Fixed-film System Research Articles

Attached indigenous microalgal-bacterial consortium with greater stress-resistance facilitated recovery of integrated fixed-film system after experiencing short-term stagnation inhibition

Stability of integrated fixed-film indigenous microalgal-bacterial consortium (IF-IMBC) requires further investigation. This study focused on the influence of short-term stagnation (STS), caused by influent variations or equipment maintenance, on IF-IMBC. Results showed that the IF-IMBC system experienced initial inhibition followed by subsequent recovery during STS treatment. Enhanced organics utilization was believed to contribute to system recovery. It is proposed that the attached IMBC possessed greater stress resistance. On the one hand, a higher increase in bacteria potentially participating in organic degradation was observed. Moreover, the dominant eukaryotic species significantly decreased in suspended IMBC while its abundance remained stable in the attached state. On the other hand, increased abundance for most functional enzymes was primarily observed in the attached bacteria. This fundamental research aims to bridge the knowledge gap regarding the response of IMBC to variations in operational conditions.

Performances of Polyethylene Terephthalate Plastic Bottles Waste as Supporting Media in Domestic Wastewater Treatment Using Aerobic Fixed-Film System

Performances of Polyethylene Terephthalate Plastic Bottles Waste as Supporting Media in Domestic Wastewater Treatment Using Aerobic Fixed-Film System

Organic matter removal in a simultaneous nitrification–denitrification process using fixed-film system

Swine wastewater treatment is a complex challenge, due to the high organic matter (OM) and nitrogen (N) concentrations which require an efficient process. This study focused on evaluating two different support media for OM and N removal from an Upflow Anaerobic Sludge Blanket (UASB) reactor fed with swine wastewater. Maximum specific nitrification (MSNA) and denitrification (MSDA) activity test for both biofilm and suspended biomass were carried out using as supports: polyurethane foam (R1) and polyethylene rings (R2). The results showed that R2 system was more efficiently than R1, reaching OM removal of 77 ± 8% and N of 98 ± 4%, attributed to higher specific denitrifying activity recorded (5.3 ± 0.34 g NO3-N/g TVS∙h). Furthermore, 40 ± 5% of the initial N in the wastewater could have been transformed into molecular nitrogen through SND, of which only 10 ± 1% was volatilized. In this sense, MSDA tests indicated that suspended biomass was responsible for at least 70% of N removal and only 20% can be attributed to biofilm. SND could be confirmed with the analysis of microbial diversity, due to the presence of the genus Pseudomonas dominated the prokaryotic community of the system in 54.4%.

Performance and biofilm-associated bacterial community dynamics of an upflow fixed-film microaerophilic-aerobic bioreactor system treating raw textile effluent

Textile wastewater contains numerous xenobiotic compounds which have several detrimental effects on aquatic and terrestrial ecosystems. Therefore, the adequate treatment of textile wastewater is essential. This study elucidated the biodegradation of raw textile effluent (RTE) in an upflow fixed-film microaerophilic bioreactor (UFMB) along with the characterization of its bacterial community dynamics at different hydraulic retention times (HRTs) and organic loading rates (OLRs). Among the various packing materials tested in the UFMB operation, wood charcoal was found to be the most suitable packing material for the establishment of biofilm and biodegradation of RTE. The steady-state performance of UFMB having wood charcoal as packing material achieved 81.97% of American dye manufacturers institute (ADMI) colour index removal, 73.08% of biochemical oxygen demand (BOD) removal and 80.47% of chemical oxygen demand (COD) removal at 2d HRT. Whereas, upon integration of the UFMB with the sequential aerobic bioreactor (UFMB-AB system), achieved better performances with 98.6% COD, 98% ADMI and 92% BOD removal from the RTE. Additionally, the combined UFMB-AB system effectively removed other contaminants such as sulphate, phenolics and nitrogenous compounds in the RTE. The biofilm was synergistically established by the bacterial community DR4 and the native community of RTE. In response to different HRTs and OLRs, the UFMB bacterial biofilm community experienced various shifts in its composition. However, a core microbiome persisted throughout the bioreactor operation. The imputed metagenome analysis of the established UFMB biofilm using phylogenetic investigation of communities by unobserved state reconstruction (PICRUSt), revealed the presence of several xenobiotic degradation and metabolism pathways with an abundance of various different oxidoreductase genes responsible for the biodegradation of dyes and other organic pollutants present in the RTE.

Removal of High Levels of Cyanide and COD from Cassava Industrial Wastewater by a Fixed-Film Sequencing Batch Reactor

The fixed-film sequencing batch reactor, or F-SBR, was developed to treat high organic compound levels and toxic cyanide concentrations in cassava wastewater. The performance of the F-SBR was compared with that of a conventional sequencing batch reactor, or SBR, that was operated with organic compound contents of 16,266.67–26,666 mg COD/L and 132.92–252.66 mg CN−/L. The cyanide and chemical oxygen demand removal efficiencies of the conventional SBR system were 42.61% and 36.83%, respectively, while those of the F-SBR were 77.95% and 74.43%, respectively; the cyanide removal efficiency reached 95.45% when the hydraulic retention time was increased to 5 days, and the F-SBR was very effective for the complete removal of cyanide when the hydraulic retention time was increased to 10 days. This effectiveness was similar to the effectiveness of chemical oxygen demand removal, which reached 40–78% efficiency with the F-SBR system. These results showed that the immobilization of cyanide-degrading bacteria such as Agrobacterium tumefaciens SUTS 1 and Pseudomonas monteilii SUTS 2 carried out with a polypropylene ring in a fixed-film aerobic system enhanced the performance of the reactor and can be successfully applied for cyanide and chemical oxygen demand removal from industrial wastewater with high cyanide and chemical oxygen demand concentrations. This study may provide a promising alternative technique that reduces economic operation costs in solving wastewater contamination problems.

Giardia spp. and Cryptosporidium spp. removal efficiency of a combined fixed-film system treating domestic wastewater receiving hospital effluent.

Giardia and Cryptosporidium have caused numerous outbreaks of diarrhea as a result of the ingestion of water contaminated with sewage. In Brazil, the efficiency of Giardia and Cryptosporidium removal by combined fixed-film systems has rarely been studied. The aims of the present study were therefore to verify the removal efficiency of Giardia and Cryptosporidium by a combined system (anaerobic/anoxic filter and aerated submerged biofilter) and to perform the genetic characterization of these parasites. The (oo)cysts were detected by centrifuge concentration and membrane filtration from raw sewage, effluents, adhered biomass, and sludge samples. Immunofluorescence assay and differential interference contrast microscopy were used for the visualization of the (oo)cysts. Nested PCR was applied to confirm Giardia and Cryptosporidium. Giardia and Cryptosporidium were detected in 27% and 5.5% of the 144 analyzed samples of raw sewage and effluents, respectively. A total of 33,000cysts/L were recovered in the adhered biomass samples (n= 25) from different points of the aerated submerged biofilter, while 6000oocysts/L were registered in a single point. An average of 11,800cysts/L were found in the sludge samples (n= 5). The combined system exhibited a removal efficiency of Giardia cysts of 1.8±1.0 log removal. The C and BIV assemblages of Giardia were identified in the raw sewage while AII was found in the treated effluent sample. It was not possible to calculate the removal efficiency of Cryptosporidium oocysts by the combined system. The combined system exhibited some potential as a suitable treatment for the removal of parasites from sewage.

Evaluation on the removal performance of dichloromethane and toluene from waste gases using an airlift packing reactor.

Biological removal of dichloromethane (DCM) from pharmaceutical industry is limited by its recalcitrance. In this study, an airlift packing reactor (ALPR), which combined the suspended and fixed-film microbial growth system, was set up to remove DCM and co-existed toluene. The removal performance of the ALPR for DCM was greater than traditional airlift reactor (ALR). The maximum elimination capacity (ECmax) of the ALPR for DCM reached 108 g m-3 h-1 with removal efficiency (RE) of 41%, increased by 145% if compared to the ALR. The ECmax for toluene was 172 g m-3 h-1 with RE of 70%, decreased by 25% if compared to the ALR, which was mainly due to the higher liquid-phase biomass in the ALR. The results of high-throughput sequencing showed that the microbial composition on the packings of the ALPR had a large difference from its liquid-phase or the liquid-phase of the ALR. Gemmobacter, Rhizomicrobium, Chitinophaga, Vampirovibrio, and Fodinicurvata were genera with great abundance fixed on the packings and Rhizomicrobium, Chitinophaga, Vampirovibrio, and Fodinicurvata are first to be reported in VOCs biological removal. This study indicated that the ALPR can augment the microbial community and effectively improve the removal of recalcitrant VOCs.

Enhancement of nutrient removal performance of activated sludge with a novel hybrid biofilm process.

The aim of this study was to investigate the efficacy of a hybrid biofilm pilot-scale treatment plant, designed with a novel configuration by the integration of a fixed-film system, to improve nitrogen removal. The pilot-scale system was established at a wastewater treatment plant in Istanbul and operated based on stream separation following a process consisting of Bio-P and primary sedimentation units in which carbonaceous compounds were entrapped/incorporated in settled biomass. The ammonia-rich supernatant was directed to a moving bed biofilm (MBBR) nitrification tank to obtain an efficient nitrification with the reduced organic loading after the primary sedimentation. The conventional activated sludge process, for which the net specific growth rate ([Formula: see text]) was measured to be 0.26day-1 at 15°C, exhibited a low nitrification capacity. However, the pilot-scale hybrid biofilm system secured nitrification performance up to 1.8 gN/m2/day ammonia loading, providing a competitive advantage over the conventional single sludge systems. The proposed hybrid configuration enables removal efficiencies of 80% and 85% for total nitrogen and phosphorus. It was possible to entrap organic matter by mixing 30% of return activated sludge (RAS) with raw wastewater. Simulation-based design study showed that the use of the hybrid biofilm system reduces the environmental footprint and aeration requirement of the nutrient removal by about 50% and 19%, respectively. Economic analyses highlighting the benefit of hybrid biofilm over conventional BNR system are illustrated.

Development of a mixed microbial culture for thiocyanate and metal cyanide degradation.

The degradation capacity of a mixed culture of Agrobacterium tumefaciens SUTS 1 and Pseudomonas monteilii SUTS 2 for thiocyanate and metal cyanide, in the form of zinc and cadmium, has been determined. The growth of a mixed culture of SUTS 1 and SUTS 2 in cyanide complexes and the cyanide removal efficiency of a fixed-film bio-column system were studied. The results showed that the mixed culture of bacteria can survive and grow in broth media containing thiocyanate and metal cyanide complexes with a maximum cell of 1.03×108CFU/mL on day 3. In addition, the optimal conditions of the fixed-film bio-column system were continuously tested for 24h, and it was found that this system had the highest removal efficiency at a flow rate of 10mL/min and 21min of empty bed retention time, with decreasing thiocyanate, zinc, and cadmium from 85, 0.44, and 0.044 to 65, 0.21, and 0.038mg/L, respectively; this is in contrast to cyanide, which was not found within 12h. Next, the conditions were maintained for 30days, and it was found that the system had removed more than 50% of cyanide complexes, except cadmium. The complex residues were 29.96, 0.16, 0.204, and 0.085mg/L of thiocyanate, cyanide, zinc, and cadmium, respectively. In addition, the growth of the SUTS 1 and SUTS 2 mixed culture increased. The by-product compounds sulfate and nitrate were found throughout the experiment, whereas bicarbonate and ammonia were found only on certain days.

Modeling of Temperature Impacts on Fixed Film Microbial Growth and Nitrification Kinetics

Monod-type kinetic models, used in simulating microbial growth in biological treatment systems, suggest significant decreases of substrate utilization at lower temperatures. However, it is documented that performance of fixed film treatment systems are not hindered with declining temperatures. Previous studies at the Moorhead, MN, Wastewater Treatment Facility (WWTF) showed significant impacts of temperature on biofilm growth in its moving bed biofilm reactor (MBBR), and studies noted that at low temperatures more biomass was present. Previously, a series of kinetic bench-scale batch tests was performed to measure ammonium removal in the full-scale system. As part of this research, a diffusion based kinetic model was developed to simulate the bench-scale trials and determine if Monod kinetics and temperature corrections properly model fixed film systems. It was found that Monod kinetics and temperature corrections do apply to fixed film system as long as proper consideration is given to the change in biofilm characteristics.

Treatment of dairy wastewater by fixed-film system in continuous flow

abstract The objective of this work was to assess the feasibility of biological phosphorus removal for dairy processing wastewater. In this study, two fixed-film systems carried out continuously were tested in the laboratory. The effect of aerobic and “anoxic/anaerobic/aerobic” conditions on phosphates removal has been investigated on both the fixed-film systems and reported, that alternating phase’s system (bioreactor 1) resulted in higher phosphorus removals relating to aerobic system (bioreactor 2). The main results showed that the effectiveness of COD and phosphates for bioreactor 1 reached, respectively, to 66 and 91% at stable biofilm functioning. Similarly, the effectiveness of COD and phosphates removal for bioreactor 2 reached to 70 and 84.61%, respectively. No clogging of media occurred and no backwashing was applied on both the systems during the study. Also, kinetic analysis of the reactor with regard to phosphorus removal has been studied with the modified Stover-Kincannon kinetic model which...

Transformation of phosphorus in intermittent aerated biofilter under aerobic continuous feeding with long backwashing intervals

A combined fixed-film system composed of anaerobic biofilter, aerobic biofilter, and intermittent aerated biofilter (IABF) is developed for enhanced biological phosphorus removal (EBPR) treating domestic wastewater. This work presents details on the performance of IABF under aerobic condition, where phosphorus-accumulating organisms are accumulated. Analysis on distribution of phosphorus in both the bulk and the biofilm indicates that the PAOs-rich biofilm is characterized by a high activity, a strong P capacity, and a good adaptability of fluctuations in aerobic continuous loading. An innovative means for P removal slows down accumulation of P in biofilm. As a result, removal of P-rich biomass is no longer a key limitation of EBPR performance in the biofilm system. Long backwashing interval is practicable in IABF under aerobic continuous feeding regime.

Hydrogen sulfide removal by a novel fixed-film bioscrubber system

The fixed-film bioscrubber was developed for hydrogen sulfide removal. Acinetobacter sp. MU1_03 and Alcaligenes faecalis MU2_03 are two new strains of microorganisms from the fixed-film bioscrubber systems found. Under certain conditions, they exhibited more than 91% of hydrogen sulfide removal efficiency while a mixture of the two strains was capable of 98% hydrogen sulfide removal. Removal efficiency increased with decreasing inlet gas flow rates, increasing the height of packing and empty bed retention time. During the operation, the pH decreased but did not fall below 6.4. Sulfate production increased when the removal efficiency increased due to the oxidation of hydrogen sulfide to sulfate. In addition, dissolved oxygen decreased during the same reaction.

A pilot study for oil refinery wastewater treatment using a fixed-film bioreactor

Biological treatment of industrial oil refinery wastewater is a well-established method for remediation of these wastes. We have designed a new bioreactor system to increase the efficiency of biological treatment systems by (1) allowing greater organic loads, (2) minimizing production of sludge waste by-products, and (3) increasing process stability and resistance to shock loading. A fixed-film bioreactor system was constructed with a highly porous polyurethane foam to incubate microorganisms at concentrations up to 8000 mg/l. The support frame of the bioreactor system was built from cylindrical plastic pall rings to form a packed bed of ‘mixed-media’. The frame support provides a high surface area-to-volume ratio (210 ft 2/ft 3), and reduces potential problems of plugging and channeling, distribution of air and water, and mass-transfer limitations. Performance data for fixed-film bioreactors with 8-h hydraulic retention time (HRT) demonstrated chemical oxygen demand (COD) removal rates of 85–90%, and near 100% degradation of phenol from industrial oil refinery wastewater. Furthermore, the pilot bioreactor only generated one-third of the sludge waste compared to the traditional activated sludge process.

Biotreatment of Oil-Bearing Coke-Oven Wastewater in Fixed-Film Reactor: A Viable Alternative to Activated Sludge Process

Coke-oven wastewater is produced in the integrated steel plants at coke-oven gas-cleaning operations. It is laden with phenol, cyanide, thiocyanate, and oil. Although the activated sludge process is widely practiced in the biological treatment of coke-oven wastewater, it was observed during field visits that oil contamination and poor sludge settleability had resulted in poor maintenance of the activated sludge process. These problems can be minimized by the use of fixed-film systems such as trickling filters; however, availability of a microbial consortium, which would sustain oil contamination, was a major constraint. Research endeavor at this Institute has resulted in the development of such a microbial consortium, and the same was applied on a bench-scale fixed-film system such as a trickling filter, for the treatment of coke-oven wastewater. The unit was set up in the steel industry, and fresh coke-oven wastewater was treated over a period of 45 days. The results indicated that phenol and oil were simultaneously degraded and the system was stable. The studies established that the fixed-film system could be a viable alternative to the activated sludge process if appropriate microbial consortium is adopted.

Sugar wastewater treatment with aerated fixed-film biological systems

Wastewater effluents from the sugar industry contain high concentrations of organic materials which are sometimes discharged into the municipal wastewater collection system and processed in wastewater treatment plants along with domestic wastewater. This study examined the performance of a four-compartment, fixed-film system in which the biofilm is attached to submerged ceramic tiles under diffused aeration, known as the aerated submerged fixed-film (ASFF) process. Field experiments were conducted using four ASFF units each of about 100 1 capacity operated at different hydraulic loading rates to provide hydraulic residence time (HRT) of 2, 4, 6 and 8 hours. Process performance was evaluated under both normal operation with domestic wastewater and under pulse and prolonged organic shock loads with sugar wastewater. The influent and effluent of the process was analyzed for solids, BOD, COD, and nitrogen forms to determine both carbonaceous and nitrogenous substrate removal. The ASFF process was found to be able to handle continuous severe organic loads increasing from about 5 to 120 g BOD/m2.d with slight decrease in organic removal efficiency from 97.9% to 88.5% for BOD and from 73.6 to 67.8% for COD. Nitrification was similarly decreased but at higher rates. The system was also able to cope with pulse injection of sugar wastewater and recovery to normal steady-state COD values was achieved in 10 hours for the 200 g COD/l spikes. An increase in the organic loading rate was accompanied by an increase in biofilm specific oxygen uptake rate until reaching a maximum which determines the optimum loading rate for process operation. Substrate removal rates were evaluated for process design.

Sugar wastewater treatment with aerated fixed-film biological systems

Wastewater effluents from the sugar industry contain high concentrations of organic materials which are sometimes discharged into the municipal wastewater collection system and processed in wastewater treatment plants along with domestic wastewater. This study examined the performance of a four-compartment, fixed-film system in which the biofilm is attached to submerged ceramic tiles under diffused aeration, known as the aerated submerged fixed-film (ASFF) process. Field experiments were conducted using four ASFF units each of about 100 1 capacity operated at different hydraulic loading rates to provide hydraulic residence time (HRT) of 2, 4, 6 and 8 hours. Process performance was evaluated under both normal operation with domestic wastewater and under pulse and prolonged organic shock loads with sugar wastewater. The influent and effluent of the process was analyzed for solids, BOD, COD, and nitrogen forms to determine both carbonaceous and nitrogenous substrate removal. The ASFF process was found to be able to handle continuous severe organic loads increasing from about 5 to 120 g BOD/m2.d with slight decrease in organic removal efficiency from 97.9% to 88.5% for BOD and from 73.6 to 67.8% for COD. Nitrification was similarly decreased but at higher rates. The system was also able to cope with pulse injection of sugar wastewater and recovery to normal steady-state COD values was achieved in 10 hours for the 200 g COD/l spikes. An increase in the organic loading rate was accompanied by an increase in biofilm specific oxygen uptake rate until reaching a maximum which determines the optimum loading rate for process operation. Substrate removal rates were evaluated for process design.

Chromium(VI) Reduction by Pseudomonas fluorescens LB300 in Fixed-Film Bioreactor

The potential for Cr(VI) reduction in a bench-scale, fixed-film bioreactor system was investigated using a Cr(VI) reducing bacterial species, Pseudomonas fluorescens LB300. The bench-scale reactor was packed by glass beads and was operated to steady-state conditions with near complete removal of Cr(VI) under a range of influent Cr(VI) concentrations (30–100 mg/L) and hydraulic retention times (3.6–14.2 min). Cr(VI) overloadings were observed when the bioreactor system was operated at 200 mg Cr(VI)/L under a 14.2 min hydraulic retention time and at 50 mg Cr(VI)/L under a 3.6 min hydraulic retention time. The system recovered in both cases after reducing Cr(VI) loadings by lowering influent Cr(VI) concentration to 10 mg/L. Cr(VI) reduction was carried out by biological mechanisms through both attached and suspended biomass. Control studies using Cr(VI) showed that abiotic Cr(VI) reduction in the bioreactor was insignificant. Nearly all the influent Cr(VI) reduced in the reactor was recovered in the form of Cr(III) in the effluent.

Experience with nutrient removal in a fixed-film system at full-scale wastewater treatment plants

In the upgrade of wastewater treatment plants to include biological nutrient removal the space available is often a limiting facor. It may be difficult to use conventional suspended growth processes (i.e. activated sludge) owing to the relatively large surface area required for these processes. Recent years have therefore seen a revived interest in treatment technologies using various types of attached growth processes. The “new” attached growth processes, like the Biostyr process, utilise various kinds of manufactured media, e.g. polystyrene granules, which offer a high specific surface area, and are therefore very compact. The Biostyr plants allow a combination of nitrification-denitrification and filtration in one and the same unit. The results obtained are 8 mg total N/l and an SS content normally below 10 mg/l. The plants in Denmark which have been extended with a Biostyr unit have various levels of PLC control and on-line instrumentation.

Experience with nutrient removal in a fixed-film system at full-scale wastewater treatment plants

In the upgrade of wastewater treatment plants to include biological nutrient removal the space available is often a limiting facor. It may be difficult to use conventional suspended growth processes (i.e. activated sludge) owing to the relatively large surface area required for these processes. Recent years have therefore seen a revived interest in treatment technologies using various types of attached growth processes. The “new” attached growth processes, like the Biostyr process, utilise various kinds of manufactured media, e.g. polystyrene granules, which offer a high specific surface area, and are therefore very compact. The Biostyr plants allow a combination of nitrification-denitrification and filtration in one and the same unit. The results obtained are 8 mg total N/l and an SS content normally below 10 mg/l. The plants in Denmark which have been extended with a Biostyr unit have various levels of PLC control and on-line instrumentation.