Insights into selenate removal mechanism of hydrogen-based membrane biofilm reactor for nitrate-polluted groundwater treatment based on anaerobic biofilm analysis

The selenate removal mechanism of hydrogen-based membrane biofilm reactor (MBfR) for nitrate-polluted groundwater treatment was studied based on anaerobic biofilm analysis. A laboratory-scale MBfR was operated for over 60 days with electron balance, structural analysis, and bacterial community identification. Results showed that anaerobic biofilm had an excellent removal of both selenate (95%) and nitrate (100%). Reduction of Selenate → Selenite → Se⁰ with hydrogen was the main pathway of anaerobic biofilm for selenate removal with amorphous Se⁰ precipitate accumulating in the biofilm. The element selenium was observed to be evenly distributed along the cross-sectional thin biofilm. A part of selenate (3%) was also reduced into methyl-selenide by heterotrophic bacteria. Additionally, Hydrogenophaga bacteria of β-Proteobacteria, capable of both nitrate and selenate removal, worked as the dominant species (over 85%) in the biofilm and contributed to the stable removal of both nitrate and selenate. With the selenate input, bacteria with a capacity for both selenate and nitrate removal were also developed in the anaerobic biofilm community.

Promoting waste activated sludge reduction by linear alkylbenzene sulfonates: Surfactant dose control extracellular polymeric substances solubilization and microbial community succession

Short-time aerobic digestion (STAD) was proved to promote the reduction of waste activated sludge (WAS). This study systematically disclosed the influential characteristics and mechanisms of linear alkylbenzene sulfonates (LAS) dosage on the reduction of WAS in STAD system. Flow cytometer (FC) combined with SYTOX Green (SG) dye was used to differentiate extracellular polymeric substances (EPS) release and cell lysis of WAS during STAD process. LAS lower than 0.10 g/g total suspended solids (TSS) brought about EPS solubilization and the decrease of sludge floc size, and the accumulated soluble microbial products (SMP) could be biodegraded by heterotrophs. Moreover, the activity of microorganisms (denoted as specific oxygen uptake rate (SOUR)) and proportion of bacteria functional for LAS and SMP biodegradation dramatically increased, leading to a high LAS biodegradation rate (k_LAS) and increased WAS biodegradation rate (k_{COD, WAS}). Even more LAS (> 0.10 g/g TSS) caused cell lysis, leading to the decreased k_TCOD and k_LAS, and therefore inhibit the reduction of WAS. High WAS reduction and LAS biodegradation rate were achieved at the LAS dosage of 0.10 g/g TSS in STAD system. This study lays the foundation for improving WAS reduction by optimizing surfactant dose in STAD system.

Electron donation characteristics and interplays of major volatile fatty acids from anaerobically fermented organic matters in bioelectrochemical systems

Anaerobic fermentation liquid of waste organic matters (WOMs) is rich in volatile fatty acids (VFAs), which can be treated with bioelectrochemical systems for both electrical energy recovery and organics removal. In this work, four major VFAs in the fermented WOMs supernatant were selected to examine their electron donation characteristics for power output and their complicated interplays in microbial fuel cells (MFCs). Results indicated a priority sequence of acetate, propionate, n-butyrate and i-valerate when served as the sole electron donor for electricity generation. The MFC solely fed with acetate showed the highest coulombic efficiency and power density, and the longest period for electricity production. When two of the VFAs were added with equal proportion, both acids contributed positively to electricity generation, while the selective or competitive use of substrates by diverse microorganisms behaved as an antagonism effect to prolong the degradation time of each VFA. When acetate and propionate, the preferable substrates for electricity generation, were mixed in various proportions, their large concentration difference led to improved electrical performance but decreased organic removal rate.

Electrochemical acidolysis of magnesite to induce struvite crystallization for recovering phosphorus from aqueous solution

A novel struvite crystallization method induced by electrochemical acidolysis of cheap magnesite was investigated to recover phosphorus from aqueous solution. Magnesite was confirmed to continuously dissolve in the anolyte whose pH stabilized at about 2. Driven by the electrical field force, over 90% of the released Mg²⁺ migrated to the cathode chamber via passing through the cation exchange membrane. The pH of the phosphate-containing aqueous solution in the cathode chamber was elevated to the appropriate pH fit for struvite crystallization. The products were identified as struvite crystals by scanning electron microscopy and X-ray diffraction. Increasing the magnesite dosage from 0.83 to 3.33 g L^-1 promoted the phosphorus recovery efficiency from 2.2% to 78.3% at 3 d, which was attributed to sufficient Mg²⁺ supply. Increasing the applied voltage from 3 to 6 V improved the recovery efficiency from 43.6% to 76.4% at 1 d, since the enhanced current density of the electrochemical system markedly accelerated both the magnesite acidolysis and the catholyte pH elevation. The initial catholyte pH between 3 and 5 was found to benefit the phosphorus recovery due to the final catholyte pH fit for the struvite crystallization.

Potential effects of suspended TiO2 nanoparticles on activated sludge floc properties in membrane bioreactors

With the rapid development and application of consumer products containing nanoparticles (NPs), especially titanium dioxide (TiO₂) NPs, the potential effects of suspended NPs on wastewater treatment has been a concern over the recent years. This study investigated the potential effects of suspended TiO₂ NPs on activated sludge flocculation properties in a membrane bioreactor (MBR). Results showed that suspended TiO₂ NPs inhibited the viability of activated sludge flocs, and led to bacterial protein secretion for bacterial protection, causing an overall protein increase of soluble microbial products. Suspended TiO₂ NPs also destabilized the activated sludge floc structure and reduced flocculation capacity of flocs, causing an over production of organic matter and resulting in a floc size decrease of over 50%. Suspended TiO₂ NPs also caused a change in the phylogenetic distribution of bacterial community. Whereby, the dominant species in activated sludge was replaced from Comamonadaceae to Thiotrichaceae in 50 mg/L suspended TiO₂ NPs.

Enhancement of nitrogen removal by supplementing fluidized-carriers into the aerobic tank in a full-scale A2/O system

Fluidized-carriers were supplemented into the aerobic tank of a full-scale wastewater treatment plant (WWTP) using an anaerobic/anoxic/aerobic (A²/O) system to improve the nitrogen removal efficiency in effluents. The effects of carrier supplementation on denitrification ability and the bacterial community structures were investigated over 10 months. The results showed that the average effluent concentration of total nitrogen (TN) was maintained at 9.46 ± 1.14 mg/L, which was lower than 15.17 ± 2.00 mg/L in the effluent without carrier supplementation, indicating that adding fluidized-carriers into the aerobic tank contributed to nitrogen removal efficiency. A thick biofilm was formed after 4 months, which provided a good anoxic-aerobic microenvironment to the microbes. Illumina sequencing analysis showed a higher bacterial diversity in the biofilm. The relative abundance of nitrifying bacteria, denitrifying bacteria, and aerobic denitrifying bacteria in the biofilms was 13.68-39%, 11.56-12.17%, and 9.76-12.50%, respectively, which was beneficial for nitrogen removal in the system. The most prevalent genera were Nitrospira, Bacillus, Thauera, Hyphomicrobium, Acinetobacter, Zoogloea, Pseudomonas, and Paracoccus, which can metabolize nitrogenous or aromatic compounds and were the major functional bacterial genera, suggesting that these organisms play key roles in biodegradation processes in the carrier-added A²/O wastewater treatment system.

Structural characteristics of cake layer in membrane bioreactor with chromate exposure

Chromate (CrO₄^2-) exposure, especially high concentration (mg/L), still probably occurs in the industrial and mining area due to industrial accidents or even illegal discharge, though CrO₄^2- has been restricted to be discharged into wastewater treatment system (WWTS). Therefore, this study was applied to better understand the structural characteristics of cake layer in membrane bioreactor (MBR), which is one of best alternative for WWTS of industrial or mining area, with CrO₄^2- exposure. Three submerged MBRs with CrO₄^2- exposure (10 mg/L was normal high concentration CrO₄^2-; 50 mg/L as extreme level for better identification; 0 mg/L as control condition) were applied in this study. Results showed that CrO₄^2- exposure caused an obvious variation of cake layer structure. Because of organic component variation, cake layer structure with CrO₄^2- exposure was re-constructed into loose and porous with biomicromolecules, and resulted in the rapid cake layer thickness increase, finally leading to severe membrane biofouling. Additionally, CrO₄^2- distributed evenly along the cross-sectional cake layer. CrO₄^2- only induced the inorganic structure variations of cake layer, but without any obvious effects on the other inorganic elements structure. CrO₄^2- exposure induced the bacterial community structure variation and led to tolerated-CrO₄^2- microorganisms as the majority in cake layer community, but had no obvious effects on the population diversity.

Quick start-up and stable operation of a one-stage deammonification reactor with a low quantity of AOB and ANAMMOX biomass

In this study, a quick start-up of one-stage deammonification in an immobilized aerobic ammonium oxidizing bacteria (AOB) and anoxic ammonium oxidizing (ANAMMOX) bacteria up-flow reactor (IAAR) was successfully achieved. With the aid of gel layers, AOB and ANAMMOX bacteria had excellent spatial distribution, theoretically meeting dissolved oxygen requirements for the simultaneous processes of aerobic and anaerobic ammonium oxidizing. The results indicated that an IAAR containing 0.4 g-VSS L^-1 immobilized biomass achieved a nitrogen removal rate (NRR) of 0.53 kg-N m^-3 d^-1 after only 10 days of operation and subsequently reached a maximum nitrogen removal rate (NRR_max) of 3.73 kg-N m^-3 d^-1. The micro-profiles of DO and pH were measured using microelectrodes to help understand the stratification of the microbial processes inside the gel layers. The distribution of AOB and ANAMMOX bacteria within the gel layers was verified using fluorescence in situ hybridization (FISH) analysis. The community distribution in the FISH three-dimensional images closely corresponded to the micro-profiles of DO concentration and pH, enabling rapid adaptation and stable operation of the reactor seeded with a quite low quantity of biomass.

Uptake of phosphate by Synechocystis sp. PCC 6803 in dark conditions: Removal driving force and modeling

Rapid uptake of inorganic phosphate (Pi) by microalgae should occur through two processes operating in parallel: onto extracellular polymeric substances (EPS) and intracellular polymeric substances (IPS). Most previous studies focused only on overall Pi uptake and ignored the roles of EPS. We investigated the two-step removal of Pi by Synechocystis sp. PCC 6803 in dark conditions (i.e., without incorporation of Pi into newly synthesized biomass). We also developed a model to simulate both steps. Experimental results with Synechocystis confirmed that Pi in the bulk solution was removed by the two uptake mechanisms operating in parallel, but with different kinetics. All uptake rates decreased with time, and the Pi uptake rate by IPS was much higher than that by EPS at all times, but EPS had a larger maximum Pi-storage capacity -- 33-48 mgP/gCOD_EPS versus 15-17 mgP/gCOD_IPS. Synechocystis had a maximum Pi-storage capacity in the range of 22-28 mgP/g dry biomass. Protein in EPS and IPS played the key role for binding Pi, and biomass with higher protein content had greater Pi-storage capacity. Furthermore, biomass with low initial stored Pi had faster Pi-uptake kinetics, leading to more Pi removed from the bulk solution. This work lays the foundation for using microalgae as a means to remove Pi from polluted water and for understanding competition for Pi in microbial communities.

pH dependent of the waste activated sludge reduction by short-time aerobic digestion (STAD) process

The short-time aerobic digestion (STAD) process has been found to be a unique and significant technique for the stabilization of waste activated sludge (WAS), but the influences of the system pH on the STAD process was unclear. This study systematically disclosed the influences of the system pH on the STAD process of WAS. Under neutral or weak alkaline conditions, although the biodegradation rates of VSS (~0.0085 h^-1) were low, high biodegradation rates of TCOD (k_TCOD) (~0.0096 h^-1) were achieved. Less releases of the biopolymers from the WAS led to low concentrations of STOC, UV₂₅₄, the low MW organic matters, NH₄⁺ - N and PO₄^3- - P in the supernatant. However, the appropriate pH for the microorganisms improved SOUR, indicating that the released substances were further reused or biodegraded by the microorganisms. Under acidic or alkaline conditions, the biodegradation rates of VSS (0.009-0.019 h^-1) and TCOD (k_TCOD) (0.005-0.009 h^-1) were opposite with those under neutral or weak alkaline conditions. The releases of the biopolymers were increased, leading to high concentrations of STOC, UV₂₅₄, the low MW organic matters, PO₄^3- - P and NH₄⁺ - N in the supernatant. However, the extreme pH inhibited the microbial activity. The SOURs were only 0.0097 h^-1 and 0.0053 h^-1 for system pH of 8.0 and 4.0, respectively. Accordingly, neutral and weak alkaline conditions should be more suitable for the STAD process of WAS. This work lays the foundation for optimizing system pH for the reduction of WAS in STAD system.

Removal Efficacy of Opportunistic Pathogens and Bacterial Community Dynamics in Two Drinking Water Treatment Trains

Drinking water treatment processes (DWTPs) impact pathogen colonization and microbial communities in finished water; however, their efficacies against opportunistic pathogens are not fully understood. In this study, the effects of treatment steps on the removal of Legionella spp., Legionella pneumophila, nontuberculous mycobacteria, Mycobacterium avium, and two amoeba hosts (Vermamoeba vermiformis, Acanthamoeba) are evaluated in two parallel trains of DWTPs equipped with different pretreatment units. Quantitative polymerase chain reaction analysis demonstrates significantly reduced numbers of total bacteria, Legionella, and mycobacteria during ozonation, followed by a rebound in granular activated carbon (GAC) filtration, whereas sand filtration exerts an overarching effect in removing microorganisms in both treatment trains. V. vermiformis is more prevalent in biofilm (34%) than water samples (7.7%), while Acanthamoeba is not found in the two trains of DWTPs. Illumina sequencing of bacterial 16S rRNA genes reveals significant community shifts at different treatment steps, as well as distinct bacterial community structures in water and biofilm samples in parallel units (e.g., ozonation, GAC, sand filtration) between the two trains (analysis of similarities (ANOSIM), p < 0.05), implying the potential influence of different pretreatment steps in shaping the downstream microbiome. Overall, the results provide insights to mitigation of opportunistic pathogens and engineer approaches for managing bacterial communities in DWTPs.

Nitrogen aeration alters the spatial distribution and metal adsorption of extracellular polymeric substances in waste-activated sludge

Extracellular polymeric substances (EPS) extracted from waste-activated sludge (WAS) have the potential to remove heavy metal ions from wastewater; both the spatial distribution and metal adsorption of EPS from WAS after nitrogen aeration were systematically investigated in this study. Compared with air aeration, nitrogen aeration significantly improved the contents of proteins (PN) and polysaccharides (PS) in the Slime-EPS (S-EPS) and loosely-bound EPS (LB-EPS), significantly increased the PS content, and slightly increased the PN content in the tightly-bound EPS (TB-EPS). The variations in the fluorescence intensities (FI) of the peaks I and II for the S-EPS, LB-EPS and TB-EPS were basically consistent with the abovementioned variations in the concentrations of these EPS. Notably, nitrogen aeration dramatically improved the content of protein-like substances in the LB-EPS. For the same aeration time, the Pb²⁺ reclamation rates obtained by the LB-EPS extracted from the nitrogen-aerated WAS were much higher than those achieved by the LB-EPS extracted from the air-aerated WAS. The FTIR analyses further indicated that nitrogen aeration improved the contents of the functional groups, especially –OH, –COOH and –NH₂, responsible for binding heavy metals, in both the LB-EPS and TB-EPS. The SEM analyses verified that the nitrogen scours contributed to the EPS release, and Pb²⁺ reclamation was achieved via the attachment of Pb²⁺ onto the edge of the EPS. The influences of the nitrogen aeration on the spatial distribution and metal adsorption of the EPS in WAS were revealed for the first time in this study. Thus, this study lays the foundation for the application of nitrogen aeration in the resource utilization of WAS.

Nitrogen aeration was superior to air aeration because of the higher EPS production and Pb²⁺ adsorption in the utilization of WAS.

The effect of maternal low flow oxygen administration during the second stage of labour on umbilical cord artery pH: a randomised controlled trial

OBJECTIVE

To assess the effect of maternal low flow oxygen administration during the second stage of labour on umbilical cord artery pH.

DESIGN

A randomised controlled trial.

SETTING

A tertiary teaching hospital in China.

POPULATION

Women in the second stage of labour with no complications.

METHODS

About 443 women were randomly allocated to receive either supplemental oxygen at a flow rate of 2 l/min or a sham supplementation by nasal cannula. Healthcare providers, women and outcome assessors were blinded to allocation.

MAIN OUTCOME MEASURES

Umbilical cord artery pH and fetal heart rate (FHR) pattern.

RESULTS

Baseline characteristics were similar between the two groups. There were no significant differences between the two groups in the umbilical cord artery pH [median 7.261, interquartile range (IQR) 7.228-7.295 versus 7.266 (IQR 7.232-7.297), P = 0.64], the proportion with pH less than 7.2 [30/219 versus 34/224, P = 0.66, RR (relative risk) 0.9, 95% CI 0.57-1.42], and the proportion with normal FHR pattern (147/219 versus 153/224, P = 0.79, RR 0.98, 95% CI 0.86-1.12). Maternal partial pressure of dissolved oxygen was significantly higher in the oxygen group than in the sham group [median 150.0 mmHg (IQR 142.6-156.7) versus 112.0 (IQR 104.8-118.3), P < 0.001], whereas carbon dioxide was significantly lower in the oxygen group than in the sham group (mean difference -1.1, 95% CI -2.1 to -0.1, P = 0.03).

CONCLUSION

The use of 2 l/min maternal oxygen during the second stage of labour did not adversely affect either the umbilical artery pH or the FHR pattern distribution.

TWEETABLE ABSTRACT

No difference in abnormal fetal acid base or normal heart rate if maternal O₂ given, randomised trial finds.

Simultaneously enhanced biopolymers production and sludge dewaterability of waste activated sludge by synergetic integration process of short-time aerobic digestion with cocoamidopropyl betaine and calcium oxide

Waste activated sludge (WAS) has seriously threatened the environment safety and the public health due to its rapid growth and complex components. Simultaneously enhanced the biopolymers production and the sludge dewaterability of WAS were investigated by synergetic integration process of the short-time aerobic digestion (STAD) with cocoamidopropyl betaine (CAPB) and calcium oxide (CaO). STAD could improve the biopolymers production by biosynthesis. CAPB could further significantly enhance the biopolymers production and optimized the constituents. CaO (0.1-0.2 g/g TSS) could dramatically enhance the sludge dewaterability by forming a multi-grid skeleton in WAS, while the biopolymers production could almost remain stable. Especially, the synergetic integration process of STAD with 0.1 g CAPB/g TSS for 8 h and 0.1 g CaO/g TSS could cost-effectively enhance both the biopolymers production and the sludge dewaterability. The produced biopolymers showed strong adsorbability for heavy metals (eg, 375 mg Cu²⁺/g biopolymers). Accordingly, the developed novel process is of big significance for resource utilization and volume reduction of WAS.

Dynamic response of biofilm microbial ecology to para-chloronitrobenzene biodegradation in a hydrogen-based, denitrifying and sulfate-reducing membrane biofilm reactor

The dynamic response of biofilm microbial ecology to para-chloronitrobenzene (p-CNB) biodegradation was systematically evaluated according to the composition and loading of electron acceptors and H₂ availability (controlled by H₂ pressure) in a hydrogen-based, denitrifying and sulfate-reducing membrane biofilm reactor (MBfR). To accomplish this, a laboratory-scale MBfR was set up and operated with different influent p-CNB concentrations (0, 2, and 5 mg p-CNB/L) and H₂ pressures (0.04 and 0.05 MPa). Polymerase chain reaction-denaturing gel electrophoresis (PCR-DGGE) and cloning were then applied to investigate the bacterial diversity response of biofilm during p-CNB biodegradation. The results showed that denitrification and sulfate reduction largely controlled the total demand for H₂. Additionally, the DGGE fingerprint demonstrated that the addition of p-CNB, which acted as an electron acceptor, was a critical factor in the dynamics of the MBfR biofilm microbial ecology. The presence of p-CNB also had a more advantageous effect on the biofilm microbial community. Additionally, clone library analysis showed that Proteobacteria (especially beta- and gamma-) comprised the majority of the microbial biofilm response to p-CNB biodegradation, and that Pseudomonas sp. (Gammaproteobacteria) played a significant role in the biotransformation of p-CNB to aniline.

Inhibition of anammox by sludge thermal hydrolysis and metagenomic insights

Anaerobic ammonium oxidation (anammox) would be a feasible treatment method for thermal hydrolysis processed sidestream (THPS). Short-term study revealed that the 1/20 diluted THPS caused a 28% decrease of specific anammox activity. The MBR achieved a volumetric nitrogen loading rate of 3.64 kg/(m³·d) with undiluted regular sidestream (RS) fed, while the reactor crashed with 70% diluted THPS as feed. The ratio of produced NO₃^--N to consumed NH₄⁺-N also decreased compared with RS feeding. Candidatus brocadia was the major anammox bacteria species with the average abundance of 33.3% (synthetic wastewater), 6.42% (RS) and 2.51% (THPS). The abundances of metagenome bins for dissimilatory nitrate reduction to ammonium (DNRA) increased in the system with THPS compared with RS. The reason for the inhibition of anammox by THPS could be the high content of organic carbon in THPS, which caused the over-population of heterotrophic bacteria, i.e. DNRA bacteria, leading to anammox bacteria washout.

Complete dechlorination and mineralization of pentachlorophenol (PCP) in a hydrogen-based membrane biofilm reactor (MBfR)

Complete biodegradation and mineralization of pentachlorophenol (PCP), a priority pollutant in water, is challenging for water treatment. In this study, a hydrogen (H₂)-based membrane biofilm reactor (MBfR) was applied to treat PCP, along with nitrate and sulfate, which often coexist in contaminated groundwater. Throughout 120-days of continuous operation, almost 100% of up to 10 mg/L PCP was removed with minimal intermediate accumulation and in parallel with complete denitrification of 20 mg-N/L nitrate. PCP initially was reductively dechlorinated to phenol, which was then mineralized to CO₂ through pathways that began with aerobic activation via monooxygenation by Xanthobacter and anaerobic activation via carboxylation by Azospira and Thauera. Sulfur cycling induced by SO₄^2- reduction affected the microbial community: The dominant bacteria became sulfate-reducers Desulfomicrobium, sulfur-oxidizers Sulfuritalea and Flavobacterium. This study provides insights and a promising technology for bioremediation of water contaminated with PCP, nitrate, and sulfate.

Effects of sulfate on simultaneous nitrate and selenate removal in a hydrogen-based membrane biofilm reactor for groundwater treatment: Performance and biofilm microbial ecology

Effects of sulfate on simultaneous nitrate and selenate removal in a hydrogen-based membrane biofilm reactor (MBfR) for groundwater treatment was identified with performance and biofilm microbial ecology. In whole operation, MBfR had almost 100% removal of nitration even with 50 mg mL^-1 sulfate. Moreover, selenate degradation increased from 95% to approximate 100% with sulfate addition, indicating that sulfate had no obvious effects on nitrate degradation, and even partly promoted selenate removal. Short-term sulfate effect experiment further showed that Gibbs free energy of reduction (majority) and abiotic sulfide oxidation (especially between sulfate and selenate) contributed to degradable performance with sulfate. Microbial ecology showed that high percentage of Hydrogenophaga (≥75%) was one of the contributors for the stable and efficient nitrate degradation. Chemoheterotrophy (ratio>0.3) and dark hydrogen oxidation (ratio>0.3) were the majority of functional profile for biofilm in MBfR, and sulfate led to profiles of sulfate respiration and respiration of sulfur compounds in biofilm. Additionally, no special bacteria for selenate degradation was identified in biofilm microbial ecology, and selenate degradation was relied on Hydrogenophaga (75% of ecology percentage with sulfate addition) and Desulfovibrionaceae (4% of ecology percentage with sulfate addition). But with overloading sulfate, Desulfovibrionaceae was prior to sulfate degradation for energy supply and thus inhibited selenate removal.

Halomonas sp. strain A55, a novel dye decolorizing bacterium from dye-uncontaminated Rift Valley Soda lake

Considering the saline-alkaline nature of textile wastewater and treatment requirements, microbial samples were collected from Ethiopian Rift Valley Soda Lakes. A large number of bacteria (121) were isolated from dye-uncontaminated Lakes Chitu (81.0%), Abijata (15.7%) and Arenguadie (3.3%), of which 95 isolates (78.5%) were found dye decolorizer. Many dye decolorizer from Lake Chitu positively correlated with higher pH (10.3 ± 0.1), salinity (64.6 ± 2.0%), conductivity (6.1 ± 0.3 mS cm^-1) and Na+ (18.4 ± 0.6 g L^-1) values observed than Abijata and Arenguadie Lakes. Through subsequent screening mechanism, strain A55 was selected to investigate the effect of nutrient (carbon and nitrogen), dissolved oxygen and dye concentration using Reactive Red 184 (RR 184). Based on morphological, biochemical and 16S rRNA gene sequence analysis, the strain was identified as Halomonas sp. Decolorization efficiencies were significantly enhanced with carbon (≥98%) and organic nitrogen (∼100%) than non-carbon/nitrogen (both<55%) supplements. Complete decolorization efficiencies were also observed under anoxic and anaerobic growth conditions. However, growing the isolate with nitrate (<30%) and aerobic (<10%) condition significantly decreased (p < 0.05) color removal efficiency. Kinetic analysis showed that pseudo-first-order best describes RR 184 decolorization process. Overall, the ability of Halomonas sp. strain A55 decolorized different dyes indicate that alkaline soda lake isolates are the potential candidate for treating color containing effluent.

Meta-analysis examining the epidemiology of clozapine-associated neutropenia

BACKGROUND

Clozapine is associated with life-threatening neutropenia. There are no previous meta-analyses of the epidemiology of clozapine-associated neutropenia.

OBJECTIVES

To determine the cumulative incidence of mild, moderate and severe neutropenia, incidence of death related to severe neutropenia, case fatality rate of neutropenia and the longitudinal incidence of neutropenia following exposure to clozapine.

DATA SOURCES

A systematic search of Medline, EMBASE and PsycINFO using search terms [clozapine OR clopine OR zaponex OR clozaril] AND [neutropenia OR agranulocytosis].

METHODS

Random effects meta-analysis to determine event rates and longitudinal incidence of events per 100 person-years of exposure.

RESULTS

A total of 108 studies were included. The incidence of clozapine-associated neutropenia was 3.8% (95% CI: 2.7-5.2%) and severe neutropenia 0.9% (95% CI: 0.7-1.1%). The incidence of death related to neutropenia following prescription of clozapine was 0.013% (95% CI: 0.01-0.017%). The case fatality rate of severe neutropenia was 2.1% (95% CI: 1.6-2.8%). The peak incidence of severe neutropenia occurred at one month of exposure and declined to negligible levels after one year of treatment.

CONCLUSION

Severe neutropenia associated with clozapine is a rare event and occurs early with a substantial decline in risk after one year of exposure. Death from clozapine-associated neutropenia is extremely rare. Implications for haematological monitoring are discussed.