reelatha S

Solid electron acceptor effect on biocatalyst activity in treating azo dye based wastewater

The functional activity of anaerobic bacteria in the presence of an electrode as solid electron acceptor was comprehensively evaluated during the treatment of azo dye based wastewater. The experiments were performed in three different reactor setups, viz., bio-electrochemical treatment (BET; with electrode assembly and anaerobic biocatalyst), anaerobic treatment (AnT; with anaerobic biocatalyst and absence of electrode assembly) and abiotic reactor (control; with electrode assembly and absence of anaerobic biocatalyst) with 50 mg l−1 azo dye concentration. Maximum dye removal was observed with BET (69.9%) followed by AnT (42%) and control (2.4%). The bioelectrogenic performance was observed to be higher in BET (92.1 mW m−2) in comparison to abiotic-control (0.41 mW m−2), which is attributed to the significant influence of bacteria as biocatalyst in concurrence with the function of the electrode as solid electron acceptor in BET. The study also documented electron acceptor dependent respiration, exemplifying the influence of conjunction between electrode and bacteria on dye degradation. Two possible electron transfer mechanisms, viz., direct electron transfer (DET) through the membrane bound cytochromes to the solid electron acceptor and mediated electron transfer (MET) through reduced dye intermediates as electron shuttles, were observed during BET operation. However, AnT and abiotic control operation resulted in less and no dye breakdown, respectively, due to the lack of conjunction between the biocatalyst and electrode. The study provides a new insight into the electron acceptor dependent respiration wherein the electrode serving as a solid electron acceptor enables efficient function of anode respiring bacteria (ARB) in terms of electron flux towards dye degradation and electrogenesis.

Functional behavior of bio-electrochemical treatment system with increasing azo dye concentrations: Synergistic interactions of biocatalyst and electrode assembly.

Treatment of dye bearing wastewater through biological machinery is particularly challenging due to its recalcitrant and inhibitory nature. In this study, functional behavior and treatment efficiency of bio-electrochemical treatment (BET) system was evaluated with increasing azo dye concentrations (100, 200, 300 and 500mg dye/l). Maximum dye removal was observed at 300mg dye/l (75%) followed by 200mg dye/l (65%), 100mg dye/l (62%) and 500mg dye/l (58%). Concurrent increment in dye load resulted in enhanced azo reductase and dehydrogenase activities respectively (300mg dye/l: 39.6U; 4.96μg/ml). Derivatives of cyclic voltammograms also supported the involvement of various membrane bound redox shuttlers, viz., cytochrome-c, cytochrome-bc1 and flavoproteins during the electron transfer. Bacterial respiration during BET operation utilized various electron acceptors such as electrodes and dye intermediates with simultaneous bioelectricity generation. This study illustrates the synergistic interaction of biocatalyst with electrode assembly for efficient treatment of azo dye wastewater.

Reductive behaviour of acid azo dye based wastewater: Biocatalyst activity in conjunction with enzymatic and bio-electro catalytic evaluation

Present study illustrates the significance of biocatalysts reductive behaviour in the degradation of dye molecules using glucose as co-substrate. An anaerobic system was operated at a dye concentration of 50mg/l with an organic loading rate (OLR) of 1.36 kg COD/m(3)-day. Decolourization and COD removal efficiencies were observed to be 42% and 48% respectively. Azo reductase (18.9 U) and dehydrogenase enzyme (1.4 μg/ml) activities showed increment with operation time. Anaerobic microenvironment showed dye reduction converting them into aromatic amines. The presence of mediators viz., cytochromes, quinines and Fe-S proteins depicted in the cyclic voltammetry profiles played a crucial role in transfer of electrons for the reduction of dye molecules. Bio-electro kinetic profiles obtained through Tafel analysis showed persistent reduction behaviour, which is in good correlation with dye degradation in the anaerobic microenvironment.

A study on risk factors and clinical presentation of ectopic pregnancy

Objectives: The present study was designed to study the risk factors of ectopic pregnancy and their clinical presentation. Material and methods: It was a retrospective study with 100 cases of ec topi pregnancy conducted in the Department of Obstetrics and Gynec ology, ESIC MC PGIMSR, Rajajinagar, Banglore for a period of 2 years were included. Detailed history s uggestive of risk factors for ectopic pregnancy, me nstrual and obstetric history was taken. Results: A total of 7200 pregnancies were confirmed during the study period, of which 100 cases of ectopic pregnancies were diagnos ed, giving an incidence of 1.38%. Sixty three perce nt were in the age group of 21-30 years. Seventy six percen t of women were multigravidae. Forty eight percent of he patients had identifiable risk factors, of which pa st history of pelvic inflammatory disease in 28%, h istory of previous abortion in 16%, infertility in 10%, histo ry of previous ectopic pregnancy in 14%, history o f previous caesarian section in 18% and tubectomy in 14% were not d. Ninety six percent had amenorrhea, followed by pain abdomen in 88%, bleeding per vagina in 78%, fa inting and syncopal attack in 16% of the patients. Pallor in 56% of the cases, 10% presented with shock. Conclusion: The early diagnosis of an ectopic pregnancy is on e of the greatest challenges for a physician. It require s a high index of suspicion in case of clinical pre sentation of pain abdomen, bleeding per vagina with amenorrhoea. The importance of an early diagnosis lies in the f act that the patient can be offered a conservative line of m anagement which can definitely have a beneficial ef fect on her future fertility.