Jonathan G. Pressman

Methanotrophic biodegradation of trichloroethylene in a hollow fiber membrane bioreactor.

Biodegradation of trichloroethlyene (TCE) in a hollow fiber membrane bioreactor was investigated using a mutant of the methanotrophic bacteria, Methylosinus trichosporium OB3b. Contaminated water flowed through the lumen (i.e., fiber interior), and the bacteria circulated through the shell side of the membrane module and an external growth reactor. In mass transfer studies with a radial cross-flow membrane module, 78.3-99.9% of the TCE was removed from the lumen at hydraulic residence times of 3-15 min in the lumen and the shell. In biodegradation experiments, 80-95% of the TCE was removed from the lumen at hydraulic residence times of 5-9 min in the lumen. The TCE transferred to the shell was rapidly biodegraded, with rate constants ranging from 0.16 to 0.9 L (mg of TSS) -1 day -1 . Radiochemical data showed that over 75% of the transferred TCE was biodegraded in the shell, with the byproducts being approximately equally divided between carbon dioxide and nonvolatiles. This study shows that a hollow fiber membrane bioreactor system coupled with the mutant strain PP358 of M. trichosporium OB3b is a very promising technology for chlorinated solvent biodegradation.

Free Chlorine and Monochloramine Application to Nitrifying Biofilm: Comparison of Biofilm Penetration, Activity, and Viability

Biofilm in drinking water systems is undesirable. Free chlorine and monochloramine are commonly used as secondary drinking water disinfectants, but monochloramine is perceived to penetrate biofilm better than free chlorine. However, this hypothesis remains unconfirmed by direct biofilm monochloramine measurement. This study compared free chlorine and monochloramine biofilm penetration into an undefined mixed-culture nitrifying biofilm by use of microelectrodes and assessed the subsequent effect on biofilm activity and viability by use of dissolved oxygen (DO) microelectrodes and confocal laser scanning microscopy (CLSM) with LIVE/DEAD BacLight. For equivalent chlorine concentrations, monochloramine initially penetrated biofilm 170 times faster than free chlorine, and even after subsequent application to a monochloramine penetrated biofilm, free chlorine penetration was limited. DO profiles paralleled monochloramine profiles, providing evidence that either the biofilm was inactivated with monochloramines penetration or its persistence reduced available substrate (free ammonia). While this research clearly demonstrated monochloramines greater penetration, this penetration did not necessarily translate to immediate viability loss. Even though free chlorines penetration was limited compared to that of monochloramine, it more effectively (on a cell membrane integrity basis) inactivated microorganisms near the biofilm surface. Limited free chlorine penetration has implications when converting to free chlorine in full-scale chloraminated systems in response to nitrification episodes.

Monochloramine Disinfection Kinetics of Nitrosomonas europaea by Propidium Monoazide Quantitative PCR and Live/Dead BacLight Methods

ABSTRACT Monochloramine disinfection kinetics were determined for the pure-culture ammonia-oxidizing bacterium Nitrosomonas europaea (ATCC 19718) by two culture-independent methods, namely, Live/Dead BacLight (LD) and propidium monoazide quantitative PCR (PMA-qPCR). Both methods were first verified with mixtures of heat-killed (nonviable) and non-heat-killed (viable) cells before a series of batch disinfection experiments with stationary-phase cultures (batch grown for 7 days) at pH 8.0, 25°C, and 5, 10, and 20 mg Cl2/liter monochloramine. Two data sets were generated based on the viability method used, either (i) LD or (ii) PMA-qPCR. These two data sets were used to estimate kinetic parameters for the delayed Chick-Watson disinfection model through a Bayesian analysis implemented in WinBUGS. This analysis provided parameter estimates of 490 mg Cl2-min/liter for the lag coefficient (b) and 1.6 × 10−3 to 4.0 × 10−3 liter/mg Cl2-min for the Chick-Watson disinfection rate constant (k). While estimates of b were similar for both data sets, the LD data set resulted in a greater k estimate than that obtained with the PMA-qPCR data set, implying that the PMA-qPCR viability measure was more conservative than LD. For N. europaea, the lag phase was not previously reported for culture-independent methods and may have implications for nitrification in drinking water distribution systems. This is the first published application of a PMA-qPCR method for disinfection kinetic model parameter estimation as well as its application to N. europaea or monochloramine. Ultimately, this PMA-qPCR method will allow evaluation of monochloramine disinfection kinetics for mixed-culture bacteria in drinking water distribution systems.

Demonstration of efficient trichloroethylene biodegradation in a hollow-fiber membrane bioreactor

Rapid cometabolism of trichloroethylene (TCE) by pure cultures of Methylosinus trichosporium OB3b PP358 was demonstrated in a two-stage hollow-fiber membrane bioreactor over the course of 3 weeks. PP358 was grown in a continuous-flow chemostat and circulated through the shell of a hollow-fiber membrane module (HFMM), while TCE contaminated water (160 to 1450 micrograms/L) was pumped through the fiber lumen (fiber interior). In parallel-flow HFMM biological experiments, 82% to 89% of the influent TCE was removed from the lumen (5.1-min residence time) with 99% of the transferred TCE undergoing biodegradation. Biological experiments in a larger capacity baffled radial-flow HFMM resulted in 66% to 99% TCE transferred and 93% to 96% TCE biodegradation at lumen residence times of between 1.5 and 3.7 min. Biodegradation was maintained throughout the experiments at pseudo-first-order biodegradation rate constants of 0.41 to 2.8 L/mg TSS/day. Best-fit computer modeling of the baffled radial-flow biological process estimated mass transfer coefficients as large as 2.7 x 10(-2) cm/min. The computer model was also shown to simulate the experimental results quite well.

A hollow-fiber membrane bioreactor for the removal of trichloroethylene from the vapor phase

A hollow‐fiber membrane bioreactor was used to separate trichloroethylene (TCE) from a gaseous waste stream with subsequent cometabolic biodegradation by a pure culture of Methylosinus trichosporium OB3b PP358. The two‐stage bioreactor system was successfully operated for 20 days. PP358 was grown in a continuous‐flow chemostat and circulated through the fiber lumen of a hollow‐fiber membrane module (HFMM), while TCE contaminated air (141 to 191 μg/L) was pumped through the HFMM shell. Between 54% –84% TCE transfer and 92%–96% TCE cometabolism were obtained in the HFMM reactor loop. Short shell‐residence times, 1.6 to 5.0 minutes, demonstrated quick throughput of TCE contaminated air. Best‐fit computer modeling of the biological experiments estimated mass transfer coefficients between 2.0 × 10−3 cm/min and 5.6 × 10−3 cm/min. The average pseudo‐first‐order biodegradation rate constant for the biological experiments was 0.46 L/mg TSS/d. These results demonstrate that the hollow‐fiber membrane bioreactor represents an attractive technology for the bioremediation of gaseous waste streams.

Developmental Toxicity Evaluations of Whole Mixtures of Disinfection By-products using Concentrated Drinking Water in Rats: Gestational and Lactational Effects of Sulfate and Sodium

A developmental toxicity bioassay was used in three experiments to evaluate water concentrates for suitability in multigenerational studies. First, chlorinated water was concentrated 135-fold by reverse osmosis; select lost disinfection by-products were spiked back. Concentrate was provided as drinking water to Sprague-Dawley and F344 rats from gestation day 6 to postnatal day 6. Maternal serum levels of luteinizing hormone on gestation day 10 were unaffected by treatment for both strains. Treated dams had increased water consumption, and increased incidences of polyuria, diarrhea, and (in Sprague-Dawley rats) red perinasal staining. Pup weights were reduced. An increased incidence of eye defects was seen in F344 litters. Chemical analysis of the concentrate revealed high sodium (6.6 g/l) and sulfate (10.4 g/l) levels. To confirm that these chemicals caused polyuria and osmotic diarrhea, respectively, Na₂SO₄ (5-20 g/l) or NaCl (16.5 g/l) was provided to rats in drinking water. Water consumption was increased at 5- and 10-g Na₂SO₄/l and with NaCl. Pup weights were reduced at 20-g Na₂SO₄/l. Dose-related incidences and severity of polyuria and diarrhea occurred in Na₂SO₄-treated rats; perinasal staining was seen at 20 g/l. NaCl caused polyuria and perinasal staining, but not diarrhea. Subsequently, water was concentrated ∼120-fold and sulfate levels were reduced by barium hydroxide before chlorination, yielding lower sodium (≤1.5 g/l) and sulfate (≤2.1 g/l) levels. Treatment resulted in increased water consumption, but pup weight and survival were unaffected. There were no treatment-related clinical findings, indicating that mixtures produced by the second method are suitable for multigenerational testing.

Biofilm Community Dynamics in Bench-Scale Annular Reactors Simulating Arrestment of Chloraminated Drinking Water Nitrification

Annular reactors (ARs) were used to study biofilm community succession and provide ecological insight during nitrification arrestment through simultaneously increasing monochloramine (NH2Cl) and chlorine to nitrogen mass ratios, resulting in four operational periods (I-IV). Analysis of 16S rRNA-encoding gene sequence reads (454-pyrosequencing) examined viable and total biofilm communities and found total samples were representative of the underlying viable community. Bacterial community structure showed dynamic changes corresponding with AR operational parameters. Period I (complete nitrification and no NH2Cl residual) was dominated by Bradyrhizobium (total cumulative distribution: 38%), while environmental Legionella-like phylotypes peaked (19%) during Period II (complete nitrification and minimal NH2Cl residual). Nitrospira moscoviensis (nitrite-oxidizing bacteria) was detected in early periods (2%) but decreased to <0.02% in later periods, corresponding to nitrite accumulation. Methylobacterium (19%) and members of Nitrosomonadaceae (42%) dominated Period III (complete ammonia and partial nitrite oxidation and low NH2Cl residual). An increase in Afipia (haloacetic acid-degrading bacteria) relative abundance (<2% to 42%) occurred during Period IV (minimal nitrification and moderate to high NH2Cl residual). Microbial community and operational data provided no evidence of taxa-time relationship, but rapid community transitions indicated that the system had experienced ecological regime shifts to alternative stable states.

Novel thermally stable poly(vinyl chloride) composites for sulfate removal

BaCO(3) dispersed PVC composites were prepared through a polymer re-precipitation method. The composites were tested for sulfate removal using rapid small scale column test (RSSCT) and found to significantly reduce sulfate concentration. The method was extended to synthesize barium carbonate-loaded silica aero-gels-polyvinyl chloride (PVC) polymer composites. The PVC composites were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray mapping, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS) analysis. The method has advantages over conventional sulfate precipitation (sulfate removal process) using BaCO(3) wherein clogging of the filter can be avoided. The method is environmentally friendly and does not interfere with natural organic matter as the conventional resin does. Some of the composites were thermally more stable as compared with the pure PVC discussed in the literature.

Disinfection byproduct formation in reverse-osmosis concentrated and lyophilized natural organic matter from a drinking water source.

Drinking water treatment and disinfection byproduct (DBP) research can be complicated by natural organic matter (NOM) temporal variability. NOM preservation by lyophilization (freeze-drying) has been long practiced to address this issue; however, its applicability for drinking water research has been limited because the selected NOM sources are atypical of most drinking water sources. The purpose of this research was to demonstrate that reconstituted NOM from a lyophilized reverse-osmosis (RO) concentrate of a typical drinking water source closely represents DBP formation in the original NOM. A preliminary experiment assessed DBP formation kinetics and yields in concentrated NOM, which demonstrated that chlorine decays faster in concentrate, in some cases leading to altered DBP speciation. Potential changes in NOM reactivity caused by lyophilization were evaluated by chlorination of lyophilized and reconstituted NOM, its parent RO concentrate, and the source water. Bromide lost during RO concentration was replaced by adding potassium bromide prior to chlorination. Although total measured DBP formation tended to decrease slightly and unidentified halogenated organic formation tended to increase slightly as a result of RO concentration, the changes associated with lyophilization were minor. In lyophilized NOM reconstituted back to source water TOC levels and then chlorinated, the concentrations of 19 of 21 measured DBPs, constituting 96% of the total identified DBP mass, were statistically indistinguishable from those in the chlorinated source water. Furthermore, the concentrations of 16 of 21 DBPs in lyophilized NOM reconstituted back to the RO concentrate TOC levels, constituting 86% DBP mass, were statistically indistinguishable from those in the RO concentrate. This study suggests that lyophilization can be used to preserve concentrated NOM without substantially altering the precursors to DBP formation.

Resilience of microbial communities in a simulated drinking water distribution system subjected to disturbances: role of conditionally rare taxa and potential implications for antibiotic-resistant bacteria

Many US water utilities using chloramine as their secondary disinfectant have experienced nitrification episodes that detrimentally impact water quality in their distribution systems. A semi-closed pipe-loop chloraminated drinking water distribution system (DWDS) simulator was used to evaluate the biological stability of the system and describe the response of microbial communities in the bulk water (BW) and biofilm (BF) phase to a disturbance caused by changes in the operational parameters. The DWDS simulator was operated through five successive operational schemes, including an episode of nitrification, followed by a ‘chlorine burn’ by switching the disinfectant from chloramine to free chlorine. Community comparisons showed significant differences in the structure based on disinfectant and phase (e.g., BW and BF). Both disturbances created changes in the relative abundances of the core microbiome and some members of the rare biosphere (i.e., conditionally rare taxa); however, the microbial community was resilient and returned to its stable state. Genes associated with multiple antibiotic resistance mechanisms were found to be a component of the core genomes of waterborne isolates. These results provide evidence of variations in the bulk water/biofilm microbial community structure during episodes of disturbance (e.g., disinfectant switching practices, nitrification) and its recovery after disturbance.