Water filter sludge - how to dispose of it? 3

[TomaszKruk]

Hello,

I'm working on a project, where we're to design a pumping station that takes water from exisiting intake and pumps it over a large distance. Since the intake doesn't have any water treatment equipment we decided on using a conical filter to purify the water before it is discharged into our suction tank.

Our filter will purify around 1450 m3/h of water containing 20 mg/ml of suspended particles. We calculated that it will produce around 5m3/d of sludge (probably a lot less but we're trying to be safe) that we sadly have nothing to do with. If we assume that all the suspended parts end up in the sludge it adds up to around 0,6 tons per day.

Could anyone provide and advice for what to do with the sludge? There's a large sludge pond belonging to the customer, but it's hundreds of meters away, and the sludge has tendencies to clog pipelines. We would probably need to further waste clean water in order to dilute the sludge, and then pump it.

We were thinking about designing 2 small sludge ponds next to our building, which, supposedly, would allow us to separate the sludge from water to some extend, tranport water elsewhere, and periodically clean one of the ponds and send "condensed sludge" for utilisation. The question of excess water from above the sediment remains - can it be drained to ground or would you say it's not clean enough? Maybe we should pump it?

All in all I came here to ask the question because the above seems a bit obsolete... I was hoping there are better methods for getting rid of the combined problem of excess filter flush water containing large amounts of sediment.

If someone can provide some advice - please, if possible, refer me to some literature or correct search topics so I can properly design the thing.

Exisiting intake uses sumberged centrifugal pumps, so we're not worriend about large object that could clog the line itself.

Regards,
Thomas

 

[itsmoked]

We've made concrete curbed drying spaces. You dump the stuff there and in a few days, to a week, it's dry. Then you can spread it around or use it for fill, as long as it isn't toxic.

We happen to be filtering arsenic so once dry we have to stockpile it until it can go to a hazardous waste site.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[TomaszKruk]

thanks for the info. Definately worth thinking about.

I see you live in States. What's the climate around your drying spaces? Our site is anything but warm and dry.

 

[MartinLe]

Where do you get the water from? If it's a river you might be able to dump the sludge back (obvs. needs to be checked if legal and environmentally responsible), downstream of where you take the water in.

If you need water to dilute the sludge for pumping into an existing lagoon, you could use untreated water of course.

But I never faced *this* particular problem so I'm just brainstorming here.

 

[TomaszKruk]

thanks for the response. I think the entire situation is atypical because you need to do something with the sludge, but it's such a low amount that there's no point in doing anything but minimum :/

Pumping it back into the river is an option - thank you. Time consuming because of legal matters, but yeah - possible.

Diluting with river water is a sound idea but again - a bit too complicated. At what point will it be diluted enough? How to dose the water? What will happen to the process and the line when the temperature drops way below 0? Do I need sewer air/vacuum valves? All the stuff will lead to increased costs, overcomplication, and, I'm afraid, possible cloging. Either that or the filter's manufacturer scared me for no reason.

I think I will just design a concrete sediment basin, around 10 squared meters in plan. I will pump whatever comes out at the other end of the basin. when it comes to cleaning it I think even an escavator will do fine. I will use standard sediment basin equations - they make sense and while I cannot predict what particles I will encounter in the water, I'm still able to define that my flow velocity in the sediment basin will be low enough to allow for sedimentation of even clay and silt particles. It has to be good enough.

My OP should say 20mg/l of suspended particles. Which leads to my last problem - how big should the sediment tank be in order to provide a reasonable retention for the sludge so they won't need to clean it too often. Gonna have to think about that.

 

[quark]

0.6 ton per 5 cu.mtr is about 14% solid concentration and I am not sure you will be able to get it straight from back wash. Have you checked the option of centrifugation or belt press? Belt Presses can give you up to 20% drip free sludge or more in your case as my experience is with 5% solid concentration.

 

[miningman]

What is the approx analysis of the sludge?? Organic matter and / or heavy metal contaminants.?? Some minesites will take material like this for revegetating waste dumps. They dont really care about the metals because the dumps already contain appreciable quantities of heavy metals. If there is a local source of sewage sludge , your material can be mixed in and applied to the rock dumps to support growth.

 

[itsmoked]

Poland.. didn't realize it was that rainy.

Never-the-less you can still do the same thing, you just do it under a pole roof preferably a clear roof like clear corrugated fiberglass to let heat in.

1/2 a ton a day...

Our sewer plant, 60,000 people, took its sludge out every day in a dump truck and dumped it in the adjacent marshy area. It was dry enough to sit in a pile not a muddy cow-pie situation.

The sludge de-watered itself and dried out fairly quickly leaving a black-ish dumped mound. Eventually they hauled it to the city landfill where they use it for over-top.

The biggest problem was tomatoes and pot. Both are unharmed in the sewer process and they'd sprout out of the piles. You should not have this problem.

So, if your stuff is soupy then you should indeed dump it on concrete and let it dewater. Then skip-loader it out to a field and in an orderly pattern, pile it. I suspect your residue would be well received by farmers and people needing fill because yours won't have the nasty stuff sewage would.

You might need two separate slabs to give enough time for dewatering.

If you want to avoid the slabs you need to run the stuff thru a rotating screen de-watering process. I've seen them elevated so ultimately a dump truck can drive up under it and pull a lever. Then go straight to the field piles with it.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[TomaszKruk]

Thanks for all the responses guys. I will have to think about what to do.

The sludge will be from filtering river water.

 

[ashtree]

I assume your measurement is 20mg/l not 20mg/ml.
If you are just pumping it why are you needing to filter it at all.
A couple of other points.
Unless this is really coarse stuff that you are pulling up off the bottom 20mg/L is unlikely to settle out unless coagulated and flocculated with a coagulant. Noramlly when a river only contains 20mg/l of SS most things that will settle out have already. Therefore there is no riusk of this settling in the bottom of the pumpwell. Likewise unless you have a pretty fine mesh on your conical filter you won't filter it out to a significant degree either. That finne mesh is going to need a lot of backwashing or a lot of surface area to not be an annoyance.

So go back to my original question, do yoiu really need to filter it at all.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[TomaszKruk]

The line will be long (60 km). We are affraid that contaminations present in the water will start to accumulate on the walls in form of sediments (or whatever the proper word is - the physical residue that always appears on older lines but can be very severe sometimes) or aid the growth of bacteria.

We've decided that every little bit helps since the situation is difficult.

In theory it will be long after the design process ends. Long after any contractor's guarantees will expire even. Still the filtration is max of what we can do in the water treatment department and, since still rational, we've decided to go for it.

From what I see I will have to get more into the physical and chemical composition of water itself and determine if there are any surprises there.

Where it comes to if it's legal to store it in form of piles I would say it will prove to not be so. But again - thanks for the input because I've assumed it impossible, and did not analize further.

 

[itsmoked]

Well that's a bit of a different animal.

Perhaps you can make sure the design is capable of being pigged. Then pig it yearly or whatever is deemed reasonable.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[TomaszKruk]

I don't like it but PIG will not happen. First of all there's some reported history of them getting stuck in lines of this kind (cannot comfirm it, don't know if it's a question of bad engineering practice - that's what I've been told). If something like that happens on one of our HDD sections - it would be a disaster.

What I've learned while conversing with other people - PIGs are readly used for oil and gas pipelines, but have bad reputation when it comes to water, especially not meticulously cleaned one.

Second - it would further complicate right of way aquisition. That everyone could live with, but still - it makes it harder to revisit a decision once made.

So far the best approach the hive mind came up with is to oversize the pipe and filter the water. Pump calculations were carried using highest aplicable roughness for Darcy-Weisbach.

 

[IRstuff]

Can you actually predict the amount of slime deposited over the lifetime of the pipeline?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[ashtree]

"Slime" will largely come from biological activity and a cone filter alone will not eliminate this.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"