Correspondence between community structure and function during succession in phenol- and phenol-plus-trichloroethene-fed sequencing batch reactors

The effects of more than 2 years of trichloroethene (TCE) application on community succession and function were studied in two aerobic sequencing batch reactors. One reactor was fed phenol, and the second reactor was fed both phenol and TCE in sequence twice per day. After initiation of TCE loading in the second reactor, the TCE transformation rates initially decreased, but they stabilized with an average second-order rate coefficient of 0.044 liter mg(-1) day(-1) for 2 years. In contrast, the phenol-fed reactor showed higher and unstable TCE transformation rates, with an average rate coefficient of 0.093 liter mg(-1) day(-1). Community analysis by terminal restriction fragment length polymorphism (T-RFLP) analysis of the 16S rRNA genes showed that the phenol-plus-TCE-fed reactor had marked changes in community structure during the first 100 days and remained relatively stable afterwards, corresponding to the period of stable function. In contrast, the community structure of the phenol-fed reactor changed periodically, and the changes coincided with the periodicity observed in the TCE transformation rates. Correspondence analysis of each reactor community showed that different community structures corresponded with function (TCE degradation rate). Furthermore, the phenol hydroxylase genotypes, as determined by restriction fragment length polymorphism analysis, corresponded to community structure patterns identified by T-RFLP analysis and to periods when the TCE transformation rates were high. Long-term TCE stress appeared to select for a different and stable community structure, with lower but stable TCE degradation rates. In contrast, the community under no stress exhibited a dynamic structure and dynamic function.     

Correspondence between Community Structure and Function during Succession in Phenol- and Phenol-plus-Trichloroethene-Fed Sequencing Batch Reactors

The effects of more than 2 years of trichloroethene (TCE) application on community succession and function were studied in two aerobic sequencing batch reactors. One reactor was fed phenol, and the second reactor was fed both phenol and TCE in sequence twice per day. After initiation of TCE loading in the second reactor, the TCE transformation rates initially decreased, but they stabilized with an average second-order rate coefficient of 0.044 liter mg⁻¹ day⁻¹ for 2 years. In contrast, the phenol-fed reactor showed higher and unstable TCE transformation rates, with an average rate coefficient of 0.093 liter mg⁻¹ day⁻¹. Community analysis by terminal restriction fragment length polymorphism (T-RFLP) analysis of the 16S rRNA genes showed that the phenol-plus-TCE-fed reactor had marked changes in community structure during the first 100 days and remained relatively stable afterwards, corresponding to the period of stable function. In contrast, the community structure of the phenol-fed reactor changed periodically, and the changes coincided with the periodicity observed in the TCE transformation rates. Correspondence analysis of each reactor community showed that different community structures corresponded with function (TCE degradation rate). Furthermore, the phenol hydroxylase genotypes, as determined by restriction fragment length polymorphism analysis, corresponded to community structure patterns identified by T-RFLP analysis and to periods when the TCE transformation rates were high. Long-term TCE stress appeared to select for a different and stable community structure, with lower but stable TCE degradation rates. In contrast, the community under no stress exhibited a dynamic structure and dynamic function.     

Performance characterization of a model bioreactor for the biodegradation of trichloroethylene by Pseudomonas cepacia G4

Pseudomonas cepacia G4 grown in chemostats with phenol demonstrated constant specific degradation rates for both phenol and trichloroethylene (TCE) over a range of dilution rates. Washout of cells from chemostats was evident at a dilution rate of 0.2 h-1 at 28 degrees C. Increased phenol concentrations in the nutrient feed led to increased biomass production with constant specific degradation rates for both phenol and TCE. The addition of lactate to the phenol feed led to increased biomass production but lowered specific phenol and TCE degradation rates. The maximum potential for TCE degradation was about 1.1 g per day per g of cell protein. Cell growth and degradation kinetic parameters were used in the design of a recirculating bioreactor for TCE degradation. In this reactor, the total amount of TCE degraded increased as either reaction time or biomass was increased. TCE degradation was observed up to 300 microM TCE with no significant decreases in rates. On the average, this reactor was able to degrade 0.7 g of TCE per day per g of cell protein. These results demonstrate the feasibility of TCE bioremediation through the use of bioreactors.     

Performance characterization of a model bioreactor for the biodegradation of trichloroethylene by Pseudomonas cepacia G4.

Pseudomonas cepacia G4 grown in chemostats with phenol demonstrated constant specific degradation rates for both phenol and trichloroethylene (TCE) over a range of dilution rates. Washout of cells from chemostats was evident at a dilution rate of 0.2 h-1 at 28 degrees C. Increased phenol concentrations in the nutrient feed led to increased biomass production with constant specific degradation rates for both phenol and TCE. The addition of lactate to the phenol feed led to increased biomass production but lowered specific phenol and TCE degradation rates. The maximum potential for TCE degradation was about 1.1 g per day per g of cell protein. Cell growth and degradation kinetic parameters were used in the design of a recirculating bioreactor for TCE degradation. In this reactor, the total amount of TCE degraded increased as either reaction time or biomass was increased. TCE degradation was observed up to 300 microM TCE with no significant decreases in rates. On the average, this reactor was able to degrade 0.7 g of TCE per day per g of cell protein. These results demonstrate the feasibility of TCE bioremediation through the use of bioreactors.     

A comparative study of gel entrapped and membrane attached microbial reactors for biodegrading phenol

A comparative study between two reactors, one using microorganisms entrapped in calcium alginate gel, and the other using microorganisms attached on the surface of a membrane (polymeric microporous sheeting, MPS^TM) to biodegrade phenol is performed. Results indicate that the alginate bead bioreactor is efficient at higher phenol concentrations while the membrane bioreactor shows better performance at lower phenol concentrations. This unique response is primarily attributed to the different techniques by which the microorganisms are immobilized in the two reactors.In batch mode, below a starting concentration of 100 ppm phenol, biodegradation rates in the membrane bioreactor are (7.58 to 12.02 mg phenol/h · g dry biomass) atleast 10 times the rates in alginate bead bioreactor (0.74 to 1.32 mg phenol/h · g dry biomass). Biodegradation rates for the two reactors match at a starting concentration of 250 ppm phenol. Above 500 ppm phenol, the rates in the alginate bead bioreactor are (7.3 to 8.1 mg phenol/h · g dry biomass) on an average 5.5 times the corresponding rates in the membrane bioreactor (2.18 to 1.03 mg phenol/h · g dry biomass).In continuous feed mode the steady state degradation rates in the membrane bioreactor are one to two orders of magnitude higher than the alginate bead bioreactor below 150 ppm inlet phenol concentration. At an inlet concentration around 250 ppm phenol the rates are comparable. Above 500 ppm of phenol the rates in the alginate bioreactor are an order of magnitude high than the membrane bioreactor.Due to substrate inhibition, and its inability to sustain a high biomass concentration, the membrane bioreactor shows poor efficiencies at phenol concentrations above 250 ppm. At low phenol concentrations the apparent reaction rates in the alginate bead bioreactor decrease due to the diffusional resistance of the gel matrix, while biodegradation rates in the membrane bioreactor remain high due to essentially no external diffusional resistance.Results indicate that a combined reactor system can be more effective for bioremediation than either separate or attached microbial reactors.     

Aerobic,phenol-induced TCE degradation in completely mixed,continuous-culture reactors

BothPseudomonas putida F1 and a mixed culture were used to study TCE degradation in continuous culture under aerobic, non-methanotrophic conditions. TCE mass balance studies were performed with continuous culture reactors to determine the total percent removed in the reactors, and to quantify the percent removed by air stripping and biodegradation. Adsorption of TCE to biomass was assumed to be negligible. This research demonstrated the feasibility of treating TCE-contaminated water under aerobic, non-methanotrophic conditions with a mixed-culture, continuous-flow system.Initially glucose and acetate were fed as primary substrates. Pnenol, which has been shown to induce TCE-degrading enzymes, was fed at a much lower concentration (20mg/L). Little degradation of TCE was observed when acetate and glucose were the primary substrates. After omitting glucose and acetate from the feed and increasing the phenol concentration to 50mg/L, TCE biotransformation was observed at a significant level (46%). When the phenol concentration in the feed was increased to 420mg/L, 85% of the incoming TCE was estimated to have been biodegraded. Under the same conditions, phenol utilization by the mixed culture was greater than that ofP. putida F1, and TCE degradation by the mixed culture (85%) exceeded that ofP. putida F1 (55%). The estimated percent-of-TCE biodegraded by the mixed culture was consistently greater than 80% when phenol was fed at 420mg/L. Biodegradation of TCE was also observed in mixed-culture, batch experiments.     

Rate limiting factors in trichloroethylene co-metabolic degradation by phenol-grown aerobic granules

The potential of aerobic granular sludge in co-metabolic removal of recalcitrant substances was evaluated using trichloroethylene (TCE) as the model compound. Aerobic granules cultivated in a sequencing batch reactor with phenol as the growth substrate exhibited TCE and phenol degradation activities lower than previously reported values. Depletion of reducing energy and diffusion limitation within the granules were investigated as the possible rate limiting factors. Sodium formate and citrate were supplied to the granules in batch studies as external electron sources. No significant enhancing effect was observed on the instant TCE transformation rates, but 10 mM formate could improve the ultimate transformation capacity by 26 %. Possible diffusion barrier was studied by sieving the biomass into five size fractions, and determining their specific TCE and phenol degradation rates and capacities. Biomass in the larger size fractions generally showed lower activities. Large granules of >700 μm diameter exhibited only 22 % of the flocs’ TCE transformation capacity and 35 % of its phenol dependent SOUR, indicating the possible occurrence of diffusion limitation in larger biomass. However, the highest specific TCE transformation rate was observed with the fraction that mostly consisted of small granules (150–300 μm), suggesting an optimal size range while applying aerobic granules in TCE co-metabolic removal.     

Laboratory evaluation of a two-stage treatment system for TCE cometabolism by a methane-oxidizing mixed culture

The objective of this research was to evaluate several factors affecting the performance of a two-stage treatment system employing methane-oxidizing bacteria for trichloroethylene (TCE) biodegradation. The system consists of a completely mixed growth reactor and a plug-flow transformation reactor in which the TCE is cometabolized. Laboratory studies were conducted with continuous growth reactors and batch experiments simulating transformation reactor conditions. Performance was characterized in terms of TCE transformation capacity (T(C), g TCE/g cells), transformation yield (T(Y), g TCE/g CH(4)), and the rate coefficient ratio k(TCE)/K(S,TCE) (L/mg-d). The growth reactor variables studied were solids retention time (SRT) and nutrient nitrogen (N) concentration. Formate and methane were evaluated as potential transformation reactor amendments. Comparison of cultures from 2- and 8-day SRT (nitrogen-limited) growth reactors indicated that there was no significant effect of growth reactor SRT or nitrogen availability on T(C) or T(Y), but N-limited conditions yielded higher k(TCE)/K(S,TCE). The TCE cometabolic activity of the 8-day SRT, N-limited growth reactor culture varied significantly during a 7-year period of operation. The T(C) and T(Y) of the resting cells increased gradually to levels a factor of 2 higher than the initial values. The reasons for this increase are unknown. Formate addition to the transformation reactor gave higher T(C) and T(Y) for 2-day SRT growth reactor conditions and significantly lower T(C), T(Y), and k(TCE)/K(S,TCE) for 8-day SRT N-limited conditions. Methane addition to the transformation reactor inhibited TCE cometabolism at low TCE concentrations and enhanced TCE cometabolism at high TCE concentrations, indicating that the TCE cometabolism in the presence of methane does not follow simple competitive inhibition kinetics. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 650-659, 1997.     

Transition Metal Catalyst-Assisted Reductive Dechlorination of Perchloroethylene by Anaerobic Aquifer Enrichments

Bioremediation of groundwater contaminated with chlorinated solvents, such as perchloroethylene (PCE) or carbon tetrachloride, can be accomplished by adding nutrients to stimulate a microbial community capable of reductive dechlorination. However, biotransformation of these solvents, especially PCE, typically occurs very slowly or not at all. Experiments were conducted to evaluate whether the addition of transition metal tetrapyrrole catalysts would increase the reductive transformation of PCE to trichloroethylene (TCE) by sulfate-reducing enrichment cultures. Batch assays were used to test vitamin B₁₂ and two synthetic sulfonatophenyl porphine catalysts for the stimulation of reductive dechlorination of PCE by sulfate-reducing bacteria (SRB) enriched from aquifer sediments from two locations at Dover Air Force Base. Cells from the enrichments were concentrated and added to batch assay vials. Vials containing SRB cells amended with vitamin B12 exhibited enhanced transformation of PCE to TCE compared with reactors amended with either synthetic catalysts or reactors containing cells alone. Methane production was observed in reactors that exhibited maximum levels of dechlorination. Storage of aquifer sediments between enrichments led to decreased levels of PCE dechlorination in subsequent assays.     

Startup of anaerobic biofilm fluidized bed reactors on molasses and phenol under various conditions

Fluidized sand bed anaerobic biofilm reactors were operated in parallel to study the effects of inoculum, loading, residence time and carrier type on the startup dynamics for the degradation of molasses and phenol. Degradation rates generally depended most directly on concentrations rather than on other operating variables. Residence times did not appear to directly influence startup. Short residence times and high loadings gave the highest specific activities for both substrates. The type of inoculum was found to be most important for the molasses system, and inoculation on fresh carrier was found to be better than reinoculation. The two times higher specific biomass retention on Siran porous glass gave essentially the same degradation rates on a volume basis.List of Symbols L kg/h loading of reactor - M kg/kg biomass per carrier mass - Red. % reduction of feed concentration due to degradation - R kg/(m³ · h) reaction rate - S kg/m³ substrate concentration in reactor and effluent - S ₀ kg/m³ substrate concentration in feed - t h time     

Disturbance,starvation, and overfeeding stresses detected by microbial lipid biomarkers in high-solids high-yield methanogenic reactors

Summary Microbial biomass and community structure of methanogenic anaerobic biomass reactors can be quantitatively monitored by signature, lipid analysis. The eubacterial and eukaryotic polar lipid fatty acids and the methanogen polar lipid ethers are reliable measures of their respective biomasses. The pattern of polar lipid fatty acids yields information on the community structure and metabolic state of the eubacteria and eukaryotes. These biomarker methods were applied over a 2-day feeding cycle of a highly productive batch-fed high-solids anaerobic biomass reactor. It was sampled before feeding, 6 h after feeding (disturbed)., at maximum gas production (healthy, 24 h), and after feedstock utilization (starved, 48h). Relative to the healthy condition, the disturbance of feeding significantly decreased eubacterial biomass and the proportion of unsaturated fatty acids, and increased branched fatty acids and the eubacterial stress biomarker,trans/cis 16: 17. The starved condition was not significantly different from the healthy in biomass or proportions of fatty acids, but did show a significant increase in the proportion of the eubacterial stress biomarkertrans/cis 18: 17. This reactor was compared to a second of the same design which had been overfed and showed significantly less productivity. The overfed reactor had a significantly lower methanogenic biomass,iso-branched fatty acids, and higher eubacterial stress markers Cy17:0 andtrans/cis 18: 17 than the highly productive reactor.     

Functional and structural analyses of trichloroethylene-degrading bacterial communities under different phenol-feeding conditions: laboratory experiments

The effects of different phenol-feeding conditions on trichloroethylene (TCE) biodegradation and bacterial population structure in an aquifer soil community were studied. The soil sample, minerals, phenol, and TCE were mixed in glass bottles, which were then incubated under three different phenol-feeding conditions. First, phenol was supplied only once at 0.2 mM (condition 0.2P); second, it was added at 2.0 mM (condition 2.0P); and third, it was periodically supplied ten times at 0.2 mM (condition 0.2PS). TCE concentrations remained stable under conditions 0.2P and 2.0P. In contrast, TCE was completely degraded under condition 0.2PS. TCE/phenol-degrading bacteria were enumerated indirectly and functionally by quantitative PCR. The low- K(s) (half saturation constant) group of phenol-degrading bacteria, exhibiting high TCE-degrading activity, yielded a 50-fold higher population under condition 0.2PS than under condition 2.0P. The bacterial community structure under condition 0.2PS was studied by denaturing gradient gel electrophoresis targeting the genes encoding 16S rRNA and the largest subunit of multicomponent phenol hydroxylase. Sequence analysis of the major bands detected indicated the predominance of the low- K(s) group of TCE/phenol-degrading bacteria belonging to beta-Proteobacteria. These results suggest that continuous supplementation with phenol at a low concentration increases the population of the low- K(s) group of TCE/phenol-degrading bacteria.     

Effects of aeration and organic loading rates on degradation of trichloroethylene in a methanogenic-methanotrophic coupled reactor

The effects of four aeration and four organic loading (OLR) rates on trichloroethylene (TCE) degradation in methanogenic-methanotrophic coupled reactors were studied using ethanol as the carbon source for the methanogens. Microcosm and PCR studies demonstrated that methanotrophs capable of mineralizing TCE and methanogens were present in the biomass throughout the study. The gene for the particulate form of methane monooxygenase (pMMO) was detected by PCR, but not that for the soluble form (sMMO). TCE mineralization by methanotrophs was therefore due primarily to pMMO activity. Low TCE concentrations were measured in effluent and off-gas samples in all cases. Volatilization losses were 0-5%. Dichloroethylene (DCE) was also observed, but vinyl chloride and ethylene were never detected. Changes in the aeration rate had no effect on TCE removal, but did influence DCE degradation. Reductive dechlorination of TCE to DCE was favored at low and no-aeration conditions, and DCE accumulation occurred due to slow DCE degradation. Low DCE levels were observed at the higher aeration rates, which indicated that conditions in these reactors were amenable to the aerobic co-metabolism of TCE and DCE. The OLR did have an effect on TCE removal. TCE and DCE removal were negatively affected when the OLR was increased. An OLR of 0.3 g COD l(rx)(-1)day(-1) or lower with an aeration rate of 3 l(O2 )l(rx)(-1)day(-1) and higher is the recommended operating condition of a coupled reactor for removal of TCE.     

Performance of the anaerobic baffled reactor under steady-state and shock loading conditions

The anaerobic baffled reactor (ABR) contains a granulated, mixed anaerobic culture segregated into compartments. Operation of four reactors under a range of hydraulic retention times showed that this novel reactor design offers highly efficient performance in the conversion of carbon in the feed stream to methane and carbon dioxide. The design parameter varied was the number of compartments. COD removal at 20 h retention time was routinely over 95% in all reactors, with low washout of biomass. Very high specific reaction rates were achievable (although with a loss of efficiency) at low biomass concentrations and high loading rates. In order to optimize volumetric reaction rates, a tradeoff has to be made between high biomass concentration, granule size, and the resulting mass transfer limitations. Formate is shown to be an important intermediate in the process under conditions of high loading.     

Degradation of phenol and benzoic acid in a three-phase fluidized-bed reactor

Degradation of phenol and benzoic acid was studied in a fluidized-bed reactor (liquid volume 2.17 L) under nonsterile conditions with special emphasis on maximizing the flow through the reactor and investigating reactor performance at fluctuating feeds. Reactor response to substrate pulses was investigated by applying substrate square-wave inputs at a liquid flow of 1.00 L h(-1). A twofold increase of the phenol and benzoic acid feed concentrations for 2.5 h did not lead to accumulation and breakthrough. The cells were able to survive four to fivefold increases of the feed concentration for 1 h without loss of viability, although the phenol pulse lead to phenol accumulation in the reactor. Reactor performance at constantly fluctuating loads was investigated by varying the feed concentrations using sine wave functions. No accumulation of phenol or benzoic acid was observed. Influence of induction was studied using shift experiments. After 35 days of operation (369 hydrodynamic residence times) with phenol as sole substrate (carbon source) the reactor was able to mineralize benzoic acid without any adaptation or lag phase. The capability of phenol degradation, on the other hand, was lost by most cells after only 3 days operation with benzoic acid as the sole substrate. The experiments underline the importance of induction. In order to maximize the flow through the reactor, the liquid flow was increased stepwise while the feed concentrations were reduced correspondingly, keeping the volumetric conversion rates of phenol (0.24 g L(-1) h(-1)) and benzoic acid (0.17 g L(-1) h(-1)) constant. By this means, liquid flow could be increased up to 13.32 L h(-1), which was more than 20-fold higher than the maximum liquid flow achievable in a chemostat using the same conditions.     

Hybrid Cavitation/Constructed Wetland Reactors for Treatment of Chlorinated and Non‐Chlorinated Organics

Mitigation strategies can be implemented to decrease chlorinated and non‐chlorinated organic exposures to biota of aquatic receiving systems thereby reducing associated risks. In this work, we investigated the concept of coupling a physical/chemical reactor (i.e. a cavitation reactor) with a biological reactor (i.e. a constructed wetland) in an effort to efficiently transform PCE, TCE, and petroleum in freshwater into non‐toxic chemical forms or concentrations. Rates of TCE degradation due to cavitation ranged from 0.010 to 0.026 min^‐1 with corresponding half‐lives of 69 to 27 min. Compared to controls, degradation of petroleum in water by cavitation was not detected in these experiments. After treatment in anaerobic wetland reactors, TCE and PCE decreased by more than 99 % under two flow regimes (5‐d and 20‐d HRT). In reciprocating constructed wetland reactors receiving petroleum, mean COD, BOD₅, and total Zn decreased by 90.0, 88.8, and 86.8 %, respectively, in wetland outflows compared to the initial conditions (96‐h HRT). Percent survival (96‐h) of D. magna and P. promelas increased from zero percent in initial conditions to 80.1 (± 18.9) and 80.0 (± 21.4) %, respectively, after treatment in the constructed wetland reactors. The experimental results obtained in the laboratory‐scale set‐up and the theoretical model for the hybrid reactor concept will be used to obtain the intrinsic kinetic coefficients for the appropriate reactors. This kinetic information will be used to scale‐up the hybrid reactor model concept for the same level of pollutant removal.     

采煤沉陷区不同造林树种恢复土壤酚酸物质对土壤微生物的影响

酚酸物质是影响微生物群落和结构的最重要因子之一,研究酚酸物质在不同造林树种土壤中的变化规律及其与微生物群落结构的关系,有助于更好地了解和揭示采煤沉陷区恢复造林条件下微生物群落变化的机制.本研究在双鸭山宝山采煤沉陷区的撂荒地基础上营造三针一阔(红松、落叶松、樟子松和杨树)人工林,测定这4种造林地土壤酚类物质、11种酚酸物质和微生物群落结构.结果表明: 复合态酚含量总体表现为人工林显著高于撂荒地,其中,落叶松人工林和杨树人工林的复合态酚含量较高,落叶松人工林和红松人工林的总酚含量显著高于撂荒地,红松人工林的水溶性酚含量显著高于撂荒地;在11种酚酸物质中,阿魏酸、松香酸、β-谷甾醇、齐墩果酸、莽草酸、亚油酸和硬脂酸的含量在人工林土壤中较高.土壤酚类物质与土壤微生物生物量不存在显著的相关关系,个别的酚酸物质与土壤微生物的相关关系显著,其中,阿魏酸、松香酸和β-谷甾醇对土壤微生物生物量有明显的促进作用,与真菌和真菌/细菌存在显著的正相关关系.杨树人工林的酚酸物质含量较高,说明营造杨树人工林对采煤沉陷区的土壤恢复有益.     

Using electron balances and molecular techniques to assess trichoroethene-induced shifts to a dechlorinating microbial community

This study demonstrated the utility in correlating performance and community structure of a trichloroethene (TCE)-dechlorinating microbial consortium; specifically dechlorinators, fermenters, homoacetogens, and methanogens. Two complementary approaches were applied: predicting trends in the microbial community structure based on an electron balance analysis and experimentally assessing the community structure via pyrosequencing and quantitative polymerase chain reaction (qPCR). Fill-and-draw reactors inoculated with the DehaloR^2 consortium were operated at five TCE-pulsing rates between 14 and 168 μmol/10-day-SRT, amended with TCE every 2 days to give peak concentrations between 0.047 and 0.56 mM (6-74 ppm) and supplied lactate and methanol as sources of e(-) donor and carbon. The complementary approaches demonstrated the same trends: increasing abundance of Dehalococcoides and Geobacter and decreasing abundance of Firmicutes with increasing TCE pulsing rate, except for the highest pulsing rate. Based on qPCR, the abundance of Geobacter and Dehalococcoides decreased for the highest TCE pulsing rate, and pyrosequencing showed this same trend for the latter. This deviation suggested decoupling of Dehalococcoides growth from dechlorination. At pseudo steady-state, methanogenesis was minimal for all TCE pulsing rates. Pyrosequencing and qPCR showed suppression of the homoacetogenic genera Acetobacterium at the two highest pulsing rates, and it was corroborated by a decreased production of acetate from lactate fermentation and increased propionate production. Suppression of Acetobacterium, which can provide growth factors to Dehalococcoides, may have contributed to the decoupling for the highest TCE-pulsing rate.     

Treatment of Cresol, Phenol and Formalin using Fixed-film Reactors

The degradability of phenol, cresol and formalin, separately or in mixtures, was studied in a laboratory-scale, submerged fixed-film reactor and in a prototype trickling-tower plant with recirculation of aerated effluent. The rates of degradation could be increased by 10–15 times by acclimating the reactors to increasing concentrations of disinfectants in the feed increasing daily from 10 to 1000 mg/1. After acclimation, detectable levels of disinfectants were only found in the liquor of the batch-operated fixed-film reactor after 24 h when the concentration of the daily dose exceeded 1100–1500 mg/1 and in the continuously-fed trickling tower plant, when the feed concentration exceeded 1500 mg/1. It was possible in the reactor to treat cresol efficiently after acclimation to formalin and vice versa. Acclimation was shown to reduce diversity of bacterial species, the dominant isolates being Pseudomonos aeruginosa and other pseudomonads.     

Effect of non-feeding period length on the intermittent operation of UASB reactors treating dairy effluents

Recent environmental concerns have prompted a re-evaluation of conventional management strategies and refueled the search of innovative waste management practices. In this sense, the anaerobic digestion of both fat and the remaining complex organic matter present in dairy wastewaters is attractive, although the continuous operation of high rate anaerobic processes treating this type of wastewaters causes the failure of the process. This work accesses the influence of non-feeding period length on the intermittent operation of mesophilic UASB reactors treating dairy wastewater, in order to allow the biological degradation to catch up with adsorption phenomenon. During the experiments, two UASB reactors were subject to three organic loading rates, ranging from 6 to 12 g(COD) x L(-1) x d(-1), with the same daily load applied to both reactors, each one with a different non-feeding period. Both reactors showed good COD removal efficiencies (87-92%). A material balance for COD in the reactors during the feeding and non-feeding periods showed the importance of the feedless period, which allowed the biomass to degrade substrate that was accumulated during the feeding period. The reactor with the longest non-feeding period had a better performance, which resulted in a higher methane production and adsorption capacity for the same organic load applied with a consequent less accumulation of substrate into the biomass. In addition, both reactors had a stable operation for the organic load of 12 g(COD) x L(-1) x d(-1), which is higher than the maximum applicable load reported in literature for continuous systems (3-6 g(COD) x L(-1) x d(-1)).