VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY LUONG HUU TRUNG EVALUATION OF THE PERFORMANCE OF LAB SCALED SELF PURIFICATION SEWER SYSTEM FOR MUNICIPAL WASTEWATER TREATMENT IN VIETNAM MAS[.]
VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY LUONG HUU TRUNG EVALUATION OF THE PERFORMANCE OF LAB-SCALED SELF-PURIFICATION SEWER SYSTEM FOR MUNICIPAL WASTEWATER TREATMENT IN VIETNAM MASTER'S THESIS ENVIRONMENTAL ENGINEERING Hanoi, 2019 VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY LUONG HUU TRUNG EVALUATION OF THE PERFORMANCE OF LAB-SCALED SELF-PURIFICATION SEWER SYSTEM FOR MUNICIPAL WASTEWATER TREATMENT IN VIETNAM MAJOR: Environmental Engineering CODE: Pilot RESEARCH SUPERVISOR: Assoc Prof Dr HIROYASU SATOH Prof Dr JUN NAKAJIMA Hanoi, 2019 ACKNOWLEDGEMENT At very first words, my gratefulness goes to all lecturers, officers and staffs in Environmental Engineering Program (MEE), Vietnam Japan University (VJU) and Japan International Cooperation Agency (JICA) for giving me the precious opportunity to study and train under this disciplinary academic environment, where I could improve myself unexpectedly and access to a broader career future In advance, I would like to spend the most gratitude toward my supervisors, Assoc Prof Hiroyasu Satoh and Prof Dr Jun Nakajima, for their intense support and supervision throughout the time I did the thesis I could not accomplish the thesis without your guidance and enthusiasm throughout all progresses, from initial research idea, reactor setup, experimental analysis and revision of the draft and presentation And last, I also really appreciate the support and encouragement from my classmates, friends and family, those who have contributed to my two wonderful years in VJU, turning it into something priceless and unforgettable in my youth i TABLE OF CONTENT ACKNOWLEDGEMENT i TABLE OF CONTENT ii LIST OF FIGURES iv LIST OF TABLES vii LIST OF ABBREVIATION viii CHAPTER INTRODUCTION TO SELF-PURIFICATION SEWER FOR MUNICIPAL WASTEWATER TREATEMENT IN VIETNAM .1 1.1 Wastewater treatment and management in urban areas of Vietnam .1 1.2 Introduction to a new approach: In-sewer self-purification technique 1.3 Modified sewer for enhancing the self-purification capacity of sewage .6 1.4 Pervious concrete as potential material for self-purification sewer 1.4.1 Introduction to pervious concrete 1.4.2 Constituent and mix design 1.4.3 Sustainable construction material 10 1.4.4 Potential usage for self-purification sewer construction 10 1.5 Objectives 11 CHAPTER MATERIALS AND METHODOLOGY 12 2.1 Lab-scaled self-purification sewer reactor 12 2.1.1 Reactor setup .12 2.1.2 Reactor operation 14 ii 2.1.3 Sampling and analytical methods 15 2.2 Microbial media for the modified self-purification sewer 17 2.2.1 Pervious concrete as a potential material for self-purification sewer 17 2.2.2 Physicochemical characteristics of pervious concrete made from conventional and waste aggregates 19 CHAPTER RESULTS AND DISCUSSION 24 3.1 Potential characteristics of pervious concrete as microbial media 24 3.1.1 Density, porosity and permeability 24 3.1.2 Morphology and chemical composition 25 3.2 Pollution transformation regimes in self-purification sewer .33 3.2.1 Sedimentation and oxidization of organic matters 33 3.2.2 Ammonia stripping due to high pH 40 3.3 Estimation of sewer treatment capacity .45 3.3.1 Removal efficiency of organic matters (COD) 46 3.3.2 Removal efficiency of Ammonia (NH4-N) and total nitrogen (T-N) 49 CONCLUSION 51 REFERENCES 53 APPENDIX .56 iii LIST OF FIGURES Figure 1.1 Sample modified sewer equipped with porous media for microbial attachment, with an impervious outer wall to prevent leakage of sewage Figure 1.2 Sample pervious concrete made from byproduct coal-slag coarse aggregate (A) and conventional rock coarse aggregate (B) Figure 2.1 Flow diagram of PVC sewer reactor installed with pervious concrete media, oxygen gas sensor, recirculation tank and pump 13 Figure 2.2 Self-purification sewer reactors with equipment and porous concrete inward Left sewer is coated with pervious concrete made from industrial by-product (coal-slag) while conventional rock-aggregate pervious concrete is used in the right sewer 14 Figure 2.3 My Dinh Canal in Nguyen Co Thach Street, My Dinh, Nam Tu Liem 15 Figure 2.4 Pervious concrete media for the PVC sewer reactor (A) Pervious concrete was placed inside in the bed of the sewer for evenly distribution of sewage and more esthetical look (B) Hardened coal-slag pervious concrete; (C) Hardened rockaggregate pervious concrete 18 Figure 2.5 Darcy’s Law experiment system for testing permeability of concrete 22 Figure 3.1 Surface structure of raw coal-slag aggregate, before submerged in the CS sewer for operation, observed under two scales of 1/1000 and 1/5000 with SEM 26 Figure 3.2 Comparison of coal-slag surface structure before and after running with municipal sewage for 30 experimental days .27 Figure 3.3 Surface structure of raw rock aggregate, before submerged in the RA sewer for operation, observed under two scales of 1/1000 and 1/5000 with SEM 28 iv Figure 3.4 Comparison of rock-aggregate surface structure before and after running with municipal sewage for 30 experimental days .29 Figure 3.5 Chemical composition of raw coal-slag aggregate 31 Figure 3.6 Chemical composition of coal-slag aggregate submerged in sewage inside CS reactor for 30 experimental days 31 Figure 3.7 Chemical composition of raw conventional rock aggregate 32 Figure 3.8 Chemical composition of rock aggregate submerged in sewage inside RA reactor for 30 experimental days .32 Figure 3.9 Correlation between Turbidity and COD in CS and RA sewers both in 15mON/45mOFF and 30mON/30mOFF pump schedules .33 Figure 3.10 COD change in effluent of lab-scaled self-purification sewer, running with pump schedule of 15mON/45mOFF simulating dry condition 34 Figure 3.11 COD change in effluent of lab-scaled self-purification sewer, running with pump schedule of 30mON/30mOFF simulating wet condition 34 Figure 3.12 Sedimentation flocs settled down on coal-slag concrete (A) and rockaggregate concrete (B) while sewage flowed through the lab-scaled sewer 37 Figure 3.13 Detached floc from pervious concrete media settled down at the bed of the recirculation tank in coal-slag sewer reactor .37 Figure 3.14 Oxygen concentration monitored in headspace of coal-slag sewer reactor by Oxygen sensor (Experimental date: April 9th, 2019) 38 Figure 3.15 Ammonia in effluent of coal-slag and rock-agregate concrete sewer, with schedule of 15m ON/45m OFF 40 Figure 3.16 Ammonia in effluent of coal-slag and rock-agregate concrete sewer, with schedule of 30m ON/30m OFF 41 v Figure 3.17 TN and ammonia of outflows from coal-slag and rock-aggregate concrete sewer, with pump schedule of 15m ON/45m OFF .43 Figure 3.18 TN and ammonia of outflows from coal-slag and rock-aggregate concrete sewer, with pump schedule of 30m ON/30m OFF .43 Figure 3.19 Correlation between NH4 and TN in CS and RA sewers in both 15/45 and 30/30 pump schedules; (1) Portion of TN which was removed by ammonnia stripping, (2) Portion of particulate nitrogen (P-N), (3) Remained ammonia 44 Figure 3.20 Treatment efficiency for COD of self-purification sewer pipe made from CS and RA concretes in dry flow pattern condition 47 Figure 3.21 Treatment efficiency for COD of self-purification sewer pipe made from CS and RA concretes in wet flow pattern condition 48 Figure 3.22 Treatment efficiency for NH4-N of self-purification sewer pipe made from CS and RA concretes in dry flow pattern condition .49 Figure 3.23 Treatment efficiency for NH4-N of self-purification sewer pipe made from CS and RA concretes in wet flow pattern condition 50 vi LIST OF TABLES Table 1.1 Capacity of several wastewater treatment plants in Vietnam (Source: NGOenvironment.com; Hanoi Department of Construction, 2015) Table 2.1 General wastewater quality of My Dinh Canal in Nguyen Co Thach Street 16 Table 2.2 Experimental sampling schedule of two sewer reactors 17 Table 3.1 Properties of Portland cement pervious concrete from coal-slag and rock aggregate 25 Table 3.2 Composition of coal-slag aggregate in Pha Lai Thermopower Plant analyzed by X-Ray Fluorescence (XRF) 30 Table 3.3 Correlation of sedimentation and microbial digestions for organic matters removal in self-purification sewers 39 Table 3.4 Estimation of flow distance from pump schedules in lab-scaled selfpurification sewer 46 Table A.1 Test of heavy metals released from coal slag aggregate 56 Table A.2 Maximum permissible concentration for domestic wastewater parameters discharged from households 56 vii LIST OF ABBREVIATION AAO: Anaerobic – Anoxic – Aerobic ASTM: American Society for Testing and Materials CAS: Conventional Activated Sludge CS: Coal Slag EDS: Electron Dispersion Spectrometry ICOP: Intermittent Contact Oxygen Process MWW: Municipal Waste Water OD: Oxidation Ditch PCPC: Portland Cement Pervious Concrete PN: Particulate Nitrogen PPD: Physical Pollutants Deposition RA: Rock Aggregate RCA: Recycle Concrete Aggregate SBR: Sequencing Batch Reactor SEM: Scanning Electron Microscopy SWMM: Standard Methods for The Examination of Water and Wastewater WWTP: Wastewater Treatment Plant viii described further in the session 2.2 The installation of concrete inward the reactors was to ensure the even distribution of sewage and prevent shortcut flow After media placement and connection of inflow and outflow pipes, the sewer was covered completely with a transparent lid to make air-tightness condition for monitoring the change of headspace oxygen gas concentration as well as observing inside Each reactor was equipped with a recirculation tank (capacity of 1.5L), a recirculation pump, an oxygen gas sensor (Grove-Gas Sensor O2, Seeed Studio), a thermometer and other connection pipes, illustrated in the Fig 2.1 and the photo in Fig 2.2 All equipment was connected and controlled by an Arduino UNO board, which acted as a micro-computer with a crucial function to operate the pump and log data from sensors A compact LCD screen connected with the board showed all operational data supporting real-time monitoring for operators Finally, an air pump connected with the inflow pipe was utilized to regenerate atmosphere in the sewer headspace after each experiment, since oxygen was supposed to be consumed for chemical and biological reactions occurred inside the system Figure 2.1 Flow diagram of PVC sewer reactor installed with pervious concrete media, oxygen gas sensor, recirculation tank and pump 13 Figure 2.2 Self-purification sewer reactors with equipment and porous concrete inward Left sewer is coated with pervious concrete made from industrial by-product (coal-slag) while conventional rock-aggregate pervious concrete is used in the right sewer 2.1.2 Reactor operation Batch experiments were conducted to evaluate the treatment performance of selfpurification sewers equipped with two different pervious concretes The two sewer reactors were operated using the same influent, pumping schedule and under the same temperature The purpose was to monitor and compare the pollutant removal rate of two sewers equipped with two media materials 1.5L of raw sewage was filled in the recirculation tank of each reactor before experiment right after sampling Sewage was then recirculated through the sewer with two pumping schedules: (1) 15minsON/45minsOFF with Q of 400mL/min and (2) 30minsON/30minsOFF with Q of 600mL/min to simulate dry and wet condition flow patterns respectively 14 2.1.3 Sampling and analytical methods Raw sewage from an open canal on Nguyen Co Thach Street, Nam Tu Liem District, Hanoi which transports domestic wastewater of surrounding residential areas to Phu Do WWTP (tentative capacity of 84,000 m3/d) was collected as influent for the sewer reactors For each batch experiment, new raw sample from the canal was taken accordingly; therefore, the inlet quality of each batch was different as the deviation shown in Table 2.1 Sampling process was taken under nice weather when there was no rain in one or two days prior to the sampling day The sample collection took place at around a.m in the morning when pollutant load was considered at highest level of the day (SHOJI et al., 2015), then 1.5L of raw sewage was filled in the recirculation tank of each reactor accordingly The samples used for experiment and analysis of two sewers were collected on March 23rd, 28th and April 23rd for the 1st pumping schedule (15mON/45mOFF, 400mL/min), and April 6th, 9th and 13th for the 2nd schedule (60mON/60mOFF, 600mL/min) On other days, the reactors were still operated to maintain the continuous environment without experimental analysis Figure 2.3 My Dinh Canal in Nguyen Co Thach Street, My Dinh, Nam Tu Liem 15 Several samples have been collected to test the raw water quality of the canal, which is described in the Table 2.1 Table 2.1 General wastewater quality of My Dinh Canal in Nguyen Co Thach Street Parameters pH Value 7.3 ± 0.1 DO (mg/L) 0.22 ± 0.1 BOD (mg/L) 116 ± 33 COD (mg/L) 186 ± 94 NH4 (mg/L) 42.2 ± 6.26 TN (mg/L) 52.1 ± 8.17 During batch experiments, the effluent from two reactors were collected at 0, 1, 3, 5, 7, and 24h of flowtime to measure the change of water quality over different lengths of the purifying pipes Oxygen gas concentration in sewer headspace was also monitored by the Grove sensor and recorded every second Sample name was assigned regarding to the sampling time (E.g CS-1 is the sample taken after 1h of recirculation from the coal-slag pervious concrete sewer, and similarly RA-1 is the sample from rock-aggregate sewer with the same flowtime) It is estimated that the time a portion of wastewater requires to reach WWTP ranges around to 9h, which is equivalent to retention time in Activated Sludge reactor However, another sample at 24h of flow was taken to see how much the sewage quality can be improved or whether the removal rate remains stable All analytical processes took place in Environmental Engineering Laboratory in VJU Water parameters monitored includes pH, Turbidity, COD, NH4 and T-N Mettler Toledo Seven Compact pH meter was utilized for measuring of pH Turbidity was measured with HANNAH portable turbidity meter, model HI98703 COD in sewage was analyzed following Standard Method 5220D Closed Reflux, Colorimetric method (SMWW, Section 5220) Ammonia-Nitrogen was analyzed with Phenate Method (SWMM, Section 4500) and Total Nitrogen was analyzed following Analytical methods for wastewater examination (ASTM D8083) 16 Table 2.2 Experimental sampling schedule of two sewer reactors Sample Recirculation time 2.2 (h) Coal-slag (CS) sewer Rock-aggregate (RA) sewer CS-0 RA-0 CS-1 RA-1 CS-3 RA-3 CS-5 RA-5 CS-7 RA-7 CS-9 RA-9 24 CS-24 RA-24 Microbial media for the modified self-purification sewer 2.2.1 Pervious concrete as a potential material for self-purification sewer From several advantages reviewed in the literature in session 1.4, pervious concrete has been proven to be a potential material for self-purification sewer construction with high porosity and permeability for sewage to infiltrate through, providing pore space and rough surface for microorganism to grow, which can enhance the selfpurification capacity of domestic sewage Two coarse aggregates were chosen as main constituent for the experimental pervious concrete, one was a conventional material used in normal concrete and another was a by-product from industrial process Angular rock gravel exploited at a stream bank in Phu Tho District was chosen as conventional aggregate Coal slag, residue from coal combustion in Pha Lai thermopower plant, was reused as waste or by-product aggregate for the pervious concrete Both of these two materials were then sorted by 17 sieves into size ranges of 2.0 – 2.8, 2.8 – 4.0, 4.0 – 5.6 mm Aggregates sized 2.0 – 2.8 mm were chosen for the experiment since concrete made from this small-medium aggregate produces a better workability and be more suitable in size for a lab-scaled reactor Each aggregate type was mixed with Portland cement with ratio of 3:1 in volume, the combination was then hydrated by just enough water to produce a workable mixture ready to be placed inside the sewer (Fig 2.4A) Figure 2.4 Pervious concrete media for the PVC sewer reactor (A) Pervious concrete was placed inside in the bed of the sewer for evenly distribution of sewage and more esthetical look (B) Hardened coal-slag pervious concrete; (C) Hardened rock-aggregate pervious concrete 18 Several methods to evaluate the properties of experimental concretes used for sewer reactors are described in session 2.2.2 2.2.2 Physicochemical characteristics of pervious concrete made from conventional and waste aggregates To quantify how much the porous space the pervious concrete possesses, and how good it can retain fluid or allow fluid to pass through, porosity and hydraulic conductivity of the concrete were measured Herein, alongside with the main concrete blocks installed in the sewer reactors, the concrete paste used to make the block was also used for making other specific blocks to serve for concrete parameters measurement The concrete block in the reactor was supposed to have the same property as the concrete block for the measurement of these parameters 2.2.2.1 Density and porosity Porosity and density are considered crucial parameters for pervious concrete, needed for design and comparison with other construction materials (Dean, Montes, Valavala, & Haselbach, 2005) Porosity is defined as the volume of void space over the total volume of a pervious concrete block stated in percentage % The method applied for measurement in this experiment follows the idea of water displacement method (Montes, et al., 2005) but in a simplified version The porous space inside concrete block is determined by the water amount which infiltrated and replaced air in the matrix after a period of 30 minutes in submergence The detail experiment process is described as follows Apparatus (1) Cylindrical plastic moulds, used for keeping pervious concrete sample; (2) Ruler, used for measuring diameter and height of concrete specimen; (3) Balance with accuracy to the nearest of 0.1g; (4) Oven, capable for rising temperature more than 100oC; (5) Water bath; 19 (6) Graduate cylinder, with accuracy to the nearest 0.5ml; Specimen From the concrete mixture used to make the sewer concrete block, the paste is installed into the cylindrical moulds fully up to its mount The process is triplicated to achieve average result The samples are then kept in shade and covered with plastic film to prevent moisture vaporization and the solidification of concrete blocks completes after two days Procedure (1) Dry the specimens stored in cylindrical moulds completely in the oven for 24h at 105oC; (2) Weigh the samples with balance, record the dry weight (Wdry); (3) Measure the diameter (D) and height (H) of each sample, record it for Total Volume (Vtotal); (4) Submerge the samples into water bath, filled with tap water at room temperature (~20oC) for at least 30 minutes; (5) Rotate and tap the samples 10 times around its circumference with a rubber mallet to let air escape from the core completely; (6) Take out concrete samples, rotate them upside down to pore all water trapped into graduate cylinder through a funnel Let the samples sit for 10 minutes and tap them with rubber mallet 10 times; (7) Record water amount poured out from the submerged concrete blocks It is assumed that the water volume (mL) is equivalent to the void space volume (Vvoid) (cm3); (8) Calculate the porosity of the concrete sample by the equation below; Calculation (1) Total volume of concrete sample: 20 𝐷 𝑉𝑡𝑜𝑡𝑎𝑙 (𝑐𝑚3 ) = ( ) ∗ 𝜋 ∗ 𝐻 [1] (2) Density of pervious concrete sample: 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 ( 𝑔 𝑐𝑚3 )= 𝑊𝑑𝑟𝑦 𝑉𝑡𝑜𝑡𝑎𝑙 [2] (3) Porosity of pervious concrete sample: 𝑃(%) = 2.2.2.2 𝑉𝑣𝑜𝑖𝑑 𝑉𝑡𝑜𝑡𝑎𝑙 ∗ 100 [3] Hydraulic conductivity Pervious concrete is considered a potential emerging construction material to enhance surface water runoff because of its capability to let water infiltrate rapidly, ranging typically from 120 to 320 L/m2/min (Sonebi et al., 2016) This ability of the experiment concrete is assessed via hydraulic conductivity K or permeability (cm/s) Darcy’s law experiment system in MEE laboratory was utilized to test the permeability of pervious concrete It applies the theory of potential energy from height difference between water source and tested material to see how much effluent flowing through the concrete column The equipment needed and the experiment procedure are illustrated as follows (Stapleton, Ph, Antonio, Mihelcic, & Ph, 1994) Apparatus (1) Pervious concrete column with thickness (H) measured, and another water column at different elevation (higher than the concrete column); (2) Constant source of water at room temperature and collection basin for overflow port; (3) Stop watch; (4) Ruler; (5) Graduate cylinder, with accuracy to the nearest 0.5ml; Procedure 21 (1) Run the water at a fixed rate, and wait until h1 and h2 are stabilized; (2) Measure the effluent discharged from concrete column according to that Δh (h1 – h2); (3) Increase the h1 of the higher water column compared to h2 of the lower concrete column, wait 3-5 minutes for the system to be stable; (4) Measure the effluent discharge again according to the new Δh; (5) Repeat the procedure from step (3) to record the change of effluent volume; (6) The Q and Delta h in the Darcy’s equation has a linear correlation, from that we could estimate the KA/L, then hydraulic conductivity constant (K) of material could be calculated The experiment procedure is illustrated by the Fig 2.5 Figure 2.5 Darcy’s Law experiment system for testing permeability of concrete 22 Calculation (1) Hydraulic conductivity of pervious concrete: 𝑄 =𝐾∗𝐴∗ ℎ1−ℎ2 𝐿 = 𝐾𝐴 𝐿 (ℎ1 − ℎ2 ) [4] Q: Flow (cm3/s); K: Hydraulic conductivity constant (specific for each porous material) (cm/s); A: Area of material block (cm2); L: Thickness of material block (cm); h1: elevation of higher elevation where water starts to fall down (cm); h2: elevation of lower elevation where water reaches (cm); 2.2.2.3 SEM and EDS Coarse aggregate, the main proportion consisted in pervious concrete, has been shown to have critical role in the concrete characteristics For instance, interconnected porous matrix in pervious concrete is determined mostly by the coarse aggregate type rather than its size (Ćosić, Korat, Ducman, & Netinger, 2015) The material types such as conventional and by-product aggregates used in the research were also measured to evaluate their potential as an adsorbent and porous media for microorganism to grow in later phase of sewer pipe’s lifespan Two types of concrete aggregate including coal slag and rock angular aggregate, sized 2.0 – 2.8mm, were tested for surface structure and composition both at raw state and after running with sewage for around 20 experimental days by Scanning Electron Microscopy (SEM) JOEL modeled JSM-IT100, integrated with the Electron Dispersion Spectrometry (EDS) JOEL modeled JED-2300 in Nanotechnology Laboratory, Vietnam Japan University (VJU) 23 CHAPTER RESULTS AND DISCUSSION 3.1 Potential characteristics of pervious concrete as microbial media 3.1.1 Density, porosity and permeability Several key properties of pervious concretes utilized for the experimental reactors are illustrated in Table 3.1 Compared to the reference data for other pervious concretes, the concretes made from conventional rock and coal-slag aggregates obtained equivalent values in porosity and permeability, though the aggregate sizes used in both concrete were relatively finer (2.0 – 2.8mm) than convention aggregate for ordinary PCPC (4 – 20mm) Among the two experimental blocks, coal-slag concrete showed better characteristics both in porosity (33%) and hydraulic conductivity (3.93 cm/s) than the concrete made from rock-aggregate (21% and 1.28 cm/s respectively) The prior material could let water infiltrate at a rate almost three times higher than that of the rock concrete Coal slag, at a first glance, presented a much rougher surface when touched by hand, as it is residue from coal combustion process The material had undergone tremendous modification in morphology and internal structure at high temperature and pressure in the blast furnace Hence, there was already interconnected porous matrix inside the slag, which was witnessed under SEM image (Section 3.1.2) However, the strength or durability of coal-slag concrete seems to be much lower than rock pervious concrete Though no experiment was conducted to measure the strength of two concrete materials, their durability can be compared through density data (Shohana Iffat, 2015) Coal-slag porous concrete density was about 60% to that of rock porous concrete, and only 47% when compared to ordinary impervious concrete This drawback on strength and durability of the concrete, which is crucial in public infrastructure design for long-term usage, could be ameliorated by substituting natural coarse aggregate (NCA) by recycled coarse aggregate (RCA) at