Foam Accumulation Research Articles

The carbohydrates of Phaeocystis and their degradation in the microbial food web

The ubiquity and high productivity associated with blooms of colonial Phaeocystis makes it an important contributor to the global carbon cycle. During blooms organic matter that is rich in carbohydrates is produced. We distinguish five different pools of carbohydrates produced by Phaeocystis. Like all plants and algal cells, both solitary and colonial cells produce (1) structural carbohydrates, (hetero) polysaccharides that are mainly part of the cell wall, (2) mono- and oligosaccharides, which are present as intermediates in the synthesis and catabolism of cell components, and (3) intracellular storage glucan. Colonial cells of Phaeocystis excrete (4) mucopolysaccharides, heteropolysaccharides that are the main constituent of the mucous colony matrix and (5) dissolved organic matter (DOM) rich in carbohydrates, which is mainly excreted by colonial cells. In this review the characteristics of these pools are discussed and quantitative data are summarized. During the exponential growth phase, the ratio of carbohydrate-carbon (C) to particulate organic carbon (POC) is approximately 0.1. When nutrients are limited, Phaeocystis blooms reach a stationary growth phase, during which excess energy is stored as carbohydrates. This so-called overflow metabolism increases the ratio of carbohydrate-C to POC to 0.4–0.6 during the stationary phase, leading to an increase in the C/N and C/P ratios of Phaeocystis organic matter. Overflow metabolism can be channeled towards both glucan and mucopolysaccharides. Summarizing the available data reveals that during the stationary phase of a bloom glucan contributes 0–51% to POC, whereas mucopolysaccharides contribute 5–60%. At the end of a bloom, lysis of Phaeocystis cells and deterioration of colonies leads to a massive release of DOM rich in glucan and mucopolysaccharides. Laboratory studies have revealed that this organic matter is potentially readily degradable by heterotrophic bacteria. However, observations in the field of accumulation of DOM and foam indicate that microbial degradation is hampered. The high C/N and C/P ratios of Phaeocystis organic matter may lead to nutrient limitation of microbial degradation, thereby prolonging degradation times. Over time polysaccharides tend to self-assemble into hydrogels. This may have a profound effect on carbon cycling, since hydrogels provide a vehicle to move DOM up the size spectrum to sizes subject to sedimentation. In addition, it changes the physical nature and microscale structure of the organic matter encountered by bacteria which may affect the degradation potential of the Phaeocystis organic matter.

Stability and instability of quiescently active volcanoes: The case of Masaya, Nicaragua

Quiescently active volcanoes are enigmatic due to their restlessness but lack of eruptive activity. I present a model of coupled conduit convection and foam accumulation to explain degassing behavior of Masaya, an active volcano in Nicaragua that is currently emitting large amounts of gas but not erupting. Gas-rich magma is transported through a conduit 2–6 m in radius and then released into a shallow reservoir. The magma is degassed in the reservoir and forms a foam 1–3 m thick at the top with bubbles 20–60 µm in diameter. The foam layer is stable because the input of gas into the foam is balanced by gas release through a vent to the surface. If the foam layer is destabilized, the volcano can erupt explosively. The most likely cause of foam destabilization is a large injection of volatile-rich magma from deeper levels into the shallow conduit-reservoir system, thereby increasing magma fluxes and gas fluxes, exsolving large gas bubbles, and reducing surface tension of the magma.

Performance Evaluation of a ‘Sequential‐Batch’ Temperature‐Phased Anaerobic Digestion (TPAD) Scheme for Producing Class A Biosolids

Laboratory studies were conducted to evaluate the performance and operational stability of a Temperature-Phased Anaerobic Digestion (TPAD) system modified to operate in the sequential-batch mode. The system fed with a 40:60 mixture (dry weight) of primary sludge (PS) and waste activated sludge (WAS) at 5.5% solids showed stable performance with minimum variation in operational parameters such as biogas production, VFA to alkalinity ratio, pH, and foam accumulation at system retention times as short as 12 days. The maximum volatile solids removal (VSR) of 52.5% was achieved at a system retention time of 16 days. The system did not show any effects of "shock loading" at the retention times studied and outperformed a "conventional" mesophilic system operated at a longer retention time. The system was effective in reducing the densities of pathogenic indicator organisms in the biosolids to levels lower than those specified by U.S. EPA for Class A designation.

Long-term analysis of a full-scale activated sludge wastewater treatment system exhibiting seasonal biological foaming

The seasonal accumulation of biological foam on the activated sludge system of the Urbana-Champaign Sanitary District Northeast (UCSD-NE) wastewater treatment plant was investigated over an 8-year period by statistical analyses including path analysis, multivariate regression, and principal component analysis. Results of these analyses suggested that variation in the activated sludge reactor temperature and the use of a stream bypassing the primary clarifier were the two main factors determining the observed temporal foam profile. Characterization of the primary clarifier influent and effluent suggested the involvement of high lipid loading rates from the bypass stream in foam accumulation. In light of these results, it is hypothesized that increasing temperatures and lipid loading rates are responsible for foam formation through the same mechanism: the foam-forming microbial population is specialized in consuming lipids, substrates classified as slowly degradable. When the temperature increases, the rate of lipid hydrolysis becomes sufficiently high for this population to become abundant, accumulate on the surfaces of the aeration basins, and cause biological foaming.

Function and significance of very low density lipoprotein receptor subtype II.

To explore the functions of very low density lipoprotein receptor (VLDL-R) subtype II in lipoprotein metabolism and foam cells formation, the recombinant plasmid with the two subtypes cDNA was constructed respectively, the 1dl-A7 cell lines were transfected and two cell lines expressing VLDL-R were obtained: one stably expressing the VLDLR with the O-linked sugar region (type I VLDLR) and the other without the O-linked sugar region (type II VLDLR). In the study on binding of VLDLR to their nuclein labeled natural ligands (VLDL and beta-VLDL), it was found that surface binding of 25 I-VLDL or 125 I-beta-VLDL of 1dl-A7 cells transfected with type I VLDL R recombinant (1dl-A7-VRI) was more higher than that of 1dl-A7 cells transfected with type II VLDLR recombinant (1dl-A7-VRII). After being incubated with VLDL for different time, the contents of triglyceride and total cholesterol in cells were mensurated, and the formation of foam cells and accumulation of lipid in cells was observed by oil-red O staining. The results showed that the contents of triglyceride and total cholesterol in 1dl-A7-VR I were much higher than those in 1dl-A7-VR II, and 1dl-A7-VR I could transform into foam cells notably. It was suggested that type I VLDLR binds with relative higher affinity to VLDL and beta-VLDL, and internalizes much more lipoprotein into cells. As a result, we can conclude that type I VLDLR plays a more important role in lipoprotein metabolism and foam cells formation than type II VLDLR.

Adsorption accumulation of proteins and dyes in foams of solutions and waste water

We have previously derived equations that connect the main characteristics of foam accumulation and the separation of surfactants (accumulation ratio, liquid carry away, efficiency of surfactant extraction, degree of extraction and another) to properties of the surfactant solution (i.e. surfactant adsorption and surface tension) and the structural parameters of foam (expansion ratio, bubble size, film thickness). In these experiments we have applied these findings to investigations of proteins accumulation in foam at extraction from the waste water of heparin production, the accumulation of soap, made from the sulfate liquor of wood pulp manufacture, gelatin and dyes. Foam accumulation of protein substances from the waste water stream of heparin production was effected after dialysis in order to purify the solution from salts at pH 5 when the most stable foam was produced. For foam drainage under gravity the maximum accumulation ratio ( R max f ) was to 1.5 and R max f = 6 when the pressure difference was created in the liquid phase of foam. Accumulation of gelatin was carried on a stationary foam and in a moving foam at pH 4.8 (the isoelectric point) from a solution of gelatin and sodium dodecylsulfate mixture (at a gelatin/surfactant concentration ratio of 1.73 which corresponds to the formation of their complex). In dry foams R max f was 50 for the moving foam and R max f = 150 in the stationary foam. Separation of thymol blue shows that this dye forms the most stable foam in the acid region at pH 2.5 and in this region of pH dye is adsorbed on the foam bubble surfaces and the residual part of dye solution changes pH becoming more alkaline.

An experimental study of holdups in large-scale p-xylene oxidation reactors using the [formula omitted]-ray attenuation approach

The gas holdups of an air-acetic acid-terephtalic acid system in a pressurized bubble column of 0.3 m diameter and 6.6 m height was studied. The overall holdups and the distribution of local holdups in the churn-turbulent flow regime with a gas velocity up to 0.54 m/s and a system pressure 1.0 MPa were obtained using γ -ray densitometry. These results are in agreement with the results obtained in the system by differential pressure methods. The effects of superficial gas velocity, static liquid height, concentrations of acetic acid, solid and antifoam agents on the overall gas holdup were investigated. The local gas holdup increases with increases of the axial height and superficial gas velocity, and there is a section of accumulation of foam in the upper section of the column. The results also show that both the static liquid height and concentration of acetic acid have no significant effect on the overall holdup. The superficial gas velocity and concentration of solids and of antifoam agents have a great influence on the gas holdup. A correlation for the estimation of the overall gas holdup was obtained, which is significant for the design and scale-up of oxidation reactor of p-xylene.

Ceramic membranes for ozonation in wastewater treatment

Ozone, due to its high oxidative capacity, is often used in water treatment for the degradation of organic pollutants. Unfortunately, the application of ozone in the form of gas bubbles causes foam problems. To avoid the development and accumulation of foam, the transfer of ozone into the water through gas permeable membranes was investigated. Ceramic membranes were used because of the chemical inertness of the material. The hydrophilic behaviour of ceramic membranes made of metal oxides causes the water to penetrate into the pores. This creates a diffusion resistance for the ozone which decreases the transfer rates. To keep the water out of the porous structure and maintain the gas/water interface at the membrane surface, the surface properties of the membrane were changed. The membrane was soaked in a solution of a fluorinated compound. Water drop measurements and transfer rates were investigated and confirmed the stability of the hydrophobic nature of the membrane surface. The ozone transfer rates thus achieved were in the range of 12 grams of ozone per square meter per hour.

Application of activated sludge and biofilm sequencing batch reactor technology to treat reject water from sludge dewatering systems: a comparison

Side stream reactors to treat reject water from sludge dewatering facilities may be considered to be small treatment plants embedded in large ones. Combination of main stream and side stream treatment provides a number of advantages. Of major importance is that tailored processes can be employed for the two waste streams very different in composition and concentration. Pilot scale experiments were conducted to study the applicability, and to compare the performance of two types of Sequencing Batch Reactor (SBR) systems, an activated sludge and a biofilm SBR. The reactors were operated to achieve nitrification only. Subsequently, the effluent of the reactors is fed into the anoxic zone of the main stream activated sludge plant to achieve denitrification. In general it can be stated that both, activated sludge and biofilm SBR systems are applicable for treating reject water of high ammonia loading. Nitrogen removal efficiencies of more than 90% could be obtained with both systems. If complete nitrification without denitrification is to be achieved, pH control is necessary. However, the amount of sodium hydroxide required for adjusting the pH during nitrification is significant. Foam development and accumulation caused major problems, especially during the early stage of start up. But the time proceeding, and by changing the type of polyelectrolyte used in the sludge dewatering process foam problems could be kept under control.

Induction of macrophage foam cell formation by Chlamydia pneumoniae.

Foam cell formation is the hallmark of early atherosclerosis. It was found that the intracellular bacterium Chlamydia pneumoniae induces foam cell formation by human monocyte-derived macrophages. Exposure of macrophages to C. pneumoniae followed by low-density lipoprotein (LDL) caused a marked increase in the number of foam cells and accumulation of cholesteryl esters. Foam cell formation was not inhibited by the antioxidant butylated hydroxytoluene nor fucoidan, suggesting that lipid accumulation did not involve scavenger receptors. In contrast, addition of heparin, which blocks binding of LDL to the LDL receptor, inhibited C. pneumoniae-induced foam cell formation, suggesting that the pathogen induced lipid accumulation by dysregulating native LDL uptake or metabolism (or both). These data demonstrate that an infectious agent can induce macrophage foam cell formation and implicate C. pneumoniae as a causative factor in atherosclerosis.

The mucilage phenomenon in the continental coastal waters of the North Sea

The basic mechanisms behind the mucilaginous phenomenon in the eutrophicated continental coastal waters of the North Sea are analysed in relation to observed short-term and predicted long-term quantitative and qualitative changes in riverine nutrient delivery to this coastal area. It is shown that foam accumulation observed every spring at sea surface and on the beaches, under windy conditions, results from food chain disruption due to the proliferation of one single phytoplanktonic species, the colony-forming Phaeocystis, peculiar physiology and biochemistry of which make them largely unpalatable for mesozooplankton and refractory to microbial degradation. Based on the knowledge of the carbon and nutrient metabolism of Phaeocystis colonies, making them more competitive than other phytoplankters to utilize nitrate as nitrogen source in dim coastal waters, it is concluded that the massive development of Phaeocystis colonies should have been enhanced by new sources of riverine nutrients, severely deficient in silicate and phosphate with respect to nitrogen and for which nitrate is the dominant form. Accordingly, historical and present-day records of bulky Phaeocystis colony blooms are closely related to those changes in land use and/or hydraulic and waste water managements that have led, over the last 100 years, to increased delivery of nitrates to the coastal area.

Dynamics of degassing at Kilauea Volcano, Hawaii

At Kilauea volcano, Hawaii, the recent long‐lived eruptions of Mauna Ulu and Pu'u O'o have occurred in two major stages, defining a characteristic eruptive pattern. The first stage consists of cyclic changes of activity between episodes of “fire fountaining” and periods of quiescence or effusion of vesicular lava. The second stage consists only of continuous effusion of lava. We suggest that these features reflect the dynamics of magma degassing in a chamber which empties into a narrow conduit. In the volcano chamber, gas bubbles rise through magma and accumulate at the roof in a foam layer. The foam flows toward the conduit, and its shape is determined by a dynamic balance between the input of bubbles from below and the output into the conduit. The foam thickness is proportional to (μlQ/ε2 ρl g)1/4, where μ l and ρl are the viscosity and density of magma, ε is the gas volume fraction in the foam, g is the acceleration of gravity, and Q is the gas flux. The bubbles in the foam deform under the action of buoyancy, and the maximum permissible foam thickness is hc = 2σ/ερlgR, where σ is the coefficient of surface tension and R is the original bubble radius. If this critical thickness is reached, the foam collapses into a large gas pocket which erupts into the conduit. Foam accumulation then resumes, and a new cycle begins. The attainment of the foam collapse threshold requires a gas flux in excess of a critical value which depends on viscosity, surface tension, and bubble size. Hence two different eruption regimes are predicted: (1) alternating regimes of foam buildup and collapse leading to the periodic eruption of large gas volumes and (2) steady foam flow at the roof leading to continuous bubbly flow in the conduit. The essential result is that the continuous process of degassing can lead to discontinuous eruptive behavior. Data on eruption rates and repose times between fountaining phases from the 1969 Mauna UIu and the 1983–1986 Pu'u O'o eruptions yield constraints on three key variables. The area of the chamber roof must be a few tens of square kilometers, with a minimum value of about 8 km2. Magma reservoirs of similar dimensions are imaged by seismic attenuation tomography below the east rift zone. Close to the roof, the gas volume fraction is a few percent, and the gas bubbles have diameters lying between 0.1 and 0.6 mm. These estimates are close to the predictions of models for bubble nucleation and growth in basaltic melts, as well as to the observations on deep submarine basalts. The transition between cyclic and continuous activity occurs when the mass flux of gas becomes lower than a critical value of the order of 103 kg/s. In this model, changes of eruptive regime reflect changes in the amount and size of bubbles which reach the chamber roof.

Physical, chemical, and biological consequences of episodic aluminum additions to a stream1

AlCl3 was added to a second‐orderroborated field results, added Al producing a 20% reduction in surface tension. We suggest that added Al may have associated with organic functional groups, rendering DOC more hydrophobic and less soluble. Some of these alumino‐organic substances subsequently may have accumulated at the air‐water interface. Terrestrial and aquatic invertebrate drift was also altered with elevated Al; we attribute drift to responses to chemical changes in the stream such as Al and H+ toxicity or to a physical change in surface film. stream to simulate episodic increases in Al concentration during acidic snowmelt. Significant decreases in pH and DOC and accumulation of foam at the surface (visible evidence of reduced surface tension) accompanied a stepwise increase in Al in the water. Laboratory experiments cor

Application of gas permeable membranes for auxiliary oxygenation of sequencing batch reactors

In a Sequencing Batch Reactor (SBR) the substrate concentration is intended to increase during the fill phase to allow the heterotrophic bacteria to periodically enjoy maximum growth conditions. When growing at a maximum rate, however, the bacteria do also respire at a maximum rate, and it can be a problem, technically, to satisfy the oxygen demand thus generated. Use of conventional aeration systems to meet peak oxygen demands has proven unsatisfactory in some cases because of foam accumulation and volatilization of noxious substances.To satisfy the peak oxygen demand a membrane oxygenation system was developed and tested under field conditions. Silicone tubing was submerged in a Sequencing Batch Reactor, and loaded with pure oxygen whenever necessary. As demonstrated, oxygen penetrates through the wall of the tubing and contributes to a rapid increase of the oxygen concentration in the reactor. Long term experiments were conducted to study the applicability of this technique. Results are promising.

Erfahrungen mit der Auswaschung von Kartoffelreibsel ohne Wasserzusatz

AbstractExperience in Potato Pulp Washing without Water Addition. In order to reduce the quantity of waste water from potato starch factories many have tried to keep the amount of water, required for washing out the starch from the pulp as low as possible. Our process is based on utilization of the water contained in the potatoes (approx. 80%, including soluble components) for starch extraction, in such a way that undiluted fruit water is separated and further treatment can be carried out in a comparatively economical way.Most of today's starch factories are tied up with production methods that make it impossible to utilize the water contained in the potatoes, as there is firstly no possibility of recirculating the fruit water and secondly there are foaming problems causing a negative effect on the efficiency.A continuous process guaranteeing a direct flow, excluding accumulation of foam, was installed and tested in both a Swedish and in a Dutch factory. The experience obtained showed that starch extraction with fruit water has no negative influence on the efficiency of the extraction (approx. 1 % free starch in the pulp DS/DS) and that up to 80% of the fruit water could be removed in a concentrated form. By extending the extraction process, and by using 300 l of process water from the refining section per ton of potatoes, separation of the fruit water can be increased up to 97%.