in Tan Truong commune, Cam Giang district, Hai Duong This model is divided into 17000 net cells with 170 columns (dx = 10m), and 100 rows (dy =10m) (Figure 3.14) Based on overall hydrogeological data of Hai Duong and hydrogeological survey data in the pilot area, the model is divided into layers, as presented in (Figure 3.15) 3.2.6 Model results 3.2.6.1 Problem 1: Determination of max reserve in exploitation well Figure 3.1: Depth in designing wells and placing pump at 7m 15 As tan Truong model contains a 2m-thick confined aquifer on the surface, the max depth is 7m from the ground The reserve reaches Qmax = 1330 (m3/days) – (Figure 3.19) 3.2.6.2 Problem 2: Identification of max reserve of exploitation wells with various distances Table 3.2 Distance from wells to river and max exploitable reserve Distance from well to river (m) Total reserve (m3/s) 25 50 75 100 200 1.82E-02 1.64E-02 1.539E-02 1.48E-02 1.32E-02 Reserve in each well (m3/d) 1568 1421 1330 1275 1139 Figure 3.20 Diagram of well simulation with various distances from well to river 3.2.6.3 Problem 3: Identification of max reserve of well field to be exploited with different distances between wells Table 3.3 Results of max exploitable reserve for entire well field Distance between wells: 80m Distance between wells: 50m Well field Total reserve Reserve of Total reserve Reserve of (m3/d) each well (m3/d) each well (m3/d) (m3/d) well 1330 1330 1330 1330 wells 2219 1110 2218 1109 wells 2911 970 2886 962 wells 3772 943 3310 828 wells 4485 897 3997 799 16 3.2.6.4 Problem 4: Identification of water infiltration time and reserve Table 3.4 Simulation results of flow path length and moving period from river Name of Length of flow path (m) Moving period from river (day) wells Min Max Medium Min Max Medium Well 50.66 69.43 58.31 48.13 85.14 67.88 Well 49.86 76.53 56.12 36.71 81.8 49.1 Well 68.91 123.41 85.34 64.76 197.93 102.4 Well 69.97 132.32 90.63 72.05 282.13 132.5 3.3 Assessment of water quality improvement effectiveness owning to riverbank filtration layer in Tan truong, Cam Giang, Hai Duong 3.3.1 Assessment of Cam Giang river water and groundwater quality in research areas  Quality of Cam Giang river water + pH is from 7.3 – 8.6, commonly at level A1 stipulated in QCVN + Conductivity EC ranges from 184 – 733 µs/cm + DO content in water is from 1.1 – 5.1 mg/l + NH4+ content fluctuates from 1.5 to 4.2 mg/l + COD ranges from 4.1 to 11.2 mg/l  Groundwater quality of qh aquifer in Cam Giang area + NH4+ content is from 0.5 – 25 mg/l, average 1.5 mg/l + NO3- content is from 0.0- 18.14 mg/l, average 2.05 mg/l + NO2- contents is from 0.0- 28 mg/l, average 0.81 mg/l + COD content is from 0.8 – 20 mg/l, average 4.01 mg/l 3.3.2 Assessment of quality changes between river water and infiltration water Based on the results of analyzing water samples of Cam Giang river and boreholes with parameters as: ToC, EC, COD, NH4, Fe, the author assessed the quality of river water and infiltration water  Temperature and conductivity The temperature of Cam Giang river water changes upon reasons In the monitoring from May to November 2020, the water temperature ranges from 24.2 to 29.2 oC In drilling wells in Tan Truong, the temperature is relatively stable with a range from 25.0 oC to 29.6 oC 17 Changes in conductivity of river water and infiltration water (borehole) in 02 sampling phases and water quality analysis are presented in (Figure 3.28) EC-River in May EC-River in October EC-Borehole in May EC-Borehole in October Figure 3.28 Chart on conductivity of river water and well water in 02 monitoring phases According to analysis results, conductivity of Cam Giang river water fluctuates from 267 to 430 mS/cm in May and from 462 to 638 mS/cm in November Meanwhile, the figure of infiltration water is lower, with smaller fluctuation showing a stability in quality and lower pollution level This can be said that after running through filtering layers, minerals in water sharply decrease  COD and NH4 parameters COD-Cam Giang river NH4-Cam Giang river Figure 3.2 COD and NH4+ contents in river water and infiltration water in May In the infiltration water in the center well, COD content ranges from 0.8 to 1.86 mg/l, reducing from 73 to 86% compared to those in river water Therefore, during transporting from river to well, organic substances content reduces owning to oxidation and decomposition processes, demonstrating the capacity of removing organic matters thanks to the bottom sediment and riverbank Meanwhile, NH4 content in infiltration fluctuates between 0.54 to 2.18 mg/l, 18 reducing from 48 to 81% in comparison with those in river water This shows the ammonium treatment of sediment and riverbank The reduction of NH4 proves the changes of NH4 in sand and soil layers This paper results are consistent to previous studies This demonstrates that COD and NH4+ could be removed by filtering layer of riverbank which is attributed to the rate of river water infiltrating into aquifers, dissolved oxygen and biological processes  Iron and manganese By analyzing water quality, it is shown that: the simulation results of groundwater flow with pumping flow rate at 8m3/h gave a mixing ratio between surface water and groundwater in the center borehole of about 70-30, which is relatively consistent with the changes of Fe contents in infiltration water Mn content in Cam Giang river water ranges from to 0.03 mg/l, meanwhile the figure in the center drilling well is from 0.12 to 0.17 mg/l The content of Mn in infiltration water is higher than river water as it penetrates from ground water into the wells 3.3.3 Assessment on the removal of iron, manganese, ammonium and organic substances thanks to riverbank filtration layer The graphs in (Figure 3.38, Figure 3.39) display the distribution of Fe2+, Mn2+, NH4+, NO2-, NO3-, TN and COD in river water and seepage water in the boreholes within research areas by the direction perpendicular to Cam Giang River Accordingly, Fe2+ and Mn2+ content increases gradually by the distance from the river, representing the reduction of seepage amount from river and increase in groundwater from ground aquifer; Fe2+ strongly increases at the positions of seepage well exploited The NH4+, NO2-, NO3-, TN and COD contents reduce by the distance of boreholes to the river, proving the effectiveness of NH4+, NO2-, NO3-, TN and COD removal via riverbank filtration In the initial infiltration area, anoxic or anaerobic conditions creating activities of microorganisms in biodegradation processes The biochemical processes include nitrification, denitrification and anamox processes, explaining the reduction of substance concentration in infiltration water from river to boreholes Also, the reduction of COD is consistent to the NO3reduction in the course of denitrification 19 River Figure 3.38 Content of Fe2+, Mn2+, NH4+ and COD within river water and infiltration water in boreholes in the section perpendicular to river River Figure 3.33 Content of NH4+, NO2-, NO3- and TN within river water and infiltration water in borehole in the section perpendicular to river 3.4 Proposal of riverbank filtration treatment technology 3.4.1 Basis for proposal of riverbank filtration treatment technology (i) Seepage water quality; (ii) Requirements for supply water quality; (iii) treatment capacity; (iv) Area of treatment plants; (v) Topographical, engineering geological conditions and other local factors 3.4.2 Criteria for proposal of riverbank filtration water treatment technology (i) Lowest investment and operation management expense; (ii) Convenient and simple operation management; (iii) water quality stability, fulfilling requirements; (iv) In conformity with local conditions 3.4.3 Characteristics of seepage water quality to be treated According to the study results, FBF technology produces seepage water with the COD and NH4+ content of 85% and 76% respectively which is lower than those of river water Besides, iron content within infiltration water in research areas in Minh Chau, ranges from 2.25 to 4.21 mg/l, much lower than that in groundwater of qh aquifer in Minh Chau, which is from to 12mg/l 20 3.4.4 Capacity of treatment plants Treatment plant capacity is proposed capacity from 1,000 – 30,000 m3/day.night The treatment plant capacity depends on the infiltration water reserve along with conditions such as hydrogeological conditions, relation between river water and groundwater With RBF technology applied in the research area from Minh Chau, Ba Vi, Hanoi to Tam Xa, Dong Anh, Hanoi, each borehole has water supplying capacity from 500 – 3000 m3/day.night In Tan Truong, Cam Giang, Hai Duong, the figure is from 200 – 500 m3/ day.night 3.4.5 Diagram of riverbank filtration treatment technology The solution is to exploit infiltration water with high quality thanks to riverbank filtration layers Infiltration water contains small content of dissolved metals, COD and NH4+ as well as residual + Quality of infiltration water is assessed based on parameters of Fe2+ and NH4+, specifically: (i) Fe2+ content: – 10 mg/l; (ii) NH4+ content: – mg/l + Treatment plant capacity is proposed from 1,000 – 30,000 m3/day.night With small content of Fe2+ and NH4+, some infiltration water treatment technology lines are proposed as below: Diagram 1: Infiltration water with high quality, small capacity For small systems, the seepage water quality is relatively good with iron content of