Effluent Chemical Oxygen Demand Concentration Research Articles

Bio-degumming of ramie fiber using an integrated spiral symmetry stream anaerobic bioreactor

The bio-degumming method focused research interest on green degumming technology in the textile sector, addressing environmental pollution, water usage and energy consumption caused by chemical degumming methods while enhancing fiber quality. The application of recent developments in the chemical degumming method of fiber remains a challenge for environmental protection. The novel spiral symmetry stream anaerobic bioreactor was employed in a system that integrates the ramie degumming process and reduces wastewater generation. This study analyzed the effect of liquor ratios on the water quality indicators, fiber quality and microbial community composition. After this study, the effluent chemical oxygen demand concentration, pH and ammonia nitrogen were 264.2 ± 114.2, 7.2 ± 0.1 and 7.4 ± 4.8 mg/L, respectively. This shows a mean chemical oxygen demand removal rate of 55.7 ± 11.8%, which is over 79% higher than previous bio-degumming methods. The fiber quality met the ramie fine dry hemp standard requirements. The high-throughput sequencing results revealed that the microbial community adapted to this process. The relative abundance of dominant microbes ( Bacteroidetes and Methanosaeta), which perform biodegradation and methane production, was present. This study demonstrates a promising green degumming technology and eco-friendly concept for the textile industry.

Reduction of soluble microbial products in activated sludge system with pure oxygen aeration under toxic stress condition of phenol

<p>This study aimed to explore the effect of pure oxygen aeration on the generation of soluble microbial products (SMP) when activated sludge was under toxic stress condition of phenol. Two parallel sequencing batch reactors, one with air and the other with pure oxygen aeration, were used to investigate the relationships among effluent chemical oxygen demand (COD), N-acyl-homoserine lactones (AHLs), microbial community, extracellular polymeric substances (EPS), and SMP. The results showed that pure oxygen aeration caused rapid recovery of the activated sludge and low effluent COD concentration in steady condition when the two reactors were fed with phenol. In contrast, these results were not observed with sodium acetate as substrate. A strong correlation was found among C4-HSL, loosely bound EPS (LB-EPS), and SMP. The genera Zoogloea, Bacteroides, and Flavobacterium were also related to effluent COD, SMP, and LB-EPS production under toxic stress condition of phenol. Pure oxygen aeration reduced AHL production and decreased the relative abundance of specific genera (Zoogloea and Flavobacterium). These changes caused the reduction of SMP generation in the pure oxygen-aerated activated sludge systems. These results provide insights into the effect of pure oxygen aeration on SMP generation of activated sludge with toxic substance existence.</p>

Wastewater treatment for ships experiencing large temperature changes： the activated sludge/membrane-biofilm reactor

A particular challenge to treatment systems for ship wastewater comes from low and variable temperatures. We evaluated the temperature response (35–15 °C) of a novel biological treatment system involving activated sludge followed by a membrane-biofilm reactor: the activated sludge/membrane-biofilm reactor (AS-ABfMemR). In this study, a pilot-scale AS-ABfMemR achieved over 96% chemical oxygen demand (COD) and 94% total nitrogen (TN) removal from a ship wastewater (550–960 mgCOD·L−1 and 52–77 mgTN·L−1) with a continuous operation with a hydraulic retention time of 12 h at 25 °C. The effluent COD and TN concentrations met IMO discharge standards at temperatures as low as 17 °C, which reduced the energy consumption for wastewater heating. The COD and TN removals of the biofilm stage became important (up to 34% and 35%, respectively) at low temperatures, and this compensated for the deterioration in performance of the aerobic sludge. The genus Azospira dominated in the biofilm's denitrification removal for TN at low temperature. In addition, the buildup of trans-membrane pressure was so slow that backwashing was not needed over the 90 days of continuous operation. These conclusions indicate that the pilot-scale AS-ABfMemR technology is an effective way for real ship sewage treatment under temperature variations.

The sustainable utilization of anaerobic digestion effluents treating in suspended filler algae assisted systems

Significant amounts of anaerobic digestion effluents (ADE) containing high concentration of inorganic salts (source of nitrogen and phosphorus) and hardly degradable organic matter are produced during the generation of biogas using livestock manure. Without appropriate treatment, the imbalanced carbon to nitrogen ratio may lead to severe pollution of the environment. Considering different environmentally friendly processes such as recycling, energy regeneration, and sustainable development, suspended fillers were added to traditional algal-bacterial symbiosis (ABS) systems. In the present research, three systems including suspended filler algae assisted bio-reactor (SFA-PBR), no filler algae assisted bio-reactor (NFA-PBR), and single activated sludge system (ABS) were examined. Changes in bacterial communities were analyzed using high throughput sequencing. In addition, the mechanisms of ADE degradation in the presence and absence of suspended algae fillers were studied by comparing their effect on the degradation of COD (chemical oxygen demand), TN (total nitrogen), AN (ammonia nitrogen), and TP (total phosphorus). Systems where the ratio of active microalgae to bacteria was higher promoted the interaction between the two types of microorganisms, accelerating the stability of the ABS. Thus, the daily COD degradation rate in the stage was still high. Flora such as microalgae and bacteria were embedded in the filler spheres, which increased the microorganisms resistance to the poor environment induced by high concentrations of inorganic nutrients and organic matter present in the ADE. This favored the sustainable water utilization of ADE. After the treatment in the SFA-PBR system, the COD degradation rate was 75.32 %. The effluent COD concentration was 334.21 ± 39.18 mg/L. TN and AN degradation rates were 89.34 and 91.32%, respectively. The TN and AN concentrations in the effluent were 35.42 ± 2.65 and 29.97 ± 2.65 mg/L, respectively. The degradation rate of TP was 95.39 %. The effluent TP concentration was 0.86 ± 0.18 mg/L. The Chao diversity and ACE index values in the SFA-PBR system were higher than those of other groups. This result further supports the conclusion formulated with the Shannon diversity index result. Specifically, the effective sequence in the SFA-PBR system group presented a higher degree of homogeneity and abundance.

Assessment of High Salinity Wastewater Treatment with Dewatered Alum Sludge-Aerobic Membrane Reactor

Abstract The discharge of wastewater containing both high salinity and high organic content without prior treatment is detrimental to aquatic life and water hygiene. In order to integrate the advantages of membrane treatment and biological treatment, and exert the phosphorus removal efficiency of dewatered alum sludge, in this study, an aerobic membrane reactor based on dehydrated alum sludge was used to treat mustard tuber wastewater with salinity of 6.8-7.3 % under the conditions of 30 °C, 20 kPa trans-membrane pressure (TMP) and chemical oxygen demand (COD) of 3300-3900 mg/L. Three replicate reactors were applied to assess the operational performance under different organic loading rate (OLR). The results showed that all reactors were effective in removing COD, ammonia nitrogen (NH4 +-N) and soluble phosphate (SP) under the conditions of 30 °C and 20 kPa of TMP. Meanwhile, the effluent concentration of COD, NH4 +-N and SP all increased while OLR was changed from 1.0 to 3.0 kg COD/m3/day, and the effluent COD and NH4 +-N concentration except for SP could reach the B-level of Chinese “Wastewater quality standards for discharge to municipal sewers” when OLR was less than 3.0 kg COD/m3/day. This indicates that dewatered alum sludge-based aerobic membrane reactor is a promising bio-measure for treating high salinity wastewater.

Kinetic models evaluation for chemical organic matter removal prediction in a full-scale primary facultative pond treating municipal wastewater

Abstract This study focuses on determining the bio-kinetic coefficients of chemical oxygen demand (COD) removal in full-scale primary facultative ponds (PFPs) system on the basis of 3-year continuous operation. The mean removal of chemical oxygen demand (COD), total suspended solid (TSS) and volatile suspended solid (VSS) were 80, 59 and 49%, respectively. The first-order model paired with continuous stirred-tank reactor (CSTR) and plug flow (PF) regimes, PF k–C*, Stover-Kincannon and Grau second-order models were applied to link COD concentrations at the inlet and outlet of the system and to compare the predictive power of models for the estimation of effluent COD concentrations. The Stover-Kincannon model showed the best adaptability (r2 = 0.9294) with the maximum substrate utilization rate (Umax) of 79.14 g/L· d and saturation constant (KB) of 80.65 g/L· d, whereas the Grau second-order model was the best model to predict outlet COD concentrations (r2 = 0.6925). The computed constants, m and n, of the Grau second-order model were 0.6725 and 15.867 d−1, respectively. While the Stover-Kincannon kinetic rates obtained in this study can be used to design the PFP systems in similar operational conditions, the appropriate prediction of pond behavior can be achieved using the Grau model.

Pollutant removal from municipal sewage by a microaerobic up-flow oxidation ditch coupled with micro-electrolysis.

The development of efficient and low-cost wastewater treatment processes remains an important challenge. A microaerobic up-flow oxidation ditch (UOD) with micro-electrolysis by waterfall aeration was designed for treating real municipal wastewater. The effects of influential factors such as up-flow rate, waterfall height, reflux ratio, number of stages and iron dosing on pollutant removal were fully investigated, and the optimum conditions were obtained. The elimination efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN) and total phosphorus (TP) reached up to 84.33 ± 2.48%, 99.91 ± 0.09%, 93.63 ± 0.60% and 89.27 ± 1.40%, respectively, while the effluent concentrations of COD, NH4+-N, TN and TP were 20.67 ± 2.85, 0.02 ± 0.02, 1.39 ± 0.09 and 0.27 ± 0.02 mg l−1, respectively. Phosphorous removal was achieved by iron–carbon micro-electrolysis to form an insoluble ferric phosphate precipitate. The microbial community structure indicated that carbon and nitrogen were removed via multiple mechanisms, possibly including nitrification, partial nitrification, denitrification and anammox in the UOD.

Green environment and sustainable development: methods and applications

Abstract The discharge of wastewater containing both high salinity and high organic content without prior treatment is detrimental to aquatic life and water hygiene. In order to integrate the advantages of membrane treatment and biological treatment, and exert the phosphorus removal efficiency of dewatered alum sludge, in this study, an aerobic membrane reactor based on dehydrated alum sludge was used to treat mustard tuber wastewater with salinity of 6.8-7.3 % under the conditions of 30 °C, 20 kPa trans-membrane pressure (TMP) and chemical oxygen demand (COD) of 3300-3900 mg/L. Three replicate reactors were applied to assess the operational performance under different organic loading rate (OLR). The results showed that all reactors were effective in removing COD, ammonia nitrogen (NH4 +-N) and soluble phosphate (SP) under the conditions of 30 °C and 20 kPa of TMP. Meanwhile, the effluent concentration of COD, NH4 +-N and SP all increased while OLR was changed from 1.0 to 3.0 kg COD/m3/day, and the effluent COD and NH4 +-N concentration except for SP could reach the B-level of Chinese “Wastewater quality standards for discharge to municipal sewers” when OLR was less than 3.0 kg COD/m3/day. This indicates that dewatered alum sludge-based aerobic membrane reactor is a promising bio-measure for treating high salinity wastewater.

Bio-energy generation and treatment of tannery effluent using microbial fuel cell

In this study, Graphite Particle (GP) and Carbon Cloth (CC) are employed as anode electrodes to study both bio-energy generation, and decrease of Chemical Oxygen Demand (COD) simultaneously using tannery effluent. The influence of electrodes distance (10 cm and 20 cm) on electricity production was evaluated. COD removal level of GP (75%) and CC (60%), maximum power outputs for 10 cm distance (600 ± 5 mW m−2) & (500 ± 10 mW m−2) and for 20 cm distance (520 ± 5 mW m−2) and also (430 ± 20 mW m−2) GP and CC were noted correspondingly. The outcomes of different parameters of MFC namely pH, conductivity, COD concentration, membrane thickness and size of bio-energy generation from tannery effluent in the MFC were investigated. The experimental results reveal that electrode provides highest power output with 10 cm distance between anode and cathode chamber. As a result, GP electrode is gradually viable, biocompatible, effective and adaptable for field application in MFC. The GP electrode has high potential for more power output, when compared to the CC electrode. The MFC system performance was improved with increasing effluent COD concentration (2340–4720 ppm), anolyte conductivity (1.6–8.1 mS cm−1) and membrane area (9–20 cm2). The system working with conductivity of 8.1 mS cm−1 and its effluent COD concentration of 4720 ppm generated the maximum peak power density of 44.69 mW m−2 with respective current density of 109 mA m−2. The findings thus show that considerable power production and effluent treatment can be achieved by MFC.

Adsorption of organic matter from papermaking wastewater by CoFe2O4-coated sand in batch and fixed-bed systems

The secondary treated effluents of pulp and paper mills contain high chemical oxygen demand (COD) that is associated with organic matter. Therefore, this study explores the adsorption of substances contributing to COD using CoFe2O4 and quartz sand-coated CoFe2O4 in batch and fixed-bed column experiments. X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller analysis, and X-ray photoelectron spectroscopy were used to characterize the adsorbents. The quartz sand-loaded CoFe2O4 exhibited a larger pore volume and average pore size. Batch experiments revealed that adsorption on CoFe2O4 closely fit the pseudo-second-order model. To explore the effects of bed depth, feed flow rate, and initial solution pH on the breakthrough characteristics of CoFe2O4-coated sand, fixed-bed column experiments were conducted, and the breakthrough curves were drawn from the ratio of influent COD concentration to effluent COD concentration. The breakthrough time decreased with an increase in the feed flow rate and initial pH but increased with the bed depth. According to the X-ray photoelectron spectroscopy analysis, CoFe2O4-coated sand showed excellent stability due to negligible leaching of metallic elements. These findings have important implications for the advanced treatment of industrial wastewater.

Performance efficiency and water quality index of a two-stage horizontal subsurface flow constructed wetland system polishing anaerobically treated brewery effluent

The disposal of untreated or partially treated brewery wastewater can cause pollution problems to the receiving water bodies. The objective of this study was to evaluate the effectiveness of a two-stage horizontal subsurface flow constructed wetland (HSSFCW) system planted with Cyperus alternifolius and Typha latifolia in polishing an up-flow anaerobic sludge blanket (UASB) reactor treating brewery effluent in Kombolcha, Northern Ethiopia. The system was integrated with the UASB reactor, and its performance efficiency was monitored for a year using standard methods. The first-order kinetic model was used to correlate the influent and effluent pollutant concentrations and estimate the areal rate constant (kA) by fitting the experimental data to the model. The HSSFCW's water quality index (WQI) and oxygen transfer rate (OTR) were also calculated. The findings showed that HSSFCW removed 89% total suspended solids (TSS), 92% chemical oxygen demand (COD), 83.6% total nitrogen (TN), 92.9% ammonium – nitrogen (NH4+ − N), 74.4% total phosphorous (TP), and 79.5% orthophosphate (PO43−). Literature comparable OTR values were obtained for each HSSFCW stage with a total OTR value of 23.5 g−2d−1. Effluent concentrations of COD, TN and NH4+ − N were reasonably correlated (R2 ≥ 0.85) to influent concentrations. The calculated kA (md-1) for TSS, COD, TN, NH4+ − N, TP, and PO43− were 0.26, 0.26, 0.11, 0.18, 0.08, and 0.08, respectively. Further polishing of the effluent with two-stage HSSFCW has shifted the WQI from a good to excellent water quality rating and thus, can be used as a sustainable polishing technique for agro-process wastewaters.

Determination of Kinetic Constants for Treating Tannery Wastewater Using Activated Sludge Process (ASP)

A study was conducted to evaluate the feasibility of Activated Sludge Process (ASP) for the treatment of tannery wastewater and to develop a simple design criterion under local conditions. A bench scale model comprising of an aeration tank and final clarifier was used for this purpose. The Lab scale reactor was operated continuously and settled tannery wastewater was used as influent to the aeration tank. Five days Biochemical Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD) of the influent and effluent were measured to find process efficiency at various mixed liquor volatile suspended solids (MLVSS) and Hydraulic Detention Time (θ).The results of the study demonstrated that an efficiency of above 90% and 80% for BOD5 and COD, respectively could be obtained if the ASP is operated at an MLVSS concentration of 3500 mg/L keeping an aeration time of 12 hours.ASP is a feasible treatment technology for tannery wastewater treatment, by conducting experiments at the HRTs of 12,10,8,6 and 2 h, it was found that the maximum COD removal efficiency of 84.20% was recorded at 12 h HRT. In this study, the Mathematical Models such as Monod, Grau Second Order, Modified Stover-Kicannon and First Order Kinetic Models were applied for the performance evaluation of the Reactor at any given time and found that the data were in good agreement with the observed ones in the models, such as, Grau second order and Monod. Further, the correlation coefficient value (R2) obtained for the experimental and predicted effluent COD concentration using the above mentioned (Grau second order and Monod) models also confirmed the suitability applying the models to predict the performance of the reactor under lab scale-controlled environmental conditions.

Discerning realizable advantages of microbial electrochemical system towards raw municipal wastewater treatment: From the analyses of mass and energy flow

The low-cost biocathode microbial electrochemical system (MES) with microbial separator (MS) is promising for the practical application in wastewater treatment. To evaluate the potential realizable advantages for future full-size MESs, four 2-Liters MES modules with MS are constructed and their energy conversion, biomass metabolism and pollution degradation are systematically investigated. The mass and energy flow for MES with raw domestic wastewater is built under maximum power point (Pmax), maximum current point (Imax), and open circuit (OC) modes. The chemical oxygen demand (COD) removal rates are 0.831 and 0.846 kg m−3 day−1 in Pmax and Imax modes, while that of OC is 0.609 kg m−3 day−1. The effluent COD concentrations at Pmax and Imax are stable at 41 ± 2 and 37 ± 2 mg L−1, while that of OC is up to 101 ± 4 mg L−1. The observed sludge yield is only 23.4% (Pmax) or 19.5% (Imax) of the OC mode with much higher sludge calorific values. For the raw wastewater treatment, the direct electricity harvest and reuse from MES units are unrealistic and uneconomical due to its low energy efficiency. But the high COD removal efficiency and low observed sludge yield are the realizable advantages for practical applicated MESs.

Modeling and simulation of an extended ASM2d model for the treatment of wastewater under different COD: N ratio

We evaluated the impact of chemical oxygen demand (COD) to nitrogen (N) ratios on the performance of a laboratory-scale anaerobic/anoxic/oxic (A2O) reactor by establishing an extended ASM2d model. This extended model introduced soluble microbial products (SMPs) and extracellular polymeric substances (EPS) to create the ASM2d-E-M. Other variables were introduced in the model to describe processes that already exist in the ASM2d, and those that were previously missing (e.g. EPS/SMP). To improve the accuracy of the simulation, this study included the establishment of the model, the division of model components, a sensitivity analysis, and model calibration and verification. The average errors of COD, ammonia and orthophosphate concentrations between the steady-state simulation data and experimental data, under different COD: N ratios were 7.42 %, 13.2 % and 9.18 %, respectively. Additionally, the average errors from the EPS and SMP simulation results were lower than 1.50 % and 2.59 %, respectively. The dynamic simulation results indicate that effluent COD, ammonia, orthophosphate and biopolymer concentrations decrease with an increase in influent COD: N ratio. But orthophosphate increases when COD: N increases to 16:1. Comparing the steady-state simulation and dynamic simulation of the model with the experimental procedure confirms that the model effectively describes the biological processes in an A2O reactor, accurately predicts SMP and EPS production in the activated sludge system under different COD: N ratios and provides a valuable tool for the operation.

Performance comparison of phenol removal in pharmaceutical wastewater by activated sludge and extended aeration augmented with activated carbon

This study investigated the removal of phenol, Chemical Oxygen Demand (COD), and ammonia from pharmaceutical wastewater using activated sludge (AS) and extended aeration (EA) systems. Also, the impact of adding activated carbon media on the performance of the two systems has been studied. Synthetic sewage was used with a composition of COD equaling 1500 mg/L. The experimental work was divided into five scenarios for the two reactors based on the Phenol concentration, 0.0 mg/L in the first scenario, 50.0 mg/L in the second and third scenarios, but activated carbon has been added to the third one. The concentration of Phenol was 100.0 mg/L and 150.0 mg/L for the fourth and fifth scenarios, respectively. The experimental results indicated that EA system gives higher removal efficiency than that by AS system for COD, phenol, and ammonia. In addition adding activated carbon of just 1.0 gm/L of the working reactor volume in both systems (AS, EA) has improved the removal efficiency. GPS-X simulator was employed to predict the performances of the biological systems under high effluent concentration of COD reaching up to 19000 mg/L. The simulation results indicated that EA effluent could comply with Egyptian Cod (Law no 44/2000).

Performance evaluation of novel attached-growth high rate algal pond system with additional artificial illumination for wastewater treatment and nutrient recovery.

Domestic wastewater containing a high proportion of organic matter and nutrients is a serious pollution problem in developing countries. This study aimed to evaluate the performance of a novel attached-growth high rate algal pond (AG-HRAP) employing attached-growth media and artificial light sources for treating domestic wastewater and enhancing nutrient recovery. Light intensities in the range of 40-180 μmol/m2/s were used in the AG-HRAPs. The experimental results showed that the highest chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removal efficiencies of 88, 62 and 69%, respectively, were found at the hydraulic retention time (HRT) of 15 days and the average light intensity of 180 μmol/m2/s. Moreover, the effluent COD concentrations could meet Thailand's national discharge standard. The highest biomass and protein productivities of 54 ± 4 and 37 ± 8 g/m2/d, respectively, were found in the AG-HRAPs, which were higher than in previous studies of HRAPs. The Stover-Kincannon kinetic values for COD, TN and TP removals of the AG-HRAPs (R2 = 0.9) were higher than those of the conventional systems. Additionally, the novel AG-HRAP system could provide a highly cost-effective operation when compared to other microalgal systems.

Enhanced treatment of landfill leachate wastewater using sono(US)-ozone(O3)–electrocoagulation(EC) process: role of process parameters on color, COD and electrical energy consumption

The combination of advanced oxidation processes (AOPs) and electrochemical process is gaining growing popularity for use in wastewater treatment. The present work explores for the first time, treatment of leachate wastewater from landfill waste using a combination of sonication (US), ozonation (O3) and electrocoagulation (EC) process expressed by % color removal, % Chemical Oxygen Demand (COD) removal and its associated electrical energy consumption. The results revealed that, the combined process (US/O3/EC) is highly successful in the treatment of leachate wastewater from landfill in terms of % color removal (100 %) and % COD removal (97.50 %) with low electrical energy consumption (8kWhr/m3) than the other hybrid and single process such as O3/EC, US/EC, US/O3 and EC, O3, US. The influence of different process parameters such as electrolyte concentration (1.50–7.50 g/L), current density (1.25–7.50 A/dm2), initial effluent pH (2–11), COD concentration (2000–6000 ppm), O3 production (0.75–3.75 g/hr) and sonication power (20–100 Watts) were studied on the efficiency of pollutant removal evaluated by reduction of % color and % COD and electrical energy consumption using hybrid US/O3/EC process. Overall, the analysis clearly showed that the approaches to integrated treatment technologies could synergistically remove the pollutant from the wastewater.

Evaluating the performance of a sequencing batch reactor for sanitary wastewater treatment using artificial neural network

AbstractIn this work, the performance of a sequencing batch reactor (SBR) was studied for treating sanitary wastewater of Yazd power plant, Iran. For this purpose, at the first, a pilot system was designed, installed, and started up. Then the effects of retention time, pH, temperature, influent chemical oxygen demand (COD) concentration, and air flow rate were investigated on the effluent concentration of COD. In SBR reactor used in the Yazd power plant, the microalga was not used for the wastewater treatment. In this case, the COD effluent output was, at the best conditions, approximately 92 mg/L. In the studied SBR system, we used the Chlorella vulgaris microalgae and microorganisms, simultaneously. In this case, the COD level reached 34 mg/L. An artificial neural network (ANN) was developed by applying Levenberg‐Marquardt training algorithm to predict the effluent concentration of COD. The optimum conditions were obtained at pH = 8, temperature of 30°C, influent COD concentration of 600 mg/L, and air flow rate of 50 L/min. ANN predicted results were in good agreement with the experimental data with a validation coefficient of determination (R2) and validation mean square error of 0.962 and 0.0015, respectively.

Pilot Study on Start-up and Stable Operation at Low Temperature Based on Denitrifying Phosphorus Removal

In order to understand the denitrifying and phosphorus removal characteristics of denitrifying phosphate-accumulating organisms (DPAOs), a pilot scale (20 m3) denitrifying and phosphorus removal experiment was carried out using a modified University of Cape Town (UCT) process at low temperatures of (6-16)℃. The test results show that at such temperatures, the hydraulic retention time (HRT) is 20 h and the solids retention time (SRT) is 35 days, and the modified UCT process can start up successfully and run steadily. When running steadily, the system can maintain nitrogen and phosphorus removal rates of 60%±5% and 80%±5%, respectively. The effluent concentrations of chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) were 20, 5, 11, and 0.5 mg·L-1, respectively, which meet the first A emission standard of "Pollutant Discharge Standard for Urban Sewage Treatment Plant" (GB 18918-2002). In order to further investigate the characteristics of nitrogen and phosphorus removal in the system, the reflux ratio from the aerobic tank to the anoxic tank was increased to 150%. After the system was stabilized, it obtained higher nitrogen and phosphorus removal rates of 80%±10% and 90%±5%, respectively. Among them, denitrifying phosphorus removal in the anoxic tank accounted for 80%±4% of the total biological phosphorus removal. The average effluent concentrations of COD, NH4+-N, TN, and TP were 19.55, 0.1, 7.8, and 0.15 mg·L-1, respectively, which meet the Beijing Standard A discharge standard.

Combined UMBAF‐MBAF process treating detergent wastewater

A combined process of the upflow multimedium biological aerated filter (UMBAF) and the multimedia biological aerated filter (MBAF) treating detergent wastewater was investigated in this study. Results showed that the optimal filtration rate of the combined system was 1.4m/hr while the optimized performance was observed at air to water ratio of 2:1. The average removal rate of chemical oxygen demand (COD), linear alkyl benzene sulfonate sodium (LAS), and total phosphate (TP) was up to 91.4%, 88.5%, and 40%, respectively, while the average effluent concentrations of COD, LAS, and TP under stable operation states were 35.0mg/L, 7.0mg/L, and 4.4mg/L, respectively. UMBAF played a major role in TP removal; the removal of COD in the combined UMBAF and MBAF process was consistent with the general formula C=C0 e -(ah + b) , while the kinetic model of LAS removal in the combined UMBAF and MBAF process could be expressed by L=L0 e-(mh + n) . The combined UMBAF-MBAF process provides a promising technology for the treatment of detergent wastewater. The kinetic model of LAS removal in the UMBAF and MBAF units is helpful for the prediction of the treatment efficiency of organic pollutants. PRACTITIONER POINTS: A novel UMBAF-MBAF process was developed treating detergent wastewater. The average removal rate of COD, LAS, and TP by the combined process was up to 91.4%, 88.5%, and 40%, respectively. Kinetic models for the UMBAF-MBAF process were investigated.