Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.Nghiên cứu xử lý nước thải bằng hệ lọc cải tiến ứng dụng vật liệu tái chế từ chất thải rắn xây dựng.
VIETNAM MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF CIVIL ENGINEERING TRAN HOAI SON STUDY ON WASTEWATER TREATMENT BY ADVANCED FILTRATION SYSTEM USING RECYCLED MATERIAL FROM CONSTRUCTION SOLID WASTE Major: Environmental Engineering – Water and wastewater environmental technology Code: 62520320-2 SUMMARY OF DOCTORAL DISSERTATION Hanoi, 2023 The dissertation was completed at Hanoi University of Civil Engineering Academic Advisor 1: Assoc Prof Tran Thi Viet Nga Academic Advisor 2: Prof Ken Kawamoto Peer reviewer 1: Assoc Prof Nguyen Ngoc Dung Peer reviewer 2: Assoc Prof Nguyen Manh Khai Peer reviewer 3: Assoc Prof Do Khac Uan The doctoral dissertation will be defended at the level of the University Council of Dissertation Assessment’s meeting at Hanoi University of Civil Engineering At hour ., day month year 20… The dissertation could be found at the National Library of Vietnam and the Library of Hanoi University of Civil Engineering INTRODUCTION Research rationale The current status of wastewater treatment (WWT) in Vietnam has improved significantly, but the rate of treated wastewater is still low, reaching only 14% in urban areas, 16.1% in craft villages, and only 20 m2/g The total porosity of AAC is around 77-80%, whereas the macroporous porosity is up to 37-46%, and the ratio of pore with r ≥10 μm occupied up to 70-80% 1.2 Overview of wastewater treatment using CSW 1.2.1 Removal of heavy metals in wastewater by using CSW Construction solid waste, especially the property of concrete waste is similar to calcium silicate materials, it has a metal-rich chemical composition, large surface area, and great potential for usage as a heavy metal adsorbent The main materials studied and researched include Marble powder, laterite, concrete powder, concrete waste, autoclaved aerated concrete, Almost all of the research use synthetic wastewater with common non-metallic metals : Pb, Cd, Cr, Cu, Ni, The adsorption capacity of heavy metals in concrete waste and AAC waste fluctuates widely depending on each metal, in which Pb and Cd are suitable for removal by using concrete waste, AAC waste The adsorption capacity is up to 20-300 mg/g, the treatment efficiency reaches > 90% 1.2.2 Wastewater treatment using CSW a Wastewater treatment using CSW Dong et al (2016) used AAC waste to replace microbial carrier materials in biological filter tanks for wastewater treatment, the COD and TP removal efficiency was from 60,2 to 84,6%, and 75,8-91,3% respectively The microorganisms grow well on the surface of AAC substrates Li et al (2021) reported the filter column using waste concrete has the highest TP removal efficiency up to 87,1%, which is explained by the chemical composition containing Ca, Fe, Al ions which participate in ion exchange reactions and precipitates with phosphates The study by Bao et al (2019) showed that the biological filtration model using AAC had better performance than the model using commercial Caramite substrates (TN removal rate was 45,96% > 15,64%, the removal rate of PO43- was 72,45% > 33,97%, respectively) With the large porosity, interconnected pore network, large surface area, and rough surface of AAC, it is believed to be suitable and support the growth of microbial biofilms The growth of voids inside the AAC promotes phosphorus and nitrogen removal b Removal Phosphorus in wastewater using CSW The studies evaluating the P adsorption capacity of construction waste and AAC were carried out through static and dynamic adsorption studies Chemical adsorption is the dominant process, including ion exchange reactions to precipitate phosphates such as Ca3(PO4)2, AlPO4.2H20, MgHPO4.3H20) and HAP(Ca5(OH)(PO4)3) precipitation on the surface of the adsorbent 1.2.3 Advance filtration system for domestic wastewater treatment Advanced filtration systems in decentralized domestic wastewater treatment which combined with biological filter tanks, filter trenches, and constructed wetlands using porous and P-adsorbent materials (Filtralite P) to increase the efficiency of wastewater treatment, have been developed and widely used in developed countries These biological filter systems got removal efficiency of BOD > 80%, TP > 94%, TN: 32-64%, and wastewater after treatment met environmental protection requirements AAC is a porous material and rich in Ca, so this material has great potential as a P adsorbent as well as a microbial carrier in advanced biological filtration systems for wastewater treatment 1.3 Potential applications of AAC in wastewater treatment 1.3.1 Pollutants in wastewater can be treated with AAC a Heavy metals: detected in many types of wastewater from different fields such as mining wastewater, plating industry wastewater, wastewater from metal recycling craft villages, leachate, etc Common heavy metals in wastewater such as Pb, Cd, As, b Municipal wastewater: classified as low-strength wastewater, characterized by low organic matter content The concentrations of pollutants in MWW in Hanoi are relatively low: COD < 300 mg/L, NH4-N: 5-25 mg/L, TN: 5-55 mg/L, TP: 1,3-21,5 mg/L c Phosphorus-concentrated wastewater: Phosphate in wastewater exists in the form of organic P, soluble monophosphate, phosphate condensates, phosphates salts, and phosphates in biomass cells TP content in bioreactors ranges from 1.3-21.5 mg/L, in wastewater from 4.3-25 mg/L, and in wastewater from food processing plants (dairy) from 6-500 mg/l 1.3.2 The Potential applications of AAC in decentralized domestic wastewater treatment Popular decentralized domestic wastewater treatment: Advanced septic tank with anaerobic filter compartment; Baffled anaerobic reactor; Anaerobic filter tank; Biological filter tank; Construction wetland Which can be combined to form wastewater treatment systems working in natural conditions Construction waste such as AAC waste can be used as filter material, and microbial carrier in these works 1.4 Research orientation The research orientation of the dissertation is to demonstrate the ability to treat contaminated objects in wastewater when using AAC materials, including the ability to act as adsorbents and treat some heavy metals (Pb, Cd, As) ), phosphate; AAC's ability as a microbial carrier in biological filtration systems for bioreactor treatment From there, the research elaborates on directions for applying AAC waste in low-cost wastewater treatment systems CHAPTER SCIENTIFIC BASIS OF WATER TREATMENT PROCESS BY AAC WASTE 2.1 Theoretical basis of the adsorption process Adsorption is the accumulation of substances on the phase interface In wastewater treatment, when talking about the adsorption method, it is talking about the adsorption of dissolved pollutants at the interface between the liquid and solid phases Pollutants in water are under the influence of two forces A bond develops from the adsorption of adhesive molecules on the substrate and the resulting attractive forces, usually designated as secondary or van der Waals forces 2.1.1 The concepts of the adsorption process a Adsorption capacity is the amount of adsorbent retained per unit (𝐶 − 𝐶 ).𝑉 mass of material: q= 𝑜 𝑐𝑏 (2.1) 𝑚 b Adsorption efficiency is the ratio between the concentration of the equilibrium solution and the initial concentration of the solution: (𝐶 − 𝐶 ) 𝐸 = 𝑐𝑏 × 100 (2.2) 𝐶0 c Langmuir model The equation expresses the Langmuir model: 𝐶𝑐𝑏 1 = 𝑏𝑞 + 𝑞 𝐶𝑐𝑏 𝑞 𝑚 𝑚 (2.3) d Freundlich model The equation expresses the non-linear equation of the Freundlich 1/𝑛 isotherm model: qe = Kf.𝐶𝑒 , (n>1) (2.4) And the formula of the graph form: Logqe = logK f + logCe (2.5) 𝑛 2.1.2 Adsorption kinetics a The Pseudo–first-order (2.6) b The Pseudo–second-order (2.7) 2.1.3 The effect factors on the adsorption process in wastewater treatment The ratio between the concentration of the adsorbent solution and the adsorbent; Temperature; Adsorbent and adsorbed nature; pH 2.2 Scientific basis for adsorption/removal of heavy metals and phosphates by AAC 16 50 mg/g and did not reach the equilibrium value when investigating the Ci of 5000 mg/l When changing the investigation ratio of adsorbent (gram)/solution (ml) to 1/100, the obtained results show that the maximum adsorption capacity of Pb(II) is up to 250 mg/g Table 4.1 Summary of batch adsorption test results of AAC Heavy S/L ratio (g/mL) equilibrium Qm (mg/g) metal time (h) As 1/10 16-24 2,0-2,2 Cd 1/10 16-24 9-9,2 Pb 1/100 0,5 230 -250 4.2.2 Evaluation of the heavy metal adsorption isotherms of AAC The results show that both Langmuir and Freundlich isotherm models are suitable to describe the adsorption process of Cd and Pb, As (R2> 0,89) Table 4.2 Parameters of the adsorption isotherm of AAC Langmuir Fruendlich AAC S/L Metal b Qm R² Kf 1/n R² L/mg mg/g mg/g 3-5 0,2700 9,26 0,999 1,507 0,282 0,887 1:10 Cd 5-10 0,0641 8,96 0,999 1,222 0,296 0,892 3-5 0,0018 2,35 0,972 0,022 0,591 0,964 1:10 As 5-10 0,0016 2,13 0,963 0,013 0,653 0,945 3-5 0,0034 256,41 0,998 16,99 0,305 0,951 1:100 Pb 5-10 0,0022 232,56 0,997 11,96 0,327 0,941 Effect of grain size: The calculation results show that the AAC material with a smaller size will have a higher adsorption capacity due to its larger surface area 4.2.3 Evaluation of the heavy metal adsorption kinetic The results of the heavy metal adsorption kinetics on AAC are shown in Table 4.3 Table 4.3 Kinetics of heavy metal adsorption on AAC qe The Pseudo–secondThe Pseudo–first-order experi order AAC Metal ment q qe K1 R² e K2 R² -1 mg/g mg/g g/mg.min mg/g 17 qe The Pseudo–secondexperi order AAC Metal ment q qe K1 R² K2 R² e -1 mg/g mg/g g/mg.min mg/g 3-5 0,0076 0,956 4,20 4,90 0,0028 0,998 5,18 Cd 5-10 0,0035 0,953 3,39 4,52 0,0016 0,997 4,99 3-5 0,00253 0,833 0,38 0,93 0,0254 0,998 0,95 As 5-10 0,00207 0,832 0,13 0,75 0,0922 0,997 0,76 3-5 0,991 0,999 4,68 0,1716 0,902 2,21 4,69 Pb 1,94 4,69 5-10 0,802 0,999 4,68 0,1769 0,901 The Pseudo-second-order model well captured the measured data, the measured maximum adsorption capacity (Qm) and estimated equilibrium adsorption capacity (Qe) became almost identical, and the correlation coefficient R2 >0,99 4.2.4 Competitive Metal Adsorption When simultaneously treating Pb and Cd, the adsorption capacity and removal efficiency of Pb(II) are both higher than that of Cd(II), the hydrated radius of Pb(II) is 4.01 Å smaller than that of Cd(II) Cd(II) is 4.26 Å, so Pb(II) exerts a greater affinity for adsorbents Besides, Pb can precipitate at lower pH conditions (pH > 7) than Cd (pH > 9) Table 4.4 Results of simultaneous Pb and Cd adsorption of AAC m V Ci Ce Qe E AAC Metal (g) (ml) (mg/l) (mg/l) (mg/g) (%) Cd 10,06 100,00 508,14 108,00 3,98 78,75 3-5 Pb 4,96 99,00 10,06 100,00 504,08 5,03 Cd 100,00 508,14 171,00 3,37 66,35 10,01 5-10 Pb 4,98 98,82 10,01 100,00 504,08 5,93 4.2.5 Mechanism of heavy metals adsorption and removal of AAC a Mechanism of adsorption and removal of Pb and Cd AAC is characteristic of calcium silicate materials, so heavy metals (HMs) removal is mainly regulated by a five-step mechanism of hydrolysis, hydration, ion exchange, surface complexation, and surface precipitation Ca2+ ion exchange, surface complexation, and precipitation are the main adsorption mechanisms of HMs for AAC; The Pseudo–first-order 18 that is, the reaction of calcium silicate materials with water produces calcium silicate hydrates (C-S-H) and calcium hydroxide (CH) due to the hydration, and those substances function as adsorption sites of HMs The hydration reactions [equation (4.1)] might have formed CaOH functional groups on the edges of tobermorite Then, hydrolyzed HM ions [equation (4.2)] in reaction with those functional groups might be contributed to the HM adsorption process This could be also supported by the measured negative ζ-potentials for the AAC [1] Hydration of the adsorbent surface: (X, Si – O)2−Ca2+ + 2H2O → 2(X, Si − O) −H+ + Ca2+ + 2OH(4.1) [2] Hydrolysis of metal ions: M2+ + 2(OH)− → M(OH)2 (4.2) The result of analyzing the Ca2+ concentration before and after the experiment showed the relationships between the released Ca2+ amount and adsorbed metal amount in the, the Ca2+ was released linearly along with the metal adsorption (R2> 0,97) This suggests that chemical adsorption by ion exchange (between Ca2+ and Cd2+, Pb2+) n the hydrated adsorbent surface is the dominant adsorption mechanism of HM adsorption for tested AAC fines (equation (4.3) and (4.4)) [3] Ion exchange on the adsorbent surface: (X, Si – O) 2− Ca2+ + M2+ → (X, Si – O) 2− M2+ + Ca2+ (4.3) (X, Si – O) 2− Ca2+ + 2M(OH)+ → 2(X, Si – O)− M(OH)+ + Ca2+ (4.4) In addition, the surface precipitation of HMs can be due to the solution pH [equation (4.5)] Cd(II) and Pb(II) have the potential to precipitate as metal hydroxides when the solution pH reaches for Cd(II) and for Pb(II) It is important that the pH after adsorption became greater than pH = for Cd(II) and pH = for Pb(II), at Ci < 2000 mg/L This implies that the surface precipitation of HMs contributed partially to HM removal in water along with the ion exchange [4] Surface precipitation of metals: M2+ + 2(OH)− → M(OH)2 (4.5) At very high initial HM concentrations (Ci ≥ 2.000 mg/L), the previous reaction would not be possible because of the lower pH The adsorption shifted to multilayer-type adsorption at higher Ci> 2.000 19 mg/L With increasing Ci and metal adsorption, the pH after adsorption decreased continuously < This can be caused by high deprotonation from the calcium silicate surface, which is a result of the surface complexation formation on AAC (equation (4.6)), the dissipation of OH− due to surface precipitation might contribute to the increase in adsorption and decrease in pH after the adsorption [5] Formation of surface complexation on AAC: 2(X, Si – O) − H+ + M2+ → (X, Si – O) 2−M2+ + 2H+ (4.6) (M = Cd, Pb) b Mechanism of adsorption and removal Asen In the synthetic wastewater solution (H3AsO4), exists mainly as an anion AsO43- In an alkaline solution, AAC has also a negative charge (-) too, so AsO43- hard to adsorb on AAC As the adsorption mechanism takes place mainly in the early stage, when the hydrolysis of concrete has not yet taken place, at this time the solution (H3AsO4 ) has pH< 3, which is under pHpzc (pH 5) of AAC Then, AAC has a positive charge (+) and attracts anions AsO43-, the cation sites of Fe and Al are suitable sites for arsenic adsorption on the surface AAC As the contact time increases, the pH of the solution increases, creating an alkaline environment due to the hydrolysis of AAC At this time, AAC becomes negatively charged (-), and no longer attracts anion AsO43-, besides, Fe and Al adsorption nuclei are also limited due to iron oxide (Fe2O3: 1,72%) and Aluminum oxide (Al2O3: 2,76%) composition in AAC is low, so the As adsorption efficiency of AAC is not high c SEM and EDX analysis results The analytical results show that in the presence of heavy metals in the composition of AAC, the percentage of Pb is greater than the percentage of Cd and the percentage of As This proves that there is a process of adsorption of these HMs on AAC d Evaluation of the ability to wash away and treat materials after heavy metal adsorption The heavy metals are mostly removed in the form of hydroxide precipitates on the surface of the material, so in the alkaline environment created by AAC, the precipitates are stable, and very difficult to dissolve in water Further evaluation studies on reuse and 20 possible conditions of heavy metal leakage are needed to recommend reuse operations 4.3 Evaluation of phosphate adsorption capacity by AAC 4.3.1 Investigate the effect of reaction time The adsorption capacity P of AAC increased rapidly between and 480 and slowly increased to saturation from 480 to 1440 TP removal efficiency reaches 91%-100% respectively after 1440 minutes 4.3.2 Effect of the phosphorus concentration P removal efficiency is best when the test solution was 3-30 mg/L with a treatment efficiency of 96-100% At the equilibrium concentration of 70 mg/L, the adsorption capacity was achieved at 1,0 -1,1 mg P/g, and at this experimental concentration point, the P removal efficiency only reached 60-62% 4.3.3 Evaluation of the phosphorus adsorption isotherms and adsorption kinetic of AAC a Evaluation of the phosphorus adsorption isotherms The Langmuir model is more suitable than the Freundlich model with the correlation coefficient R2 = 0,9996 and 0,9991 compared to 0,6166 and 0,6096 respectively, that is monolayer adsorption dominates Maximum adsorption capacity (Qm, mg/g): 1,06- 1,1 mg P/g, Langmuir adsorption constant (b, L/mg): 2,81- 4,88 L/mg Freundlich adsorption constant (Kf, L/mg): 0,612- 0,702 L/mg; 1/n from 0,220 to 0,225 (0,1 70%), in small sizes, it is relatively brittle and easy to break, therefore, when used as biofilm media, it is not recommended to use too small sizes ( 28%), high 26 porosity (77-80%), large surface area (>20 m2/g) AAC concrete has pHpzc at about pH 5, so in an alkaline environment, AAC has a negative charge so it can attract positive ions in water - The adsorption process of Pb, Cd, As, and phosphate of AAC material follows Langmuir and Fruendlich isotherm model with a correlation coefficient R2 >0,9 The adsorption constant according to Langmuir model b (L/mg) when adsorbing Cd(II): 0,0641-0,270; As(V): 0,0016-0,0018; Pb(II): 0,0022-0,0034; phosphate: 2,80924,8836 The adsorption constant according to Fruendlich model Kf (mg/g) when adsorbing Cd(II): 1,222-1,507; As(V): 0,0130-0,0215; Pb(II): 11,965-16,990; phosphate: 0,612-0,702 - The Pseudo-second-order model best describes the adsorption process Pb(II), Cd(II), As(V), phosphate by AAC, with the correlation coefficient (R2 > 0,99), the measured maximum adsorption capacity (Qm) and estimated equilibrium adsorption capacity (Qe) became almost identical The constant of the Pseudo–first-order K1 (m-1) when adsorbing Cd(II): 0,0035-0,0076; As(V): 0,00207-0,00253; Pb(II): 0,1716-0,1769; phosphate: 0,0042-0,0051 The constant of the Pseudo–second-order K2 (g/mg.m) when adsorbing Cd(II): 0,00160,0028; As(V): 0,02543-0,0922; Pb(II): 0,802-0,991; phosphate: 0,0548-0,0863 - The equilibrium adsorption time of Pb is only about 0.5 hours, Cd and As is 16-24 hours, and phosphate is about hours At the experimental conditions S:L = 1:100, the maximum adsorption capacity of AAC with Pb(II) was as high as 250 mg/g, while at the experimental conditions S: L = 1:10, the maximum adsorption capacity of Cd(II): 9,2 mg/g, As(V): 2,2 mg/g, the maximum adsorption capacity of phosphate: 1,1 mg P/g (at the experimental conditions S:L = 1:25) When processing, simultaneously adsorbing Pb and Cd in priority order, the treatment efficiency of Pb(II) > Cd(II) Advanced filtration system using AAC has high efficiency in municipal wastewater treatment, the optimal hydraulic retention time of the filter system is ≥ 26 hours, the optimal circulating flow rate is 80-130%, then the efficiency COD removal, total phosphorus reached, ammonium nitrogen > 90% and total nitrogen removal efficiency > 60% 27 - Reactive biological filtration system using AAC (consists of a vertical dripped filtration tank → a horizontal filtration tank → a reactive bed filter tank) When treating domestic wastewater there is an effective range of removal COD: 60-94%, TN: 22-71%, NH4-N: 3199%, and TP: 73-100% When increasing the recirculation rate (from to 130%) and the hydraulic retention time (from 20 to 40 hours), the COD treatment efficiency increased by 10% (reaching >90%), TN increased by 35% (reaching >70%), NH4-N increased by 40% (reached >90%), TP increased by 5% (reached >90%) - The optimal operating status of the system corresponds to the water retention time from 26-40 hours, and the circulating flow from 80130%, at this time the treatment efficiency of COD, NH4-N >90%, TN > 60% TP >90%, low total suspended solids and turbidity The effluent meets the National Technical Regulation on domestic wastewater when discharging into surface water sources according to the survey parameters, especially with low TP content (