Modeling of wastewater treatment by Azolla filiculoides using response surface methodology.

EFEITO DA TAXA DE AERAÇÃO NO DESEMPENHO DE ALAGADOS CONSTRUÍDOS AERADOS INTERMITENTEMENTE JOÃO GABRIEL THOMAZ QUELUZ; LAUREN NOZOMI MARQUES YABUKI E MARCELO LOUREIRO GARCIA Instituto de Geociências e Ciências Extas, Universidade Estadual Paulista, Avenida 24 A,1515, CEP: 13506-900, Rio Claro, SP, Brasil. queluz@fca.unesp.br; lauren.yabuki@unesp.br; marcelo.garcia@unesp.br 1 RESUMO O presente trabalho foi conduzido com o objetivo de avaliar o efeito de diferentes taxas de aeração na remoção de nitrogênio total (NT) e demanda química de oxigênio (DQO) em alagados construídos de fluxo subsuperficial horizontal (ACFH) aerados intermitentemente. Para isso, foram avaliados quatro ACFH em escala piloto utilizando diferentes taxas de aeração (0; 2; 5 e 10 L min-1) com intervalo de aeração intermitente fixo de 3 h d-1 (1h com aeração/7 horas sem aeração). Os sistemas receberam 8,6 L d-1 de efluente sintético, resultando em tempo de detenção hidráulica de 3 dias. Os resultados mostram que os ACFH aerados intermitentemente apresentaram elevada eficiência na remoção de DQO (>97%), NT (>80%) e NH4+ (>97%), enquanto o ACFH sem aeração apresentou menor eficiência na remoção de DQO (93,9%), NT (48,8%) e NH4+ (57,7%). Adicionalmente, os resultados também mostram que os três ACFH aerados intermitentemente obtiveram desempenho similar na remoção de DQO, NT e NH4+. Finalmente, os resultados permitem concluir que a aeração intermitente permite a ocorrência simultânea da nitrificação e da desnitrificação, aprimorando, assim, o desempenho dos ACFH na remoção de NT. Entretanto, o uso de diferentes taxas de aeração não altera a eficiência de remoção de NT e DQO. Palavras-chave: aeração artificial, remoção de DQO, remoção de nitrogênio. QUELUZ, J. G. T.; YABUKI, L. N. M.; GARCIA, M. L. EFFECT OF AERATION RATE ON THE PERFORMANCE OF INTERMITTENTLY AERATED CONSTRUCTED WETLAND 2 ABSTRACT The aim of the present work was to evaluate the effect of different aeration rates on the removal of total nitrogen (TN) and chemical oxygen demand (COD) in intermittently aerated horizontal subsurface flow constructed wetlands (HFCW). Four pilot-scale HFCWs were evaluated using different aeration rates (0, 2, 5, and 10 L min-1) with a fixed intermittent aeration interval of 3 h d-1 (1 h with aeration / 7 h without aeration). The HFCWs received 8.6 L d-1 of synthetic effluent, resulting in a hydraulic retention time of 3 days. The results show that intermittently aerated HFCWs were highly efficient in removing COD (>97%), TN (>80%) and NH4+ (>97%), while the HFCW without aeration showed lower efficiencies in the removal of COD (93.9%), TN (48.8%), and NH4+ (57.7%). In addition, the results also show that the three intermittently aerated HFCW achieved similar performance in the removal of COD, TN, and NH4+. Finally, the results indicate that intermittent aeration allows the simultaneous occurrence of nitrification and denitrification, thus improving the performance of HFCW in removing TN. However, the use of different aeration rates does not alter COD and TN removal efficiencies. Keywords: artificial aeration, COD removal, the nitrogen removal.

In this study, the effect of three operating parameters, i.e., the first/second volumetric feeding ratio (milliliters/milliliters), the first anaerobic/aerobic (an/oxic) time ratio (minute/minute), and the second an/oxic time ratio (minute/minute), on the performance of a two-step fed sequencing batch reactor (SBR) system to treat swine wastewater for nutrients removal was examined. Central Composite Design, coupled with Response Surface Methodology, was employed to test these parameters at five levels in order to optimize the SBR to achieve the best removal efficiencies for six response variables including total nitrogen (TN), ammonium nitrogen (NH4-N), total phosphorus (TP), dissolved phosphorus (DP), chemical oxygen demand (COD), and biochemical oxygen demand (BOD). The results showed that the three parameters investigated had significant impact on all the response variables (TN, NH4-N, TP, DP, COD, and BOD), although the highest removal efficiency for each individual responses was associated with different combination of the three parameters. The maximum TN, NH4-N, TP, DP, COD, and BOD removal efficiencies of 96.38%, 95.38%, 93.62%, 94.3%, 95.26%, and 92.84% were obtained at the optimal first/second volumetric feeding ratio, first an/oxic time ratio, and second an/oxic time ratio of 3.23, 0.4, and 0.8 for TN; 2.64, 0.72, and 0.76 for NH4-N; 3.08, 1.16, and 1.07 for TP; 1.32, 0.81, and 1.0 for DP; 2.57, 0.96, and 1.12 for COD; and 1.62, 0.64, and 1.61 for BOD, respectively. Good linear relationships between the predicted and observed results for all the response variables were observed.

The polluted water of Chiang Mai’s iconic moat negatively impacts the city’s image, affecting perceptions among both residents and visitors. Furthermore, contamination of the moat poses significant risks to public health, underscoring the urgent need for cost-effective and sustainable remediation strategies. To achieve this goal, the implementation of bio-phytoremediation, using vetiver grass (Chrysopogon zizanioides L. Roberty), was proposed as a promising solution to this problem. This study aimed to assess the effectiveness of vetiver grass, in combination with aeration, for removal of chemical oxygen demand (COD) and nutrients from the moat’s water. Water samples collected from the moat were used in experimental setups, where hydroponically grown vetiver grass was cultivated on floating platforms, with some setups incorporating aeration and others without. A control group without vetiver platforms or aeration was also included. The results obtained demonstrated that the combination of vetiver grass and aeration yielded the highest removal efficiencies, achieving 96.38% COD removal (kCOD = -5×10-4 h-1), 91.57% NH3-N removal, and 70.59% total nitrogen (TN) removal (kTN = -0.115 h-1). Total phosphorus (TP) removal efficiency was approximately 70% for both the vetiver platform with aeration, and the vetiver platform alone (kTP = -1×10-4 h-1). This study demonstrates the potential of vetiver grass as an effective bio-phytoremediation agent for the treatment of urban surface water. Implementing this approach in Chiang Mai’s moat could improve the city’s appearance, protect public health, promote sustainable water management, and do so in a cost-effective manner.

Effect of operating parameters on the performance of sediment microbial fuel cell treating aquaculture water

Three different treatment technologies, namely mono-algae culture, algal-bacterial culture, and algal-fungal culture, were applied to remove pollutants form synthetic domestic sewage and to remove CO2 from biogas in a photobioreactor. The effects of different initial influent C/N ratios on microalgal growth rates and pollutants removal efficiencies by the three microalgal cultures were investigated. The best biogas upgrading and synthetic domestic sewage pollutants removal effect was achieved in the algal-fungal system at the influent C/N ratio of 5:1. At the influent C/N ratio of 5:1, the algal-fungal system achieved the highest mean chemical oxygen demand (COD) removal efficiency of 81.92% and total phosphorus (TP) removal efficiency of 81.52%, respectively, while the algal-bacterial system demonstrated the highest mean total nitrogen (TN) removal efficiency of 82.28%. The average CH4 concentration in upgraded biogas and the removal efficiencies of COD, TN, and TP were 93.25 ± 3.84% (v/v), 80.23 ± 3.92%, 75.85 ± 6.61%, and 78.41 ± 3.98%, respectively. These results will provide a reference for wastewater purification ad biogas upgrading with microalgae based technology.

ABSTRACTA combined anaerobic-aerobic bio-filter technology was used for field treatment of high-organic-load domestic wastewater with coal cinder as the bio-filter medium. The effects of parameters, including hydraulic retention time (HRT) and backflow ratio, on the decrease in the chemical oxygen demand (COD), NH3-N, total nitrogen (TN), total phosphorus (TP), and turbidity were investigated. The results showed the obvious influence of the HRT and ratio of backflow on wastewater treatment. Under the optimal HRT condition of 18 h, the removal efficiencies of COD, NH3-N, TN, TP, and turbidity were 67.9%, 95.6%, 30.4%, 65.6%, and 83.8%, respectively. When the backflow ratio (2:1) was added to the treatment system, the TN removal obviously increased, and the removal efficiencies of COD, NH3-N, TN, TP, and turbidity were 88.1%, 91.7%, 69.9%, 69.6%, and 97.5%, respectively. These results indicated that the combined technology has the potential as a treatment method for high-organic-load domestic wastewater.

BACKGROUND: This study considers batch treatment of saline wastewater in an upflow anaerobic packed bed reactor by salt tolerant anaerobic organisms Halanaerobium lacusrosei.RESULTS: The effects of initial chemical oxygen demand (COD) concentration (COD0 = 1880–9570 mg L−1), salt concentration ([NaCl] = 30–100 g L−1) and liquid upflow velocity (Vup = 1.0–8.5 m h−1) on COD removal from salt (NaCl)‐containing synthetic wastewater were investigated. The results indicated that initial COD concentration significantly affects the effluent COD concentration and removal efficiency. COD removal was around 87% at about COD0 = 1880 mg L−1, and efficiency decreased to 43% on increasing COD0 to 9570 mg L−1 at 20 g L−1 salt concentration. COD removal was in the range 50–60% for [NaCl] = 30–60 g L−1 at COD0 = 5200 ± .100 mg L−1. However, removal efficiency dropped to 10% when salt concentration was increased to 100 g L−1. Increasing liquid upflow velocity from Vup = 1.0 m h−1 to 8.5 m h−1 provided a substantial improvement in COD removal. COD concentration decreased from 4343 mg L−1 to 321 mg L−1 at Vup = 8.5 m h−1, resulting in over 92% COD removal at 30 g L−1 salt‐containing synthetic wastewater.CONCLUSION: The experimental results showed that anaerobic treatment of saline wastewater is possible and could result in efficient COD removal by the utilization of halophilic anaerobic bacteria. Copyright © 2008 Society of Chemical Industry

Electrocoagulation of wastewater using aluminum, iron, and magnesium electrodes.

A bioelectrochemical-system-based trickling filter reactor for wastewater treatment

Reclaimed wastewater reuse for irrigation to crop plants is evaluated in a laboratory-scale experiment to assess growth and water saving potential from natural resources. A prototype laboratory-scale treatment plant was established for this purpose with suspended and attached growth configurations. Chakwal wheat variety was selected to examine growth parameters. The removal of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were evaluated to check the quality of treated water. It was found that a suspended growth sequencing batch bioreactor (SGSBBR) achieved 97% ± 2 removal efficiency over a 4 h hydraulic retention time (HRT). For an attached growth sequencing batch bioreactor (AGSBBR) results showed 98% ± 2 removal efficiencies with polyurethane. TN and TP removal efficiency was 58.7 ± 3% and 64 ± 4.8% in SGSBBR, 53 ± 0.17% and 67 ± 2.7% in polyurethane. AGSBBR enhanced performance with AGSBBR may be due to enforced anoxic/aerobic conditions in the inner layers of biofilm formed on biocarriers which facilitate the required metabolic conditions for treating high strength wastewater. Plant growth was visibly greater in SGSBBR treated wastewater than AGSBBR because of less nutrient removal.

This study aimed to develop a low cost bioreactor process to efficiently remove organic compounds and nutrients from on-site wastewater treatment systems. A laboratory-scale anaerobic membrane-aerated biofilm bioreactor (ANMABR) using a gas-permeable silicone tubing covered with non-woven fabrics was constructed to evaluate the efficiency of chemical oxygen demand (COD) and nitrogen removal in the system. After 250 days of continuous reactor operation, the experiment results showed consistent COD and NH 4 —N removal efficiencies at 89±6 and 82±5%, respectively. The total nitrogen (TN) removal efficiency was 64±8% with an effluent average total nitrogen concentration of 11 mg/L. From day 89 to day 120 the biofilm reactor experienced a shock load running with C/N ratio of 2:1 with influent NH 4 —N increased to 150 mg/L. The COD removal efficiency was not affected after the shock load, but NH 4 —N and TN removal efficiencies were decreased down to 44 and 22%, respectively. This study demonstrated that gas-permeable tubing/membrane could be used to treat wastewater containing low organic and nitrogen loadings from on-site wastewater treatment systems. Improvement is still needed under the shock loading conditions for on-site wastewater treatment systems.

Photocatalytic removal of ammonium-nitrogen (-N) from water using solar energy is an approach of high interest and applicability due to the convenience in application. ZnO has a great potential in photocatalytic decomposition of -N and conversion of this nutrient to under visible light irradiations. However the applicability of pristine ZnO though is limited due to its reduced capacity to utilize light from natural light. Herein, we report a two-step ZnO-modified strategy (Cu-doped ZnO nanoparticles, immobilized on reduced graphene oxide (rGO) sheets) for the promotion of photocatalytic degradation of -N under visible light. UV-Vis spectra showed that the Cu/ZnO/rGO can be highly efficient in the utilization of photons from the visible region. Hence, Cu/ZnO/rGO managed to demonstrate adequate photocatalytic activity and effective -N removal from water under visible light compared to single ZnO. Specifically, up to 83.1% of -N (initial concentration 50 mg·L−1, catalyst dosage 2 g·L−1, pH 10) was removed within 2 h retention time under Xe lamp irradiation. From the catalysis, the major by-product was N2. The high ammonia degradation efficiency from the ZnO/Cu/rGO is attributed to the improvement of the reactive oxygen species (ROSs) production efficiency and the further activation of the interfacial catalytic sites. This study also demonstrated that such nanocomposite is a recyclable agent. Its -N removal capacity remained effective even after five batch cycles. In addition, Cu/ZnO/rGO was applied to treat real domestic wastewater, and it was found that chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removal efficiencies can reach 84.3, 80.7, and 90.3%, respectively. Thus, Cu/ZnO/rGO in the presence of solar light can be a promising photocatalyst in the field of wastewater treatment.

Increasingly, environmental regulations are demanding more exacting chemical oxygen demand (COD) and nitrogen removal from wastewater, which come at a high economic cost. A very simple novel bioreactor, the micro-pressure swirl reactor (MPSR), can improve the dissolution and distribution of oxygen by the introduced micro-pressure swirl. Comparison with a conventional sequencing batch reactor (SBR) over 76 days of operation showed that this method can enhance simultaneous COD and nitrogen removal. By installing an aeration diffuser on one side of the two-dimensional MPSR, a swirl formed in the bioreactor that extended the retention time of the air bubbles. This unique flow regime, combined with the micro-pressure caused by the elevated water surface at the bubble outflow point, resulted in a higher level of dissolved oxygen (DO) in the MPSR. Aerobic and anaerobic zones that created appropriate conditions for simultaneous COD and nitrogen removal also formed in the MPSR. As the organic loading rate increased from 0.29 to 1.68 g COD/(L · day) over the test period, the COD removal efficiencies of the MPSR were generally 10-20 % greater than those of the SBR. In particular, the total nitrogen (TN) removal efficiencies of the MPSR and SBR were 40-50 and 20-35 %, respectively, whereas the TN concentrations in the MPSR effluent were always around 10 mg/L lower than those of the SBR. Further, because of the unique DO distribution, the bacterial species in the MPSR were more diverse and contributed to enhanced TN removal.

Side-by-side comparison of horizontal subsurface flow and free water surface flow constructed wetlands and artificial neural network (ANN) modelling approach

Enhanced nutrient removal from aquaculture wastewater using optimized constructed wetlands: A comprehensive screening of microbial complexes, substrates, and macrophytes