Abstract
Sewage sludge, a major byproduct of municipal wastewater treatment, presents both environmental challenges and resource utilization opportunities. In this study, biochars were prepared from sewage sludge at pyrolysis temperatures ranging from 400°C to 800°C and evaluated for their adsorption performance in removing dissolved organic carbon (DOC), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) from secondary effluent. The physicochemical properties of the biochars were characterized using Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FE-SEM), and elemental analysis. The results showed that higher pyrolysis temperatures significantly increased surface area and pore development. Although surface functional groups decreased with increasing pyrolysis temperature, the adsorption capacities improved overall. The biochar produced at 800°C (BC800) exhibited the highest removal efficiency for organic contaminants, while the biochar produced at 500°C (BC500) showed the best performance for phosphorus removal. To assess energy efficiency, the energy-normalized adsorption capacity (ENAC) was introduced. Although the biochar produced at 700°C (BC700) exhibited the highest ENAC values for COD and TN, the choice of an appropriate pyrolysis temperature that balances removal efficiency and energy performance is crucial. These findings highlight the importance of pyrolysis temperature in tailoring both the adsorption and energy performance of sewage sludge biochar. This study provides theoretical and practical insights into the use of thermally optimized biochar for sustainable wastewater treatment applications.
Key Words
adsorption; biochar; pyrolysis; sewage sludge; wastewater treatment
Address
Zikang Jiang, Chehyeun Kim, Jiwon Han, Sungjin Park, Jihyang Kweon: Department of Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul, Korea
Wonjung Song: Global Institute for Advanced Nanoscience & Technology (GIANT), Changwon National University, 20, Changwondaehak-ro, Uichang-gu, Changwon-si, Korea
Abstract
This study focuses on investigating the efficacy of corn bran, serving as a natural biosorbent, in the biosorption of Pb(II) and Cd(II) ions. The FTIR, XRD, SEM, and pHpzc were used to characterize the biosorbent. The aim of examining the impact of contact time, pH, biosorbent dose, initial concentration, and temperature was to thoroughly comprehend how these factors affect the biosorption process. The equilibrium was defined through the Langmuir and the Freundlich isotherm models. The Langmuir model exhibited a satisfactory linear correlation (R2 = 0.999 for Pb and R2 = 0.989 for Cd), than the Frundlich isotherm. At the optimal conditions for each metal, the maximum loading capacity (qmax) was 40.98 mg/g and 29.41 mg/g for Pb(II) and Cd(II) ions, respectively. These results emphasize the possibility of utilizing corn bran as a low-cost and eco-friendly material for removing lead and cadmium ions. The biosorption capacity of lead and cadmium ions in a single system was higher than in a binary system, at optimum conditions. Over 99.18 % and 97.54 % of lead and cadmium ions were successfully recovered through desorption using 0.5M HNO3. The examination of thermodynamic parameters (ΔHo, ΔSo, and ΔGo) suggests that the biosorption process is exothermic, spontaneous, and favorable.
Key Words
biosorption; cadmium; corn bran; isotherm; lead; thermodynamic parameters
Address
Salih T. Gashi: Academy of Arts and Sciences of Kosova, 10000 Prishtina, Republic of Kosovo
Bashkim S. Thaçi: University of Prishtina, Department of Chemistry, 10000 Prishtina, Republic of Kosovo
Abstract
The treatment of oil-contaminated industrial wastewater remains a critical environmental and economic challenge. This study presents a comprehensive hydrodynamic analysis and design optimization of a horizontal oil-water separator, integrating an automated control system with a theoretical trajectory model for oil droplets. This study develops a mathematical model based on force balance (buoyancy versus drag) under laminar flow conditions to predict droplet trajectories as functions of key hydrodynamic and dimensional parameters: droplet radius, inlet velocity, separator diameter, mass flow rate, and Reynolds number. The model yields explicit expressions for terminal rise velocity, rise time, residence time, and minimum required separator length. Parametric analysis reveals that smaller droplets (50 µm) dictate design requirements: at an inlet velocity of 0.005 m/s, a separator of radius 1.0 m requires a minimum length of 4.55 m to achieve complete separation, corresponding to a residence time of approximately 15 minutes. A critical mass flow rate of 0.5 kg/s is identified, below which buoyancy dominates and above which horizontal advection compromises efficiency. To maintain laminar conditions (Re < 2300), inlet velocity must not exceed 0.015 m/s for a 1.0 m diameter separator. The theoretical length-to-diameter ratio for the design droplet is approximately 2.3; applying a safety factor of 1.5–2.0 yields practical ratios of 3.4–4.6, aligning with industry standards (3:1 to 5:1). Quantitative design guidelines are summarized, including recommendations for separator diameter (≥1.0 m), maximum inlet velocity (≤0.015 m/s), and separator compartment sizing.
Address
Melouka Bellil: Faculty of Nature and Life Sciences, Mustapha Stambouli University of Mascara, 305 Mamounia Road, Mascara, Algeria/ Faculty of Sciences and Technology, Mustapha Stambouli University of Mascara, 305 Mamounia Road, Mascara, Algeria
Menouer Bennaoum: Faculty of Sciences and Technology, Mustapha Stambouli University of Mascara, 305 Mamounia Road, Mascara, Algeria
Ali Bellil: 3Department of Chemical Engineering, Faculty of Chemistry, University of Sciences and Technology of Oran-MB, El Mnaouar, 1505, Bir ElDjir, Oran, Algeria
Abstract
In this work, the feasibility of air gap membrane distillation for breaking the butyric acid/water azeotrope is examined. The azeotropic mixture was passed through the set up equipped with a porous, hydrophobic PTFE membrane. The effect of various process variables, including feed temperature, feed flow rate, coolant temperature, coolant flow rate, and air gap width on total permeate flux, selectivity of butyric acid, and permeate and retentate concentration has been studied. Furthermore, EDS and FE-SEM were used to investigate how operating time impacts morphology of membrane. The SEM image of membrane was analysed with ImageJ software to determine the pore size distribution. The experimental findings indicate that the total flux increases from 0.54 to 9.81 kg/m2⋅h on increasing the feed temperature from 40°C to 80°C mm at air gap width of 3mm. Total flux decreases from 2.75 to 1.01 kg/m2⋅h on increasing air gap width from 3 to 11 mm at flow rate of 4 l/min. In addition, the total flux decreases from 0.54 to 0.40 kg/m2⋅h when the coolant temperature is increased from 4°C to 20°C for air gap of 3 mm. It was observed that the butyric acid selectivity in the permeate was less than one, indicating the higher butyric acid concentration in retentate relative to permeate.
Key Words
air gap membrane distillation; butyric acid/water azeotrope; effect of process parameters; pore size distribution; PTFE hydrophobic membrane
Address
Rajeshwar K. Kholapure, Kailash Singh, Sushant Upadhyaya: Department of Chemical Engineering, Malaviya National Institute of Technology, Jaipur, Rajasthan 302017, India
Abstract
Anaerobic ammonia oxidation (Anammox) faces challenges in high salinity environments due to inhibited microbial activity, while upflow anaerobic sludge bed (UASB) reactors maintain a higher biomass concentration. To explore how the Anammox-USAB system responds to the high salinity (NaCl) environment, a UASB reactor seeded with heterotrophic nitrification sludge. The salinity was gradually increased from 0 to 40 g NaCl/L. The results show that, when salinity increased from 0 to 15 g NaCl/L, the conversion rate of ammonia nitrogen (NH4+-N) and total nitrogen (TN) decreased by about 25% and 22 %, respectively. At the same time, the ammonium removal load of unit sludge gradually stabilized at about 3.65 mg NH4+-N/g VSS over 10 g NaCl /L. When the salinity gradient increased to 30 g NaCl/L, microorganisms preferentially increased their polysaccharide (PS) content from 5.50 to 8.26 mg/g VSS to resist the high osmotic pressure environment. Notably, extracellular protein increased significantly, from 5.78 to 29.01 mg/g VSS to stabilize the cell structure and maintain metabolic activities at 40 g NaCl/L. With the increase of salinity, some salt-intolerant bacteria were inhibited or killed, resulting in a continuous decline in abundance while the abundance of salt-tolerant bacteria increased. The abundance of dominant species Candidatus Kuenenia and Halomonas increased from 5.97% and 0.53% to 12.29% and 12.17%, respectively. It could be seen that the Anammox-USAB system used the structural adjustment of the microbial itself and community as an adaptive strategy in response to the changes of the high-salinity environment.
Key Words
anammox; denitrification; high ammonia nitrogen wastewater; high salinity; UASB
Address
Zhang Huining, Li Yan, Ji Bixiao, Guo Xingnan, Zhang Kefeng: School of Civil Engineering, NingboTech University, Ningbo, China
Sun Keying, Pan Zhengmin: School of Civil Engineering, NingboTech University, Ningbo, China/ College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China
