Pharmacokinetic model for the successive demethylation and biliary secretion of methyl orange in the rat.

1. A one-compartment pharmacokinetic model was developed in which a drug underwent two successive metabolical reactions (for example, metabolism followed by conjugation) and free drug and both metabolites were excreted.2. Techniques were described whereby graphical estimates of the first-order rate constants may be derived from cumulative excretion data on the drug and its metabolites. Computer simulation techniques were used to show that the experimental data permit reasonably accurate estimation of the rate constants of the model by graphical and computer methods.3. Tritiated methyl orange (2 mg) was administered to five groups of six rats with biliary cannulation. The bile produced by each animal was collected at hourly intervals for 6 h and the amounts of methyl orange and its metabolites, 4'sulpho-4-methylaminoazobenzene and 4'sulpho-4-aminoazobenzene, determined by thin layer chromatography and radioactive counting techniques.4. The data were analysed graphically and with an iterative digital computer programme to yield the first-order rate constants for the successive demethylation steps in the metabolism of methyl orange. The removal of the first methyl group had a rate constant of 0.684+/-0.142 h(-1) (+/-S.D.) and the second methyl group 1.00+/-0.302 h(-1). The rate constant for biliary excretion of the free methyl orange was 0.164+/-0.042 h(-1), for the monomethyl derivative 0.672+/-0.461 h(-1), and for the demethylated metabolite 6.413+/-3.222 h(-1).

A survey of filamentous organisms at the Deer Island treatment plant.

The Deer Island Treatment Plant (DITP) treating both domestic and industrial wastewater, has a peak flow capacity of up to 1270 million gallons per day (MGD) (3342 m3 min(-1). The DITP contains a Pilot Plant, which consists of two identical pure oxygen activated sludge treatment trains, each with a maximum capacity of 1 MGD (2.63 m3 min(-1)) to simulate the maximum flow of the full size facility. This study documents the community of filamentous organisms living in the activatedsludge under various operational conditions in the Pilot Plant. Sixteen types of filamentous organisms were identified. The major filamentous organisms present in the Pilot Plant were Type 1701, Type 0041, Sphaerotilus natans, Microthrix parvicella, and Nocardia sp. Nocardia sp. was quite dominant in the early stages of the experimental period during high ambient temperatures (summer), indicating that temperature is one determining factor in the distribution of Nocardia sp. Thiothrix sp. was very sensitive to the dissolved oxygen (DO) level, with low DO values favoring the growth of the organisms. Microbiological observations made during the start-up and stable operation of the full-scale secondary treatment plant (maximum capacity 780 MGD) are also reported. No dominant filamentous species existed during the start-up period. Type 0803 and Type 1701, indicators of low oxygen level for the applied food to microorganism ratio, confirmed the low DO conditions of activated sludge tanks.