Kinetics of lactate,acetate and propionate in unadapted and lactate-adapted thermophilic,anaerobic sewage sludge: the influence of sludge adaptation for start-up of thermophilic UASB-reactors

Summary A thermophilic anaerobic sludge digestor was adapted to lactate metabolism. The adapted sludge showed an improved capacity for lactate degradation when tested by a batch activity test, compared to the performance of unadapted sludge. Acetate was the major intermediate produced during the degradation. When adapted sludge was used as the inoculum for a lactate-fed, upflow anaerobic sludge blanket (UASB) reactor, the chemical oxygen demand reduction rate was higher than with unadapted sludge. After 39 days, however, the difference vanished due to an extensive wash-out of sludge from the reactor inoculated with adapted sludge.Offprint requests to: B. K. Ahring     

Comparison of autochthonous bacteria and commercially available cultures with respect to their effectiveness in fuel oil degradation

Summary This study examined the microbial degradation of fuel oil by nine highly adapted different commercially available mixed bacterial cultures (DBC-plus, Flow Laboratories, Meckenheim, F.R.G.) and a bacterial community from a domestic sewage sludge sample. All mixed cultures were cultivated under aerobic batch conditions shaking (110 rpm) at 20°C in a mineral base medium containing 1 or 5% (v/v) fuel oil as the sole carbon source. Percent degradation of fuel oil and the n-alkane fraction was recorded for the nine DBC-plus cultures and the mixed population of the activated sludge sample. The increase in colony counts, protein, and optical density was studied during a 31-day incubation period for DBC-plus culture A, DBC-plus culture A2 and the activated sludge sample. The activated sludge mixed culture was most effective in degrading fuel oil, but various isolated bacterial strains from this bacterial community were not able to grow on fuel oil as the sole carbon source. In contrast, the n-alkane degradation rates of the DBC-cultures were lower, but single strains from the commercially available mixed cultures were able to mineralize fuel oil hydrocarbons. Strains ofPseudomonas aeruginosa were isolated most frequently and these organisms were able to grow very rapidly on fuel oil as a complex sole carbon source. The results indicate that fuel oil degradation in domestic sewage sludge is performed by mixed populations of naturally occurring bacteria and does not depend on the application of highly adapted commercially available cultures.     

Development of thermophilic methanogenic sludge in compartmentalized upflow reactors

The characteristics and development of thermophilic anaerobic sludge in upflow staged sludge bed (USSB) reactors were studied. The compartmentalized reactors were inoculated with partially crushed mesophilic granular sludge and then fed with either a mixture of volatile fatty acids (VFA) or a mixture of sucrose and VFA. The staged degradation of the soluble substrate in the various compartments led to a clear segregation of specific types of biomass along the height of the reactor, particularly in reactors fed with the sucrose-VFA mixture. Both the biological as well as the physical properties of the cultivated sludge were affected by the fraction of nonacidified substrate. The sludge in the first compartment of the reactor treating the sucrose-VFA mixture was whitish and fluffy, most likely resulting from the development of acidifying bacteria. Sludge granules which developed in the top part of this reactor possessed the highest acetogenic and methanogenic activity and the highest granule strength as well. The experiments also revealed that the conversion of the sucrose-VFA mixture into methane gradually deteriorated at prolonged operation at high organic loading rates (50 to 100 g COD . L(-1) . day(-1)). Stable long-term performance of a reactor can only be achieved by preserving the sludge segregation along the height of the reactor. In the reactor fed solely with the VFA mixture little formation of granular sludge occurred. In this reactor, large differences in sludge characteristics were also observed along the reactor height. Li(+)-tracer experiments indicated that the hydraulic regime in the USSB reactor is best characterized by a series of at least five completely mixed reactors. The formation of granular sludge was found to influence the liquid flow pattern. (c) 1996 John Wiley & Sons, Inc.     

Detection of anaerobic processes and microorganisms in immobilized activated sludge of a wastewater treatment plant with intense aeration

Attached activated sludge from the Krasnaya Polyana (Sochi) wastewater treatment plant was studied after the reconstruction by increased aeration and water recycle, as well as by the installation of a bristle carrier for activated sludge immobilization. The activated sludge biofilms developing under conditions of intense aeration were shown to contain both aerobic and anaerobic microorganisms. Activity of a strictly anaerobic methanogenic community was revealed, which degraded organic compounds to methane, further oxidized by aerobic methanotrophs. Volatile fatty acids, the intermediates of anaerobic degradation of complex organic compounds, were used by both aerobic and anaerobic microorganisms. Anaerobic oxidation of ammonium with nitrite (anammox) and the presence of obligate anammox bacteria were revealed in attached activated sludge biofilms. Simultaneous aerobic and anaerobic degradation of organic contaminants by attached activated sludge provides for high rates of water treatment, stability of the activated sludge under variable environmental conditions, and decreased excess sludge formation.     

Empirical model for the autotrophic biodegradation of thiocyanate in an activated sludge reactor

AIMS: The aim of this investigation was to develop an empirical model for the autotrophic biodegradation of thiocyanate using an activated sludge reactor. METHODS AND RESULTS: The methods used for this purpose included the use of a laboratory scale activated sludge reactor unit using thiocyante feed concentrations from 200 to 550 mg x l(-1). Reactor effluent concentrations of <1 mg x l(-1) thiocyanate were consistently achieved for the entire duration of the investigation at a hydraulic retention time of 8 h, solids (biomass) retention of 18 h and biomass (dry weight) concentrations ranging from 2 to 4 g x l(-1). A biomass specific degradation rate factor was used to relate thiocyanate degradation in the reactor to the prevailing biomass and thiocyanate feed concentrations. A maximum biomass specific degradation rate of 16 mg(-1) x g(-1) x h(-1) (mg thiocyanate consumed per gram biomass per hour) was achieved at a thiocyanate feed concentration of 550 mg x l(-1). The overall yield coefficient was found to be 0.086 (biomass dry weight produced per mass of thiocyanate consumed). CONCLUSION: Using the results generated by this investigation, an empirical model was developed, based on thiocyanate feed concentration and reactor biomass concentration, to calculate the required absolute hydraulic retention time at which a single-stage continuously stirred tank activated sludge reactor could be operated in order to achieve an effluent concentration of <1 mg x l(-1). The use of an empirical model rather than a mechanistic-based kinetic model was proposed due to the low prevailing thiocyanate concentrations in the reactor. SIGNIFICANCE AND IMPACT OF THE STUDY: These results represent the first empirical model, based on a comprehensive data set, that could be used for the design of thiocyanate-degrading activated sludge systems.     

Simultaneous removal of carbon and nitrate in an airlift bioreactor

This paper presents the integrated removal of carbon (measured as chemical oxygen demand i.e. COD) and NO(x)-N by sequentially adapted sludge, studied in an airlift reactor (ALR). Simultaneous removal of COD and nitrate occurs by denitrification (anoxic) and oxidation (aerobic). Aerobic (riser) and anoxic (remaining part) conditions prevail in different parts of the reactor. Studies were carried out in a 42 L ALR operated at low aeration rate to maintain anoxic and aerobic conditions as required for denitrification and COD removal, respectively. The sludge was adapted sequentially to increasing levels of NO(x)-N and COD over a period of 45 days. Nitrate removal efficiency of the sludge increased due to adaptation and degraded 900 ppm NO(3)-N completely in 2h (initially the sludge could not degrade 100 ppm NO(3)-N). The performance of the adapted sludge was tested for the degradation of synthetic waste with COD/N loadings in the range of 4-10. The reduction of COD was significantly faster in the presence of NO(x)-N and was attributed to the availability of oxygen from NO(x)-N and distinct conditions in the reactor. This hypothesis was justified by the material balance of COD.     

Biodegradation of Malathion with Indigenous Acclimated Activated Sludge in Batch Mode and in Continuous-Flow Packed-Bed Reactor

Acclimated activated sludge was examined for its ability to degrade malathion with and without the presence of glucose as a potential cometabolite substrate. In this study, a packed-bed reactor (PBR) using three kinds of biofilm carriers was employed for efficient degradation of malathion. The results obtained indicate that microorganisms tested were able to degrade malathion. The observed degradation rate of the pesticide in the presence of glucose was the same as without glucose. The activated sludge was found to be able to use malathion as the sole phosphorus source. In contrast, the degradation ability of the activated sludge was lost when the pesticide was used as the sole source of sulfur. The degradation capacity of the PBR was higher than the performance obtained with the batch reactor. The reactor packed with crushed olive kernels exhibited the best performance, allowing a total removal of malathion (10 mg/dm³) within 12 h.     

Biodegradation of nitrobenzene by a sequential anaerobic-aerobic process

Nitrobenzene was completely degraded by mixed cultures using a sequential anaerobic-aerobic treatment process. Under anaerobic conditions in a fixed-bed column aniline was formed from nitrobenzene through gratuitous reduction by cells of sewage sludge. This reaction was accelerated by the addition of glucose. Complete mineralization of aniline was accomplished by subsequent aerobic treatment using activated sludge as inoculum. The maximum degradation rate of nitrobenzene (4.5 mM) in the two-stage system was 552 mg l^–1d^–1, referring to 154 mg of nitrobenzene per gram of glucose. In a second experimental phase glucose as cosubstrate and H-donor was replaced by synthetic waste containing ethanol, methanol, isopropanol and acetone. Again, nitrobenzene (1.9 mM) was completely degraded (maximum degradation rate of 237 mg l^–d^–1, referring to 251 mg per gram of solvents). The major advantage of the described two-stage process is that the reduction of nitrobenzene by anaerobic pretreatment drastically reduces emission by stripping during aerobic treatment.Abbreviations HRT hydraulic retention time - OD₅₄₆ optical density at 546 nm     

Effect of activated carbon on the biological treatment of oil-water emulsions

Waste water, derived from the reprocessing of used emulsions or suspensions, contains high concentrations of emulsified mineral oil and stabilizers, as well as different additives that are needed during the treatment process. Two stirred-tank reactors and two fixed-bed reactors were used to study the biodegradation of these waste-water compounds during two-stage biological treatment. The waste water was first proceesed in an activated sludge reactor to remove easily biodegradable substances. The effluent from the first stage was treated in three parallel operating reactors: an activated sludge tank containing different amounts of powdered activated carbon (PAC, between 0 and 2%), an upflow anaerobic fixed-bed reactor and an aerobic fixed-bed reactor (trickling filter). The results from the continuous treatment were compared with laboratory batch experiments. About 60% of the influent TOC was reduced by the first activated sludge treatment. The removal efficiency increased to about 70% by using a second activated sludge stage. This degradation was comparable to the maximum degree of degradation measured in laboratory batch experiments. PAC addition to the second activated sludge tank resulted in increased degradation rates. The removal efficiency increased to about 76% when 0.1% PAC was added and to 96% with 1% PAC. The removal efficiency decreased to 84% when the proportion of PAC was further increased to 2%. Variations in the amount of PAC addition per unit influent volume in the range of 50 and 200 mg/l had no significant effect on the TOC removal. Degradation models based on the MONOD-type equation were found to be in close correlation with the results obtained from batch experiments. However, the biological removal rates measured in batch experiments did not reflect the removal capacity determined in continuous operating treatment systems.     

Anaerobic degradation of acetone and higher ketones via carboxylation by newly isolated denitrifying bacteria

Five strains of Gram-negative denitrifying bacteria that used various ketones as sole carbon and energy sources were isolated from activated sludge from a municipal sewage plant. Three strains are related to the genus Pseudomonas; two non-motile species have not yet been affiliated. All strains grew well with ketones and fatty acids (C2 to C7), but sugars were seldom utilized. The physiology of anaerobic acetone degradation was studied with strain BunN, which was originally enriched with butanone. Bicarbonate was essential for growth with acetone under anaerobic and aerobic conditions, but not if acetate or 3-hydroxybutyrate were used as substrates. An apparent Ks value of 5.6 mM-bicarbonate was determined for growth with acetone in batch culture. The molar growth yield was 24.8-29.8 g dry cell matter (mol acetone consumed)-1, with nitrate as the electron acceptor in batch culture; it varied slightly with the extent of poly-beta-hydroxybutyric acid (PHB) formation. During growth with acetone, 14CO2 was incorporated mainly into the C-1 atom of the monomers of the storage polymer PHB. With 3-hydroxybutyrate as substrate, 14CO2 incorporation into PHB was negligible. The results provide evidence that acetone is channelled into the intermediary metabolism of this strain via carboxylation to acetoacetate.     

Treatment of saline municipal wastewater using hybrid growth system

Background

In this study, a hybrid treatment system (Fluidized Bed positioned in a biological reactor of an Activated Sludge process) was used to treat saline domestic wastewater. The performance of the mentioned hybrid system was compared with the conventional activated sludge. A pilot study was conducted, and Chemical Oxygen Demand (COD), Electrical Conductivity (EC), Total Dissolved Solids (TDS) and pH were measured to investigate treatment efficiency. Three saline wastewater samples with salt concentrations of 0.5, 1, and 1.5 % and detention times of 2, 4 and 6 h were loaded into both rectors of hybrid system and activated sludge.

Results

The results showed that Chemical Oxygen Demand (COD) removals at salt concentrations of 0.5, 1, 1.5 % were equal to 80, 71, 48.5 for the hybrid system and 62, 47.7, 26.5 for the activated sludge system respectively. Likewise, similar results obtained for other contamination indices indicating the superiority of the hybrid system in comparison to activated sludge system. Moreover, another advantage of the hybrid system was that the activated sludge needed sludge returning while sludge returning was not required in the hybrid system. In addition, by loading fixed rate of air into both systems, dissolved oxygen concentration in the hybrid reactor is higher than the conventional reactor.

Conclusions

Therefore, the hybrid system had a significantly higher efficiency than conventional reactor to treat saline domestic wastewater.

     

Fermentation equations for propionic-acid bacteria and production of assorted oxychemicals from various sugars

Fermentation (stoichiometric) equations are derived for anaerobic fermentations of propionic-acid bacteria (of both the Propionibacterium and acrylate pathways) and for production of various oxychemicals (butanol, acetone, isopropanol, butanediol, butyrate, acetate, propionate, succinate, lactate, and acrylate) from pentoses, hexoses, and cellobiose. The derivations of the equations are based on the fermentation biochemistries of the various bacterial classes. The validity of the equations is tested using fermentation data from the literature. The equations are shown to be valuable, among other uses, for calculating maximal yields and selectivities of the various fermentation products, as "gateway sensors" for monitoring of the fermentations, and for calculating the extents of the various intracellular reactions of the fermentation biochemistry.     

The performance and microbial communities of biodegradation-electron transfer with sulfur metabolism integrated process for flue gas desulfurization wastewater treatment

The biodegradation-electron transfer with sulfur metabolism integrated (BESI®) process was used for the treatment of real flue gas desulfurization wastewater. The BESI® process consists of an anaerobic activated sludge reactor, an anoxic activated sludge reactor, and an aerobic bio-film reactor. The performance of the integrated process was evaluated by the removal efficiencies of organics and nitrogen pollutants. The sulfate in the wastewater was used as an abundant sulfur source to drive the integrated process. The removal efficiencies of chemical oxygen demand, total organic carbon, ammonia nitrogen, and total nitrogen of the integrated process were 87.99, 87.04, 30.77, and 45.17%, respectively. High-throughput 454-pyrosequencing was applied for the analysis of microbial communities in the integrated process. From the anaerobic activated sludge (Sample 1), anoxic activated sludge (Sample 2), and aerobic bio-film (Sample 3), totals of 1701, 1181, and 857 operational taxonomic units were obtained, respectively. The sulfur cycle was associated with the removal of organics and nitrogen pollutants. The sulfate-reducing bacteria participated in the organics removal in the anaerobic reactor, and the sulfide oxidation was related with the denitrification in the anoxic reactor. A complete nitrogen degradation chain was built in the integrated process. Through the degradation chain, the nitrogenous organic pollutants, ammonia nitrogen, and nitrate could be removed. The participant functional bacteria were also detected by pyrosequencing.     

Polyphasic approaches to the identification of predominant polyphosphate-accumulating organisms in a laboratory-scale anaerobic/aerobic activated sludge system

By combination of denaturing gradient gel electrophoresis of PCR-amplified 16S rDNA (PCR-DGGE), quinone profiling, and 16S rRNA-targeted fluorescence in situ hybridization (FISH), a polyphosphate-accumulating organism (PAO) responsible for phosphate (P)-removal was identified in activated sludge with high P-removal ability from a laboratory-scale anaerobic/aerobic continuous flow reactor. The DNA fragment from the most dense band on the DGGE gel was closely related to that of 'Candidatus Accumulibacter phosphatis' (beta-Proteobacteria). Quinone profiling also suggested the predominance of beta-Proteobacteria. FISH with a specific oligonucleotide probe designed for the sequence showed that the targeted bacterium was dominant in the activated sludge, and the accumulation and consumption of polyphosphate were observed by dual staining with 4',6-diamidino-2-phenylindole. The bacterium was concluded to be the responsible PAO in the reactor. However, when the P-removal ability per cell slightly decreased, the dominance of the PAO greatly diminished in the activated sludge. Such sludge might be dominated by other types of PAOs.     

The oxidation of α-olefins by aPseudomonas reactions involving the double bond

The preponderant pathway of octene-1 degradation by octane- and octene-1-grownPseudomonas aeruginosa cells (strain 473) starts with oxidation of the methyl group.In addition, with both types of cells minor reactions occur that involve the double bond. The formation of a 1,2-epoxide was reported earlier. In addition, the identification of the saturated C₈ fatty acid is a strong indication that the terminal methylene group is partially converted into an aldehydic group. The aldehyde seems to be formed beside the epoxide and the latter is not an intermediate. Enzymatic dihydroxylation of the double bond, if at all occurring, is masked by non-enzymatic hydrolysis of the epoxide.The formation of a saturated methyl ketone could not be detected. Nor is the olefinic group converted into a primary or secondary alcohol group under conditions which result in accumulation of octanol-1 from octane and of 7-octenol-1 from octene-1.The absence of a saturated alcohol among the intermediates in octene-1 degradation excludes hydration of the double bond as well as other mechanisms leading to saturated alcohols.Accumulation of C₈ fatty acids was effected by inhibition of -oxidation with acrylate, whereas addition of a competing alcohol substrate (octanediol-1,8) yielded detectable amounts of the alcoholic intermediates.     

Adaptation of a freshwater anammox population to high salinity wastewater

For the successful application of anaerobic ammonium oxidation (anammox) in wastewater practice it is important to know how to seed new anammox reactors with biomass from existing reactors. In this study, a new high salinity anammox reactor was inoculated with biomass from a freshwater system. The changes in activity and population shifts were monitored. It was shown that freshwater anammox bacteria could adapt to salt concentrations as high as 30 gl(-1) provided the salt concentration was gradually increased. Higher salt concentrations reversibly inhibited anammox bacteria. The nitrogen removal efficiency and maximum anammox activity of the salt adapted sludge was very similar to the reference freshwater sludge. Fluorescence in situ hybridization analysis revealed that the freshwater anammox species Candidatus "Kuenenia stuttgartiensis" was the dominant in both salt adapted sludge and freshwater sludge. These results show that gradual adaptation may be the key to successful seeding of anammox bioreactors.     

Development of mechanistically based model for simulating soluble microbial products generation in an aerated/non-aerated SBR

Soluble microbial products (SMPs) are considered as the main organic components in wastewater treatment plant effluent from biological wastewater treatment systems. To investigate and explore SMP metabolism pathway for further treatment and control, two innovative mechanistically based activated sludge models were developed by extension of activated sludge model no.3 (ASM3). One was the model by combining SMP formation and degradation (ASM3-SMP model) processes with ASM3, and the other by combining both SMP and simultaneous substrate storage and growth (SSSG) mechanisms with ASM3 (SSSG-ASM3-SMP model). The detailed schematic modification and process supplements were introduced for comprehensively understanding all the mechanisms involved in the activated sludge process. The evaluations of these two models were demonstrated by a laboratory-scale sequencing batch reactor (SBR) operated under aerated/non-aerated conditions. The simulated and measured results indicated that SMP comprised about 83% of total soluble chemical oxygen demand (SCOD) in which biomass-associated products (BAPs) were predominant compared with utilization-associated products (UAPs). It also elucidated that there should be a minimum SMP value as the reactive time increases continuously and this conclusion could be used to optimize effluent SCOD in activated sludge processes. The comparative results among ASM3, ASM3-SMP and SSSG-ASM3-SMP models and the experimental measurements (SCOD, ammonia and nitrate nitrogen) showed clearly the best agreement with SSSG-ASM3-SMP simulation values (R = 0.993), strongly suggesting that both SMP formation and degradation and SSSG mechanisms are necessary in biologically activated sludge modeling for municipal wastewater treatment.     

Scanning electron microscopy of biofilm development in anaerobic fixed-bed reactors: Influence of the inoculum

Summary Scanning electron microscopy was applied to evaluate the influence of inoculum on efficiency of initial biofilm formation and reactor performance. Five anaerobic fixed-bed reactors were inoculated with anaerobic sludges from different sources and operated in parallel under identical conditions with defined wastewater and acetate, propionate and butyrate as constituents In all sludges Methanothrix sp. was the predominant acetotroph. The reactors inoculated with anaerobic sludge adapted to the wastewater achieved the highest space loading with 21.0 g COD/l·d after 58 days. The inoculation with granular sludge from an upflow anaerobic sludge blanket (UASB) reactor resulted in significantly less reactor efficiency. Time course of biofilm formation and biofilm thickness (ranging from 20–200 m) depended on the type of inoculum.     

Bacteriological composition and structure of granular sludge adapted to different substrates

The bacteriological composition and ultrastructure of mesophilic granular methanogenic sludge from a large-scale Upflow Anaerobic Sludge Blanket reactor treating wastewater from a sugar plant and of sludge granules adapted to ethanol and propionate were studied by counting different bacterial groups and by immunocytochemical methods. Propionate-grown granular sludge consisted of two types of clusters, those of a rod-shaped bacterium immunologically related to Methanothrix soehngenii and those consisting of two different types of bacteria with a specific spatial orientation. One of these bacteria reacted with antiserum against Methanobrevibacter arboriphilus AZ, whereas the other is most likely a propionate-oxidizing bacterium immunologically unrelated to Syntrophobacter wolinii. Sludge granules obtained from the large-scale Upflow Anaerobic Sludge Blanket reactor and granules cultivated on ethanol did not show the typical spatial orientation of bacteria. Examination of the bacterial composition of the three types of granules by light and electron microscopy, the most-probable-number method, and by isolations showed that M. arboriphilus and M. soehngenii were the most abundant hydrogenotrophic and acetoclastic methanogens in propionate-grown sludge. Methanospirillum hungatei and Methanosarcina barkeri predominated in ethanol-grown granules, whereas many morphotypes of methanogens were abundant in granules from the full-scale reactor.     

Bacteriological composition and structure of granular sludge adapted to different substrates.

The bacteriological composition and ultrastructure of mesophilic granular methanogenic sludge from a large-scale Upflow Anaerobic Sludge Blanket reactor treating wastewater from a sugar plant and of sludge granules adapted to ethanol and propionate were studied by counting different bacterial groups and by immunocytochemical methods. Propionate-grown granular sludge consisted of two types of clusters, those of a rod-shaped bacterium immunologically related to Methanothrix soehngenii and those consisting of two different types of bacteria with a specific spatial orientation. One of these bacteria reacted with antiserum against Methanobrevibacter arboriphilus AZ, whereas the other is most likely a propionate-oxidizing bacterium immunologically unrelated to Syntrophobacter wolinii. Sludge granules obtained from the large-scale Upflow Anaerobic Sludge Blanket reactor and granules cultivated on ethanol did not show the typical spatial orientation of bacteria. Examination of the bacterial composition of the three types of granules by light and electron microscopy, the most-probable-number method, and by isolations showed that M. arboriphilus and M. soehngenii were the most abundant hydrogenotrophic and acetoclastic methanogens in propionate-grown sludge. Methanospirillum hungatei and Methanosarcina barkeri predominated in ethanol-grown granules, whereas many morphotypes of methanogens were abundant in granules from the full-scale reactor.