Analysis of sludge flocculation and emulsions with Lumifuge Separation Analyser

Answers to questions from users of the analytical centrifuge

further information on sludge related applications

...we've bought a Lumifuge 116 and we are now
performing some trials on flocculated sewage sludge.
During these trials, we encountered a few problems leading to following
questions:
*Do you have application notes for flocculated sludge (in english or
german)?
*We are currently using glass vials with 2 ml of sludge. We do see
however that the light intensity in the cleared zone is much more than
100 %. Should we tackle this problem by putting a lower intensity in the
method section ?
*Do we have to homogenize the light at all possible rotational speeds or
is it sufficient to do this at e.g. 1000 rpm ? Do I have to do a
homogenisation with a water filled glass cuvette when using these types
of vials ? Do I have to change something on the pixel settings in the
Menu options.../light homogenisation ?

On the preprint server of chemweb.com the following two articles are assessible:

Investigations on sludge dewatering with the separation analyser LUMiFuge 114
T. Sobisch, D. Lerche, 2000
shifted by elsevier to
Chemistry Preprint Archive, Volume 2002, Issue 10, October 2002, Pages 1-11
http://www.sciencedirect.com/preprintarchive

Pre-selection of Flocculants by the Separation Analyser Lumifuge 114
T. Sobisch, 2002
shifted by elsevier to
Chemistry Preprint Archive, Volume 2002, Issue 4, April 2002, Pages 265-274
http://www.sciencedirect.com/preprintarchive

The first considers general aspects including sludge characterization, the second is a kind of progress report focussing on selection of flocculants for dewatering in decanter centrifuges.
The latest in the series of sludge related publications is the paper that will be presented at the World Filtration Conference - wfc 9 April 18-22 2004 in New Orleans.

# To problems with the glass cells
To study the dewatering behaviour and packing and elasticity of the sludge cake the use of the round glass vials is the only good choice you have at present, however, evaluation of the resulting centrate using these cells is nearly impossible.
Please consider the following,
To trace the kinetics of sludge separation, cake compressional behaviour the precise determination of transmission of the supernatant is not necessary. For evaluation of clarification you should use rectangular cells.
Due to the curvature the cells act as optical lenses, causing an amplification of the incoming light. The magnitude of this effect depends on turbidity insight the sample, quality of the glass tubing and of the very exact position where the vial is hit by the light beam. So you will be unable to ensure reproducible conditions. To improve the situation a little, you might do the homogenization in front of the measurement under the same conditions with the cells filled with water only, however, you should ensure that the position is not altered around the axis of the cells. You then might check the reproducibility of the results (caution!).
In case, the sludge samples have initial total solids below 3 - 4 % wt you might consider increasing the sludge volume above 2 ml (max. 5 ml!) to enhance precision of determination of the volume of the sludge cake. If you are working at the highest centrifugal speed you should be able to trace the phase boundary after 10 to 30 s.
You might determine the volume of the sludge cake from the position of the phase boundary after calibration.

see

How to determine the position of the bottom of the measuring cells and

How to determine volumes (sediment, cream or water layer)

The calibration can be done by filling a set of cells with different amount (mass) of water and do a run in the lumifuge. The position of the meniscus can be traced by the location of a sharp insection of the transmission profiles. From one or two runs you will get a set of data - position - volume. This can be used to fit it by an equation, lets say y = a + bx + bx². Then you will be able to compute all data for the sludge volumes.
Please be aware, that if you take the flocculated sludge samples, in most cases you cannot ensure that the initial total solids content of this sample is identical with that of the reservoir. However, variations in the initial total solids have a marked influence on results measured. For a sample of the same quality but higher solids content the kinetics will seem more hindered and due to a higher excess pressure the samples will compact to a higher density. Therefore, it should be necessary in most cases to determine the total solids content after measurement (drying). We would propose to take parallel samples and do the measurements twice or three times.
The suggestions above are related to the measurement of sludge dewatering, especially in the light of flocculant selection. If your investigations have another focus, eventually, a different approach is needed.

# homogenization
It will be sufficient to do the homogenization at a medium speed. However, if you do this with the filled glass cells, then it should be the same as during the measurement.


Analysis of oil in water (o/w) and water in oil (w/o) emulsions - emulsion type

Chemistry Preprint Archive, Volume 2004, Issue 5, May 2004, Pages 7-18

Einfluß der Tensidzusammensetzung

Using analytical centrifugation determination of O/W or W/O emulsion type is as simple as in other cases when the emulsion starts to separate.
During centrifugation an osmotic pressure is exerted onto the emulsion, forcing the dispersion media out of the space between the droplets. For a detailed theoretical description of this process see for example:

S. Tcholakova, N.D. Denkov, I.B. Ivanov and B. Campbell, Langmuir 18(23) (2002) 8960.

Therefore, you can already trace the emulsion type at the beginning of the separation.

O/W - at the cell bottom you will trace a clearing-up (oil droplets are depleting), at the top layer a zone of a concentrating emulsion appears (low transmission). Release of oil from this emulsion might occur or not (thin upper layer with higher transmission) as a secondary process.

W/O - clearing-up at the upper part of the sample (water droplets are depleting), emulsion is concentrating towards the bottom and so forth.

In summary, you should try to deduce the emulsion type from the first changes that can be noticed because at a later stage secondary processes might occur. Please be cautious and have look at the samples before you place them into the LUMiFuge and after measurement. Experimental errors, like wall effects might cause confusion.

Water and Wastewater.com Help Forum - how to measure a spheres surface hydrophobic?

Water and Wastewater.com Help Forum - how to measure a spheres surface hydrophobicity?

Question
I am supposed to measure the anaerobic granules' surface hydrophobicity. but is there any method I can use to quantify it?
I only know the Contact Angle for plat surface and MATH for single cell.

Any suggestion is welcomed. Thanks!

First thoughts
If it is possible to dry the granules I would try one of the following approaches
# Washburn method, which was developed for contact angle measurements of powder packings, measures the height a liquid reaches due to capillarity. You may find a lot about this method at the internet, however, I doubt nobody has applied this method for anaerobic granules.
# related to the Wilhelmy method you might fix the individual granules to a tensiometer or alike and measure the force when the granules just contact the liquid surface and the change with time.

An elaborate method would be to measure the ad-/absorption in a mixture of liquids of different polarity.
Eventually the following could work, rinse the granules with alcohol and equilibrate them with a mixture of alcohol - octane
(or another mixture). Compare the initial liquid composition with that after equilibration.
Alternatively, use "inverse chromatography" (characterization of the stationary phase with the mobile phase). You can find a lot on this method at the internet.

Please send comments

just another, maybe more appropriate method

evaluation of packing density after sedimentation

after sedimentation the packing density achieved will be characteristic of surface polarity. Packing density should be determined straightforward in the natural media. Eventually repeated slight agitation of the sediment will be necessary to obtain reproducible packing density values. The more hydrophobic the surface, the more irregular (looser) will the packing due to the surfaces sticking together at the hydrophobic sites.


Further discussion

please consider, it will be difficult to test the surface properties without any alteration of the surface to some degree. This is also the case for the MATH method - contact with the hydrocarbon will to some extend "change the real surface properties of anaerobic granules since cell surface would be damaged".
Wilhelmy method is known as "Wilhelmy plate method" measuring the force at equilibrium for a wetting plate immersed in a liquid. From this one determines surface tension. What I meant was - if you have to types of granules with approx. the same volume, shape and density and contact them each with a liquid (water or organic solvent) the force acting on the granules will depend on their wetting properties (polarity).
Mixed adsorption - determine the concentration of the two components after equilibration - which component shows prefered sorption and to which extent. Lets say in an ethanol cyclohexane mixture I expect that ethanol will be depleted in the mixture due to prefered interaction with the cell surface. For the more hydrophobic granules depletion of ethanol will be less, for very hydrophobic granules eventually cyclohexane will be depleted.
Microsphere absorption method - you might work with a modification of that method. Use an reversed phase material of a filling material for chromatography - these materials are usually some kind of silica gel with grafted alkyl groups. You may also use silica gel or other solid powder (inorganic with negative surface charge or microcrystallin cellulose) wash them with a solution of a cationic surfactant and than with water, so you will get hydrophobic particles.
Sediment packing density is the ratio of volume of the particles (mass/density) and the volume of the sediment.

# ethanol-cyclohexane adsorption
please consider the different purpose
Kanyo et al. tried to gain exact adsorption isotherms over the whole range of composition of the mixed solvent. They had to use an analytical method which is able to detect even very small changes in composition.
Your purpose is a fast, qualitative characterization of surface hydrophobicity.
I dont know if 10 or 30 minutes will be more appropriate.
One or two initial composition will suffice. They have to be chosen in a range where the shift in concentration is expected to be high, i.e. for preferential adsorption of ethanol at lower ethanol concentration.
Another way to obtain well detectable changes in compositon is to use a high solid (surface) to solvent ratio. Eventually, most simply put the granules in a column and fill it with the mixed solvent and drain it off after a distinct time period. Gas chromatography would be a simple analytical method.

# fluorescence
'fluoresent hydrophobic solvent' will not have high activity, polyaromatic hydrocarbons as pyrene, have high flourescence activity but can only be dispersed, lets say after introduction via an ethanol or acetone solution. It seems difficult to me to use this to measure surface hydrophobicity.

Zum 200. Geburtstag von Immanuel Kant – Weltfrieden gegen

could someone translate this interesting article ???

Inhalt einer e-mail von einem Mitglied der DFG-VK Berlin
Liebe friedensfreunde,

hier einen Hintergrundsartikel aus der Wochenendausgabe des ND v.
17.94.04 der den Frieden verstehen hilft- oder!!??

Wünscht alles Gute
Lothar Eberhardt


Pax Kantiana contra Pax Americana
Zum 200. Geburtstag von Immanuel Kant – Weltfrieden gegen
Weltherrschaft

Von Hermann Klenner

Die Anzahl derer, die des Immanuel Kant transzendentalphilosophischen
Weltanschauungsansatz wirklich verstanden haben, dürfte im Lande seiner
Muttersprache kleiner sein als die der beamteten Philosophieprofessoren.
Wer beherrscht schon den Denkweg von Leibniz zu Hegel, ohne den
begriffen zu haben der in dessen Mitte philosophierende Kant nicht
angemessen gewürdigt werden kann?
Der am 22. April 1724 geborene und 1804 gestorbene, in Königsberg
lebende und lehrende, aber auch in Berlin publizierende Immanuel Kant
hat sich zwischen seinem 60. und seinem 75. Lebensjahr zu keinem Problem
häufiger geäußert als zu der Frage, ob und wodurch das seiner Meinung
nach größte Übel der Völker, der »kontinuierliche Krieg« zwischen ihnen,
in einen »immerwährenden Frieden« überführt werden könne? Als zu Beginn
dieses Jahres das anstehende doppelte Kant-Jubiläum (Todestag: 12.
Februar 1804) auch in den ernsteren Tageszeitungen reflektiert wurde,
ist merkwürdiger Weise aber genau dieses Fundamentalproblem der
Menschheit, das Kant in mindestens acht verschiedenen seiner Schriften
sowie 1795 in einem zunächst in zweitausend Exemplaren verbreiteten
selbstständigen Traktat von 104 Seiten – »Zum ewigen Frieden. Ein
philosophischer Entwurf« – erörtert hatte, buchstäblich links liegen
gelassen worden. Die Leibniz-Sozietät jedoch hat sich auch dieser Frage
angenommen. Zufall? An Zufälle solcher Art zu glauben, ist mir die
Naivität abhanden gekommen. Inzwischen ist im Zentralorgan des deutschen
Kapitals Kants Friedenstext sogar als höchstens für Sonntagsreden
geeignet, ansonsten aber als hirnrissig bezeichnet worden; seine
Schwäche offenbare sich heutzutage in der Hilflosigkeit der Vereinten
Nationen gegenüber jener Supermacht, die jetzt das Recht des Stärkeren
wahrnehme und wohl auch wahrzunehmen die Pflicht habe. Zuvor war bereits
– entgegengesetzt sinnwidrig – Kants Friedensschrift als
Rechtfertigungsgrundlage für den NATO-Krieg gegen Jugoslawien
monografisch missbraucht worden.
Als Kant während der damaligen Kriegszeiten in die europaweit wuchernde
Friedens-Diskussion, übrigens zu Gunsten der französischen Revolution,
eingriff, hieß es in einer der vielen seinem Friedenspamphlet gewidmeten
Rezensionen, dass die erhabene Gesinnung des ehrwürdigen Weisen noch von
der spätesten Nachwelt bewundert werden würde.
Gesinnung hin, Gesinnung her; dafür braucht man keine Philosophen. Man
hat sie, oder hat sie nicht – die Gesinnung. Es ist weniger das
Bekenntnis Kants zum Frieden, das heute in Erinnerung zu rufen viel Sinn
macht; es sind vielmehr seine Erkenntnisse, die ihn als einen
philosophischen Zeitgenossen noch unserer politischen Gegenwart
ausweisen, wenn es darum geht, Einsichten in das unbedingt Erforderliche
zu gewinnen, um dem heutigen militärischen Morden ein Ende zu bereiten.
Wie es einem Systemdenker zukommt, hat Kant seine friedenspolitischen
Auffassungen zu einer geschlossenen Theorie verdichtet. Diese wiederum
hat er als deren notwendiges Element in seine Geschichts-, Sozial- und
Rechtsphilosophie integriert. Das alles kann hier nicht einmal in
Umrissen wiedergegeben werden, denn das Gedankengeflecht des Patriarchen
deutscher Metaphysik zu komprimieren, heißt sich dem Verdacht wie der
Gefahr auszusetzen, an seinen Gedankengängen zu manipulieren. Davon
zeugt und lebt eine ganze Literatur.
Vielmehr soll hier auf die damals wie heute zum Selbstdenken
provozierende Substanz seiner Friedenskonzeption verwiesen werden, auch
um das Vorurteil abzubauen, dass deren Autor eine Kontaktaufnahme mit
der Wirklichkeit vermieden habe, damit sich sein genialisches Überhirn
vollständig dem In-sich-Geschäft der Vernunft widmen könne.
Drei Gesichtspunkte sind es vor allem, die zwar nicht den Ruf: »Zurück
zu Kant!« legitimieren, wohl aber die Warnung: »Kein Zurück hinter
Kant!«
Zunächst hielt er das kriegerische Morden der Menschen durch
ihresgleichen nicht für ein durch deren aggressive Triebausstattung
definitiv bedingtes Verhaltensmuster. Ohne sich die Natur des (seiner
Meinung nach aus »krummem Holze« geschnitzten) Menschen schönzureden,
war er jedenfalls der Meinung, dass Kriege gesellschaftsbedingte
Phänomene seien, charakteristisch für vorübergehende Phasen der
Menschheitsentwicklung, und zwar während ihrer barbarischen Zeiten.
Kriegstapferkeit, so schrieb er hintergründig, sei die höchste Tugend
der Wilden – in ihrer Meinung. Frieden, der ewige insbesondere, war für
ihn das Ergebnis eines in der Objektivität menschlicher
Gesellschaftsentwicklung angelegten Fortschrittsprozesses, kein Traum,
auch kein durch Moralisieren herbeizuführendes Sofortereignis, sondern
eine dem »Mechanismus der Natur« gemäße, in der objektiven Tendenz
»einer ins Unendliche fortschreitenden Annäherung« liegende subjektive
Verhaltensentwicklung.
Nicht auf den Edelsinn der Völker, sondern auf ihren Eigennutz setzte
Kant. Kriege zu erleiden, sei keine von Gott auferlegte Strafe, Kriege
zu führen keine göttliche Mission. Letzteres nimmt aber die von der
Bush-Administration mit Panzern und Raketen betriebene Kreuzzugsversion
mit ihrer Anmaßung: »We are a nation under God« nicht weniger in
Anspruch als der Terroristen Taten in Allahs Namen. Newton benötigte für
sein Weltbild einen göttlichen Nachbesserer, der einen möglichen Kollaps
im Sonnensystem zu verhindern hatte; Kant hingegen verdanken wir neben
einer vollständig säkularen Kosmogonie auch eine ihr insofern adäquate
Gesellschaftstheorie. Und zeigen nicht alle unsere eigenen Erfahrungen,
dass Kriege menschengemacht sind: Bevor sie geführt werden, werden sie
vorbereitet und dann auch noch in durchaus irdischem Interesse
herbeigelogen.
Krieg, von Kants Schüler Herder als »Mord auf Befehl« definiert, ist die
brutalste Form von Staatsterrorismus. Er hat nicht nur einen Anlass, er
hat vor allem eine Ursache. Gesellschaftliche Kausalitäten zu verhüllen,
gehört freilich zu den wichtigsten Funktionen jener mit den
militärischen Gewalthabern kollaborierenden medialen Machthaber. Ohne
eine auch diese Zusammenhänge aufklärende Gegensteuerung ist kein Krieg
zu verhindern.
Sodann hat der kleine Mann aus Königsberg die Kriegsentstehung und
-führung aus den Interessen der Obrigkeiten erklärt, und damit das
Interesse am Frieden dem Volk zugeordnet. Es verargten damals sogar die
gewiss nicht reaktionären Humboldt und Schiller Kants Friedenspamphlet
den »wirklich zu grell durchblickenden Demokratismus.« Zieht man die
Konsequenz aus Kants rhetorischer Frage, welches Recht eigentlich der
Souverän habe, seine Untertanen in den Krieg wie auf eine Jagd und zu
einer Feldschlacht wie auf eine Lustpartie zu führen, gelangt man
unschwer zu einer Illegalisierung des Krieges als Mittel der Politik und
zu einer dem Recht eines »jeden Menschen(!), im Frieden zu sein«,
entsprechenden Staatenpflicht zum Frieden. Schließlich stammt von Kant
auch der pazifistische Imperativ: »Ein jeder Staat werde in seinem
Innern so organisiert, dass nicht das Staatsoberhaupt, dem der Krieg
(weil er ihn auf eines anderen, nämlich des Volkes, Kosten führt)
eigentlich nichts kostet, sondern das Volk, dem er selbst kostet, die
entscheidende Stimme habe, ob Krieg sein solle oder nicht.« Nicht das
zur Rechtfertigung von Kriegen allezeit bereite »diplomatische Korps«,
sondern nur das die Drangsale des Krieges und die nachfolgende
Schuldenlast auch erleidende Volk sei über einen Krieg zu befinden
berechtigt.
Übrigens hat Kant sogar die Begründung für einen anarchistischen
Imperativ geliefert: Der Besitz der Gewalt, heißt es bei ihm, verderbe
»unvermeidlich (!) das freie Urteil der Vernunft.« Man denke diesen Satz
zu Ende. Und gibt es nicht tausend gute Gründe, diesen Wahrspruch jenen
amerikanischen Staatsmännern und ihren deutschen Subunternehmern mit
beiden Händen ins Stammbuch zu schreiben, die für die USA, wenn schon
nicht die Berechtigung zu einer Weltherrschaft (Global Domination), dann
zumindest zu einer Weltführerschaft (Global Leadership), ob mit, ob ohne
Krieg, zubilligen?
Und drittens ist Kants ureigenes, überwiegend unbeachtetes Transferieren
seines allseits geläufigen kategorischen Imperativs vom
Gegenstandsbereich der zwischenmenschlichen auf den der
zwischenstaatlichen Beziehungen von allerhöchstem Gegenwartsinteresse.
Ins Außenpolitische gewendet postuliert nämlich sein nicht von Ungefähr
auch in seinem Friedenstraktat zitiertes »Handle so, dass die Maxime
deines Willens jederzeit zugleich als Prinzip einer allgemeinen
Gesetzgebung gelten könne«, die Norm eines Miteinanders
gleichberechtigter Staaten. Diese Option Kants für eine »Föderation nach
einem gemeinschaftlich verabredeten Völkerrecht« stimmt mit den
Grundprinzipien des Völkerrechts der Gegenwart im Großen und Ganzen
überein, steht aber in einem unbedingten Gegensatz zur offiziell als
neue »Nationale Sicherheitsstrategie« verlautbarten und blutig
praktizierten Abkehr der US-amerikanischen Außenpolitik von einer durch
das atomare Patt erzwungenen internationalen Kooperationspolitik hin zu
einer unilateralen Gewaltpolitik. Weltherrschaft oder Weltführerschaft
zu beanspruchen, erwies sich als konzeptionelle Vorbereitung von
Völkerrechtsverbrechen. Die das Verbot eigenmächtig ausgeübter
zwischenstaatlicher Gewalt ebenso wie die »souveräne Gleichheit aller
ihrer Mitglieder« dekretierende Satzung der Vereinten Nationen, und
damit indirekt auch die Friedenskonzeption des Immanuel Kant als
veraltet zu verwerfen, da sie die Präventivkriegspolitik der USA und
ihrer willigen Vasallen nicht hatten verhindern können, entspricht dem
intellektuellen Niveau des Vorschlags, in den Strafgesetzbüchern das
Mordverbot zu streichen, da es die zahlreichen Morde nicht habe
verhindern können!
Es gibt viele Gründe, den – wie ihn Moses Mendelssohn charakterisierte –
»alles zermalmenden Kant« zu ehren. Nicht dass bei ihm die Lösung der
Welträtsel abzurufen wäre. So funktioniert die Rezeptionsgeschichte der
großen Denker nicht. Aber Kant hat Einsichten in den Fortschrittsprozess
der Menschheit beigesteuert, hinter die zurückzugehen sie das Überleben
kosten oder sie zumindest in ihr barbarisches Zeitalter zurückwerfen
könnte. Im eigentlichen Sinne kommt es also gar nicht auf eine Ehrung
Kants an. Etwas für seine wissenschaftliche Hinterlassenschaft zu tun,
heißt den Wahrheitsgehalt seiner Provokationen in unsere eigene
Gedankenwelt einzuschleusen. Dazu haben wir allerdings allen Grund.

Der Berliner Professor, Jg. 1926, Mitglied der Leibniz-Sozietät,
verfasste zahlreiche rechtsphilosophische Arbeiten u.a. zu Hegel,
Hobbes, Kant, Locke und Paschukanis.
Hinweis zu Neuerscheinungen über Kant:
Oskar Negt: Kant und Marx. Ein Epochengespräch. Steidl Verlag, 112S.,
geb., 14 EUR.
Jean Grondin: Kant. Junius Verlag, 159S., br., 11,50 EUR.
Heiner F. Klemme: Immanuel Kant. Campus Verlag, 172S., br., 12,90 EUR.
(ND 17.04.04)

Water and Wastewater.com Help Forum - Why foaming always comes along with rise of pH?

Water and Wastewater.com Help Forum - Why foaming always comes along with rise of pH?

Question
My SBR always have foaming along with a rise of pH within one cycle. I am wondering what substances responsible for this foaming and comes from the rise fo pH?

Answer
often foaming ability is related to pH values above neutral. This is the case for surface active materials like fatty acids and proteins. Alkalinity causes ionization of these substances.

your SBR-mix may contain fatty acids, proteins, biopolymers, biosurfactants and protein hydrolysates. Most of these contain anionic groups, mostly carboxyl groups. The latter are only ionized under alkaline conditions. Besides, the alkaline conditions will favor hydrolysis of biomaterials, this way increasing the concentration of foaming substances. This is related to the comment of judo.
So in summary, yes, under alkaline conditions the carboxyl groups will transform to carboxylate ions. In addition the alkalinity will cause hydrolysis.
What Grrun meant was foaming in hard water is often reduced compared to soft water. The reason behind this is that water "hardness" means the content of Calcium and Magnesium ions. These precipitate fatty acids, but also other anionic surfactants like sulfates and sulfonates. When shifting the pH of hard water to alkaline, hydrogencarbonates with limited solubility are transformed into carbonates with very low solubility thereby precipitating Magnesium and Calcium ions, softening the water. However, in presence of carboxylate ions this will precipitate the foaming substances. So this effect should not be the cause of foaming to occur.
To a more thorough description of the foaming one should also mention that foam stability is the highest at a distinct ratio of dissociated and undissociated carboxyl groups, with foam generation and stability will be influenced differently by this balance.

write comment - Why foaming always comes along with rise of pH?

comment by judo
Fatty acids and (soluble) proteins should be good substrates for bacteria. If there are these compounds remaining in the aeration tank enough to cause foaming, you would be in very serious trouble, far worse than just foaming.

What I meant to say on the earlier reply is foaming phenomenon at high pH is quite normal reaction for activated sludge process. I mean, just keep the pH neutral.


As a part of unknown foaming mechanisms, comformation change of biopolymers such as extracellular polysaccharides and glycoproteins due to pH change might be partly responsible for change in foaming property.

You should also remember that high pH has inhibitory effect on aerobic bacteria because proton-based active transport including oxidative phosphorylation gets difficult at basic environment. Many bacterial species are known to overcome this difficulty though, for example using sodium motive force. Those which do not have this ability have to "die" eventually.

LUM GmbH Presentations at the 9th World Filtration Congress

LUM GmbH Presentations at the 9th World Filtration Congress

Meet you at wfc9

Presentations

Lecture: session 414, Thursday April 22nd, 2004; T. Sobisch, D. Lerche
"Use of Analytical Centrifugation for Evaluation of Solid-Liquid Separation in Decanter Centrifuges: Application for Selection of Flocculants for Sludge Dewatering"

sludge dewatering preprint 1 Chemistry Preprint Archive, Volume 2002, Issue 10, October 2002, Pages 1-11
sludge dewatering preprint 2 Chemistry Preprint Archive, Volume 2002, Issue 4, April 2002, Pages 265-274

The paper reports on a new laboratory method for evaluation of solid-liquid separation in decanter centrifuges based on analytical centrifugation. The method allows to determine the two critical parameters for sludge dewatering – separation rate of sludge flocs and the compressibility (dewaterability) of the sludge cake.
The initial separation rate gives information whether or not the sludge flocs are separated fast enough from the bulk liquid. This relates to the maximum throughput performance at which the decanter can operate. The final cake solids obtained by centrifugation measures to what extent the separated sludge cake can be compressed. This is proportional to the total solids, which can be obtained in the decanter if throughput rate is not critical.
The action of high shear stresses during mechanical processing was modelled by adapting the sample pre-treatment, so that similar changes take place in the sludge samples as in practice.
The performance of the newly developed method was demonstrated by investigations on the effect of the feed solid concentration, of mechanical stresses on sludges before flocculant addition, by an example of flocculant selection and by comparison with results obtained under field conditions.

Poster session: 146, Monday April 19th, 2004; D. Lerche, T. Sobisch
"Characterization of Sedimentation and Consolidation Behaviour of Concentrated Dispersions by Analytical Centrifugation"

The sedimentation and consolidation behaviour of suspensions was experimentally analysed by means of a multisample analytical photocentrifuge. Experiments were conducted covering a broad range of volume concentrations and centrifugal accelerations. The obtained material functions allow to simulate batch sedimentation, filtration and consolidation.
For only hydrodynamically interacting particles the separation velocity decreases with the volume concentration. The so-called hindered settling rate may be fitted to a power law. For rigid spherical particles the exponent was found to be in the range of 3 to 4.6 in dependence on the Reynolds number of the settling particles. In turn the description of sedimentation and packing of deformable particles is possible by using a deformation parameter and the maximum packing density as fitting parameter. The flexible shape leads to an overall lower viscosity. For both rigid and deformable particles theoretical description and experimental results are in excellent agreement.
Interacting particle systems above the gelpoint have to be described by the compressive yield stress. The compressive properties of stable and flocculated dispersions can be easily determined by multisample analytical centrifugation for rapid classification and tailoring of dispersion properties.

The Bioremediation Discussion Forum - Sulfide Resistantance of Bacteria

The Biogroup Home Page

The Bioremediation Discussion Group is the forum for all bioremediation related problems.

found the following interesting discussion:

question

I have a question relating to sulfide resistance mechanisms of sulfate reducing bacteria (SRB). Specifically I am interested in knowing what makes
SRB tolerate high concentrations of sulfide. Any references or pointers would be really appreciated.

Sridhar Viamajala
Research Associate
Washington State University

replies

Bruce Rittmann - John Evans Professor of Environmental Engineering - Northwestern University

While some bacteria might have specialized sulfide-resistance mechanisms, the widespread and widely used strategy is to make the
sulfide unavailable by precipitating it with ferrous iron or a number of other metals. This is a research theme in my group, and it is an
example of what we call bioprotection. In addition, bioprotection works to protect the community against metal toxicity.
So, it is a two-way street.

Valerie Anne Edwards - President - Alken-Murray Corporation - http://www.alken-murray.com

I tackle this problem differently, by introducing selected bacteria with
sulfide oxidizing capabilities. Specifically, I prefer Thiobacillus
denitrificans and Paracoccus pantotrophus, which can utilize sodium nitrate
as nitrogen source and as alternate electron acceptor, creating sulfate or
organic sulfur instead of sulfuric acid, which is the end result when some
other strains of Thiobacillus. We also include sodium nitrate and
dolomitic limestone to further buffer pH in the system. When organic carbon
sources are limited, these strains can use carbon dioxide as their carbon
source.
In an oxygenated system, Starkeya novella can oxidize sulfide and
mercaptans. All of these strains can use carbon dioxide as their carbon
source when introduced to a system lacking organic carbon sources, but
Thiobacillus denitrificans is unable to use organic carbon sources at all,
a totally chemotrophic species.
I also use three strains of a new species of Bacillus I isolated from a
Georgia humified soil deposit, with cationic polymer activity which
inhibits all gram-negative strains, thus creating an environment conducive
to development of unique Bacillus. My new species of Bacillus acts a lot
like the Paracoccus pantotrophus, facultatively heterotrophic, utilizing a
nice array of organic carbon compounds or alternatively utilizing carbon
dioxide while oxidizing hydrogen sulfide and denitrifying any leftover
sodium nitrate, creating sodium sulfate and nitrogen gas. Dr. Frederick
Cohan of Wesleyan University did the DNA hybridization work for these
strains to prove that they are NOT Bacillus mojavensis, as initially
identified by Accugenix using 16S rRNA. According to Dr.Cohan, they are
actually closer to B.subtilis spizizinii and B.valismortis than to
B.mojavensis. I have been using all of these strains commercially since
March of 2003, with great success.
Another treatment option for sulfide oxidizing strains that can denitrify
and use carbon dioxide as their carbon source is the treatment of WWT
effluent with excess nitrate and sulfide and no remaining organic carbon.
In the past, an organic carbon source, such as methanol or acetic acid
would be added and an attempt at creating an anaerobic environment would
have been necessary to force Bacillus or Pseudomonas aeruginosa to
denitrify. T.denitrificans, Paracoccus pantotrophus and my new Bacillus
will all denitrify even when oxygen is present as another option, avoiding
the addition of another pollutant in order to eliminate one that is present.

Hello Valerie-Anne Edwards,

My name is Casey Hubert and I'm a PhD student at the University of
Calgary. I recently read your BioGroup posting about sulfide tolerance
where you took more or a sulfide oxidation angle. I have done some
experiments on sulfide removal with nitrate and molecular analysis of my
experimental system shows some Bacillus homologs are
present. I suspect they are probably heterotrophic nitrate reducers
(organics are also present in the system), and I was intrigued by the
description of your Bacillus strains in the BioGroup
posting - by calling them facultative heterotrophs, so you mean they are
also capable of oxidizing inorganics (ie sulfide)?. Can you refer me to
any papers in which you have discussed or characterized these
Bacillus spp (the posting alluded to DNA studies, etc.)?
Such information, if it is available, might be useful to me as I try to
understand my own results.

Dear Casey,

Yes, my four sulfide oxidizing Bacillus can grow on two selective media i
used to detect their talents and compare with Thiobacillus denitrificans.
The primary media was a thiosulfate based media designed to support
Thiobacillus denitrificans in a BBL GasPak jar with GasPak Plus envelope
to assure no presence of free oxygen and plenty of carbon dioxide. This
was my primary selection media used to screen soil isolates fairly early.
Those that showed good strong growth on that media and also on TSA (not
on Nutrient since they absolutely require 0.5% NaCl, tolerate up to 10%
NaCl), i continued to test their talents and enzymes produced. Since I
wanted sulfide oxidation, and not necessarily thiosulfate oxidation, I
created another selective media, this time with sodium sulfide and sodium
or potassium nitrate in it under the same anaerobic conditions and they
jumped up and said "hey look at me - I love this stuff better than the
thiosulfate media". My final media used acetic acid to adjust pH instead
of hydrochloric acid to see if a tiny bit of an alternate carbon source
would accelerate them and two of the strains that test positive on acetic
acid media with no other carbon source were even more thrilled to go
after the sulfide. The media was so stinky it had to be poured in a fume
hood and it was immediately evident which strains worked by odor
dissipating in two days and color change from green to blue, actually
increased because of use of nitrate instead of acid produced in the
thiosulfate media without nitrate present. They are also capable of a
nice assortment of carbon digestion, as long as at least 0.5% NaCl is
present. Another strain from the same soil showed unusual talents with
nitrogen compounds, first degrading citrate to ammonia changing green to
blue and then 12 hours later back to green, which one of the sulfide
babies did also. I then tried them both in a media used to verify our
ammonia oxidizing nitrifiers are working. See the procedure at
http://www.alken-murray.com/QC2.pdf for details. I ended up
discovering that only two of the strains, the new genus between Kurthia
and Bacillus (5.6% or more from each) and one of the sulfide babies
showed positive results on this media, taking around a week to change the
color to a very pale yellow-orange. I have Chemetrics kits that will
reveal presence of nitrite and nitrate, so i made the STP media without
any color to interfere and used it to check whether nitrite or nitrate
were created and nitrite was plentiful, some ammonia still remained and
no nitrate was created by either strain. I also like the two Paracoccus
pantotrophus I use for comparable behavior in a gram-negative with the
advantage of slime production by the gram-negatives to protect them from
toxic chemicals in the environment and also protect their friends in the
same consortia. The Paracoccus, Starkeya novella and Thiobacillus
denitrificans work well in consortia with my Bacillus babies. Only the
Bacillus can be used in a liquid formula containing 15 to 30% sodium
nitrate, non-toxic micro-nutrients that accelerate performance and
germination of spores once the preservative is diluted enough to allow
them to awaken and go to work, enhanced by a chemical formula to make
them work even better. In liquid form, i usually mix in some FOG
degraders since H2S is often present in collection systems that have a
high buildup of FOG and odors from fatty acids, thus fatty acid degraders
also included. Nitrate alone cannot accomplish sulfide remediation, it
only catalyzes the result if the right bugs are present to be able to use
it. By combining both, I can be absolutely sure of my end result. My
only problem with the sulfide Bacillus has been commercializing them.
They do not grow really well in high numbers unless sodium sulfide and
potassium nitrate and 0.5% NaCl are added to the media. They will not
grow well in typical media used for large scale fermentations. Once we
got over the odor issue and gave them what they wanted, they grew just
like champs with final freeze-dried culture count of 4.2 to 5.85 E11
CFU/g , but without I was lucky to get a result over 1.0 E 10 CFU/g, not
so good for commercial value. My main goal when I began playing with that
specific soil was to find the sulfide oxidizing strains and I was stunned
when nothing I could isolate was gram-negative despite good thiosulfate
growth. Apparently a high-molecular substance in the soil is deadly to
gram-negatives, opening the door for Bacillus to develop new traits.
Accugenix initially identified them as Bacillus mojavensis, so I wrote to
Dr. Cohan of Wesleyan University, who named Bacillus mojavensis and a
number of other Bacillus closely related and we swapped strains. I tested
his and he tested mine and only one of his grew very faintly on the
Thiobacillus media and none on the sulfide-nitrate media, even with a
tiny bit of acetic acid added as an accelerant. Only two of my sulfide
strains can use acetic acid at all and those two also use lactic acid as
sole food source. Dr. Cohan sent me a program and bootstrap showing that
they are actually further away from B. mojavensis and closer to
B.subtilis, spizizinii and B. valismortis, which I found fascinating. Dr.
Cohan conjectures that bacteria pick up a trait and then the DNA changes
to mirror that change. Nobody knows what makes B. mojavensis different
except DNA, so perhaps it has some hidden talent as my babies would have
if I had not been on a mission to find sulfide oxidizing strains and they
turned out to be a new species of Bacillus, the highlight of my work with
bugs. Having screened for salt tolerance for over four years now, I have
assembled an interesting group of strains that i can formulate with, as
needed and I plan to patent 17 of them in a specific formula to solve
something I have been advised not to discuss prior to applying for the
patent. I sent that group of strains to ARS culture collection today,
liking their pricing for patent deposit better than ATCC.


Louis B. Fournier, Ph.D. - STAR Environmental, Inc.

I'm not sure I recall what the exact question is/was. However, suffice it to say that if sulfide in a waste stream is being treated, it might be easier to simply add an appropriate concentration of hydrogen peroxide. Depending upon pH, peroxide reacts with sulfide to form either sulfate ion or colloidial sulfur. This is commonly used to treat sewage effluents in order to eliminate sulfidic odors.

Fred Heyrich - Bio-SURGE, Inc./Neotech.

I use a quadra-peroxide and a non-ionic surfactant to effect conversion to
sulfate from sulfide. Very prompt. I would be willing to send to you
samples for a lab-scale or pilot study. If intersted please contact me by
reply. The technique is rather basic but depends on a quadra-peroxide (300 ppm diluting
an 18% basic solution. All dilutions are rated non-haz.

Water and Wastewater.com Help Forum - Centrifuge (spin) test

Water and Wastewater.com Help Forum - Centrifuge (spin) test

Question
Anyone remember the spin test for solids management? I remember how to do the test.....just can't recall what the numbers meant. I know it was not a true representation of the % Solids. Any help? Using the 12.5 mL graduated vials.

We are down on staffing and some of the concessions are losing a couple days of non-DMR lab data...we are looking to get at least an idea of what is going on with our MLSS in an extended aeration process.

I realize we could probably do the analyses along with the lab and establish some sort of reference chart.....

Answer
as you already noticed the volume of the sediment after spinning cannot be a true representation of % solids.
Consider the following
# depending on the properties of the suspended solids and centrifugal acceleration time to reach equilibrium will vary.
# the relation of equilibrium sediment volume to suspended solids depends on properties of suspended solids, but also markedly on solids concentration. The higher the concentration the higher the excess pressure acting on the sediment.

From this you can see that a spin test can be a method for fast characterization of properties of suspended solids, when total solids are determined in parallel (Our company is offering a multisample analytical centrifuge, which is also applicable for this purpose).
For the intended purpose of measuring suspended solids the method will only be reliable if properties of suspended solids are fairly constant.

Destruction of Tropical Rainforests on Sumatra Continues Relentlessly

ROBIN WOOD Pressemitteilungen

A Robin Wood activist reports from his research trip to Sumatra

After three weeks of research on Sumatra, Robin Wood's Expert on Tropical Forests Jens Wieting draws a bitter conclusion: “The two largest pulp combines in Indonesia, APP and APRIL, continue to plunder the remaining rainforest at a breathtaking speed. Despite international protests the combines still source approximately two thirds of their raw material from areas of precious biodiversity. The extent of destruction is devastating.” Robin Wood and the Indonesian environmental networks WALHI, CAPPA, and Hakiki Foundation are therefore appealing to the paper tradespeople, who are currently meeting at the trade fair PAPERWORLD in Frankfurt, to refuse pulp and paper of Indonesian origin.
“The Sumatran region of Riau is in a state of ecological emergency” reports Jens Wieting, who has just returned from there. “Settlements and streams are severely polluted and the forests are almost completely cleared. They have given way to barren land and monotonous oil palm and acacia plantations. Effectively, there is no state control which could stop the paper, palm oil and timber industries from destroying the last remains of rainforest on the island. Both the military and the police are making profit from the illegal logging business.”

APP and APRIL have the biggest hunger for wood. Credits issued by the World Bank and by private creditors as well as government export credit guarantees from Germany have enabled the two combines to build massive pulp processing plants. To use these to their full capacity the combines do not hesitate to exploit valuable native forests. There is no end in sight for this practise as figures by the Ministry of Forestry, which Robin Wood has access to, reveal: APP is planning to clear a further 160,000 ha of native forest before 2007, APRIL a further 200,000 ha before 2009. In conservation zones and forests such as the Tesso Nilo area, in which APP and APRIL have accepted a logging moratorium due to pressure by environmentalists, illegal logging continues nevertheless.

“The pulp combines have to cut back their overcapacities until they are able to supply the full amount of wood required from their own existing plantations”, Wieting demands. “No sooner will APP and APRIL take action than when they feel that their destruction of rainforests results in decreased demand.”

Indonesian environmental and human rights groups are asking for a nation-wide logging moratorium. Rully Syumanda from the environmental network WALHI in Riau urges: “The pulp and paper industries must stop immediately to cut the Indonesian rainforest and to pollute our environment. Don't buy paper from our forest!”


Contact:
Ute Bertrand,
Press Spokesperson, Ph: +49 40 380 892 22, presse@robinwood.de