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Treatment of domestic wastewater can recover valuable resources, including clean water, energy, and ammonia. Important metrics for these systems are greenhouse gas (GHG) emissions and embodied energy, both of which are location- and technology-dependent. Here, we determine the embodied energy and GHG emissions resulting from a conventional process train, and we compare them to a nonconventional process train. The conventional train assumes freshwater conveyance from a pristine source that requires energy for pumping (US average of 0.29 kWh/m

CFD modeling of fluidized bed bioreactors can identify desirable operational regimes and improve design.

Wastewater-based epidemiology has gained attention throughout the world for detection of SARS-CoV-2 RNA in wastewater to supplement clinical testing. Raw wastewater consists of small particles, or solids, suspended in liquid. Methods have been developed to measure SARS-CoV-2 RNA in the liquid and the solid fraction of wastewater, with some studies reporting higher concentrations in the solid fraction. To investigate this relationship further, six laboratories collaborated to conduct a study across five publicly owned treatment works (POTWs) where both primary settled solids obtained from primary clarifiers and raw wastewater influent samples were collected and quantified for SARS-CoV-2 RNA. Settled solids and influent samples were processed by participating laboratories using their respective methods and retrospectively paired based on date of collection. SARS-CoV-2 RNA concentrations, on a mass equivalent basis, were higher in settled solids than in influent by approximately three orders of magnitude. Concentrations in matched settled solids and influent were positively and significantly correlated at all five POTWs. RNA concentrations in both settled solids and influent were correlated to COVID-19 incidence rates in the sewersheds and thus representative of disease occurrence; the settled solids methods appeared to produce a comparable relationship between SARS-CoV-2 RNA concentration measurements and incidence rates across all POTWs. Settled solids and influent methods showed comparable sensitivity, N gene detection frequency, and calculated empirical incidence rate lower limits. Analysis of settled solids for SARS-CoV-2 RNA has the advantage of using less sample volume to achieve similar sensitivity to influent methods.

Methane emitted and flared from industrial sources across the United States is a major contributor to global climate change. Methanotrophic bacteria can transform this methane into useful protein-rich biomass, already approved for inclusion into animal feed. In the rapidly growing aquaculture industry, methanotrophic additives have a favourable amino acid profile and can offset ocean-caught fishmeal, reducing demands on over-harvested fisheries. Here we analyse the economic potential of producing methanotrophic microbial protein from stranded methane produced at wastewater treatment plants, landfills, and oil and gas facilities. Our results show that current technology can enable production, in the United States alone, equivalent to 14% of the global fishmeal market at prices at or below the current cost of fishmeal (roughly US$1,600 per metric ton). A sensitivity analysis highlights technically and economically feasible cost reductions (such as reduced cooling or labour requirements), which could allow stranded methane from the United States alone to satisfy global fishmeal demand. Methanotrophic bacteria can capture waste greenhouse gas emissions and feed fish, reducing the need for wild captures. An economic analysis shows great potential for this approach to replace aquaculture feed at competitive prices.

As renewed interest in human space-exploration intensifies, a coherent and modernized strategy for mission-design and planning has become increasingly crucial. Biotechnology has emerged as a promising approach to increase mission resilience, flexibility, and efficiency by virtue of its ability to efficiently utilize in situ resources and reclaim resources from waste streams. Since its infancy during the Apollo years, biotechnology, and specifically biomanufacturing, have witnessed significant expansions of scope and scale. Here we outline four primary mission classes, on Luna and Mars, that drive a staged and accretive biomanufacturing strategy. Each class requires a unique approach to integrate biomanufacturing into the existing mission architecture and so faces unique challenges in technology development.These challenges stem directly from the resources available in a given mission class – the degree to which feedstocks are derived from cargo and in situ resources – and the degree to which loop-closure is necessary. We see that as mission duration and distance from Earth increase, the benefits of specialized sustainable biomanufacturing processes increases. Here we present a strategic approach, guided by technoeconomics, to development, testing, and deployment of these technologies serves to nucleate the larger effort of supporting a sustained human presence in space. The processes needed for each scenario spans the technical breadth of synthetic biology to design engineering, from sophisticated genetic tailoring of chassis-organisms to building scalable, automated, easily operable bioreactors and processing systems. As space-related technology development often does, these advancements are likely to have profound implications for the creation of a stable, resilient bioeconomy on Earth.

As the global threat of plastic pollution has grown in scale and urgency, so have efforts to find sustainable and efficient solutions. Research conducted over the past few years has identified gut environments within insect larvae, including Tenebrio molitor (yellow mealworms), as microenvironments uniquely suited to rapid plastic biodegradation. However, there is currently limited understanding of how the insect host and its gut microbiome collaborate to create an environment conducive to plastic biodegradation. In this work, we provide evidence that T. molitor secretes one or more emulsifying factor(s) (30-100 kDa) that mediate plastic bioavailability. We also demonstrate that the insect gut microbiome secretes factor(s) (

Recovery of struvite at wastewater treatment plants provides a beneficial fertilizer while preventing costly operational issues due to precipitation in pipes, pumps, and digesters. At present, however, sale of struvite as fertilizer is hampered by low revenues. A higher value proposition of struvite is its use in phosphorus-based fire retardants, in which phosphoric acids released at elevated temperatures react catalytically with organic substrates to produce layers of carbon char that smother the flame. In this work, we evaluated the fire retardant performance of wastewater-derived struvite suspended in a low-cost viscoelastic hydrogel carrier (0.68% hydroxyethylcellulose, 0.12% methylcellulose, and 5% colloidal silica nanoparticles). The effectiveness of this formulation was compared to that of a conventional polyphosphate-based fire retardant in thermogravimetric analyses of wood samples and lab-scale burn tests of dry grass. The struvite-based formulation exhibited performance comparable to the polyphosphate retardant while requiring 60% less total phosphorus. Moreover, because struvite is derived from wastewater, applications of struvite in fire retardants can offset demand for mined phosphorus, a finite resource. Analysis of supply and demand for conventional fire retardants in the US indicates that wastewater treatment plants could produce sufficient amounts of struvite-based fire retardants to meet US demands for wildfire suppression while significantly improving revenues over direct struvite fertilizer sales. We conclude that wastewater-derived struvite is a promising green chemistry agent for fire retardants and can contribute to global phosphorus conservation.

Anaerobic membrane bioreactors can now produce effluent that meets regulatory standards for BOD, enabling energy recovery and use of the treated effluent for irrigation. RO treatment of this effluent can potentially enable recovery of potable water and total ammonia nitrogen (TAN). In this study, we optimized the removal of TAN from the effluent of a staged anaerobic membrane bioreactor (SAF-MBR), a system that consists of an anaerobic fluidized bed reactor and anaerobic membrane bioreactor. The SAF-MBR effluent was treated using an ESPA RO membrane. The result was a high-quality RO permeate that meets the typical potable water guidelines (≤1 mg N L−1). Hydraulic operating conditions (i.e., pressure and flux settings) did not affect TAN rejection efficiency, but pH had major impacts, due to changes in ammonium/ammonia speciation and membrane surface charge. At pH 6, the TAN rejection efficiency was optimal at 99.8%. For pH > 6, the passage of uncharged NH3 increased, decreasing TAN removal. For pH < 6, the membrane retained a progressively less negative (carboxylate) charge as the pH decreased, decreasing ammonium removal from the optimum and allowing increased passage of ammonium into the permeate. Our results suggest that an RO membrane having a lower isoelectric point (IEP) can enable higher TAN rejection efficiencies. A more concentrated RO retentate enables more efficient recovery of ammonia for reuse, and the energy required is less than the energy needed for biological removal of NH3 as N2 followed by synthesis of NH3 from N2 by the Haber–Bosch process. Further systems level research is needed to assess the energy intensity of different options for recovery and reuse of concentrated ammonia.

We developed and implemented a framework for examining how molecular assay sensitivity for a viral RNA genome target affects its utility for wastewater-based epidemiology. We applied this framework to digital droplet RT-PCR measurements of SARS-CoV-2 and Pepper Mild Mottle Virus genes made using 10 replicate wells, and determined how using fewer wells affected assay sensitivity and its performance for wastewater-based epidemiology applications. We used a computational, downsampling approach. When percent of positive droplets was between 0.024% and 0.5% (as was the case for SARS-CoV-2 genes during the Delta surge), measurements obtained with 3 or more wells were similar to those obtained using 10. When percent of positive droplets was less than 0.024%, then 6 or more wells were needed to obtain similar results as those obtained using 10 wells. When COVID-19 incidence is low, as it was before the Delta surge and SARS-CoV-2 gene concentrations are 4 cp/g, using 6 wells will yield a detectable concentration 90% of the time. Overall, results support an adaptive approach where assay sensitivity is increased by running 6 or more wells during periods of low SARS-CoV-2 gene concentrations, and 3 or more wells during periods of high SARS-CoV-2 gene concentrations.SynopsisAdaptive approaches developed with assay sensitivity in consideration may reduce cost and increase sensitivity for wastewater-based epidemiology.Abstract Art

Prior to the 1960s, knowledge of biological transformations of highly halogenated aliphatic compounds was limited, except in mammalian organisms where enzymatic transformations occurred to rid the body of ingested harmful chemicals. Limited abiotic transformation of such compounds had also been observed, with half-lives varying from days to centuries. Commonly believed was that aerobic transformation might occur by cometabolism rather than to conserve energy for respiration, while anaerobic transformations were in general thought not to occur. However, in the late 1960s anaerobic transformation of chlorinated pesticides was noted, and then in the early 1980s, partial microbial dehalogenation of chlorinated solvents such as tetrachlorethene, trichloroethene, trichlorethane, and carbon tetrachloride was also found to occur. With only partial dechlorination, complete detoxification was not achieved. And at the time, dehalogenation reactions were not believed to yield energy for growth to the degrading microorganisms. However, in the 1990s bacteria began to be found that obtain energy from anaerobic transformations, often enabling complete dechlorination and detoxification. Since then such ability has been found among several bacterial species, many of which use molecular hydrogen as a donor substrate and halogenated organics as electron acceptors, thus conserving energy through reductive dehalogenation. Growth of knowledge in this field has grown rapidly since the 1960s. Broad usages of such microorganisms are now underway to rid contaminated groundwater of hazardous halogenated chemicals.

Stormwater runoff is a significant source of coastal pathogen pollution. Here, we demonstrate field-scale use of a charge-free mixing entropy battery (MEB) to tap the salinity gradient voltage between stormwater and seawater and use it to power stormwater disinfection in an UV-LED module, achieving a 2.8 log reduction in E. coli.

Nitritation of anaerobic digestion centrate reduces aeration energy demand by preventing oxidation to nitrate and can be affected by changes in upstream processing of anaerobic digestate. Here we report autotrophic/heterotrophic nitritation and partial denitrification in a pilot-scale reactor treating anaerobic digester centrate amended with nitrogen-containing coagulants. The pilot reactor selected for a stable microbial community with nitritation of 60–65% of influent TKN; ∼30–35% nitrogen removal; low nitrate concentrations; and concurrent appearance of autotrophic and heterotrophic ammonia oxidizing bacteria (AOB). Dominant autotrophic AOB were Nitrosomonadaceae. Heterotrophic AOB included Xanthomonadaceae and Chitinophagaceae. Denitrifying bacteria included Comamonadaceae and Actinomycetales. The effects of coagulant dosage on nitritation were studied in bench-scale sequencing batch bioreactors (SBRs), where unclassified AOB were identified that had amoA sequences clustering between the autotrophic and heterotrophic clades. Heterotrophic nitritation was stimulated by glucose addition, especially in SBR biomass adapted to continuous coagulant addition, with elevated levels of Xanthomonadaceae, Chitinophagaceae, and Rhodanobacteraceae. Further research is needed to understand the effects of coagulants on downstream nitrogen removal unit operations and implications for land-application of treated biosolids.

Synthetic materials are integral components of consumable and durable goods and are indispensable in the modern world. Polyesters are the most versatile bulk- and specialty-polymers but their production is not sustainable and their fate at end-of-life is of great concern. Bioplastics are highly regarded alternatives but often fall behind conventional synthetic plastics due to shortcomings in material properties and commercial competitiveness. This has limited the success of sustainable replacements at global market scale. Enabling production of bioplastics with superior properties from waste-derived feedstocks could change that. To this end, we created a synthetic entry into the metabolic pathway of bio-polyester synthesis ofCupriavidus necatorH16 by means of heterologous hydroxyacyl-CoA transferase and mutant PHA synthase. The resulting microbial cell factories produced a range of aliphatic and aromatic biopolyesters and enabled co-polymerization of a range of hydroxy carboxylates, including a hydroxyphenylic and a hydroxyfuranoic acid, for the first time incorporating aromatic rings in the backbone of biological polyesters. These diverse polymers were then characterized in terms of their physical properties. The resulting polymers were structurally analogous to synthetic polyesters like PET, PEF and other polyarylates. In a further advance, the transgenic strain was cultivated in a bio-electrochemical system under autotrophic conditions, enabling synthesis of aromatic bio-polyesters fromin-situgenerated O2, while assimilating CO2. Follow-up elementary flux-mode analysis established the feasibility ofde novoproduction of twenty different polyesters from five different carbon- and energy-sources. This comprehensive study opens the door to sustainable bio-production of various high-performance thermoplastics and thermosets.Significance statementBiomaterials can facilitate the transition of chemical industry to a carbon-neutral and circular economy and prevent the accumulation of greenhouse gases and plastic waste in the natural environment by developing bio-replacements for existing fossil carbon-based plastics along with end-of-life strategies. Accomplished via the genetic engineering of a microbial cell factory that assimilates carbon dioxide, this work demonstrates the first biocatalytic polymerization of aromatic building blocks and their incorporation into the backbone of a bio-polyester. Employing a bio-electrochemical system for cultivation of the microbes, oxyhydrogen is formed and consumedin-situ, thus avoiding explosive gasmixtures. The obtained aromatic polyesters are structural analogs to synthetic bulk- and high-performance polymers such as PET (polyethylene terephthalate) and PEF (polyethylene furanoate).Highlights-First demonstration of bio-polyarylates – microbial polyesters with aromatic rings in the backbone-Production of novel PHAs from CO2and H2+O2achievedin-situin a bio-electrochemical system-Expression-level of PHA synthase and molecular weight of polyesters is inversely correlated-In silicodesign and pathway analysis of bio-polyesters from low-cost carbon-feedstocks

Wastewater-based epidemiology has gained attention throughout the world for detection of SARS-CoV-2 RNA in wastewater to supplement clinical testing. Methods have been developed using both the liquid and the solid fraction of wastewater, with some studies reporting higher concentrations in solids. To investigate this relationship further, we collaborated with six other laboratories to conduct a study across five publicly owned treatment works (POTWs) where both primary solids and raw wastewater influent samples were collected and quantified for SARS-CoV-2 RNA. Solids and influent samples were processed by participating laboratories using their respective methods and retrospectively paired based on date of collection. SARS-CoV-2 RNA concentrations by mass (gene copies per gram) were higher in solids than in influent by approximately three orders of magnitude. Concentrations in matched solids and influent were positively and significantly correlated at all five POTWs. RNA concentrations in both solids and influent were correlated to COVID-19 incidence rates in the sewershed and thus representative of disease burden; the solids methods appeared to produce a comparable relationship between SARS-CoV-2 RNA concentration measurements and incidence rates across all POTWs. Solids and influent methods showed comparable sensitivity, N gene detection frequency, and calculated empirical incidence rate lower limits. Analysis of solids has the advantage of using less sample volume to achieve similar sensitivity to influent methods.

Since industrial fluidized-bed reactors typically operate with polydispersed particles, approximating such reactors as the superposition of corresponding monodispersed fluidized beds would greatly simplify their design and operation. To examine the validity of this superposition, we evaluate the effects of bidispersity by comparing three-dimensional liquid-solid monodispersed and segregated bidipsersed fluidized beds. This work demonstrates that, despite the clear segregation into layers that behave like monodispersed beds, the transition region is governed by complex bidispersed mechanisms that cannot be explained in terms of the particle behavior in the segregated layers.

As awareness of the ubiquity and magnitude of plastic pollution has increased, so has interest in the long term fate of plastics. To date, however, the fate of potentially toxic plastic additives has received comparatively little attention. In this study, we investigated the fate of the flame retardant hexabromocyclododecane (HBCD) in polystyrene (PS)-degrading mealworms and in mealworm-fed shrimp. Most of the commercial HBCD consumed by the mealworms was egested in frass within 24 h (1-log removal) with nearly a 3-log removal after 48 h. In mealworms fed PS containing high HBCD levels, only 0.27 ± 0.10%, of the ingested HBCD remained in the mealworm body tissue. This value did not increase over the course of the experiment, indicating little or no bioaccumulation. Additionally, no evidence of higher trophic level bioaccumulation or toxicity was observed when L. vannamei (Pacific whiteleg shrimp) were fed mealworm biomass grown with PS containing HBCD. Differences in shrimp survival were attributable to the fraction of mealworm biomass incorporated into the diet, not HBCD. We conclude that the environmental effects of PS ingestion need further evaluation as the generation of smaller, more contaminated particles is possible, and may contribute to toxicity at nanoscale.

A microbial battery (MB) breaks down waste organics and stores the liberated electrons in a solid-state cathode. Here, we demonstrate that these electrons can be utilized, along with the products (e.g., carbon dioxide, CO2) of the MB, to electrochemically generate higher-value products from waste. We utilize a series-stacked MB with mediated enzymatic electrosynthesis (EES) to produce either hydrogen (H2) from protons (H+) or formate (HCOO–) from CO2 with the electrons and carbon directly derived from waste organics. We also demonstrate that a reduced solid-state cathode can be used as a solid-state anode as an electron source for EES. This work shows that higher-value products can be electrochemically generated at high faradaic efficiencies (up to 91% for hydrogenase and 72% for formate dehydrogenase) using the energy, electrons, and carbon contained in the waste organic input without the need for continuous oxygen, potentiostatic control, or supplemental power.

Significance Despite strong fire prevention efforts, every year wildfires destroy millions of acres of forest. While fires are necessary for a healthy forest ecology, the vast majority are human-caused and occur in high-risk areas such as roadsides and utilities infrastructure. Yet, retardant-based treatments to prevent ignitions at the source are currently impossible with existing technologies, which are only suited for reactive fire prevention approaches. Here we develop a viscoelastic carrier fluid for existing fire retardants to enhance retention on common wildfire-prone vegetation through environmental exposure and weathering. These materials enable a prophylactic wildfire prevention strategy, where areas at high risk of wildfire can be treated and protected from ignitions throughout the peak fire season., Polyphosphate fire retardants are a critical tactical resource for fighting fires in the wildland and in the wildland–urban interface. Yet, application of these retardants is limited to emergency suppression strategies because current formulations cannot retain fire retardants on target vegetation for extended periods of time through environmental exposure and weathering. New retardant formulations with persistent retention to target vegetation throughout the peak fire season would enable methodical, prophylactic treatment strategies of landscapes at high risk of wildfires through prolonged prevention of ignition and continual impediment to active flaming fronts. Here we develop a sprayable, environmentally benign viscoelastic fluid comprising biopolymers and colloidal silica to enhance adherence and retention of polyphosphate retardants on common wildfire-prone vegetation. These viscoelastic fluids exhibit appropriate wetting and rheological responses to enable robust retardant adherence to vegetation following spray application. Further, laboratory and pilot-scale burn studies establish that these materials drastically reduce ignition probability before and after simulated weathering events. Overall, these studies demonstrate how these materials actualize opportunities to shift the approach of retardant-based wildfire management from reactive suppression to proactive prevention at the source of ignitions.

Salinity gradients are a vast and untapped energy resource. For every cubic meter of freshwater that mixes with seawater, approximately 0.65 kW h of theoretically recoverable energy is lost. For coastal wastewater treatment plants that discharge to the ocean, this energy, if recovered, could power the plant. The mixing entropy battery (MEB) uses battery electrodes to convert salinity gradient energy into electricity in a four-step process: (1) freshwater exchange; (2) charging in freshwater; (3) seawater exchange; and (4) discharging in seawater. Previously, we demonstrated a proof of concept, but with electrode materials that required an energy investment during the charging step. Here, we introduce a charge-free MEB with low-cost electrodes: Prussian Blue (PB) and polypyrrole (PPy). Importantly, this MEB requires no energy investment, and the electrode materials are stable with repeated cycling. The MEB equipped with PB and PPy achieved high voltage ratios (actual voltages obtained divided by the theoretical voltages) of 89.5% in wastewater effluent and 97.6% in seawater, with over 93% capacity retention after 50 cycles of operation and 97-99% over 150 cycles with a polyvinyl alcohol/sulfosuccinic acid (PVA/SSA) coating on the PB electrode.

Accumulation of plastic pollution in aquatic ecosystems is the predictable result of high demand for plastic functionalities, optimized production with economies of scale, and recalcitrance. Strategies are needed for end-of-life conversion of recalcitrant plastics into useful feedstocks and for transition to materials that are biodegradable, non-bioaccumulative, and non-toxic. Promising alternatives are the polyhydroxyalkanoates (PHAs), a vast family of polymers amenable to decentralized production from renewable feedstocks. Establishment of a global-scale PHA-based industry will require identification of PHAs with tailored properties for use as 'drop-in' replacements for existing plastics; use of low-cost renewable/waste-derived feedstocks; high productivity cultures that may be genetically modified microorganisms or non-axenic mixed cultures maintained by selection pressures that favor high PHA-producing strains; and low-cost extraction/purification schemes.

Meeting global food needs in the face of climate change and resource limitation requires innovative approaches to food production. Here, we explore incorporation of new dark food chains into human food systems, drawing inspiration from natural ecosystems, the history of single cell protein, and opportunities for new food production through wastewater treatment, microbial protein production, and aquaculture. The envisioned dark food chains rely upon chemoautotrophy in lieu of photosynthesis, with primary production based upon assimilation of CH4 and CO2 by methane- and hydrogen-oxidizing bacteria. The stoichiometry, kinetics, and thermodynamics of these bacteria are evaluated, and opportunities for recycling of carbon, nitrogen, and water are explored. Because these processes do not require light delivery, high volumetric productivities are possible; because they are exothermic, heat is available for downstream protein processing; because the feedstock gases are cheap, existing pipeline infrastructure could facilitate low-cost energy-efficient delivery in urban environments. Potential life-cycle benefits include: a protein alternative to fishmeal; partial decoupling of animal feed from human food; climate change mitigation due to decreased land use for agriculture; efficient local cycling of carbon and nutrients that offsets the need for energy-intensive fertilizers; and production of high value products, such as the prebiotic polyhydroxybutyrate.

Storage, preservation, and batch-to-batch variability of the influent composition are challenges to laboratory-scale research in the wastewater treatment field. Synthetic wastewaters are commonly used, but many fail to capture the complexity of actual wastewater, especially in terms of particulate organic matter. An alternative synthetic sewage, referred to as complex organic particulate artificial sewage (COPAS), is introduced in this study. COPAS is easily prepared and is based on a simple recipe that uses granular dried cat food as the source of particulate organic matter. On a weight basis, COPAS particles consist of proteins (40%), fats (17%), carbohydrates (43%), and trace nutrients, including vitamins and trace metals. Dissolution/hydrolysis batch tests of COPAS particles indicate that the dissolved organic carbon and nitrogen are released rapidly within the first two hours (approximately 10% C and 17% N). The remaining fraction of organic C and N remain in the particulate form for further dissolution and/or biodegradation. A khyd of 0.82 d−1 was calculated for COPAS based on its protein, fat, and carbohydrate contents. Further, anaerobic bioassays prove the biodegradability of COPAS with approximately 60% theoretical methane produced after 45 days of incubation.

Membrane fouling is the major bottleneck limiting widespread adoption of membrane bioreactors (MBRs), but its root causes are not yet fully understood. In this study, different fouling patterns were observed for replicate MBRs seeded with the same inoculum and maintained under identical operating conditions, with similar levels of biomass, soluble microbial products, and extracellular polymeric substances. None of these had significant correlations with membrane fouling. Exogenous colloidal particles from a real plant did not have an impact on fouling propensity. Fouling appeared to be correlated with increased abundance of specific classes of bacteria, notably Alphaproteobacteria, Sphingobacteria, and Flavobacteria. The membrane biofouling layer had a different community structure from MBR mixed liquor, showing the two dominant phyla Proteobacteria and Chloroflexi.

Nitrogen (N) recycling is essential for efficient food production in regenerative life support systems. Crew members with a high workload need 90–100 g of protein per person per day, which is about 14 g of N, or 1 mole of N, per person per day. Most of this N is excreted through urine with 85% as urea. Plants take up N predominantly as nitrate and ammonium, but direct uptake as urea is possible in small amounts. Efficient N recycling requires maintenance of pH of waste streams below about 7 to minimize the volatilization of N to ammonia. In aerobic reactors, continuous aerobic conditions are needed to minimize production and volatilization of nitrous oxide. N is not well recycled on Earth. The energy intensive Haber–Bosh process supplies most of the N for crop production in terrestrial agriculture. Bacterial fixation of dinitrogen to ammonium is also energy intensive. Recycling of N from plant and human waste streams is necessary to minimize the need for N fixation. Here we review approaches and potential for N fixation and recycling in regenerative life support systems. Initial estimates indicate that nearly all the N from human and plant waste streams can be recovered in forms usable for plants.

Conventional aerobic secondary treatment of domestic wastewater is energy intensive. Here we report net energy positive operation of a pilot-scale anaerobic secondary treatment system in a temperate climate, with low levels of volatile solids for disposal ( 0.15 mgVSS/mgCOD

We study the effects of fluid-particle and particle-particle interactions in a three-dimensional monodispersed reactor with unstable fluidization. Simulations were conducted using the Immersed Boundary Method (IBM) for particle Reynolds numbers of 20-70 with an Archimedes number of 23600. Two different flow regimes were identified as a function of the particle Reynolds number. For low particle Reynolds numbers ($20 < Re_p < 40$), the porosity is relatively low and the particle dynamics are dominated by interparticle collisions that produce anisotropic particle velocity fluctuations. The relative importance of hydrodynamic effects increases with increasing particle Reynolds number, leading to a minimized anisotropy in the particle velocity fluctuations at an intermediate particle Reynolds number. For high particle Reynolds numbers ($Re_p > 40$), the particle dynamics are dominated by hydrodynamic effects, leading to decreasing and more anisotropic particle velocity fluctuations. A sharp increase in the anisotropy occurs when the particle Reynolds number increases from 40 to 50, corresponding to a transition from a regime in which collision and hydrodynamic effects are equally important (Regime 1) to a hydrodynamic-dominated regime (Regime 2). The results imply an optimum particle Reynolds number of roughly 40 for the investigated Archimedes number of 23600 at which mixing in the reactor is expected to peak, which is consistent with reactor studies showing peak performance at a similar particle Reynolds number and with a similar Archimedes number. Results also show that maximum effective collisions are attained at intermediate particle Reynolds number. Future work is required to relate optimum particle Reynolds number to Archimedes number., 28 pages, 17 figures

Biodegradation of plastics has been observed at rapid turnover rate by some insect larvae, especially those of Coleoptera, in particular Tenebrionidae. Tenebrio molitor larva is well studied and capable of biodegrading polystyrene (PS), polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) in their digestive intestine in synergy with their gut microflora. This chapter includes the methods, protocols, and procedures used to characterize biodegradation of plastics in T. molitor larvae and their gut microbiomes with polystyrene as the model feedstock. The methods used can be expanded to enable investigation of other plastics and/or insects.

We present a collocated-grid framework for Direct Numerical Simulations of polydisperse particles submerged in a viscous fluid. The fluid-particle forces are coupled with the Immersed Boundary Method (IBM) while the particle-particle forces are modeled with a combination of contact and lubrication models, adapted for collocated grids. Our method is modified from the staggered-grid IBM of previous authors to a collocated-grid IBM by adapting the fluid and particle solvers. The method scales well on high-performance parallel computing platforms. It has been validated against various cases and is able to reproduce experimental results. Tuning parameters have been thoroughly calibrated to ensure the accuracy of the method. Finally, we demonstrate the capability of the method to simulate both monodispersed and bidispersed fluidized beds and reproduce the power law relationship between the inflow velocity and the porosity., Comment: 32 pages, 17 figures

For microbial electrochemical technologies to be successful in the decentralized treatment of wastewater, steady-state power density must be improved and cost must be decreased. Here, we demonstrate in vivo polymerization ("hard-wiring") of a microbial community to a growing layer of conductive polypyrrole on a sponge bioanode of a microbial battery, showing rapid biocatalytic current development (∼10 times higher than a sponge control after 4 h). Moreover, bioanodes with the polymerized inoculant maintain higher steady-state power density (∼2 times greater than the control after 28 days). We then evaluate the same hard-wired bioanodes in both a two-chamber microbial fuel cell and microbial battery with a solid-state NaFeIIFeIII(CN)6 (Prussian Blue) cathode, showing approximately an order-of-magnitude greater volumetric power density with the microbial battery. The result is a rapid start-up, low-cost (no membrane or platinum catalyst), and high volumetric power density system (independent of atmospheric oxygen) for harvesting energy and carbon from dilute organics in wastewater.

Tenebrio molitor larvae (Coleoptera: Tenebrionidae) are capable of depolymerizing and biodegrading polystyrene and polyethylene. We tested for biodegradation of Polyvinyl Chloride (PVC) in T. molitor larvae using rigid PVC microplastic powders (MPs) (70–150 μm) with weight-, number-, and size-average molecular weights (Mw, Mn and Mz) of 143,800, 82,200 and 244,900 Da, respectively, as sole diet at 25 °C. The ingestion rate was 36.62 ± 6.79 mg MPs 100 larvae-1 d-1 during a 16-day period. The egested frass contained about 34.6% of residual PVC polymer, and chlorinated organic carbons. Gel permeation chromatography (GPC) analysis indicated a decrease in the Mw, Mn and Mz by 33.4%, 32.8%, and 36.4%, respectively, demonstrating broad depolymerization. Biodegradation and oxidation of the PVC MPs was supported by the formation of O C and O C functional groups using frontier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1H NMR), and by significant changes in the thermal characteristics using thermo-gravimetric analysis (TGA). Chloride released was counted as about 2.9% of the PVC ingested, indicating limited mineralization of the PVC MPs. T. molitor larvae survived with PVC as sole diet at up to 80% over 5 weeks but did not complete their life cycle with a low survival rate of 39% in three months. With PVC plus co-diet wheat bran (1:5, w/w), they completed growth and pupation as same as bran only in 91 days. Suppression of gut microbes with the antibiotic gentamicin severely inhibited PVC depolymerization, indicating that the PVC depolymerization/biodegradation was gut microbe-dependent. Significant population shifts and clustering in the gut microbiome and unique OTUs were observed after PVC MPs consumption. The results indicated that T. molitor larvae are capable of performing broad depolymerization/biodegradation but limited mineralization of PVC MPs.

Recent studies have demonstrated the ability for polystyrene (PS) degradation within the gut of mealworms (Tenebrio molitor). To determine whether plastics may be broadly susceptible to biodegradation within mealworms, we evaluated the fate of polyethylene (PE) and mixtures (PE + PS). We find that PE biodegrades at comparable rates to PS. Mass balances indicate conversion of up 49.0 ± 1.4% of the ingested PE into a putative gas fraction (CO2). The molecular weights (Mn) of egested polymer residues decreased by 40.1 ± 8.5% in PE-fed mealworms and by 12.8 ± 3.1% in PS-fed mealworms. NMR and FTIR analyses revealed chemical modifications consistent with degradation and partial oxidation of the polymer. Mixtures likewise degraded. Our results are consistent with a nonspecific degradation mechanism. Analysis of the gut microbiome by next-generation sequencing revealed two OTUs (Citrobacter sp. and Kosakonia sp.) strongly associated with both PE and PS as well as OTUs unique to each plastic. Our results suggest ...

Molecular hydrogen, a valuable clean energy fuel and industrial feedstock, is commonly produced by steam reforming of fossil fuels, a process that results in the co-generation of CO 2 . Strategies that produce H 2 without CO 2 emissions focus on water-splitting powered by solar or wind energy. Here, we introduce a new approach in which energy derived from the oxidation of waste organic matter is used to subsidize the electrical energy consumed by electrochemical H 2 generation. The primary gas product is H 2 , with minimal O 2 contamination, avoiding the purification step required for conventional water electrolysis. The energy efficiency (i.e., energy from H 2 combustion ÷ input electrical energy × 100%) ranges from 214% to 304%. We also demonstrate a sustained cycling operation with concomitant treatment of domestic and industrial wastewater. These findings open the door to recovery of H 2 from other dilute reservoirs of organic matter, such as marine sediment.

Biodegradable resins can enhance the environmental sustainability of wood-plastic composites (WPCs) by enabling methane (CH $$_4$$ ) recovery via anaerobic digestion (AD). An under appreciated step in biocomposite AD is the role of cracking and fragmentation due to moisture uptake by the wood fiber (WF) fraction. Here, we use batch microcosms to simulate AD at end-of-life and to assess the effects of fiber-matrix treatments used to retard in-service moisture uptake. The composites evaluated were injection molded poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with WF (0, 20%) using two fiber-matrix compatibilization treatments: (1) hydrophobic silane treatment of the wood fiber and (2) grafting of hydrophilic maleic anhydride groups to the PHBV matrix. Both treatments accelerated rates of mass loss and CH $$_4$$ production by a factor of 1.2–2.3 compared to neat PHBV. The fragmentation rate, as measured by mass loss, increased significantly for treated samples compared to untreated samples. A ranking of test samples from lowest to highest rates of mass loss gave the following sequence: neat PHBV $$\approx$$ maleated PHBV

The first methanotrophic syntheses of polyhydroxyalkanoates (PHAs) that contain repeating units beyond 3-hydroxybutyrate and 3-hydroxyvalerate are reported. New PHAs synthesized by methanotrophs include poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)), poly(3-hydroxybutyrate-co-5-hydroxyvalerate-co-3-hydroxyvalerate) (P(3HB-co-5HV-co-3HV)), and poly(3-hydroxybutyrate-co-6-hydroxyhexanoate-co-4-hydroxybutyrate) (P(3HB-co-6HHx-co-4HB)). This was achieved from a pure culture of Methylocystis parvus OBBP where the primary substrate is methane and the corresponding ω-hydroxyalkanoate monomers are added as a co-substrate after the cells are subjected to nitrogen-limited conditions. Electronic supplementary material The online version of this article (doi:10.1186/s13568-017-0417-y) contains supplementary material, which is available to authorized users.