Typically, microbes associated with biological wastewater treatment processes are subjected to dynamic organic and nutrient loading conditions. This constantly changing environment imposes a stress, referred to as "feast-famine" that selects for microbes capable of biologically storing substrates as polymers during high organic concentration periods (i.e., feast) for use during periods of low organic availability (i.e., famine). In this study, we monitored the production of biostorage polymers generated with actual cheese wastewater treatment by way of sequencing batch reactors (SBRs). SBRs were employed and operated in duplicate under two long (i.e., hours) filling scenarios (1) "react fill" with mixing/aeration and (2) "static fill" with no mixing/aeration. Despite comparable effluent water quality levels, the results reveal that a "static fill" approach outperforms a "react fill" with respect to maximum biostorage polymer production (50% more poly-beta-hydroxybutyrate, 15% more glycogen). The presence of biostorage polymer production has been shown to be indicative of a more stable and robust process.

Much research has asserted that high shear forces are necessary for the formation of aerobic granular sludge in Sequencing Batch Reactors (SBRs). In order to distinguish the role of shear and dissolved oxygen on granule formation, two separate experiments were conducted with three bench-scale SBRs. In the first experiment, an SBR was operated with five sequentially decreasing superficial upflow gas velocities ranging from 1.2 to 0.4 cm s(-1). When less than 1 cm s(-1) shear was applied to the reactor, aerobic granules disintegrated into flocs, with corresponding increases in SVI and effluent suspended solids. However, the dissolved oxygen also decreased from 8 mg L(-1) to 5 mg L(-1), affecting the Feast/Famine regime in the SBR and the substrate removal kinetics. A second experiment operated two SBRs with an identical shear force of 1.2 cm s(-1), but two dissolved oxygen concentrations. Even when supplied a high shear force, aerobic granules could not form at a dissolved oxygen less than 5 mg L(-1), with a Static Fill. These results indicate that the substrate removal kinetics and dissolved oxygen are more significant to granule formation than shear force.

ABSTRACT Extracellular polymeric substances (EPS) were quantified in flocculent and aerobic granular sludge developed in two sequencing batch reactors with the same shear force but different settling times. Several EPS extraction methods were compared to investigate how different methods affect EPS chemical characterization, and fluorescent stains were used to visualize EPS in intact samples and 20-μm cryosections. Reactor 1 (operated with a 10-min settle) enriched predominantly flocculent sludge with a sludge volume index (SVI) of 120 ± 12 ml g−1, and reactor 2 (2-min settle time) formed compact aerobic granules with an SVI of 50 ± 2 ml g−1. EPS extraction by using a cation-exchange resin showed that proteins were more dominant than polysaccharides in all samples, and the protein content was 50% more in granular EPS than flocculent EPS. NaOH and heat extraction produced a higher protein and polysaccharide content from cell lysis. In situ EPS staining of granules showed that cells and polysaccharides were localized to the outer edge of granules, whereas the center was comprised mostly of proteins. These observations confirm the chemical extraction data and indicate that granule formation and stability are dependent on a noncellular, protein core. The comparison of EPS methods explains how significant cell lysis and contamination by dead biomass leads to different and opposing conclusions.

Aerobic granular sludge, without the addition of carrier material, has only been reported in one suspended growth system, the Sequencing Batch Reactor (SBR) operated with short fill and settling periods. Recent studies have demonstrated that extracellular polysaccharides increased with the formation of aerobic granules, and that the shear force may stimulate production of these polysaccharides. In the study described herein, two SBRs were operated with the same shear force (air flow rate 275 Lh(-1)) and two different settling times (2 and 10 min). Only the reactor with 2 min settling formed completely granular sludge, although granules were present in both reactors. Community analysis using 16S rRNA PCR products and DGGE showed that the communities diverged quickly after reactor start-up. For samples taken at steady-state, the granular population was more stable and less diverse than the flocculent reactor. EPS extraction of samples using cation exchange resin yielded similar values for aerobic granular sludge and previously reported anaerobic granules. While differences in the protein and TOC content between the flocculent and granular reactors increased appreciably as the sludge became more granular, the protein to polysaccharide ratio was relatively constant. The experiment confirmed previous theories that short, settling times in SBRs select-for granular sludge. The settling time results in granular sludge having a higher EPS protein content and a less diverse but more stable population.

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 x 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.

Characterization of organaic matter in US ball clay exhibiting the 'natural formation' profile utilizing pyrolysis-GC/MS: Trends between PCDD homologue distributions and specific pyrolysis products

Aerobic granular sludge, without the addition of carrier material, has only been reported in one suspended growth system, the Sequencing Batch Reactor (SBR) operated with short fill and settling periods. Recent studies have demonstrated that extracellular polysaccharides increased with the formation of aerobic granules, and that the shear force may stimulate production of these polysaccharides. In the study described herein, two SBRs were operated with the same shear force (air flow rate 275 L h–1) and two different settling times (2 and 10 min). Only the reactor with 2 min settling formed completely granular sludge, although granules were present in both reactors. Community analysis using 16S rRNA PCR products and DGGE showed that the communities diverged quickly after reactor start-up. For samples taken at steady-state, the granular population was more stable and less diverse than the flocculent reactor. EPS extraction of samples using cation exchange resin yielded similar values for aerobic granular sludge and previously reported anaerobic granules. While differences in the protein and TOC content between the flocculent and granular reactors increased appreciably as the sludge became more granular, the protein to polysaccharide ratio was relatively constant. The experiment confirmed previous theories that short settling times in SBRs select for granular sludge. The settling time results in granular sludge having a higher EPS protein content and a less diverse but more stable population.

The US Army is pilot testing the neutralization of VX nerve agent stockpiled at Newport, Indiana using caustic hydrolysis in a Sequencing Batch Reactor (SBR). The resulting hydrolysate was tested at the bench-scale for treatment with activated sludge biodegradation in two distinct studies, one in the SBR and another, in the PACT process. The feed to both biological systems was pretreated to enhance the biodegradability of the hydrolysis products. Both biodegradation studies demonstrated that the hydrolysate could easily meet the Chemical Weapons Convention treaty and US environmental regulations following pretreatment.

The aim of the present study was to investigate how phenol modifies, through cometabolism, the biodegrading capability of 3-chlorophenol (3-CP) in a sequencing batch reactor seeded with a mixed culture obtained from a domestic sewage treatment plant. Two laboratory-scale SBRs, one fed 3-CP only and the other fed 3-CP and phenol in the same concentration, were seeded with the partially acclimated biomass. The removal capability in both reactors was measured for progressive increases in the feed organic loading. Cometabolism enhanced biodegradation of 3-CP by reducing both the initial lag period and the time required for the complete removal. 700 mg/L 3-CP was demonstrated to be the highest concentration, which could be completely degraded during the active phase (fill plus react) either in the presence or absence of phenol as the growth substrate even though the lag period was shorter when phenol was present. The operating strategy required modification for the complete removal of 800 mg/L 3-CP. An increase in the phenol to 3-CP ratio did, however, improve 3-CP degradation rate.

Aerobic granular sludge was successfully cultivated in a sequencing batch reactor (SBR) treating wastewater from the malting process with a high content of particulate organic matter. At an organic loading rate of 3.2 kg/(m 3 d) COD total and an influent particle concentration of 0.95 g/L MLSS an average removal of 50% in COD total and 80% in COD dissolved could be achieved. A comparison of granular and flocculent sludge grown under the same operating conditions showed no significant difference in removal efficiency although granules exhibited a higher metabolic activity in terms of specific oxygen uptake rate ( r O2, X ). Two distinct mechanisms of particle removal were observed for granular sludge: during initial granule formation, particles were incorporated into the biofilm matrix. For mature granules, a high level of protozoa growth on the granule surface accounted for the ability to remove particulate COD. Combined evaluation of the development in MLSS content and sludge bed settling rate (i.e., mean derivative of the normalized sludge volume) was found to be an adequate method for monitoring the characteristic settling properties of a granulizing sludge bed. By means of this method, a distinct substrate gradient out of several operating conditions was concluded to have the biggest impact on the formation of aerobic granular sludge.

In this study, we report the PCDD and mineralogical results from the analyses of 27 different samples from three ball clay cores from different locations in Kentucky and Tennessee. One goal of this study was to determine if there is a correlation between the mineralogy of the ball clay samples and the PCDD concentrations and/or homologue profiles in each sample. Samples from each of the three cores exhibited the natural formation profile with extremely high PCDD concentrations with low and mostly undetectable levels of polychlorinated dibenzofurans (PCDFs). The maximum toxic equivalents (TEQs) for Cores C-E were 2500, 440, and 15 000 pg WHO-TEQ/g, respectively. Although there does not seem to be a direct correlation between mineralogy and PCDD concentrations or homologue profiles the mineralogy of Core C is substantially different than that of Cores D and E,which may in part explain the differences in congener patterns we observed among the three cores.

AbstractBackgroundThe ConceptDesign and Operation of SBR PlantsSizing of SBRsExperiencesNovel Applications for Biofilm and Slurry Systems

The present paper shows the results obtained through a study on the biodegradation of 3-chlorophenol (3-CP) in a Sequencing Batch Reactor (SBR). To such a purpose a lab-scale SBR was fed a synthetic wastewater containing 3-CP and nutrients (nitrogen and phosphorus) diluted in tap water. The operating strategy, in terms of both the duration of either the cycle or the react phase, was changed throughout the experimental activity in order to find out the optimal one allowing to ensure constant and high removal efficiency despite the increasing 3-chlorophenol concentration in the feed. Biomass collected from a full-scale continuous flow activated sludge facility treating domestic wastewater was used as seed, after being acclimated to 3-CP by means of several batch tests. The results showed that a periodically operated activated sludge system can be successfully used for the biodegradation of chlorophenol compounds, after the needed members of the microbiological consortium are selected and enriched.

Introduction Studies have found elevated levels of polychlorinated dibenzo-p-dioxins (PCDDs) in ball clay and kaolin samples from specific regions in the United States and Germany 1, 2, . In general, the congener profiles associated with these clay samples include, increasing PCDD concentration with increasing chlorine substitution, and low or even undetectable levels of PCDFs at comparable detection limits. Moreover, 1,2,3,7,8,9-HxCDD dominates the 2,3,7,8-substituted HxCDD isomers. The congener patterns and the high ∑PCDDs/ ∑PCDFs ratio associated with these samples are unlike those from known anthropogenic sources, chemical products or environmental samples. The natural processes that produce the PCDDs observed in these clay samples are not yet understood.

In conventional biofilter operation, contaminated air is passed continuously through packed beds containing microbial consortia capable of contaminant biotransformation. This paper describes how biofilters can be designed and operated as controlled unsteady-state, periodic processes for the destruction of gas-phase contaminants. Such operation, previously limited to applications in wastewater treatment and soil remediation, increases an operator's ability to control the physiological state, "robustness," and spatial distribution of the microbial communities established within the biofilter and, thus, minimizes uncertainties that often accompany design and operation of biological systems. Results are presented from toluene degrading biofilters that used polyurethane foam packing medium. These studies demonstrate how controlled periodic operations can enhance contaminant removal during transient periods of elevated contaminant load.

Biological treatment of a silty clay loam with aged diesel fuel contamination was conducted in 8 L Soil Slurry-Sequencing Batch Reactors (SS-SBRs). The purpose was to monitor slurry conditions and evaluate reactor performance for varying solids concentration (5%, 25%, 40%, 50%), mixing speed(300 rpm, 700 rpm, 1200 rpm), retention time (8 d, 10 d, 20 d), and volume replaced per cycle (10%, 50%, 90%). Diesel fuel was measured in slurry and in filtered aqueous samples. Oxygen uptake rate (OUR) was monitored. Aggregate size was measured with sieve analyses. Biosurfactant production was quantified with surface tension measurements. Increasing solids concentration and decreasing mixing speed resulted in increased aggregate size, which in turn increased effluent diesel fuel concentrations. Diesel fuel removal was unaffected by retention time and volume replaced per cycle. Biosurfactant production occurred with all operating strategies. Foam thickness was related to surfactant concentration and mixing speed. OUR, surfactant concentration, and foam thickness increased with increasing diesel fuel added per cycle.

The literature reports conflicting observations regarding the need for nutrient addition to biofilters treating contaminated gases. Such conflicts are often based on quasi-steady-state performance data collected on biofilters operated under continuous loading conditions. In the studies described herein, the impact of nitrogen limitations on two toluene-fed biofilters was assessed over a 97-day period. The biofilters were packed with polyurethane foam medium and contained different initial levels of nitrate-nitrogen. Toluene and CO2 concentration profiles were monitored during both normal steady loading conditions and short-term, unsteady-state transient loading conditions (e.g., shock loads). Packing medium samples were periodically removed and analyzed to quantify changes in nitrate-nitrogen content over time. Data are presented which show that over long-time periods (several months), nutrient-induced kinetic limitations diminished biofilter performance during transient, unsteady-state conditions even when performance during normal steady loading was not adversely affected. Elemental analysis of biomass removed from the biofilters support nitrate-nitrogen and CO2 concentration profile data and clearly illustrate how kinetically limited biofilters fail during shock loads even when there is an overall stoichiometric excess of nutrients.