ANU - MAC - MEDIA - MEDIA RELEASES - 2005 - JANUARY - 190105FILTERS
"A handful of clay, yesterday’s coffee grounds and some cow manure are the simple ingredients that could bring clean drinking water to developing countries around the globe..."
"Organic materials which are combined with the clay burn away during the firing process, leaving cavities that help produce the structure in which pathogens will become trapped."
Popular Posts
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Water and Wastewater.com Help Forum - Tertiary Treatment Surfactant Foam Question by Hilary - CAMS We have a modified UCT BNR plant ...
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--> Characterization of the dispersion properties of carbon nanotubes in ionic liquids by the separation behaviour in the centrifuga... -
Scope Carbon blacks are widely applied as pigments and fillers in various products (inks, paints, rubber, plastics). A multisampl...
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Scope Selection of emulsifiers and evaluation of emulsion stability is a frequent task. This relates to practical issues like formu...
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CME 2006 World Congress of Emulsions 3 - 6 Oct. 2006, Lyon, France Evaluation of long term stability of model emulsions by multisample analy...
Monday, January 31, 2005
Friday, January 28, 2005
Conversion of activated sludge to granular sludge? - From the Water and Wastewater.com Help Forum
Water and Wastewater.com Help Forum - Conversion of activated sludge to granular sludge?:
"a key to granular sludge formation is the application of hydrodynamic stresses.
I found this website devoted to the topic granular sludge:
http://www.uasb.org/discover/granules.htm, there is also a forum on that page! "
"a key to granular sludge formation is the application of hydrodynamic stresses.
I found this website devoted to the topic granular sludge:
http://www.uasb.org/discover/granules.htm, there is also a forum on that page! "
Thursday, January 27, 2005
Removing or Treating edible oil in waste stream - From the Water and Wastewater.com Help Forum
Water and Wastewater.com Help Forum - Removing or Treating edible oil in waste stream: "please consider that likely most of the oil is bound to the biosolids. You might check that in lab after filtration.
Eventually then oil and biosolids can be removed by filtration in front of the aeration basin. You might make this strategy feasible by looking for filtration aids and/or flocculants.
A further option besides DAF or demulsifier addition is coagulation or flocculation followed by settling.
I do not thing that it is possible to remove oil and biosolids separately unless you apply centrifugation, which is another option. "
Your real problem seems to get started when you are putting the oil / biosolids dispersion into the aerated unit. Obviously here is the ideal place for producing bio emulsifiers. This has to be avoided.
Therefore, the oil loaden biosolids should be removed earlier.
And do not expect that removal of oil covered biosolids is the same as removal of a common emulsion.
Eventually then oil and biosolids can be removed by filtration in front of the aeration basin. You might make this strategy feasible by looking for filtration aids and/or flocculants.
A further option besides DAF or demulsifier addition is coagulation or flocculation followed by settling.
I do not thing that it is possible to remove oil and biosolids separately unless you apply centrifugation, which is another option. "
Your real problem seems to get started when you are putting the oil / biosolids dispersion into the aerated unit. Obviously here is the ideal place for producing bio emulsifiers. This has to be avoided.
Therefore, the oil loaden biosolids should be removed earlier.
And do not expect that removal of oil covered biosolids is the same as removal of a common emulsion.
Scum or foam at filter bed - From the Water and Wastewater.com Help Forum
Water and Wastewater.com Help Forum - Scum or foam at filter bed
obviously you have not only turbidity as a problem in your raw water.
Traces of lime or aluminum salts do not cause foaming!
Therefore you have to identify and remove the foaming substances (natural, like degradation products of resin or manmade).
By the way chlorination will produce byproducts with these compounds leading to deterioration of taste and quality.
Removal might be achieved by ion exchange (if ionic contaminants), adsorption (granular activated carbons), oxidation ...
obviously you have not only turbidity as a problem in your raw water.
Traces of lime or aluminum salts do not cause foaming!
Therefore you have to identify and remove the foaming substances (natural, like degradation products of resin or manmade).
By the way chlorination will produce byproducts with these compounds leading to deterioration of taste and quality.
Removal might be achieved by ion exchange (if ionic contaminants), adsorption (granular activated carbons), oxidation ...
Floating Floc - From the Water and Wastewater.com Help Forum
Water and Wastewater.com Help Forum - Floating Floc: "Floating Floc
� on: Jan 25th, 2005, 11:14pm �"
a part of the flocs is floating when their density is lower than water, obviously. Possible causes are entrapment of gases or oil or both.
The problem might be approached by
# implementing or improving oil/grease separation before coagulation/flocculation. This might also help to reduce costs for chemicals, sludge.
# reduction of or removal of gases entrapped. Perhaps the mixing regime can be modified.
# reduction of floc erosion or increase of time for floc formation to agglomerate the lighter flocs with the bulk of flocs.
# another flocculant might be more effective in forming flocs heavier than water only.
if you are unable to separate the oil before coagulation/flocculation I would suggest addition of bentonite or modified clays for binding of the oil.
As an alternative to add cationic or anionic polymer you should consider dual flocculation, i.e adding them on after the other.
This will require some extensive testing to determine the right order and concentration.
I would guess a small amount of anionic polymer first followed by cationic might work.
� on: Jan 25th, 2005, 11:14pm �"
a part of the flocs is floating when their density is lower than water, obviously. Possible causes are entrapment of gases or oil or both.
The problem might be approached by
# implementing or improving oil/grease separation before coagulation/flocculation. This might also help to reduce costs for chemicals, sludge.
# reduction of or removal of gases entrapped. Perhaps the mixing regime can be modified.
# reduction of floc erosion or increase of time for floc formation to agglomerate the lighter flocs with the bulk of flocs.
# another flocculant might be more effective in forming flocs heavier than water only.
if you are unable to separate the oil before coagulation/flocculation I would suggest addition of bentonite or modified clays for binding of the oil.
As an alternative to add cationic or anionic polymer you should consider dual flocculation, i.e adding them on after the other.
This will require some extensive testing to determine the right order and concentration.
I would guess a small amount of anionic polymer first followed by cationic might work.
Inquiring effect of pH on water surface tension ? - From the Water and Wastewater.com Help Forum
Water and Wastewater.com Help Forum - Inquiring effect of pH on water surface tension ?
In case of substances with 'positive' surface activity of solutes (if the tend to adsorb at the water-air interface) the pH will have an effect if it influences the adsorption tendency.
Weak organic acids will be far more surface active at low pH than in the alkaline region, proteins have their highest surface activity at their isoelectric point.
In case of substances with 'positive' surface activity of solutes (if the tend to adsorb at the water-air interface) the pH will have an effect if it influences the adsorption tendency.
Weak organic acids will be far more surface active at low pH than in the alkaline region, proteins have their highest surface activity at their isoelectric point.
Tuesday, January 25, 2005
Silica aqueous chemistry, behaviour in water/wastewater treatment systems, removal options
Water Online News for wastewater professionals
to download the white paper by Peter Meyers / Resin Tech Inc.
follow the link above
"In water treatment, we are concerned with silica because of its tendency to form deposits (scale) on surfaces it comes in contact with. In boiler and turbine systems, the deposition is often associated with temperature, pressure, and phase state changes that occur. In microelectronics, the concern is deposition and/or changes to the surface properties of the "silicon" wafers. In this paper, we take up the task of describing the behavior of aqueous silica and of the various water treatment processes used for its removal..."
to download the white paper by Peter Meyers / Resin Tech Inc.
follow the link above
"In water treatment, we are concerned with silica because of its tendency to form deposits (scale) on surfaces it comes in contact with. In boiler and turbine systems, the deposition is often associated with temperature, pressure, and phase state changes that occur. In microelectronics, the concern is deposition and/or changes to the surface properties of the "silicon" wafers. In this paper, we take up the task of describing the behavior of aqueous silica and of the various water treatment processes used for its removal..."
Antifouling coatings - TBT- alternatives
The Expert's View: "Jan 12, 2005"
experts view by Sandy Morrison
"Any object left in seawater for some time falls victim to marine fouling - the attachment of algae (seaweeds) and various small marine animals. This can have serious operational and economic consequences - reduced speed and increased fuel consumption for ships, accelerated corrosion and increased risk of storm damage on fixed structures.
For a while, it seemed as though the coatings industry had found the perfect answer to almost every fouling problem: self-polishing coatings which gave a controlled release of the toxin tributyltin (TBT). But TBT has been a victim of its own success:...."
key points
the alternative use of copper containing coatings requires replacement too
"Whales, dolphins and other marine mammals live for decades with little fouling growth on their skins, and release no toxic biocides."
see also Technology update: Antifouling coatings
experts view by Sandy Morrison
"Any object left in seawater for some time falls victim to marine fouling - the attachment of algae (seaweeds) and various small marine animals. This can have serious operational and economic consequences - reduced speed and increased fuel consumption for ships, accelerated corrosion and increased risk of storm damage on fixed structures.
For a while, it seemed as though the coatings industry had found the perfect answer to almost every fouling problem: self-polishing coatings which gave a controlled release of the toxin tributyltin (TBT). But TBT has been a victim of its own success:...."
key points
the alternative use of copper containing coatings requires replacement too
"Whales, dolphins and other marine mammals live for decades with little fouling growth on their skins, and release no toxic biocides."
see also Technology update: Antifouling coatings
Sunday, January 23, 2005
Chelants in Industrial wastewater - From the Water and Wastewater.com Help Forum
Water and Wastewater.com Help Forum - Chelants in Industrial wastewater:
Question by Catman
What can be done to minimize the effect of chelating agents in Industrial Wastewater where we are trying to precipitate metal hydroxides. We do zinc plating and the problem occurs when we get an influx of the cleaning baths into the WWT system. We supposedly don't have any "chelants" in our cleaning baths (according to the suppliers)but there are constituents that act as chelants (Pyrophosphates,etc.)
answer
I would try coagulation with iron salts. If chelating agents are present the iron will partly displace the zinc bound .
The heavy metals will adsorb to the precipitated iron hydroxides.
The phosphates should not interfere.
Addition of minor amounts of flocculants might improve the coagulation/precipitation process.
reply by Catman
Our pH is controlled closely we raise to 9.8 before adding a cationic polymer and gravity flow to a Lamella clarifier where an anionic polymer is added in the flocculation tank. The system is a continuous flow system which runs about 40 gpm. We raise the pH with sodium hydroxide. The cleaners are usually recovered for reuse but on occasion tanks are overflowed or inadvertently dumped to WWT. On these occasions it takes us several hours (sometimes days) to recover from the cleaner influx. We have about 30,000 gallons of capacity in our equalization tanks and the cleaner still causes us problems. Our polymer supplier suggested a calcium magnesium blend product to help with the problem but we see little effect when this is used. They have also mentioned carbamate but we are hesitant to use this due to it's toxicity.
answer by Dedalus
A pH of 9.8 is a little too high for Zn. When I used to treat a lot of cyanide zinc rinses I used 9.3 as my control level.
Sobisch offers good advice - dose with iron salts. I would add: bring the pH down to 3 - 4 before doing so. This tends to protonate things like organic acid salts and EDTA, disrupting metal complexes. If when the pH is raised again, there is a large excess of ferrous or ferric ions, the chelants will latch onto those, leaving the target ions free to be precipitated as hydroxides.
question by Catman
What effect will the iron salts have on the amount of sludge generated? Our filter cake is classified as non-haz and costs little to dispose of, but our filter press is about at capacity. Just wondering if we would have to add a bigger press. At present we aren't lowering the pH of the incoming stream. It generally is around the 5 - 5.5 range. At one time we were having a problem with small spikes of cadmium but have since eliminated the source. We were running the pH at 9.8 - 9.9 to try and catch the zinc and the cadmium. Since the cadmium is no longer an issue should we lower the pH regardless of whether we add the iron salts?
answer by Dedalus
A modest dose of ferrous sulfate at the incoming pH ought to help you. I would avoid the use of ferric salts, which will precipitate immediately at the pH you indicated, giving little benefit from coprecipitation.
You will see some increase in sludge volumes from this addition. The main thing is to be moderate and use only as much ferrous sulfate as is needed to produce the desired effect.
Can you batch treat those cleaners? They are notorious for causing system upsets. I always excluded them from continuous flow systems I was responsible for running.
And, don't forget to change the final precipitation pH. You will do much better with Zn at 9 - 9.3.
answer by Superglide
I have a little experience with Chelants giving me problems. The stuff is in everything. Some worse than others. I use a chemical called Clearmet. It's really just organic sulfur, but it is not pH dependent. I have found that just relying on solubility curves with pH, will not solve your problem. That only seems to work in the lab. Try as much product substitution upstream as possible.
comment by Dedalus
Re: Solubility products, solubility curves, etc. Superglide is entirely right. They will not reliably predict what will work. If I had a nickel for every time some...person from the front office came to visit me in the field with a table of theoretical data that was supposed to solve my problems, I could retire. My pH 9.3 value was derived from actual batch treatments, not textbook data.
What that theoretical stuff is good for is not telling you what will work, but what absolutely will not work. This can cut down the number of bench tests and sour batches considerably.
Question by Catman
What can be done to minimize the effect of chelating agents in Industrial Wastewater where we are trying to precipitate metal hydroxides. We do zinc plating and the problem occurs when we get an influx of the cleaning baths into the WWT system. We supposedly don't have any "chelants" in our cleaning baths (according to the suppliers)but there are constituents that act as chelants (Pyrophosphates,etc.)
answer
I would try coagulation with iron salts. If chelating agents are present the iron will partly displace the zinc bound .
The heavy metals will adsorb to the precipitated iron hydroxides.
The phosphates should not interfere.
Addition of minor amounts of flocculants might improve the coagulation/precipitation process.
reply by Catman
Our pH is controlled closely we raise to 9.8 before adding a cationic polymer and gravity flow to a Lamella clarifier where an anionic polymer is added in the flocculation tank. The system is a continuous flow system which runs about 40 gpm. We raise the pH with sodium hydroxide. The cleaners are usually recovered for reuse but on occasion tanks are overflowed or inadvertently dumped to WWT. On these occasions it takes us several hours (sometimes days) to recover from the cleaner influx. We have about 30,000 gallons of capacity in our equalization tanks and the cleaner still causes us problems. Our polymer supplier suggested a calcium magnesium blend product to help with the problem but we see little effect when this is used. They have also mentioned carbamate but we are hesitant to use this due to it's toxicity.
answer by Dedalus
A pH of 9.8 is a little too high for Zn. When I used to treat a lot of cyanide zinc rinses I used 9.3 as my control level.
Sobisch offers good advice - dose with iron salts. I would add: bring the pH down to 3 - 4 before doing so. This tends to protonate things like organic acid salts and EDTA, disrupting metal complexes. If when the pH is raised again, there is a large excess of ferrous or ferric ions, the chelants will latch onto those, leaving the target ions free to be precipitated as hydroxides.
question by Catman
What effect will the iron salts have on the amount of sludge generated? Our filter cake is classified as non-haz and costs little to dispose of, but our filter press is about at capacity. Just wondering if we would have to add a bigger press. At present we aren't lowering the pH of the incoming stream. It generally is around the 5 - 5.5 range. At one time we were having a problem with small spikes of cadmium but have since eliminated the source. We were running the pH at 9.8 - 9.9 to try and catch the zinc and the cadmium. Since the cadmium is no longer an issue should we lower the pH regardless of whether we add the iron salts?
answer by Dedalus
A modest dose of ferrous sulfate at the incoming pH ought to help you. I would avoid the use of ferric salts, which will precipitate immediately at the pH you indicated, giving little benefit from coprecipitation.
You will see some increase in sludge volumes from this addition. The main thing is to be moderate and use only as much ferrous sulfate as is needed to produce the desired effect.
Can you batch treat those cleaners? They are notorious for causing system upsets. I always excluded them from continuous flow systems I was responsible for running.
And, don't forget to change the final precipitation pH. You will do much better with Zn at 9 - 9.3.
answer by Superglide
I have a little experience with Chelants giving me problems. The stuff is in everything. Some worse than others. I use a chemical called Clearmet. It's really just organic sulfur, but it is not pH dependent. I have found that just relying on solubility curves with pH, will not solve your problem. That only seems to work in the lab. Try as much product substitution upstream as possible.
comment by Dedalus
Re: Solubility products, solubility curves, etc. Superglide is entirely right. They will not reliably predict what will work. If I had a nickel for every time some...person from the front office came to visit me in the field with a table of theoretical data that was supposed to solve my problems, I could retire. My pH 9.3 value was derived from actual batch treatments, not textbook data.
What that theoretical stuff is good for is not telling you what will work, but what absolutely will not work. This can cut down the number of bench tests and sour batches considerably.
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