Performance Of Moving Bed Biofilm Reactor Research Articles

Olive mill wastewater co-treatment: Effect of (electro)Fenton processes and dilution ratio on moving bed biofilm reactor performance

The treatment of olive mill wastewater (OMW) represents still an open challenge because of its highly polluting load. One of the most affordable methods for small-medium mills is to send OMW to industrial wastewater treatment plants (IWTP). Accordingly, this work explored a strategy consisting of the biological co-treatment of real OMW and simulated urban wastewater by a moving bed biofilm reactor (MBBR), with and without (electro)Fenton pre-treatment, to simulate OMW treatment through a multi-barrier approach in an IWTP. The effluent of the MBBR without pre-treatment, despite the long period of operation of 18 months, was in compliance with the limit for total phenols (TPHs) of 0.5 mg/L only at a really low OMW's dilution ratio (DR) (1/4000 (v/v)). The Fenton oxidation (FO) and the electro-assisted Fenton (EAF) processes were investigated as pre-treatment of diluted OMW. FO resulted in good performances in terms of TPHs removal (81%) and improved biodegradability (final BOD5/COD ratio = 0.35) but in poor COD removal (24%). EAF was more effective (COD removal = 41%, TPHs removal = 85%, and final BOD5/COD ratio = 0.40) than FO. Therefore, EAF was finally investigated on undiluted OMW (COD removal = 56%, TPHs removal = 84%, and final BOD5/COD ratio = 0.62) and subsequently co-treated with simulated urban wastewater by MBBR, identifying 1/1000 as the optimal DR. The investigated multi-barrier approach is an interesting option for OMW co-treatment in IWTPs to successfully address the challenge of TPHs degradation and drastically reduce the volume of the biological process unit (4 times lower than MBBR treatment alone).

Optimization of moving bed biofilm reactors for the treatment of municipal wastewater

The properties of biocarriers significantly influence the performance of a moving bed-biofilm reactor (MBBR). This study aimed to assess the impact of media type, filling ratio, and hydraulic retention time (HRT) on biofilm formation and MBBR performance in both batch and continuous setups using real municipal wastewater. Two different media, high-density polyethylene (HDPE) and polypropylene (PPE), with varying surface area and properties were used. Biofilm growth and MBBR performance were monitored and optimized using response surface methodology. The effect of different media was investigated for three filling ratios of 20%, 40% and 60% and HRT of 4, 6 and 8 h. Results depicted a better biofilm growth on HDPE media in comparison to PPE carriers due to difference in media structure and surface properties. At all the conditions tested, HDPE media showed comparatively better performance for the removal of organic matter and nutrients than PPE media. The maximum organic matter removal efficiency was found as 77% and 75% at an HRT of 6 h and filling ratio of 40% for HDPE and PPE media, respectively. The ammonia removal was also found better for HDPE media due to its geometry and structure favoring the anoxic conditions with maximum removal of 89% achieved at 6-h HRT and 40% filling ratio. Overall, the system with HDPE media indicated more stability in terms of reactor performance than PPE carriers with variations in the operating conditions.

A Coin-Shaped Polypropylene Bio-Carrier Fabricated Using a Filament-Based 3D Printer for Wastewater Treatment

The utilization of the moving bed biofilm reactor (MBBR) has been identified as a promising technology for reducing water pollutants. This study focuses on designing a novel bio-carrier using 3D printing technology for use in an MBBR for wastewater treatment. The bio-carrier is made of polypropylene filament with four variations in specific surface area. The study investigates the relationship between the specific surface area and the amount of adhering biofilm on the bio-carrier. Results show that type-4 bio-carrier with a specific surface area of 1438.16 m2/m3 and a pore diameter of 1.8 mm to 4.9 mm has the highest mass of biofilm attachment at 2.598 grams. This research provides insights for designing bio-carriers with suitable pore diameters and specific surface areas for improved MBBR performance in wastewater treatment.

Improvement of MBBR Performance by the Addition of 3D-Printed Biocarriers Fabricated with 13X and Bentonite

The current study investigated the performance of a moving bed biofilm reactor (MBBR), when adding 3D-printed biocarriers fabricated with 13X and bentonite (MBBR 3D), when using K1 commercial biocarriers (MBBR K1) and when not adding biocarriers at all (control MBBR). For the evaluation of the MBBR efficiency, various physicochemical parameters were measured, while biofilm extracted from the biocarriers was evaluated. The findings suggest that there is an optimal biodegradation of the organic load in all MBBR units. The nitrification and denitrification processes were improved in MBBR 3D as compared to the control MBBR and MBBR K1. The dry mass of the biofilm in the 3D-printed biocarriers was two orders of magnitude larger than in the K1 biocarriers. Moreover, in the K1 biocarriers the mass of the biofilm varied in relation to time, since it could not be protected inside the holes, something that did not happen with the 3D-printed biocarriers. Finally, it was found, mostly in MBBR 3D and less in MBBR K1, that the growth of nitrifying bacteria and heterotrophs inside the units increased the biomass production in the form of soluble microbial products, which in turn favored the adhesion of biomass on the surface of biocarriers.

Kinetic Study for Startup of Aerobic Moving Bed Biofilm Reactor in Treatment of Textile Dye Wastewater.

Due to high augmentation in population and low availability of land, the quantum of wastewater production has surged resulting in advancements in wastewater treatment systems. To cope under such stressful circumstances, moving bed biofilm reactor (MBBR) proves to be an upgraded treatment technology for industrial and municipal wastewater treatment. The present startup study has been carried out using a laboratory-scale aerobic MBBR with working volume of 25L for textile dye wastewater treatment having AnoxKaldnes K3 media at filling percentage of 50%. In order to acclimatize the microorganisms on textile dye wastewater, the startup of the reactor was carried out using lactose as readily degradable co-substrate with textile dye wastewater in different ratios at hydraulic retention time (HRT) of 24h. The biofilm on the media was developed in 63days duration and the reactor attained pseudo-steady state (PSS) in 185days period. During PSS condition of the MBBR, the maximum chemical oxygen demand (COD) removal efficiency of 92% with mixed liquor suspended solids (MLSS) concentration of 4224 ± 22mg/L has been achieved. The kinetic study for biodegradation of textile dye wastewater has also been carried out using the Monodgrowth kinetics. The values of bio-kinetic coefficients of yieldof heterotrophic biomass (Y) and endogenousdecay coefficient for heterotrophic biomass (Kd) recorded are 0.394 mgVSS/mgCOD.d and 0.087day-1, respectively. The values of specific substrate removal rate (k), Monodhalf saturation constant (Ks), and maximumspecific growth rate for heterotrophic biomass (µmax) are 0.024 mgCOD/mgVSS.d, 53.203mg/L, and 0.0095day-1, respectively, demonstrating the suitability and healthy performance of MBBR for textile dye wastewater treatment.

PENGOLAHAN LIMBAH DOMESTIK RUMAH MAKAN DENGAN MOVING BED BIOFILM REACTOR (MBBR)

Saat ini usaha rumah makan jumlahnya semakin meningkat. Air buangan yang diakibatkan oleh aktivitas rumah makan tersebut akan menjadi suatu permasalahan bagi lingkungan. Pengolahan air buangan rumah makan bisa dilakukan dengan cara pengolahan biologis karena dapat menurunkan kandungan organik pada air limbah. Proses pengolahan biologis yang dapat digunakan yaitu dengan sistem Moving Bed Biofilm Reactor (MBBR). Proses MBBR pada prinsipnya adalah pertumbuhan biologis dengan menggunakan biakan tersuspensi dan melekat yang tercampur didalam suatu reaktor dengan aerasi dan media yang bergerak. Penelitian ini bertujuan untuk mengetahui kinerja MBBR dalam menurunkan TOC dan TSS pada air buangan rumah makan. Media yang digunakan adalah Kaldness K3 dan Bioball dengan variasi komposisi media yaitu 100% Kaldness K3, 100% Bioball, 50% Kaldness K3 dan 50% Bioball, 60% Kaldness K3 dan 40% Biobll, 40% Kaldness K3 dan 60% Bioball. Variasi kedua adalah waktu sampling yaitu 3 jam, 6 jam, 9 jam, 12 jam, dan 15 jam. Berdasarkan hasil penelitian ini menunjukkan bahwa kemampuan reaktor MBBR paling optimum adalah dengan komposisi 100% Kaldness K3 pada waktu sampling 15 jam. Reaktor tersebut dapat menurunkan TOC sebesar 97,84% dan untuk penurunan TSS sebesar 76,84%

Comparative analysis of the effect of cell immobilization on the hydrogenothrophic biomethanation of CO2

AbstractCarbon capture and utilization (CCU) has been offered as a potential technological solution for mitigating the greenhouse gas emissions and climate change concern worldwide. Anaerobically carbon utilization has started to be in the agenda of researchers in recent years since this approach offers significant advantages such as use of catalysis reactions through environmentally friendly microorganisms under low temperature and pressure operational conditions. Moreover, a cleaner and more effective bioenergy production is realized in the form of biomethane.This study aimed to exploit the merits of cell immobilization in order to provide a stable hydrogenotrophic biomethanation process. For this purpose, two different immobilized bioreactors packed with plastic moving bed biofilm reactor (MBBR) and glass beads packing materials were comparatively investigated. To the best of our knowledge, these two immobilization materials were used for the first time for this purpose. Two different bioreactor configurations were compared for the performance parameters such as methane formation rate, H2 consumption and methane contents in the headspace. Methane content in the headspace of these bioreactors were measured to be 80 and 75% for MBBR bioreactor and glass bead bioreactors, respectively. In addition, methane formation rates (MFR) of 5.14 and 4.8 m3/m3/day were achieved in MBBR and glass beads bioreactors, respectively. Even though both bioreactor configurations performed highly efficient biomethanation of CO2, the statistical evaluation of the results indicated that MBBR performance was more favourable for hydrogenotrophic biomethanation. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

Numerical study of hydrodynamic characteristics in a moving bed biofilm reactor

The moving bed biofilm reactor (MBBR) has certain advantages, such as high wastewater treatment efficiency, low maintenance and operating costs, and simple operation. It has emerged as a valuable option for small decentralized facilities. The filling ratio, aeration mode and aeration intensity are the main factors that affect the performance of MBBRs in wastewater treatment. However, the information that concerns the used criteria that pertain to the process design for the MBBR is not adequate. In this study, a three dimensional computational fluid dynamics (CFD) model was constructed and the maximum error was only 1.98%, which was much smaller than the traditional 2D-CFD model. The filling ratio, aeration mode and aeration intensity of MBBR were optimized by CFD model from the point of view of fluid mechanics. The results show that the fluidization performance of the filling is the best under the one-side aeration mode with 30% filling ratio. The cost-performance ratio of the reactor with 30% filling ratio was 1.53, 25% and 35% filling ratio were only 1.17 and 1.14 respectively. Increasing the aeration intensity could improve the fluidization performance. However, the effect of high aeration intensity on the fluidization performance of the carrier was limited and the energy consumption increased greatly. The results revealed that when the aeration intensity increased from 0.07 min−1 to 0.13 min−1, the proportion of the carrier area increased by 16.56%. The proportion of the carrier area with an aeration rate of 0.20 min−1 was only 4.23%, which is higher than 0.13 min−1. The main factors that control the fluidization of the carrier were the range of the flow zone and the flow velocity of the liquid. Increasing the range of the flow zone could facilitate the flow of the carriers. The critical value of the flow velocity of the liquid in the flow zone was 0.04 m/s. These results could guide the optimization design of the filling ratio and the aeration conditions and provide a theoretical basis for the application of MBBR.

High loaded moving bed biofilm reactors treating pulp & paper industry wastewater: Effect of hydraulic retention time, filling degree and nutrients availability on performance, biomass fractions and nutrients utilization

For treating pulp and paper (P&P) industry wastewaters, the high-loaded/nutrient-limited moving bed biofilm reactor (MBBR) is frequently followed by an activated sludge, in the Biofilm-Activated Sludge (BAS) configuration. Evidences show that the MBBR performance relies on a complex surface-volume relation, affecting the biosolids dynamics. That subject was addressed in parallel lab-scale MBBRs, with carrier filling degrees of 15% and 45%, fed with P&P wastewater. The removal of chemical oxygen demand (COD) and utilization of nutrients were evaluated for varying hydraulic retention times (HRT, 1.6–4.9 h), and availabilities of nitrogen and phosphorous. Nutrients excess and 4.9 h HRT led to soluble COD removal close to 50% (totality of the biodegradable portion) in both reactors, but only 32% was achieved at 1.6 h HRT and 45% filling degree. Restrained wastewater-biosolids contact time rather than overload justified that, as the maximum capacity (Kincannon–Stover model, 30.6 kg sCOD/(m3 d)) was substantially higher than the apparent removal rates (≤ 14.1 kg sCOD/(m3 d)). The performance at 4.9 h HRT was matched at 3.2 h HRT with threefold filling ratio, which compensated the lower contact time. Higher HRT was also responsible for i) improving nutrients usage (up to 1.72 times higher sCOD/P and 1.47 sCOD/N); ii) superior suspended solids content, corresponding up to 30% of total biomass at 4.9 h, against 8.6% at 1.6 h; and iii) up to 2.45 times greater planktonic maximum specific activity. Nutrients restriction boosted the sCOD/nutrient consumption ratio up to 2.65 times for the limited nutrient and 1.70 for the abundant one, with minimal sCOD:N:P (100:0.70:0.14) at limited N and 4.9 h HRT.

Analysis of very-high surface area 3D-printed media in a moving bed biofilm reactor for wastewater treatment.

Moving Bed Biofilm Reactors (MBBRs) can efficiently treat wastewater by incorporating suspended biocarriers that provide attachment surfaces for active microorganisms. The performance of MBBRs for wastewater treatment is, among other factors, contingent upon the characteristics of the surface area of the biocarriers. Thus, novel biocarrier topology designs can potentially increase MBBR performance in a significant manner. The goal of this work is to assess the performance of 3-D-printed biofilter media biocarriers with varying surface area designs for use in nitrifying MBBRs for wastewater treatment. Mathematical models, rendering, and 3D printing were used to design and fabricate gyroid-shaped biocarriers with a high degree of complexity at three different levels of specific surface area (SSA), generally providing greater specific surface areas than currently available commercial designs. The biocarriers were inoculated with a nitrifying bacteria community, and tested in a series of batch reactors for ammonia conversion to nitrate, in three different experimental configurations: constant fill ratio, constant total surface area, and constant biocarrier media count. Results showed that large and medium SSA gyroid biocarriers delivered the best ammonia conversion performance of all designs, and significantly better than that of a standard commercial design. The percentage of ammonia nitrogen conversion at 8 hours for the best performing biocarrier design was: 99.33% (large SSA gyroid, constant fill ratio), 94.74% (medium SSA gyroid, constant total surface area), and 92.73% (large SSA gyroid, constant biocarrier media count). Additionally, it is shown that the ammonia conversion performance was correlated to the specific surface area of the biocarrier, with the greatest rates of ammonia conversion (99.33%) and nitrate production (2.7 mg/L) for manufactured gyroid biocarriers with a specific surface area greater than 1980.5 m2/m3. The results suggest that the performance of commercial MBBRs for wastewater treatment can be greatly improved by manipulation of media design through topology optimization.

Performance of a laboratory-scale moving bed biofilm reactor (MBBR) and its microbial diversity in palm oil mill effluent (POME) treatment

The treatment performance of palm oil mill effluent (POME) using a laboratory-scale moving bed biofilm reactor (MBBR) was investigated in this study. Two types of biofilm carriers were used to fill the MBBR: black plastic media (BPM) and Hexafilter (HEX). Three media filling fractions (MFFs: 25 %, 50 % and 70 %) and retention times (RTs: 24, 48 and 72 h) were investigated to achieve the best MBBR performance in terms of the removal of chemical oxygen demand (COD) and ammonia-nitrogen (NH3-N) from POME. Increasing the RT significantly improved the removal of COD and NH3-N, whereas increasing the MFF resulted in insignificant changes. Overall, HEX performed better than BPM at 50 % MFF (72 h RT). Metagenomics analysis identified approximately 13 phyla of bacteria on the HEX compared to the BPM with only 10 phyla. Based on these findings, the laboratory-scale MBBR deserved a vote as an alternative treatment for POME under appropriate RTs and MFFs and in the presence of a suitable microbial community.

Insights into electroactive biofilms for enhanced phenolic degradation of coal pyrolysis wastewater (CPW) by magnetic activated coke (MAC): Metagenomic analysis in attached biofilm and suspended sludge

To investigate the role of electroactive biofilms for enhanced phenolic degradation, lignite activated coke (LAC) and MAC were used as carriers in moving-bed biofilm reactor (MBBR) for CPW treatment. In contrast to activated sludge (AS) reactor, the carriers improved degradation performance of MBBR. Although two MBBRs exerted similar degradation capacity with over 92% of COD and 93% phenols removal under the highest phenolics concentration (500 mg/L), the effluent of MAC-based MBBR remained higher biodegradability (BOD5/COD = 0.34 vs 0.18) than that of LAC-based MBBR. Metagenomic analysis revealed that electroactive biofilms determined phenolic degradation of MAC-based MBBR. Primarily, Geobacter (17.33%) started Fe redox cycle on biofilms and developed syntrophy with Syntrophorhabdus (6.47%), which fermented phenols into easily biodegradable substrates. Subsequently, Ignavibacterium (3.38% to 2.52%) and Acidovorax (0.46% to 8.83%) conducted biological electricity from electroactive biofilms to suspended sludge. They synergized with dominated genus in suspended sludge, Alicycliphilus (19.56%) that accounted for phenolic oxidation and nitrate reduction. Consequently, the significantly advantage of Geobater and Syntrophorhabdus was the keystone reason for superior biodegradability maintenance of MAC-based MBBR.

Anammox bacteria enrichment and denitrification in moving bed biofilm reactors packed with different buoyant carriers: Performances and mechanisms

Anaerobic ammonium oxidation (anammox) is recognized as the most cost-effective process for nitrogen removal from wastewater. In this study, effects of polyethylene plastics, nonwoven fabric, granular activated carbon (GAC) and polyurethane sponge as buoyant carriers were evaluated in lab-scale moving bed biofilm reactors (MBBRs). The overall performance of MBBRs with four types of carriers from priority to inferiority was noticed as, GAC, nonwoven fabrics, polyurethane sponge and polyethylene plastics under the same packing ratio of 20 v% and an average carrier size of 4 × 4 × 4 mm. The hydrophobic surface of GAC could selectively adsorb hydrophobic protein and favor anammox bacteria attachment, which contributed to achieving a total nitrogen removal rate of 0.40 kg-N/(m3·d) in 60 days. In conclusion, our results provide compelling evidence for achieving effective anammox process in an MBBR with GAC carriers and would benefit towards accomplishing a stable partial nitritation-anammox process in the future.

Two birds with one stone: Simultaneous improvement of biofilm formation and nitrogen transformation in MBBR treating high ammonia nitrogen wastewater via exogenous N-acyl homoserine lactones

Moving bed biofilm reactor (MBBR) is facing the challenges of slow start-up and poor treatment performance when treating high ammonia nitrogen wastewater, especially at low temperature. Exogenous N-acyl homoserine lactones (AHLs) were proposed to improve the biofilm formation and pollutant removal simultaneously for the first time. The effects of 100 nM exogenous C6-HSL and C8-HSL on the distribution of AHLs, reactor performance, biofilm characteristics and microbial community structure were systematically investigated in six lab-scale MBBRs treating wastewater with 200 mg/L ammonia nitrogen at 25 °C and 5 °C. Results showed that exogenous AHLs exhibited more significant influences during the stable operation period rather than the start-up of MBBR. Biofilm growth and EPS secretion were significantly promoted by C8-HSL (p < 0.05) while inhibited by C6-HSL at 25 °C, however, the results were opposite at 5 °C. Denitrogenation-related enzyme activities and function genes, and abundances of bacteria possessing quorum sensing and pollutants degradation ability, were heightened by exogenous AHLs (p < 0.05), thus enhancing biofilm formation and pollutants removal at room and low temperature. This study inspired a feasible strategy towards synchronous enhancement of biofilm growth and performance of MBBR treating high ammonia nitrogen wastewater through exogenous AHLs.

Impacts of typical pharmaceuticals and personal care products on the performance and microbial community of a sponge-based moving bed biofilm reactor

Four lab-scale moving bed biofilm reactors (MBBRs) were built to treat simulated wastewater containing typical pharmaceuticals and personal care products (PPCPs). The efficiency in removing different PPCPs at different concentrations (1, 2 and 5 mg/L) and their effects on the performance of MBBRs were investigated. Results showed that the average removal efficiencies of sulfadiazine, ibuprofen and carbamazepine were 61.1 ± 8.8%, 74.9 ± 8.8% and 28.3 ± 7.4%, respectively. Compared to the reactor without PPCPs, the total nitrogen (TN) removal efficiency of the reactors containing sulfadiazine, ibuprofen and carbamazepine declined by 21%, 30% and 42%, respectively. Based on the microbial community analysis, increasing the PPCPs concentration within a certain range (<2 mg/L) could stimulate microbial growth and increase microbial diversity yet the diversity reduced when the concentration (5 mg/L) exceeded the tolerance of microorganisms. Furthermore the presence and degradation of different PPCPs resulted in a different kind of microbial community structure in the MBBRs.

Evaluation of High Rate MBBR to Predict Optimal Design Parameters for Higher Carbon and Subsequent Ammoniacal Nitrogen Removal

The high rate moving bed biofilm reactor (MBBR) processes were designed for wastewater treatment to meet the past effluent discharge norms of biological oxygen demand (BOD) <50 mg/l. However, they are incapable of meeting current effluent discharge norms which consist of BOD <10 mg/l and total nitrogen <10 mg/l. This study analyses the effect and variation of organic loading rate from 1.21 kg to 4.59 kg chemical oxygen demand (COD)/(m3 day) and surface loading rate from 4.9 g to 24 g COD/(m2 day) on a high rate MBBR performance. The results of COD reduction (CODred) and subsequent ammoniacal nitrogen reduction (NH3–Nred) were in the range of 65.4% to 87.8% and 11.8% to 47.2% respectively. The projected graphical optimization defines the design parameters for MBBR and also predicts CODred and subsequent NH3–Nred. By understanding this subsequent NH3–Nred in the MBBR system, future designs for engineering technologies will be aided.

Influence of ultrasonic cell disintegration on excess sludge reduction in a Moving Bed Biofilm Reactor (MBBR)

Sludge handling is a common issue in all biological wastewater treatment methods. In this study, sonication technique as a state-of-the-art technology has been applied to a continuous MBBR system with the aim of sludge reduction. A novel configuration of MBBR with an additional recycle stream of sonicated sludge was used as the experimental setup. Based on exposed energy and sludge disruption performance, optimized sonication density and exposure time were obtained 1.5 W/mL and 15 min, respectively. This condition provided 42.2% increase in soluble COD as a result of sludge disintegration. Our results revealed that the performance of MBBR and excess sludge reduction were affected by sonicated sludge recycle ratio (SRR). The energy consumption index (EC) was defined to evaluate the optimum recycle ratio. The maximum excess sludge reduction was observed at 80% SRR, however, the effluent COD and turbidity were deteriorated considerably in comparison to control reactor. The recommended SRR was 60%, where the COD removal efficiency, effluent turbidity and excess sludge reduction were 89.7%, 19 NTU and 61.7%, respectively. Under this condition, the lowest energy consumption of 72.9 kWhkg removed sludge was observed.

Performance of moving bed biofilm reactor using effective microorganisms

Abstract This work shows the feasibility of using effective microorganisms (EM) to improve the performance of a moving bed biofilm reactor (MBBR) in treating primary settled wastewater. Two MBBR systems were compared, one inoculated with activated sludge only, and the other inoculated with a mixture of activated sludge and EM, under steady-state conditions, and under organic and hydraulic shock loadings. Results after a startup period showed that carriers in MBBR inoculated with activated sludge had only a thicker biofilm compared to MBBR inoculated with a mixture of activated sludge and EM. When compared to MBBR inoculated with activated sludge only, adding EM to the activated sludge was found to improve slightly the removal of particulate chemical oxygen demand (pCOD) and total ammonia nitrogen (TAN), while no improvement in the removal of soluble chemical oxygen demand (sCOD) was achieved. The average removal efficiencies for chemical oxygen demand (COD), sCOD, pCOD, and TAN were found to be 76.71%, 81.87%, 68.13%, and 45.92%, respectively in MBBR inoculated with activated sludge only for a period of 30 days; while those for MBBR inoculated with a mixture of activated sludge and EM were found to be 67.79%, 61.12%, 76.26%, and 56.97%, respectively, during the same period. Both MBBR systems were affected by shock loadings. Performance of MBBR inoculated with activated sludge only was much better than that for MBBR inoculated with a mixture of activated sludge and EM under both organic and hydraulic shock loadings with respect to removal of COD and TAN. MBBR inoculated with activated sludge only took much less time to reach steady-state conditions after the removal of both organic and hydraulic shock loadings when compared to MBBR inoculated with a mixture of activated sludge and EM. MBBR inoculated with a mixture of activated sludge and EM was able to reach steady-state conditions 5 h from removal of organic shock loading, while it was not able to reach original conditions after removal of hydraulic shock loading.

A kinetic study of a mesophilic aerobic moving bed biofilm reactor (MBBR) treating paper and pulp mill effluents: The impact of phenols on biodegradation rates

This study investigated the impact that phenols have on the biodegradation rate of paper and pulp mill effluents in a bench-scale aerobic moving bed biofilm reactor (MBBR). Paper and pulp mill effluents were collected from recycle and neutral sulfite semi-chemical mills. The phenol concentrations of the four individual paper and pulp mill effluents were 4.61, 29.1, 42.65 and 60.6mg/L. The removal of chemical oxygen demand (COD) was continuously monitored for individual effluents during the experiments. The hydraulic residence time (HRT) and organic loading rates (OLR) in the experiment were varied between 5 and 45h and 2–6kg COD/m3.day, respectively. The biodegradable chemical oxygen demand (COD) removal efficiency at a hydraulic residence time (HRT) of 16h was 86, 65, 60 and 46% for individual mill effluents. The Kincannon-Stover, first order and Grau second order kinetic models were evaluated to describe the removal of organics in a mesophilic aerobic MBBR. The highest correlation coefficients (r2) were found for the Kincannon-Stover model. According to the Kincannon-Stover model, the maximum substrate removal rates were 11.14, 10.46, 5.31 and 4.63 gCOD/L.day for mill effluents containing 4.61, 29.1, 42.65 and 60.6 mg/L phenols, respectively. The trend indicated that phenols inhibited the biodegradation rates of paper and pulp mill effluents in a mesophilic aerobic MBBR. Additional intermediate or pre-treatment may be required to remove excessive phenols to ultimately increase the performance of MBBRs in the paper and pulp industry.

Mixing and scale affect moving bed biofilm reactor (MBBR) performance

Moving Bed Biofilm Reactors (MBBR) are used increasingly in closed systems for farming of fish. Scaling, i.e. design of units of increasing size, is an important issue in general bio-reactor design since mixing behaviour will differ between small and large scale. Research is mostly performed on small-scale biofilters and the question is to what extent this can be upscaled to a commercial level. Therefore, the objective of this research was to establish the effect of mixing and scale on MBBR performance. The research was done in two major parts; firstly effects of scale-sensitive factors were studied in small reactors. Secondly, performance of these small reactors was then compared to increasingly large reactor sizes, using the same inlet water quality and biofilm.Firstly, a 200L MBBR (medium scale) was operated continuously using a synthetic feed solution. Biofilm carriers from this reactor was used for short-term experiments in 0.8L reactors (small scale) and compared with the performance of the 200L medium scale reactor. Reactor geometry and superficial air velocity (mh−1) were identical in these experiments. Subsequently, the small reactors were incubated with biofilm carriers from three commercial farms and performance compared with these large scale reactors. In a number of additional experiments the effect of mixing and Total Ammonia Nitrogen (TAN) was tested at small and medium scale.The results showed that MBBR scale has a significant effect on TAN removal rate. In general, the larger the scale the better the performance. TAN removal (rTAN) at small scale (0.8L) is about 80% compared to that at medium scale (200L). The difference between small scale and large scale (>20m3) is even higher. These findings warrant further studies on whether a plateau is reached in rTAN at a certain scale; a study which will have considerable importance for optimal design and dimensioning of commercial scale RAS. It was further found that superficial air velocity is not a good scaling factor for MBBRs. Upscaling while maintaining geometry implies increasing air injection depth and therefore increased energy input will be required at a comparable superficial air velocity, which is not incorporated in the superficial air velocity term (mh−1). Superficial air velocity and media filling% were found to have a strong effect on mixing time at small scale. An air velocity below a threshold of 5mh−1 decreased TAN removal at both small and medium scale. Intense mixing at small scale increased TAN removal at low TAN concentration. However, at a high TAN concentration, the small scale MBBR always performed at not more than 80% of the capacity of the medium scale system, irrespective of the mixing conditions. Hence, the capacity of full scale systems will be under-estimated when based solely on small scale experiments.