Effluent COD Concentration Research Articles

Mainstream upflow nitritation-anammox system with hybrid anaerobic pretreatment: Long-term performance and microbial community dynamics

Mainstream nitritation-anammox is of strong interest to energy- and resource-efficient domestic wastewater treatment. However, there lack in-depth studies of pretreatment, tests of actual wastewater, and examination of long-term performance. Herein, an upflow nitritation-anammox granular reactor has been investigated to treat primary effluent with a hybrid anaerobic reactor (HAR) as pretreatment for more than 300 days. This system achieved 92% of COD removal, 75% of which was accomplished by the HAR, and had an average final effluent COD concentration of 22 mg L−1. More than 90% of ammonium was removed in the nitritation-anammox reactor, achieving a nitrogen removal rate of 81.0 g N m−3 d−1 in the last stage. The accumulation of sulfate-reducing bacteria in the HAR evidenced the effect of sulfate on COD removal and subsequent nitrogen removal. Anammox bacteria (predominantly Ca. Jettenia asiatica) accounted for up to 40.2% of total granular communities, but their abundance decreased over time in the suspended communities. The dynamics of major metabolisms and functional genes involved in nitrogen conversion were predicted by PICRUSt based on the taxonomic data, providing more insights into the functions of the microbial communities. These results have demonstrated the effectiveness and importance of anaerobic pretreatment to successful mainstream nitritation-anammox.

Combination of Microbubble Catalytic Ozonation and Biological Process for Advanced Treatment of Biotreated Coal Chemical Wastewater

A combination of microbubble catalytic ozonation and biological process was used for advanced treatment of biotreated coal chemical wastewater (BCCW). The performance of the combination system and the influence of the ratio of ozone dosage to influent COD were investigated. The results indicated that the refractory nitrogen-containing aromatics in the BCCW was degraded efficiently by microbubble catalytic ozonation, which resulted in some COD removal, ammonia nitrogen release, and significant improvement of biodegradability. The ozone utilization efficiency was close to 100% and the off-gas ozone did not need to be treated. Sufficient dissolved oxygen (DO) was provided by the microbubble catalytic ozonation for biological treatment without aeration. COD and ammonia nitrogen were removed further in the biological treatment efficiently. Better performance of the combination system was achieved when the system effluent reflux ratio was 30% and the ratio of ozone dosage to influent COD was 0.44 mg·mg-1. In this case, for microbubble catalytic ozonation, the COD removal efficiency was 42.5%, the ratio of ozone consumed to COD removed was 1.38 mg·mg-1, and the ozone utilization efficiency was 98.0%. For biological treatment, the COD removal efficiency was 42.3%. For the combination system, the total COD removal efficiency was 66.7%, the average final effluent COD concentration was 91.5 mg·L-1, and the estimated total ratio of ozone consumed to COD removed was 0.68 mg·mg-1, indicating better technical and economic performance.

Enhanced nitrogen removal using solid carbon source in constructed wetland with limited aeration

In this study, the performances of nitrogen removal in constructed wetlands using solid carbon source with limited aeration were investigated. The blends of poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) and polyacetic acid (PLA) were used as the carbon source and biofilm support. The performances of nitrogen removal, microbial abundance and microbial community structure in the biofilm attached on PHBV/PLA were investigated. Higher ammonia removal efficiency (91.00%) and total nitrogen removal efficiency (97.03%) than non-aerated constructed wetland (System NA) were achieved in constructed wetland with limited aeration (System A). The limited aeration decreased the average concentrations of COD in effluent. And, System A had higher microbial abundance than System NA. Pyrosequencing analysis showed that denitrifying bacteria Brevinema (41.85%) and Thiothrix (12.33%) were the predominant genus in the biofilm attached on the carbon source in System NA and System A, respectively.

Metagenomic and metabolomic analysis reveals the effects of chemical phosphorus recovery on biological nutrient removal system

Side-stream phosphorus recovery coupled with biological nutrient removal can achieve the dual goals of resource recycling and meeting effluent discharge standards in wastewater treatment processes. However, suboptimal side-stream ratios (SSRs) for phosphorus recovery exert a negative effect on the performance of the combined process. The aim of this study was to reveal the comprehensive effect of chemical phosphorus recovery on the biological nutrient removal process using combined bio-omics (metagenomics and metabolomics) analysis. The optimal SSR was 0.3, at which point the effluent concentrations of COD, TN, NH4+-N and TP were approximately 32.56, 11.35, 3.71 and 0.23mg/L, respectively. Initially increasing the SSR favored resource recovery; however, SSRs>0.3 disrupted the phosphorus balance of the system and inhibited the metabolic activity of microorganisms related to the phosphorus removal process. Variations of activated sludge characteristics at different SRR indicated that the polysaccharide were more important than protein in resisting the toxicity of the imported Ca2+ on microorganisms. Relevant changes in the microbial community, functional potential, key enzymes and intracellular metabolites were illustrated in the bio-omics analysis, which revealed the influencing mechanism of chemical phosphorus recovery on activated sludge system at the micro level. The results of this study provide a novel perspective on the interactions between resource recovery and pollutant removal in a combined process using a bio-omics approach.

Comparison research on denitrification efficiency of two types of solid carbon source

C/N rates can greatly influence efficiency of denitrification. It is difficult for current treated effluent to reach GB18918-2002 primary effluent standard because of its low C/N rate. To improve the efficiency of denitrification, the quality of effluent, and realize the waste recycling, this article selected magnolia leaves and degradable meal box as the solid carbon source for periodic denitrification stage to study the change of NO3--N, TN, COD, NO2--N, NH4+, PO43- and color. The results showed that in the condition of influent nitrate concentration of 40 mg/L, carbon dosage of 10 g, the reaction temperature of 25°C the nitrate removal rates of magnolia leaves and degradable meal box reached 89.0% and 56.3% respectively, and the TN removal rates reached 91.7% and 53.9% respectively. But in the aspect of final treated effluent COD concentration level, magnolia leaves experiment (608 mg/L) was much higher than the degradable meal box (78 mg/L). Besides, the accumulation of nitrite, the released concentration of ammonia nitrogen and phosphate of magnolia leaves experiment were also higher than the degradable meal box. Under the integrated analysis, the magnolia leaves are more suitable than the degradable meal box as the denitrification external carbon source.

Nitrogen Removal of Municipal Wastewater by ANAMMOX Coupled Shortcut Nitrification in Anaerobic Baffled Reactor

If the technology of anaerobic ammonium oxidation(ANAMMOX) can substitute the mainstream technology of municipal wastewater treatment plant, the energy of municipal wastewater treatment will be decreased significantly. Thus, anaerobic baffled reactor(ABR) was used to build carbon system, shortcut nitrification system and anaerobic ammonia oxidation system. And the three systems were coupled to shortcut nitrification-anaerobic ammonia oxidation reactor to treat municipal wastewater. The results showed that the average effluent COD concentration of carbon removal system was 80 mg·L-1 when the hydraulic retention time of carbon removal system was 4.5 h. And the subsequent shortcut nitrification system would not be adversely affected by the effluent COD. Finally, the average effluent total nitrogen concentration was 10 mg·L-1, with total nitrogen volume load of ANAMMOX system of 0.36 kg·(m3·d)-1. When the dissolved oxygen was controlled between 1 to 2 mg·L-1, the nitrite accumulation rate could be maintained around 90%, ensuring the stable operation of the subsequent anaerobic ammonia oxidation system. The nitrogen of municipal wastewater could be stable and efficiently removed by the shortcut nitrification -ANAMMOX integration ABR with temperature of 30℃ and dissolved oxygen of 1-2 mg·L-1.

Start-up performance of a woodchip bioreactor operated end-of-pipe at a commercial fish farm—A case study

There is a need for simple, maintenance-free technologies for removing nitrogen (N) from aquaculture effluents. Denitrifying woodchip bioreactors have been used successfully to remove nitrate-N (NO3-N) from ground and surface waters and may potentially be applied to dilute aquaculture effluents as well. Real-life applicability in commercial, outdoor fish farms including practical start-up issues such as e.g. time till stable performance and potential leaching are, however, unknown to the industry.This case study consequently investigated the temporal performance of a woodchip bioreactor (12.5m3) during start-up. The bioreactor was operated end-of-pipe at a commercial, outdoor rainbow trout (Oncorhynchus mykiss) farm in Denmark operated at low recirculation intensity. Applying an empty bed contact time (EBCT) of 5h, the specific objectives of the study were to resolve: i) how fast the bioreactor would start to remove NO3-N; ii) how fast steady state was achieved; iii) which NO3-N removal rates could be attained at the relatively low effluent temperature (∼8°C) and iv) to which extent any concomitant leaching of phosphorous (P), ammonia or organic matter would occur.In- and outlet grab samples were obtained every 6h until the bioreactor was in steady state (2 weeks) followed by weekly 24h pooled samples for another 3 weeks (5 weeks in total). Additional grab samples were obtained from 9 sampling ports within the bioreactor on 3 consecutive days during steady state. Samples were analyzed for dissolved nutrients (total N, nitrate, nitrite, ammonium, total phosphorous, ortho-phosphorous, BOD5 and COD). In addition, oxygen, temperature and pH were logged every 30min while sampling and alkalinity were measured once a week.Removal of NO3-N started immediately and remained stable at 7.06±0.81g NO3-N/m3/d (n=6) throughout the sampling period. Increased effluent NO2-N concentrations (peaking at 1.14mg NO2-N/l after 4–5 days) were transiently observed during the initial 11 days. After that, the woodchip bioreactor was largely in steady state with respect to N-balances corroborated by a close match between filtered total-N (TNdiss) and NO3-N removal rates. Measurements within the bed showed that the majority of the influent dissolved oxygen (DO) was consumed within the first part of the bioreactor and that NO3-N removal thereafter proceeded gradually with distance within the bed. Leaching of non-structural, dissolved organic compounds were observed just after startup, causing a short-term (1 week) increase in effluent concentrations of COD, BOD5, P and ammonium.Additional measurements carried out until 147 days after start-up showed that the woodchip bioreactor continued to remove TNdiss at an average removal rate of 7.81±0.82gN/m3/d, and that the initial leakage of P stopped altogether.In summary, the study demonstrated that woodchip bioreactors can effectively remove NO3-N from dilute aquacultural effluents at low temperatures and commercial conditions and that stable performance is achieved within a few weeks.

Performance of constructed wetland applied for domestic wastewater treatment: Case study at Boimorto (Galicia, Spain)

The study aims at evaluating the performance of a horizontal subsurface flow constructed wetland used for secondary treatment of domestic wastewater since May 2011 at Galicia (Spain). A septic tank was used as primary treatment. The wetland consists of two cells in parallel: cell-A with 350m2 and cell-B with 280m2, constructed with a depth of 0.6m, filled with gravel of 30mm of average size and planted with common reeds. The performance of wastewater treatment was controlled from June 2011 to September 2015. The rural agglomeration is served by a gravity sewer system with high rates of infiltration/inflow during wet weather. Thus, concentration and flow rate of wastewater have high seasonal variability. Average primary effluent BOD5, COD, suspended solids (TSS), total nitrogen (TN) and total phosphorous (TP) concentrations (in mg/L) were: 105, 197, 43, 29 and 3.4, respectively. Meanwhile, average secondary effluent BOD5, COD, SS, TN and TP values (in mg/L) were: 19, 44, 12, 14.3 and 1.9, respectively. A 2.2 log unit reduction for faecal coliforms was observed in the global system. The wetland required to be harvested at the end of each October. The sludge produced by the septic tank has not yet required to be removed. The wetland system presented no problems for vectors or nuisance odours.

Novel insights on the response of horizontal flow constructed wetlands to sudden changes of influent organic load: A modeling study

Horizontal flow constructed wetlands (HF CWs) have shown a good efficiency in the treatment of highly variable influent loads (e.g. touristic facilities, stormwater). However, recent studies have highlighted the possibilities of HF CW failure in treatment of high sudden loads. In order to limit excessive overestimation of the required surface area to face sudden loads, a more indepth understanding of HF response to time-variable loads is needed. With this objective in mind, the response of HF CWs to time-variable loads is investigated using a modeling approach. A validated process-based numerical model of a laboratory HF CW (1.1m×0.76m×0.3m) is used to study the response to both hourly and daily sudden loads, according to the specifications for the daily load pattern given in the European Standards for testing small wastewater treatment plants. During nominal load, the system was loaded with 10l of artificial wastewater per day with 954mgCOD/l and 21mgNH4−N/l. In addition to nominal load phase, high and low load phases with periods of 2 weeks with 50% higher and lower organic loads were simulated, respectively. The HF CW showed a good capacity to cope with the hourly variations, as concentrations at the outlet were constant (effluent concentrations of 319mg COD/l and 108mg NH4-N/l, respectively). During the high load phase, the COD effluent concentration was increased by 16% whereas the NH4-N effluent concentrations were decreased by 5%, respectively. During the low load phase, the COD effluent concentrations was decreased by 16% and the NH4-N effluent concentrations increased by 3%, respectively. After the end of the high and low load events, the system was able to recover original removal performances. The results of this work provide novel insights into the internal processes of a HF CW facing time-variable loads, as well as providing interesting insights for future designers.

Effect of temperature downshifts on a bench-scale hybrid A/O system: Process performance and microbial community dynamics

Effect of temperature downshifts on process performance and bacterial community dynamics was investigated in a bench-scale hybrid A/O system treating real domestic wastewater. Results showed that the average COD removal in this system reached 90.5%, 89.1% and 90.3% for Run 1 (25 °C), Run 2 (15 °C) and Run 3 (10 °C), respectively, and variations in temperature barely affected the effluent COD concentration. The average removal efficiencies of NH4+-N were 98.4%, 97.8%, 95.7%, and that of TN were 77.1%, 61.8%, 72% at 25 °C, 15 °C and 10 °C, respectively. Although the hybrid system was subjected to low temperature, this process effectively removed NH4+-N and TN even at 10 °C with the average effluent concentrations of 2.4 mg/L and 14.3 mg/L, respectively. Results from high-throughput sequencing analysis revealed that when the operation temperature decreased from 25 °C to 10 °C, the richness and diversity indexes of the system decreased in the sludge samples, while underwent an increase in the biofilm samples. Furthermore, the major heterotrophic bacteria consisted of Lewinella, Lutimonas, Chitinophaga and Fluviicola at 10 °C, which could be central to effective COD removal at low temperature. Additionally, Azospira, one denitrifying-related genus increased from 0.4% to 4.45% in the biofilm samples, with a stable TN removal in response to temperature downshifts. Nitrosomonas and Nitrospira increased significantly in the biofilm samples, implying that the attached biofilm contributed to more nitrification at low temperature.

Energy Recovery and Treatment of Winery Wastes by a Compact Anaerobic Digester

The objective of this study was to examine the process of aqueous extraction of organics and phenolics from winery wastes (grape marc and wine lees) and the anaerobic digestion of the extracts using a pilot-scale anaerobic digester. Samples of grape marc and wine lees were extracted with tap water under controlled laboratory conditions at different solid/liquid ratios 1:3, 1:5 and 1:10 (w/w). The extracts were characterized in terms of organic matter composition, and phenolic content. Following this, a 3 m3 stirred tank digester, inoculated with anaerobic granular sludge, was installed and operated at the premises of a winery using original grape marc and wine lees extracts. The recovered extracts were characterized by a high chemical oxygen demand (COD = 20–30 kg m3) and low concentration of phenolics (<100 mg L−1). They displayed high anaerobic degradability with a biogas yield of 0.50 m3 kg−1 COD, a methane content of 72 % and an effluent COD concentration between 0.6 and 1.6 g L−1. Based on a preliminary design and cost analysis it was demonstrated that for a medium sized winery (1000 tn grapes per season) a 40 m3 compact anaerobic digester suffices, while the payback period is around 6–7 years. Aqueous extraction of organics from winery wastes enables the recovery of readily degradable COD with low phenolic content. Generation of biogas from the recovered extracts was highly efficient using a compact anaerobic digester.

Combined biological and photocatalytic treatment of real coke oven wastewater

Wastewater generated from coke oven industries contains highly toxic organic and inorganic compounds. In the present study, biological reactors were integrated in sequence of anaerobic–aerobic–anoxic and tested with real coke oven wastewater obtained from a Steel Plant located in India. Among several pretreatment methods, coagulation of raw CWW was found to be effective. COD removal efficiency of 78.5% was achieved by the integrated bioreactor system after coagulation of CWW with 1000mg/L of alum. The effluent COD, NH4-N and TCN concentration from the integrated bioreactors was 420, 152 and 20mg/L, respectively. It was observed that 420mg/L of COD present in the effluent after integrated bio treatment was degraded in less than 4h to minimum COD concentration of 94mg/L using UV–TiO2 photocatalysis. In absence of photocatalyst (TiO2), there was no COD reduction from the bio treated effluent. Similarly, there was insignificant reduction in COD from the raw CWW using photocatalysis without biological treatment. Considerable COD reduction (78.5%) was observed only in the wastewater subjected to integrated biological system. The overall COD removal efficiency of the combined treatment system was found to be 96.2%, which resulted in an effluent COD concentration less than 94mg/L.

Treatment of pharmaceutical wastewater using interior micro-electrolysis/Fenton oxidation-coagulation and biological degradation

The synthesis of steroid hormones produces wastewater that is difficult to manage and characterize due to its complex components and high levels of toxicity and bio-refractory compounds. In this work, interior micro-electrolysis (IME) and Fenton oxidation–coagulation (FOC) were investigated as wastewater pretreatment processes in combination with biological treatments using a hydrolysis acidification unit (HA) and two-stage biological contact oxidation (BCO) in laboratory and field experiments. In laboratory experiments with an average initial COD load of about 15,000 mg/L, pH of 4, Fe–C/water (V/V) ratio of 1:1, air/water ratio of 10, and reaction time of 180 min, IME achieved a COD removal efficiency of 31.8% and a 1.7-fold increase in the BOD5/COD (B/C) ratio of wastewater. The Fe2+ concentration of 458.5 mg/L in the IME effluent meets the requirements of the Fenton oxidation (FO) process. FOC further reduced the COD with an efficiency of 30.1%, and the B/C ratio of the wastewater reached 0.59. Excitation-emission matrix (EEM) analysis showed that complex higher molecular weight organic compounds in the wastewater were degraded after the pretreatment process. In addition, a field experiment with a continuous flow of 96 m3/d was conducted for over 90 d. The combined process system operated steadily, though the Fe–C fillings should be soaked in a sulfuric acid solution (5‰) for 12 h to recover activity every two weeks. The COD and BOD5 concentrations in the final effluent were less than 90 mg/L and 15 mg/L, respectively.

A Comparison of Performance of ADM1 and Monod Model Treating Low Strength Wastewater

In the present paper, for performance evaluation two model namely anaerobic digestion model 1 and Monod model was used treating low strength wastewater. Effluent COD concentration was consider as a main predicting factor for performance evaluation. Kinetic constants are obtained by using the equations of completely stirred tank reactor. By comparing the kinetic constant obtained by both two models, kinetic constants are obtained by Monod model is more similar to CSTR model kinetic constants. Maximum percentage error in experimental and predicted effluent COD concentration in Monod model is 25% but in ADM1 model become 30%. From statistical analysis, it is concluded that Monod model is better for performance evaluation in UASB reactor treating low strength wastewater.

Evaluation of High Density Algal Cultivation for Secondary Wastewater Polishing.

This study evaluated the performance of an algal membrane bioreactor (A-MBR) for secondary wastewater effluent polishing and determined the membrane fouling behavior and dominance of algae in the A-MBR. The continuous flow A-MBR (effective volume = 7.2 L) was operated with low biomass wastage for more than 180 days, resulting in an average algal mixed liquor suspended solid concentration of 4922 mg/L. At the influent concentrations of 43 mg/L COD, 1.6 mg/L total phosphorus (TP), and 11.8 mg/L total nitrogen (TN), the effluent COD, TP and TN concentrations were 26 ± 6 mg/L, 0.7 ± 0.3 mg/L, and 9.6 ± 1.2 mg/L, respectively. High-density algae cultivation facilitated P adsorption and chemical precipitation. However, the TN removal efficiency was only 14% because of low biomass wastage. Although bacteria represented less than 2% of the total biomass in the A-MBR, bacterial growth in the secondary wastewater effluent accelerated membrane fouling.

Effect of Earthworm Eisenia Foetida in Constructed Wetland on Purification of Country Wastewater

Based on the ecology theory,this study wants to improve the wetland ecological system for ideas, introduced the Eisenia foetida to add the food chain's link, strengthen the link of aquatic animals, educed the conclusion:The Eisenia foetida can improve the condition of dissolved oxygen in the wetland. When hydraulic load is 0.3m3/(m2·d),the average effluent concentration of COD, TN and TP are 41.02mg/L,4.59mg/L,12.58mg/L and 0.44mg/L respectively,the effluent water quality satisfy the | A level of ▪ discharge standard of pollutants for municipal wastewater treatment plant ▪ (GB18918-2002).

SUBSTRATE REDUCTION KINETICS AND PERFORMANCE EVALUATION OF FLUIDIZED-BED REACTOR FOR TREATMENT OF BREWERY WASTEWATER

pilot scale anaerobic fluidized-bed reactor was operated for treating brewery wastewater at nine different hydraulic retention time (HRTs) of 2, 3, 4, 5, 6, 7, 8, 9, and 10hr. The COD reduction efficiencies increased from 9.8% to 74.1% with increasing HRT from 2 to 10hr.Similarly, the corresponding BOD 5 reduction efficiencies increased from 38.0% to 92.9% with the same increase in HRT. The predicted effluent substrate concentration values of Modified Stover–Kincannon model were found to be in strong agreement with the experimental values. This is due to proper solubilization and consumption of entrapped substrates in the fluidized-bed reactor since the microbial cells have maximum opportunity to interact with the entrapped substrates in the reactor. The kinetic parameters were determined using existing linear models with experimental data. Modified Stover-Kincannon model showed high correlation coefficient (R 2 = 0.9996) only in predicted effluent concentration of wastewater. This shows that this model can be best used to predict effluent COD concentration in a fluidized bed reactor treating brewery wastewater. Similarly, FIRST ORDER MODEL has the highest correlation coefficient in the plot using experimental data. This means that first order model can be used to represent the real biological degradation that takes place during the treatment of waste water by microorganisms in a fluidized-bed reactor system treating brewery wastewater. This model and kinetic parameters obtained in this work can be employed in the design of industrial size- fluidized bed reactor for treatment of brewery waste water. Maximum utilization rate constant (U max ) determined is 11.75g COD/l.hr and the saturation value constant (K B ) 131.41g COD/l.hr was also determined. The values of kinetic constants were also used to predict the effluent COD concentration. It was observed that the simulated data (predicted data) were in good harmony with the experimental data counterpart in modified Stover –Kicannon model, The strength of the above-mentioned model can be observed from the correlation coefficient obtained from the model asR 2 =0.9996 in modified Stover-kicannon model. http://dx.doi.org/10.4314/njt.v35i1.15

An Integrated Attached Growth Bioreactor for the Treatment of Wastewater

An integrated attached growth bioreactor was evaluated in this study for the removal of organic matter (COD). The bioreactor integrated the aerobic tank, anoxic tank and the secondary clarifier in a single unit. An attached growth media was submerged into the aerobic tank to improve the growth of biomass while bio-balls were submerged into the anoxic tank. Synthetic wastewater simulating medium and high strength domestic wastewater were pumped into the reactor for biodegradation. Hydraulic Retention Time (HRT) was varied in the range 12 and 7.2 days. Influent COD was introduced in two phases. Phase 1 consists of COD 400 mg/L whereas phase 2 consists of COD 650 mg/L. In phase 1, steady state was attained from day 18 until day 26. Effluent concentrations of COD were approximately 9 mg/L at HRT of 12 days. The effluent COD concentration increased (16 mg/L) when COD concentration was increased to 650 mg/L at HRT of 12 days. Effluent COD decreased from 19-9 mg/L when HRT was increased from 7.2-12 days. The effluent COD obtained in this study was below the Malaysia Department of Environment (DOE) guideline limit Standard A (120 mg/L). Residual ammonia, nitrate and total suspended solids were also monitored at steady state. Results show a 97, 87 and 97%, respectively removals for ammonia, nitrate and TSS, respectively. The attached growth media in the aerobic and anoxic tanks provided a large surface area for the attachment of biomass. The bioreactor performance shows it can serve as an alternative footprint for the treatment of wastewater.

Brewery wastewater treatment using an anaerobic membrane bioreactor

Anaerobic digestion technology plays an important role in the treatment of high strength wastewater. This study investigated the treatment of brewery wastewater using an advanced anaerobic membrane reactor (AnMBR). The results suggest that the AnMBR can achieve a COD removal higher than 98% when treating brewery wastewater, with a biogas yield of 0.53±0.015m3 biogas/kgCOD at 35°C. It was found that the 0.04-μm UF membrane played an important role in reducing COD concentrations in the AnMBR effluent. The observed specific MLVSS growth rate and yield for the AnMBR system tested were determined as 0.022±0.001 gVSS/gVSS/d and 0.029±0.001 gVSS/gCOD, respectively. The critical flux for the membrane filtration with the AnMBR system tested was in the range of 8.64±0.69L/m2/h, and the results showed that chemical recovery cleaning is necessary to maintain a stable, long-termoperation at a filtration flux of 8L/m2/h when treating brewery wastewater. The size fraction analysis of the EPS showed that particulate proteins and polysaccharides were the dominant forms of EPS in the AnMBR, which could exert a critical influence on the filtration behavior of the membrane process under the sub-critical flux condition in AnMBRs.

Culture of denitrifying phosphorus removal granules with different influent wastewater

Fed with three different kinds of influent, i.e. sodium acetate-based synthetic wastewater, synthetic wastewater with 10-mg L−1 Ca2+ ions, and raw domestic wastewater, respectively, compact of different influent wastewater on aerobic granulation was investigated in three sequencing batch reactors (corresponding to R1–R3) operating in an alternating anaerobic/oxic/anoxic mode. As a result, denitrifying phosphorus removal granules with an average diameter above 600 μm were successfully cultivated within 42 d when inoculated with flocculent sludge. The granules showed some characteristics, e.g. low in moisture content, high in specific gravity, and specific oxygen uptake rate. Reactors’ performance throughout operation presented that effluent concentration of COD was always lower than 40-mg L−1; TN, NH4+-N, and TP was often lower than 1-mg L−1. In addition, cycle test displayed that efficiencies of COD, NH4+-N, TN, and TP removal in R1–R3 reached up to 90.25, 92.98, 92.96%; 99.29, 99.57, 91.70; 90.83, 92.80, 89.56%; 94.06, 96.76, 90.71%, respectively, the maximal specific phosphorus release rate was 14.34, 8.32 and 2.32 mg P g MLVSS−1 h−1 in R1–R3, respectively, and the maximal specific phosphorus uptake rate was 14.13 mg P g MLVSS−1 h−1 in R1 and 2.34 mg P g MLVSS−1 h−1 in R2, respectively.