Aluminum Sulfate Solution Precipitate Problem

We had almost the same situation when the procurement officer order Aluminium sulfate instead of Alum (30+ years ago).

Maybe you can change your water source. Aluminium sulfate and alkaline water produces a gel.

Your ph is too alkaline. You will have to raise the acidity to keep it from happening again once you solve the gell problem. You might try adding citric acid to the mix, but you will have to ad a mechanical stir to the drain hole for awhile until it clears. If the pipes start to clog with the gel, you are gonna have to drain the tank and clean it manually.

Stirrer or agitator would do the best job of preventing the precipitation and rendering a homogeneous solution. But it may be difficult to included one now if it was not thought at the design stage. Alternately, you may try establishing a constant circulation to prevent precipitation. For this purpose, the top inspection hole could be used. An air operated diaphragm pump could be used for trail purpose. Suction could be taken from the clear liquid zone and discharge could be kept around the tank outlet such that out liquid is well assured with more homogeneous liquid.

Alum being a coagulant, will form deposits in any water dispersed solutions, the very property required of it. You can remove the deposit by soaking in acetic/ formic acid solution with a surfactant. Further as the other member YESYEN suggested, a constant stirring inside the Alum supply/ dosing tank is a must to prevent depositions. Select a suitable speed[ low or med] stirrer or agitator attachment inside the Fiber glass and make it operative all the time. When you feed solids make it drain gently in filled water along with agitation. Top overflow will feed only dilute solution at surface and you may lose effective coagulant partcles into the system.

Good suggestions all. Changing the source water, adding acid to reduce alkalinity and stirring equipment are viable options and great advice.

I suggest that the use of a stirring paddle be used 24/7, at a slow rotational speed so as to keep the solution in continuous suspension...

Good luck!

Aluminium sulfate undergoes hydrolysis in aqueous solution, particularly if the solution is too weak. Do you make it up yourself, or buy it in, ready made? If you purchase it ready mixed, then I suggest you discuss with the supplier. Otherwise, you may need to adjust your mixing procedure to avoid low concentrations and hydrolysis.

This page outlines some of the issues quite nicely.

http://www.generalchemical.com/faq.html

Morrie, Good piece of information. Thanks for the link.

I am not sure of the chemistry of your water nor the design of the tank. Waste treatment includes a lot of parameters for consideration. Alkalinity will be used up by the aluminum sulfate at a rate of 6 moles bicarbonate alkalinity for each mole of aluminum sulfate used. CO2 will be introduced by the reduction of alkalinity. The CO2 could cause some problems if you don't desludge the tank regularly. Adjusting alkalinity too low can then be problematic, so be careful. Adjusting pH however to a level close to 7 may provide some relief but don't expect too much. Jar testing is often used to optimize the dosage of aluminum sulfate.

As this is wastewater treatment it sounds like you need some method of pumping off the sludge at the bottom and do it slowly or periodically. You don't want to pump all the liquid out of the tank. There are some food to microorganism ratios (F/M) you should monitor so you know when to desludge. It is common to pump the waste to digesters or to drying beds or both. You will need to bring yourself up to speed on operating waste water treatment plants. I don't think there is a practical way to reuse the sludge or reclaim the alum form such a process. There will be too many complexes attached to the alum for practical consideration.

Sorry I can't be more specific but you do need to do some work and practice desludging. Alum or aluminum sulfate is an ongoing process to be added regularly.

You seem to be assuming that the tank is a treatment tank. I was assuming from the OP that it is a reagent storage tank.

Yes and I apologize. I didn't read the question correctly and I tried to delete my answer too late. My daughter took my power cord to my laptop and my computer died before I could delete.

Regards

Add sulfuric acid. It will dissolve the aluminum hydroxide to reform aluminum sulfate that can then be reused.

Don't do what a client of mine did. I arrived on site to inspect their fibre glass aluminium sulphate stock tank, to be told 'Paddy's in the tank cleaning out the sediment'. Paddy was using a jack hammer to break it up! Jack hammers and fibre glass don't work well together. You might be able to guess where it was from the hammer operator's name.

I have solved such a problem when I was manufacturing swimming pool chemicals. Adding a little H2SO4 sulphuric acid enough to make the water acidic before desolving Aluminium sulfate prevents this flocking. It will not couse any problem at the futher stage of the water treatment because you need to make a pH adjesment in any way.

Hope this would help.

Thanks everyone for the great advise. I mis-typed...It's a little over a thousand gallon tank. Sorry I didn't get back sooner to read and say thanks. Had to do something Monday... Hose through top to diaphragm pump, back to outlet with steam injection. Cleared the clog and warmed tank from around 35 degrees to around 70. I'm hoping that the little bit of caustic in our boiler steam did no harm. Still don't know what we're going to find when we get the level down. When we get there, and if we find what I'm sure that we will, I'm going to experiment with the ideas presented. Thanks again.

Hi there all, I have a problem with Aluminium Sulphate. Several years back I bought a Dux Heat Pump to replace my old solar water heater.

In April last year we began getting Aluminium Sulphate in our drinking/cold water. I had filled up a couple of 2 litre bottles and took them into my office where during the night I drank one and half of the other. When I went into the the office next day there was half of the contents left had settled out as Aluminium sulphate.

Shaking the bottle sees the gel reabsorbed but as soon as you stop and it starts to settle out.

I worked for one of the local chemical manufacturing places here in Australind WA, who produced Aluminium sulphate way back in the 80's, and living on a farm where we used it to settle out water pumped to a 2000 lt tank from a soak and our swimming pool.

I easily identified what it was in the bottle and had it confirmed by the water authority.

The local water authority began an investigation of where this was coming from. They monitored the water from every pipe that came and went to service us. I even had them supply filters to my house.

Finally one of the guys who came out said he recalled some thing like this happening somewhere else. So we back flushed the water heater and all the lines. This removed the sediment from the water heater.

The problem has returned again, and it seems to be after we use the hot water tap to wash something out and then use the cold water tap to fill up a container. leave it for a while and then we have it settling out as a gel in the bottom of whatever we are using.

I made some enquiries and found out that Dux recommends using Aluminium Anodes in our area because it is deemed an extremely hard water area.

There also seems to be a lot of Chlorine in the water as we have developed green stains running down the wall of the spa and tiles in the shower below the taps in the bathroom

Would a Chlorine filter help stop the formation of the Aluminium Sulphate

Here is an email I sent to an ex workmate to try and get his slant on things.

date 9 April 2010 05:05 subject Lever's Hot water heat pump mailed-by gmail.com

My speculation, Something to add to the email I sent is the back flow can be compounded/created by the pressure created in the tank when heating is in progress, and the ecv's have not released. Water heating is reliant on pressure in the vessel. Opening of a cold water tap may allow an amount of the cold water coming into the bottom of the tank to be pushed back down the line into the flow of cold water when the lower pressure water is created by opening the cold water tap. Because of the flocculation all the junk is in the bottom of the tank and would force some of the Al Sulphate back into the cold water line.I am not sure if the one way valve would be operating properly with that junk in the line anyway. ___________________________________________
What happened to the simple chip heater of my youth.,

I thank you for your time and hope this isn't too far off topic and I look forward to any solutions you may be able to offer. I would like to replace the anodes with the other type

Many thanks

Les Lever

Marine Drive Leschenault WA 6233

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