Initial experience with intraoperative testing and repair of colorectal anastomosis using a TAMIS approach after a positive leak test.

Anastomotic leak is one of the most feared complications of colorectal anastomosis. Different techniques have been described for intraoperative testing of anastomotic integrity. These include air insufflation, methylene blue and endoscopic visualisation. If an anastomotic leak is identified intraoperatively, there are various management options. Redo anastomosis is a possibility, but may be difficult in some cases. Defunctioning is another option, but there is an associated morbidity and signficant detrimental effect on quality of life. Direct transanal repair is only possible when a low anastomosis has been performed. When the anastomotic leak occurs high in the rectum or a partial mesorectal excision is performed a transanal approach is technically very challenging. We present our experience with transanal minimally invasive surgery (TAMIS) approach for anastomotic assessment and repair in four patients. In all cases, a colorectal anastomosis was performed and the air insufflation test was positive. We assessed the anastomosis with TAMIS. In three cases, a defect was found and subsequently sutured. In one case, a scar in the rectal mucosa was found and reinforced with a suture. A protective ileostomy was performed in two cases, while in the other two cases, no stoma was added. All four patients were discharged with no further complications. Both protective ileostomies were taken down after radiological and endoscopic confirmation of anastomotic integrity and all 4 anastomoses remain intact after follow-up. TAMIS intraoperative assessment and repair of anastomotic leak is a safe and feasible technique whcih may avoid the need for a defunctioning stoma.

Analysis of MSW full-scale facilities based on anaerobic digestion and/or composting using respiration indices as performance indicators.

The Landfill Directive (1999/31/EC) forces European States to reduce the amount of biodegradable municipal waste landfilled to 35% of 1995 levels. Mechanical-Biological Treatment (MBT) plants are the main alternative to waste incineration and landfilling. In this work, the waste treatment efficiency of six full-scale MBT facilities has been analysed using respiration indices (Dynamic Respiration Index and Cumulative Oxygen Consumption) to monitor plant performance. MBTs relying on anaerobic digestion plus composting achieved a high grade of stability on final compost (0.24±0.09mgO2g-1DMh-1 and 20±9mgO2g-1DM for dynamic respiration and cumulative consumption, respectively). On the contrary, MBTs relying only on composting showed a poor performance (1.3±0.2mgO2g-1DMh-1 and 104±18mgO2g-1DM for dynamic respiration and cumulative consumption, respectively). These results highlight the usefulness of respirometric balances to assess the performance of MBT full-scale plants.

A comparative study based on physical characteristics of suitable packing materials in biofiltration.

In the present work, 10 packing materials commonly used as support media in biofiltration are analysed and compared to evaluate their suitability according to physical characteristics. The nature of the packing material in biofilters is an important factor for the success in their construction and operation. Different packing materials have been used in biofiltration without a global agreement about which ones are the most adequate for biofiltration success. The materials studied were chosen according to previous works in the field of biofiltration including both organic and inorganic (or synthetic) materials. A set of nine different parameters were selected to cope with well-established factors, such as a material-specific surface area, pressure drop, nutrient supply, water retentivity, sorption capacity, and purchase cost. One ranking of packing materials was established for each parameter studied in order to define a relative suitability degree. Since biofiltration success generally depends on a combination of the ranked parameters, a procedure was defined to compare packing materials suitability under common situations in biofiltration. The selected scenarios, such as biofiltration of intermittent loads of pollutants and biofiltration of waste gases with low relative humidity, were investigated. The results indicate that, out of the packing materials studied, activated carbons were ranked top of several parameter rankings and were shown to be a significantly better packing material when parameters were combined to assess such selected scenarios.

Effect of different operational parameters in the enhanced biological phosphorus removal process. Experimental design and results.

The uncontrolled dumping of phosphorus into a water environment creates serious problems of eutrophication, affecting water quality and causing grave problems in the aquatic ecosystem. European legislation demands drastic reduction of phosphorus dissolved in wastewater. Enhanced Biological Phosphorus Removal (EBPR) is the current tendency in wastewater treatment. This biological process depends on a multiplicity of variables, but its three main factors are: influent COD/P ratio, anaerobic fraction and sludge retention time (SRT). The aim of this work is to statistically determine the effect of these three parameters in EBPR through a response surface methodology. The objective function that has been chosen is phosphorus removed per unit biomass formed. This function provides ample information on BPR, since the quantity of phosphorus removed depends on the accumulative capacity of the microorganisms present. Two levels were chosen for the SRT (5 and 10 days), two for the anaerobic fraction (0.1 and 0.2), and six for levels of the influent COD/P ratio (between 16 and 87). The experiments were undertaken at pilot scale (100 litres) with an A2/O configuration, with simultaneous nitrogen and phosphorous removaL The wastewater used is a synthetic mixture of complex sources of carbon and nitrogenwithout volatile fatty acids. The empirical model obtained indicates that the factor most influencing the EBPR process is the influent COD/P ratio, whilst the anaerobic fraction is that which has least influence. Additionally, there is an optimum in the influent COD/P ratio that is to be found between 41 and 48.