09. dewatering technologies
TRANSCRIPT
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Sludge dewatering
Wolfgang StumpÖko-control GmbH; Burgwall 13a;
D – 39128 Schönebeck
Telephone: +49 (0)3928/42738; Fax: 42739E-Mail: [email protected]
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Sludge dewatering
Outline:
1) The method of sludge dewatering
1a) Natural method
1b) Artificial methods
2) Need for (mobile) sludge dewatering
3) Problems with the (mobile) sludge dewatering
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1a) Natural methods of sludge dewatering
Steps Treatment Effective by Individual processes
1. Step thickening gravitation continuous ordiscontinuous operatedthickener
2. Step dewatering gravitationevaporation
sludge basinsludge drying bed
sludge lagoon
3. Step drying thermic forces sludge drying bed(only in warm regions)
Sludge dewatering
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Sludge lagoon
Sludge dewatering1a) Natural methods of sludge dewatering
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Sludge basins
– a nightmare for mobile sludge dewatering
Sludge dewatering1a) Natural methods of sludge dewatering
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Construction of a dry reed bed
Sludge dewatering1a) Natural methods of sludge dewatering
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Reed bed
Sludge dewatering1a) Natural methods of sludge dewatering
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Sludge dewatering1a) Natural methods of sludge dewatering
Reed bed (gras)
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Site clearance of a dry reed bed (reed)
Sludge dewatering1a) Natural methods of sludge dewatering
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Steps Treatment Effective by Individual processes
1. Step thickening gravitation continuous ordiscontinuous operatedthickener
2. Step dewatering static methods(Pressure differencescompared to theatmosphere by low or highpressure in the machinedynamic processGravity (artificial gravityfield)
static methodsVacuum filtration,Belt filter presses(Over) pressurefiltrationdynamic processCentrifuges /Decanters
3. Step drying Thermic forces dryers / dehydrators(any sort / type)
Sludge dewatering1b) Artificial methods of sludge dewatering
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Static thickener – operated with moving turbid water pump or
with float and suction pipe
Sludge dewatering1b) Artificial methods of sludge dewatering
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Sludge storage with sample line for liquid removal
or connection for mobile dewatering; mobile belt filter press
Sludge dewatering1b) Artificial methods of sludge dewatering
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Stationary belt filter press
Sludge dewatering1b) Artificial methods of sludge dewatering
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Mobile Chamber Filter Press
Sludge dewatering1b) Artificial methods of sludge dewatering
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Filter cake from a chamber filter press
Sludge dewatering1b) Artificial methods of sludge dewatering
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Sludge storage and mobile decanter centrifuge with sludge storage
Sludge dewatering1b) Artificial methods of sludge dewatering
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Decanter centrifuge
Sludge dewatering1b) Artificial methods of sludge dewatering
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Stationary decanter centrifuge and sludge storage
Sludge dewatering1b) Artificial methods of sludge dewatering
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Sludge transport…
Sludge dewatering1b) Artificial methods of sludge dewatering
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2.) Necessity of (mobile) sludge dewatering
The only way for recycling of liquid sewage is the agricultural use
- Conservation of resources for society (savings of landfill space) and for agriculture(replacement of mineral fertilizers)
- Recycling of organic matter and nutrients in agriculture as recycling processcorresponds to the cycle principle
- Agricultural use is a process with long-term experience on a secure legal andscientific basis
- Recycling in agriculture is, in comparison to other means of disposal, a cost-efficientsolution
- Efficient organization and qualified service providers enable effective monitoring for
low-risk agricultural recycling
Sludge dewatering
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The only way for recycling of liquid sewage is the agricultural use
Theses against the use of sewage sludge in agriculture:
- Risk of pollutant dispersion and enrichment in the environment and in the food chain
- Significant exposure to viruses, bacteria and hormones
- Through coincineration of sewage sludge fossil resources can be replaced
- Phosphorus compounds are, by additives in wastewater treatment, often notavailable in the soil
Sludge dewatering2.) Necessity of (mobile) sludge dewatering
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The only way for recycling of liquid sewage is the agricultural use
The agricultural use is not always possible:
- High pollution load of the sewage sludge (exceedances of limits for metals, traceorganic substances)
- Acceptance problems among farmers and businesses in the food industry
- Adequate supply of nutrients in the soil - no / low fertilizer requirements
- No sewage sludge application during the growing season (just after harvest andbefore sowing)
Sludge dewatering2.) Necessity of (mobile) sludge dewatering
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Any other recycling method for sewage sludge requires a solid state
of the sludge
- Composting
- Landscaping and reclamation
- Landfilling (banned in Germany)
- Combustion (coincineration or mono incineration)
Sludge dewatering2.) Necessity of (mobile) sludge dewatering
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3.) Problems of the (mobile) sludge dewatering
Depending on the type of sludge and the wastewater and sludge
treatment sludge can be dewatered good or bad
Factors:
- dry solids, organic content- pH and organic acids- fats / lipophilic substances- sediment content, grain size- binding forms of water to the sludge flocs
Sludge dewatering
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In order to separate the sludge from the water well,flocculants – e.g. organic polymers – are added
- Flocculants to improve the separation of sludge and water
- Goal: high dry matters of the dewatered sludge and "clean"sludge water (centrate, filtrate)
- the use of flocculants must be optimized; different sewage
sludges and fluctuating characteristics of the sludge requiredifferent substances
Sludge dewatering3.) Problems of the (mobile) sludge dewatering
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Dewatered sludge is to be recycled as soon as
possible.
Sludge dewatering3.) Problems of the (mobile) sludge dewatering
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The sludge water (centrate, filtrate) is recycled to the wastewatertreatment plant inlet and generates a high return of the plant load
- sludge water has high concentrations of chemical oxygen demand, total nitrogenand ammonium nitrogen, phosphorus and suspended solids
- small WWTP often do not have the capacity of co-treatment of the sludge water
- private companies for mobile sludge dewatering are interested in a high throughput
and produce sometimes significant impact loads for the WWTP
Sludge dewatering3.) Problems of the (mobile) sludge dewatering
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Concentrations in sludge water and municipal wastewater
parameter sludge water
minimum
mg/l
sludge water
maximum
mg/l
Municipal waste-
water average
mg/l
CSB 400 8.000 500
BSB5 200 6.000 250Nges 150 1.600 55
NH4-N 100 1.200 45
Pges 20 200 8
Sludge dewatering3.) Problems of the (mobile) sludge dewatering
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Sludge dewatering increases the possibilities of sludge disposaland reduces the cost at a reasonable cost
Opportunities:- Profit from disposal of sewage sludge safety- Saving of transport costs- Reduce the amount to be disposed of
Risks
- Charge back to the wastewater treatment plant through sludge water- Cost factor for sludge dewatering
Sludge dewatering4.) Conclusion and Summary
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Notes from the field
- for smaller WWTP: Set quality criteria and dicharge load limit for sludge water
- accounting basis should be the tonnage of the dewatered sludge
- the dry solids content of the raw sludge and the dewatered sludge should be fixed ina contract
- parallel provisions of the drainer and operator of the system in the dry mattercontent
- limit the amount of daily sludge to be dewatered
Sludge dewatering4.) Conclusion and Summary
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4.) Conclusion and SummarySludge dewatering
Thank you for your attention
and I look forward to your questions.
Wolfgang StumpÖko-control GmbH Schönebeck
Phone: +49 (0)3928 / 42738