Microbiological hydrogen (H ) thresholds in anaerobic continuous-flow systems: Effects of system characteristics.

Hydrogen (H ) concentrations that were associated with microbiological respiratory processes (RPs) such as sulfate reduction and methanogenesis were quantified in continuous-flow systems (CFSs) (e.g., bioreactors, sediments).

Experimental data for physical characteristics, fiber compositions, and tensile properties of nonwoven wipes and toilet papers.

This article presents experimental data for physical characteristics, fiber compositions, and tensile properties of non-flushable wipes, flushable wipes, and toilet papers. Samples included 42 flushable wipes, 16 non-flushable wipes, and 11 toilet papers that were collected from around the world by considering product diversity in their retail regions (e.g.

Physical characteristics, fiber compositions, and tensile properties of nonwoven wipes and toilet papers in relevance to what is flushable.

Numerous products, such as moist wipes, are marketed worldwide as "flushable." Recent studies indicate that wipes cause operational problems (e.g.

Role of hydrogen (H) mass transfer in microbiological H-threshold studies.

Gas-to-liquid mass transfer of hydrogen (H) was investigated in a gas-liquid reactor with a continuous gas phase, a batch liquid phase, and liquid mixing regimes relevant to assessing kinetics of microbial H consumption. H transfer was quantified in real-time with a H microsensor for no mixing, moderate mixing [100 rotations per minute (rpm)], and rapid mixing (200 rpm). The experimental results were simulated by mathematical models to find best-fit values of volumetric mass transfer coefficients-ka-for H, which were 1.

Effect of turbulence on the disintegration rate of flushable consumer products.

A previously developed model for the physical disintegration of flushable consumer products is expanded by investigating the effects of turbulence on the rate of physical disintegration. Disintegration experiments were conducted with cardboard tampon applicators at 100, 150, and 200 rotations per minute, corresponding to Reynold's numbers of 25,900, 39,400, and 52,900, respectively, which were estimated by using computational fluid dynamics modeling. The experiments were simulated with the disintegration model to obtain best-fit values of the kinetic and distribution parameters.

Physical disintegration of toilet papers in wastewater systems: experimental analysis and mathematical modeling.

Physical disintegration of representative toilet papers was investigated in this study to assess their disintegration potential in sewer systems. Characterization of toilet papers from different parts of the world indicated two main categories as premium and average quality. Physical disintegration experiments were conducted with representative products from each category according to standard protocols with improvements.

Development of a mathematical model for physical disintegration of flushable consumer products in wastewater systems.

The processes that flushable solid products may undergo after discharge to wastewater systems are (1) physical disintegration of solids resulting from turbulence, (2) direct dissolution of water-soluble components, (3) hydrolysis of solids to form soluble components, and (4) biodegradation of soluble and insoluble components. We develop a mathematical model for physical disintegration of flushable solid consumer products and test it with two different flushable products--product A, which has 40% water soluble-content, and product B, which has no water-soluble components. We present our modeling analysis of experimental results, from which we computed disintegration rate constants and fractional distribution coefficients for the disintegration of larger solids.

A mathematical model for the kinetics of Methanobacterium bryantii M.o.H. considering hydrogen thresholds.

We develop a kinetic model that builds on the foundation of classic Monod kinetics, but incorporates new phenomena such as substrate thresholds and survival mode observed in experiments with the H2-oxidizing methanogen Methanobacterium bryantii M.o.H.

Thermodynamic and kinetic analysis of the H2 threshold for Methanobacterium bryantii M.o.H.

H2 thresholds, concentrations below which H2 consumption by a microbial group stops, have been associated with microbial respiratory processes such as dechlorination, denitrification, sulfate reduction, and methanogenesis. Researchers have proposed that observed H2 thresholds occur when the available Gibbs free energy is minimal (DeltaG approximately 0) for a specific respiratory reaction. Others suggest that microbial kinetics also may play a role in controlling the thresholds.

Kinetic characterization of Methanobacterium bryantii M.o.H.

H2 is a key electron donor for many anaerobic microorganisms; thus, keen competition for H2 occurs among H2-utilizing microbial groups. Monod kinetic parameters provide essential information for kinetic analysis of competition for H2. In this study, we estimated Monod kinetic parameter values for a methanogen that consumes only H2 as its electron donor, Methanobacterium bryantii M.