Nitrogen removal in a two-stage, re-circulating waste stabilisation pond system.

Waste stabilisation ponds are used widely in Australia and other parts of the world for treating wastewater from domestic and a wide range of industrial sources. It remains a popular form of treatment for wastewater for many small rural towns. The development of a two-stage, re-circulating waste stabilisation pond incorporating algal-bacterial biofilm represents a new approach to increasing the functioning biomass within the water column to improve treatment efficiency. This new approach will be a more viable and economical option for most of the existing waste stabilisation ponds to achieve significant nitrogen removal than converting them to another form of biological nutrient removal processes. A laboratory-scale, two-stage, re-circulating system incorporating "Bio-Tube" plastic modules as attached growth medium has been tested using synthetic wastewater. It has been proven that nitrification-denitrification was the primary mechanism for nitrogen removal in such a system operated under complete mix conditions. During the experimental period, average removal efficiencies of 90-95% of ammonia nitrogen and 65-85% of total nitrogen removal were achieved with influent COD of 600 mg/L and total nitrogen of 70 mg/L.

Thermodilution right ventricular volume: a novel and better predictor of volume replacement in acute thermal injury.

Management of acutely burned patients requires intense but meticulous fluid therapy. Indicators of satisfactory resuscitation include: intravascular and arterial pressures and urine output. The usefulness of these parameters as a predictor of cardiac index (CI) has not been tested. Compared to central venous pressure, right ventricular end-diastolic volume (RVEDV) may give a closer approximation of the preload of the right ventricle. Modifying the pulmonary artery (PA) catheter and using the thermodilution technique we measured RVEDV and right ventricular ejection fraction (RVEF) as well as the classical parameters in 16 patients of mean age 39.3 years and of mean body surface area burn 75.2%. CI best correlated with RVEDV (r = 0.75). Mean PA pressure, wedge pressure, RV end-diastolic pressure, and urine output correlated poorly with CI (r = 0.36, 0.32, 0.27, and 0.26, respectively). Unlike atrial pressures the RVEDV and RVEF are unaffected by malpositioning of transducers, airway pressure, and compliance changes of the ventricle. The measurement of RVEDV is a useful clinical tool for the assessment of preload and when used in combination with RVEF may indicate the need for inotropy.