The Impact of Bone Marrow Stimulation on Arthroscopic Rotator Cuff Repair for Small to Large Rotator Cuff Tears: A Randomized Controlled Trial.

BACKGROUND: Bone marrow stimulation (BMS), a procedure involving the creation of multiple channels in the greater tuberosity, is often performed alongside arthroscopic rotator cuff repair (ARCR). This study evaluated the effect of BMS on clinical and structural outcomes following ARCR. METHOD: This study involved 204 patients with small, medium, and large full-thickness rotator cuff tears. In all, 103 patients who underwent BMS and ARCR made up the BMS group, while the 101 patients who only had ARCR made up the control group with randomization. Clinical and functional outcomes were assessed before and at 3 months, 6 months, 1 year, and 2 years after surgery, using parameters such as range of motion, functional scores (ASES and constant score), and clinical scores (VAS). Tendon integrity was also examined postoperatively via ultrasound at 6 months and 2 years. RESULTS: There were no significant differences between the two groups concerning range of motion, functional scores (ASES score and constant score), and clinical score (VAS) during the 2-year post-surgery period (all p>0.05). Similarly, the rotator cuff retear rate, as assessed using ultrasonographic tendon integrity checks over 2 years post-surgery, did not significantly vary between the groups (all p>0.05). CONCLUSION: There were no significant disparities in functional scores and clinical outcomes between the BMS and control groups. Further, no significant differences were observed in tendon integrity post-surgery. Therefore, the inclusion or exclusion of BMS is not anticipated to influence the postoperative outcome in ARCR for patients with small, medium, or large rotator cuff tears.

Returning to golf after rotator cuff repair.

Background: The prevalence of rotator cuff repair is increasing; however, no study has assessed patients who have returned to golf activity after arthroscopic rotator cuff repair. Methods: The subjects of the survey were 633 patients who were at least two years postoperative after rotator cuff repair from January 2005 to December 2017. From August 2019 to October 2019, survey responses were collected via an online questionnaire or phone calls and a total of 197 patients were reviewed retrospectively to study about returning to golf after rotator cuff repair. The detailed survey included 12 questions specific to the patient's golf career, performance, time of return to play, and symptoms related to golf activity. Depending on the size of the rotator cuff tear, each question was statistically analyzed to determine whether there were differences in the time of return to golf, uncomfortable symptoms when golfing, and distance of the driving. Results: Of the 197 patients who underwent arthroscopic rotator cuff repair, there were 145 patients (73.6%) returned to golf. In the analysis results of 145 patients, the longer the golf career, the greater the chance of returning to golf. Sixty (30.5%) people returned to golf at 1 year after surgery. Twenty-one patients (10.7%) improved and 46 patients (23.4%) maintained their driving distance, whereas 78 patients (39.6%) had a worse driving distance after surgery. Ten patients (5.1%) improved and 97 patients (49.2%) maintained their golf score, but 38 patients (19.3%) had worse golf scores after surgery. Symptoms when playing golf were reported in the order of no symptoms (62.1%), a limited range of motion (13.1%), muscle weakness (11.1%), and anxious about their operated shoulder (10.3 %). Men were 6.9 times more likely to return to golf than women (odds ratio, 6.9; 95% confidence interval, 3.2-14.8). The younger the age and the shorter the time since surgery, the higher the golfing return rate. The rate of returning to golf was high in the group of patients with good tissue quality during surgery (odds ratio, 3.9; 95% confidence interval, 0.01-2.6). Conclusion: The golfing return rate after arthroscopic rotator cuff repair was higher than expected (73.6%) and most players returned at 1 year after surgery. Especially, in the case of young males, their golf scores were maintained or improved and they were able to return to golf earlier after surgery. Better tissue quality in the intraoperative torn tendon was associated with a greater chance of returning to golf.

Microbial response on the first full-scale DEMON® biomass transfer for mainstream deammonification.

Sidestream partial nitritation and deammonification (pN/A) of high-strength ammonia wastewater is a well-established technology. Its expansion to the mainstream is, however mainly impeded by poor retention of anaerobic ammonia oxidizing bacteria (AnAOB), insufficient repression of nitrite oxidizing bacteria (NOB) and difficult control of soluble chemical oxygen demand and nitrite levels. At the municipal wastewater treatment plant in Strass (Austria) the microbial consortium was exhaustively monitored at full-scale over one and a half year with regular transfer of sidestream DEMON® biomass and further retention and enrichment of granular anammox biomass via hydrocyclone operation. Routine process parameters were surveyed and the response and evolution of the microbiota was followed by molecular tools, ex-situ activity tests and further, AnAOB quantification through particle tracking and heme measurement. After eight months of operation, the first anaerobic, simultaneous depletion of ammonia and nitrite was observed ex-situ, together with a direction to higher nitrite generation (68% of total NOx-N) as compared to nitrate under aerobic conditions. Our dissolved oxygen (DO) scheme allowed for transient anoxic conditions and had a strong influence on nitrite levels and the NOB community, where Nitrobacter eventually dominated Nitrospira. The establishment of a minor but stable AnAOB biomass was accompanied by the rise of Chloroflexi and distinct emergence of Chlorobi, a trend not seen in the sidestream system. Interestingly, the most pronounced switch in the microbial community and noticeable NOB repression occurred during unfavorable conditions, i.e. the cold winter season and high organic load. Further abatement of NOB was achieved through bioaugmentation of aerobic ammonia oxidizing bacteria (AerAOB) from the sidestream-DEMON® tank. Performance of the sidestream pN/A was not impaired by this operational scheme and the average volumetric nitrogen removal rate of the mainstream even doubled in the second half of the monitoring campaign. We conclude that a combination of both, regular sidestream-DEMON® biomass transfer and granular SRT increase via hydrocyclone operation was crucial for AnAOB establishment within the mainstream.

Vertically stacked, low-voltage organic ternary logic circuits including nonvolatile floating-gate memory transistors.

Multi-valued logic (MVL) circuits based on heterojunction transistor (HTR) have emerged as an effective strategy for high-density information processing without increasing the circuit complexity. Herein, an organic ternary logic inverter (T-inverter) is demonstrated, where a nonvolatile floating-gate flash memory is employed to control the channel conductance systematically, thus realizing the stabilized T-inverter operation. The 3-dimensional (3D) T-inverter is fabricated in a vertically stacked form based on all-dry processes, which enables the high-density integration with high device uniformity. In the flash memory, ultrathin polymer dielectrics are utilized to reduce the programming/erasing voltage as well as operating voltage. With the optimum programming state, the 3D T-inverter fulfills all the important requirements such as full-swing operation, optimum intermediate logic value (~VDD/2), high DC gain exceeding 20 V/V as well as low-voltage operation (< 5 V). The organic flash memory exhibits long retention characteristics (current change less than 10% after 104 s), leading to the long-term stability of the 3D T-inverter. We believe the 3D T-inverter employing flash memory developed in this study can provide a useful insight to achieve high-performance MVL circuits.

Systematic Control of Negative Transconductance in Organic Heterojunction Transistor for High-Performance, Low-Power Flexible Ternary Logic Circuits.

Organic multi-valued logic (MVL) circuits can substantially improve the data processing efficiency in highly advanced wearable electronics. Organic ternary logic circuits can be implemented by utilizing the negative transconductance (NTC) of heterojunction transistors (H-TRs). To achieve high-performance organic ternary logic circuits, the range of NTC in H-TRs must be optimized in advance to ensure the well-defined intermediate logic state in ternary logic inverters (T-inverters). Herein, a simple and efficient strategy, which enables the systematic control of the range and position of NTC in H-TRs is presented. Each thickness of p-/n-type semiconductor in H-TRs is adjusted to control the channel conductivity. Furthermore, asymmetric source/drain (S/D) electrode structure is newly developed for H-TRs, which can adjust the amount of hole and electron injection, independently. Based on the semiconductor thickness variation and asymmetric S/D electrodes, the T-inverter exhibits full-swing operation with three distinguishable logic states, resulting in unprecedentedly high static noise margin (≈48% of the ideal value). Moreover, a flexible T-inverter with an ultrathin polymer dielectric is demonstrated, whose operating voltage is less than 8 V. The proposed strategy is fully compatible with the conventional integrated circuit design, which is highly desirable for broad applicability and scalability for various types of T-inverter production.

Highly stacked 3D organic integrated circuits with via-hole-less multilevel metal interconnects.

Multilevel metal interconnects are crucial for the development of large-scale organic integrated circuits. In particular, three-dimensional integrated circuits require a large number of vertical interconnects between layers. Here, we present a novel multilevel metal interconnect scheme that involves solvent-free patterning of insulator layers to form an interconnecting area that ensures a reliable electrical connection between two metals in different layers. Using a highly reliable interconnect method, the highest stacked organic transistors to date, a three-dimensional organic integrated circuits consisting of 5 transistors and 20 metal layers, is successfully fabricated in a solvent-free manner. All transistors exhibit outstanding device characteristics, including a high on/off current ratio of ~107, no hysteresis behavior, and excellent device-to-device uniformity. We also demonstrate two vertically-stacked complementary inverter circuits that use transistors on 4 different floors. All circuits show superb inverter characteristics with a 100% output voltage swing and gain up to 35 V per V.

Metabolite tracking to elucidate the effects of environmental pollutants.

The purpose of this study was to determine whether behavioral tests and metabolic profiling of organisms can be promising alternatives for assessing the health of aquatic systems. Water samples from four potential pollution sources in South Korea were collected for toxicity evaluation. First, conventional acute toxicity test in Daphnia magna and behavioral test in zebrafish was conducted to assess water quality. Second, metabolomic analysis was performed on zebrafish exposed to water samples and on environmental fish collected from the same source. Acute toxicity test in D. magna showed that none of the water samples exerted significant adverse effects. However, activity of zebrafish larvae exposed to samples from the zinc smelter (ZS) and industrial complex (IND) sites decreased compared to those exposed to samples from the reference site (RS). Metabolomic analysis using the Manhattan plot and Partial Least Square (PLS)/Orthogonal PLS Discriminant Analysis (OPLS-DA) showed differences in metabolic profiles between RS and ZS, and between IND and abandoned mine site (M). Interestingly, applying the same metabolomic analysis to environmental fish revealed patterns similar to those for zebrafish, despite the uncontrollable variables involved in environmental sampling. This study shows that metabolomics is a promising tool in assessing the health of aquatic environments.

Functional Circuitry on Commercial Fabric via Textile-Compatible Nanoscale Film Coating Process for Fibertronics.

Fabric-based electronic textiles (e-textiles) are the fundamental components of wearable electronic systems, which can provide convenient hand-free access to computer and electronics applications. However, e-textile technologies presently face significant technical challenges. These challenges include difficulties of fabrication due to the delicate nature of the materials, and limited operating time, a consequence of the conventional normally on computing architecture, with volatile power-hungry electronic components, and modest battery storage. Here, we report a novel poly(ethylene glycol dimethacrylate) (pEGDMA)-textile memristive nonvolatile logic-in-memory circuit, enabling normally off computing, that can overcome those challenges. To form the metal electrode and resistive switching layer, strands of cotton yarn were coated with aluminum (Al) using a solution dip coating method, and the pEGDMA was conformally applied using an initiated chemical vapor deposition process. The intersection of two Al/pEGDMA coated yarns becomes a unit memristor in the lattice structure. The pEGDMA-Textile Memristor (ETM), a form of crossbar array, was interwoven using a grid of Al/pEGDMA coated yarns and untreated yarns. The former were employed in the active memristor and the latter suppressed cell-to-cell disturbance. We experimentally demonstrated for the first time that the basic Boolean functions, including a half adder as well as NOT, NOR, OR, AND, and NAND logic gates, are successfully implemented with the ETM crossbar array on a fabric substrate. This research may represent a breakthrough development for practical wearable and smart fibertronics.

Flexible, Low-Power Thin-Film Transistors Made of Vapor-Phase Synthesized High-k, Ultrathin Polymer Gate Dielectrics.

A series of high-k, ultrathin copolymer gate dielectrics were synthesized from 2-cyanoethyl acrylate (CEA) and di(ethylene glycol) divinyl ether (DEGDVE) monomers by a free radical polymerization via a one-step, vapor-phase, initiated chemical vapor deposition (iCVD) method. The chemical composition of the copolymers was systematically optimized by tuning the input ratio of the vaporized CEA and DEGDVE monomers to achieve a high dielectric constant (k) as well as excellent dielectric strength. Interestingly, DEGDVE was nonhomopolymerizable but it was able to form a copolymer with other kinds of monomers. Utilizing this interesting property of the DEGDVE cross-linker, the dielectric constant of the copolymer film could be maximized with minimum incorporation of the cross-linker moiety. To our knowledge, this is the first report on the synthesis of a cyanide-containing polymer in the vapor phase, where a high-purity polymer film with a maximized dielectric constant was achieved. The dielectric film with the optimized composition showed a dielectric constant greater than 6 and extremely low leakage current densities (<3 × 10-8 A/cm2 in the range of ±2 MV/cm), with a thickness of only 20 nm, which is an outstanding thickness for down-scalable cyanide polymer dielectrics. With this high-k dielectric layer, organic thin-film transistors (OTFTs) and oxide TFTs were fabricated, which showed hysteresis-free transfer characteristics with an operating voltage of less than 3 V. Furthermore, the flexible OTFTs retained their low gate leakage current and ideal TFT characteristics even under 2% applied tensile strain, which makes them some of the most flexible OTFTs reported to date. We believe that these ultrathin, high-k organic dielectric films with excellent mechanical flexibility will play a crucial role in future soft electronics.

Discovery and metagenomic analysis of an anammox bacterial enrichment related to Candidatus "Brocadia caroliniensis" in a full-scale glycerol-fed nitritation-denitritation separate centrate treatment process.

A distinctive red biofilm was observed in a glycerol-fed digester liquid effluent treatment process coupling partial nitrification (nitritation) and partial denitrification (denitritation) processes. Based on initial phylogenetic screening using 16S rRNA clone libraries and quantitative polymerase chain reaction, the biofilm was enriched in novel anaerobic ammonium oxidizing bacteria (AMX/anammox) closely related to Candidatus "Brocadia caroliniensis". The metabolic functionality of the C. "Brocadia caroliniensis" enrichment was further explored using high-throughput sequencing and de novo metagenome assembly. The population anammox genome that was binned from the metagenome consisted of 209 contigs with a total of 3.73 Mbp consensus sequences having 43.3% GC content, and 27.4 average coverage depth. The assembled metagenome bin was comprised of 3582 open reading frames (ORFs). Based on 16S rRNA similarity the binned metagenome was closely related with Candidatus "Brocadia caroliniensis", Candidatus "Brocadia fulgida", planctomycete KSU-1, and Candidatus "Kuenenia stuttgartiensis" with 99%, 96%, 92% and 93% similarity, respectively. Essential genes in anammox metabolic functions including ammonium and nitrite transport, hydrazine synthesis, electron transfer for catabolism, and inorganic carbon fixation, among several other anabolic pathways, were also observed in the population genome of the C. "Brocadia caroliniensis" related enrichment. Our results demonstrate the wider profusion of anammox bacteria in engineered nitrogen removal systems than expected. The utility of metagenomics approaches to deciphering such novel functionality in these systems is also highlighted.

Molecular and Kinetic Characterization of Planktonic Nitrospira spp. Selectively Enriched from Activated Sludge.

Nitrospira spp. are chemolithoautotrophic nitrite-oxidizing bacteria (NOB), which are ubiquitous in natural and engineered environments. However, there exist few independent biokinetic studies on Nitrospira spp., likely because their isolation and selective enrichment from environmental consortia such as activated sludge can be challenging. Herein, planktonic Nitrospira spp. cultures closely related to Candidatus Nitrospira defluvii (Nitrospira lineage I) were successfully enriched from activated sludge in a sequencing batch reactor by maintaining sustained limiting extant nitrite and dissolved oxygen concentrations. Morphologically, the enrichment consisted largely of planktonic cells with an average characteristic diameter of 1.3 ± 0.6 µm. On the basis of respirometric assays, estimated maximum specific growth rate (µmax), nitrite half saturation coefficient (KS), oxygen half saturation coefficient (KO), and biomass yield coefficient (Y) of the enriched cultures were 0.69 ± 0.10 d-1, 0.52 ± 0.14 mg-N/L, 0.33 ± 0.14 mg-O2/L, and 0.14 ± 0.02 mg-COD/mg-N, respectively. These parameters collectively reflect not just higher affinities of this enrichment for nitrite and oxygen, respectively, but also a higher biomass yield and energy transfer efficiency relative to Nitrobacter spp. Used in combination, these kinetic and thermodynamic parameters can help toward the development and application of energy-efficient biological nutrient removal processes through effective Nitrospira out-selection.

Nitrification inhibition by hexavalent chromium Cr(VI)--Microbial ecology, gene expression and off-gas emissions.

The goal of this study was to investigate the responses in the physiology, microbial ecology and gene expression of nitrifying bacteria to imposition of and recovery from Cr(VI) loading in a lab-scale nitrification bioreactor. Exposure to Cr(VI) in the reactor strongly inhibited nitrification performance resulting in a parallel decrease in nitrate production and ammonia consumption. Cr(VI) exposure also led to an overall decrease in total bacterial concentrations in the reactor. However, the fraction of ammonia oxidizing bacteria (AOB) decreased to a greater extent than the fraction of nitrite oxidizing bacteria (NOB). In terms of functional gene expression, a rapid decrease in the transcript concentrations of amoA gene coding for ammonia oxidation in AOB was observed in response to the Cr(VI) shock. In contrast, transcript concentrations of the nxrA gene coding for nitrite oxidation in NOB were relatively unchanged compared to Cr(VI) pre-exposure levels. Therefore, Cr(VI) exposure selectively and directly inhibited activity of AOB, which indirectly resulted in substrate (nitrite) limitation to NOB. Significantly, trends in amoA expression preceded performance trends both during imposition of and recovery from inhibition. During recovery from the Cr(VI) shock, the high ammonia concentrations in the bioreactor resulted in an irreversible shift towards AOB populations, which are expected to be more competitive in high ammonia environments. An inadvertent impact during recovery was increased emission of nitrous oxide (N2O) and nitric oxide (NO), consistent with recent findings linking AOB activity and the production of these gases. Therefore, Cr(VI) exposure elicited multiple responses on the microbial ecology, gene expression and both aqueous and gaseous nitrogenous conversion in a nitrification process. A complementary interrogation of these multiple responses facilitated an understanding of both direct and indirect inhibitory impacts on nitrification.

Nitrogen polishing in a fully anoxic anammox MBBR treating mainstream nitritation-denitritation effluent.

As nitrogen discharge limits are becoming more stringent, short-cut nitrogen systems and tertiary nitrogen polishing steps are gaining popularity. For partial nitritation or nitritation-denitritation systems, anaerobic ammonia oxidation (anammox) polishing may be feasible to remove residual ammonia and nitrite from the effluent. Nitrogen polishing of mainstream nitritation-denitritation system effluent via anammox was studied at 25°C in a fully anoxic moving bed bioreactor (MBBR) (V = 0.45 m(3) ) over 385 days. Unlike other anammox based processes, a very fast startup of anammox MBBR was demonstrated, despite nitrite limited feeding conditions (influent nitrite = 0.7 ± 0.59 mgN/L, ammonia = 6.13 ± 2.86 mgN/L, nitrate = 3.41 ± 1.92 mgN/L). The nitrogen removal performance was very stable within a wide range of nitrogen inputs. Anammox bacteria (AMX) activity up to 1 gN/m(2) /d was observed which is comparable to other biofilm-based systems. It is generally believed that nitrate production limits nitrogen removal through AMX metabolism. However, in this study, anammox MBBR demonstrated ammonia, nitrite, and nitrate removal at limited chemical oxygen demand (COD) availability. AMX and heterotrophs contributed to 0.68 ± 0.17 and 0.32 ± 0.17 of TIN removal, respectively. It was speculated that nitrogen removal might be aided by denitratation which could be due to heterotrophs or the recently discovered ability for AMX to use short-chain fatty acids to reduce nitrate to nitrite. This study demonstrates the feasibility of anammox nitrogen polishing in an MBBR is possible for nitritation-denitration systems.

Direct Observation of a Carbon Filament in Water-Resistant Organic Memory.

The memory for the Internet of Things (IoT) requires versatile characteristics such as flexibility, wearability, and stability in outdoor environments. Resistive random access memory (RRAM) to harness a simple structure and organic material with good flexibility can be an attractive candidate for IoT memory. However, its solution-oriented process and unclear switching mechanism are critical problems. Here we demonstrate iCVD polymer-intercalated RRAM (i-RRAM). i-RRAM exhibits robust flexibility and versatile wearability on any substrate. Stable operation of i-RRAM, even in water, is demonstrated, which is the first experimental presentation of water-resistant organic memory without any waterproof protection package. Moreover, the direct observation of a carbon filament is also reported for the first time using transmission electron microscopy, which puts an end to the controversy surrounding the switching mechanism. Therefore, reproducibility is feasible through comprehensive modeling. Furthermore, a carbon filament is superior to a metal filament in terms of the design window and selection of the electrode material. These results suggest an alternative to solve the critical issues of organic RRAM and an optimized memory type suitable for the IoT era.

Ammonia-based intermittent aeration control optimized for efficient nitrogen removal.

This work describes the development of an intermittently aerated pilot-scale process (V = 0.45 m(3) ) operated for optimized efficient nitrogen removal in terms of volume, supplemental carbon and alkalinity requirements. The intermittent aeration pattern was controlled using a strategy based on effluent ammonia concentration set-points. The unique feature of the ammonia-based aeration control was that a fixed dissolved oxygen (DO) set-point was used and the length of the aerobic and anoxic time (anoxic time ≥25% of total cycle time) were changed based on the effluent ammonia concentration. Unlike continuously aerated ammonia-based aeration control strategies, this approach offered control over the aerobic solids retention time (SRT) to deal with fluctuating ammonia loading without solely relying on changes to the total SRT. This approach allowed the system to be operated at a total SRT with a small safety factor. The benefits of operating at an aggressive SRT were reduced hydraulic retention time (HRT) for nitrogen removal. As a result of such an operation, nitrite oxidizing bacteria (NOB) out-selection was also obtained (ammonia oxidizing bacteria [AOB] maximum activity: 400 ± 79 mgN/L/d, NOB maximum activity: 257 ± 133 mgN/L/d, P < 0.001) expanding opportunities for short-cut nitrogen removal. The pilot demonstrated a total inorganic nitrogen (TIN) removal rate of 95 ± 30 mgN/L/d at an influent chemical oxygen demand: ammonia (COD/NH4 (+) -N) ratio of 10.2 ± 2.2 at 25°C within the hydraulic retention time (HRT) of 4 h and within a total SRT of 5-10 days. The TIN removal efficiency up to 91% was observed during the study, while effluent TIN was 9.6 ± 4.4 mgN/L. Therefore, this pilot-scale study demonstrates that application of the proposed on-line aeration control is capable of relatively high nitrogen removal without supplemental carbon and alkalinity addition at a low HRT.

PDMS-based turbulent microfluidic mixer.

Over the past decade, homogeneous mixing in microfluidic devices has been a critical challenge, because of the inherently low flow rates in microfluidic channels. Although several mixer designs have been suggested to achieve efficient mixing, most of them involve intricate structures requiring a series of laborious fabrication processes. Operation at high flow rates can greatly enhance mixing by induction of turbulence, but devices that can resist such a high pressure drop to induce turbulence in microfluidic channels are difficult to fabricate, especially for commonly used poly(dimethylsiloxane) (PDMS)-based microfluidic devices. We have developed a Y-shaped, turbulent microfluidic mixer made of PDMS and a glass substrate by strong bonding of the substrates to a nanoadhesive layer deposited via initiated chemical vapor deposition. The high bonding strength of the nanoadhesive layer enables safe operation of the PDMS/glass turbulent microfluidic mixer at a total water flow rate of 40 mL min(-1), corresponding to a Reynolds number, Re, of ~4423, one of the highest values achieved in a microfluidic channel. The turbulence generated as a result of the high Re allows rapid mixing of the input fluids on contact. Image analysis showed that mixing started as soon as the fluids were introduced into the mixer. The experimental results matched the numerical predictions well, demonstrating that convective mixing was dominant as a result of turbulence induced in the microfluidic channel. Using the turbulent microfluidic mixer, we have demonstrated high throughput formation of emulsions with narrower size distribution. It was shown that as the flow rate increases inside the microfluidic channel, the size distribution of resulting emulsions decreases owing to the increase in the turbulent energy dissipation. The turbulent microfluidic mixer developed in this work not only enables rapid mixing of streams, but also increases throughputs of microfluidic reactors.

Differentiation in the microbial ecology and activity of suspended and attached bacteria in a nitritation-anammox process.

A directed differentiation between the biofilm and suspension was observed in the molecular microbial ecology and gene expression of different bacteria in a biofilm nitritation-anammox process operated at varying hydraulic residence times (HRT) and nitrogen loading rates (NLR). The highest degree of enrichment observed in the biofilm was of anaerobic ammonia-oxidizing bacteria (AMX) followed by that of Nitrospira spp. related nitrite-oxidizing bacteria (NOB). For AMX, a major shift from Candidatus "Brocadia fulgida" to Candidatus "Kuenenia stuttgartiensis" in both suspension and biofilm was observed with progressively shorter HRT, using discriminatory biomarkers targeting the hydrazine synthase (hzsA) gene. In parallel, expression of the hydrazine oxidoreductase gene (hzo), a functional biomarker for AMX energy metabolism, became progressively prominent in the biofilm. A marginal but statistically significant enrichment in the biofilm was observed for Nitrosomonas europaea related ammonia-oxidizing bacteria (AOB). In direct contrast to AMX, the gene expression of ammonia monooxygenase subunit A (amoA), a functional biomarker for AOB energy metabolism, progressively increased in suspension. Using gene expression and biomass concentration measures in conjunction, it was determined that signatures of AOB metabolism were primarily present in the biofilm throughout the study. On the other hand, AMX metabolism gradually shifted from being uniformly distributed in both the biofilm and suspension to primarily the biofilm at shorter HRTs and higher NLRs. These results therefore highlight the complexity and key differences in the microbial ecology, gene expression and activity between the biofilm and suspension of a nitritation-anammox process and the biokinetic and metabolic drivers for such niche segregation.

The effect of inorganic carbon on microbial interactions in a biofilm nitritation-anammox process.

The overarching goal of this study was to determine the role of inorganic carbon (IC) in influencing the microbial ecology, performance and nitrogen turnover by individual microbial communities of a biofilm based combined nitritation-anammox process. IC limitation was transiently imposed by reducing the IC input from 350% to 40% of the stoichiometric requirement for 40 days. The principal impact observed during IC limitation was the overgrowth of nitrite oxidizing bacteria (NOB) at the expense of anaerobic ammonia oxidizing bacteria (AMX). On the other hand, the concentrations of ammonia oxidizing bacteria (AOB) were relatively stable during the imposition of and recovery from IC limitation. The resulting dominance of NOB, in terms of their concentration and contribution to nitrite consumption over AMX, resulted, in turn, in a decrease in overall nitrogen removal from 78 ± 2.0% before IC limitation to 46 ± 2.9% during IC limitation. Upon recovery back to non-limiting IC input, it took an inordinately long time (about 57*HRT) for the N-removal to recover back to pre-limitation conditions. Even after recovery, NOB were still persistent in the biofilm and could not be washed out to pre-limitation concentrations. The emission of nitrous oxide (N2O) and nitric oxide (NO), likely from AOB, transiently increased in concert with transient increases in ammonia and hydroxylamine concentrations during the period of IC limitation. Therefore, an unintended consequence of IC limitation in nitritation-anammox systems can be an increase in their greenhouse gas footprint, in addition to compromised process performance. Most emphasis to date on nitritation and anammox studies has been on the nitrogen cycle. The results of this study demonstrate that the differing strategies used by AOB, NOB and AMX to compete for their preferred assimilative carbon source can also significantly influence the microbial ecology, performance and carbon footprint of such processes.

Nitric oxide preferentially inhibits nitrite oxidizing communities with high affinity for nitrite.

The prerequisite to the development success of the novel mainstream processes partial nitritation/anammox is the out-selection of nitrite oxidizing bacteria (NOB). A recent study suggested that this could be achieved through NO production by ammonium oxidizing bacteria under cyclic oxic-anoxic conditions. Indeed, it is known that among NOB, Nitrobacter species are reversibly inhibited by NO. However, the effect of NO on the activity of the NOB genus Nitrospira is not studied so far. Such an understanding is needed, since Nitrospira related NOB are mostly prevailing in sewage treatment plants. This study quantified the effect of NO on the nitratation activity of sludge types with different Nitrobacter/Nitrospira ratios. In an oxic bubbling column, a dosage of 4.4 mg NO L(-1) d(-1) (∼2 µg NO-N L(-1) in liquid phase) inhibited the Nitrobacter dominated sludge with 24%. For the Nitrospira dominated sludge types, the inhibition was strongly correlated with the nitrite half saturation constant (K(s)) ranging from 0% to 30-50% and 60-80% inhibition of the nitrite oxidation for K(s) of 0.72, 0.36 and 0.06 mg NO2(-)-N L(-1), respectively. This study showed that nitrifying communities with high affinity for nitrite and low specific nitrite oxidation rates (K-strategists) can be strongly inhibited by NO. The degree of inhibition could be confirmed in a set-up with NO dosage through an artificial alginate-based biofilm, ensuring a more direct contact between NO and the microorganisms.

Control of aeration, aerobic SRT and COD input for mainstream nitritation/denitritation.

This work describes the development of an intermittently aerated pilot-scale process (V = 0.34 m(3)) operated without oxidized nitrogen recycle and supplemental carbon addition optimized for nitrogen removal via nitritation/denitritation. The aeration pattern was controlled using a novel aeration strategy based on set-points for reactor ammonia, nitrite and nitrate concentrations with the aim of maintaining equal effluent ammonia and nitrate + nitrite (NOx) concentrations. Further, unique operational and process control strategies were developed to facilitate the out-selection of nitrite oxidizing bacteria (NOB) based on optimizing the chemical oxygen demand (COD) input, imposing transient anoxia, aggressive solids retention time (SRT) operation towards ammonia oxidizing bacteria (AOB) washout and high dissolved oxygen (DO) (>1.5 mg/L). Sustained nitrite accumulation (NO2-N/NOx-N = 0.36 ± 0.27) was observed while AOB activity was greater than NOB activity (AOB: 391 ± 124 mgN/L/d, NOB: 233 ± 151 mgN/L/d, p < 0.001) during the entire study. The reactor demonstrated total inorganic nitrogen (TIN) removal rate of 151 ± 74 mgN/L/d at an influent COD/ [Formula: see text] -N ratio of 10.4 ± 1.9 at 25 °C. The TIN removal efficiency was 57  ±  25% within the hydraulic retention time (HRT) of 3 h and within an SRT of 4-8 days. Therefore, this pilot-scale study demonstrates that application of the proposed online aeration control is able to out-select NOB in mainstream conditions providing relatively high nitrogen removal without supplemental carbon and alkalinity at a low HRT.