Strategies to attenuate ciprofloxacin inhibition on enhanced biological phosphorus removal from wastewater and its recoverability.

The inhibiting effects of ciprofloxacin (CIP) on enhanced biological phosphorus removal (EBPR) were investigated with no change in reactor operation and with increased aeration rate and sludge retention time (SRT) to explore inhibition-alleviating solutions. Additionally, performance recoverability was evaluated. The results showed that the phosphorus removal efficiency in the presence of 0.002-0.092 mg/L CIP for 7 days was only 12.5%. Increasing the aeration rate relieved inhibition (33.5% phosphorus removal efficiency on Day 7), and increasing SRT slowed EBPR performance deterioration. The EBPR performance recovered from CIP inhibition and increases in the aeration rate and SRT resulted in different recovery phenomena. The maximum PO43--P release rate continued to decrease in the first 2 days of the recovery stage and then gradually increased. However, the maximum PO43--P uptake rate immediately increased at different rates among reactors, which might be attributed to variations in the microbial community structure, decreased poly-P content, and enhanced abundances of ABC transporters and quorum sensing. It was found that some microorganisms associated with phosphorus removal were more tolerant to CIP than glycogen accumulating organisms. Moreover, the increased relative abundance of the qepA gene indicated that the microorganisms in the EBPR system had strong antibiotic resistance capacity. The bacterial community structure was significantly affected by CIP and could not recover to the initial structure. The results help to provide technical support for the operation of the EBPR process in the presence of CIP and to increase the understanding of system recoverability.

Handling the inhibitory role of product accumulation during sophorolipid fermentation in a bubble column reactor with an in situ foam recovery.

Sophorolipid (SL) production by Candida catenulata from sunflower fatty acids was studied in a bubble column reactor (BCR). The specific oxygen uptake rate was 0.021 mg gcell-1 min-1 which indicates the importance of aeration in SL biosynthesis. The measurement of oxygen transfer rate (OTR) in the BCR showed a satisfactory OTR value of about 0.093 min-1 in the system. However, further SL production was stopped after 30 h in the BCR mainly due to the product accumulation in the culture and its inhibitory effects on cell growth and SL synthesis. Since an extensive foam was generated in the BCR under the absence of an antifoam agent, the development of an in situ foam recovery system provided the integration of production and separation of SL to handle the problem. The application of the foam recovery system enhanced biomass and titer SL concentration by 38.5 and 28.2% in comparison with the conventional BCR, respectively. Further studies in the system were performed by monitoring the size of bubbles and their effects on the biomass and SL enrichment in the foam stream at different aeration rates where the SL enrichment varied from 900 to 100% at 12 and 50 h of the fermentation.

Effect of ultrasound on the stability of partial nitrification: Under the interference of aeration rate.

The fluctuation of dissolved oxygen is one of the primary cause of disruptions to the consistent operation of partial nitrification, and the level of dissolved oxygen is mainly controlled by the aeration rate. This study investigated the influence of ultrasonic treatment on the stability of partial nitrification of activated sludge under different aeration conditions. After being treated with ultrasound (energy density = 0.20 W·mL-1, treatment time = 10 min), partial nitrification process operated stably for 67 days, with the nitrite accumulation rate above 83.89 %. The effluent contained 42.50 mg·L-1 of nitrite, much higher than the control reactor (0.30 mg·L-1). The gap between the specific ammonia and nitrite oxidation rates widened continuously as the aeration rate increased, and nitrite-oxidizing bacteria activity did not recover even under conditions with a very high oxygen content. Further analysis showed that ultrasonic treatment had obvious stripping effect on excess extracellular polymeric substances (EPS), especially loosely bound EPS and protein. Additionally, long-term ultrasonic treatment promoted the enrichment of Nitrosomonas and strongly inhibited Nitrotoga. Based on these findings, it appears that under conditions of high aeration rate, ultrasound effectively suppress the recovery of Nitrotoga activity and improve the stability of partial nitrification.

The influence of aeration rate on the sorption of emerging pharmaceuticals in activated sludge.

The sorption of pharmaceuticals on activated sludge during the wastewater treatment process has been widely studied and considered one of the main mechanisms for the removal of these micropollutants from domestic sewage. Understanding the removal mechanism is important to reduce the environmental risk associated with these compounds. To the best of our knowledge, no data are reporting the influence of the aeration rate and, consequently, of the physicochemical properties of the sludge flocs, on the sorption of pharmaceutical compounds. In this context, the influence of the aeration rate (2, 5, and 8 L min-1) on the physical properties of the sludge and the sorption of two emerging pharmaceuticals, 17-alpha-ethynylestradiol (EE2) and diclofenac (DCF), was evaluated. The pharmaceuticals were analyzed by Solid Phase Extraction and Liquid Chromatography, and the sludge by Laser Particle Size Analyzer and Settling Curves. As a result, higher sorption for 17-alpha-ethinylestradiol (78-96%) in comparison to diclofenac (23-43%) was observed, corroborating the greater hydrophobicity of EE2. Higher pharmaceuticals removal rates were observed for the highest aeration (10.02 µgEE2 gSST-1 and 3.99 µgDCF gSST-1) in comparison to the lowest one (7.81 µgEE2 gSST-1 and 2.58 µgDCF gSST-1), what can be attributed to structural and surface changes in flocs. Smaller and more dispersed flocs were observed when aeration was increased (104.4 µm for 8 L min-1 and 63.8 µm for 2 L min-1). The results suggest that the increase in aeration seems to be promising for the removal of pharmaceuticals by sorption in sewage sludge, especially for the hydrophobic ones.

A first-order kinetic model for simulating the aerobic degradation of municipal solid waste.

Aerobic degradation models are important tools for investigating the aerobic degradation behavior of municipal solid waste (MSW). In this paper, a first-order kinetic model for aerobic degradation of MSW was developed. The model comprehensively considers the aerobic degradation of five substrates, i.e., holocellulose, non-cellulosic sugars, proteins, lipids and lignin. The proportion ranges of the five substrates are summarized with the recommended values given. The effects of temperature, moisture content, oxygen concentration and free air space (FAS) on the reaction rates are considered, and the effect of settlement is accounted for in the FAS correction function. The reliability of the model was verified by comparing simulations of the aerobic degradation of low food waste content (LFWC-) and high food waste content (HFWC-) MSWs to the literature. Afterwards, a sensitivity analysis was carried out to establish the relative importance of aeration rate (AR), volumetric moisture content (VMC), and temperature. VMC had the greatest influence on the aerobic degradation of LFWC-MSW, followed by temperature and then AR; for HFWC-MSW, temperature was the most important factor, then VMC and last was AR. The degradation ratio of LFWC-MSW can reach 98.0% after 100 days degradation under its optimal conditions (i.e., temperature: 55 °C, VMC: 40%, AR: 0.16 L min-1 kg-1 DM), while it is slightly higher as 99.5% for HFWC-MSW under its optimal conditions (i.e., temperature: 55 °C, VMC: 40%, AR: 0.20 L min-1 kg-1 DM).

The Effect of Cultivation Conditions on Antifungal and Maize Seed Germination Activity of Bacillus-Based Biocontrol Agent.

Aflatoxin contamination is a global risk and a concerning problem threatening food safety. The biotechnological answer lies in the production of biocontrol agents that are effective against aflatoxins producers. In addition to their biocontrol effect, microbial-based products are recognized as efficient biosolutions for plant nutrition and growth promotion. The present study addresses the characterization of the representative of Phaseolus vulgaris rhizosphere microbiome, Bacillus sp. BioSol021, regarding plant growth promotion traits, including the activity of protease, cellulase, xylanase, and pectinase with the enzymatic activity index values 1.06, 2.04, 2.41, and 3.51, respectively. The potential for the wider commercialization of this kind of product is determined by the possibility of developing a scalable bioprocess solution suitable for technology transfer to an industrial scale. Therefore, the study addresses one of the most challenging steps in bioprocess development, including the production scale-up from the Erlenmeyer flask to the laboratory bioreactor. The results indicated the influence of the key bioprocess parameters on the dual mechanism of action of biocontrol effects against the aflatoxigenic Aspergillus flavus, as well on maize seed germination activity, pointing out the positive impact of high aeration intensity and agitation rate, resulting in inhibition zone diameters of 60 mm, a root length 96 mm, and a shoot length 27 mm.

Extended batch cultures for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) production by Azotobacter vinelandii OP growing at different aeration rates.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a polymer produced by Azotobacter vinelandii OP. In the bioreactor, PHBV production and its molar composition are affected by aeration rate. PHBV production by A. vinelandii OP was evaluated using extended batch cultures at different aeration rates, which determined different oxygen transfer rates (OTR) in the cultures. Under the conditions evaluated, PHBV with different 3-hydroxyvalerate (3HV) fractions were obtained. In the cultures with a low OTR (6.7 mmol L-1 h-1, at 0.3 vvm), a PHBV content of 38% w w-1 with 9.1 mol % 3HV was achieved. The maximum PHBV production (72% w w-1) was obtained at a high OTR (18.2 mmol L-1 h-1, at 1.0 vvm), both at 48 h. Thus, PHBV production increased in the bioreactor with an increased aeration rate, but not the 3HV fraction in the polymer chain. An OTR of 24.9 mmol L-1 h-1 (at 2.1 vvm) was the most suitable for improving the PHBV content (61% w w-1) and a high 3HV fraction of 20.8 mol % (at 48 h); and volumetric productivity (0.15 g L-1 h-1). The findings indicate that the extended batch culture at 2.1 vvm is the most adequate mode of cultivation to produce higher biomass and PHBV with a high 3HV fraction. Overall, the results have shown that the PHBV production and 3HV fraction could be affected by the aeration rate and the proposed approach could be applied to implement cultivation strategies to optimize PHBV production for different biotechnological applications.

Effects of carbon/nitrogen ratio and aeration rate on the sheep manure composting process and associated gaseous emissions.

There are several issues such as low maturity degree of compost product and severe pollution gas emissions during the composting process. Carbon/Nitrogen (C/N) ratio and aeration rate (AR) are the most important factors affecting the composting performance. According to the results of previous studies, the proper C/N ratio and AR were 20-30:1 and 0.1-0.4 L kg-1 DM·min-1, respectively. Therefore, a lab-scale experiment was conducted to investigate the effects of C/N ratio and AR on sheep manure composting process and associated gaseous emissions. The initial C/N ratio in this experiment were set at 23, 26 and 29 to simulate the C/N ratio at low, medium and high levels. The AR were decided at 0.12, 0.24 and 0.36 L kg-1 DM·min-1 to simulate the aeration at low, middle and high levels. The results showed that as the C/N ratio or AR increased, the methane (CH4) and hydrogen sulfide (H2S) emissions decreased. The nitrous oxide (N2O) emission peaked at the low C/N ratio or AR treatments. The total greenhouse gas (GHG) emissions decreased with the increase of C/N ratio or AR, and the maximum value occurred in the treatment with C/N ratio 23 and AR 0.24 L kg-1 DM·min-1. In the treatment with C/N ratio 26 and AR 0.36 L kg-1 DM·min-1, the GI value of compost product was the highest (about 250%), and the total greenhouse effect was the lowest (2.36 kg CO2-eq·t-1 DM). Therefore, considering reduction of pollution gas emissions and improvement of the quality of compost products comprehensively, the optimum conditions were initial C/N ratio 26 and AR 0.36 L kg-1 DM·min-1 during the co-composting of sheep manure and cornstalks. In addition, the key physicochemical factors and eight key bacterial communities were determined to regulate compost maturity and pollution gas emissions during the sheep manure composting, which could provide scientific support and theoretical reference for controlling pollution gas emissions and obtaining high quality sheep manure compost products.

The effect of preparation time and aeration rate on the properties of bulk micro-nanobubble water using hydrodynamic cavitation.

Fundamental research on bulk micro-nanobubbles (BMNBs) has grown rapidly due to the demand for their industrial applications and potential role in interfacial sciences. This work focuses on examining properties of such bubbles, including the number, concentration, zeta potential, and surface tension in water. For this purpose, BMNBs were generated by the hydrodynamic cavitation (HC) mechanism. Distilled water and air in the experiments were the liquid and gas phases, respectively. The characterization of bulk microbubbles (BMBs) and bulk nanobubbles (BNBs) were performed through focused beam reflectance measurement (FBRM) and nanoparticle tracking analysis (NTA) techniques, respectively. Zeta potential and surface tension of aqueous solutions were measured at different time and aeration rates. The results showed that aeration rate and preparation time had an important role in the properties of BNBs (concentration, bubble size, and surface charge) and BMBs (number, and bubble size). The instability of BMBs led to the rapid changes in the dissolved oxygen (DO) content in the water. The number of BMBs decreased when preparation time and aeration rate increased, but their size remained constant. By enhancing the preparation time and aeration rate, the concentration of BNBs improved first and then reduced. Additionally, the surface tension of an aqueous solution containing BNBs was significantly lower than that of pure water.

Investigation and evaluation of membrane fouling in a microbial fuel cell-membrane bioreactor systems (MFC-MBR).

Two membrane bioreactors with and without adding an electric circuit (named as MFC-MBR and C-MBR, respectively) were established to investigate the effects of micro-electric field on membrane fouling. With the aeration rate of 1.5 L/min, the synergistic effect of aeration and micro-electric field was the best in reducing membrane fouling and COD in treatment of a simulated phenol wastewater. Compared with C-MBR, the running time of MFC-MBR was extended for 16 days. Scanning electron microscope (SEM) and energy-dispersive X-ray detector (SEM-EDX) demonstrated that less foulants were attached to the membrane and the attachment was loosend in MFC-MBR. The decreased absolute value of zeta potential indicated repulsion among the negatively-charged sludge particles was reduced and flocculation of the sludge was improved, which alleviated the membrane fouling. The soluble microbial products (SMP) and loosely-bound extracellular polymeric substances (LB-EPS) were also decreased in MFC-MBR. It was found that migration and neutralization of the negatively-charged particles, and degradation of microorganisms contributed to the alleviation of membrane fouling. Moreover, the decreases of carbohydrates in LB-EPS led to higher protein/carbohydrates (PN/PS) ratio, which was a key parameter for alleviating membrane fouling. Meanwhile, the increase of tightly bound extracellular polymeric substances (TB-EPS) could also slow down membrane fouling. Because TB-EPS can be used as a binder to strengthen the flocculation of sludge particles.

Aeration rate improves the compost quality of food waste and promotes the decomposition of toxic materials in leachate by changing the bacterial community.

The effect of aeration rates on maturity, leachate and bacterial community succession during a pilot-scale food waste composting were evaluated. Out of the four aeration rates (0.44, 3.25, 6.50 and 11.65 L kg-1 DM initial min-1 for T1, T2, T3 and T4, respectively) that were conducted, results found T2 to be the recommended ventilation rate considering the quality of compost and the leachate utilization. Higher ventilation increased germination index of diluted leachate. The abundance of Proteobacteria in mesophilic stage (35.5%) and Actinobacteria in cooling stage (30.6%) in T4 were higher than in other groups (7.9%-17.5%), suggesting the formation of a select community categorized by the capacity of degrading the organic matter and promoting maturity. The key bacteria of aeration-shaped bacterial communities such as Sporosarcina, Pseudomonas and Thermobifida were identified and they could be manipulated by increasing NH4+, NO3- contents and pH in the initial stage of composting.

Characteristics of organic carbon metabolism and bioremediation of petroleum-contaminated soil by a mesophilic aerobic biopile system.

An innovative mesophilic aerobic biopile technology was explored to improve the bioremediation efficiency of petroleum-contaminated soil. Under the suitable soil conditions (C:N:P at 100:5:1 and soil moisture content at 18%), the soil pH was hold in the range of 7.4 to 6.8 throughout the bioremediation process, the mesophilic (30 °C-40 °C) and forced aeration (3 h-on/1 h-off) conditions were the critical factors to enhancing petroleum biodegradation. The consumption of bioavailable organic carbon (BAC) which was one of the most important factors regulating microbial metabolism, was positively related (R2 = 0.85, 40 °C) with the rate of petroleum removal. The 50% threshold of BAC could be regarded as the signal for supplementing the soil nutrients in the mesophilic aerobic biopiles to favor petroleum removal. The optimal conditions (40 °C, 3 h-on/1 h-off) maximized the utilization of BAC, promoted the petroleum degradation, and remained the microbial abundance and community composition stable to the greatest extent. In addition, the accumulation of aliphatic acids affected the microbial activity, which limited the efficiency of petroleum degradation to a certain extent. Jointly considering the energy consumption, time cost and soil conditions maintenance, a cost-effective biopile technology was obtained by temperature and aeration regulation and BAC supplementation, which could be applied to engineering application.

Ancillary palm oil fuel ash (POFA) in sequencing batch reactor for enhancing recalcitrant pollutants removal from domestic wastewater.

Domestic wastewater has been generated massively along with rapid growth of population and economic. Biological treatment using sequencing batch reactor (SBR) augmented with palm oil fuel ash (POFA) was investigated for the first time. The performance of POFA in enhancing biological treatment of wastewater has not been tested. The porosity property of POFA can improve SBR efficiency by promoting growth of mixed liquor suspended solids (MLSS) and formation of larger flocs for settling and facilitating attachment of microorganisms and pollutants onto POFA surfaces. The properties of POFA were tested to identify morphological properties, particle size, surface area, chemical compositions. Four SBRs, namely SBR1, SBR2, SBR3 and SBR4 were provided with aeration rate of 1, 2, 3 and 4 L/min, respectively. Each reactor was augmented with different dosages of POFA. Optimum aeration rate and POFA concentration were identified by the performance of SBRs in removing chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N) and colour from domestic wastewater. The results showed the most efficient COD (97.8%), NH3-N (99.4%) and colour (98.8%) removals were achieved at optimum POFA concentration of 4 g/L in SBR and aeration rate of 1 L/min. The study also found that higher aeration rate would contribute to the smaller specific size of flocs and decrease the pollutant removal efficiency.

Recommended turbulent energy dissipation rate for biomass and lipid production of Scenedesmus obliquus in an aerated photosynthetic culture system.

Effects of turbulent energy dissipation rate (increased from 1.28 × 10-6 to 1.67 × 10-5 m2 s-3) on Scenedesmus obliquus biomass and lipid accumulation at different aeration rates (0.3, 0.6, 0.9, 1.2, and 1.5 L min-1) were investigated. The turbulent energy dissipation rate was calculated by CFD model simulation. When the turbulent energy dissipation rate increased to 7.30 × 10-6 m2 s-3, the biomass and lipid productivity increased gradually, and finally reached their maximum values of 1.11 × 107 cells mL-1 and 16.0 mg L-1 day-1, respectively. When it exceeded 7.30 × 10-6 m2 s-3, the biomass and lipid productivity showed a decreasing trend. Therefore, the most favorable turbulent energy dissipation rate for S. obliquus growth and lipid accumulation was 7.30 × 10-6 m2 s-3.

Investigation of antifouling properties of polypropylene/TiO2 nanocomposite membrane under different aeration rate in membrane bioreactor system.

This paper presents the results of aeration rate effect on antifouling properties of polypropylene (PP)/TiO2 nanocomposite membrane in membrane bioreactor (MBR) system in order to oil refinery wastewater treatment. For this purpose, three levels of aeration rate with specific aeration demand per membrane area (SADm) of 0.5, 1, and 1.5 m3/m2h was used. According to the obtained results, PP nanocomposite membrane showed high hydrophilicity, porosity, and high flux compared to neat PP membrane. Also, either low or high aeration rate had a negative influence on permeability and antifouling properties of neat PP and nanocomposite membranes. The analysis of fouling mechanism for both membranes based on Hermia's model revealed that the cake formation is dominant mechanism for lower aeration rate while by increasing aeration rate, all models couldn't predict experimental data. Meanwhile, by increasing aeration rate, chemical oxygen demand (COD) removal for activated sludge and both membranes decreased and increased, respectively.

Effect of aeration rate on the anti-biofouling properties of cellulose acetate nanocomposite membranes in a membrane bioreactor system for the treatment of pharmaceutical wastewater.

In this study, the effect of aeration rate in terms of specific aeration demand per membrane area (SADm) on the anti-biofouling properties of cellulose acetate (CA) nanocomposite membranes (CA/ND-NH2) in a membrane bioreactor system was investigated. The amount of EPS and soluble EPS under high aeration rate conditions was observed to be higher than under low aeration rate conditions. The results obtained showed that either lower or higher aeration rates had a negative impact on membrane permeability. The high aeration rate resulted in a severe breakage of sludge flocs, and promoted the release of soluble EPS from the microbial flocs to the bioreactor tank. By increasing the aeration rate, the COD removal increased and decreased respectively for the membranes and the activated sludge. It was finally concluded that higher anti-biofouling properties of neat CA and nanocomposite membranes were obtained under optimal aeration rate conditions (SADm = 1 m3 m-2 h-1).

Performance of microbial fuel cells based on the operational parameters of biocathode during simultaneous Congo red decolorization and electricity generation.

A biocathode microbial fuel cell was constructed to investigate Congo red decolorization and power generation under different cathode operational parameters. The results showed that the suspended sludge in the cathode could improve the performance of the microbial fuel cell for electricity generation but had a negligible effect on the Congo red decolorization. The maximum voltage increased as the aeration rate was increased up to 100 mL/min. At aeration rates of 150 and 200 mL/min, the maximum voltage was lower than that at 100 mL/min. In the meantime, the Congo red decolorization efficiency decreased with increasing cathode aeration rate. These results showed that excessive aeration is not favorable in a bio-cathode microbial fuel cell used for simultaneous Congo red decolorization and electricity generation. The addition of Mn2+ to the biocathode resulted in a 74.5% increase in maximum power density but had no effect on Congo red decolorization. SEM and 16S rRNA sequencing analysis confirmed that Mn2+ was involved in the electrochemical reaction of the biocathode as an electron mediator, and it could induce a difference in the biocathode-attached populations.

Effects of aeration on microbes and intestinal bacteria in bioaerosols from the BRT of an indoor wastewater treatment facility.

The generation and emission of airborne bacteria from a biochemical reaction tank (BRT) for wastewater treatment was investigated by altering the aeration rate. The levels of bioaerosols increased from 715 ±â€¯69 to 1597 ±â€¯135 CFU/m3 (total airborne bacteria) and from 78 ±â€¯6 to 359 ±â€¯18 CFU/m3 (intestinal bacteria) as the aeration rate increased from 0.3 to 1.2 m3/h. Most airborne bacteria were attached to particles smaller than 4.7 µm at an aeration rate of 0.3 m3/h. They were found attached to larger particles (>4.7 µm) when the aeration rate increased to 1.2 m3/h. A similar phenomenon was observed for intestinal bacteria. The high-throughput sequencing technique was used to assay the microbial populations of the bioaerosols. Both microbial counts and diversity increased as the aeration rate increased. Brevundimonas (63.82%), Chryseobacterium (16.54%), and Micrococcaceae (12.37%) were the dominant intestinal bacteria at an aeration rate of 0.3 m3/h. Pseudochrobactrum (33.10%), Citrobacter (21.28%), and Yersinia (18.21%) were the dominant intestinal bacteria at an aeration rate of 1.2 m3/h. The level, particle size distribution, population structure, and diversity of the bioaerosols were all affected by aeration rate. The source tracker results indicated that water and the surrounding air were the two main bioaerosol sources. The contribution of water is greater at larger levels of aeration. Inhalation was the main pathway of microbial aerosol intake for people in the surrounding area. The exposure hazard quotients for adult males were generally higher than those for adult females. Necessary measures should be taken to ensure worker safety.

Application of a microbial fuel cell-based biosensor for the energy-saving operation of macrophyte residues bioreactor with low concentration of dissolved organic carbon in effluents.

The increasing application of plant residues bioreactor for aquatic environment remediation may release numerous dissolved organic carbon (DOC) into aquatic ecosystems. In this study, a microbial fuel cell (MFC) sensor was integrated with a macrophyte residues bioreactor (MRBR) to provide an energy-saving way for reduction of DOC concentrations in the effluent. Through re-utilization of macrophyte residues as solid carbon source, DOC concentrations in the effluent of MRBR increased to the maximum on day 5 and then dropped down rapidly to a low value, while the ratio of bioavailable DOC decreased gradually. Interestingly, it was found that there existed a linear relationship between DOC concentrations in initial residue leachate and the voltage from MFC biosensor (R2 = 0.9852). Accordingly, aerobic biofilm through aeration were applied in the upper part of MRBR to enhance the degradation of DOC prior to discharge to aquatic systems, and aeration rate was adjusted based on MFC sensor signal. Further experiments demonstrated that when voltage decreased from 0.18 V to 0.09 V, a half of aeration rate (7.5 L min-1) could still lead to a high DOC degradation efficiency (above 50%) and a low DOC concentration (∼10 mg L-1) in the reactor effluent. Thus, the integrated MFC signal could be used to regulate the aeration rate in order to obtain a low DOC concentration in effluents under an energy-saving way.

[Effect of Aeration Rate on Shortcut Nitrification Recovery in Intermittent Aeration Mode].

Shortcut nitrification sludge, which was set aside for two months, was recovered using Reactors Ⅰ, Ⅱ, Ⅲ, and Ⅳ. The aeration rates of Reactors Ⅰ, Ⅱ, Ⅲ, and Ⅳ were 120, 100, 80, and 60 L·h-1, respectively, while treating real domestic sewage, and the ratio of aerobic/anoxic was 30 min/30 min at the temperature of 25℃. The influent of ammonia was 50-80 mg·L-1, and the concentration of effluent ammonia was stable, at below 5 mg·L-1, after the 12th, 18th, 21st, and 21st cycles. The removal ratio of ammonia nitrogen was about 95%. The highest concentrations of nitrite for Reactors Ⅰ, Ⅱ, Ⅲ, and Ⅳ were 20.83, 22.81, 21.50, and 20.73 mg·L-1, respectively, which occurred in the 30th, 35th, 38th, and 42nd cycles, respectively. The concentrations of effluent nitrate were lower than 0.5 mg·L-1, and the nitrite accumulation rates were higher than 99%. The activity of ammonia-oxidizing bacteria (AOB) increased gradually and finally stabilized at 100.00%; however, the activity of nitrite-oxidizing bacteria (NOB) was gradually inhibited. The recovery of shortcut nitrification was achieved successfully in the different aeration modes.