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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 TN (CS) TN (RA) NH4-N (CS) NH4-N (RA) 70 60 57.2 mg/L 50 43.3 36.1 40 35.6 30 27.8 20 23.6 16.4 10 0 10 12 14 16 18 20 22 24 Time (h) Figure 3.17 TN and ammonia of outflows from coal-slag and rock-aggregate concrete sewer, with pump schedule of 15m ON/45m OFF TN (CS) TN (RA) NH4-N (CS) NH4-N (RA) 60 50 47.1 40 mg/L 31.6 30 24.5 20 10 0 10 12 14 16 18 20 22 24 Time (h) 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 CS-15/45 RA-15/45 CS-30/30 RA-30/30 TN reduction trend 60 Raw (35.6; 1h 57.2) (1) 50 TN (mg/L) 40 24h (16.4; 36.1) CS-15/45 (16.6, 30.1) (34.8; 53.7) (2) RA-30/30 (10.6, 24.5) 30 7h (29.0; 9h 46.0) (27.8; 43.3) NH4-N (y = x) CS-30/30 (12.8, 20.2) 20 (3) 10 0 10 15 20 25 30 35 40 NH4-N (mg/L) 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 In Fig 3.19, the correlation between TN and NH4-N is shown In raw sewage, TN concentration, symbolized by the blue line, composed of ammonia, suspended organic nitrogen, and NOx NOx was presumed to be neglectable as its portion was minor compared to other constituents in TN As TN and ammonia had the same reduction trend, when ammonia reduced by ammonia stripping and microbial oxidization, TN also lowered down accordingly The equation y = x, marked by the red line on the graph, represents the portion of ammonia-N in total nitrogen TN This line always presented the amount of remained ammonia in sewage, which was lower than the blue line regarding to the TN concentration 44 As the sewage run in sewer, self-purification processes took place, sedimentation of particulate organic matters, nitrification and ammonia stripping occurred together at the same time Particulate nitrogen (PN) settled down at the sewer bottom similarly to the removal of COD discussed in the previous section Take an example of RA sewer with pump schedule of 15mON/45mOFF, symbolled as RA-15/45, at raw sample, TN concentration was 57.2mg/L (mTN-0 = 57.2mg/L * 1.5L = 85.8mg) consisting of 35.6mg/L of NH4-N (mNH4-N-0 = 53.4mg) noted by (3), and 21.6mg/L of PN and (mPN = 32.4mg) noted by (2) on the graph After 9h of recirculation through the sewer, TN and NH4-N reduced to 65.0mg and 41.7mg respectively Therefore, the TN amount removed was 20.8mg and NH4-N amount reduced for 11.7mg, noted by (1) Hence, the TN portion removed by floc sedimentation after 9h was 9.10mg, almost 30% of its initial mass 3.3 Estimation of sewer treatment capacity Salt solution tracer was utilized to test the wastewater velocity inside the sewers, with a portable multifunctional Hach HQ40d The estimated flow velocity in the lab-scaled sewers were measured to be 9.32cm/s and 9.84cm/s for the 1st and 2nd pump schedules respectively for both sewers, since the concrete media thickness and pipe size were the same in two pipelines The two flow rates were not significantly distinct as the water level in the lab-scaled pipelines was relatively equal to each other From the estimated flow rate, I could be able to estimate the travelled distance of sewage according to the witnessed flow time in the self-purification sewer tentatively (Table 3.3) The idea is that how many percent of pollutants could be removed or transformed by self-purification technique in accordance to each section of the pipe length before it can arrive to WWTPs or discharge to water bodies in peri-urban or rural areas of Vietnam However, along the sewer pipe, domestic wastewater 45 continues to discharge and supply more pollutants, the actual pollution concentration at the end of pipe is quite difficult to be controlled Table 3.4 Estimation of flow distance from pump schedules in lab-scaled selfpurification sewer Time Flow time Flow rate Flow distance (h) (s) (m/s) (m) 900 84 2,700 252 4,500 419 Pump schedule 15mON/45mOFF 0.0932 6,300 587 8,100 755 24 21,600 2,013 1,800 177 5,400 531 9,000 886 30mON/30mOFF 0.0984 12,600 1,240 16,200 1,594 24 43,200 4,251 3.3.1 Removal efficiency of organic matters (COD) According to the model of the two lab-scaled sewers, after 9h flowing in the pipe, sewage can achieve the distance of 755m; and after 24h, the distance could be over 2,000m 46 Hence, as viewed in the model condition, after 24h or flowing for over 2km in dry condition, COD in sewage could be removed for almost 70% in both sewers made from CS and RA concrete The removal percentage of COD could be calculated in the following equation (Nwaigwe & Enweremadu, 2015) 𝐶𝑂𝐷𝑟𝑒𝑚𝑜𝑣𝑒𝑑 (𝑚𝑔) = (𝐶𝑂𝐷0 − 𝐶𝑂𝐷𝑡 ) ∗ 𝑉 [6] 𝑅𝑒𝑚𝑜𝑣𝑎𝑙 𝑟𝑎𝑡𝑒 (𝑚𝑔𝐶𝑂𝐷 ⁄𝑚2 ⁄ℎ) = 𝐶𝑂𝐷𝑟𝑒𝑚𝑜𝑣𝑒𝑑 ∗ 𝑉 ⁄𝜏⁄𝐴 [7] Where: V: Sewage volume of the experimental batch (L) = 1.5L; τ: Retention time (h) = 24h; A: Pervious concrete media area (m2) = 0.0336 m2; COD (CS) 200 COD (RA) 172 180 160 COD (mg/L) 140 120 72 100 68 80 54 42 60 40 20 0 84 252 419 587 755 2013 Flow distance (m) Figure 3.20 Treatment efficiency for COD of self-purification sewer pipe made from CS and RA concretes in dry flow pattern condition 47 COD (CS) 160 COD (RA) 133 140 120 COD (mg/L) 72 100 73 77 76 80 60 40 20 0 177 531 886 1240 1594 4251 Flow distance (m) Figure 3.21 Treatment efficiency for COD of self-purification sewer pipe made from CS and RA concretes in wet flow pattern condition Following the equation [7] on removal rate, the treatment capacity of two sewers for COD are calculated as follows For the 1st pump schedule, which exhibits a flow rate Q of 400mL/min or 24L/h and with the concrete media of 0.0336m2, COD removal efficiencies could be 219.5 and 241.8 mgCOD/m2/h for CS sewer and RA sewer respectively For the 2nd pump mode, with Q of 600mL/min or 36L/h, the efficiencies of CS and RA sewer are 113.5 and 111.6 mgCOD/m2/h respectively Since the removal mechanism for organic matters, assumed presented by COD, based considerably on sedimentation along the sewer channel, the self-purification capacity of sewage in dry flow pattern is higher than the wet flow pattern However, in the work-scaled sewer, this phenomenon requires frequent removal of sludge in the sewer or maintenance of drainage should be put more attention, which is one drawback of the in-sewer purification technique so far Based on the removal rates of two sewers or equation [6], in the dry condition, COD in sewage of CS sewer could be removed by 68.6% after sewage flows for more than 2km RA sewer showed a slightly better efficiency of 75.6% COD removed with the 48 same pipe length The removal rates were 45.9% and 45.1% of CS and RA sewer respectively during wet flow pattern The effluents after 24h of two sewers in both pumping schedules met the regulation leveled A for COD (≤75mg/L), sewage quality dischargeable to waterbodies which can be used for water supply, in Vietnam national technical regulation on domestic wastewater (QCVN 14-MT:2015/BTNMT) 3.3.2 Removal efficiency of Ammonia (NH4-N) and total nitrogen (T-N) The same calculation processes were also applied to estimate the removal efficiency of the two self-purifying sewers for Ammonia and total nitrogen, using equation [6] and [7] TN (CS) TN (RA) NH4-N (CS) NH4-N (RA) 70 60 57.2 mgN/L 50 43.3 40 35.6 37.6 36.1 30 30.1 27.8 20 23.6 16.6 16.4 10 0 500 1000 1500 2000 Flow distance (m) Figure 3.22 Treatment efficiency for NH4-N of self-purification sewer pipe made from CS and RA concretes in dry flow pattern condition For the 1st pump schedule simulating dry flow pattern, NH4-N removal efficiencies in CS and RA sewer were 35.3 and 35.7 mgNH4-N/m2/h respectively For the 2nd schedule, the removal rate could increase to 32.2 and 36.3 mgNH4-N/m2/h for two sewers Hence, during dry condition, after 24h of flowing in the self-purification sewer pipe, NH4-N in sewage could be reduced by 53.4% in CS sewer and 53.9% in RA sewer 57.5% and 64.8% estimated amount of ammonia could be removed after 24h during wet condition in the CS and RA sewer 49 TN (CS) TN (RA) NH4-N (CS) NH4-N (RA) 60 50 47.1 mgN/L 40 31.6 30.1 30 24.5 20.2 19.8 20 19.4 12.8 10 10.6 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Flow distance (m) Figure 3.23 Treatment efficiency for NH4-N of self-purification sewer pipe made from CS and RA concretes in wet flow pattern condition TN removal rates were of 50.4 and 39.2 mgTN/m2/h for CS and RA sewer respectively in the 1st pump schedule After 24h, TN in CS and RA sewer pipe could be removed for 47.4% and 36.9% respectively In the nd schedule, CS sewer still performed a better efficiency of 50 mgTN/m2/h compared to a rate of 42 mgTN/m2/h in RA sewer After 24h recirculating, 57.1% and 48.0% TN amount could be reduced by self-purification process in the two sewers respectively, the effluent concentration after 24h in both sewers and in both pumping schedules met the regulation B (≤40mg/L) for total nitrogen, dischargeable to waterbodies which are not used for water supply, in QCVN 14-MT:2015/BTNMT 50 CONCLUSION Several remarks and conclusions could be obtained from the study on selfpurification capacity of lab-scaled sewer pipe as follows (1) Pervious concrete made from coal slag (CS), an industrial by-product, and conventional rock aggregate (RA) sized 2.0 – 2.8mm have shown their valuable abilities as microbial media material such as high porosity (21 – 33% void volume) and permeability (1.28 – 3.93 cm/s), capable of capturing particulate organic matters and supporting accommodation for microorganisms to adhere, hence enhancing the self-purification capacity of sewage biologically (2) The two sewers installed with CS and RA pervious concrete performed a good pretreatment capacity for municipal wastewater assessed by removal of COD, NH4-N, TN Removal rates for these three parameters of CS sewer reactor were COD: 219.5, NH4-N: 35.3, TN: 50.4 mg substrate/m2/h for dry flow pattern and COD: 113.5, NH4-N: 32.2, TN: 50 mg substrate/m2/h for wet flow pattern condition Removal rates of RA sewer reactor were COD: 241.8, NH4N: 35.7, TN: 42 for dry flow pattern and COD: 111.6, NH4-N: 36.3, TN: 42 mg substrate/m2/h for wet flow pattern respectively The effluents in two sewers in both dry and wet flow patterns could meet the regulatory standards stated in QCVN-14/2015-BTNMT for COD (level A) and TN (level B) (Appendix 2) (3) After merely 30 days in operation, pH still increased in sewage when it contacted with pervious concrete, however, microbial activities were still recorded via the oxygen concentration reduction in the headspace of sewer After 24h in operation, oxygen gas in sewer’s atmosphere reduced from 21% to around 17% in average, assumed mostly for oxidization of organic matters in sewage and nitrification process Oxygen amount consumed were 65.1mg 51 and 61.2mg in average in the 1st and 2nd pump schedules respectively in CS sewer; (4) The in-sewer purification technology using modified sewer made from reused coal slag and natural rock aggregate could be feasible to be applied in the case of water sanitation in Vietnam because of its low cost, ease of construction and rich abundancy in source The practice could contribute to solve the water pollution issues in the country and on the other hand help to reduce the slag by-product waste being landfilled by reusing coal slag as sewer construction material (5) Self-purification sewer made from pervious concrete materials could be applied as a pretreatment unit in sewerage system in Vietnam to reduce the pollution load in wastewater before further treatment in WWTPs or to achieve the wastewater standard before discharging to water bodies where WWTPs have not been invested The technique should be applied at a work-scaled sewage conduit such as My Dinh Open Canal where access for maintenance and sludge removal is feasible I hope the results obtained in this study will help open further researches and studies on the pretreatment process for sewage in Vietnam using sewer network, as well as investigate more potentials of pervious concrete in public facility construction such as sewerage infrastructures Due to the lack of knowledge and skills, I may not conduct the study at highest polished form, in that case any comments and distribution to make this research become more meaningful and valuable are immensely appreciated 52 REFERENCES (1) An, D T (2014) Waste water management and sanitation practices in Viet Nam (2) Baban, A., & Talinli, I (2009) Modeling of organic matter removal and nitrification in sewer systems - an approach to wastewater treatment Desalination, 246(1–3), 640–647 https://doi.org/10.1016/j.desal.2008.07.018 (3) Ćosić, K., Korat, L., Ducman, V., & Netinger, I (2015) Influence of aggregate type and size on properties of pervious concrete Construction and Building Materials, 78, 69–76 https://doi.org/10.1016/j.conbuildmat.2014.12.073 (4) Dean, S., Montes, F., Valavala, S., & 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