Performance analysis of three pilot-scale multi-compartment anaerobic baffled reactors treating domestic wastewater at psychrophilic temperatures in Colorado.

A transition from inefficient aerobic wastewater treatment methods to sustainable approaches is needed. Anaerobic bioreactors are a viable solution as they consume less energy, reduce biosolid production, and provide a source of renewable methane-rich biogas. A barrier to widespread implementation of anaerobic technologies is the lack of design guidance, especially in colder climates. This study bridges this knowledge gap by deriving design principles from three long-running pilot-scale anaerobic baffled reactors (ABRs) operating under psychrophilic conditions. The ABRs removed an average of 56% and 80% chemical oxygen demand (COD) and suspended solids, respectively, with a methane yield of 0.21 L CH4 /g CODrem . Methane production may be improved with increased influent sCOD concentrations and decreased sulfate concentrations. Results suggest that ABRs can treat a range of wastewater strengths accompanied by useable methane production. Despite sharing location, temperature, and HRT, the ABRs displayed distinct performances, highlighting the significance of influent wastewater characteristics. PRACTITIONER POINTS: ABRs achieved 56% and 80% removal efficiencies for COD and suspended solids. Average biogas was 63% methane, and methane yield was 0.21 L CH4 /g CODrem . Volumetric methane production was positively correlated with the influent sCOD/sulfate ratio and negatively correlated with influent sulfate loading.

Evidence for Biotic Perchlorate Reduction in Naturally Perchlorate-Rich Sediments of Pilot Valley Basin, Utah.

The presence of perchlorate on Mars suggests a possible energy source for sustaining microbial life. Perchlorate-reducing microbes have been isolated from perchlorate-contaminated soils and sediments on the Earth, but to date, never from an environment that is naturally enriched in perchlorate. The arid Pilot Valley paleolake basin in Utah is a Mars analog environment whose sediments are naturally enriched with up to ∼6.5 µg kg-1 perchlorate oxyanions. Here, we present results of field and laboratory studies indicating that perchlorate-reducing microorganisms co-occur with this potential electron acceptor. Biogeochemical data suggest ongoing perchlorate reduction; phylogenetic data indicate the presence of diverse microbial communities; and laboratory enrichments using Pilot Valley sediments show that resident microbes can reduce perchlorate. This is the first article of the co-existence of perchlorate-reducing microbes in an environment where perchlorate occurs naturally, arguing for Pilot Valley's utility as an analog for studying biogeochemical processes that may have occurred, and may yet still be occurring, in ancient martian lacustrine sediments.

Lifecycle Comparison of Mainstream Anaerobic Baffled Reactor and Conventional Activated Sludge Systems for Domestic Wastewater Treatment.

The objective of this study was to evaluate the lifecycle impacts of anaerobic primary treatment of domestic wastewater using anaerobic baffled reactors (ABRs) coupled with aerobic secondary treatment relative to conventional wastewater and sludge/biosolids treatment systems through the application of wastewater treatment modeling and three lifecycle-based analyses: environmental lifecycle assessment, net energy balance, and lifecycle costing. Data from two pilot-scale ABRs operated under ambient wastewater temperatures were used to model the anaerobic primary treatment process. To address uncertain parameters in the scale-up of pilot-scale anaerobic reactor data, uncertainty analysis and Monte Carlo simulation were employed. This study demonstrates that anaerobic primary treatment of domestic wastewater using ABRs can be incorporated with existing aerobic treatment strategies to reduce aeration demand, reduce sludge production, and increase energy generation. The net result of coupling anaerobic primary treatment with aerobic secondary treatment is a more favorable net energy balance, reduced environmental impacts in most examined categories, and lower lifecycle costs relative to conventional treatment configurations; however, the removal and/or capture of dissolved methane is required to reduce global warming impacts and increase on-site energy generation. With further study, anaerobic primary treatment can be a path forward for energy-positive wastewater treatment.

Statistical Exposé of a Multiple-Compartment Anaerobic Reactor Treating Domestic Wastewater.

Mainstream anaerobic treatment of domestic wastewater is a promising energy-generating treatment strategy; however, such reactors operated in colder regions are not well characterized. Performance data from a pilot-scale, multiple-compartment anaerobic reactor taken over 786 days were subjected to comprehensive statistical analyses. Results suggest that chemical oxygen demand (COD) was a poor proxy for organics in anaerobic systems as oxygen demand from dissolved inorganic material, dissolved methane, and colloidal material influence dissolved and particulate COD measurements. Additionally, univariate and functional boxplots were useful in visualizing variability in contaminant concentrations and identifying statistical outliers. Further, significantly different dissolved organic removal and methane production was observed between operational years, suggesting that anaerobic reactor systems may not achieve steady-state performance within one year. Last, modeling multiple-compartment reactor systems will require data collected over at least two years to capture seasonal variations of the major anaerobic microbial functions occurring within each reactor compartment.

Resuscitation of starved suspended- and attached-growth anaerobic ammonium oxidizing bacteria with and without acetate.

Anammox application for nutrient removal from wastewater is increasing, though questions remain about anammox resilience to fluctuating conditions. Resuscitation of anammox suspended- and attached-growth cultures after 3 months of starvation was studied with and without acetate dosing. Without acetate, the attached-growth culture recovered more quickly than the suspended-growth culture. Suspended-growth cultures recovered more quickly (within 60 days) with weekly and daily acetate dosing than without, but anammox activity and copy numbers decreased with continued acetate addition. All attached-growth cultures recovered within 60 days, but after that activity with acetate dosing was consistently at least 20% lower than that without acetate addition. Ca. Jettenia caeni, Ca. Anammoxoglobus sp., Ca. Brocadia fulgida, Ca. Brocadia anammoxidans, Ca. Brocadia fulgida and Ca. Jettenia asiatica were identified. Acetate addition can significantly accelerate short-term resuscitation of enriched anammox suspended-growth cultures after starvation but may reduce anammox activity over the longer term in suspended- and attached-growth cultures.

Disturbance opens recruitment sites for bacterial colonization in activated sludge.

Little is known about the role of immigration in shaping bacterial communities or the factors that may dictate success or failure of colonization by bacteria from regional species pools. To address these knowledge gaps, the influence of bacterial colonization into an ecosystem (activated sludge bioreactor) was measured through a disturbance gradient (successive decreases in the parameter solids retention time) relative to stable operational conditions. Through a DNA sequencing approach, we show that the most abundant bacteria within the immigrant community have a greater probability of colonizing the receiving ecosystem, but mostly as low abundance community members. Only during the disturbance do some of these bacterial populations significantly increase in abundance beyond background levels and in few cases become dominant community members post-disturbance. Two mechanisms facilitate the enhanced enrichment of immigrant populations during disturbance: (i) the availability of resources left unconsumed by established species and (ii) the increased availability of niche space for colonizers to establish and displace resident populations. Thus, as a disturbance decreases local diversity, recruitment sites become available to promote colonization. This work advances our understanding of microbial resource management and diversity maintenance in complex ecosystems.

Identification and quantification of bacteria and archaea responsible for ammonia oxidation in different activated sludge of full-scale wastewater treatment plants.

In this study, the abundance and sequences of the amoA gene in ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) were defined in three wastewater treatment plants using activated sludge with biological nitrogen removal in different countries: Thailand, United States of America (USA), and Japan. Quantitative real-time polymerase chain reaction (PCR) and PCR coupled with denaturing gradient gel electrophoresis were used to find the comparative abundance and identity of AOB and AOA. The conditions at the Phuket WWTP in Thailand promoted the dominance of AOA amoA genes over AOB amoA genes, while conditions at the WWTPs in Japan and USA promoted growth of AOB. Three parameters that may have contributed to the AOA dominance in Phuket were longer SRT, higher temperature, and higher pH. The Phuket WWTP is a unique system that can be used to better understand the conditions that promote AOA growth and dominance over AOB. In addition, analysis of operational data in conjunction with AOA and AOB community structure from the Phuket WWTP may elucidate advantages of AOA in meeting stricter treatment standards.

Disturbance and temporal partitioning of the activated sludge metacommunity.

The resilience of microbial communities to press disturbances and whether ecosystem function is governed by microbial composition or by the environment have not been empirically tested. To address these issues, a whole-ecosystem manipulation was performed in a full-scale activated sludge wastewater treatment plant. The parameter solids retention time (SRT) was used to manipulate microbial composition, which started at 30 days, then decreased to 12 and 3 days, before operation was restored to starting conditions (30-day SRT). Activated sludge samples were collected throughout the 313-day time series in parallel with bioreactor performance ('ecosystem function'). Bacterial small subunit (SSU) rRNA genes were surveyed from sludge samples resulting in a sequence library of >417,000 SSU rRNA genes. A shift in community composition was observed for 12- and 3-day SRTs. The composition was altered such that r-strategists were enriched in the system during the 3-day SRT, whereas K-strategists were only present at SRTs⩾12 days. This shift corresponded to loss of ecosystem functions (nitrification, denitrification and biological phosphorus removal) for SRTs⩽12 days. Upon return to a 30-day SRT, complete recovery of the bioreactor performance was observed after 54 days despite an incomplete recovery of bacterial diversity. In addition, a different, yet phylogenetically related, community with fewer of its original rare members displaced the pre-disturbance community. Our results support the hypothesis that microbial ecosystems harbor functionally redundant phylotypes with regard to general ecosystem functions (carbon oxidation, nitrification, denitrification and phosphorus accumulation). However, the impacts of decreased rare phylotype membership on ecosystem stability and micropollutant removal remain unknown.

Analysis of sources of bulk conductivity change in saturated silica sand after unbuffered TCE oxidation by permanganate.

Time lapse resistivity surveys could potentially improve monitoring of permanganate-based in situ chemical oxidation (ISCO) of organic contaminants such as trichloroethene (TCE) by tracking changes in subsurface conductivity that result from injection of permanganate and oxidation of the contaminant. Bulk conductivity and pore fluid conductivity changes during unbuffered TCE oxidation using permanganate are examined through laboratory measurements and conductivity modeling using PHREEQC in fluid samples and porous media samples containing silica sand. In fluid samples, oxidation of one TCE molecule produces three chloride ions and one proton, resulting in an increase in fluid electrical conductivity despite the loss of two permanganate ions in the reaction. However, in saturated sand samples in which up to 8mM TCE was oxidized, at least 94% of the fluid conductivity associated with the presence of protons was removed within 3h of sand contact, most likely through protonation of silanol groups found on the surface of the sand grains. Minor conductivity effects most likely associated with pH-dependent reductive dissolution of manganese dioxide were also observed but not accounted for in pore-fluid conductivity modeling. Unaccounted conductivity effects resulted in an under-calculation of post-reaction pore fluid conductivity of 2.1% to 5.5%. Although small increases in the porous media formation factor resulting from precipitation of manganese dioxide were detected (about 3%), these increases could not be confirmed to be statistically significant. Both injection of permanganate and oxidation of TCE cause increases in bulk conductivity that would be detectable through time-lapse resistivity surveys in field conditions.

Comparison of nitrogen removal rates and nitrous oxide production from enriched anaerobic ammonium oxidizing bacteria in suspended and attached growth reactors.

Attached growth-systems for the anaerobic ammonium oxidation (anammox) process have been postulated for implementation in the field. However, information about the anammox process in attached growth-systems is limited. This study compared nitrogen removal rates and nitrous oxide (N2O) production of enriched anammox cultures in both suspended and attached growth sequencing batch reactors (SBRs). Suspended growth reactors (SBR-S) and attached growth reactors using polystyrene sponge as a medium (SBR-A) were used in these experiments. After inoculation with an enriched anammox culture, significant nitrogen removals of ammonium (NH4 (+)) and nitrite (NO2 (-)) were observed under NH4 (+):NO2 (-) ratios ranging from 1:1 to 1:2 in both types of SBRs. The specific rates of total nitrogen removal in SBR-S and SBR-A were 0.52 mg N/mg VSS-d and 0.44 mg N/mg VSS-d, respectively, at an NH4 (+):NO2 (-) ratio of 1:2. N2O production by the enriched anammox culture in both SBR-S and SBR-A was significantly higher at NH4 (+):NO2 (-) ratio of 1:2 than at NH4 (+):NO2 (-) ratios of 1:1 and 1:1.32. In addition, N2O production was higher at a pH of 6.8 than at pH 7.3, 7.8, and 8.3 in both SBR-S and SBR-A. The results of this investigation demonstrate that the anammox process may avoid N2O emission by maintaining an NH4 (+):NO2 (-) ratio of less than 1:2 and pH higher than 6.8.

Identifying well contamination through the use of 3-D fluorescence spectroscopy to classify coalbed methane produced water.

Production of unconventional gas resources commonly requires the use of hydraulic fracturing and chemical production well additives. Concern exists for the use of chemical compounds in gas wells due to the risk of groundwater contamination. This study focuses on a proposed method of identifying groundwater contamination from gas production. The method focuses on the classification of naturally occurring organic signatures of coalbed methane (CBM) produced water compared to anthropogenic organic compounds. The 3-D fluorescence excitation-emission matrix (EEM) spectra of coalbed methane produced water samples revealed four peaks characteristic of coalbed methane produced water: Peak P (aromatic proteins region), Peak M(1) (microbial byproducts region), Peak M(2) (microbial byproducts region), and Peak H (humic acid-like region). Peak H is characteristic of the coal-water equilibria present in all basins, while peaks P and M(2) correlate with microbial activity in basins with biogenic methane generation pathways. Anthropogenic well additives produce EEM signatures with notable flooding of peaks P, M(1), M(2), and H, relatively higher overall fluorescence intensity, and slightly higher DOC concentrations. Fluorescence spectroscopy has the potential to be used in conjunction with groundwater contamination studies to determine if detected organic compounds originate from naturally occurring sources or well production additives.

The effect of system variables on in situ sweep-efficiency improvements via viscosity modification.

Laboratory experiments and numerical simulations were performed to critically evaluate the utility of viscosity modification as a technique to improve injected fluid sweep efficiencies within texturally heterogeneous geomedia. The objective of this technique is to improve the subsurface distribution of fluids by mitigating the potential for preferential flow and bypassing of lower permeability media that can limit the effectiveness of in situ remediation applications. The results of two-dimensional sand tank experiments and numerical simulations demonstrate that viscosity modification, via polymer amendment, can improve sweep efficiencies within layered heterogeneous structures by up to 90%, relative to the no-polymer case. The amount of sweep efficiency improvement depended on a number of system variables, including: the degree of layering, the relative positioning of layers within the system, the permeability contrast between layers, fluid viscosity, and the rheological character of the fluid utilized. Although significant sweep-efficiency improvement was observed, achieving 100% sweep in one pore volume was only possible when the permeability contrast was less than a factor of four, regardless of the viscosity and the rheological character of the fluid.

Effects of oxytetracycline on anammox activity.

Batch experiments were conducted to investigate the effects of oxytetracycline on anaerobic ammonium oxidation (anammox) process. The short-and long-term effects on anammox activity were studied by measuring ammonium (NH(4)(+)), nitrite (NO(2)(-)), and nitrate (NO(3)(-)) concentrations over time. Experiments were conducted at NH(4)(+)and NO(2)(-) concentrations of 60-90 mg N/L and 60-190 mg N/L, respectively (NH(4)(+):NO(2)(-) ratio from 1:1-1:2.25), oxytetracycline concentrations of 10-100 mg/L, and biomass concentrations of 300-800 mg/L. In the short-term study, anammox activity was inhibited by all oxytetracycline concentrations studied. However, daily addition of oxytetracycline to a concentration of 5 ± 3.5 mg/L in the anammox sequencing batch reactor completely inhibited anammox activity in the fifth week. Fluorescent in situ hybridization was used to identify autotrophic ammonium oxidizing bacteria (Nitrosomonas spp., Nitrobacter spp., Nitrospira spp., Candidatus Brocadia anammoxidans, and Candidatus Kuenenia stuttgartiensis). The population of anammox culture was significantly decreased while Nitrosomonas spp. and Nitrospira spp. increased in the fifth week compared with the first week of experiment. A not-competitive model fit the anammox inhibition data at oxytetracycline concentrations of 0-100 mg/L quite well with V(max) of 0.0435 mg N/mg VSS-hr and K(i) of 54.66 mg/L.

Nitrogen removal of anammox cultures under different enrichment conditions.

Anammox bacteria in sludge from an anoxic tank of a municipal wastewater treatment plant at Nongkhaem, Bangkok, Thailand were enriched in two sequencing batch reactors (SBRs; SBR-1 and SBR-2), under different conditions. SBR-1 was open to the atmosphere, while SBR-2 was closed and flushed with a mixture of 95% argon and 5% CO(2) during the fill period in order to provide strict anaerobic conditions. The specific nitrogen removal rates of SBR-1 and SBR-2 were 0.43 g N/g VSS-d and 2.59 g N/g VSS-d, respectively. Denaturing gradient gel electrophoresis (DGGE) analyses showed differences in band patterns among the Nongkhaem sludge and the two enrichment cultures. Based on fluorescent in situ hybridization (FISH), the anammox bacteria in both systems were either "Candidatus Brocadia anammoxidans" or "Candidatus Kuenenia stuttgartiensis". The results from this study demonstrate the potential of alternative anammox systems for nitrogen removal and provide information on the microbial communities of anammox cultures under different enrichment conditions.

Anaerobic ammonium oxidation by Nitrosomonas spp. and anammox bacteria in a sequencing batch reactor.

A sequencing batch reactor (SBR) was inoculated with mixed nitrifying bacteria from an anoxic tank at the conventional activated sludge wastewater treatment plant in Nongkhaem, Bangkok, Thailand. This enriched nitrifying culture was maintained under anaerobic conditions using ammonium (NH(4)(+)) as an electron donor and nitrite (NO(2)(-)) as an electron acceptor. Autotrophic ammonium oxidizing bacteria survived under these conditions. The enrichment period for anammox culture was over 100 days. Both ammonium and nitrite conversion rates were proportional to the biomass of ammonium oxidizing bacteria; rates were 0.08 g N/gV SS/d and 0.05 g N/g VSS/d for ammonium and nitrite, respectively, in a culture maintained for 3 months at 42 mg N/L ammonium. The nitrogen transformation rate at a ratio of NH(4)(+)-N to NO(2)(-)-N of 1:1.38 was faster, and effluent nitrogen levels were lower, than at ratios of 1:0.671, 1:2.18, and 1:3.05. Fluorescent in situ hybridization (FISH) was used to identify specific autotrophic ammonium oxidizing bacteria (Nitrosomonas spp., Candidatus Brocadia anammoxidans, and Candidatus Kuenenia stuttgartiensis). The ammonium oxidizing culture maintained at 42 mg N/L ammonium was enriched for Nitrosomonas spp. (30%) over Candidati B. anammoxidans and K. stuttgartiensis (2.1%) while the culture maintained at 210 mg N/L ammonium was dominated by Candidati B. anammoxidans and K. stuttgartiensis (85.6%). The specific nitrogen removal rate of anammox bacteria (0.6 g N/g anammox VSS/d) was significantly higher than that of ammonium oxidizing bacteria (0.4 g N/g Nitrosomonas VSS/d). Anammox bacteria removed up to 979 mg N/L/d of total nitrogen (ammonium:nitrite concentrations, 397:582 mg N/L). These results suggest significant promise of this approach for application to wastewater with high nitrogen but low carbon content, such as that found in Bangkok.

Compatibility of polymers and chemical oxidants for enhanced groundwater remediation.

Polymer floods provide a promising method to more effectively deliver conventional groundwater treatment agents to organic contaminants distributed within heterogeneous aquifer systems. Combinations of nontoxic polymers (xanthan and hydrolyzed polyacrylamide) and common chemical oxidants (potassium permanganate and sodium persulfate) were investigated to determine the suitability of these mixtures for polymer-enhanced in situ chemical oxidation applications. Oxidant demand and solution viscosity were utilized as initial measures of chemical compatibility. After 72 h of reaction with both test oxidants, solution viscosities in mixtures containing hydrolyzed polyacrylamide were decreased by more than 90% (final viscosities approximately 2 cP), similar to the 95% viscosity loss (final viscosities approximately 1 cP, near that of water) observed in xanthan/persulfate experiments. In contrast, xanthan solutions exposed to potassium permanganate preserved 60-95% of initial viscosity after 72 h. Permanganate depletion in xanthan-containing experiments ranged from 2% to 24% over the same test period. Although oxidant consumption in xanthan/permanganate solutions appeared to be correlated with increasing xanthan concentrations, solutions of up to 2000 mg/L xanthan did not inhibit permanganate from oxidizing a dissolved-phase test contaminant (tetrachloroethene, PCE) in xanthan solution. These advantageous characteristics (high viscosity retention, moderate oxidant demand, and lack of competitive effects on PCE oxidation rate) render xanthan/permanganate the most compatible polymer/oxidant combination of those tested for remediation by polymer-enhanced chemical oxidation.

Biologically enhanced mass transfer of tetrachloroethene from DNAPL in source zones: experimental evaluation and influence of pool morphology.

High-saturation pools of dense nonaqueous phase liquid (DNAPL) are long-term sources of groundwater contamination at many hazardous-waste sites. DNAPL pools consist of a high saturation zone with slow dissolution overlaid by a transition zone with lower saturations and more rapid dissolution. Effects of biological activity on pool dissolution must be understood to evaluate and implement bioremediation strategies. Bioenhanced dissolution of tetrachloroethene (PCE) in transition zones of high-saturation pools was investigated in a custom-designed 5-cm flow cell. Experiments were conducted to characterize mass transfer following DNAPL emplacement, with and without an active microbial culture capable of reductive dehalogenation. For average pool saturations < or = 0.55, mass transfer during biodegradation was enhanced by factors of 4-13, due primarily to high mass flux of PCE degradation products. However, at an average pool saturation of 0.74, mass transfer was enhanced by factors less than 1.5. Mass transfer was significantly greater from pools with an observable transition zone than without. Advective flow through multiphase transition zones enhanced dissolution and biological activity. These laboratory-scale experimental results suggest that biotechnologies may be effective remediation strategies for depletion of source zones within pool transition zones.

Coupling permanganate oxidation with microbial dechlorination of tetrachloroethene.

For sites contaminated with chloroethene non-aqueous-phase liquids, designing a remediation system that couples in situ chemical oxidation (ISCO) with potassium permanganate (KMnO4) and microbial dechlorination may be complicated because of the potentially adverse effects of ISCO on anaerobic bioremediation processes. Therefore, one-dimensional column studies were conducted to understand the effect of permanganate oxidation on tetrachloroethene (PCE) dechlorination by the anaerobic mixed culture KB-1. Following the confirmation of PCE dechlorination, KMnO4 was applied to all columns at a range of concentrations and application velocities to simulate varied distances from oxidant injection. Immediately following oxidation, reductive dechlorination was inhibited; however, after passing several pore volumes of sterile growth medium through the columns after oxidation, a rebound of PCE dechlorination activity was observed in every inoculated column without the need to reinoculate. The volume of medium required for a rebound of dechlorination activity differed from 1.1 to 8.1 pore volumes (at a groundwater velocity of 4 cm/d), depending on the specific condition of oxidant application.

Effects of heterogeneity and experimental scale on the biodegradation of diesel.

Biodegradation of petroleum hydrocarbon contamination is a common method for remediating soils and groundwater. Due to complexities with field-scale studies, biodegradation rates are typically evaluated at the bench-scale in laboratory studies. However, important field conditions can be difficult to mimic in the laboratory. This study investigates three scaling factors that can impact laboratory biodegradation rates and that are frequently unaccounted for in typical laboratory experimental procedures. These factors are soil heterogeneity, morphology of petroleum hydrocarbon non-aqueous phase liquids (NAPLs) and soil moisture distribution. The effects of these factors on the biodegradation rate of diesel NAPL is tested under a variety of experimental procedures from well-mixed batch studies to four-foot static soil columns. The results indicate that a high degree of variability results from even small-scale heterogeneities. In addition, it appears that as the experimental scale increases, the measured biodegradation rates slow. The results indicate that diesel biodegradation rates derived from small-scale experiments are not necessarily representative of field-scale biodegradation rates.