Plant Aeration Research Articles

Measurement of polysaccharides and proteins in biofilm extracellular polymers

The structure of biofilm extracellular polymers (ECPs) was studied by measuring their polysaccharide and protein spatial distributions along biofilm depth. Biofilm was collected from two aerobic heterotrophic biofilm reactors, which were seeded with Sphingomonas sp. and Sphingomonas sp. plus mixed liquor, respectively, and operated under toxic organic (in this case, azo dye) degrading conditions. Complete mixing conditions in the tworeactors were verified by measuring water content, and polysaccharide and protein quantities from three vertical sampling positions over time. Experimental results showed that: (1) the biofilm water content of either reactor did not change with sample position or biofilm age, with an average biofilm water content m both reactors of 97%; (2) polysaccharides and proteins in the ECPs did not change with sample position; (3) the profiles of polysaccharides and proteins along the biofilm depth showed a stratified biofilm structure, with their ratio (proteins/polysaccharides) being relatively stable over the depth. Oxygen and substrate transport and interactions among species were considered to be the main reasons for producing such a non-uniform biofilm structure; and (4) Sphingomonas sp. could not compete well with microorganisms derived from the mixed liquor of a wastewater treatment plant aeration basin.

Convective Gas Flow in Plant Aeration and Graham's Law of Diffusion

Experiments with porous ceramic membranes and leaves of Nymphaea alba L. are described which demonstrate that the counter diffusion of gaseous components of different molar mass governed by Graham’s law of diffusion (not to be confused with Graham’s law of effusion) has to be taken into account to understand the exchange processes of gases between leaves of aquatic and amphibic plants and the outer atmosphere. The experiments are carried out under conditions under which the ratio of the maximum pore size r of the ceramic material to the mean free path length λ. of the molecules in air has a value of the order of λ/r ≈ 1

Convective gas flow in plant aeration and thermo-osmosis: a model experiment

The stationary thermo-osmotic pressure difference ( Δ P) stat between a gaseous phase formed by air of constant volume and the outer atmosphere ( P ≈ 1 bar) across a porous cellulose nitrate membrane is measured as a function of the effective temperature difference ΔT across the membranes. In the stationary state (i.e. vanishing gas flow across the membrane) the pressure of the phase with the higher temperature is higher than that of the phase with the lower temperature. The effective radius of the pore structure of the membrane (0.14 μm < r eff < 1.27 μm) and thickness of the membranes (105 μm < δ m < 735 μ m) are parameters of the experiments. The ratio of the mean free path length of the molecules in the gaseous phase λ at atmospheric pressure and r eff has a value of about ( λ r eff ) ≈ 1 . The relation between ( Δ P) stat and ΔT are linear to a first approximation (e.g. r eff = 0.19 μm: ( Δ P) stat = AΔT, where A = 59.4 Pa K −1; 0 < ΔT < 10 K). The values of the molar heat of transport Q∗ m obtained from the slope of the ( Δ P) stat vs. ΔT curves for the different types of membranes are compared with theoretically calculated values. The agreement between the two data sets is satisfactory. It is concluded that at atmospheric pressure under the condition ( λ r eff ) = 1 , thermo-osmotically generated pressure differences can contribute significantly to the pressure difference needed as a driving force of the observed convective gas flow in plant aeration.

The effect of pore size on transfer capabilities, fouling tendencies, and cleaning of ceramic air diffusers

ABSTRACT: A study of the effect of fouling on the standard oxygen transfer efficiency (SOTE) of ceramic diffusers of four different pore sizes was conducted at the Monroe, Wis. wastewater treatment plant over a 2‐year period. Four pilot test headers were installed in the plant aeration tanks each containing four diffusers of one pore size. Only minor changes in SOTE, bubble release vacuum (BRV), and dynamic wet pressure (DWP) were observed indicating that the fouling phenomenon at Monroe was not progressive. The adverse effects of fouling with respect to back pressure and SOTE were found to be less than might have been predicted from the literature. The cleaning procedure used in the study, involving a combination of high pressure water spraying with liquid acid treatment, followed by additional spraying, resulted in nearly complete restoration of the diffusers' original characteristics.

Polarographic oxygen electrodes and their use in plant aeration studies

SynopsisThe electrolytic reduction of oxygen which occurs at a wetted ‘unattackable’ cathodic electrode of platinum or gold when polarised in conjunction with a Ag/AgCl anode, forms the basis of most polarographic oxygen measurements in plant biological work.Various types of polarographic electrode and their uses are reviewed. These include cylindrical sleeving electrodes for quantifying localised oxygen fluxes from intact roots, ‘bare’, membrane-coated, and Clark-type microelectrodes suitable for measuring concentrations and profiles both inside roots and in the rhizosphere, and macro-Clark electrodes most frequently used in respiratory studies.Some details concerning equipment and electrode construction are given and some pitfalls in electrode application are discussed.

Improvements to Activated‐Sludge Plant Aeration Systems at Hawick and Jedburgh Sewage‐Treatment Works

ABSTRACTIn response to the requirement of the Tweed River Purification Board for a higher standard of effluent, improvements have been carried out to the activated‐sludge aeration systems at Hawick and Jed‐burgh sewage‐treatment works.This paper describes the electrical and mechanical refurbishment involved, and the performance of the completed systems. Process control was considered to be of particular importance in these projects as the plant receives a high proportion of industrial effluent.

On the relative importance of convective and diffusive gas flows in plant aeration

summaryThe importance of through flow convection of gases is recognized hut the notion that convection of a non‐through flow type might play n major role in plant aeration is challenged. It is shown that this convection discovered recently in deep‐water rice, and which could operate also in almost any submerged root system, must be subordinate to diffusion in the plant's aeration process and will al best have only minimal influence on root aeration.

Oxygen demand and supply in Zizania latifolia and Phragmites australis

The oxygen demand of underground organs in tall emergent plants was assumed to be supplied with the oxygen flux through aerial shoots. Measurements were made of the respiratory activity of underground organs and oxygen flux through aerial shoots in Zizania latifolia (Griseb.) Stapf and Phragmites australis (Cav.) Trin. ex Steud. Oxygen uptake rates of Z. latifolia roots and rhizomes decreased as the supply of oxygen decreased. Phragmites australis, however, did not respond to decreases in the supply of oxygen until the oxygen supply was relatively low. The values for old rhizomes of P. australis were very low. Most of the oxygen flux for P. australis was derived from standing dead shoots. The important role of dead shoots of P. australis in plant aeration is suggested. The degree of sufficiency of oxygen supply for Z. latifolia was 179% in May and 92% in August. The values for P. australis were 45% both in May and August. Furthermore, estimation of mean oxygen concentration of inner underground organs for P. australis showed very low values, 1.6% both in May and August, even in shallow water.

Root Aeration and Respiration in Young Mangrove Plants (Avicennia marina(Forsk.) Vierh.)

Curran, M., Cole, M. and Allaway, W. G. 1986. Root aeration and respiration in young mangrove plants (Avicennia marina (Forsk.) Vierh.).—J. exp. Bot. 37: 1225-1233. The roots of young plants of Avicennia marina (Forsk.) Vierh. grown under simulated tidal conditions were harvested so as to obtain the entire root system. The roots were subdivided and weighed and subsamples taken for manometric determination of respiration rates at different temperatures. The supply capacity of the above-ground portion of the root system was determined and the results compared in terms of supply and demand. The oxygen consumption rate of the roots at 15 °C was found to be 1-69 + 007 ?tmol kg1 s1 for cable roots and 3-27 + 0-12 /rmol kg-1 s_1 for fine roots. The gio for respiration was 2-55 for oxygen consumption in both fine and cable roots, and for carbon dioxide production was 2-66 for fine roots and 04 for cable roots. The respiratory quotient varied with temperature but was less than unity. Concentration differences of between 1-8 mol m and 3-4 mol m 3 between the inside of root and the air were sufficient to permit aeration of the root system by diffusion alone, and the aerenchyma contained sufficient oxygen to maintain aerobic conditions while the roots were covered with water. The effect of tide and seasonal temperature change on gas exchange, together with the possibility of some form of carbon dioxide fixation within the root, are examined and the implications of these effects on growth and development are discussed.

Role of plant aeration in zonation of Zizania latifolia and Phragmites australis

The emergent plants Phragmites australis (Cav.) Trin. ex Steud and Zizania latifolia (Griseb.) Stapf. are distributed along a gradient of increasing water depth, with P. australis restricted to shallow water and Z. latifolia to deeper water. The lower limits of the two vegetational zones were discussed from the view-point of oxygen supply from aerial shoots. The oxygen influx to the underground organs from aerial shoots is proportional to the gradient between oxygen concentrations in atmosphere and inside the basal stem ( C). The proportional constant ( Q), called here the ventilation coefficient, expresses the efficiency of the diffusion of oxygen. An attempt was made to measure Q and C. The values of Q for the two species in their dominant niches are higher in Z. latifolia than in P. australis, corresponding to the natural distribution with increasing depths of water. Q in Z. latifolia and P. australis first increased and then decreased. Corresponding to such changes of Q, the oxygen concentration inside the basal stem ( C) fell to low values for Z. latifolia at the greatest water-depth. Since in Z. latifolia a low value of C in deeper waters was accompanied by a decline in standing crop of aerial shoots, it was concluded that oxygen is the limiting factor for the distribution of Z. latifolia in the deeper waters.

Oxygen Diffusion in the Soil‐Plant System V. Oxygen Concentration and Temperature Effects on Oxygen Relations Predicted for Maize Roots1

AbstractA model for steady state isothermal oxygen diffusion into a cylindrical root surrounded by a uniform water film, accounting for longitudinal oxygen flux through intercellular gas spaces, radial flux through the water film, and a concentration‐dependent respiratory oxygen sink, was used to assess effects of change in soil and root oxygen concentration and temperature on the oxygen relations of maize (Zea mays L.) roots.Increases in both root oxygen concentration at 5 cm from the tip and in soil oxygen concentration increased the root oxygen profile. Under conditions of high soil oxygen concentration and low root concentration oxygen diffused back along the root toward the shoot. Change in root oxygen concentration (0.05 to 0.15 ml/ml) at cm from the root tip had only a small effect on the oxygen concentration at the root tip, whereas an increase in soil oxygen concentration (0.05 to 0.15 ml/ml) increased the root tip oxygen concentration (0.02 to 0.07 ml/ml). Respiration rate of the root tip (1‐mm section) was closely dependent on soil oxygen supply and plant aeration had very little effect. Plant aeration contributed significantly to the respiration rate on a whole‐root basis. Mean root respiration rate increased with increase in soil and root oxygen concentration and also with increase in temperature. The root oxygen concentration profile decreased with rise in temperature associated with an increased respiratory oxygen demand. For mean respiration rate Q10 was less than 2 and decreased with increase in temperature.

Aerobic Treatment of Fruit Cannery Waste Water with Added Nitrogen

Increased land disposal costs and more stringent legislation implies more sophisticated treatment methods for food processing plant wastes. Fruit cannery wastes, characterized by high BOD values and very low N & P levels, present problems for biological oxidation systems.A pilot plant aeration system with sludge recirculation was used to determine the most suitable form of N for use as a nutrient supplement. It was possible, using a three compartment system, to achieve up to 99+ percent BOD removal with an average retention time of about 2.5 days. The final effluent was clear and was free of nitrate, nitrite and ammonia N. Use of a single aeration chamber with sludge recirculation (average retention time 30hours) gave up to 98+ percent BOD removal.Sodium nitrate at 56ppm added N was the only effective nitrogenous additive. Others tested (urea, ammonium phosphate, ammonium nitrate, sodium nitrite and ammonia) gave poor floe characteristics and much lower BOD removal.

Gas Space Porosity of Citrus Roots1

Abstract The vol of gas spaces per unit root vol (porosity) was measured for 4 citrus rootstock cultivars grown in sand culture for 100 days under greenhouse conditions. Rough lemon (Citrus jambhiri Lush.) had a porosity of 7.2% which was significantly less than sweet orange (Citrus sinensis L. Osbeck) at 10.9% and ‘Troyer’ citrange (Poncirus trifoliata L. Raf. × C. sinensis) at 9.4%. Trifoliate orange (P. trifoliata) had a mean porosity of 9.8% with more variability than the other cultivars. ‘Troyer’ citrange roots sampled from trees grown in solution culture had a porosity of 13.2% and this is significantly higher than for roots grown in sand culture. Characterization of root porosity is one important factor in assessing the significance of internal plant aeration.

Oxygen Diffusion in the Soil‐Plant System I. A Model1

AbstractA model for steady state, isothermal oxygen diffusion into a cylindrical root surrounded by a water film of uniform thickness is proposed. Equations are developed which account for longitudinal oxygen flux through the intercellular gas spaces, radial flux through the water film, and a respiratory oxygen sink which is defined as a function of oxygen concentration.A method of computer analysis is outlined whereby the law of continuity is applied sequentially to small sections of root, such that the amount of oxygen diffusing into a section is equated with the oxygen diffusing out plus the respiratory consumption. The solution for the model defines a series of oxygen concentrations along the root length. From these data the amount of oxygen consumed in respiration which diffuses into the top of the root (plant aeration) and the amount diffusing radially from the soil (soil aeration) may be calculated, and effects of soil and plant characteristics examined.

A microelectrode for measuring intracellular PO2.

A simple and reliable method of constructing an intracellular pH microelectrode is described. Antimony is used as the pH sensor. Antimony electrodes have been used in biological systems as early as 1927 (1). Since then several investigators have used different kinds of Sb electrodes. Roos and Boton (3) describe the latest methods of construction and application of pH sensitive micro-electrodes. In most cases the pH electrodes were fabricated by pulling glass capillaries filled with molten antimony and in a few cases by coating glass with antimony. The electrodes were of the open type.