Dynamic analysis and optimal feedback control synthesis applied to biological waste treatment

The dynamics and optimal feedback control of biological waste treatment processes are examined. Modern feedback control theory is applied and results are obtained for both proportional and proportional plus integral control. A dynamic mathematical model of the system is developed by employing a Monod kinetic model, which is modified to account for endogenous metabolism, and a complete mixing flow model in the growth chamber. The feedback control is implemented via the flow rate so as to maintain desired effluent concentrations. External disturbances which cause changes in substrate concentration and/or cell concentration are considered and optimal control effort is applied. Results are also presented for impulse and step changes in the influent substrate concentration. It is found that by changing the values of the weighting factors in the objective function, it is possible to obtain good control of either the effluent substrate concentration or cell concentration.     

Treatment capability of a physical—Chemical package plant

A short-term study of a commercially-available physical—chemical waste treatment plant is reported. Results indicate that an excellent quality of effluent can be consistently obtained despite wide fluctuations of influent wastewater characteristics. Physical, chemical, and biological parameters were monitored. The short-term data obtained offer some evidence of superior treatment efficiency in terms of COD, color, turbidity, and phosphorus removals when compared to more conventional treatment methods.     

Toxicity bioassay of heavy metals in water using Tetrahymena pyriformis

The toxicities of five heavy metal compounds on the survival of the ciliated protozoan Tetrahymena pyriformis were determined. Three-day old cultured cells were exposed to five concentrations of each test compound in one or more of three water series; distilled, soft, and hard water. A culture of each sample was placed in a plastic petri dish and covered with mineral oil to prevent evaporation. The cells were counted initially, then again at 0·5 h, 1 h, 2 h, 1 day, 2 days, 3 days, and on the fourth day. Lethal threshold concentrations and tolerance limit medians were determined by graphic methods. On a weight bases cadmium was most toxic, followed in decreasing toxicity by mercury, cobalt, zinc, and lead. Compared to similar fish data, all heavy metals were more toxic to T. pyriformis except lead. The toxicity of lead in soft versus hard water exemplified an antagonistic effect with greater than seven times the amount of lead necessary in hard water to produce comparable mortality as lead in soft water. On the other hand, the toxicity of mercury is about twice as great in hard water as in soft water (a synergistic effect). T. pyriformis appears to be a more sensitive indicator than fish of heavy metal contamination of water. T. pyriformis bioassay should prove a good means of determining the existence of many water pollutants.     

The uptake of heavy metals by epiphytic bacteria on Alisma plantago-aquatica

Bacterial epiphytes on the surface of the fresh-water plant Alisma plantago-aquatica collected from a polluted river were found to be a major factor in contributing to the total metal concentrations of the plant. The removal of epiphytes from the leaf surface resulted in significant reductions in the concentrations of Cr (reduced by 15–50%), Cu (30–35%), Fe, Pb, and Zn (10–50%). While numbers of epiphytes and concentrations of heavy metals increased in samples collected from polluted water compared with from unpolluted water, the fraction of metals held by the epiphytes appeared to remain similar for all samples.     

Classic and novel brominated flame retardants (BFRs) in common sole (Solea solea L.) from main nursery zones along the French coasts

Brominated flame retardants (BFRs) were investigated in juvenile common sole from nursery zones situated along the French coast in 2007, 2008 and 2009. Extensive identification was performed with regard to PBDEs, novel BFRs 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) and decabromodiphenylethane (DBDPE), and other non-PBDE BFRs, namely, hexabromobenzene (HBB) and 2,2′,4,4′,5,5′-hexabromobiphenyl (BB-153). Polybrominated diphenyl ether (PBDE) concentrations (Σ 14 congeners) ranged from 0.01 ng/g to 0.16 ng/g wet weight (ww) in muscle, and 0.07 ng/g to 2.8 ng/g ww in liver. Concentrations were in the lower range of those reported in the literature in other European locations. Lower PBDE concentrations, condition indices and lipid contents were observed in the Seine estuary in 2009, possibly in relation to a lower water flow. The PBDE patterns and ratios we observed suggested that juvenile sole have a relative high metabolic degradation capacity. Non-PBDE BFRs were detected at lower levels than PBDEs, i.e., within the < method detection limit - 0.005 ng/g ww range in muscle, and < method detection limit - 0.2 ng/g ww range in liver. The data obtained is of particular interest for the future monitoring of these compounds in the environment.     

Orientation of smoke production in polyacrylonitrile

The introduction of ionic additives, such as KCN, or acidic comonomer units, such as methacrylic acid, which change the nature of the mechanism of nitrile oligomerization reaction from radical to ionic and cause its initiation at lower temperature, allows the level of obscurity and the total amount of smoke production, both in smouldering and flaming conditions to be decreased. An opposite result is obtained if diphenylpicrylhydrayl (DPPH) radicals in polyacrylonitrile is introduced; DPPH retards the initiation of the radical nitrile oligomerization reaction. The acrylonitrile-methacrylic acid copolymers have a limiting oxygen index, which increases with the methacrylic acid content. Owing to the increased amount of NH₃ produced during pyrolysis, the copolymers have a swelling behavior during the combustion test.     

Coagulation dynamics of fractal flocs induced by enmeshment and electrostatic patch mechanisms

The size and structure of flocs during floc formation were monitored for various coagulation mechanisms. Two distinctive mechanisms, namely, enmeshment and electrostatic patch, govern the dynamics of kaolin particles coagulation by polyaluminum chloride (PACl). They were investigated by small angle static light scattering (SASLS) and solid-state ²⁷Al NMR. In addition, a novel wet SEM (WSEM) was used in-situ to image the morphology of the aggregate in aqueous solution. Synthetic suspended particles were coagulated by two PACl products, a commercial product (PACl) and one laboratory product (PACl-E). The PACl-E contained more than 60% Al₁₃ while the PACl contained only 7% Al₁₃, with large percentage of colloidal Al. For coagulation by PACl at neutral pH and high dosage where the strong repulsion between particles occurs, the enmeshment ruled by reaction-limited aggregation (RLA) results in larger sweep flocs as well as higher fractal dimensional structure. For coagulation by PACl-E at alkaline pH and low dosage, the flocs were coagulated predominately by electrostatic patch with Al₁₃ aggregates. At such condition, it is likely that diffusion-limited aggregation (DLA) predominately rule PACl-E coagulation. The fractal dimension (D_s) values of PACl and PACl-E flocs formed at enmeshment and electrostatic patch increased with dosage, respectively. When breakage of flocs occurs, the breakage rate of PACl-E flocs is slower than that of sweep flocs. By WSEM imaging, the adsorption of spherical Al precipitates onto the particles was observed to form sweep flocs with a rough and ragged contour, while the PACl-E flocs were formed with a smooth and glossy structure.     

Free vibration of a clamped-free circular cylindrical shell partially filled with liquid—Part I: Theoretical analysis

Theoretical analyses are presented for the linear free vibration of a clamped-free cylindrical shell partially filled with an incompressible, inviscid liquid. For the vibration of the shell itself, the dynamic version of the Donnell equations was used and the problem was solved with the modified Galerkin procedure, taking the effect of the axisymmetric deformation due to the static liquid pressure into consideration. Concerning the vibration relevant to the liquid motion, the solution for the velocity potential was assumed as a sum of two sets of linear combinations of the suitable harmonic function, the unknown parameters of which were imposed to satisfy both boundary conditions along the wetted shell wall and the free liquid surface in a sense of appropriate series expansions. The procedure stated in the foregoing leads to a determinantal equation for the determination of the natural frequencies of the present shell-liquid system. To compare with the experimental results which will be stated in a companion paper,¹⁴ detailed numerical results will be presented in another companion paper¹³ on the free vibration characteristics of the two test cylinders partially filled with water.     

Levels of copper in the urine of women from nonpolluted farming regions of Japan.

Nearly 1500 spot urine samples were collected in the winter of 1987-1988 from women of seven farming prefectures located throughout Japan. Samples were analyzed for copper by flameless atomic absorption spectrometry. The copper content of the urine samples (Cu-U) distributed log-normally with a geometric mean (geometric standard deviation) of 36.9 (1.47) micrograms/l after adjustment for the specific gravity of urine of 1.016. The 95% confidence range was 17.1-79.7 micrograms/l. Neither alcohol consumption nor smoking habit affected the Cu-U. A literature survey showed that the observed level appears to be somewhat higher than previously reported values.     

Interaction effects of multiple pool fires

What are the effects of flame behavior of a number of fires burning in close proximity to one another? The results of measurements of burning rates, heat feedback, flame height, and flame trailing are reported for fires involving liquid pools.