Volumetric Loading Rate Research Articles

Pre-treating amoxicillin contained wastewater with an anaerobic expanded granular sludge bed (EGSB)

The characteristic of anaerobic expanded granular sludge bed (EGSB) treating antibiotic wastewater that contained amoxicillin (AMX) was investigated. The performance of the reactor was characterized in terms of its COD, AMX removal efficiencies, and methane yield. After 241 d of operation, 85 and 80% removal efficiencies of COD and AMX were achieved, respectively. Furthermore, volumetric loading rate (VLR) effecting on EGSB system was evaluated by changing hydraulic retention time (HRT was switched to 14, 8, and 14 h, respectively). With HRT decreased to 8 h, COD and AMX removal efficiencies dropped obviously to 36.50 and 58.55%, respectively. When HRT was switched to 14 h again, AMX removal efficiency required three more days than COD to recover to around 80%. These results showed that EGSB reactor could resist the short-time shock of VLR and recover to high removal efficiencies of AMX and COD. According to AMX and COD removal efficiencies and methane yield, it was confirmed that AMX was unlikely to create problems in pre-treating AMX-contained wastewater with EGSB system.

Biogas Cleaning by Hydrogen Sulfide Scrubbing and Bio-oxidation of Captured Sulfides

Hydrogen sulfide and partially carbon dioxide can be absorbed into alkaline washing liquid with nitrates for upgrading a quality of biogas. Sulfides captured into the washing liquid are consequently biologically oxidized in an anoxic bioreactor by autotrophic denitrifying bacteria. Nitrates in the washing liquid serve as electron acceptors for sulfide bio-oxidation. Washing of hydrogen sulfide from biogas was examined in a lab-scale countercurrent scrubber that was packed with plastic carriers and operated at different biogas and washing liquid flows. The hydrogen sulfide concentration in treated biogas was investigated in the range from 3 to 12.3 g m–3. The influence of the hydrogen sulfide volumetric loading rate on required scrubber wetting Sw was determined. The anoxic bioreactor packed with the same plastic carriers for immobilization of bacteria was operated long term at the sulfide loading rate in the range from 21 g m–3 day–1 during the start-up period to 400 g m–3 day–1 at the end of the operatio...

Long-term operation of a pilot scale anaerobic membrane bioreactor (AnMBR) for the treatment of municipal wastewater under psychrophilic conditions

The performance of a pilot scale anaerobic membrane bioreactor (AnMBR), comprising an upflow anaerobic sludge blanket (UASB) reactor coupled to an external ultrafiltration membrane treating municipal wastewater at 18±2°C, was evaluated over three years of stable operation. The reactor was inoculated with a mesophilic inoculum without acclimation. The AnMBR supported a tCOD removal efficiency of 87±1% at hydraulic retention time (HRT) of 7h, operating at a volumetric loading rate (VLR) of between 2 and 2.5kgtCOD/m3d, reaching effluent tCOD concentrations of 100–120mg/L and BOD5 concentrations of 35–50mgO2/L. Specific methane yield varied from 0.18 to 0.23Nm3CH4/kgCODremoved depending on the recirculation between the membrane module and the UASB reactor. The permeate flow rate, using cycles of 15s backwash, 7.5min filtration, and continuous biogas sparging (40–60m/h), ranged from 10 to 14Lm2/h with trans-membrane pressure (TMP) values of 400–550mbar.

Advanced removal of organic and nitrogen from ammonium-rich landfill leachate using an anaerobic-aerobic system

A novel system coupling an up-flow anaerobic sludge blanket (UASB) and sequencing batch reactor (SBR) was introduced to achieve advanced removal of organic and nitrogen from ammonium-rich landfill leachate. UASB could remove 88.1% of the influent COD at a volumetric loading rate of 6.8kgCOD·m−3·d−1. Nitritation–denitritation was responsible for removing 99.8% of NH4+-N and 25% of total nitrogen in the SBR under alternating aerobic/anoxic modes. Simultaneous denitritation and methanogenesis in the UASB enhanced COD and TN removal, and replenished alkalinity consumed in nitritation. For the activated sludge of SBR, ammonia oxidizing bacteria were preponderant in nitrifying population, indicated by fluorescence in situ hybridization (FISH) analysis. The Monod equation is appropriate to describe the kinetic behavior of heterotrophic denitrifying bacteria, with its kinetic parameters determined from batch experiments.

Mitigating off-gas emissions in the biological nitrogen removal via nitrite process treating anaerobic effluents

A sequencing batch reactor treating the reject water produced from the dewatering of the anaerobic co-digestate of waste activated sludge and the organic fraction of municipal solid waste was monitored in order to assess the off-gas emissions that were produced. The gaseous emissions of nitrous oxide (N2O), carbon dioxide (CO2), methane (CH4), ammonia (NH3) and methyl mercaptan (CH3SH) produced during the biological nitrogen removal via nitrite route were monitored. During experimental period 1 a volumetric nitrogen loading rate (vNLR) of 1.08 kg N/m3 d was applied, while in period 2 the vNLR was 0.81 kg N/m3 d. Nitrous oxide emissions decreased from 1.49% of the influent nitrogen load in period 1 to 0.24% in period 2. The higher dissolved oxygen (DO) concentration and the lower accumulation of nitrite in the reactor resulted in significantly lower nitrous oxide emissions in period 2. Some methane (5.8% of influent COD load) was emitted during period 1, as the lower DO concentration created micro-anaerobic conditions within the sludge flocs.

Development of Anaerobic High-Rate Reactors, Focusing on Sludge Bed Technology.

In the last 40 years, anaerobic sludge bed reactor technology has evolved from localized laboratory-scale trials to worldwide successful implementations in a variety of industries. High-rate sludge bed reactors are characterized by a very small footprint and high applicable volumetric loading rates. Best performances are obtained when the sludge bed consists of highly active and well settleable granular sludge. Sludge granulation provides a rich microbial diversity, high biomass concentration, high solids retention time, good settling characteristics, reduction in both operation costs and reactor volume, and high tolerance to inhibitors and temperature changes. However, sludge granulation cannot be guaranteed on every type of industrial wastewater. Especially in the last two decades, various types of high-rate anaerobic reactor configurations have been developed that are less dependent on the presence of granular sludge, and many of them are currently successfully used for the treatment of various kinds of industrial wastewaters worldwide. This study discusses the evolution of anaerobic sludge bed technology for the treatment of industrial wastewaters in the last four decades, focusing on granular sludge bed systems.

Treatment of Wastewater from Purified Terephtalic Acid (PTA) Production in a Two-stage Anaerobic Expanded Granular Sludge Bed System

ABSTRACT The wastewater treatment with a two-phase expanded granular sludge bed (EGSB) system for anaerobic degradation of acetate, benzoate, terephtalate and p -toluate from purified terephtalic acid (PTA) production was studied. The feasibility and effectiveness of the system was evaluated in terms of organic oxidation by chemical oxygen demand (COD), gas production, bacterial adaptability and stability in the granular sludge. Average removal efficiencies 93.5% and 72.7% were achieved in the EGSB reactors under volumetric loading rates of 1.0–15 kg-COD/m 3 /day and terephtalate and p -toluate of 351–526 mg/L, respectively. Gas production reached total methane production rate of 0.30 L/g-COD under these conditions in the sequential EGSB reactor system. Higher strength influent COD concentration above 4.8 g-COD/L related to field conditions was fed to observe the disturbance of the EGSB reactors. Keywords: Anaerobic treatment, Expanded granular sludge bed (EGSB), Purified terephtalic acid (PTA), Two-phase, Wastewater

Performance and microbial community analysis of a pilot-scale UASB for corn-ethanol wastewater treatment.

The performance and microbial community structure of a pilot-scale upflow anaerobic sludge blanket (UASB) reactor inoculated with flocculent sludge were investigated over 52days. The characteristics of corn-ethanol wastewater were as follows: CODCr, 1,050-4,970mgl(-1); ammonia, 14-298mgl(-1); and alkalinity, 332-2,867mgl(-1). The UASB could start up smoothly with a hydraulic loading rate lower than 180lh(-1) and a ratio of volatile fatty acid versus alkalinity between 0.04 and 0.48. The maximum gas production rate was 432lh(-1) and the highest volumetric loading rate of 7.2kgm(-3)day(-1) was obtained after 48days. The 1mm granules could form a complex network and were composed of many Methanosaeta. Aceticlastic methanogens served as a dominant methanogenic group, which accounted for the relatively high resistance to shock loading.

Performance of nitrate-dependent anaerobic ferrous oxidizing (NAFO) process: A novel prospective technology for autotrophic denitrification

Nitrate-dependent anaerobic ferrous oxidizing (NAFO) is a valuable biological process, which utilizes ferrous iron to convert nitrate into nitrogen gas, removing nitrogen from wastewater. In this work, the performance of NAFO process was investigated as a nitrate removal technology. The results showed that NAFO system was feasible for autotrophic denitrification. The volumetric loading rate (VLR) and volumetric removal rate (VRR) under steady state were 0.159±0.01kg-N/(m3d) and 0.073±0.01kg-N/(m3d), respectively. In NAFO system, the effluent pH was suggested as an indicator which demonstrated a good correlation with nitrogen removal. The nitrate concentration was preferred to be less than 130mg-N/L. Organic matters had little influence on NAFO performance. Abundant iron compounds were revealed to accumulate in NAFO sludge with peak value of 51.73% (wt), and they could be recycled for phosphorus removal, with capacity of 16.57mg-P/g VS and removal rate of 94.77±2.97%, respectively.

Denitrification in biofilm configured horizontal flow woodchip bioreactor: effect of hydraulic retention time and biomass growth

Removal of nitrates and nitrogen (NO3−-N) from surface and groundwater was a matter of special importance, and there was a need for sustaining the public health problems and aquatic life related to the presence of NO3−-N in drinking water supplies. The influence of hydraulic retention time (HRT), volumetric loading rates (VLRs) and temperature on denitrification were investigated in a biofilm configured woodchip bioreactor (WBR) from synthetic tile water. Three HRTs were examined, ranging from 4 to 12h. The denitrification removal efficiency (RE) >99% was obtained in WBR operated at 8-h HRT. The WBR was operated with VLR ranging from 49 to 198g NO3−-N/L/day for denitrification study. The maximum load reduction of the WBR showed 99% in second level of reactor operation with biomass concentration of 12.3g/L. The pH (6.5–7.2) and temperature (17–20°C) under the unique study profoundly impact on denitrification. The coefficient factors of 0.8 and 1.05 have been reported in studies with a temperature change from 4 to 20°C. Scanning electron microscope (SEM) analysis documented formation of biofilm on woodchips in each level of reactor operation study. Therefore we recommend from this study, that the horizontal flow based WBR to enhance denitrification while minimizing higher operating conditions in denitrification beds.

Effect of microwave pre-treatment of thickened waste activated sludge on biogas production from co-digestion of organic fraction of municipal solid waste, thickened waste activated sludge and municipal sludge.

Anaerobic co-digestion of organic fraction of municipal solid waste, with thickened waste activated sludge and primary sludge has the potential to enhance biodegradation of solid waste, increase longevity of existing landfills and lead to more sustainable development by improving waste to energy production. This study reports on mesophilic batch and continuous studies using different concentrations and combinations (ratios) of organic fraction of municipal solid waste, thickened waste activated sludge (microwave pre-treated and untreated) and primary sludge to assess the potential for improved biodegradability and specific biogas production. Improvements in specific biogas production for batch assays, with concomitant improvements in total chemical oxygen demand and volatile solid removal, were obtained with organic fraction of municipal solid waste:thickened waste activated sludge:primary sludge mixtures at a ratio of 50:25:25 (with and without thickened waste activated sludge microwave pre-treatment). This combination was used for continuous digester studies. At 15 d hydraulic retention times, the co-digestion of organic fraction of municipal solid waste:organic fraction of municipal solid waste:primary sludge and organic fraction of municipal solid waste:thickened waste activated sludge microwave:primary sludge resulted in a 1.38- and 1.46-fold increase in biogas production and concomitant waste stabilisation when compared with thickened waste activated sludge:primary sludge (50:50) and thickened waste activated sludge microwave:primary sludge (50:50) digestion at the same hydraulic retention times and volumetric volatile solid loading rate, respectively. The digestion of organic fraction of municipal solid waste with primary sludge and thickened waste activated sludge provides beneficial effects that could be implemented at municipal wastewater treatment plants that are operating at loading rates of less than design capacity.

Coupling the treatment of low strength anaerobic effluent with fermented biowaste for nutrient removal via nitrite

Nutrient removal via nitrite was investigated in a sequencing batch reactor (SBR) treating low strength effluent produced from an upflow anaerobic sludge blanket (UASB). Domestic organic waste (DOW) and vegetable and fruit waste (VFW) were fermented and applied as external carbon source to the SBR. Nutrient removal via nitrite was much higher when DOW fermentation liquid (FL) was applied rather than VFW FL and acetic acid. The DOW FL contained propionic acid and butyric acid in significant proportions, favouring the nutrient removal via nitrite, while the VFW FL contained mainly acetic acid, which was associated with lower nutrient via nitrite activity. The application of high volumetric nitrogen loading rate (vNLR = 0.19–0.21 kgN m−3 d−1) in combination with low dissolved oxygen (DO) concentration during the aerobic phase, resulted in high and stable nitrite accumulation (NO2–N/NOx–N >97%). These conditions favoured the phosphorus uptake via nitrite, which reached high rates (5.95 ± 2.21 mgP (gVSS h)−1), while the aerobic phosphorus removal was much lower. Through mass balances, it was demonstrated that the application of the UASB-SBR process with nutrient removal via nitrite at a decentralized level is a sustainable solution for effective co-treatment of domestic sewage and biowaste.

RO 농축폐액의 처리를 위한 이온교환수지의 생물재생

In order to remove both nitrate and sulfate present in the concentrate of RO(reverse osmosis) process, a combined bio-regeneration and ion-exchange(IX) system was studied. For this purpose, both denitrifying bacteria(DNB) and sulfate reducing bacteria(SRB) were simultaneously cultivated in a bio-reactor under anaerobic conditions. When the IX column containing a nitrate-selective A520E resin was fully exhausted by nitrate and sulfate, the IX column was bio-regenerated by pumping the supernatant of the bio-reactor, which contains MLSS concentration of <TEX>$125{\pm}25mg/L$</TEX>, at the flowrate of 360 BV/hr. Even though the nitrate-selective A520E resin was used, the breakthrough curves of ionic species showed that sulfate was exhausted earlier than nitrate. The reason for this result is due to the fact that the concentration of sulfate in RO concentrate was 36 to 48 times higher than nitrate. The bio-reactor was successfully operated at a volumetric loading rate of 0.6 g <TEX>$COD/l{\cdot}d$</TEX>, nitrate-N loading rate of 0.13 g <TEX>$NO_3{^-}-N/l{\cdot}d$</TEX>, and sulfate loading rate of 0.08 g <TEX>$SO_4{^{2-}}/l{\cdot}d$</TEX>. The removal rate of SCOD, nitrate-N, sulfate was 90, 100, and 85%, respectively. When the virgin resin was fully exhausted and consecutively bio-regenerated for 2 days, 81% of nitrate and 93% of sulfate were reduced. When the virgin resin was repeatedly used up to 4 cycles of service and bio-regeneration, the ion-exchange capacity of bio-regenerated resin decreased to 95, 91, 88, and 81% of virgin resin.

Start-up and bacterial communities of single-stage nitrogen removal using anammox and partial nitritation (SNAP) for treatment of high strength ammonia wastewater

In this study, a lab-scale sequencing batch biofilm reactor (SBBR) was used to start up the single-stage nitrogen removal system using anammox and partial nitritation (SNAP) process seeding from surplus activated sludge. The volumetric nitrogen loading rate (vNLR) was firstly 0.075kgNm−3d−1 and then gradually increased to 0.60kgNm−3d−1. A maximal total nitrogen (TN) removal rate of 0.54kgNm−3d−1 was achieved by the SNAP process after 132days operation with NH4+-N and TN removal efficiency of 99.4% and 90.5%, respectively. This reactor may have applications for the SNAP process treating high strength ammonia wastewater. And dewatered surplus activated sludge was recommended as the seed sludge for engineering applications. The dominant bacterial strains were Xanthomonas campestris, Nitrosomonas europaea and Ignavibacterium album, corresponding to the percentage of 24%, 22% and 20%, respectively, based on the 16S rDNA amplicon pyrosequencing of the SNAP sludge.

The use of bottle caps as submerged aerated filter medium

In this study, a submerged aerated filter (SAF) using bottle caps as a support medium was evaluated. The system was fed with effluent from an upflow anaerobic sludge blanket system at ETE 2-South wastewater treatment plant, under different volumetric organic load rates (VOLRs). The population of a particular nitrifying microbial community was assessed by fluorescent in situ hybridization with specific oligonucleotide probes. The system showed an average removal of chemical oxygen demand (COD) equal to 76% for VOLRs between 2.6 and 13.6 kg COD m(-3)_media.day(-1). The process of nitrification in conjunction with the removal of organic matter was observed from applying VOLRs lower than 5.5 kg COD m(-3)_media.day(-1) resulting in 78% conversion of NH4(+)-N. As the applied organic load was reduced, an increase in the nitrifying bacteria population was observed compared with total 4'-6-diamidino-2-phenylindole (DAPI) stained cells. Generally, SAF using bottle caps as a biological aerated filter medium treating wastewater from an anaerobic system showed promising removal of chemical oxygen demand (COD) and conversion of NH4(+)-N.

BIODEGRADATION OF THE HERBICIDE LINURON IN A PLUG-FLOW PACKED-BED BIOFILM CHANNEL EQUIPPED WITH TOP AERATION MODULES

A lab-scale packed-bed biofilm channel reactor that operates as a plug-flow system equipped with top aeration modules was constructed and evaluated. To assess the reactor performance a microbial community able to degrade linuron was used. Changing the fluid flow rates and the linuron concentrations in the inflowing medium the volumetric loading rates of linuron (BV,L) were gradually increased from 0.29 to 14.93 mg/Lh. During the operation of the reactor, an airflow rate of 0.15 ± 0.05 L/min was maintained in each aeration module. In these working conditions, dissolved oxygen concentrations (OD) of about 5 mg/L were obtained in the aeration modules. For all BV,L values tested, the microbial community colonized the support and removed the linuron with efficiencies of about 100%. The highest removal efficiency measuring the chemical oxygen demand (COD) was about 84%, and no accumulation of aromatic intermediates was detected by HPLC analysis. The results showed that the oxygen consumption rate was proportional to BV,L. The dissolved oxygen was not entirely consumed in the bioreactor indicating that, even at the highest loading rates, the microbial community was not limited by oxygen. The use of top aeration modules was successful, and their place in a packed bed biofilm channel allowed enough dissolved oxygen at the beginning of each stage, and along the whole reactor. It is appropriate to mention that no reports of linuron removal in bioreactors could be found in the literature.

Experiences with anaerobic treatment of fat-containing food waste liquids: two full scale studies with a novel anaerobic flotation reactor

Fat-containing food waste can be effectively treated in a new type of reactor, the so-called BIOPAQ-Anaerobic Flotation Reactor or BIOPAQ(®) anaerobic flotation reactor (AFR). In the reactor a flotation unit is integrated to retain the sludge. In this study results from two plants with a 430 and 511 m(3)-AFR, respectively, are presented. In one reactor, which is fed with water originating from different food liquid streams, over 99% of fat and oils were removed. Over 90% of the chemical oxygen demand (COD) was removed. When the last solids were removed from the effluent with a tilted plate settler, 98% COD removal was attained. The effluent concentrations of extractable hydrolysed and non-hydrolysed fats were less than 40 mg/l. Apparently the variations in the liquid streams deriving from the tank cleaning activities did not disturb the system. Only extremely high concentrations of fats could disturb the system, but the inhibition was reversible. In the reactor treating water from an ice-cream factory, which contained fats up to approximately 50% of influent COD, a COD removal efficiency of 90% was achieved. At volumetric loading rates varying from 1 to 8 kg COD/m(3)/d, biogas was produced at an average specific gas production of 0.69 m(3)/kg COD-removed.

The combined UASB and MBR system to COD and TSS removal and excess sludge reduction for the treatment of high strength wastewater in various operational temperatures

There are many activated sludge plants (ASP) in Iran. Most of them are overloaded and as a result their efficiency is very low. A combined laboratory-scale system (5 L reactors) consisting of an up-flow anaerobic sludge blanket (UASB) and aerobic membrane bioreactor (MBR) was operated at 20 and 30°C with pH between 7.6 and 8.4. The experiment was run to optimize treatment of high-strength enriched municipal wastewater of the Ekbatan treatment plant located in west Tehran. The chemical oxygen demand (COD) of the wastewater was enriched due to the addition of molasses and milk powder. To prevent pH fluctuation of the influent, NaHCO3 and K2HPO4 were added to the wastewater. The excess sludge from the MBR was recirculated into the UASB. The system treated fortified municipal wastewater with a volumetric COD loading rate of 600, 1,200, 1,800, and 2,400 mg/L, and temperatures at 20 and 30°C. The results of the present work indicate an optimum organic loading (7.2–10.8 kg m−3 d−1) with COD removal efficiency (RE) between 74 and 85% in both examined temperatures in UASBR. The total combined system efficiency was, approximately, 98% in COD removal and 100% in total suspended solids removal. Furthermore, the nitrate RE was about 80%. Also, excess sludge reduction was over 90%, and the optimum hydraulic retention time for influent COD concentration of 1,200 mg l−1 is shown to be 4 h. This upgraded system increases the treatment capacity by factor of 5.

A Bioelectrochemically‐Assisted Membrane Bioreactor for Simultaneous Wastewater Treatment and Energy Production

AbstractA bioelectrochemically‐assisted membrane bioreactor (BEAMBR), integrating a microbial fuel cell with a membrane bioreactor, was developed for energy recovery and efficient wastewater treatment. The stainless‐steel membrane module with biofilm, served not only as dynamic membrane separation device but also as biocathode. The effluent turbidity reached 0.8 NTU after stable operation, and particle with average size larger than 1.14 μm were effectively rejected from the mixed liquor by the dynamic membrane. The BEAMBR successfully removed the chemical oxygen demand and ammonium. With increasing hydraulic retention time and decreasing volumetric organic loading rate, the power production in this reactor was enhanced. The results showed that the BEAMBR is a promising process for efficient energy recovery and wastewater treatment.

Application of membrane bioreactor for completely autotrophic nitrogen removal over nitrite (CANON) process

A membrane bioreactor (MBR) was adopted for completely autotrophic nitrogen removal over nitrite (CANON) process at ambient temperature. CANON was rapidly started-up within around 50d under oxygen-limited condition. The average nitrogen removal rate reached to 0.70kgNm−3d−1 with a removal efficiency of 88%. The ratio of air flow rate to volumetric ammonium loading rate should be maintained below 0.28Lairmin−1kg−1Nm3d for stable CANON. The feasibility of MBR for CANON process was proved in batch experiments. FISH results showed that aerobic ammonium-oxidizing bacteria predominated in the reactor sludge, whereas anaerobic ammonium-oxidizing bacteria predominated in the membrane biofilm. This study demonstrated that MBR was a suitable experimental setup for the operation of CANON process.