Aerobic Section Research Articles

Nutrient Removal from Industrial Wastewater Systems Using Controlled Activated Sludge Treatment

Biological treatment with activated sludge as an alternative treatment was studied, and nitrogen and phosphorus were monitored. This scheme involves modifying the treatment tank by dividing it into anoxic and aerobic sections. According to this scheme, the process simulation was performed using Hydromantis' GPS-X 7.0 computer software. Wastewater discharges are usually generated by various industrial activities such as the milk (dairy) processing industry, petroleum processing refineries and slaughterhouses, which were studied in detail. The economic evaluation (cost estimation) of removing nutrients has been done using the CapdetWorks 4.0 computer simulation software. A cost sensitivity analysis has also been performed for the variable influent flows, altering the alpha factor for oxygen transfer during the aeration process and serving as a typical variable. The simulation procedure and economic evaluation have been carried out for a complete wastewater treatment plant, including both treatment lines (the water line and the sludge line simultaneously), and the derived results have been represented through illustrated graphs, tables, and meaningful diagrams.

Application of Anaerobic-Aerobic Combined Bioreactor in Phosphorus Removal

A two-stage anaerobic-aerobic sequencing reactor system was developed in order to enhance the removal of biological phosphorus in the sequencing of combined reactors. Combining both aerobic and anaerobic designs in one reactor improved the efficiency and reduced the construction and operating costs. The combination of an upflow anaerobic fixed bed (UAFB) and a floating activated sludge aerobic bioreactor was designed with respective Kaldnes packing ratios of 90 and 30% for the anaerobic and aerobic sections. The controlled parameters were pH levels within a neutral range, a temperature of 37°C, mixed liquor suspended solids (MLSS) of 1220 and 1030 mg/L for the aerobic and anaerobic sections, respectively, and an attached growth that was equal of 743 and 1190 mg/L for the aerobic and anaerobic sections, respectively. Tests were conducted for three different initial phosphorus concentrations (12.8, 32.0, and 44.8 mg/L), two different volumes for each section, and four chemical oxygen demands (CODs) (500, 1000, 1200, and 1400 mg/L). The results demonstrated that, generally, the phosphorus removal in the anaerobic section fell significantly by increasing the inlet COD, and the maximum removal occurred at COD = 500 mg/L. More than 90% of the phosphorus was removed in the aerobic section at COD = 500 mg/L. In other words, the best performance of the reactor was when the ratio of the COD : N : P = 100 : 5 : 2, composition of phosphorus in industrial wastewater.

An integrated process of Fe/C micro-electrolysis-anaerobic hydrolyze-microalgae for treatment of high concentration pharmaceutical wastewater

As a high concentration wastewater of high organic matter content, many toxic substances, large amounts of organic solvents and poor biochemistry, pharmaceutical wastewater is challenging to handle with a single water treatment technology. In this study, a combined process of Fe/C micro-electrolysis (Fe/C-ME)-anaerobic hydrolyze-microalgae was developed to treat high-concentration pharmaceutical wastewater (i.e. 100,000 mg/L chemical oxygen demand (COD), 2800 mg/L ammonia nitrogen (NH3-N) and 130 mg/L total phosphorus (TP)). Firstly, in the Fe/C-ME process, under optimal experimental conditions, the removal rates of COD, NH3-N and TP were 55 %, 36 % and 63 %, and it was worth mentioning that the removal of ammonia nitrogen and total phosphorus may be attributed to the complexation and flocculation of hydrated iron ions. Secondly, the outer circulation anaerobic reactor (OCAR) performed biochemical treatment on pretreated pharmaceutical wastewater, 85 % of COD was removed, and it was found that through anaerobic digestion, and further hydrolyzed and acidified macromolecular pollutants into small molecules to reduce the impact load, which was conducive to the subsequent digestion and absorption of microalgae and improved the treatment efficiency of the aerobic section. The microalgae cultivated by heterotrophy using anaerobic effluent, directly used NH3-N and TP in wastewater to synthesize substances needed for self-growth and reproduction, and removed 88 %, 91 % and 83 % of COD, NH3-N and TP, respectively. The final results indicated that the removal rates of COD, NH3-N and TP in the integrated process of Fe/C-ME-anaerobic hydrolysis-microalgae were 99.8 %, 98.6 % and 98.5 %, respectively, demonstrating that the coupling process is an effective method for treating high-concentration pharmaceutical wastewater.

Transport and interaction of cadmium and active sludge extracellular polymeric substances in saturated sand influenced by ionic strength and composition.

Artificial groundwater recharge with reclaimed water (secondary effluent from wastewater treatment plants) has become an important approach to solving water scarcity worldwide. Microorganisms in activated sludge can secrete many extracellular polymeric substances (EPS). However, information on the impact of EPS on the movement of heavy metals in porous media and their environmental effects on underground networks is limited. To assess this risk, we extracted EPS from the aerobic section of a wastewater treatment plant using hot sodium hydroxide and conducted experiments using one-dimensional sand columns to investigate how ion composition and strength affect the movement and interaction of cadmium (Cd) and EPS in porous media. The results showed that EPS facilitated Cd migration in porous media. Sodium (Na) and calcium (Ca) ions promoted the migration of Cd in porous media and EPS-Cd complexation. The effect of Ca was more significant than that of Na. As the Na adsorption ratio increased, the migration ability of Cd in porous media and the complexation ability of EPS with Cd decreased. Therefore, when estimating the migration of EPS and Cd in subsurface environments, careful consideration should be given to prevent the risk of groundwater pollution.

Research on Greenhouse Gas Emission Reduction Methods of SBR and Anoxic Oxic Urban Sewage Treatment System

With the rising awareness of environmental protection, more sewage treatment plants have been built. However, this is also one of the main sources of greenhouse gas emissions. This study carried out a series of sewage treatment experiments to analyze the factors affecting the greenhouse gas emissions of the two commonly used treatment processes in the current urban sewage treatment: the A/O and SBR methods. The experimental results showed that the total amount of greenhouse gases emitted by the A/O method was 415.63 gCO2-eq/m3, and the total amount of greenhouse gases emitted by the SBR method was 879.51 gCO2-eq/m3. The N2O emission factor in the A/O method experimental group was 0.76% of the nitrogen content in the influent. In the aerobic section, when the content of dissolved oxygen was in the range of 1.30~2.10 mg/L, and the content of dissolved oxygen was 1.90 mg/L, the minimum N2O emission factor was reduced to 0.29% of the nitrogen content of the influent. In the SBR experimental group, the ammonia oxidation rate of sewage decreased rapidly as the temperature decreased, thus affecting the discharge rate of N2O. At 25 °C, the biological enzyme activity of nitrifying bacteria was higher, thus promoting denitrification and generating more greenhouse gases. The research results provide reference for strengthening the management of sewage treatment plants and reducing greenhouse gas emissions from sewage treatment plants.

An Application of Anaerobic-Aerobic Combined Bioreactor Efficiency in COD Removal

Over the past few decades, anaerobic-aerobic wastewater treatment systems have been widely used in industrial and municipal wastewater treatment. This study was conducted to examine the effects of combined anaerobic-aerobic bioreactors in the removal of chemical oxygen demands (COD) while reducing phosphate concentrations in synthetic wastewater. In this project, a bioreactor with the dimensions of 10 cm × 10 cm × 80 cm with respective Kaldnes packing ratios of 90 and 30% for the anaerobic and aerobic sections was designed. A combined anaerobic-aerobic reactor’s structure made changing hydraulic retention times only possible by adjusting the volume of its aerobic and anaerobic sections. In the first case, the anaerobic and aerobic sections of the reactor occupied 30 and 50 cm of its height, respectively. The height of the anaerobic section decreases to 12.5 cm in the second case. In aerobic and anaerobic sections, pH was within a neutral range, temperature was 37°C. MLSS (mixed liquor suspended solids) was 1220 and 1030 mg/L, and attached growth was 743 and1190 mg/L respectively. In order to evaluate COD in the wastewater, three different initial phosphorus concentrations were tested: 12.8, 32.0 and 44.8 mg/L, as well as four COD: 500, 1000, 1200 and 1400 mg/L. Considering the results, COD removal is greater than 80% when the valve 2 is in the anaerobic section outlet regardless of the concentration of phosphate. In this case, the best result is for inlet COD of 500, where the reactor can eliminate more than 90%. When the COD concentration reaches 1000 to 1400 ppm, the reactor’s COD removal efficiency declines to 60%.

Insight into dissolved organic nitrogen transformation and characteristics: Focus on printing and dyeing wastewater treatment process

Textile industry discharges large amounts of printing and dyeing wastewater (PDW) containing high concentration of refractory dissolved organic nitrogen (DON). However, the DON transformation and characteristics during PDW treatment, and its potential environment impact receive little concern. Treatment groups of dyeing wastewater (G-RB5), printing wastewater (G-Urea) and domestic wastewater (G-NH4Cl) with Reactive Black 5 (RB5), Urea and NH4Cl as influent nitrogen species were set to compare the DON behavior during the hydrolytic acidification-aerobic-anoxic process. G-RB5 exhibited higher DON concentrations with greater fluctuations, and its effluent dominated low molecular weight (LMW) and hydrophilic DON, showing high bioavailability (67.6%) and low biodegradation (8.0%). In the aerobic section, the concentration of microorganism-derived DON in G-RB5 was higher but the nitrogen species were fewer than G-Urea and G-NH4Cl. Grey relational analysis revealed that Proteobacteria and Thauera were the common bacteria strains showing high association degree (γ > 0.9) with biodegradable DON (ABDON) in all groups; while microbes related with biodegradable DON (BDON) varied between groups. The higher contents of DON, ABDON, LMW-DON and hydrophilic DON induced by RB5 highlight the importance of controlling DON from textile industry to mitigate the potential risk like algae growth stimulation, which needs more attention in future.

Robust nitrogen removal from municipal wastewater by partial nitrification anammox at ultra-low dissolved oxygen in a pure biofilm system

Efficient nitrogen removal from municipal wastewater applying a pure biofilm system has promise. In this study, a partial nitrification anammox (PNA) pure biofilm system was established in a sequencing batch reactor with anaerobic/oxic/anoxic operation; using this reactor, robust nitrogen removal from municipal wastewater at ambient temperature was achieved with a nitrogen removal efficiency (NRE) of 93.3 %. Partial nitrification with anammox could be coupled at dominant nitrite-oxidizing bacteria (NOB) abundance by controlling ultra-low dissolved oxygen (<0.1 mg/L) in the aerobic section where the contribution to nitrogen removal was 79.4 %. Microorganisms with different oxygen affinity spatially distributed on the carrier. Ammonia-oxidizing bacteria (AOB) dominated on the surface of the carrier, while anammox bacteria dominated on the interior of the carrier, with their relative abundance increasing from 0.26 % to 1.78 %. The intercalary NOB were inhibited by the restricted oxygen transfer. Overall, this study provides a new approach to realize PNA in biofilm system.

Study on Advanced Nitrogen Removal and Microbial Community Structure of Traditional Chinese Medicine Wastewater by a Novel System Coupling Anaerobic Sequencing Batch Reactor and Modified Sequencing Batch Biofilm Reactor

To improve the efficiency of nitrogen removal from pharmaceutical wastewater, wastewater from traditional Chinese medicine was treated in an anaerobic sequencing batch reactor (ASBR) combined with a modified sequencing batch biofilm reactor (SBBR). The chemical oxygen demand (COD) and total nitrogen (TN) contents were 3,750 ± 50 mg/L and 210 ± 10 mg/L, respectively. After 99 days of start-up and domestication, the COD, NH4+-N, and TN contents in the effluent were 230 ± 10 mg/L, 1 ± 0.5 mg/L, and 5 ± 3 mg/L, respectively, and the removal efficiencies reached more than 93.5, 99, and 96%, respectively. Among these results, the COD removal efficiency in traditional Chinese medicine wastewater with an ASBR reached more than 85%, and the effluent and raw water were mixed to adjust the C/N ratio in the SBBR influent. The initial operation mode of the improved SBBR was anaerobic–aerobic–anoxic. When the C/N ratio in the influent was adjusted to 5, the simultaneous nitrification and denitrification (SND) in the aerobic section was gradually enhanced, and the endogenous denitrification (ED) in the anoxic section gradually decreased. In conclusion, deep denitrification of the system was achieved only through SND, and the running time of the cycle was shortened from the initial 24 to 4.6 h. High-throughput sequencing analysis showed that the relative abundances of Bacteroidetes and Proteobacteria in the system were 39.69 and 37.34%, respectively. The content of Firmicutes with denitrification in the system was also high, accounting for 5.17%. At the genus level, the bacteria with denitrification functions in the system were mainly Thauera and unidentified_Sphingobacteriales, accounting for 5.67 and 1.66% of the system, respectively. In addition, there was heterotrophic nitrification–aerobic denitrification (HN-AD) activated in the system, including Denitratisoma, Paracoccus, and Pseudomonas. The total relative abundance of these bacteria was 0.612%. Their existence may be one of the reasons for the good effect of SND in this system.

The generation characteristics, pattern, and exposure risk of bioaerosol emitted in an A²O process wastewater treatment plant

Bioaerosols can be generated in wastewater treatment plants (WWTPs), they may contain pathogenic bacteria, cause disease transmission, and attract the public’s attention. In this study, bioaerosols were collected from seven different stages of an A²O process WWTP. The component characteristics were analyzed by bacterial culture and high-throughput sequencing. The correlations in different processes were analyzed, and the health risks of bioaerosols produced were evaluated. The results showed that the concentration range of bacteria aerosol in the WWTP was 75 CFU/m³−706 CFU/m³. The concentration range of total suspended particles was 111.13 µg/m³−211.67 µg/m³, the primary water-soluble ions were Ca²⁺ and Cl⁻. In the air of each stage, the main bacteria were Cetobacterium, Bacteroides, Romboutsia, and the fungi were Fusarium, Alternaria, and Aspergillus. The dominant bacteria in the wastewater were Cetobacterium, Romboutsia, Stenotrophobacter, and the fungi were Fusarium, Aspergillus, and Mortierella. The total bacterial concentration and ion concentration in the aerobic section of the biochemical tank were the highest. The results of species composition and principal component analysis showed that the bacterial composition in the air at different processes was similar, while the bacteria in wastewater differed significantly. Among them, the wastewater bacteria in the aerobic section of the biochemical tank were closer to that in the air. Fungal results were similar to bacteria but not prominent. The bioaerosol exposure risk results show that the risk in each stage was acceptable (5.15 ×10⁻⁴−6.47 ×10⁻³). However, the exposure risk of bioaerosol was calculated by the total bacterial concentration. In fact, some pathogenic microorganisms such as Escherichia coli and Aspergillus flavus were detected in bioaerosols, which may cause hemorrhagic colitis, cancer and other diseases by swallowing and inhalation. Therefore, the risk might be underestimated and should be a cause of concern.

Engineering application of an improved AAO process

An improved AAO process was designed in this study, in which the pre-anaerobic section was prepositioned and water inlet by two-points method was utilized. A regulating section was added between the anaerobic and aerobic sections, and could be switched to anaerobic or aerobic sections as needed to enhance the performance of nitrogen and phosphorus removal. On this basis, the process was applied to the Xihai Sewage Treatment Plant Project (Phase III), aiming to the treatment of domestic sewage with a scale of 8×104 m3/d. Characteristics, mechanisms and design parameters of the process were introduced and the operation results were analyzed in this study. It could be found that the removal efficiencies of COD, NH3-N, TP and SS were 89.36%, 96.89%, 95.99% and 96.78%, respectively. All the effluent indicators meet the first-level A standard in the “Pollutant Discharge Standard for Urban Wastewater Treatment Plant” (18918-2002).

Metagenomic insights into the explanation of biofilter performance distinction induced by dissolved oxygen increment

In this study, a set of novel double-layer-packed sequencing batch biofilm reactors (SBBRs) were constructed to treat secondary effluent with a low carbon-to-nitrogen ratio (C/N = 3.0). All the reactors were operated under identical conditions except dissolved oxygen (DO) in the aerobic section, which was controlled at seven different levels (0.5, 1.0, 1.5, 2.0, 2.5, 3.5 and 4.5 mg/L). It was found that the aerobic section contributed most to performance at an optimal DO of 2.0 mg/L. The change in DO accounted for the varied bacterial communities, which resulted in different performances. Both bacterial community structure and potential functions displayed close associations with performance implying nutrients were mainly removed by simultaneous nitrification-endogenous denitrification and phosphorus removal (SNEDPR) process. Moreover, the proliferation of nonfunctional nitrifiers/denitrifiers led to the inhibition of denitrification resulting in a lower removal of total dissolved nitrogen and phosphorus.

Temperature-induced difference in microbial characterizations accounts for the fluctuation of sequencing batch biofilm reactor performance.

Generally, the purification performance of bioreactors could be influenced by temperature variation via shaping different microbial communities. However, the underlying mechanisms remain largely unknown. Here, the variation trends of microbial communities in three sequencing batch biofilm reactors (SBBRs) under four different temperatures (15, 20, 25, 30°C) were compared. It was found that temperature increment led to an obvious enhancement in nutrient removal which was mainly occurred in the aerobic section. Meanwhile, distinct differences in dominant microbial communities or autotrophic nitrifiers were also observed. The performance of the SBBR reactors was closely associated with nitrifier communities since the treated wastewater was characterized by a severe lack of carbon sources (mean effluent COD ≤ 14.4mg/L). Spearman correlation unraveled that: most of the differentiated microbes as well as the dominant potential functions were strongly associated with nutrient removal, indicating the temperature-induced difference in microbial community well explained the distinction in purification performance.

Simultaneous nitrogen and carbon removal in a packed A/O reactor: effect of C/N ratio on microbial community structure.

In this research, a novel packed anoxic/oxic moving bed biofilm reactor (MBBR) was established to achieve high-organic matter removal rates, despite the carbon/nitrogen (C/N) ratio of 2.7-5.1 in the influent. Simultaneous nitrification-denitrification (SND) was investigated under a long sludge retention time of 104days. The system exhibited excellent performance in pollutant removal, with chemical oxygen demand and total nitrogen (TN) enhanced to 93.6-97.4% and 34.4-60%, respectively. Under low C/N conditions, the nitrogen removal process of A/O MBBR system was mainly achieved by anaerobic denitrification. The increase of C/N ratio enhanced SND rate of the aerobic section, where dissolved oxygen was maintained at the range of 4-6mg/L, and resulted in higher TN removal efficiency. The microbial composition and structures were analyzed utilizing the MiSeq Illumina sequencing technique. High-throughput pyrosequencing results indicated that the dominant microorganisms were Proteobacteria and Bacteroidetes at the phylum level, which contributes to the removal of organics matters. In the aerobic section, abundances of Nitrospirae (1.12-29.33%), Burkholderiales (2.15-21.38%), and Sphingobacteriales (2.92-11.67%) rose with increasing C/N ratio in the influent, this proved that SND did occur in the aerobic zone. As the C/N ratio of influent increased, the SND phenomenon in the aerobic zone of the system is the main mechanism for greatly improving the removal rate of TN in the aerobic section. The C/N ratio in the aerobic zone is not required to be high to exhibit good TN removal performance. When C/NH4+ and C/TN in the aerobic zone were higher than 2.29 and 1.77, respectively, TN removal efficiency was higher than 60%, which means that carbon sources added to the reactor could be saved. This study would be vital for a better understanding of microbial structures within a packed A/O MBBR and the development of cost-efficient strategies for the treatment of low C/N wastewater.

Effects of Aerobic Carbon Sources on Biofilm with Simultaneous Phosphate Removal and Enrichment

In a cyclic alternating O/A operation mode, phosphorus accumulating organisms (PAOs) can undertake phosphate removal and enrichment as the main process in wastewater treatment plants. The effects of the concentration of carbon sources during the aerobic stage on phosphate removal and enrichment performance of PAO biofilms, and the microbial population structure in the biofilms, were investigated. The results showed that the aerobic COD concentration decreased from 200 mg·L-1 to 0 mg·L-1, the phosphorus uptake rate improved by 1.29 times, the phosphorus concentration in effluent stabilized below 0.5 mg·L-1, the phosphorus release rate increased by 3.56 times, and the phosphate concentration in the circulating solution increased from 27.125 mg·L-1 to 55.91 mg·L-1. With respect to the change in microbial communities, the identification showed that the abundance of Proteobacteria increased by approximately two times, and the enrichment effects of Rhodocyclaceae and Anaerolineaceae increased by 2.28 and 5 times, respectively. Reducing the concentration of the carbon source in the aerobic section was beneficial to the screening and enrichment of PAOs, strengthening the removal of phosphate in the aerobic section and the release of phosphate in the anaerobic section. This resulted in an enriched phosphate solution. These observations provide a theoretical basis for future urban sewage treatment plants seeking to reduce their carbon demand.

Effect of intermittent operation model on the function of soil infiltration system.

To enhance denitrification in a process of solute infiltration through a soil, a two-section mixed-medium soil infiltration system (TMSIS) for urban non-point pollution was developed. The artificial aerobic respiration and nitrification took place in the upper aerobic section (AES), while grass powders and sawdust were mixed in the bottom anaerobic section (ANS) to supply organic carbon source for denitrification bacteria, and the reduction was increased by iron addition in the ANS. Measured resident concentrations from the bottom of each ANS column were assumed to represent mean values averaged over the column cross-sectional area. The TMSIS with hydraulic loading rates (HLR) of 0.32, 0.24, and 0.16m3m-2day-1 and with wetting-drying ratio (RWD) of 1.0 showed remarkable removal efficiencies for chemical oxygen demand (COD), NH4+-N, and TP, respectively. The hydraulic loading rate of 0.32m3m-2day-1 was selected as the optimal HLR due to the high contaminated runoff treatment efficiency. When RWD was 1.0, 0.5, or 0.2 with hydraulic loading rate of 0.32m3m-2day-1, the TMSIS could treat synthetic urban runoff contaminants very well. The corresponding effluent water met the China's national quality standard for class V surface water. The wetting-drying ratio of 0.5 with hydraulic loading of 0.32m3m-2day-1 was selected as the optimal operation conditions for the TMSIS. Aerobic respiration and nitrification mainly took place in the upper AES, in which most of the COD and the NH4+-N were removed. Mixed sawdust and grass powders used as a carbon source and heterotrophic denitrification were put at the bottom of the ANS. The developed TMSIS has the potential to be applied for urban non-point pollution removal.

Improvement of biological nitrogen removal with nitrate-dependent Fe(II) oxidation bacterium Aquabacterium parvum B6 in an up-flow bioreactor for wastewater treatment

Aquabacterium parvum strain B6 exhibited efficient nitrate-dependent Fe(II) oxidation ability using nitrate as an electron acceptor. A continuous up-flow bioreactor that included an aerobic and an anoxic section was constructed, and strain B6 was added to the bioreactor as inocula to explore the application of microbial nitrate-dependent Fe(II) oxidizing (NDFO) efficiency in wastewater treatment. The maximum NRE (anoxic section) and TNRE of 46.9% and 79.7%, respectively, could be obtained at a C/N ratio of 5.3:1 in the influent with HRT of 17. Meanwhile, the taxonomy composition of the reactor was assessed, as well. The NDFO metabolism of strain B6 could be expected because of its relatively dominant position in the anoxic section, whereas potential heterotrophic nitrification and aerobic denitrification developed into the prevailing status in the aerobic section after 50days of continuous operation.

Evaluation of Baffle Fixes Film up Flow Sludge Blanket Filtration (BFUSBF) System in Treatment of Wastewaters from Phenol and 2,4-Dinitrophenol Using Daphnia Magna Bioassay

Background: Phenol and nitrophenol are common compounds found in different types of industrial wastewater known as serious threats to human health and natural environment. In this study, Daphnia magna was used to evaluate the effectiveness of "baffle fixes film up flow sludge blanket filtration" (BFUSBF) system in elimination of phenolic compounds from water. Methods: D. magna cultures were used as toxicity index of phenol and 2,4-DNP mixtures after treatment by a pilot BFUSBF system which consisted of baffle in anoxic section and biofilm in aerobic sections. Initial concentrations were 312 mg/L phenol and 288 mg/L 2,4-dinitrophenol (2,4-DNP). Results: Bioassay tests showed that D. magna was influenced by the toxicity of phenol and 2,4 DNP mixtures. The comparison between the toxicity of initial phenol and 2,4-DNP mixtures and the output toxic unit (TU) derived from BFUSBF treatment system showed that the TU of the effluent from BFUSBF reactor was much lower than that of the solution that entered the reactor. Conclusion: Based on the acute toxicity test, BFUSBF process could reduce phenol and 2,4-DNP in aqueous solutions. Therefore, it is possible to use BFUSBF process as an appropriate treatment option for wastewaters containing phenolic compounds.

Biodegradation of Polychlorinated Biphenyls Using a Moving‐Bed Biofilm Reactor

As persistent organic pollutants, polychlorinated biphenyls (PCBs) are rarely degraded in nature environment. Biodegradation is an effective method for the removal of PCBs from contaminated wastewater. In this study, an assessment of the performance of a combined moving‐bed biofilm reactor and a membrane filtration system (MBBR‐MF) for the treatment of PCB‐containing wastewater was performed. Simulated wastewater containing PCB77 was treated in an MBBR system. PCB removal efficiency was investigated at different sections of the combined MBBR‐MF system. The results showed that the removal efficiencies for PCB77 in the anaerobic MBBR were 73 and 84.4% in the aerobic section. The possible biodegradation products were investigated. The results of gas chromatography–mass spectrometry indicate that the PCBs were converted into small molecules that were easily mineralized under aerobic conditions. Thus, the MBBR technology could have potential for biodegradation use of PCB‐contaminated wastewater.

Effects of the Filler Properties on Removal Nitrogen of Wastewater in Hybrid Biofilm-Activated Sludge Process

To develop the proper filler for improving removal efficiency of ammonia nitrogen in the activated sludge process of wastewater treatment, the effects of the filler properties and treatment conditions on removal efficiency of ammonia nitrogen in hybrid biofilm-activated sludge process were investigated by the lab-scale test and pilot-scale test. Moreover, the feasibility of simultaneous nitrification and denitrification (SND) was explored with biofilm treatment for chemical poor-biological wastewater. The results showed that SND occurred in the aerobic section. The effluent total basicity (TB) in biofilm process was more than 2mmol / L, higher than activated sludge process. Correspondingly, the effluent TB in activated sludge process was about 0.1mmol / L, and nitrate produced by activated sludge process was 30 mg/L higher than biofilm process. Under the condition of HRT of 24 h for hydrolysis-acidification tank, HRT of 4 h for anoxic tank and HRT of 16 h for aerobic tank, effluent NOˉx-N with combination type of filler in biofilm process was 20mg/L less than that with the activated sludge process. TB with combination type of filler in biofilm process was 2mmol/L less than that with the activated sludge process. Nitrogen removal efficiency was 10.46% with SJ-1 type of filler (made in Jiangsu Suzhou Purification Group Co.,Ltd) more than with combination type of filler. The effluent NOˉx-N concentrations was less than.15mg/L in biofilm process with SJ-1 type of filler. A practical mathematical model with the A/O process was developed for predicting removal effects, which can provide a theoretical guidance for wastewater treatment and engineering design.