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The goal of this study was to unravel the impact of high and low temperatures (T) on glycogen-accumulating microorganisms (GAOs) which were stimulated in an aerobic granular sludge plant fed with industrial wastewater, which is derived from the cleaning of trucks transporting chocolate and beer. Among GAOs, Candidatus Competibacter (Ca. Competibacter) was the most abundant. The long-term impact on (1) anaerobic dissolved organic carbon (DOC) uptake, (2) sludge morphology, and (3) microbial community composition was investigated. In addition, the short-term impact of T changes on the anaerobic uptake rate was evaluated. High T (above 38 °C) and low T (below 11 °C) had a negative impact on the relative read abundance of Ca. Competibacter and the anaerobic DOC uptake. Nevertheless, the carbon removal efficiency and the settleability of the biomass were not affected. Denitrifiers such as Thauera and Zoogloea were promoted over Ca. Competibacter under high T and low T, respectively, indicating their positive contribution to granulation maintenance. HIGHLIGHTS The long-term exposure to high T completely inhibited Ca. Competibacter.; The long-term exposure to low T decreased the Ca. Competibacter population but not at an alarming level.; The short-term exposure of sludge enriched with Ca. Competibacter to high T did not affect the carbon uptake rate.; The short-term exposure of sludge enriched with Ca. Competibacter to low T negatively affected the carbon uptake rate.;

The application of a hybrid-fruit-peel (HFP) coagulant used as an external carbon source (ECS) in both simulated water and real sewage having a low carbon source treated with sequencing batch reactor (SBR) was studied, compared with that of sodium acetate (NaAc). The impact of HFP on sludge properties (such as extracellular polymer substance (EPS), dehydrogenase activity (DHA), charged property, size, microscopic images and bacteria phase) was characterized. The results showed that as an ECS, HFP basically gave similar nitrogen removal to NaAc and also gave a similar developing trend of both dissolved oxygen (DO) and pH. HFP promoted more proliferation of microorganisms and posed higher levels of protein (PN) and polysaccharide (PS) than NaAc, but gave slightly lower DHA than NaAc. After HFP was added as an ECS, the types and quantities of microorganisms increased significantly, the effluent qualities were improved and the sludge size and extensibility became larger, which was conducive to direct contact and remove pollutants. HFP played a similar role to NaAc as ECS and can be used as a quality and slow-releasing ECS for low carbon source wastewaters. HIGHLIGHTS Application of HFP coagulant as an external carbon source (ECS) for low C/N wastewater was studied and gave a similar effect to NaAc.; HFP can be used as a quality and slow-releasing ECS for low C/N wastewater.; HFP produced sludge has a larger size and better extensibility.; HFP promoted more proliferation of microorganisms and gave better effluent qualities.;

In this study, sequencing batch reactor (SBR) using anaerobic/aerobic/anoxic process was coupled to a solar photocatalytic reactor (SPCR) for greywater treatment. The greywater effluent from SBR (operated at the optimal condition: 6.8 h hydraulic retention time (HRT), 0.7 Volumetric exchange ratio (VER) and 7.94 d solids retention time (SRT) with optimal corn cob adsorbent dosage (0.5 g/L)) was fed to the SPCR (operated at optimal conditions: pH – 3, H2O2 dosage – 1 g/L, catalyst dosage – 5 g/L). Chemical oxygen demand (COD) removal of 92.8±0.5% and ∼100% were achieved in SBR and SBR-SPCR, respectively. Similarly, total organic carbon (TOC) removal of 91±0.9% and ∼100% were observed in SBR and SBR-SPCR, respectively. After SBR treatment, average total nitrogen (TN) removal of 84% was found and this TN removal increased to 93% after combined SBR-SPCR treatment. The maximum PO43−_P reduction of 80±1.5% % was achieved with SBR-adsorption system. In addition, a maximum of 87±0.9% of net PO43−_P removal was reached after SBR-SPCR treatment. 58.9±2.3% BP (benzophenone-3) removal was obtained in the SBR while the integration of SBR and SPCR treatment was resulted in 100% BP removal. An effective anionic surfactant (AS) removal rate (80.1±2.2%) was observed in the SBR phase, which further improved to 94.9±1% at the end of 4 h SPCR treatment. HIGHLIGHTS Biological – photochemical system successfully treated greywater.; The coupled system efficiently mineralizes COD, TOC and BP.; Significant removal of TN (93%), PO43−_P (87%) and AS (94.9%) was achieved.; Solar photocatalysis was able to remove emerging contaminants.; Treated SBR-SPCR greywater could meet reuse standards (toilet flushing and others).;

In this study, the performance of the membrane bioreactor (MBR) and anoxic–aerobic sequencing batch reactor (SBR) are compared in treating municipal wastewater. The aim of the work was to determine the feasibility of these systems for the removal of organics matter and nutriments from the municipal wastewater. The MBR displayed a superior performance with removal efficiencies exceeding 99% for TSS, 94% for chemical oxygen demand (COD) and an improvement on SBR efficiencies was found. In the same way, the MBR produced an effluent with much better quality than SBR in terms of total nitrogen (TN) and total phosphorus (TP) removal efficiencies. Combining membrane separation and biodegradation processes or the membrane bioreactor (MBR) technology improved pollution removal efficiencies significantly. Highlights Municipal wastewater treatment.; Membrane bioreactor process.; SBR process evaluation.; Organic pollution removal.; Reuse in irrigation.;

The effects of CeO2 nanoparticles (NPs) on the system performance and the bacterial community dynamics in a sequencing batch reactor (SBR) were investigated, along with the fate and removal of CeO2 NPs within the SBR. Significant impact was observed on nitrification; NH+4-N removal efficiency decreased from almost 100% to around 70% after 6 days of continuous exposure to 1.0 mg/L of CeO2 NPs, followed by a gradual recovery until a stable value of around 90% after 20 days. Additionally, CeO2 NPs also led to a significant increase in the protein content in the soluble microbial products, showing the disruptive effects of CeO2 NPs on the extracellular polymeric substance matrix and related activated sludge structure. Denaturing gradient gel electrophoresis analysis showed remarkable changes in the bacterial community structure in the activated sludge after exposure to CeO2 NPs. CeO2 NPs were effectively removed in the SBR mainly via sorption onto the sludge. However, the removal efficiency decreased from 95 to 80% over 30 days. Mass balance evaluation showed that up to 50% of the NPs were accumulated within the activated sludge and were removed with the waste sludge. [ABSTRACT FROM AUTHOR]

In this research, two sequencing batch reactors (R1 and R2) were operated with different feeding strategies to investigate the effects of elongated anaerobic feeding mode on the granulation process. For this purpose, R1 was operated in a short-feed strategy (5 min) as a reference, whereas an extended anaerobic feeding of 85 min was applied in R2. Results showed that aerobic granules formed in R1 were denser and more uniform with lower sludge volume index than those formed in R2. Investigation of tightly bound extracellular polymeric substances (TB-EPS) showed that aerobic granules in R1 produced lower amounts of TB-EPS than those in R2. This was due to the bigger and more compact granules cultivated in R1 in comparison with looser structure granules in R2 with higher flocculent sludge percentage. The relative hydrophobicity of granules in both reactors was increased with culture time and reached about 63 and 65% at day 70 for R1 and R2, respectively. Moreover, no significant correlation between protein/polysaccharide ratio and hydrophobicity was found, which showed that protein in loosely bound extracellular polymer substances was not the predominant hydrophobic component. Considering the outcomes of this study, it can be concluded that the elongated anaerobic feeding strategy was unfavourable for cultivating aerobic granules. [ABSTRACT FROM AUTHOR]

Aerobic granules to treat wastewater containing o-nitrophenol were successfully developed in a sequencing batch reactor (SBR) using activated sludge as inoculum. Stable aerobic granules were obtained with a clearly defined shape and diameters ranging from 2 to 6 mm after 122 days of operation. The integrity coefficient (IC) and granules density was found to be 98% and 1,054 kg m-3 respectively. After development of aerobic granules, o-nitrophenols were successfully degraded to an efficiency of 78% at a concentration of 70 mg L-1. GC-MS study revealed that the biodegradation of o-nitrophenol occurred via catechol via nitrobenzene pathway. Specific o-nitrophenol biodegradation rates followed the Haldane model and the associated kinetic parameters were found as follows: Vmax = 3.96 g o-nitrophenol g-1VSS-1d-1, Ks = 198.12 mg L-1, and Ki = 31.16 mg L-1. The aerobic granules proved to be a feasible and effective way to degrade o-nitrophenol containing wastewater. [ABSTRACT FROM AUTHOR]

Pulp and paper mills are under increasing pressure to minimize the discharge of phosphate to receiving waters. we investigated the operation of two laboratory sequencing batch reactors (SBR) under low phosphate conditions over a period of eight months. Performance characteristics in terms of COD and TSS removal were similar to the full-scale mill activated sludge operation, but the floc density and structure was improved. Sludge yield as a result of phosphate limitation was routinely lower than 0.15kg/kg of COD. Aerobic granule formation was established in one of the SBRs by reducing the settling time from 30mm to 2mm and by increasing stirring shear force. Once established, the brown granules which were 1-2 mm in diameter were stable over five months of operation. Extracellular polymeric substance (EPS) analysis of the granules indicated a higher galactose content and lower mannose content than in conventional flccs. The granules generated more quorum sensing compound (acyl homoserine lactone) than conventional flocs, suggesting that quorum sensing could play a role in granule formation. when compared to the conventional SBR, the aerobic granule SBR performed at a higher organic loading, at faster settling velocity, and without filamentous bulking. [ABSTRACT FROM AUTHOR]

When treating effluents from anaerobic processing of organic wastes, the challenge lies in the large quantity of recalcitrant COD and in the high nitrogen content. The data presented in this study illustrate an advanced SBR concept that is able to significantly reduce the organic load. It was found that undigested mashed bio-waste bypassing the anaerobic digestion is highly suitable as an external carbon source to compensate deficiencies of readily biodegradable BOD required for denitrification. In order to utilize the carbon source as efficiently as possible, the SBR was operated in a mode by which nitrification/denitrification is achieved by a shortcut process using nitrite. This procedure reduced the requirement of an external carbon source to only 5% (v/v). Moreover, through an optimized SBR sequence for an influent concentration of 14,000mgCOD/l and 3,800 mg TN/l, nearly complete removal of nitrogen (.95%) was achieved. The average removal rates for COD and BOD were 83% and 86%, respectively. The applied hydraulic retention time (HRT) of the SBR was 6.8 days. The elevated temperature of 30-41°C in the reactor as a result of the high biological activity was advantageous in terms of enhanced reaction kinetics and also provided better process stability. [ABSTRACT FROM AUTHOR]

Integrated operation strategies for combined sewer and WWTP are becoming more and more popular because of numerous benefits. One can find many examples in literature, but many of these studies deal with partly fictitious systems and/or were accomplished within the planning. Hence most of these studies do not have to deal with the restrictions given by already built constructions. The authors, who worked on several integrated projects, will discuss the requirements of SBR and CFR plants concerning an implementation of integrated operation. [ABSTRACT FROM AUTHOR]

Laboratory batch experiments were conducted to investigate pH profiles during partial and complete denitrification with sufficient organic carbon source. Five stirred tank-type glass vessels, with a 7 L working volume for each, were used as SBR reactors that were all operated in denitrification mode. Five levels of initial proportion of nitrogen substances, i.e. nitrate and nitrite, were used in five reactors, respectively. Results showed that, at given temperature and mixed liquor suspended solids (MLSS), partial denitrification could attain a higher pH value than complete denitrification at the end of denitrification with the same initial NOx- concentration. The larger proportion the nitrite took in initial NOx- concentration, the higher pH peak would be obtained on pH profiles during denitrification despite the same total alkalinity produced. It was found that different types of alkalinity were produced during biological denitrification with different nitrogen substances. Partial denitrification could more carbonate alkalinity produce than complete denitrification. Furthermore, some characteristic points were identified on pH profiles which could indicate the disappearance of not only nitrate, but also nitrite in system. When computers are used to detect these features, they can provide rapid, real-time information, regarding the biological state of the system. [ABSTRACT FROM AUTHOR]

A process for autotrophic nitrogen removal named aerobic/anoxic deammonification wherein NH4+ is oxidized by nearly 50% to NO2- and subsequently the ammonia is converted together with the nitrite to molecular nitrogen (N2 gas), has come to full-scale application within the last few years. In this research, sludge from a biological rotation disk located at a landfill leachate plant at Mechernich, Germany, which is capable of performing the deammonification process, was used as seed sludge for acclimating deammonification activities in laboratory scale batch-reactors. In parallel, the same tests were performed with normal activated sludge. Research results indicated that deammonification activities could be obtained from the seeded reactor and also, with limited performance, from normal activated sludge in a single SBR system after several months acclimation. It was also seen that oxygen is an important factor that influences the deammonification from both the acclimatization process and process running. Further results were approved that report an impact of nitrite as a process intermediate on the closely related process of anaerobic ammonia oxidation ("Anammox"). However, limiting concentrations on a bacteria population performing deammonification were found to be different to those reported for a pure Anammox-culture. Also the influence of another intermediate, hydrazine, was tested for speeding up the acclimating process by inducing the deammonification activities and recovering the activities of deammonification from nitrite inhibition. [ABSTRACT FROM AUTHOR]

Self-immobilized biofilms, or aerobic granules without the addition of carrier material, have only been reported in one suspended growth system, the Sequencing Batch Reactor (SBR) with a very short fill time (dump fill). The SBR utilizes intermittent feeding which creates a period of high load followed by starvation (often referred to as feast-famine). In this experiment, three identical SBRs were operated with different feeding conditions to determine the role of feast-famine on granule formation. All three SBRs were operated with a total volumetric load of 2.4 kg/m³ ⋅ d. The 90 minute Fill phase was altered for each reactor, providing an increasing time of Aerated Fill. A dump fill condition was applied for one reactor, while the other two reactors were aerated for different times during Fill, resulting in a smaller COD load at the beginning of each React phase. Aerobic granules formed in all reactors, but the structural properties and content of filamentous organisms were clearly dependent on a high feast condition. Only the reactor with dump fill formed compact, stable granules. It is concluded that intermittent feeding associated with the SBR affects the selection and growth of filamentous organisms and has a critical role in granule structure and composition. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the feasibility of the Sequencing Batch Reactor (SBR) system for implementation in Malaysia. Theoretical, field, laboratory investigations, and modelling simulations have been carried out. The results of the study indicated that the SBR system was robust, relatively cost-effective, and efficient under Malaysian conditions. However, the SBR system requires highly skilled operators and continuous monitoring. This paper also attempted to identify operating conditions for the SBR system, which optimise both the removal efficiencies and the removal rates. The removal efficiencies could reach 90-96% for COD, up to 92% for TN, and 95% for SS. An approach to estimate a full operational cycle time, to estimate the de-sludging rate, and to control the biomass in the sludge has also been developed. About 4 hours react time was obtained, as 2.25 hours of nitrification with aerated slow fill and 1.75 hour of denitrification with HAc addition as an additional carbon source. Inefficient settling was one of the problems that affect the SBR effluent quality. The settling time was one hour for achieving Standard B (effluent quality) and 2 hours for Standard A. [ABSTRACT FROM AUTHOR]

Nitrifying bacteria were selected from shrimp farm water and sediment ("natural" seed) in Thailand and from commercial seed cultures. The microbial consortia from each source giving the best ammonia removal during batch culture pre-enrichments were used as inocula for two sequencing batch reactors (SBRs). Nitrifiers were cultivated in the SBRs with 100 mg NH4-N/l and artificial wastewater containing 25 ppt salinity. The two SBRs were operated at a 7 d hydraulic retention time (HRT) for 77 d after which the HRT was reduced to 3.5 d. The amounts of ammonia removed from the influent by microorganisms sourced from the natural seed were 85% and 92% for the 7 d HRT and the 3.5 d HRT, respectively. The ammonia removals of microbial consortia from the commercial seed were 71% and 83% for these HRTs respectively. The quantity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was determined in the SBRs using the most probable number (MPN) technique. Both AOB and NOB increased in number over the long-term operation of both SBRs. According to quantitative fluorescence in situ hybridisation (FISH) probing, AOB from the natural seed and commercial seed comprised 21 ± 2% and 30 ± 2%, respectively of all bacteria. NOB could not be detected with currently-reported FISH probes, suggesting that novel NOB were enriched from both sources. Taken collectively, the results from this study provide an indication that the nitrifiers from shrimp farm sources are more effective at ammonia removal than those from commercial seed cultures. [ABSTRACT FROM AUTHOR]

In this research, the effects of different color intensities, anoxic+anaerobic times and types of substrate on color removal effectiveness were studied using 16-litre bench scale sequencing batch reactor (SBR) anoxic+anaerobic/aerobic models. The systems were fed with a synthetic wastewater containing 500 mg/l of COD, 50 mg/l of N, 15 mg/l ofP along with 10, 40 and 80 mg/l of reactive diazo Remazol Black B dye. The anoxic+anaerobic/aerobic periods were 0/11 (normal aerobic SBR), 2/9, 4/7 and 8/3 hours, respectively. The color removal occurred mainly under the anaerobic environment, while a slight attenuation wasnoticed under the aerobic condition. A better decolorization could be achieved with a longer anoxic+anaerobic period. The sodium acetate was a slightly better co-substrate for the color removal than glucose. The decolorization efficiency dwindled as the fed dye concentrationincreased, but the overall color removal leaned in the opposite direction. The phosphorus removal of the anoxic+anaerobic/aerobic systemswas outstanding, whereas only 50% removal was achieved for the aerobic process. A dye concentration of up to 80 mg/l did not have any significant impact on the performance of the polyphosphate accumulating organisms (PAOs). The removal of organic carbon and TKN was comparable among all experiments regardless of system configurations, color intensities and types of substrate. [ABSTRACT FROM AUTHOR]

The relationships between bacterial storage products, density, and settling characteristics were determined in a laboratory-scale sequencing batch reactor (SBR) enhanced biological phosphorus removal (EBPR)system. Both long-term and single anaerobic-aerobic cycle variationsin these properties were studied. Increased polyphosphate (PP) content of the biomass during long-term operation resulted in improved sludge volume index (SVI) values. End-aerobic phase (after phosphate (P)uptake) values were consistently lower than end-anaerobic phase (after P release) values. Neither filamentous nor slime bulking were evident by microscopic observations. Biomass density increased at a rate of 1.2 mg/L per each 1% increase in biomass P content. End-aerobic phase samples had an average 25% higher buoyant density than end-anaerobic phase samples, which was attributed to aerobic P uptake. Biomass density was negatively correlated with SVI values, and SVI values increased sharply at low biomass density. A mathematical model developedby Mas et al. (1985) was modified to predict total cell density based on literature values of PP, glycogen (GLY), and poly-b-hydroxybutyrate (PHB) densities. Model predictions were in good agreement with experimental results, although improved measurement of PP density is required to improve model predictions. [ABSTRACT FROM AUTHOR]

Using the Western blot immunochemical analysis method, the heat shock protein, GroEL, was found to be either induced or repressed in activated sludge microorganisms exposed to a range of xenobiotics. At theEC25 concentration, pentachlorophenol (PCP), cadmium, nickel, 2,4-dichloroaniline, benzoquinone, 2,4-dinitrophenol, and 1,1,1-trichloroethane all rapidly induced measurable GroEL expression, eventhough the time-dependent response for each of these compounds was somewhat varied. Toluene and hydroquinone resulted in repression of GroEL expression to levels below that measured in the control mixed liquor. For PCP concentrations at or exceeding the EC25, there was a significant and consistent increase in effluent volatile suspended solids from activated sludge sequencing batch reactors relativeto unstressed controls. These preliminary results indicate that stress proteins may serve as sensitive and rapid indicators of toxicity which can adversely impact treatment process performance in activated sludge systems. [ABSTRACT FROM AUTHOR]

Laboratory experiments were conducted to investigate the performanceof an anaerobic sequencing batch reactor (ASBR) process for night soil treatment. Performances of the reactors were evaluated at an equivalent hydraulic retention time (HRT) of 10 days with an equivalent loading rate of 2.6 kgVS/m3/d (3.1 kgCOD/m3/day) at 35 deg. C. Digestion of a night soil was possible using the ASBR at an HRT of 10 days in spite of high concentration of ammonia nitrogen and settleable solids. Solids were accumulated rapidly in the ASBRs, and their concentrations were 2.3~2.4 times higher than that in a completely mixed control reactor. Remarkable increases in gas production were observed in the ASBRs compared with the control reactor. Average increases in equivalent daily gas production from the ASBRs were 205~220% compared with that from the control run. The ASBR with reaction period/thickening period ratio (R/T ratio) of 1 showed a little higher gas production and organic removal efficiency than that with R/T ratio of 3. Volatile solids removals based on supernatant of the ASBRs were 12~14% higher than that of the control reactor. Thus, the ASBR was a stable and effective process for the treatment of night soilhaving high concentration of settleable organics and ammonia nitrogen. [ABSTRACT FROM AUTHOR]

Biological phosphorus and nitrogen removal in biofilm processes havea potential advantage compared to activated sludge processes, because of less vulnerability with respect to sludge loss and because biofilm processes, in general, are more compact with a smaller footprint. Experiments have been carried out in a moving bed biofilm reactor operated as a sequencing batch reactor (SBR), with simultaneous nitrification, phosphorus uptake and denitrification in the aerobic phase. Inorder to achieve good phosphorus and nitrogen removal, the length ofthe anaerobic period should be tuned to achieve near complete removal of easily biodegradable COD in the anaerobic period, and the lengthof the aerobic period should be long enough for complete nitrification. The total COD-loading rate must be at the same time be kept high enough to achieve a net growth of biomass in the reactor. [ABSTRACT FROM AUTHOR]

Research aimed at solving important environmental problems at all scales ranging from global to individual will continue to be an essential part of the process by which sustainability of life on earth may be achieved. Solutions to environmental problems that relate to water are especially critical to this process and are likely to involve useof innovative technologies that emerge from research with sufficientpromise to justify their development, a process that evaluates them at a scale that will yield engineering design parameters and confidence in their technical performance and economic value. Privatization of water and wastewater systems and mergers of equipment manufacturersmay provide the economic bases needed for development of innovative water and wastewater treatment technologies in the 21st Century that have emerged from research in the 19th and 20th Centuries but have not as yet been fully developed or adopted. [ABSTRACT FROM AUTHOR]

A separate sludge system incorporating sequencing batch reactor (SBR) for sequestered denitrification and an immobilized fixed-film reactor for nitrification was investigated in this study. Emphases were placed on the preservation of organic matter as an electron donor for denitrification and the improvement of nitrification efficiency by using an immobilization technique with alginate coating. To preserve organic materials in the sludge required for denitrification, a study was made with a contact process. The contactor, when operated with a short detention time, gave incomplete metabolism of organic matter. With 64% of the influent soluble chemical oxygen demand (SCOD) was adsorbed to activated sludge within 30 min. The specific mass of organic matter uptaken was 55 mg SCOD/g mixed liquor suspended solids (MLSS), which enhanced the denitrification efficiency up to 63% in the following denitrification step. Thus, the required COD in the proposed system can be saved up to 63% as an available electron donor for the conventional aerobic process. The immobilized nitrification unit showed over 90% of nitrate production rate up to 50 mg/l of influent ammonia load. [ABSTRACT FROM AUTHOR]

Ratio of total Kjeldahl Nitrogen to COD for ABS (acrylnitrile, butadiene and styrene) wastewater is in a range of 0.12-0.17, which is significantly higher than that needed for optimal growth of an activatedsludge. In this work, an automated Sequencing Batch Biofilm Reactor (SBBR) system at lab-scale is applied to reduce the amount of ABS; this system is controlled by an on-line monitoring of oxidation-reduction potential (ORP). A comparison of the operation efficiency for the lab-scale SBBR operated with the control of fix-time method and ORP-based real-time automatic method is presented. The results show that the system ORP can be used as an available parameter for achieving a real-time operation and control of the lab-scale SBBR. It is found that the reaction time is reduced of 11.1-55.2% if an ORP-based real-time control is used, instead of the fixed-time control. Also, the SBBR system is made more efficient and cost-effective. [ABSTRACT FROM AUTHOR]

Nitrification of ammonium-rich synthetic wastewater was studied in acontinuously operated rotating disc reactor (RDR) with additional aeration. For a wastewater with 500 mg L+1 NH4-N a nearly complete oxidation to nitrate could be demonstrated for a hydraulic residence time of 27 h (HRT). The reactor was nearly completely mixed. Nevertheless, the biofilm covering the first discs was remarkably thicker than that of the last discs. In order to study the bioactivity of selected discs, single-disc reactors were used. The determined ammonium oxidation rate was nearly independent of the thicknessand location of the disc. In contrast, the nitrite oxidation rate increased from the first to the last discs. Some results from experiments on nitrogen removal in sequencing batch single-disc reactors (SBSDR) are discussed. The SBSDR was operated with 2 phases, a partially submerged phase for nitrification and a completely submerged anoxic phase in which acetate was added for denitrification. It was advantageous to operate without additional aeration and thus produce more nitrite and saving carbon and energy. First results of the treatment of a synthetic wastewater with a C:N ratio of 1 in a 5-phase SBBR process providing 2 nitrification, 2 anoxic and a final aerobic post-treatment phase showed average specific rates. [ABSTRACT FROM AUTHOR]

Most industrial processes and environmental remediation activities generate large volumes of air contaminated with volatile organic compounds (VOCs). In conventional biofilter operation, gaseous emissions contaminated with low concentrations of biodegradable VOCs are remediated by being passed continuously through packed beds. This paper describes how periodically operated biofilters can be designed as controlled, unsteady-state systems that destroy gas-phase contaminants. Periodic operation, previously limited to applications in wastewater treatment and soil remediation, increases an operator's ability to control the spatial distribution, physiological state, and 'robustness' of the microbial communities established within a biofilter while minimizing uncertainties that often accompany design and operation of biological systems. Results are presented from toluene degrading biofilters that used a novel polyurethane foam packing medium. These studies demonstrate how controlled periodic operations can enhance contaminantremoval during transient periods of elevated contaminant load. [ABSTRACT FROM AUTHOR]

In order to give detailed information about the local flow field in a bioreactor a numerical method has been developed. This method givesinformation about the velocity, pressure and temperature in each point of the reactor, avoiding the problems caused by placing measurement instruments inside. Comparisons of experiments and numerical results show good agreement. The functionality and physical fundamentals ofthis tool are described. This is followed by explaining a reasonableapplication of the numerical code in the field of biological reactors. The reactors considered are filled with polydisperse, spherical support particles. From the results of the simulation a detailed picture of a reactor's fluid mechanical behaviour is drawn. This includes the quantification of mechanical stresses on the biofilm surface as well as information about the inflow, outflow and channelling behaviourof a reactor. Furthermore the effect of polydisperse support carriesin discussed. [ABSTRACT FROM AUTHOR]

Research activities carried out at ENEA during the last few years allowed the development of a Sequencing Batch Reactor (SBR) that is able to remove biologically organic waste, nitrogen and phosphorus and that was shown to be particularly suited to obtaining low effluent nutrient concentrations even starting from concentrated wastes. Researchon optimisation of time cycles and on process modelling, allowed an advanced comprehension of reactor behaviour and the development of a process able to obtain more than 98% removal of nitrogen, phosphorus and COD, and therefore almost capable of matching effluent standards with a sole biological process. On the basis of laboratory results and process modelling, a full scale SBR plant has been designed and realised. This plant, in ten months of operation, is achieving even better results compared to the laboratory ones. (C) 1999 IAWQ Published by Elsevier Science. All rights reserved. [ABSTRACT FROM AUTHOR]

The driving force for Enhanced Biological Phosphorus Removal (EBPR) is the presence of an anaerobic zone that enriches the activated sludge for P-accumulating microorganisms (PAOs). According to accepted models, PAOs anaerobically store volatile fatty acids (VFAs) as polyhydroxyalkanoates (PHAs) utilising polyphosphate hydrolysis as the energy source. For substrates other than VFAs, one hypothesis is that other heterotrophs convert them to VFAs, so acting in favour of PAOs. However, particular glycogen accumulating microorganisms have been described (GAOs), that compete against PAOs being able to store anaerobically many substrates into PHAs, by transforming intracellular carbohydrates (glycogen) into PHAs, as the energy source. In this perspective, the paper presents a summary (with new findings) of a long experimental work to study EBPR processes with a lab-scale Sequencing Batch Reactor fed with different organic, substrates (peptone, glucose and acetate, separate or in mixtures). Our results show that EBPR can be obtained with substrates other than VFAs with neither their pre-conversion to VFAs nor their storage as PHA. Moreover, in different periodsanaerobic uptake of glucose was possible with and without EBPR. In both cases, the stored polymer was glycogen while the energy source was either polyphosphate hydrolysis or lactic fermentation, respectively. These results are not consistent with the reported behaviour of PAOs or GAOs, so showing that many different mechanisms of anaerobic uptake and storage of substrates can act in favour of, or against EBPR.Deeper insight on these mechanisms is needed to improve design and operation of EBPR plants. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved. [ABSTRACT FROM AUTHOR]

Experiments have been performed to gain an understanding of the conditions and processes governing the occurrence of SND in activated sludge systems. Sequencing batch reactors (SBRs) have been operated under controlled conditions using the wastewater from the first anaerobicpond in an abattoir wastewater treatment plant. Under specific circumstances, up to 95% of total nitrogen removal through SND has been found in the system. Carbon source and oxygen concentrations were foundto be important process parameters. The addition of acetate as an external carbon source resulted in a significant increase of SND activity in the system. Stepwise change of DO concentration has also been observed in this study. Experiments to determine the effect of the floc size on SND have been performed in order to test the hypothesis that SND is a physical phenomenon, governed by the diffusion of oxygen into the activated sludge flocs. Initial results support this hypothesis but further experimental confirmation is still required. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved. [ABSTRACT FROM AUTHOR]

A sequencing batch reactor (SBR) was operated to selectively grow a nitrite oxidising microbial community and was called the nitrite oxidising SBR (NOSBR). The nitrite oxidising characteristics of the reactor biomass were studied as well as the microbial composition. Molecular biological methods of clone libraries were used to evaluate the microorganisms in both the seed sludge and in the NOSBR sludge. We havefound that the nitrite oxidation in the NOSBR was due the presence of bacteria from the Nitrospira phylum and not because of the presenceof Nitrobacter which were in very low numbers in the NOSBR and not detected in the seed sludge. We hypothesize that the unknown nitrite oxidising bacteria in wastewater treatment plants are a range of species related to Nitrospira moscoviensis. A suite of primers were developed from the clone sequence data and used in a diagnostic polymerase chain reaction to prove the presence of these novel nitrite oxidisersin a range of full scale and laboratory scale activated sludge plants. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved. [ABSTRACT FROM AUTHOR]

Many waste water treatment plants in Sweden have been using pre-precipitation, which has considerably decreased the load on the existing activated sludge process. In many cases it has been possible to introduce pre-denitrification, with minor changes or increase of volume, in order to reach the required effluent values, which in Sweden variesbetween 10 and 15 mg Ntot/l as annual average value. In treatment plants with anaerobic digestion of sludge, some 15- -20% of the nitrogen load is recirculated with the return liquors from dewatering. Separate treatment of ammonia-rich return liquors has successfully been using SBR-technique for nitrogen removal, adding external carbon source, e.g. methanol or ethanol. The overall result is, however, not sufficient to meet the requirement without additional action. The use of SBR-reactors, designed for nitrification/denitrification ofreturn liquors from dewatering of digested sludge, and part of the influent raw waste water, 20--30%, as a carbon source, has been provenmost cost-effective, both from investment and operation cost point of view. The result is a considerably decreased load on the existing biological stage, making it possible to introduce pre-denitrification without any extension of reaction volumes. The paper presents the result from full-scale operation of some plants in Sweden. (c) 1998 1AWQ. Published by Elsevier Science Ltd. [ABSTRACT FROM AUTHOR]

A new strategy based on respirometry for the control of the anaerobic period duration of an SBR bio-P process with a rapid-fill mode of operation was developed. Samples were withdrawn every 15 minutes from a lab-scale SBR during the anaerobic period and aerated intermittently in order to determine the respiration rate. The time of disappearance of the rapidly biodegradable substrate (acetate) was determined bythe fall observed in the respiration rate. It was shown that, respirometry can be used not only for the characterization and control of aerobic processes, but also for the control of the anaerobic period duration of an SBR bio-P process. ) 1997 IAWQ. Published by Elsevier Science Ltd. [ABSTRACT FROM AUTHOR]