A laboratory batch reactor test for assessing nonspeciated volatile organic compound biodegradation in activated sludge.

The relative rates of biodegradation and stripping and volatilization of nonspeciated volatile organic compounds (VOCs) in wastewater treated with aerobic activated-sludge processes can be quantified using a newly developed procedure. This method was adapted from the original aerated draft tube reactor test that was developed to measure biodegradation rate constants for specific volatile pollutants of interest. The original batch test has been modified to include solid-phase microextraction (SPME) fibers for sampling in the gas phase. The experimental procedure using SPME fibers does not require specific identification and quantitation of individual pollutants and can be used to evaluate wastewater with multiple VOCs. To illustrate use of this procedure, laboratory experiments were conducted using biomass and wastewater or effluent from three activated-sludge treatment systems. Each experiment consisted of two trials: a stripping-only trial without biomass and a stripping plus biodegradation trial using biomass from the activated-sludge unit of interest. Data from the two trials were used to quantify the rates of biodegradation by difference. The activated-sludge systems tested were a laboratory diffused-air reactor treating refinery wastewater, a full-scale surface aerated reactor treating a petrochemical wastewater, and a full-scale diffused-air reactor treating a variety of industrial effluents. The biodegradation rate constant data from each laboratory batch experiment were used in model calculations to quantify the fraction emitted (fe) and the fraction biodegraded (fbio) for each system. The fe values ranged from a maximum of 0.01 to a maximum of 0.32, whereas fbio values ranged from a minimum of 0.40 to a minimum 0.95. Two of these systems had been previously tested using a more complicated experimental approach, and the current results were in good agreement with previous results. These results indicate that biodegradation rate constant data from this laboratory method can be successfully used to predict the fate of VOCs in field-scale treatment units, and thus could potentially be used for demonstration of compliance with wastewater VOC emission regulations.

Computed tomographic and cytologic assessment of cystic pancreatic neoplasms: a difficult preoperative diagnosis.

The computed tomography (CT) findings or cytologic results, or both, for 21 patients with cystic pancreatic neoplasm (4 with microcystic cystadenoma, 6 with macrocystic mucinous cystadenoma, 10 with macrocystic mucinous cystadenocarcinoma and 1 with a papillary cystic neoplasm) were reviewed. CT scans for 14 of the patients were reviewed by two gastrointestinal radiologists who were blinded with respect to the patients' identities and the diagnoses. The radiologists used previously published criteria for distinguishing between microcystic and macrocystic neoplasms. Of the four cases of microcystic cystadenoma, two were correctly diagnosed by one radiologist, and one was correctly diagnosed by the other. Three and four cases respectively of five cases of macrocystic cystadenoma were correctly identified, as were three and five of five cases of macrocystic cystadenocarcinoma. Cytologic evaluation of samples from fine-needle aspiration biopsy had been performed for 15 of the patients, and these records were reviewed. One of three cases of microcystic cystadenoma, two of four cases of macrocystic cystadenoma, five of seven cases of macrocystic cystadenocarcinoma and the papillary cystic neoplasm were correctly diagnosed on the basis of the cytologic findings. The combination of CT and cytologic assessment is helpful in distinguishing different types of cystic pancreatic neoplasms, but there is significant overlap among the clinical and radiographic features of these lesions, and therefore operative assessment is often necessary.

Coexistence and the productivity of white clover-perennial ryegrass mixtures.

Yield comparisons between five white cloverperennial ryegrass mixtures, whose individual components had previously coexisted, and a corresponding set of ten mixtures based on components that had not coexisted disclosed a yield advantage to the former group of 8.5% over a 4-year period. All five clover populations produced their highest yields when associated with their coexisting grass. The coexisting mixtures also yielded more grass in spring, probably due to the exotic origin of the majority of the companion grasses, reinforced by the nitrogen transfer process between clover and grass. The relative proportions of clover attained by the five populations was apparently unaffected by grass companion. These results are briefly discussed in the context of improving the productivity of white clover-perennial ryegrass mixtures.

Effects of coexistence on the performance of white clover-perennial ryegrass mixtures.

Yields from five white clover/perennial ryegrass mixtures, each based on coexisting components, were compared with those produced by ten mixtures whose constituents had no previous history of coexistence. The former group consisted of five paired clover/ryegrass populations, four collected from natural pastures and one from a sown pasture, whilst the latter group comprised the same five clover populations grown in turn with each of two ryegrass companions.In the first harvest year, when artificial fertilizer plus soil mineralization supplied most of the nitrogen to this experiment, the grasses were generally favoured at the expense of the clovers. Although those mixtures based on coexisting populations had significantly lower yields the clover within these mixtures made a significantly higher contribution to their productivity. This advantage was retained into the second harvest year when it was accompanied by a correlated response in the grasses, which by then may have become dependent upon the clover for their nitrogen supply. Consequently, by the end of the second harvest year those mixtures based on coexisting populations yielded over 20% more on average, due mainly to improved early season growth. Despite considerable differences in productivity, all five clover populations gave their highest yields when grown with their matching grass.