Fate and levels of steroid oestrogens and androgens in waste stabilisation ponds: quantification by liquid chromatography-tandem mass spectrometry.

The capacity for removing wastewater-borne endocrine disrupting chemicals (EDCs) was investigated for two wastewater treatment plants (WWTPs) incorporating waste stabilisation ponds (WSPs) as the principal treatment technology. Samples were analysed for a number of steroidal oestrogens and androgens using liquid chromatography-tandem mass spectrometry (LC/MS/MS). Removal efficiency for steroid androgens was high for both WWTPs (93-100%) but WSP treatment was observed to be less effective for removing steroid oestrogens, particularly oestriol.

Nitrification potential in waste stabilisation ponds: comparison of a secondary and tertiary pond system.

This study compared the nitrification potential of two separate Waste Stabilisation Ponds (WSPs) operating under differing physical and chemical conditions. In order to probe the nitrification potential of each system, the oxidation of ammonium and also the intermediate product nitrite was assessed using both in situ and laboratory micro-scale incubations. The role of sediment in determining the nitrification potential of the two WSPs was also investigated. Results from laboratory microcosm incubations revealed a competent and strikingly similar nitrification potential for both WSPs in spite of their differing nitrogen and organic loadings, and also suggested a significant role for sediment in WSP nitrogen cycling. Results from in situ field experiments identified biomass uptake to be the dominant nitrogen removal mechanism in natural pond environments. Other aspects of WSP nitrogen cycling are also discussed.

Application of high rate nitrifying trickling filters to remove low concentrations of ammonia from reclaimed municipal wastewater.

The interference of ammonia with the chlorination process is a problem for many reclaimed water treatment plant operators. This paper presents the findings from a series of pilot experiments that investigated the efficacy of high flow rate nitrifying trickling filters (NTFs) for the removal of low concentrations of ammonia (0.5-3.0 mg N L(-1)) from reclaimed wastewater. Results showed that nitrification was impeded by a combination of high organic carbon loads and aquatic snails, which consumed much of the active biomass. With adequate snail control, nitrification rates (0.3-1.1 g NH(4)-N m(-2) d(-1)) equivalent to that of traditional wastewater NTFs were achieved, despite operating under comparably low ammonia feed concentrations and high hydraulic flow rates.

Relative performance of duckweed ponds and rock filtration as advanced in-pond wastewater treatment processes for upgrading waste stabilisation pond effluent: a pilot study.

An experimental pilot plant was operated over a five month period to assess the relative treatment performances of: a duckweed (DW) pond; a rock filter (RF); and an open pond (OP); for the upgrading of final WSP effluent prior to reuse applications. Each pilot treatment system consisted of three identical ponds arranged in three parallel series, each fed a continuous flow of wastewater from the local Bolivar treatment plant. Light penetration profiling for the DW and OP systems revealed some 55% greater light attenuation capacity for DW ponds compared to the OP system. Results showed a significantly elevated performance capacity for the RF treatment with respect to BOD5, SS, turbidity and NH4-N removal, but equal treatment performances for algal (chlorophyll) removal. No significant performance differences were evident between the DW and OP treatments for any of the monitored parameters. Soluble reactive phosphorus, faecal coliform and E. coli removals were similar for all pilot treatment systems. Rock filters not only demonstrated an enhanced performance capacity in terms of removal of loaded parameters, but also showed greater reliability of performance and produced a consistently higher quality final effluent. Rock filters demonstrated greater potential over both DW and OP systems for the upgrading of WSP effluent prior to reuse application.

Femoral head activity in Perthes' disease: clinical evaluation of a quantitative technique for estimating tracer uptake.

A method for quantifying the uptake of Tc-99m-labeled phosphate complexes in the femoral head has been clinically evaluated, being used specifically for studying the uptake of these bone-seeking agents in Perthes' disease. The analysis depends on the selection, by computer program, of a reliable reference area in the femoral shaft, which is then compared with the mean uptake from each femoral head. The femoral-head activity is then represented as an uptake ratio. These ratios, together with a fixed contour representing the uptake in the femoral-head regions, provide more clinical information than the radiograph or scintiphoto, particularly in the early stages of unilateral or bilateral femoral-head disease and during followup. No correlation has been found between these ratios and qualitative techniques for assessing Perthes' disease by radiograph. From the quantitative data so far obtained it is clear that osteotomy reduces the vascularity of the femoral head, and in certain cases this reduction persists for some years. Tc-99m-labeled diphosphonate compounds were used in more recent studies, and a significant increase in sensitivity was obtained, compared with earlier polyphosphate data.

A comparison between monodisperse Tc-99m-labeled aerosol particles and Kr-81m for the assessment of lung function.

A quantitative method for study of the penetration and clearance of inhaled particles (5-micron Tc-99m-labeled polystyrene) in the human lung is described and compared with a Kr-81m technique for ventilation imaging. Volunteer healthy subjects and patients with chronic obstructive airway disease (COAD) were studied. Following inhalation of radioaerosol, data were recorded by a gamma-camera/computer system over a period of 6 hr. An aerosol penetration index (API) measures the proportion of aerosol reaching the peripheral region of the lung relative to that deposited in the larger central airways. A significant difference in the mean values of API for both groups was observed. Aerosol clearance rates from the whole lung and from central, intermediate and peripheral compartments of each lung field were studied. The healthy group showed a total clearance rate consistent with data from earlier work; the patients with COAD showed no clearance over the same period. Some healthy subjects were smokers, and differences in their penetration and clearance rates were evident, in spite of normal results from their conventional pulmonary function tests and Kr-81m ventilation studies. The aerosol technique, if carefully controlled, can be a more sensitive index for early lung abnormality than Kr-81m ventilation imaging.

A quantitative assessment of femoral head activity using 99Tcm -polyphosphate and a computer data collection system.

Abnormal femoral head activity in Legg-Calve-Perthes' disease has been measured using 99Tcm -polyphosphate and a gamma camera/computer data collection system. A reference point on the data matrix, which is unaffected by the diease, is used for deriving comparative uptake ratios in each femoral head. The reference point remains unaltered after surgical procedures or short intervals between follow-up studies. Early abnormality can be measured in both unilateral and bilateral femoral head pathology.

Which gamma camera?

Performance data on seven currently available gamma cameras have been presented. Where appropriate, results from both the DHSS and NEMA are included. It should be emphasized that no 'best buy' exists for all types of nuclear medicine application and that the performance figures presented in this paper must be interpreted in the light of clinical priorities. No mention has been made of optional extras for a camera system, long-term system reliability, availability of efficient servicing and last but not least, cost. Such details will no doubt be considered as important as the basic performance of the camera. Finally, continued improvements in gamma camera design and performance are likely to necessitate a further communication in the not too distant future.

A reappraisal of current methods for the assessment of planar gamma camera performance.

This study reappraises the acquisition parameters defined by three current protocols for the specification of planar gamma camera performance. These are the manufacturer Standards of the National Electrical Manufacturers' Association [1] and the International Electrotechnical Commission [2], and the user-orientated protocol of the UK Department of Health (DoH, formerly DHSS) Gamma Camera Performance Assessment Group [3]. The study looks specifically at three major planar performance characteristics: intrinsic non-uniformity, intrinsic spatial resolution and intrinsic non-linearity (spatial distortion). Acquisition parameters specified for these characteristics are investigated by testing a range of values for each parameter around those figures currently advocated by the three protocols. Those acquisition parameters which may be relaxed without loss of data integrity are identified and the adoption of revised parameters for some measurements within the DoH assessment protocol is suggested. Reviewing the data obtained, observations are made regarding the accuracy of some tests performed regularly for quality control purposes. The feasibility and advantages of incorporating some suitably modified DoH performance assessment tests within a routine quality assurance protocol for the gamma camera are also discussed.

Stomach outline visualization in gastrointestinal transit studies using scintigraphy.

A major disadvantage of gamma scintigraphy in gastrointestinal transit studies is the inability to provide adequate delineation of anatomical details. As an aid to the important requirement of outlining the stomach to ensure accurate quantification of the time at which material empties from this organ, a new technique is described, using short half-life 81mKr gas to provide clearer identification of the stomach outline and position.

Contribution of individual differences in gastric emptying to variability in plasma propranolol concentrations.

1 No correlation was found between the rate of gastric emptying and peak plasma propranolol concentrations in six hypertensive patients after single oral doses of 80 mg. 2 In four normal subjects given oral propranolol the peak plasma concentration was highest when a simultaneous injection of metoclopramide and lowest when propantheline was given. The mean time to peak was 1.5 h after metoclopramide, 2.8 h after normal saline and 4.5 h after propantheline. 3 Gastric emptying has some influence on the time of peak plasma propranolol concentrations but individual variation in its bioavailability is determined mainly by first-pass metabolism in the liver.