This study demonstrated that temperature is an important factor in determining the outcome of competition between polyphosphate-accumulating organisms (PAOs) and glycogen-accumulating non-poly-P organisms (GAOs) and the resultant stability of enhanced biological phosphorus removal (EBPR) systems. At 20 degrees C and a 10-day sludge age, PAOs were dominant in the anaerobic/aerobic (A/O) SBR, however, at 30 degrees C and a 10-day sludge age, GAOs were dominant in the A/O SBR. For kinetic batch studies, the anaerobic specific acetate uptake rate of GAO-dominated sludge (1.34 x 10(-3) mg C/mg VSS x minute) was higher than the rate of PAO-dominated sludge (0.89 x 10(-3) mg C/mg VSS x minute) at 30 degrees C, leading to the eventual failure of EBPR processes at high temperatures.

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Laboratory-scale batch experiments (semicontinuously fed) were conducted using a two-level factorial experimental design to investigate principal factors and interactions affecting microbiologically influenced corrosion (MIC) of carbon (C) steel. Factors considered included the C source as chemical oxygen demand (COD), sulfate (SO 4 2-) concentration, calcium carbonate (CaCO 3 ) precipitation, and bacteria inoculation at 20°C. Yates' algorithm was applied to calculate main and interaction effects, and an empirical model indicating major trends was obtained. Experimental results showed CaCO 3 precipitation played a significant role in influencing the biocorrosion tendency of steel. In the supersaturated condition, SO 4 2concentration and bacterial inoculation had no appreciable effects on corrosion. In the undersaturated condition, the corrosion rate was affected significantly by SO 4 2concentration and bacterial inoculation. The effect of each factor on corrosion rate was explored.

Hydrodynamic surveys were conducted in a partially stratified estuary. Longitudinal salt fluxes through a cross-section were measured and the optimal number of lateral and 'vertical points for observation and estimation of fluxes ofpollutants found. The hydrodynamic data were decomposed to investigate the mechanism of instantaneous and tidally averaged mass fluxes.The decomposition method developed showed that instantaneous salt flux arose principally from the combination of velocity fluctuation with the tidal mean salinity. The error analysis showed that the estimate of mass flux was sensitive to the error inherent in the velocity data and the error range was within + 10% of the total flux. Seven. depth and four width points gave acceptable estimates of the water flux, salt flux, and longitudinal dispersion.An important feature of estuarine flow systems is the great spatial and temporal (seasonal, semidiurnal, and diurnal) variation resulting from interaction between tidal oscillation and freshwater flow. Having field observations be representative in an estuary is thus highly dependent on the sampling design (sampling locations, sampling rate, and sampling durations) as well as a rational procedure of data analysis and synthesis (Kjerfve 1979). Cross-sectional variations in velocity and pollutant (dissolved or suspended) concentrations may have a significant effect on longitudinal mass flux. One must decide how many lateral and vertical measuring positions are required to estimate longitudinal mass fluxes through a cross-section within an acceptable error. The standard sampling rate is typically once every hour, but only a few studies have been conducted with sufficient spatial resolution to estimate longitudinal mass fluxes precisely.Velocity and concentration values have been decomposed to investigate the relative importance of transverse and vertical variations (e.g. Hansen 1965; Fischer 1972;Smith 1980;Lewis and Lewis 1983). These AcknowledgmentsWe thank R. E. Lewis for advice during this research and K. R. Dyer for supplying the data for Southampton Water.

SYNOPSISThe permeation parameters, partition coefficient and diffusion coefficient, were obtained for polybutylene (PB) with toluene using a gravimetric method. A PB sample was repeatedly exposed and desorbed, and the partition coefficient and diffusion coefficient were measured. Permeation parameters were also measured at different temperatures. The results were compared with those obtained from a 12-year-old PB pipe sample, which had experienced structural failure. Tests at an elevated temperature of 45°C failed to simulate the effect of polymer aging, whereas repeated sorption/desorption tests produced permeation parameters compatible with those of a 12-year-old PB pipe in service. I NTRODU CTlO NThe major thermoplastic materials used for potable water transport and plumbing applications include poly ( vinyl chloride) ( PVC ) , chlorinated poly ( vinyl chloride) (CPVC) , polyethylene ( P E ) , polybutylene ( PB ) , and acrylonitrile-butadiene-styrene ( ABS ) .Advantages claimed for plastic pipes include immunity to corrosion, ease of use, ductility, and durability. During the last decade, however, it has been found that plastic piping and gasket materials are susceptible to attack and/or permeation by certain organic chemicals.'s2Polymers are permeated by organic chemicals through a combination of partitioning (solubility) and diffusion phenomena. Prediction of a partition coefficient and diffusion coefficient has been attempted by other ~esearchers.~'~ For aromatic organic chemicals, the vapor-phase partition coefficient was predicted from a logarithmic correlation with the saturation vapor concentration for PB and styrene butadiene rubber (SBR) .' Also, the diffusion coefficient was estimated from the relationship between the molecular diameter and the logarithm of the diffusion coefficient for PVC, PB, and SBR.' During service, polymers may change their physical properties including strength, stiffness, strain at failure, and permeability. Attempts have been made to evaluate the changes of original properties over a long period of time. One method adopted by EPA is to raise the temperature to 5OoC to test chemical ~ompatibilities.~ It is not clear whether a test at an elevated temperature can produce permeation parameters comparable to those of samples exposed to organic chemicals for a long time. A technique should be developed to assess the effects the aging of a polymer has on its permeability. In other words, how does the performance of a polymer change when it is exposed to organic chemicals for a long service time.The objective of this paper is to evaluate permeability of PB to toluene after long-term use. The results from 12-year-old specimens, repeated sorption-desorption tests, and various temperature conditions are compared. MATERIALS AND METHODS MaterialsPB, trade name for poly ( 1-butene) , is a member of the polyolefin group of polymers made of straightchain hydrocarbons. PB is partially crystalline and 2989