Assessing membrane aerated biofilm reactor configurations in mainstream anammox applications.

Partial nitritation anammox (PNA) membrane aerated biofilm reactors (MABRs) have the potential to be employed in mainstream wastewater treatment and can drastically decrease the energy and carbon requirements for nitrogen removal. Previous PNA MABR studies have looked at 1-stage systems, but no study has holistically compared the performance of different MABR configurations. In this study, a PNA MABR was mechanistically modelled to determine the impact of the reactor configuration (1-stage, hybrid, or 2-stage system) on the location of the preferred niche for anammox bacteria and the overall nitrogen removal performance. Results from this study show that the 2-stage configuration, which used an MABR with a thin biofilm for nitritation and a moving bed biofilm reactor for anammox, had a 20% larger nitrogen removal rate than the 1-stage or hybrid configurations. This suggests that an MABR should focus on maximizing nitrite production with anammox implemented in a second-stage biofilm reactor to achieve the most cost-effective nitrogen removal. However, the optimal configuration will likely be facility specific, as each facility differs in operating costs, construction costs, footprint, and effluent limits. Additional experimentation is required to confirm these results, but this work narrows the number of viable configurations that need to be tested. The results of this study will inform researchers and engineers how to best implement PNA MABRs in mainstream nitrogen removal at larger scales.

A persistent recurring cluster of meticillin-resistant Staphylococcus aureus (MRSA) colonizations in a special care baby unit: a matched case-control study.

BACKGROUND: Between August 2016 and November 2019, a cluster of babies colonized with meticillin-resistant Staphylococcus aureus (MRSA) was reported in a special care baby unit in northern England. AIM: A case-control study was performed to identify the source and prevent further cases. METHODS: Cases were admitted neonates colonized or infected with MRSA (spa type t316). A retrospective case-control study was performed with two matched controls per case. Exposures were determined by medical record review. Cases were compared with controls using conditional logistic regression. Environmental investigations and staff screening were undertaken. FINDINGS: Thirty-one colonized cases were identified across the 3-year period, with no infections reported. Thirteen of the 31 cases were sequenced and were within a cluster of 25 single nucleotide polymorphisms, consistent with exposure to a common source over a prolonged period. Most MRSA cases had a prior negative screen (N=22, 71%). Environmental sampling and staff screening were performed on several occasions. In the analytical study, 31 cases were compared with 62 controls. One ward location and one healthcare worker were identified as significant exposures in the multi-variable analysis. CONCLUSIONS: Due to the sporadic nature of the colonizations, it was hypothesized that MRSA was being introduced intermittently, likely by a colonized healthcare worker, with possible transmission between infants also occurring within each temporal cluster. It is recommended that transiently colonized healthcare workers should be considered as a source of MRSA during outbreaks. This study highlights the importance of analytic epidemiological studies in persistent outbreaks of MRSA.

Multi-year diagnosis of unpredictable fouling occurrences in a full-scale membrane bioreactor.

The membrane bioreactor (MBR) at the Traverse City Regional Wastewater Treatment Plant has experienced sudden and unpredictable periods of substantial permeability decline since 2011. Early observations detected irregularly-shaped Gram-positive bacteria that correlated with plant upsets. Use of biomolecular techniques, such as DNA sequencing of laboratory isolates and the mixed liquor microbial community, and fluorescent in situ hybridization, identified the dispersed organisms as members of the genus Staphylococcus. However, Staphylococcus species were consistently present during normal operation and therefore were more likely to be an indicator of the upset, not the cause. The results suggest that these microorganisms are responding to specific influent wastewater constituents. We chemically analysed seven mixed liquor samples from periods of permeability decline in 2017 and 2018, and four samples from a period of normal operation. During upset conditions, the total carbohydrate content exceeded that of normal operation by 40%. Additionally, mixed liquor calcium concentrations were 65% above normal during the upset in 2017. It is hypothesized and supported through multivariate statistical analysis and estimation of specific resistance to filtration values that a calcium-intermediated polymer bridging mechanism with extracellular polymeric substance constituents is a major contributor to fouling and permeability disruptions in the Traverse City MBR.

Timely initiation of chemotherapy: a systematic literature review of six priority cancers - results and recommendations for clinical practice.

This review evaluated the association between time-to-chemotherapy (TTC) and survival in six priority cancers. A systematic review of the literature was undertaken for papers indexed in the MEDLINE and Cochrane Library databases from the earliest index until April 2014. The methodology used has been published in a separate paper (Guidelines for timely initiation of chemotherapy: a proposed framework for access to medical oncology and haematology cancer clinics and chemotherapy services). The optimal timing of chemotherapy in breast cancer is unclear as available studies are of low quality, report inconsistent results and are limited to the adjuvant setting. However, increased TTC may have a negative prognostic impact, and delays beyond 4 weeks should be avoided. Studies suggest that the optimal timing for initiation of adjuvant chemotherapy for surgically resected colorectal cancer is 4-8 weeks post-surgery. Timing of chemotherapy for metastatic colorectal cancer does not influence survival. There is a paucity of studies to guide the timing of chemotherapy for the treatment of lymphoma and myeloma; no definitive conclusions can be drawn, and clinician discretion should be applied. The optimal timing of chemotherapy in lung cancer is unclear; however, rapid tumour growth and poor disease prognosis suggest that delays should be avoided wherever possible. The optimal timing of chemotherapy in ovarian cancer is unclear as available studies are of low level, report inconsistent results and are limited to the post-surgery setting; however, increased TTC may have a negative prognostic impact; therefore, delays beyond 4 weeks should be avoided.

Guidelines for timely initiation of chemotherapy: a proposed framework for access to medical oncology and haematology cancer clinics and chemotherapy services.

These guidelines, informed by the best available evidence and consensus expert opinion, provide a framework to guide the timely initiation of chemotherapy for treating cancer. They sit at the intersection of patient experience, state-of-the-art disease management and rational efficient service provision for these patients at a system level. Internationally, cancer waiting times are routinely measured and publicly reported. In Australia, there are existing policies and guidelines relating to the timeliness of cancer care for surgery and radiation therapy; however, until now, equivalent guidance for chemotherapy was lacking. Timeliness of care should be informed, where available, by evidence for improved patient outcomes. Independent of this, it should be recognised that shorter waiting periods are likely to reduce patient anxiety. While these guidelines were developed as part of a proposed framework for consideration by the Victorian Department of Health, they are clinically relevant to national and international cancer services. They are intended to be used by clinical and administrative staff within cancer services. Adoption of these guidelines, which are for the timely triage, review and treatment of cancer patients receiving systemic chemotherapy, aims to ensure that patients receive care within a timeframe that will maximise health outcomes, and that access to care is consistent and equitable across cancer services. Local monitoring of performance against this guideline will enable cancer service providers to manage proactively future service demand.

Recommendations for standards of monitoring during anaesthesia and recovery 2015: Association of Anaesthetists of Great Britain and Ireland.

This guideline updates and replaces the 4th edition of the AAGBI Standards of Monitoring published in 2007. The aim of this document is to provide guidance on the minimum standards for physiological monitoring of any patient undergoing anaesthesia or sedation under the care of an anaesthetist. The recommendations are primarily aimed at anaesthetists practising in the United Kingdom and Ireland. Minimum standards for monitoring patients during anaesthesia and in the recovery phase are included. There is also guidance on monitoring patients undergoing sedation and also during transfer of anaesthetised or sedated patients. There are new sections discussing the role of monitoring depth of anaesthesia, neuromuscular blockade and cardiac output. The indications for end-tidal carbon dioxide monitoring have been updated.

Peri-operative care of the elderly 2014: Association of Anaesthetists of Great Britain and Ireland.

Increasing numbers of elderly patients are undergoing an increasing variety of surgical procedures. There is an age-related decline in physiological reserve, which may be compounded by illness, cognitive decline, frailty and polypharmacy. Compared with younger surgical patients, the elderly are at relatively higher risk of mortality and morbidity after elective and (especially) emergency surgery. Multidisciplinary care improves outcomes for elderly surgical patients. Protocol-driven integrated pathways guide care effectively, but must be individualised to suit each patient. The AAGBI strongly supports an expanded role for senior geriatricians in coordinating peri-operative care for the elderly, with input from senior anaesthetists (consultants/associate specialists) and surgeons. The aims of peri-operative care are to treat elderly patients in a timely, dignified manner, and to optimise rehabilitation by avoiding postoperative complications. Effective peri-operative care improves the likelihood of very elderly surgical patients returning to their same pre-morbid place of residence, and maintains the continuity of their community care when in hospital. Postoperative delirium is common, but underdiagnosed, in elderly surgical patients, and delays rehabilitation. Multimodal intervention strategies are recommended for preventing postoperative delirium. Peri-operative pain is common, but underappreciated, in elderly surgical patients, particularly if they are cognitively impaired. Anaesthetists should administer opioid-sparing analgesia where possible, and follow published guidance on the management of pain in older people. Elderly patients should be assumed to have the mental capacity to make decisions about their treatment. Good communication is essential to this process. If they clearly lack that capacity, proxy information should be sought to determine what treatment, if any, is in the patient's best interests. Anaesthetists must not ration surgical or critical care on the basis of age, but must be involved in discussions about the utility of surgery and/or resuscitation. The evidence base informing peri-operative care for the elderly remains poor. Anaesthetists are strongly encouraged to become involved in national audit projects and outcomes research specifically involving elderly surgical patients.

Impact of national guidelines on reporting anaphylaxis during anaesthesia -- an outcome audit.

AIMS: Anaphylaxis during anaesthesia is a rare and potentially fatal event. Adequate reporting and investigation of anaphylaxis associated with anaesthesia results in improved patient safety and outcomes. Guidelines from the Association of Anaesthetists of Great Britain and Ireland (AAGBI) designed to improve this process were first issued in 1990 and updated in 1995, 2003 and 2008. In a setting where no formal guideline was previously in place, we compared the reporting and investigation of anaphylaxis in a large hospital before and after the introduction of the 2008 guideline. METHODS: A retrospective outcome audit was conducted to compare data from 12 patients referred from April 2006 to May 2008 prior to release of the 2008 AAGBI guidance, with 53 patients referred from 2008 until April 2011. Data were collected using the AAGBI Anaphylaxis Referral Form. RESULTS: There was an increase in the number of referrals for suspected anaphylaxis following implementation of the AAGBI guidance. The clinical features observed in patients were consistent with previous studies. There was improved documentation of referral to local and national databases. Most cases resulted in cancellation of surgery, and there were no patient deaths. A substantial increase in the number of patients with amoxicillin allergy was noted in the second time period, which was linked to a change in the local perioperative antibiotic policy. CONCLUSIONS: Implementation of the AAGBI guidelines locally in a large hospital in 2008 resulted in an improved awareness of the importance of reporting and investigation of suspected anaphylaxis under anaesthesia. This tool was implemented coincidentally with the change in hospital antibiotic prophylaxis and enabled the cases detected to be accurately recorded and investigated. This led to a change in the hospital antibiotic policy for surgical prophylaxis. Implementation of structured guidance from a national anaesthesia organisation enhances recognition of the clinical features of anaphylaxis, increases number and completeness of referrals and more thorough immunological investigation, leading to improved patient safety during anaesthesia.

Elucidating the relative roles of ammonia oxidizing and heterotrophic bacteria during the biotransformation of 17α-Ethinylestradiol and Trimethoprim.

The biological fate of 17α-ethinylestradiol (EE2; 500 ng/L to 1 mg/L) and trimethoprim (TMP; 1 µg/L to 1 mg/L) was evaluated with flow through reactors containing an ammonia oxidizing bacterial (AOB) culture, two enriched heterotrophic cultures devoid of nitrifier activity, and nitrifying activated sludge (NAS) cultures. AOBs biotransformed EE2 but not TMP, whereas heterotrophs mineralized EE2, biotransformed TMP, and mineralized EE2-derived metabolites generated by AOBs. Kinetic bioassays showed that AOBs biotransformed EE2 five times faster than heterotrophs. The basal expression of heterotrophic dioxygenase enzymes was sufficient to achieve the high degree of transformation observed at EE2 and TMP concentrations ≤ 1 mg/L, and enhanced enzyme expression was not necessary. The importance of AOBs in removing EE2 and TMP was evaluated further by performing NAS experiments at lower feed concentrations (500-1000 ng/L). EE2 removal slowed markedly after AOBs were inhibited, while TMP removal was not affected by AOB inhibition. Two key EE2 metabolites formed by AOB and heterotrophic laboratory-scale chemostats were also found in independent laboratory-scale mixed culture bioreactors; one of these, sulfo-EE2, was largely resistant to further biodegradation. AOBs and heterotrophs may cooperatively enhance the reliability of treatment systems where efficient removal of EE2 is desired.

Multidetector computed tomography in large bowel lesions-a study of 100 cases.

This study aims to evaluate the role of multidetector computed tomography (MDCT) in detecting and classifying the large bowel lesions. A prospective study of 100 adult patients was conducted from June 2007 to October 2009. Rectal and IV contrast were used for three dimensional reconstruction. Angiography was performed in cases of suspected ischemic pathology. CT colongraphy was done to evaluate adenomas. CT findings were correlated and confirmed by either colonoscopy, biopsy, postoperative findings or follow-up CT. The pathologies were common in 50-70 yrs (44%). M: F ratio was 2:1. Malignant lesions were seen in (55%) followed by inflammatory lesions in 26%, diverticulitis and ischemic colitis in 6% each. Miscellaneous conditions like polyps, volvulus and intussusceptions were seen in 7%. Adenocarcinoma was the common malignancy (81.2%). Present study showed that adenocarcinomas were associated with marked thickening of bowel wall (>1.5 cm) in 85.4% of patients, asymmetrical wall thickening (96.4%), focal involvement (length <10 cm) in 85.5% with heterogeneous post contrast enhancement (96.3%). Inflammatory lesions showed mild thickening (69%),segmental or diffuse involvement (77%), symmetrical wall thickening (89%) and homogenous post contrast enhancement (81%). Ischemic lesions showed marked thickening (83.4%), symmetrical thickening (100%) and homogenous enhancement (100%). Diverticulitis showed marked thickening (100%), asymmetrical wall thickening (66.7%) with heterogeneous post contrast enhancement (100%), with pericolic fluid. Arterial/venous thrombosis was diagnosed in 66.66%. Three per cent had benign adenomatous polyps on CT colonographic studies. MDCT was accurate in 98.2% cases for differentiating between benign and malignant etiology and is the modality of choice.

Effect of diet on fecal and urinary estrogenic activity.

The United States Environmental Protection Agency has identified estrogens from animal feeding operations as a major environmental concern, but few data are available to quantify the excretion of estrogenic compounds by dairy cattle. The objectives of this study were to quantify variation in estrogenic activity in feces and urine due to increased dietary inclusion of phytoestrogens. Ten Holstein heifers were assigned to 2 groups balanced for age and days pregnant; groups were randomly assigned to treatment sequence in a 2-period crossover design. Dietary treatments consisted of grass hay or red clover hay, and necessary supplements. Total collection allowed for sampling of feed refusals, feces, and urine during the last 4 d of each period. Feces and urine samples were pooled by heifer and period, and base extracts were analyzed for estrogenic activity (estrogen equivalents) using the yeast estrogen screen bioassay. Feces and urine samples collected from 5 heifers were extracted and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to quantify excretion of 7 phytoestrogenic compounds. Excretion of 17-beta estradiol equivalents in urine was higher and tended to be higher in feces for heifers fed red clover hay (84.4 and 120.2 mg/d for feces and urine, respectively) compared with those fed grass hay (57.4 and 35.6 mg/d). Analysis by LC-MS/MS indicated greater fecal excretion of equol, genistein, daidzein, coumestrol, and formononetin by heifers fed red clover hay (1634, 29.9, 96.3, 27.8, and 163 mg/d, respectively) than heifers fed grass hay (340, 3.0, 46.2, 8.8, and 18.3 mg/d, respectively). Diet had no effect on fecal biochanin A or 2-carbethoxy-5, 7-dihydroxy-4'-methoxyisoflavone. Four phytoestrogens were detected in urine (2-carbethoxy-5, 7-dihydroxy-4'-methoxyisoflavone, daidzein, equol, and formononetin) and their excretion was not affected by diet. Identifying sources of variation in estrogenic activity of manure will aid in the development of practices to reduce environmental estrogen accumulation.

The use of qualitative system dynamics to identify sustainability characteristics of decentralized wastewater management alternatives.

In order to pursue more sustainable alternatives in wastewater management, it is vital that we understand how a given infrastructure alternative will impact the various aspects of sustainability. A set of qualitative tools (force field diagrams and causal loop diagrams (CLDs)) for the assessment of wastewater management alternatives is proposed and demonstrated in the context of a decentralized wastewater infrastructure upgrade. The objective for the application of these tools is to improve decision makers' understanding of how a given alternative will impact the economic, environmental/ecological, social, and functional aspects of sustainability. In the proposed method, each aspect of sustainability is treated as a stock, and its movement (up or down) can be inferred using both qualitative and quantitative data. By incorporating these tools into a participatory planning process, project-specific CLDs can be developed and loops of interest can be identified to help elucidate stakeholder values. The ultimate goal of this methodology is to facilitate the pursuit of sustainability in wastewater management by allowing decision makers to address specific sustainability challenges without creating new ones.

Characterization of metabolites formed during the biotransformation of 17alpha-ethinylestradiol by Nitrosomonas europaea in batch and continuous flow bioreactors.

The biotransformation of 17alpha-ethinylestradiol (EE2) by an ammonia oxidizing bacteria, Nitrosomonas europaea, grown in batch (ammonia-rich) and continuous flow (chemostat, ammonia-limited) reactors was investigated. Both C-14 labeled EE2 (10 gammag/L) and unlabeled EE2 (1 mg/L) were used to facilitate metabolite identification under environmentally relevant physiological conditions. Whole cell ammonia monooxygenase (AMO) activity was not inhibited at the EE2 concentrations used in this study. Characterization of the primary metabolite formed during batch cultivation by liquid chromatography/ion-trap mass spectrometry (LC-ITMS) and nuclear magnetic resonance (NMR) spectroscopy showed modification at the ethinyl group and addition of a carboxyl group. This metabolite (M386) (revealed by m/z 385 in negative mode electrospray LC/ MS) was not formed in the abiotic control. In contrast, biotransformation of EE2 under continuous flow conditions showed formation of a monohydroxylated EE2 (revealed by m/z 311), but not M386. Furthermore, nitrated EE2 derivatives were formed in both batch and continuous flow cultures, as a result of abiotic transformation of EE2 in the presence of high concentrations of nitrite in the bioreactors. Results from this study underscore the importance of physiological state and growth conditions as critical variables that can dictate the metabolic pathway for EE2 biodegradation and the nature of byproducts formed.

The value of Modified Early Warning Score (MEWS) in surgical in-patients: a prospective observational study.

INTRODUCTION: The Modified Early Warning Score (MEWS) is a simple, physiological score that may allow improvement in the quality and safety of management provided to surgical ward patients. The primary purpose is to prevent delay in intervention or transfer of critically ill patients. PATIENTS AND METHODS: A total of 334 consecutive ward patients were prospectively studied. MEWS were recorded on all patients and the primary end-point was transfer to ITU or HDU. RESULTS: Fifty-seven (17%) ward patients triggered the call-out algorithm by scoring four or more on MEWS. Emergency patients were more likely to trigger the system than elective patients. Sixteen (5% of the total) patients were admitted to the ITU or HDU. MEWS with a threshold of four or more was 75% sensitive and 83% specific for patients who required transfer to ITU or HDU. CONCLUSIONS: The MEWS in association with a call-out algorithm is a useful and appropriate risk-management tool that should be implemented for all surgical in-patients.

Chemical inhibition of nitrification in activated sludge.

Conventional aerobic nitrification was adversely affected by single pulse inputs of six different classes of industrially relevant chemical toxins: an electrophilic solvent (1-chloro-2,4-dinitrobenzene, CDNB), a heavy metal (cadmium), a hydrophobic chemical (1-octanol), an uncoupling agent (2,4-dinitrophenol, DNP), alkaline pH, and cyanide in its weak metal complexed form. The concentrations of each chemical source that caused 1 5, 25, and 50% respiratory inhibition of a nitrifying mixed liquor during a short-term assay were used to shock sequencing batch reactors containing nitrifying conventional activated sludge. The reactors were monitored for recovery over a period of 30 days or less. All shock conditions inhibited nitrification, but to different degrees. The nitrate generation rate (NGR) of the shocked reactors recovered overtime to control reactor levels and showed that it was a more sensitive indicator of nitrification inhibition than both initial respirometric tests conducted on unexposed biomass and effluent nitrogen species analyses. CDNB had the most severe impact on nitrification, followed by alkaline pH 11, cadmium, cyanide, octanol, and DNP. Based on effluent data, cadmium and octanol primarily inhibited ammonia-oxidizing bacteria (AOB) while CDNB, pH 11,and cyanide inhibited both AOB and nitrite-oxidizing bacteria (NOB). DNP initially inhibited nitrification but quickly increased the NGR relative to the control and stimulated nitrification after several days in a manner reflective of oxidative uncoupling. The shocked mixed liquor showed trends toward recovery from inhibition for all chemicals tested, but in some cases this reversion was slow. These results contribute to our broader effort to identify relationships between chemical sources and the process effects they induce in activated sludge treatment systems.

Deflocculation effects due to chemical perturbations in sequencing batch reactors.

Toxic shock-induced deflocculation was examined for activated sludge exposed to six different classes of industrially relevant chemical toxins: an electrophilic solvent (1-chloro-2,4-dinitrobenzene, CDNB), a heavy metal (cadmium), a hydrophobic chemical (1-octanol), an uncoupling agent (2,4-dinitrophenol, DNP), alkaline pH, and weakly complexed cyanide. The concentrations required to inhibit respiration by 50% were used to shock sequencing batch reactors (SBRs) containing a nitrifying (10-day solids retention time (SRT)) and a non-nitrifying (2-day SRT) biomass. Effluent total suspended solids (TSS) and soluble potassium were monitored to examine deflocculation caused by a bacterial stress response mechanism called glutathione-gated potassium efflux (GGKE). Reactors were monitored for recovery over a period of 3 SRTs or less. At the concentrations tested, CDNB, cadmium and pH 11 were found to cause significant increases in effluent TSS concentrations and showed elevated levels of potassium. In contrast, octanol, DNP and cyanide did not induce severe deflocculation and showed moderate increases in effluent potassium levels. Recovery of effluent TSS and potassium concentrations to control levels generally did not correlate, supporting the hypothesis that reflocculation requires regrowth of biomass. These results suggest that different chemicals induce deflocculation in SBRs, but deflocculation is not necessarily caused by the GGKE mechanism in all cases.

Evaluating the role of microbial stress response mechanisms in causing biological treatment system upset.

It is known that microbial stress mechanisms play a significant role in short-term microbial adaptation to environmental perturbations, and activation of these mechanisms enhance a cell's chance for surviving the perturbation with minimal damage. Although the target of these mechanisms is protective at the cellular level, the effect may be disruptive at the macroscopic level in engineered bioreactor systems. In this paper, it is proposed that these mechanisms are activated in response to wastewater influent perturbations and may be a significant cause of activated sludge treatment process upset. Selected microbial stress responses are reviewed and hypotheses indicating their potential role in treatment process upset are proposed. A research approach that was previously used to identify the mechanistic cause of deflocculation during perturbation by electrophilic chemicals is summarized, and a protocol for future experiments geared toward establishing source-cause-effect relationships for a range of wastewater upset conditions is put forth. Identifying source-cause-effect relationships will provide a basis for development of new monitoring technologies and operational strategies for systems under the influence of influent chemical perturbations.

Stress protein expression in domestic activated sludge in response to xenobiotic shock loading.

Using the Western blot immunochemical analysis method, the heat shock protein, GroEL, was found to be either induced or repressed in activated sludge microorganisms exposed to a range of xenobiotics. At the EC25 concentration, pentachlorophenol (PCP), cadmium, nickel, 2,4-dichloroaniline, benzoquinone, 2,4-dinitrophenol, and 1,1,1-trichloroethane all rapidly induced measurable GroEL expression, even though the time-dependent response for each of these compounds was somewhat varied. Toluene and hydroquinone resulted in repression of GroEL expression to levels below that measured in the control mixed liquor. For PCP concentrations at or exceeding the EC25, there was a significant and consistent increase in effluent volatile suspended solids from activated sludge sequencing batch reactors relative to unstressed controls. These preliminary results indicate that stress proteins may serve as sensitive and rapid indicators of toxicity which can adversely impact treatment process performance in activated sludge systems.

Creating anoxic and microaerobic conditions in sequencing batch reactors treating volatile BTX compounds.

An experimental strategy is introduced for studying the biodegradation of wastewaters containing volatile contaminants using an alternating anoxic/microaerobic sequencing batch reactor (SBR). Benzene, toluene, and the xylene isomers (BTX) served as model volatile contaminants for this study. The reactor was configured to overcome stripping the volatile BTX compounds into the atmosphere to provide opportunities for BTX biodegradation. Oxygen-free anoxic and microaerobic (< 0.2 mg/L dissolved oxygen) conditions were established using a novel laboratory reactor configuration. ORP was successfully used to monitor different electron acceptor conditions in the SBR. Toluene and m-xylene were amenable to anoxic (denitrifying) metabolism while benzene, o-, and p-xylene were biodegradable under microaerobic conditions. The results demonstrate that establishing microaerobic conditions in full-scale bioreactors may be an appropriate way to encourage the biodegradation of aerobically biodegradable volatile contaminants. Additionally, the laboratory reactor configuration introduced in this paper may be useful in subsequent studies involving microaerobic metabolism.