COD Loading Rate Research Articles

Machine learning model optimization for removal of steroid hormones from wastewater

In the past few decades, there has been a significant focus on detecting steroid hormones in aquatic environments due to their influence on the endocrine system. Most compounds of these pollutants are the natural steroidal estrogens, i.e., estrone (E1), 17β-Estradiol (E2), and the synthetic estrogen 17α-Ethinylestradiol (EE2). The Moving-Bed Biofilm Reactor (MBBR) technique is appropriate for eliminating steroid hormones. This study centers on creating a model to estimate the effectiveness of the MBBR system regarding its ability to eliminate E1, E2, and EE2. The results were modeled with artificial neural networks (ANNs). The Particle Warm Optimization (PSO) and Levenberg Marquardt (LM) algorithms were selected for network training. The models incorporated five input parameters, encompassing the COD loading rate, initial levels of E1, E2, and EE2 steroid hormones, and Hydraulic Retention Time (HRT). The optimum removal conditions (three steroid hormones and COD) were determined using the optimized ANN based on both PSO and LM algorithms. The optimal transfer functions for the hidden and output layers were identified as tan-sigmoid and linear, respectively. The best ANN structures (Neurons in input, hidden, and output layers) and correlation coefficients (R) were 5:9:4, with R = 0.9978, and 5:10:4, with R = 0.9982 for the trained networks with LM and PSO algorithms, respectively. Eventually, the input parameters' importance was ranked using sensitivity analysis (SA) through Pearson correlation and developed ANNs.

A series anaerobic-aerobic down-flow hanging sponge (DHS) reactor for the treatment of palm oil mill effluent (POME)

Palm oil mill effluent (POME) contains very high organic compounds that must be treated before being discharged into the environment. Pond technology has been widely used for the treatment of POME; however, it requires a huge area of land. Down-flow hanging sponge (DHS) reactor has shown a high pollutant removal efficiency, less energy, and land area requirement. This study aimed to investigate the performance of a series of anaerobic (R3) and aerobic (R4) DHS reactors in treating POME. The reactor was continuously supplied with POME in three different phases for 165 days. The COD loading rate was set at 3.06, 6.12, and 12.24 kg-COD/m³·day in Phase 1, Phase 2, and Phase 3, respectively. Hydraulic retention time (HRT) was set at 47 min and 50 min, in R3 and R4, respectively. The reactors showed good performance for pollutant removal efficiency, especially COD. In Phase 1, the average COD removal rate was 2.68 and 0.27 kg-COD/m³·d in R3 and R4, respectively. In Phase 2, when the COD loading rate was increased, the average COD removal rate achieved 4.12 and 1.53 kg-COD/m³·d in R3 and R4, respectively. In Phase 3, the COD loading rate was doubled to 12.24 kg-COD/m³·day and the average COD removal rate of 5.81 and 2.90 kg-COD/m³·d was achieved in R3 and R4, respectively. During operation, the concentration of nitrate fluctuated in R4, which indicated that nitrification had occurred. Phosphate could be reduced in R3, but only a small portion could be removed in R4. Total suspended solids (TSS) could be effectively removed in R4. These results revealed that a combination of anaerobic-aerobic DHS reactors showed good performance in removing pollutants such as COD and TSS. Therefore, DHS technology can be used as a polishing treatment for treated POME.

Palm oil mill effluent (POME) treatment using a combined anaerobic-microalgae down-flow hanging sponge (DHS) reactor

Palm oil mill effluent (POME) generated from the production of palm oil contains organic and inorganic contaminants that can be a nutrient source for microorganisms such as bacteria, fungi, and microalgae. In this study, POME was treated using a combined anaerobic (R1) and microalgae (R2) in down-flow hanging sponge (DHS) reactor. Chlorella pyrenoidosa was immobilized in sponge carriers of R2 and LED lights were used for 12 hours per day to support microalgae growth. The DHS reactors were continuously operated for 165 days in three phases with different COD loading rates, namely 3, 6, and 12 kg-COD/m³·day in Phase 1, Phase 2, and Phase 3, respectively. The hydraulic retention time (HRT) was set at 46 min and 52 min in R1 and R2, respectively. The highest COD removal rate was achieved at 6.93 kg-COD/m³·day and 4.85 kg-COD/m³·day in R1 and R2, respectively. In addition, maximum phosphate removal was 68% in both reactors. Increased concentration of nitrate in R-2 indicated that nitrification may occur in the reactor. The pH of R1 effluent was relatively stable at neutral conditions, while the pH value of R2 effluent slightly increased. Based on visual observation, bacteria biofilm also grew in the microalgae reactor (R2). Synergistic bacteria-microalgae may play an important role in pollutant removal. The results of this study show that a combined anaerobic and microalgae DHS reactor can be used as an alternative for POME treatment because they have a shorter HRT and can be applied in a small area.

Identification of dissimilatory nitrate reduction to ammonium (DNRA) and denitrification in the dynamic cake layer of a full-scale anoixc dynamic membrane bioreactor for treating hotel laundry wastewater

Identification of dissimilatory nitrate reduction to ammonium (DNRA) and denitrification in the dynamic cake layer of a full-scale anoixc dynamic membrane bioreactor (AnDMBR) for treating hotel laundry wastewater was studied. A series of experiments were conducted to understand the contributions of DNRA and canonical denitrification activities in the dynamic cake layer of the AnDMBR. The dynamic cake layer developed included two phases - a steady transmembrane pressure (TMP) increase at 0.24 kPa/day followed by a sharp TMP jump at 1.26 kPa/day four to five days after the AnDMBR start-up. The nitrogen mass balance results showed that canonical denitrification was predominant during the development of the dynamic cake layer. However, DNRA activity and accumulation of bacteria equipped with a complete DNRA pathway showed a positive correlation to the development of the dynamic cake layer. Our metagenomic analysis identified an approximately 18% of the dynamic cake layer bacterial community has a complete DNRA pathway. Pannonibacter (1%), Thauera (0.8%) and Pseudomonas (3%) contained all genes encoding for funcional enzymes of both DNRA (nitrate reductase and DNRA nitrite reductase) and denitrification (nitrate reductase, nitrous oxide reductase and nitric oxide reductase). No other metagenome-assembled genomes (MAGs) possessed a complete cononical denitrification pathway, indicating food-chain-like interactions of denitrifiers in the dynamic cake layer. We found that COD loading rate could be used to control DNRA and canonical denitrification activities during the dynamic cake layer formation.

Anaerobic Treatment for Palm Oil Mill Effluent Using Covered In-the Ground Anaerobic Reactor (CIGAR)

Wastewater from crude palm oil mills contains high organic matter, which potentially produces biogas through anaerobic digestion processes. The design and operation of an anaerobic bioreactor require a good understanding of the reaction kinetic in the bioreactor. This study aimed to evaluate the biogas production from POME and to determine the kinetic parameters of microbial growth and the substrate utilization rates in a CIGAR. An experiment was conducted using a 5-m3 bioreactor with a working volume of 4.4 m3. Wastewater from the Bekri palm oil mill was stored in a 5-m3 tank. After stabilization, the wastewater was loaded into the reactor at a rate of 100 to 250 L/d, corresponding to a COD loading rate of 1.373-3.097 kg·m-3.d-1, and an HRT of 18-44 days. Monod, Contois, Moser, and Shuler kinetic models were evaluated. The results showed that the Shuler model performed best for microbial activities, while the first order reaction model performed best for the substrate utilization kinetic. The maximum specific growth rate (μmax) for the Shuler model was 0.052 d-1 and the saturation constant (Kso) was 0.119. The maximum substrate utilization rate constant (ks) was 2.183 d-1 and biomass yield (Yx/s) 0.024 kg/kg. The maximum average efficiency of anaerobic degradation (34.4%) occurred at a feeding rate of 100 L/d with methane yield of 0.120 Nm3/kg of removed COD. This value is relatively low compared to the maximum potential of 0.350 Nm3/kg CODr.

The performance of simultaneous partial nitritation, anammox, denitrification, and COD oxidation (SNADCO) method in the treatment of digested effluent of fish processing wastewater

The simultaneous partial nitritation, anammox, denitrification, and COD oxidation (SNADCO) method was successfully carried out in an air-lift moving bed biofilm reactor (AL-MBBR) with cylinders carriers for the treatment of digested fish processing wastewater (FPW). Synthetic wastewater was used as substrate at stage 1. It changed into the digested FPW with dilution variation in order to increase the nitrogen and COD loading rates. With influent concentration of NH4+-N of 909 ± 101 mg-N/L and COD of 731 ± 26 mg/L, the nitrogen removal efficiency was 86.8% (nitrogen loading rate of 1.21 g-TN/L/d) and the COD removal efficiency was 50.5% (COD loading rate at 0.98 g-COD/L/d). This study showed that the process has the advantages in treating the real high ammonia concentration of digested wastewater containing organic compounds. The nitritation and anammox route was predominant in nitrogen removal, while COD oxidation and microbe proliferation played the main role in COD removal.

Biological treatment of palm oil mill effluent by using a downflow hanging sponge reactor

The performance of biological treatment using a downflow hanging sponge reactor as post-treatment of agro-industrial wastewater has been recognized worldwide. However, the effectiveness of the system in treating POME is remain unknown. Therefore, with this background in mind, an anaerobic treatment operated at COD loading rate of 0.4-0.6 kg/m3/day, HRT of 2 hours and input pH of 7.6 was run using a DHS reactor packed with sponge media for the treatment of POME. During the study, the output concentration performances of COD (32-58%), Colour (41-76%), ammoniacal nitrogen (66-92%) and phosphate (54-87%) were recorded. These results indicate comparable performances with the existing biological treatment system. However, it also offered additional credits in-term of fouling and clogging issues, practically as well as lower cost and energy consumption. Thus, it will be great to have a system that is capable to provide a simple technology which is affordable to various industrial scales.

Textile wastewater treatment using horizontal flow constructed wetland and effect of length of flow in operation efficiency

Textile wastewater treatment is a challenging process due to its high-intensity color and high COD value. In this study, the effect of design parameters of constructed wetlands in the treatment of synthetic textile dyeing bath effluent using horizontal flow constructed wetlands was explored. The effect of length of flow through the wetlands and hydraulic retention time in pollutant removal were analyzed. Two wetland reactors, one baffled, and the other non-baffled reactors were operated with varying lengths of flow and HRT (3 days to 7 days). It was observed that the maximum color (72 ± 2%) and COD removal (85 ± 3%) occurred in the baffled reactor at a dye loading rate of 1.15 g/m2 d and COD loading rate of 10.3 g/m2 d. The pH change and sulfate removal rates (34 ± 2%) at a sulfate loading rate of 2.8 g/m2 d were similar in both reactors. Overall, the length of flow affected slightly the performance of wetland reactors for color and COD removal. The study suggests that there exists a need for the development of proper design parameters for the effective use of constructed wetlands in the treatment of wastewater.

Effects of the reactor volumetric ratio and recycle ratio on the methane and energy productivity of a three-step anaerobic sequencing batch reactor (3S-ASBR) treating ethanol wastewater

A new three-step anaerobic sequencing batch reactor (3S-ASBR) was developed to enhance methane productivity and energy yield by varying the reactor volumetric and recycle ratios. The pH of the first reactor (R1) was maintained at 5.5, whereas that of the others (R2/R3) was not controlled. The effluent from R3 was recirculated to R1 to amplify the alkalinity and lessen the NaOH quantity for pH regulation. The 3S-ASBR was continually operated to attain a steady state at a moderate COD loading rate (10 kg/m3d) with different reactor volumetric ratios under 37 °C, a fixed total liquid volume of 30 L and a constant recycle ratio of unity. A R1:R2:R3 volumetric ratio of 1:1.5:5 gave the highest COD reduction (90%) and yielded 343 mL CH4/g COD applied with an overall energy extraction efficiency of up to 66%. This volumetric ratio corresponded well to the generation time ratio of the microbes involved in the hydrolysis/acidogenesis, acetogenesis, and methanogenesis steps which can be applied to scale up both 3S-ASBR and three-step/stage upflow anaerobic sludge blanket (3S-UASB) systems. The low pH level (5.5) in R1 was responsible for maintaining adequate amounts of all micronutrients in the system, causing both high microbial concentrations and activities. This was because the lower the solution pH, the higher the fraction of produced H2S to be in the gaseous phase, causing the lower the amounts of micronutrients to be precipitated chemically.

High methanogenic activity of a three-stage UASB in relation to the granular sludge formation

A new UASB (upflow anaerobic sludge blanket) system with three-stage concept and granular sludge formation was developed to provide a very high process activity, in terms of a high energy yield and a large optimum COD loading rate, from ethanol wastewater at 37 °C and a controlled pH of 5.5 in the first bioreactor with recirculation of the final overflow from the third to the first two bioreactors to lower the amount of sodium hydroxide used for pH control in the first bioreactor and to increase the total alkalinity of the whole system. The proper volumetric ratio of the three-stage UASB with flocculant sludge provided the dominance of the three sequencial steps of acidogenesis, acetognesis and methanogenesis to occur in the respective bioreactors, causing a higher process performance and giving the optimum COD loading rate of 15 kg/m3d. The presence of granular sludge in all three bioreactors, resulted from the slow increment in the COD loading rate over a long operation period with high levels of microbial concentrations in all three bioreactors under the continuous feed operation and steady sate condition. This further increased the optimum COD loading rate from 15 to 25 kg/m3d (calculated from the total liquid volume) with an extremely high energy yield of 11,740 kJ/kg COD applied.

Rapid degradation of 2,4-dichloronitrobenzene in single-chamber microbial electrolysis cell with pre-acclimated bioanode: A comprehensive assessment

2,4-dichloronitrobenzene (DClNB) as a typical refractory pollutant, exists in multifarious industrial wastewater widely and poses a serious threat to the environment. An ion exchange membrane (IEM)-free microbial electrolysis cell (MEC) with pre-acclimated bioanode was built and evaluated systematically for treatment of DClNB containing wastewater. Results showed that compared with the non-acclimated or IEM-equipped MECs, the pre-acclimated IEM-free MECs had the best DClNB removal efficiency of 91.3% under COD and DClNB loading rates of nearly 1000 kg m−3 d−1 and 100 g m−3 d−1. Both of anode pre-acclimation and IEM removal reduced the electron transfer resistance by 71.1 and 194.5 Ω, respectively. Compared to the pre-acclimated IEM-equipped MEC, the cathode current efficiency of pre-acclimated IEM-free MEC increased by 13.7%. Analysis of live/dead cell staining indicated that a higher proportion of live cells was observed in the acclimated anode biofilm (66.1% vs. 47.3%), and the detoxification of DClNB in the pre-acclimated IEM-free MECs was significantly better (p < 0.05) than those of non-acclimated or IEM-equipped MECs. This study contributes to the performance improvement of the MEC process for treatment of toxic industrial wastewater.

Performance of an up-flow anaerobic bio-electrochemical system (UBES) for treating sulfamethoxazole (SMX) antibiotic wastewater

This paper focused on the feasibility and performance of an up-flow anaerobic bio-electrochemical system (UBES) for treating sulfamethoxazole (SMX) antibiotic wastewater at different COD loading rates (LRs) from 2.02 ± 0.13 to 6.09 ± 0.14 kgCOD/(m3·d). Open-circuit UBES had a lower average COD removal rate of 62.4 ± 4.7% in Run2, and the accumulation of volatile fatty acid (VFA) was occurred. However, closed-circuit UBES can alleviate the accumulation of VFA (which was decreased from 720.4 to 102.4 mg/L), the highest average COD, SMX removal rates were 85.7 ± 3.2% and 73.7 ± 2.0%, respectively. The closed-circuit UBES can withstand more than 3 times LR than open-circuit UBES, which proved that the ability of microorganisms to resist toxic substance stress was strengthened. And the mathematical models for pollutants removal rate were established and well interpreted the results, which also can guide the operation of UBES.

High rate of biological removal of sulfate, organic matter, and metals in UASB reactor to treat synthetic acid mine drainage and cheese whey wastewater as carbon source.

The anaerobic biological treatment of sulfate-rich effluents, such as acid mine drainage (AMD), is mediated by sulfate-reducing bacteria (SRB). This process involves the reduction of sulfates in the presence of an electron donor. Complex carbon compounds can be used as electron donors. In the present study, was used an upflow anaerobic sludge blanket (UASB) reactor to co-treat a low-pH synthetic AMD and cheese whey wastewater (CWW). Were observed higher sulfate and COD removal rates (1,114±88 and 1,214±128mgL-1 day-1 , respectively) at higher sulfate and applied COD loading rates (1,500mgL-1 day-1 ). The overall pH of the effluent remained above 6.4 without any bicarbonate supplementation. Almost 100% of the Fe, Zn, and Cu was removed and the presence of metals improved the process. The use of a single reactor to treat AMD and CWW is promising. PRACTITIONER POINTS: Wastewater cheese whey was electron donor for treating acid mine drainage in an UASB reactor. Metals additions in the system indicated an increased removal of COD. About 99% of the metals were removed with the treatment.

Does duckweed ponds used for wastewater treatment emit or sequester greenhouse gases?

The reduction of greenhouse gases (GHG) emissions is important challenge in the wastewater treatment plants. In this way, the present study aimed to evaluate the GHG emissions and carbon dioxide fixation by duckweed ponds (DWP) applied to treat municipal wastewater in a polishing stage. Two pilot DWP (3000 L) were operated in a series with real wastewater receiving a flow rate of 200 L d-1 and organic load rate of 39 g COD ha-1 d-1. Beyond the standard physicochemical parameters for wastewater monitoring, the gases emissions from pond surface were measures by using a static flux chamber with infrared probes installed inside to detect CO2 and CH4 concentration. Operating the DWP with a load of 18.1 kg TN ha-1 d-1 and 2 kg TP ha-1 d-1, across 425 days of monitoring, higher COD and nutrient removal efficiency was identified (79%, 93% and 84% for COD, TN and TP, respectively). The CO2 emission rate ranged from 3048 to 6017 mg CO2 m-2 d-1 and the fixation rate ranged from 19,592 to 42,052 mg CO2 m-2 d-1. Methane emission was not detected (less than 0.1%). Moreover, low abundance of archaeal community was identified in both DWP. The results showed that in presented conditions, under low COD loading rate DWP could fix at least three times more CO2 than it emits, highlighting the sustainability of this natural technology.

Material inter-recycling for advanced nitrogen and residual COD removal from bio-treated coking wastewater through autotrophic denitrification

For wastewaters containing high strength sulfide and nitrogen (e.g. coking wastewater), sulfide might be precipitated and recovered using ferrous salt. This study systematically investigated the feasibility of recovered and precipitated FeS (comparing to commercial FeS minerals) to support autotrophic denitrification for advance nitrogen removal from bio-treated coking wastewater in fluidized bed reactors. The reactor with precipitated FeS could achieve simultaneous removal of NO3−-N and inert COD with high efficiencies of around 96.3% and 30.5%, at NO3−-N and COD loading rates of 4.18 mg·L−1·h−1 and 8.06 mg·L−1·h−1, respectively. Whereas, the performance of commercial FeS reduced gradually and irreversibly after two days, which became completely ineffective after 40 days. Thiobacillus and Rhodanobacter dominated the biomass, which played a key role in the FeS-based denitrification process. This material inter-recycling concept benefits an advance and more sustainable treatment of wastewaters with high strength sulfide and nitrogen.

Feasibility Studies on the Treatment of Dairy Wastewater Using Rotating Biological Contactor (RBC) Under Variable Experimental Conditions

There are numerous methods for treatment of effluents of dairy waste/waste water. Rotating Biological Contactors (RBC) is one of the most popular because of its easy operation, low energy usage and less area requirement. RBC is an aerobic treatment process. In the present study RBC is used to treat dairy waste water. Three stage RBC with each tank of total volume 10 litres and working volume of 8 litres is taken and kept in series. Rotational speed of discs is fixed to 40 rpm and with 40% submergence throughout the study. Biofilm formation has been taken because of continuous rotation of RBC discs. Hydraulic Retention Time [HRT] varies with 48,24,12,8 and 4 hrs for initial COD concentration 1000mg/l. Optimum HRT is fixed for 8hrs as per the study. With increasing loading rate of COD to 1500mg/l efficiency is reduced. To fix the COD loading rate, 1000 mg/l was increased to 1100mg/l, 1200 mg/l,1300 mg/l and 1400mg/l. With initial COD concentration of 1000mg/l with different HRT it is found 8hrs with COD removal efficiency (tank 1+tank 2+ tanks 3) was 85%. It is evident from the results that for an optimum HRT of 8 hrs, optimum COD loading rate is 1300mg/l with COD removal efficiency of tank 1+tank 2+ tanks 3 is 94%.

Simultaneous power generation and pollutant removals using microbial desalination cell at variable operation modes

The performance of microbial desalination cells was investigated concurrently under different substrate strengths and variable external resistances. When the external resistance was fixed at 1,000 Ω, the maximum voltage was 710, 694 and 650 mV at substrate COD concentrations of 500, 1500 and 3000 mg/l respectively. The average COD removal efficiencies were 90.0 ± 5.2, 92.3 ± 4.3 and 53.4 ± 7.2% at substrate concentrations of 500, 1500 and 3000 mg/l respectively. The cell operated at high substrate strength achieved the lowest voltage generation and highest internal resistance. Columbic Efficiencies (CEs) increased with decreased COD loading rates. The cell operated at medium substrate strength achieved the best desalination efficiency due to substrate availability and the lowermost internal resistance. Further investigation was made at different external resistances of 10 to 10,000 Ω which were found to have a significant effect on COD removal and CEs. The high desalination efficiencies were accompanied by higher current densities. Scanning Electron Microscopy (SEM) analyses were conducted for the anode electrode to investigate the biofilm morphology. This study demonstrated interesting results regarding the operation modes that could contribute to the microbial desalination cells scale up.

A comparative pilot-scale evaluation of gas-sparged and granular activated carbon-fluidized anaerobic membrane bioreactors for domestic wastewater treatment

Two significantly different pilot-scale AnMBRs were used to treat screened domestic wastewater for over one year. Both systems similarly reduced BOD5 and COD by 86–90% within a 13–32 °C temperature range and at comparable COD loading rates of 1.3–1.4 kg-COD m−3 d−1 and membrane fluxes of 7.6–7.9 L m−2 h−1 (LMH). However, the GAC-fluidized AnMBR achieved these results at a 65% shorter hydraulic retention time than the gas-sparged AnMBR. The gas-sparged AnMBR was able to operate at a similar operating permeability with greater reactor concentrations of suspended solids and colloidal organics than the GAC-fluidized AnMBR. Also, the membranes were damaged more in the GAC-fluidized system. To better capture the relative advantages of each system a hybrid AnMBR comprised of a GAC-fluidized bioreactor connected to a separate gas-sparged ultrafiltration membrane system is proposed. This will likely be more effective, efficient, robust, resilient, and cost-effective.

Nghiên cứu xử lý nước thải thủy sản bằng công nghệ A2/O - MBR

In order to study the applicability of combined wastewater treatment processes of A2/O-MBR, a lab scale model of A2/O-MBR processes with 55-liter A2/O tank combined with 26-liter MBR tank was used to remove contaminants from an aquatic products processing wastewater at relatively high concentration of nitrogen and phosphorus. The COD, BOD5, N-NO3-, N-NH4+, TKN, TN and TP of the influent wastewater are 749± 41,73 mg/L, 507± 49.08 mg/L, 4.35± 1,43 mg/L, 18.77± 0.92 mg/L, 72.9 ± 11.38 mg/L, 77.25 ± 10.01 mg/L, and 37.67± 9.07 mg/L and at pH 6.9 respectively. The A2/O-MBR model was run at hydraulic retention time of 8 hours, organic matter loading of 1.52 kg BOD/m3.day, COD loading rate for anaerobic chamber of 22.47 kg COD/m3.day and MLSS concentration for A2/O tank of 4.163 mg/L. The COD, BOD5, N-NO3-, N-NH4+, TKN, TN, and TP in the effluent were 21.49 ± 0.86 mg/L, 16.8 ± 1.56 mg/L, 2.4 ± 0.28 mg/L, 0.75 ± 0.13 mg/L, 1.32 ± 0.39 mg/L, 3.72 ± 0.41 mg/L, and 5.87 ± 1.0 mg/L, respectively. The effluent quality met the column A of the national technical regulation on the effluent of aquatic products processing industry, with corresponding removal efficiency of 97% COD; 96% BOD5; 45% N-NO3-, 96% N-NH4+; 98% TKN, 95% TN, and 84% TP. Therefore, the A2/O-MBR combined processes can be applied to treat aquatic products processing wastewaste and all other wastewaters of the same characteristics.

Evaluating organics removal performance from lagoon-pretreated swine wastewater in pilot-scale three-stage surface flow constructed wetlands

Pilot-scale three-stage surface flow constructed wetlands (SFCWs) planted with Myriophyllum aquaticum were constructed to study the organics removal performance from lagoon-pretreated swine wastewater. The removal performance of organics in the SFCWs was evaluated using deterministic and probabilistic methods and the results were consistent. The SFCWs achieved a relatively high removal efficiency (79.0–82.7%) for a wide influent COD concentration range (456–1010 mg L−1). No significant difference (p > 0.05) of COD removal efficiency and first-order removal rate constant among the various strengths of influent suggested that the present loading rates (2.74–6.06 g m−2 d−1) have not yet reached the maximum removal capacity of the SFCWs. The mean emission fluxes of methane from the SFCW units fed with different strengths of wastewater were 25–1210 mg m−2 d−1. A significantly positive correlation (p < 0.01) between methane emission fluxes and COD loading rates indicated that the anaerobic digestion of organics was an important process for organics removal in the SFCWs. No significant organics accumulation in the sediment over time suggested that plant harvest could be in favor of reducing the organics accumulation in the substrate and should be considered important during management of constructed wetlands.