General method for determining anaerobic biodegradation potential

Long-term, high-rate anaerobic biological treatment of whey wastewaters at psychrophilic temperatures

Two laboratory-scale anaerobic hybrid reactors, R1 and R2, treated low- (1 kg COD m-3) and high-strength (10 kg COD m-3) whey-based wastewaters, respectively, in a 500-day trial. The chemical oxygen demand (COD) removal efficiencies of R1 averaged 70-80%, at organic loading rates of 0.5-1.3 kg COD m-3 day-1, between 20 and 12 degrees C. The COD removal efficiencies of R2 exceeded 90%, at organic loading rates up to 13.3 kg COD m-3 day-1, between 20 and 14 degrees C. Lowering the operating temperature of R2 to 12 degrees C resulted in a decrease in COD removal efficiency, to between 50% and 60%, and a disintegration of granular sludge. The decline in performance, and granule disintegration, was reversed by decreasing the organic loading rate of R2 to 6.6 kg m-3 day-1. Specific methanogenic activity profiles revealed mesophilic (37 degrees C) temperature optima for biomass in both reactors, even after 500 days of psychrophilic operation, although the development of psychrotolerance in the biomass was noted.

The effect of varying levels of sodium bicarbonate on polychlorinated biphenyl dechlorination in Hudson River sediment cultures

The addition of different concentrations of sodium bicarbonate had a profound effect on 2,3,4,5-chlorobiphenyl (2,3,4,5-CB) dechlorination in Hudson River sediment cultures. The most extensive dechlorination was observed in cultures to which 100 mg l(-1) bicarbonate was added. Cultures amended with 1000 mg l(-1) bicarbonate had the least extensive dechlorination, with 2,4-CB and 2,5-CB as predominant end-products. A significant loss of total chlorinated biphenyl mass was observed in cultures to which < or = 500 mg l(-1) bicarbonate was added, suggesting that degradation beyond chlorinated biphenyls occurred. The dynamics of acetate formation were different among the treatments, with high acetate concentrations detected throughout the 303-day experiment in cultures to which 1000 mg l(-1) bicarbonate had been added. Sodium bicarbonate addition also had a significant impact on bacterial community structure as detected by polymerase chain reaction-denaturant gradient gel electrophoresis (PCR-DGGE) of 16S rRNA gene fragments. Three putative polychlorinated biphenyl (PCB) dechlorinators were identified; one Dehalococcoides-like population was detected in all enrichment cultures, whereas two Dehalobacter-like populations were only detected in the enrichment cultures with the most extensive dechlorination. These results suggest that the availability of bicarbonate, and potentially sodium, may affect PCB dechlorination in Hudson River sediment and thus need to be taken into consideration when assessing the fate of PCBs or implementing bioremediation.

The effect of varying levels of sodium bicarbonate on polychlorinated biphenyl dechlorination in Hudson River sediment cultures

The addition of different concentrations of sodium bicarbonate had a profound effect on 2,3,4,5-chlorobiphenyl (2,3,4,5-CB) dechlorination in Hudson River sediment cultures. The most extensive dechlorination was observed in cultures to which 100 mg l(-1) bicarbonate was added. Cultures amended with 1000 mg l(-1) bicarbonate had the least extensive dechlorination, with 2,4-CB and 2,5-CB as predominant end-products. A significant loss of total chlorinated biphenyl mass was observed in cultures to which < or = 500 mg l(-1) bicarbonate was added, suggesting that degradation beyond chlorinated biphenyls occurred. The dynamics of acetate formation were different among the treatments, with high acetate concentrations detected throughout the 303-day experiment in cultures to which 1000 mg l(-1) bicarbonate had been added. Sodium bicarbonate addition also had a significant impact on bacterial community structure as detected by polymerase chain reaction-denaturant gradient gel electrophoresis (PCR-DGGE) of 16S rRNA gene fragments. Three putative polychlorinated biphenyl (PCB) dechlorinators were identified; one Dehalococcoides-like population was detected in all enrichment cultures, whereas two Dehalobacter-like populations were only detected in the enrichment cultures with the most extensive dechlorination. These results suggest that the availability of bicarbonate, and potentially sodium, may affect PCB dechlorination in Hudson River sediment and thus need to be taken into consideration when assessing the fate of PCBs or implementing bioremediation.

Kinetics of phenol degradation in an anaerobic fixed-biofilm process

A mathematical model was developed to describe phenol degradation in an anaerobic fixed-biofilm process. The model incorporates the mechanisms of diffusive mass transport and Monod kinetics. The model was solved using a combination of the orthogonal collocation method and Gear's method. A pilot-scale column reactor was used to verify the model. Batch kinetic tests were conducted independently to determine the biokinetic parameters used in the model, while shear loss and initial thickness of biofilm were assumed so that the model simulated the substrate concentration results well. The removal efficiency for phenol was approximately 98.5% at a steady-state condition. The model accurately described the effluent substrate concentrations and the sequence of biodegradation in the reactor. The model simulations are in agreement with the experimental results. The approaches presented in this paper could be used to design fullscale anaerobic fixed-biofilm reactor systems for the biodegradation of phenolic substrates.

Isolation and characterization of a Geobacillus thermoleovorans strain from an ultra-deep South African gold mine

A thermophilic facultative bacterial isolate was recovered from 3.2km depth in a gold mine in South Africa. This isolate, designated GE-7, was cultivated from pH 8.0, 50 degrees C water from a dripping fracture near the top of an exploration tunnel. GE-7 grows optimally at 65 degrees C and pH 6.5 on a wide range of carbon substrates including cellobiose, hydrocarbons and lactate. In addition to O(2), GE-7 also utilizes nitrate as an electron acceptor. GE-7 is a long rod-shaped bacterium (4-6microm longx0.5microm wide) with terminal endospores and flagella. Phylogenetic analysis of GE-7 16S rDNA sequence revealed high sequence similarity with G. thermoleovorans DSM 5366(T) (99.6%), however, certain phenotypic characteristics of GE-7 were distinct from this and other previously described strains of G. thermoleovorans.

Growth kinetics and competition between Methanosarcina and Methanosaeta in mesophilic anaerobic digestion

Methanosarcina species with a high maximum specific growth rate (mumax) and high half-saturation coefficient (KS) and Methanosaeta species with a low mumax and low KS are the only known aceticlastic methanogens. Because of Methanosaeta's low KS, the low acetate concentrations in conventional, mesophilic anaerobic digestion yield Methanosaeta dominance. However, Methanosarcina absorbs increases in acetate more efficiently and thus promotes more stable digestion. This paper tests the hypothesis that decreasing digester feeding frequencies can increase Methanosarcina predominance. Two acetate-fed reactors were established at a 17-day solids retention time. One reactor was fed hourly, and one was fed once daily. Microscopic and molecular methods were used to verify that the hourly fed reactor enriched for Methanosaeta, while the daily fed reactor enriched for Methanosarcina. Growth and substrate-use kinetics were measured for each reactor. A digester overload condition was simulated, and the Methanosarcina-enriched reactor was found to perform better than the Methanosaeta-enriched reactor. These findings indicate that Methanosarcina dominance can be achieved with infrequent feedings, leading to more stable digestion.

Degradation of aroclor 1242 dechlorination products in sediments by Burkholderia xenovorans LB400(ohb) and Rhodococcus sp. strain RHA1(fcb)

Burkholderia xenovorans strain LB400, which possesses the biphenyl pathway, was engineered to contain the oxygenolytic ortho dehalogenation (ohb) operon, allowing it to grow on 2-chlorobenzoate and to completely mineralize 2-chlorobiphenyl. A two-stage anaerobic/aerobic biotreatment process for Aroclor 1242-contaminated sediment was simulated, and the degradation activities and genetic stabilities of LB400(ohb) and the previously constructed strain RHA1(fcb), capable of growth on 4-chlorobenzoate, were monitored during the aerobic phase. The population dynamics of both strains were also followed by selective plating and real-time PCR, with comparable results; populations of both recombinants increased in the contaminated sediment. Inoculation at different cell densities (10(4) or 10(6) cells g(-1) sediment) did not affect the extent of polychlorinated biphenyl (PCB) biodegradation. After 30 days, PCB removal rates for high and low inoculation densities were 57% and 54%, respectively, during the aerobic phase.

Development of microbial community structure and actvity in a high-rate anaerobic bioreactor at 18 degrees C

Anaerobic digestion in the psychrophilic (< 20 degrees C) or sub-mesophilic temperature range has recently been proven as an effective treatment option for the mineralization of a wide variety of problematic wastewaters. In this study, an expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactor was seeded with a full-scale, mesophilic sludge and employed to evaluate the long-term operational potential, and underlying microbial ecology, of this approach for the treatment of a medium-strength (5 g chemical oxygen demand [COD] l(-1)), synthetic, volatile fatty acid-based wastewater. Throughout the trial period of 625 days, extended intervals of consistently stable and efficient wastewater treatment were sustained. These results were highlighted by a short start-up period (21 d), low hydraulic retention times (4.88h), high organic (up to 24.64kg CODm(-3)d(-1)), and volumetric loading rates (up to 4.92 m3 m(-3) d(-1)). A stable, well-settling granular sludge bed was maintained in the bioreactor for the majority of the trial; however, reduced treatment efficiency and biomass washout were observed at an imposed OLR of 36.96 kg COD m(-3) d(-1). The microbial biomass in the bioreactor was investigated using maximum specific methanogenic activity assays and polymerase chain reaction-denaturing gradient gel electrophoresis. A temporal succession of both the bacterial and archaeal populations was noted during the trial, compared to the seed sludge, in response to bioreactor operation at lower temperatures, loading rate increases and to VFA accumulation in the bioreactor. During the trial, an increased contribution of hydrogenotrophic methanogenesis as a pathway of methane production was observed, along with the overall emergence of a highly active psychrotolerent-though still mesophilic biomass.

Stability and reproducibility of low-temperature anaerobic biological wastewater treatment

The reproducibility of low-temperature anaerobic biological wastewater treatment trials was evaluated. Two identical anaerobic expanded granular sludge bed bioreactors were used to treat synthetic volatile fatty acid-based industrial wastewater under ambient conditions (18-20 degrees C) and to investigate the effect of various environmental perturbations on reactor performance and microbial community dynamics, which were assessed by chemical oxygen demand removal or effluent volatile fatty acid determination and terminal restriction fragment length polymorphism analysis, respectively. Methanogenic activity was monitored using specific methanogenic activity assays. Reactor performance and microbial community dynamics were each well replicated between Reactor 1 and Reactor 2. Archaeal dynamics, in particular, were associated with reactor operating parameters. Terminal restriction fragment length polymorphism data suggested dynamic acetoclastic and hydrogenophilic methanogenic populations and were in agreement with temporal specific methanogenic activity data. Putative psychrophilic populations were observed in anaerobic bioreactor sludge for the first time.

The influence of structural components of alkyl esters on their anaerobic biodegradation in marine sediment

Ester-based organic compounds are one type of synthetic base fluid added to drilling mud used during off-shore oil-drilling operations in the Gulf of Mexico. Concern over the environmental impact of synthetic base fluid (SBF) contaminated rock cuttings discharged into the Gulf of Mexico has prompted the promulgation of EPA regulations requiring that all SBF be tested for biodegradability in marine sediment prior to their use in the Gulf. In order to allow the design or selection of suitably biodegradable esters, the anaerobic biodegradability of a variety of ester compounds was tested using a marine sediment inoculum to reveal the effect of: (a) increasing the chain length of the acid moiety, (b) increasing the chain length of the alcohol moiety; (c) alternating the relative size of the alcohol and acid moieties, (d) branching in the alcohol moiety, and (e) the presence of an unsaturated bond in the acidic moiety. The chemical structure of esters was found to affect the completeness and rate of anaerobic biodegradation, and would affect their ability to be certified for use as an SBF in the Gulf of Mexico. Recommendations for ester usage include using esters that have a total carbon number of between 12 and 18 and avoiding the use of branched alcohols (or acids by inference). The presence of an unsaturated bond in the acid (or alcohol by inference) increased biodegradability of the ester.

Mineralization of the cyclic nitramine explosive hexahydro-1,3,5-trinitro-1,3,5-triazine by Gordonia and Williamsia spp

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a cyclic nitroamine explosive that is a major component in many military high-explosive formulations. In this study, two aerobic bacteria that are capable of using RDX as the sole source of carbon and nitrogen to support their growth were isolated from surface soil. These bacterial strains were identified by their fatty acid profiles and 16S ribosomal gene sequences as Williamsia sp. KTR4 and Gordonia sp. KTR9. The physiology of each strain was characterized with respect to the rates of RDX degradation and [U-14C]RDX mineralization when RDX was supplied as a sole carbon and nitrogen source in the presence and absence of competing carbon and nitrogen sources. Strains KTR4 and KTR9 degraded 180 microM RDX within 72 h when RDX served as the only added carbon and nitrogen source while growing to total protein concentrations of 18.6 and 16.5 microg/ml, respectively. Mineralization of [U-14C]RDX to 14CO2 was 30% by strain KTR4 and 27% by KTR9 when RDX was the only added source of carbon and nitrogen. The addition of (NH4)2SO4- greatly inhibited KTR9's degradation of RDX but had little effect on that of KTR4. These are the first two pure bacterial cultures isolated that are able to use RDX as a sole carbon and nitrogen source. These two genera possess different physiologies with respect to RDX mineralization, and each can serve as a useful microbiological model for the study of RDX biodegradation with regard to physiology, biochemistry, and genetics.

The reductive dechlorination of 2,3,4,5-tetrachlorobiphenyl in three different sediment cultures: evidence for the involvement of phylogenetically similar Dehalococcoides-like bacterial populations

Anaerobic cultures capable of reductively dechlorinating 2,3,4,5-tetrachlorobiphenyl (CB) were enriched from three different sediments, one estuarine, one marine and one riverine. Two different electron donors were used in enrichments with the estuarine sediment (elemental iron or a mixture of fatty acids). The removal of doubly flanked meta and para chlorines to form 2,3,5-CB and 2,4,5-CB was observed in all cultures. Bacterial community analysis of PCR-amplified 16S rRNA gene fragments revealed different communities in these cultures, with the exception of one common population that showed a high phylogentic relatedness to Dehalococcoides species. No Dehalococcoides-like populations were ever detected in control cultures to which no PCBs were added. In addition, the dynamics of this Dehalococcoides-like population were strongly correlated with dechlorination. Subcultures of the estuarine sediment culture demonstrated that the Dehalococcoides-like population disappeared when dechlorination was inhibited with 2-bromoethanesulfonate or when 2,3,4,5-CB had been consumed. These results provide evidence that Dehalococcoides-like populations were involved in the removal of doubly flanked chlorines from 2,3,4,5-CB. Furthermore, the successful enrichment of these populations from geographically distant and geochemically distinct environments indicates the widespread presence of these PCB-dechlorinating, Dehalococcoides-like organisms.

The Impact of Sediment Characteristics on PCB-dechlorinating Cultures: Implications for Bioaugmentation

PCB-dechlorinating cultures with complimentary activities, previously derived from estuarine Baltimore Harbor (B), marine Palos Verdes (P) and riverine Hudson River (H) sediments, were mixed and then inoculated into sterile sediments from the same sources. In the treatments containing sterile B sediment, the different inocula had limited impact on the bacterial community development and on dechlorination patterns, all of which were similar. In treatments containing sterile P or H sediment, however, different inocula resulted in significantly different PCB dechlorination patterns and bacterial communities. The B sediment appeared to support not only the most extensive and rapid dechlorination of the three sediments, but also supported a more diverse bacterial community. This was thought to be a result of nutritional richness, as it was high in organic carbon and micronutrients such as zinc and cobalt. Although mixing three PCB-dechlorinating cultures was able to produce a culture capable of enhanced PCB-dechlorinating activity as compared to single cultures, some activities were lost upon culture transfer. This indicates that care must be taken to establish robust PCB-dechlorinating cultures capable of extensive dechlorination prior to pursuing bioaugmentation. In addition, our results indicate that the concentration and availability of macro- and micro-nutrients could have a significant impact on the microbial community structure, and thus a thorough characterization of the sediment at contaminated sites is essential for implementing bioaugmentation for PCB bioremediation.

New low-temperature applications of anaerobic wastewater treatment

Low-temperature or psychrophilic (<20 degrees C) anaerobic biological treatment of simple industrial wastewaters has recently been proven feasible as an alternative to more expensive mesophilic (ca. 37 degrees C) technology. We implemented novel expanded granular sludge bed (EGSB)-based bioreactor designs for 27 psychrophilic anaerobic digestion (PAD) trials for the treatment of a broad range of simple and complex synthetic wastewaters representing dairy, food-processing and pharmaceutical sector effluents. A variety of operating parameters, such as hydraulic retention time, organic and volumetric loading rates and upflow velocity, were tested. Chemical oxygen demand (COD) removal efficiencies were recorded, which were comparable to previous mesophilic trials. Specific methanogenic activity, toxicity and biodegradability batch assays were employed to monitor the metabolic capabilities of microbial consortia in anaerobic reactors. The prevalence of psychrotolerant communities was observed and psychrophilic populations were detected in two of the reactors. The potential of PAD with respect to global sustainable development is discussed.

Assessment of anaerobic wastewater treatment failure using terminal restriction fragment length polymorphism analysis

AIMS

The suitability of genetic fingerprinting to study the microbiological basis of anaerobic bioreactor failure is investigated.

METHODS AND RESULTS

Two laboratory-scale anaerobic expanded granular sludge bed bioreactors, R1 and R2, were used for the mesophilic (37 degrees C) treatment of high-strength [10 g chemical oxygen demand (COD) l(-1)] synthetic industrial-like wastewater over a 100-day trial period. A successful start up was achieved by both bioreactors with COD removal over 90%. Both reactors were operated under identical parameters; however, increased organic loading during the trial induced a reduction in the COD removal of R1, while R2 maintained satisfactory performance (COD removal >90%) throughout the experiment. Specific methanogenic activity measurements of biomass from both reactors indicated that the main route of methane production was hydrogenotrophic methanogenesis. Terminal restriction fragment length polymorphism (TRFLP) analysis was applied to the characterization of microbial community dynamics within the system during the trial. The principal differences between the two consortia analysed included an increased abundance of Thiovulum- and Methanococcus-like organisms and uncultured Crenarchaeota in R1.

CONCLUSIONS

The results indicated that there was a microbiological basis for the deviation, in terms of operational performance, of R1 and R2.

SIGNIFICANCE AND IMPACT OF THE STUDY

High-throughput fingerprinting techniques, such as TRFLP, have been demonstrated as practically relevant for biomonitoring of anaerobic reactor communities.

Biotic and abiotic degradation of CL-20 and RDX in soils

The caged cyclic nitramine 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is a new explosive that has the potential to replace existing military explosives, but little is known about its environmental toxicity, transport, and fate. We quantified and compared the aerobic environmental fate of CL-20 to the widely used cyclic nitramine explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in surface and subsurface soil microcosms. Soil-free controls and biologically attenuated soil controls were used to separate abiotic processes from biologically mediated processes. Both abiotic and biological processes significantly degraded CL-20 in all soils examined. Apparent abiotic, first-order degradation rates (k) for CL-20 were not significantly different between soil-free controls (0.018 < k < 0.030 d(-1)) and biologically attenuated soil controls (0.003 < k < 0.277 d(-1)). The addition of glucose to biologically active soil microcosms significantly increased CL-20 degradation rates (0.068 < k < 1.22 d(-1)). Extents of mineralization of (14)C-CL-20 to (14)CO(2) in biologically active soil microcosms were 41.1 to 55.7%, indicating that the CL-20 cage was broken, since all carbons are part of the heterocyclic cage. Under aerobic conditions, abiotic degradation rates of RDX were generally slower (0 < k < 0.032 d(-1)) than abiotic CL-20 degradation rates. In biologically active soil microcosms amended with glucose aerobic RDX degradation rates varied between 0.010 and 0.474 d(-1). Biodegradation was a key factor in determining the environmental fate of RDX, while a combination of biotic and abiotic processes was important with CL-20. Our data suggest that CL-20 should be less recalcitrant than RDX in aerobic soils.

Development of an enzymatic assay for the determination of cellulose bioavailability in municipal solid waste

As there is a constant need to assess the biodegradation potential of refuse disposed of in landfills, we have developed a method to evaluate the biodegradability of cellulosic compounds (cellulose and hemicellulose) in municipal solid waste. This test is based on the quantification of monosaccharides released after the hydrolysis of solid waste samples with an optimised enzyme preparation containing commercially available cellulases and hemicellulases. We show that the amounts of monosaccharides could be related to the biodegradability of the cellulosic material contained in the samples. This enzymatic cellulose degradation test was assayed on 37 samples originating from three Belgian landfills and collected at different depths. As results correlated well with those obtained with a classical biochemical methane potential assay, this new and rapid test is sufficiently reliable to evaluate cellulose bioavailability in waste samples.

Anaerobic treatment of 2,4,6-trichlorophenol in an expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactor at 15 °C

Expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactors were operated at 15 degrees C for the treatment of 2,4,6-trichlorophenol (TCP)-containing volatile fatty acid (VFA)-based wastewaters. The seed sludge used as inoculum for the control (no TCP) and test reactor was unexposed to chlorophenols (CPs) prior to the 425-day trial. TCP supplementation to the feed at 50 mg TCPl(-1) partially inhibited the anaerobic degradation of the VFA feed measured as COD removal efficiency. However, the withdrawal and subsequent application of stepwise increments to the TCP loading resulted in steady COD removal. Terminal restriction fragment length polymorphism analysis showed Methanosaeta-like Archaea in the control reactor over the experimental period. Different methanogenic populations were detected in the test reactor and responded to the changes in feed composition. Bacterial community analyses indicated changes in the community structure over time and suggested the presence of Campylobacter-like, Acidimicrobium-like and Heliophilum-like organisms in the samples. TCP mineralisation was by a reductive dechlorination pathway through 2,4-dichlorophenol (DCP) and 4-chlorophenol (4-CP) or 2-chlorophenol (2-CP). CP degradation rates in sludge granules from the lower chamber of the hybrid EGSB-AF reactor was in the order TCP > DCP > 4-CP > 2-CP. However, a biodegradability order of lower CPs > TCP was observed in fixed-film biomass taken from the upper reactor chamber, thus reflecting the role of this reactor section in the metabolism of residual lower CPs from the lower sludge-bed stage of operation.

Anaerobic biological treatment of phenolic wastewater at 15-18 degrees C

Low-temperature, or psychrophilic (<20 degrees C) anaerobic digestion has been proven feasible for the mineralisation of simple wastewaters. In this study, hybrid expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactors were used to evaluate the feasibility of psychrophilic digestion for the treatment of phenol-containing wastewater. Efficient chemical oxygen demand and phenol removal were observed at organic and phenol loading rates of 5 kg COD m(-3)d(-1) and 0.4-1.2 kg phenol m(-3)d(-1) (400-1200 mg phenol [l wastewater](-1)), respectively. There was no long-term accumulation of volatile fatty acids in the reactor systems. Methanogenic activity was developed under psychrophilic conditions but anaerobic methane-producing populations remained mesophilic throughout the trial of 415 days.

Toxicity of nitrite toward mesophilic and thermophilic sulphate-reducing, methanogenic and syntrophic populations in anaerobic sludge

The various problems associated with treating sulphate-containing wastewaters stem inherently from successful competitive interactions between sulphate reducing bacteria (SRB) and other bacteria involved in the process, resulting in the formation of H(2)S. Prevention of in-reactor sulphide generation by use of specific SRB inhibitors presents a potential solution. Nitrite has been reported to be a specific inhibitor of SRB but its possible toxicity to syntrophic and methanogenic members of the anaerobic consortium has not been investigated. In batch activity and toxicity tests, under both mesophilic and thermophilic conditions, nitrite, at concentrations of up to 150 mg L(-1), was found to be ineffective as a specific inhibitor of SRB, and was also shown to have an inhibitory effect on the activity of syntrophic and methane-producing bacteria in mesophilic and thermophilic digester sludge samples.

In vitro gas production as a surrogate measure of the fermentability of cellulosic biomass to ethanol

Current methods for measuring ethanol yields from lignocellulosic biomass are relatively slow and are not well geared for analyzing large numbers of samples generated by feedstock management and breeding research. The objective of this study was to determine if an in vitro ruminal fermentation assay used in forage quality research was predictive of results obtained using a conventional biomass-to-ethanol conversion assay. In the conventional assay, herbaceous biomass samples were converted to ethanol by Saccharomyces cerevisiae cultures in the presence of cellulase enzymes. Cultures were grown in sealed serum bottles and gas production monitored by measuring increasing head space pressure. Gas accumulation as calculated from the pressure measurements was highly correlated (r(2)>0.9) with ethanol production measured by gas chromatography at 24 h or 7 days. The same feedstocks were also analyzed by in vitro ruminal digestion, as also measured by gas accumulation. Good correlations (r(2) approximately 0.63-0.82) were observed between ethanol production during simultaneous saccharification and fermentation and gas accumulation in parallel in vitro ruminal fermentations. Because the in vitro ruminal fermentation assay can be performed without sterilization of the medium and does not require aseptic conditions, this assay may be useful for biomass feedstock agronomic and breeding research.

Acetylene inhibition of trichloroethene and vinyl chloride reductive dechlorination

Kinetic studies reported here have shown that acetylene is a potent reversible inhibitor of reductive dehalogenation of trichloroethene (TCE) and vinyl chloride (VC) by a mixed dehalogenating anaerobic culture. The mixed culture was enriched from a contaminated site in Corvallis, OR, and exhibited methanogenic, acetogenic, and reductive dehalogenation activities. The H2-fed culture transformed TCE to ethene via cis-dichloroethene (c-DCE) and VC as intermediates. Batch kinetic studies showed acetylene reversibly inhibited reduction of both TCE and VC, and the levels of inhibition were strongly dependent on acetylene concentrations in both cases. Acetylene concentrations of 192 and 12 microM, respectively, were required to achieve 90% inhibition in rates of TCE and VC transformation at an aqueous concentration of 400 microM. Acetylene also inhibited methane production (90% inhibition at 48 microM) but did not inhibit H2-dependent acetate production. Mass balances conducted during the studies of VC inhibition showed that acetogenesis, VC transformation to ethene, and methane production were responsible for 52%, 47%, and 1% of the H2 consumption, respectively. The results indicate that halorespiration is the dominant process responsible for VC and TCE transformation and that dehalorespiring organisms are the target of acetylene inhibition. Acetylene has potential use as a reversible inhibitor to probe the biological activities of reductive dechlorination and methanogenesis. It can be added to inhibit reactions and then removed to permit reactions to proceed. Thus, it can be a powerful tool for investigating intrinsic and enhanced anaerobic remediation of chloroethenes at contaminated sites. The results also suggest that acetylene produced abiotically by reactions of chlorinated ethenes with zero-valent iron could inhibit the biological transformation of VC to ethene.

Hybrid adaptive optimal control of anaerobic fluidized bed bioreactor for the de-icing waste treatment

Hybrid adaptive control strategy was developed and tested for the degradation of propylene glycol, a major component in de-icing waste, in an anaerobic fluidized bed bioreactor (AFBR). A linearized model with time-varying parameters was first employed to describe the dynamic behavior of the AFBR using a recursive off-line system identification method. A hybrid adaptive control strategy was then tested using a recursive off-line system identification routine followed by an on-line adaptive optimal control algorithm. The objective of the controller was to achieve the desired set point value of the propionate concentration (stand-alone control output variable) by manipulating the dilution rate (control input variable). To do so, the optimal control law was developed by minimizing a cost function with constraint equations. This novel idea was successfully applied to the underlying system for 200 h. The set point (700 mg HPrl(-1)) was achieved even in the case where the feed concentration suddenly increased by 50% (9000 mg HPrl(-1) to 13500 mg HPrl(-1)).

Regulatory role of n-propanol in propylene glycol biomethanization under overload

This work examines the transient response of an anaerobic fluidized bed bioreactor to an overload of propylene glycol (PG), the primary component in aircraft de-icing waste. Under favorable operating conditions, PG was converted to n-propanol (n-PrOH) and propionate (HPr), and subsequently n-PrOH was completely converted into HPr. HPr was then fully degraded to methane and carbon dioxide via acetate. Under an overload condition, n-PrOH conversion to propionate was completely blocked but propionate degradation continued, contrary to free-energy computations in which n-PrOH should rapidly degrade and HPr should accumulate. When the imposed overload condition was relieved, the accumulated n-PrOH was rapidly converted into propionate. n-PrOH, then, could act as a temporal sink for reducing equivalents (XH(2)) and could regulate the overall PG methanazation process. n-PrOH should be monitored along with typical VFAs such as HPr to avoid sudden VFA accumulation and thus to optimize process performance for PG methanization.

Changes in enantiomeric fractions during microbial reductive dechlorination of PCB132, PCB149, and araclor 1254 in Lake Hartwell sediment microcosms

The enantioselectivity of microbial reductive dechlorination of chiral PCBs in sediments from Lake Hartwell, SC, was determined by microcosm studies and enantiomer-specific GC analysis. Sediments from two locations in the vicinity of the highest levels of PCB contamination were used as inocula. Dechlorination activity was monitored by concentration decreases in the spiked chiral PCBs and formation of dechlorination products using both achiral and chiral chromatography. Live microcosms spiked with PCB132 (234-236) exhibited dechlorination of PCB132 to PCB91 (236-24) and PCB51 (24-26). Meta dechlorination was the dominant mechanism. Microcosms spiked with PCB149 (245-236) exhibited preferential para dechlorination of PCB149 to PCB95 (236-25), followed by meta dechlorination to PCB53 (25-26) and subsequently PCB19 (26-2). Dechlorination of chiral PCB132 and PCB149 was not enantioselective. In Aroclor 1254-spiked microcosms, reductive dechlorination of PCB149 also was nonenantioselective. These results suggest that dechlorinating enzymes responsible for the dehalogenation of the chiral PCB132 and PCB149 congeners bind the two enantiomers equally. Reductive dechlorination of PCB91 and PCB95, however, occurred in an enantioselective manner, indicating that the dechlorinating enzymes for these PCBs are enantiomer-specific. The chlorine substitution pattern on the biphenyl ring appears to influence whether reductive dechlorination of chiral PCB congeners is enantioselective. Enantioselective PCB dechlorination by the microbial population of Lake Hartwell sediments occurs for select chiral PCBs; thus, certain chiral PCBs might be useful as markers for in situ reductive dechlorination.

Operating conditions for the determination of the biochemical acidogenic potential of wastewater

The aim of this work was to study the test conditions for the determination of the biochemical acidogenic potential (BAP) of wastewater, which should be useful to predict the performance of enhanced biological phosphorus removal (EBPR). Proposed operating conditions for a simple and reproducible BAP test in 250 ml serum bottles (equipped with black butyl stoppers and magnetic bars) are: use of either frozen or fresh water, no inoculum addition, fermentation carried out in the dark during 15 days, addition of 1 mM bromo-ethane sulfonate (BES) and 2 mM barium chloride (BaCl2), stirring speed strong enough to maintain vortex conditions, no pH control and controlled temperature of 20 degrees C.

Anaerobic digestion of alcohol sulfate (anionic surfactant) rich wastewater--batch experiments. Part I: influence of the surfactant concentration

Textile wet processing wastewater (e.g., from cotton desizing) contains high concentrations of surfactants as well as readily biodegradable compounds like starch and other carbohydrates. Decyl sulfate (DS, surfactant) and soluble starch were used as model pollutants for biodegradation batch experiments. Very high loadings of the biomass were applied (DS: 21.7-217 g/kg cell dry weight (CDW); starch: 910 g/kg cell dry weight) to study inhibitory effects of the surfactant on the degradation cascade of the biopolymer. The starch hydrolysis was inhibited above sludge loadings of 65 g DS/kg CDW. Acidogenesis was the degradation step with the highest resistance towards inhibitory effects of the surfactant, whereas methanogenesis proved to be the most sensitive. The effects of the surfactant were described by the change of the methane evolution, which was reduced by 50% in 87 days with an addition of 58 g DS/kg CDW. The surfactant caused a high temporary accumulation of intermediates like volatile fatty acids. At the highest loading (217 g DS/kg CDW) the conversion of the substrate to methane was only minor.

Integration of biotechnological wastewater treatment units in textile finishing factories: from end of the pipe solutions to combined production and wastewater treatment units

Increasing costs for water, wastewater and energy put pressure on textile finishing plants to increase the efficiency of wet processing. An improved water management can decrease the use of these resources and is a prerequisite for the integration of an efficient, anaerobic on-site pretreatment of effluents that will further cut wastewater costs. A two-phase anaerobic treatment is proposed, and successful laboratory experiments with model effluents from the cotton finishing industry are reported. The chemical oxygen demand of this wastewater was reduced by over 88% at retention times of 1 day or longer. The next step to boost the efficiency is to combine the production and wastewater treatment. The example of cotton fabric desizing (removing size from the fabric) illustrates how this final step of integration uses the acidic phase bioreactor as a part of the production and allows to close the water cycle of the system.

Degradation of natural polyphenols by methanogenic consortia enriched from digested municipal sludge

Using digested municipal sludge as the inoculum and either rutin, quercetin or hesperidin as the sole external carbon source. methanogenic consortia were enriched which converted various flavonoids at initial concentration of 0.5 3.0mM during stationary incubation at 37 degrees C in serum bottles with specific rates ranging from 0.025 to 0.073 micromol min(-1) (mg protein)(-1). In the culture fluid, several hydroxyaromatic metabolites as well as VFA (acetate, propionate, n-butyrate) were detected and biogas was formed in the headspace of the test bottles. Most of these metabolites were identified. Based on their sequential appearance/disappearance in the test cultures it was concluded that following initial hydrolysis of the glycosidic bond by cellular enzymes, ring C of the flavane skeleton was hydrolytically cleaved yielding an A- and B-ring fission product. In case of the flavonol quercetin, phloroglucinol (A-ring) and 3,4-dihydroxyphenylacetate (B-ring) were identified as the fission products whereas the flavanone hesperetin was cleaved with formation of phloroglucinol (A-ring) and 3,4-dihydroxyphenylpropionate (B-ring). In pre-adapted subcultures amended with either hesperidin or hesperetin, all of the formed hydroxyaromatic metabolites disappeared within 100 h of incubation whereas in the culture medium of rutin and quercetin degrading consortia m-cresol (3-methylphenol) was formed as the ultimate hydroxyaromatic metabolite being detectable in considerable amounts even after prolonged incubation.

Identification and characterization of nuclease activities in anaerobic environmental samples

DNA-degrading activity from anaerobic samples of bovine ruminal fluid, primary anaerobic digestor wastewater, freshwater sediments, and marine sediments was observed in the presence of 5 mM EDTA. Nuclease activity experiments involved exposing salmon chromosomal DNA to the environmental samples in 50 mM pH 7.2 buffer, incubating at 37°C, and subjecting the products to electrophoresis. The same stock and concentration of EDTA used in these assays (5 mM) completely inhibited commercial grade DNase. Nuclease activity in two of the samples, ruminal fluid and wastewater, was further characterized. DNA degradation in the ruminal sample was significantly reduced when EDTA or citrate concentrations were increased to 50 mM or above. DNA degradation activity in ruminal fluid was associated with material that passed through a 0.22-µm filter, but wastewater activity was associated with material retained by a 3-µm filter. Degradation activity in the wastewater was resistant to heat pretreatment, whereas the rumen activity was heat-labile (70°C, 60 min). These results demonstrated the biochemical complexity of these two environments and that high molecular weight DNA has a short half-life in these anaerobic environments.Key words: nucleic acid degradation, ruminal fluid, wastewater.

Degradation half-life times of PCDDs, PCDFs and PCBs for environmental fate modeling

Literature search of the knowledge on the degradation of persistent organic pollutants (POPs) in environmental compartments air, water, soil and sediment was done in purpose to find properties of POPs of interest for modeling. One degradation process, hydrolysis (chemical degradation), was omitted as negligibly slow for POPs studied. The other two, photolysis and biodegradation processes, were considered separately in purpose to develop estimation procedures. The estimates can be given as pseudo first-order rate constants kP for photolysis and kB for biodegradation. For each compartment, an overall degradation rate is k(tot) = kP + kB and lifetime t(1/2) = ln 2/k(tot). The latter values, lifetimes in each compartment, will be used as input parameters to the Baltic Sea model.

Evaluation of laboratory-made sludge for an anaerobic biodegradability test and its use for assessment of 13 chemicals

Laboratory-made sludge for a biogas based anaerobic biodegradability test was prepared as an alternative for digested sludge from wastewater treatment plants (WWTPs). Biodegradation activities and background gas productions of digested sludge from various WWTPs were found to vary significantly depending on the source, which adversely affected test reliability. Subsequently, test conditions such as sludge concentration and sludge washing were examined with the laboratory-made sludge and a sludge concentration of 1.0 g-SS/L without washing was determined to be most suitable. Under these conditions, biodegradability tests were conducted for 13 select chemicals and their relative toxicities to methanogenic bacteria were evaluated. The results of biodegradability tests showed that chemicals with -OH and -CH2OH radicals were readily biodegraded and those with -Cl, -NO2, -NH2, -SO3H and -CH3 had inhibited degradation responses m-nitriphenol and 2,4,6-trichlorophenol were highly toxic to methanogenic bacteria, with m-nitrophenol completely inhibiting methane fermentation as low as 20 mg/L.

The anaerobic degradation of endosulfan by indigenous microorganisms from low-oxygen soils and sediments

Indigenous mixed populations of anaerobic microorganisms from an irrigation tailwater drain and submerged agricultural chemical waste pit readily biodegraded the major isomer of endosulfan (endosulfan I). Endosulfan I was biodegraded to endosulfan diol, a low toxicity degradation product, in the presence of organic carbon sources under anaerobic, methanogenic conditions. While there was extensive degradation (>85%) over the 30 days, there was no significant enhancement of degradation from enriched inocula. This study demonstrates that endosulfan I has the potential to be biodegraded in sediments, in the absence of enriched microorganisms. This is of particular importance since such sediments are prevalent in cotton-growing areas and are typically contaminated with endosulfan residues. The importance of minimizing non-biological losses has also been highlighted as a critical issue in determining anaerobic biodegradation potential. Seals for such incubation vessels must be both oxygen and pollutant impermeable. Teflon-lined butyl rubber provides such a seal because of its resistance to the absorption of volatiles and in preventing volatilization. Moreover, including a 100 mM phosphate buffer in the anaerobic media has reduced non-biological losses from chemical hydrolysis, allowing biodegradation to be assessed.

Inhibitory effects and biotransformation of acrylic acid in computer-controlled pH-stat CSTRs

In this study, the inhibitory effects and anaerobic biotransformation of acrylic acid in computer-controlled pH-stat completely stirred tank reactors (CSTRs) with two different cultures, namely unacclimated and acrylate-acclimated acetate-enriched Methanosarcina and homogenized (crushed) granular cultures, were investigated. The microbial acclimation, influent concentration, and loading rate of acrylic acid were studied in the experiments. The experimental results revealed that methanogenic cultures at a concentration of 3200 +/- 80 mg/L as volatile suspended solids (VSS) could be acclimated to acrylic acid up to a loading rate of 220 mg/L per day (0.068 g acrylic acid/g VSS per day) in the presence of a constant acetate concentration of 2000 +/- 200 mg/L as the primary substrate after 300 days of acclimation. The same cultures (680 +/- 80 mg/L as VSS), after 80 days of acclimation to acrylic acid as the sole carbon source, transformed acrylic acid up to the loading rate of about 200 mg/L per day (0.29 g acrylic acid/g VSS per day) almost completely (>99%) to acetic and propionic acid, but could not effectively metabolize these intermediate products. Acrylate-acclimated homogenized granular cultures (6900 +/- 80 mg/L as VSS) effectively metabolized 2200 mg/L per day (0.32 g acrylic acid/g VSS per day) of acrylic acid, as the sole carbon source, after 50 days of severe inhibition.

2-Bromoethanesulfonate, sulfate, molybdate, and ethanesulfonate inhibit anaerobic dechlorination of polychlorobiphenyls by pasteurized microorganisms

Dechlorination of Aroclor 1242 by pasteurized microorganisms was inhibited by 2-bromoethanesulfonate (BES), sulfate, molybdate, and ethanesulfonate. Consumption of these anions and production of sulfide from BES were detected. The inhibition could not be relieved by hydrogen. Taken together these results suggest that pattern M dechlorination is mediated by spore-forming sulfidogenic bacteria. These results also suggest that BES may inhibit anaerobic dechlorination by nonmethanogens by more than one mechanism.

Phylogenetic analysis of an anaerobic, trichlorobenzene-transforming microbial consortium

A culture-independent phylogenetic survey for an anaerobic trichlorobenzene-transforming microbial community was carried out. Small-subunit rRNA genes were PCR amplified from community DNA by using primers specific for Bacteria or Euryarchaeota and were subsequently cloned. Application of a new hybridization-based screening approach revealed 51 bacterial clone families, one of which was closely related to dechlorinating Dehalobacter species. Several clone sequences clustered to rDNA sequences obtained from a molecular study of an anaerobic aquifer contaminated with hydrocarbons and chlorinated solvents (Dojka et al., Appl. Env. Microbiol. 64:3869-3877, 1998).

Altered biologic activities of commercial polychlorinated biphenyl mixtures after microbial reductive dechlorination

The reductive dechlorination of polychlorinated biphenyls (PCBs) by anaerobic bacteria has recently been established as an important environmental fate of these compounds. This process removes chlorines directly from the biphenyl ring with replacement by hydrogen, resulting in a product mixture in which the average number of chlorines per biphenyl is reduced. In this study, dechlorination of commercial PCB mixtures (Aroclors 1242 and 1254) by microorganisms eluted from PCB-contaminated sediments of the River Raisin (Michigan) and Silver Lake (Massachusetts) caused a depletion in the proportion of highly chlorinated PCB congeners and an accumulation of lesser-chlorinated congeners. Dechlorination occurred primarily at the meta and, to a much lesser extent, para positions of biphenyl. The concentrations of the coplanar congeners including 3,3',4,4',5-pentachlorobiphenyl, the most potent dioxinlike congener, were significantly lowered by reductive dechlorination. Microbial reductive dechlorination of commercial PCB mixtures caused a substantial reduction in biologic activities in several instances. It significantly lowered or eliminated the inhibitory effects of Aroclors on fertilization of mouse gametes in vitro. Similarly, the dechlorinated product mixtures had substantially lower ethoxyresorufin-O-deethylase induction potencies and showed less ability to induce activating protein 1 transcription factor activity as compared to the unaltered Aroclors. In other assays the same dechlorinated product mixtures demonstrated biologic activities similar to the nondechlorinated Aroclors, including the ability of PCB mixtures to stimulate insulin secretion and cause neutrophil activation. The data presented here establish that the biologic activities of commercial PCB mixtures are altered by microbial reductive dechlorination and that an assessment of their toxic potential requires an array of tests that include the different mechanisms associated with PCBs.

Reductive dechlorination of DDE to DDMU in marine sediment microcosms

DDT is reductively dechlorinated to DDD and dehydrochlorinated to DDE; it has been thought that DDE is not degraded further in the environment. Laboratory experiments with DDE-containing marine sediments showed that DDE is dechlorinated to DDMU in both methanogenic and sulfidogenic microcosms and that DDD is dehydrochlorinated to DDMU three orders of magnitude more slowly. Thus, DDD does not appear to be an important precursor of the DDMU found in these sediments. These results imply that remediation decisions and risk assessments based on the recalcitrance of DDE in marine and estuarine sediments should be reevaluated.

Anaerobic degradation of xenobiotics by organisms from municipal solid waste under landfilling conditions

The potential for biological transformation of 23 xenobiotic compounds by microorganisms in municipal solid waste (MSW) samples from a laboratory scale landfill reactor was studied. In addition the influence of these xenobiotic compounds on methanogenesis was investigated. All R11, 1,1 dichloroethylene, 2,4,6 trichlorophenol, dimethyl phthalate, phenol, benzoate and phthalic acid added were completely transformed during the period of incubation ( > 100 days). Parts of the initially added perchloroethylene, trichloroethylene, R12, R114, diethyl phthalate, dibutyl phthalate and benzylbutyl phthalate were transformed. Methanogenesis from acetate was completely inhibited in the presence of 2,5 dichlorophenol, whereas 2,4,6 trichlorophenol and R11 showed an initial inhibition, whenafter methane formation recovered. No transformation or effect on the anaerobic microflora occurred for R13, R22, R114, 3 chlorobenzoate, 2,4,6 trichlorobenzoate, bis(2 ethyl)hexyl phthalate, diisodecyl phthalate and dinonyl phthalate. The results indicate a limited potential for degradation, of the compounds tested, by microorganisms developing in a methanogenic landfill environment as compared with other anaerobic habitats such as sewage digestor sludge and sediments.

Different types of sludge granules in UASB reactors treating acidified wastewaters

The influence of a high energy substrate, i.e. sucrose, on the granular sludge yield and the development of different types of granular sludge was investigated by using Upflow Anaerobic Sludge Bed (UASB) reactors fed with synthetic wastewater. The feed COD was a mixture of volatile fatty acids (VFA) i.e., 20, 40, and 40% of the COD as C2-, C3-, and C4-VFA, respectively. Furthermore, experiments were carried out in which 10 and 30% of the VFA COD was substituted with sucrose. The following distinctly different types of granules were observed in each testrun: in the reactor fed with solely VFA, black (B) and white (W) granules developed; in the reactor fed with a mixture of 90% VFA and 10% sucrose, three types of granules i.e., B, W, and grey (G) granules could be seen; in the reactor fed with 70% VFA and 30% sucrose, only W and G granules were found. The granular sludge yield increased proportional to the amount of sucrose COD. At steady-state performance of the reactors, specific acidogenic (SAA) and methanogenic (SMA) activity tests on these granules revealed that B granules had the highest SMA with low SAA. The W granules had very high SMA with low SAA. G granules gave the highest SAA with a considerable SMA. Measurement of coenzyme F420 revealed that B granules consist mainly of acetoclastic methanogens. The fore-mentioned tests were supplemented with analyses of the wash-out cells present in the reactor effluent and the results suggested that acidogens, if present, prevail at the granule surface. The B granules were particularly rich in Ca, Mn, and Zn minerals. The size distribution analysis showed that the granule diameter increased in the following order: B < W < G granules. The biogas bubbles tended to adhere to the B and W granules but not so strongly to the G granules.