Rotating Biological Contactor Research Articles

Performance of a rotating biological contactor treating VOC emissions from paint industry

Abstract In this study, the performance of a rotating biological contactor (RBC) treating complex mixtures of VOCs commonly found in surface coating manufacturing and application facilities was evaluated. The effects of inlet loading rate (ILR) and empty bed residence time (EBRT) on elimination capacity (EC) and removal efficiency (RE) were evaluated. Methyl ethyl ketone (MEK), methyl iso-butyl ketone (MIBK), ethylbenzene, o-xylene and toluene (T) were taken as model pollutants. The performance of RBC was evaluated while treating single pollutants and various combinations of pollutants (two, three and five). Though the elimination capacity varied at different phases, the system recorded a maximum elimination capacity of 569 g/m3/h. While ketones were biodegraded mostly in the first two discs of RBC near the inlet, degradation of aromatics utilized the full reactor length. Shut-down of the circulating liquid flow affected the reactor performance more than shut-down of gas-flow or rotation of the discs. Shock–load of toluene had significant adverse effect on the reactor performance while that of ketone had no residual impact on the performance of RBC.

Control of nitratation in an oxygen-limited autotrophic nitrification/denitrification rotating biological contactor through disc immersion level variation

With oxygen supply playing a crucial role in an oxygen-limited autotrophic nitrification/denitrification (OLAND) rotating biological contactor (RBC), its controlling factors were investigated in this study. Disc rotation speeds (1.8 and 3.6rpm) showed no influence on the process performance of a lab-scale RBC, although abiotic experiments showed a significant effect on the oxygenation capacity. Estimations of the biological oxygen uptake rate revealed that 85-89% of the oxygen was absorbed by the microorganisms during the air exposure of the discs. Indeed, increasing the disc immersion (50 to 75-80%) could significantly suppress undesired nitratation, on the short and long term. The presented results demonstrated that nitratation could be controlled by the immersion level and revealed that oxygen control in an OLAND RBC should be predominantly based on the atmospheric exposure percentage of the discs.

Bacterial community dynamics in a rotating biological contactor treating 2-fluorophenol-containing wastewater

One of the main factors affecting the performance of rotating biological contactors (RBC) is the biofilm characteristics. Therefore, a deep understanding of the microbial population dynamics and structure of the biofilm is mandatory if optimization of organic matter and nutrients removal is targeted. This study focused on the effects of organic shock loads of 2-fluorophenol (2-FP) on the microbial diversity present in an RBC biofilm. The RBC was seeded with activated sludge from a conventional wastewater treatment plant and was operated during 496days. During the first 126days, the RBC was subjected to intermittent 2-FP shocks of 25mgl(-1) and no degradation occurred. Therefore, the reactor was subsequently augmented with a 2-FP-degrading strain (FP1). Afterwards, the RBC had a stable performance when subjected to 2-FP shocks up to 50mgl(-1) and to a starvation period, as indicated by removal of the compound. Denaturing gradient gel electrophoresis (DGGE) revealed large shifts in microbial communities present in the first and fifth stages, although no clear relation between the sample collection time and spatial factor was found. Phylogenetic affiliation of some predominant members was assessed by direct sequencing of correspondent DGGE bands. Affiliations to α-, β- and δ-Proteobacteria were found. Several bacterial strains isolated from the reactor showed capacity for 2-FP degradation. Strain FP1 was successfully recovered from the biofilm by plating and by DGGE, reinforcing that bioaugmentation was successfully achieved.

Biodegradation and detoxification potential of rotating biological contactor (RBC) with Irpex lacteus for remediation of dye-containing wastewater

Use of fungal organisms in rotating biological contactors (RBC) for bioremediation of liquid industrial wastes has so far been limited in spite of their significant biodegradation potential. The purpose was to investigate the power of RBC using Irpex lacteus for decolorization and detoxification of industrial dyes and dyeing textile liquors. Recalcitrant dye Methylene Blue (150 mg L−1) was decolorized within 70 days, its mutagenicity removed, and the biological toxicity decreased more than 10-fold. I. lacteus biofilm in the RBC completely decolorized within 26 and 47 days dyeing liquors containing disperse or reactive dyes adjusted to pH4.5 and 5-fold diluted with the growth medium, respectively. Their respective biological toxicity values were reduced 10- to 104-fold in dependence of the test used. A battery of toxicity tests comprising Vibrio fisheri, Lemna minor and Sinapis alba was efficient to monitor the toxicity of textile dyes and wastewaters. Strong decolorization and detoxification power of RBC using I. lacteus biofilms was demonstrated.

English

The rotating biological contactor (RBC) process was frequently used for the biological wastewater treatment in order to remove pollutants and to improve the water qualitybefore discharge to the environment. The presence of bacteria species in the secondary treated wastewater indicates the necessity of a tertiary treatment process [ultraviolet (UV)-C radiation disinfection] to reduce the number of living organisms in the water. Denaturing gradient gel electrophoresis (DGGE) method using 16S rDNA was commonly used for a direct comparison of structural diversity among different microbial communities. In the present study, community in treated and untreated wastewater from RBC treatment plantwas investigated using DGGE coupled with sequence analysis of 16S rRNA gene fragments from bands of interest. The analysis of the DGGE profiles and the sequence of the dominant DGGE bands showed a variability of the bacterial community with season. DGGE patterns of samples collected in summer were more complex than those collected in winter. In addition, the investigation of the effect of increasing UV253.7 germicidal doses on the bacterial community, in secondary treated wastewater effluent, revealed variabilityin bacterial tolerance to UV253.7 radiation. This variability is inter-specific and is dependent on the UV-C dose used and the bacterial specie irradiated. Consequently, this study demonstrated that DGGE method coupled with sequencing provides precise information on RBC and UV-C wastewater treatment process.   Key words: Wastewater, biological treatment, bacterial communities, polymerase chain reaction - denaturing gradient gel electrophoresis (PCR-DGGE), 16S rDNA, ultraviolet (UV)-C radiation disinfection.

Bioaugmentation for treating transient 4-fluorocinnamic acid shock loads in a rotating biological contactor

A rotating biological contactor (RBC) was used to treat shock loadings of 4-fluorocinnamic acid (4-FCA). Intermittent 4-FCA shocks of 35 mg L(-1) were applied (ca. 3 months) with only limited mineralization occurring and accumulation of 4-fluorobenzoate (4-FBA) as an intermediate. After bioaugmentation with a degrading bacterium the RBC was able to deal with 4-FCA intermittent loading of 80 mg L(-1) however, a gradual decline in RBC performance occurred, leading to 4-FBA accumulation. The degrading strain was recovered from the biofilm during 2 months but intermittent feeding may have led to diminishing strain numbers. Distinct bacterial communities in the 1st and the 5th and 10th stages of the RBC were revealed by denaturating gradient gel electrophoresis. Several isolates retrieved from the RBC transformed 4-FCA into 4-FBA but only two strains mineralized the compound. Bioaugmentation allowed removal of the fluorinated compound however intermittent feeding may have compromised the bioreactor efficiency.

Treatment of an agrochemical wastewater by integration of heterogeneous catalytic wet hydrogen peroxide oxidation and rotating biological contactors

The treatment of a non-biodegradable agrochemical wastewater has been studied by coupling of heterogeneous catalytic wet hydrogen peroxide oxidation (CWHPO) and rotating biological contactors (RBCs). The influence of the hydrogen peroxide dosage and the organic content of the wastewater (dilution degree) were studied. The CWHPO of the raw wastewater at 80°C and using a moderate amount of oxidant (0.23gH2O2/gTOC) reduced significantly its total organic carbon content and increased its biodegradability. Likewise, the iron leaching of the heterogeneous catalyst (Fe2O3/SBA-15) was less than 2mg/L in the treated effluent. Under the best operating conditions, the resultant CWHPO effluent was successfully co-treated by rotating biological contactors (RBCs) using a simulated municipal wastewater with different percentages of the CWHPO effluent (2.5, 5 and 10%v/v). The RBCs showed high stability for the treatment of the highest percentage of the CWHPO effluent, achieving total organic carbon (TOC) and total nitrogen (TN) reductions of ca. 78% and 50%, respectively. The integration of both processes on a continuous mode has been successfully accomplished for the treatment of the as-received agrochemical wastewater.

The Effectiveness of Anaerobic Baffled Reactor and Rotating Biological Contactor in Batik Wastewater Treatment

Batik is one of popular arts of Indonesia. The batik industries in Sragen, Central Java, are prepared to compete in global market. In order to realize that objective, batik products should fulfill some qualifications, one of which is “environmental friendliness”. As batik production is usually generating wastewater which pollutes the environment, the technology of wastewater treatment should be developed to solve the problem. This preliminary study has been done to assess the effectiveness of anaerobic baffled reactor (ABR) and rotating biological contactor (RBC) in batik wastewater treatment. In 40 days of treatment period, the ABR performance in reducing pollutants showed an effectiveness up to 75%, whereas RBC effectiveness was in the range of 15-57%. Concerning the quality standard of wastewater, the wastewater treatment system showed a good performance to decrease pH, whereas the COD was still high. Further optimization, then, is needed to improve the quality of effluent.

Anaerobic Followed by Aerobic Treatment Approaches for Spentwash Using MFC and RBC

Distillery spent wash is the unwanted residual liquid waste generated during alcohol production and pollution caused by it is one of the most critical environmental issue. Distillery spent wash is one of the recalcitrant wastes having extremely high Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Suspended Solids (SS), inorganic solids, color and low in pH. Wastewater collection, storage, treatment and management are of prime importance towards environmental pollution prevention and control. In this concern, Microbial Fuel Cell (MFC) and Rotating Biological Contactor (RBC) were fabricated and further used to treat distillery spent wash. The present study was carried out at ambient environmental conditions. Different feed concentrations of 1,100 mg COD/L to 10,100 mg COD/L was fed to MFC which treated spent wash anaerobically. As the feed concentration increased the percentage reduction of COD, BOD and Dissolved Solids (DS) increased initially up to 6,100 mg COD/L and further reduction in the removal efficiencies were observed. The highest percentage of COD, BOD and DS removal were 64, 61.2 and 44.8 % respectively at 6,100 mg COD/L and was considered as optimal effluent. The average current (0.27 mA) and power density (18.35 mW/m2) values also proved to be higher at the feed concentration of 6,100 mg/L COD. This optimal effluent was treated further aerobically in RBC and obtained 84 % COD, 81 % BOD and 46.4 % DS removal. Hence MFC and RBC can be adopted to treat spent wash in an effective manner.

Influencia de la carga orgánica sobre la eficiencia de reactores RBC de tres etapas en el tratamiento de un efluente industrial sintético

<span>El presente artículo incluye el estudio de la influencia de la carga orgánica (CO) sobre la eficiencia de reactores biológicos rotativos de contacto (RBC), aerobios de tres etapas, al tratar un efluente industrial sintético, con la finalidad de establecer la adecuación del efluente final con respecto a los límites de descarga establecidos en la normativa de Venezuela. Durante la experimentación, se evaluaron pH, alcalinidad total, oxígeno disuelto, demanda biológica de oxígeno (DBO), demanda química de oxígeno (DQO), sólidos suspendidos totales (SST), nitrógeno total Kjeldahl (NTK), NH4+, NO2- y NO3-, de acuerdo con los métodos estándares. La variación de la CO aplicada se obtuvo mediante modificación del tiempo de retención hidráulico (TRH), (24, 12 y 6 h), y se mantuvo constante la DQO de entrada (influente sintético de sacarosa+ urea). La mayor eficiencia de remoción de DQO se obtuvo para un CO global de 11,68 gDQO/m2.d (96,25%; TRH=12 h). Para los TRH 24 y 12 h, la eficiencia de remoción global de N-total fue de 66,92 y 62,95%, respectivamente. La mayor remoción de C y de N se obtuvo en la primera etapa de los reactores y se logró cumplir con el límite venezolano permisible de descarga para DQO (<350 mg/L). La posible ocurrencia del proceso de nitrificación repercutió sobre el aumento de las concentraciones de nitrógeno inorgánico en el efluente final.</span>

Reactor performance in terms of COD and nitrogen removal and bacterial community structure of a three-stage rotating bioelectrochemical contactor

Integrating microbial fuel cell (MFC) into rotating biological contactor (RBC) creates an opportunity for enhanced removal of COD and nitrogen coupled with energy generation from wastewater. In this study, a three-stage rotating bioelectrochemical contactor (referred to as RBC–MFC unit) integrating MFC with RBC technology was constructed for simultaneous removal of carbonaceous and nitrogenous compounds and electricity generation from a synthetic medium containing acetate and ammonium. The performance of the RBC–MFC unit was compared to a control reactor (referred to as RBC unit) that was operated under the same conditions but without current generation (i.e. open-circuit mode). The effect of hydraulic loading rate (HLR) and COD/N ratio on the performance of the two units was investigated. At low (3.05 gCOD g−1N) and high COD/N ratio (6.64 gCOD g−1N), both units achieved almost similar COD and ammonia-nitrogen removal. However, the RBC–MFC unit achieved significantly higher denitrification and nitrogen removal compared to the RBC unit indicating improved denitrification at the cathode due to current flow. The average voltage under 1000 Ω external resistance ranged between 0.03 and 0.30 V and between 0.02 and 0.21 V for stages 1 and 2 of the RBC–MFC unit. Pyrosequencing analysis of bacterial 16S rRNA gene revealed high bacterial diversity at the anode and cathode of both units. Genera that play a role in nitrification (Nitrospira; Nitrosomonas), denitrification (Comamonas; Thauera) and electricity generation (Geobacter) were identified at the electrodes. Geobacter was only detected on the anode of the RBC–MFC unit. Nitrifiers and denitrifiers were more abundant in the RBC–MFC unit compared to the RBC unit and were largely present on the cathode of both units suggesting that most of the nitrogen removal occurred at the cathode.

Kinetic Analysis on Rotating Biological Contactor Treatment of Organic Matter

This paper adopts a 3-stage rotating biological contactor (RBC), studies kinetic analysis on RBC treatment of organic matter .Water temperature 25 °C and hydraulic retention time (HRT) 5h , COD concentration of influent varies from about 400 to 700mg / L, the average COD removal rate is 85% . According to Monod and Michaelis-Menten formula, organic matter removal kinetics equation in the first stage of RBC can be catched. When DO≥2mg/L, organic matter removal kinetic equation: U1=7.02S1/( S1+640.70), DO<2mg/L, organic matter removal kinetic equation: U2=35.97S2/( S2+4848.92) .Where U is substrate removal rate of unit area of disc, S is the organic matter concentration of substrate. Some reference values of the equation are very useful for practical application of RBC.

Performance of a modified RBC system in simulated municipal wastewater treatment

A new method based on rotating biological contactor (RBC) was employed for solving the problems of long hydraulic retention times (HRT) low specific surface area and organic loading rates (OLR) in conventional RBCs. The system showed its particular adsorption ability of microorganisms in the biofilm-attaching period. Microbes on the first cage were observed in comparison with the second one. Packing biodisc also had a good shock load tolerance. It was observed that the system performance improved at higher HRTs, while at the increased level of input OLR, the removal performance worsened slightly. The positive role of rotational speed in the treatment of municipal wastewater was more pronounced in the range of 10-12 rpm. Chemical oxygen demand (COD) removal rate achieved 94% under the optimal operating conditions, which were HRT of 1.5 h, rotational speed of 9.9 rpm. The modified RBC system is highly beneficial to engineering application for better system performance and lower energy consumption.

Rotating Biological Contactor Reactor with Biofilm Promoting Mats for Treatment of Benzene and Xylene Containing Wastewater

A novel rotating biological contactor (RBC) bioreactor immobilized with microorganisms was designed to remove volatile organic compounds (VOC), such as benzene and xylene from emissions, and its performance was investigated. Gas-phase VOCs stripped by air injection were 98 % removed in the RBC when the superficial air flow rate was 375 ml/h (1,193 and 1,226 mg/l of benzene and xylene, respectively). The maximum removal rate was observed to be 1,007 and 1,872 mg/m(3)/day for benzene and xylene, respectively. The concentration profile of benzene and xylene along the RBC was dependent on the air flow rate and the degree of microbial adaptation. Air flow rate and residence time were found to be the most important operational parameters for the RBC reactor. By manipulating these operational parameters, the removal efficiency and capacity of the bioreactor could be enhanced. The kinetic constant K (s) demonstrated a linear relationship that indicated the maximum removal of benzene and xylene in RBC reactor. The phylogenic profile shows the presence of bacterium like Pseudomonas sp., Bacillus sp., and Enterococcus sp., which belonged to the phylum Firmicutes, and Proteobacteria that were responsible for the 98 % organic removal in the RBC.

Characterization of biofilm of a rotating biological contactor treating synthetic wastewater

A four-stage rotating biological contactor (RBC) was designed and operated to treat synthetic wastewater containing 1,000 mg/l chemical oxygen demand (COD) and 112 mg/l NH(4)(+)-N. A mixed culture bacterial biofilm was developed consisting of a heterotrophic bacterium Paracoccus pantotrophus, nitrifiers and other heterotrophs. Applying the peculiar characteristics of P. pantotrophus of simultaneous heterotrophic nitrification and aerobic denitrification, high simultaneous removal of carbon and nitrogen could be achieved in the fully aerobic RBC. The microbial community structure of the RBC biofilm was categorized based on the nitrate reduction, biochemical reactions, gram staining and morphology. The presence of P. pantotrophus within the RBC biofilm was confirmed with an array of biochemical tests. Isolates from the four stages of RBC were grouped into complete denitrifiers, incomplete denitrifiers and non-denitrifiers. This categorization showed a higher relative abundance of P. pantotrophus in the first stage as compared with subsequent stages, in which other nitrifiers and heterotrophs were significantly present. High total nitrogen removal of upto 68% was in conformity with observations made using microbial categorization and biochemical tests. The high relative abundance of P. pantotrophus in the biofilm revealed that it could successfully compete with other heterotrophs and autotrophic nitrifiers in mixed bacterial biomass.

Treatment of aqueous effluents containing non-aqueous phase liquids in rotating biological contactor with algal bacterial biofilm

Rotating biological contactors (RBCs) have been widely used for treatment of effluents containing soluble organic compounds. This study reports treatment of aqueous effluent containing diesel oil (0.6%) as a model non-aqueous phase liquid (NAPL) in a RBC. The NAPL serves as the sole substrate for the bacterial culture, Burkholderia cepacia that is inoculated along with a sessile algal culture for biofilm formation. After biofilm formation in batch mode, the 3-stage reactor was operated in a flow through mode. Data was collected over the unsteady state and also for steady state operation over hydraulic retention time (HRT) range 12–24h and total petroleum hydrocarbon (TPH) loading range 23.9–47.8gTPH/m2d. Greater than 99% removal could be achieved for TPH loading up to 31.8gTPH/m2d. The models available for predicting removal efficiency of soluble substrate at various HRT values could not be applied for this system. While the assumption of uniform distribution in each stage of the RBC is valid for soluble substrate, it is invalid for NAPLs as illustrated by the unsteady state profile. The stage-wise effluent TPH profiles obtained during unsteady-state operation was indicative of a plug flow reactor with dispersion (PFDR) with sorption and biodegradation occurring simultaneously. The diesel oil in the aqueous phase sorbed on the algal–bacterial biomass and bulk of the aliphatic fraction was biodegraded. The aromatic fraction of diesel accumulated on the biofilm. This system is very complex and new models need to be formulated for understanding and elucidating treatment of NAPL containing aqueous effluents in RBCs.

Low‐ammonia niche of ammonia‐oxidizing archaea in rotating biological contactors of a municipal wastewater treatment plant

The first step of nitrification is catalysed by both ammonia-oxidizing bacteria (AOB) and archaea (AOA), but physicochemical controls on the relative abundance and function of these two groups are not yet fully understood, especially in freshwater environments. This study investigated ammonia-oxidizing populations in nitrifying rotating biological contactors (RBCs) from a municipal wastewater treatment plant. Individual RBC stages are arranged in series, with nitrification at each stage creating an ammonia gradient along the flowpath. This RBC system provides a valuable experimental system for testing the hypothesis that ammonia concentration determines the relative abundance of AOA and AOB. The results demonstrate that AOA increased as ammonium decreased across the RBC flowpath, as indicated by qPCR for thaumarchaeal amoA and 16S rRNA genes, and core lipid (CL) and intact polar lipid (IPL) crenarchaeol abundances. Overall, there was a negative logarithmic relationship (R2 = 0.51) between ammonium concentration and the relative abundance of AOA amoA genes. A single AOA population was detected in the RBC biofilms; this phylotype shared low amoA and 16S rRNA gene homology with existing AOA cultures and enrichments. These results provide evidence that ammonia availability influences the relative abundances of AOA and AOB, and that AOA are abundant in some municipal wastewater treatment systems.

Studying the efficiency of grey water treatment by using rotating biological contactors system

The need for water is growing with increasing population and the adverse impacts of climate change especially in the Mediterranean basin. Innovative concepts and technologies are urgently needed to close the loop for water. Among the options for innovative water resources, segregation of grey water and reuse is receiving crucial attention for decentralized areas as a sustainable approach. Grey water represents substantial portion of household water consumption in volume. Treated grey water to a level complying reuse rules and regulations can be reused for several purposes including agriculture, landscaping and toilet flush. The mathematical model was used to investigate the performance and treatment capability of Rotating Biological Contactors (RBC) to treat the grey water. The GPS-X (version 5.0) simulation program was used in this study to simulate the proposed RBC plant. The proposed Rotating Biological Contactors (RBC) plant is composed of three parts, first is the RBC tank unit, second is the settling tank unit and third is the disinfection tank unit. After the model optimization, three different concentrations of the grey water were used to run the proposed mathematical model. Low, medium and high concentrations of the grey water were used to run the model. The proposed model was verified by using data from RBC experimental pilot plant. The results of this study showed that, the treatment efficiency of the RBC system based on BOD removal was ranged between about 93.0% and 96.0%, and based on TSS removal was ranged between about 84.0% and 95.0 % for all concentrations of influent grey water. Also, the proposed model results indicated that grey water can be properly treated by RBC system and can be reused for many purposes after disinfection and sand filtration.

Study on Domestic Sewage Treatment with Rotating Biological Contactor

This paper adopted a 3-stage rotating biological contactor (RBC), while the operating parameters could be controlled properly, this kind of RBC can obtain better removal effect in domestic sewage treatment. At 25oC, when hydraulic retention time (HRT) is 4h ,6h,8h,10h and 12h ,removal rate of COD is 65.14%,86.10%,89.82%,85.93% and 78.58%.HRT fixes on 8h, removal rate of NH3 –N is 75% after adjusting alkalinity. When rotating rate of RBC is 4,6,8,10,12 and 14 r/min, the removal rate of TN is 53.88%,56.78%,60.03%,58.49%,55.32% and 54.87%.RBC also has a good removal efficiency of TP and obtains the removal rate of TP 45%.There is good prospect in domestic sewage treatment with RBC.

The use of the fungus Dichomitus squalens for degradation in rotating biological contactor conditions

Biodegradation potential of Dichomitus squalens in biofilm cultures and rotating biological contactor (RBC) was investigated. The fungus formed thick biofilms on inert and lignocellulosic supports and exhibited stable activities of laccase and manganese peroxidase to reach 40–62 and 25–32% decolorization of anthraquinone Remazol Brilliant Blue R and heterocyclic phthalocyanine dyes, respectively. The decolorization ceased when glucose concentration dropped to 1mmoll−1. In RBC reactor, respective decolorizations of Remazol Brilliant Blue R and heterocyclic Methylene Blue and Azure B dyes (50mgl−1) attained 99%, 93%, and 59% within 7, 40 and 200h. The fungus exhibited tolerance to coliform and non-coliform bacteria on rich organic media, the inhibition occurred only on media containing tryptone and NaCl. The degradation efficiency in RBC reactor, capability to decolorize a wide range of dye structures and tolerance to bacterial stress make D. squalens an organism applicable to remediation of textile wastewaters.