ABSTRACT
Mixing and transport phenomena affect the efficiency of all bioreactor configurations. An even mixing pattern at the macro-level is desirable to provide good conditions for substrate transport to, and from, the microbial aggregates. The state of segregation of particulate material in the reactor is also important. The production of biogas in anaerobic reactors is another factor that affects mixing intensity and hence the interactions between the liquid, solid and gaseous phases. The CSTR model with some degree of short-circuiting, dead zones and bypassing flows seems to describe the overall hydrodynamics of UASBs. However, few data are available in the literature for full-scale reactors that relate process performance to mixing characteristics. Dispersion studies using LiCl were done for four hydraulic loading rates on a full-scale UASB treating domestic wastewater in Ginebra, Valle del Cauca, southwest Colombia. COD, TSS, and Settleable Solids were used to evaluate the performance of organic matter removal. The UASB showed a complete mixing pattern for hydraulic loading rates close to the design value (i.e. Q = 10-13l s(-1) and HRT=8-6 h). Gross mixing distortions and localised stagnant zones, short-circuiting and bypass flows were found in the sludge bed and blanket zones for both extreme conditions (underloading and overloading). The liquid volume contained below the gas-liquid-solid separator was found to contribute to the overall stagnant volume, particularly when the reactor was underloaded. The removal of organic matter showed a log-linear correlation with the dispersion number.
Subject(s)
Bioreactors , Waste Disposal, Fluid/methods , Bacteria, Anaerobic , Gases , Organic Chemicals/metabolism , Water MovementsABSTRACT
Objective: to describe the surgical treatment of an anterior sacral meningocele (ASM). Description: a 67 year-old woman presented with pelvic mass symptoms, and had a previous history of four surgeries with mistaken diagnosis, consulted to the neurosurgery departament for pain treatment. MRI revealed a cystic sacral mass connected with the spinal subarachnoid space, with low density structures in the pedicle. MyeloCT showed no neural elements in the sac. Intervention: an anterior transabdominal approach with wall cyst dissection, excision of the sac and simple ligation of the neck was performed. Conclusion: we presented an uncommon case of ASM in an adult woman, with the transabdominal surgical approach was the treatment of choice in anterior sacral meningocele
Subject(s)
Humans , Adult , Female , Meningocele , Sacrum , Magnetic Resonance ImagingABSTRACT
Objective: to describe the surgical treatment of an anterior sacral meningocele (ASM). Description: a 67 year-old woman presented with pelvic mass symptoms, and had a previous history of four surgeries with mistaken diagnosis, consulted to the neurosurgery departament for pain treatment. MRI revealed a cystic sacral mass connected with the spinal subarachnoid space, with low density structures in the pedicle. MyeloCT showed no neural elements in the sac. Intervention: an anterior transabdominal approach with wall cyst dissection, excision of the sac and simple ligation of the neck was performed. Conclusion: we presented an uncommon case of ASM in an adult woman, with the transabdominal surgical approach was the treatment of choice in anterior sacral meningocele (AU)