Wolfgang Stump Öko-control GmbH; Burgwall 13a; D 39128 Schönebeck Telephone: +49 (0)3928/42738; Fax: 42739 E-Mail: wolfgang.stump@oeko-control.com
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
1a) Natural methods of sludge dewatering Steps Treatment Effective by Individual processes 1. Step thickening gravitation continuous or discontinuous operated thickener 2. Step dewatering gravitation evaporation sludge basin sludge drying bed sludge lagoon 3. Step drying thermic forces sludge drying bed (only in warm regions)
1a) Natural methods of sludge dewatering Sludge lagoon
1a) Natural methods of sludge dewatering Sludge basins a nightmare for mobile sludge dewatering
1a) Natural methods of sludge dewatering Construction of a dry reed bed
1a) Natural methods of sludge dewatering Reed bed
1a) Natural methods of sludge dewatering Reed bed (gras)
1a) Natural methods of sludge dewatering Site clearance of a dry reed bed (reed)
1b) Artificial methods of sludge dewatering Steps Treatment Effective by Individual processes 1. Step thickening gravitation continuous or discontinuous operated thickener 2. Step dewatering static methods (Pressure differences compared to the atmosphere by low or high pressure in the machine dynamic process Gravity (artificial gravity field) static methods Vacuum filtration, Belt filter presses (Over) pressure filtration dynamic process Centrifuges / Decanters 3. Step drying Thermic forces dryers / dehydrators (any sort / type)
1b) Artificial methods of sludge dewatering Static thickener operated with moving turbid water pump or with float and suction pipe
1b) Artificial methods of sludge dewatering Sludge storage with sample line for liquid removal or connection for mobile dewatering; mobile belt filter press
1b) Artificial methods of sludge dewatering Stationary belt filter press
1b) Artificial methods of sludge dewatering Mobile Chamber Filter Press
1b) Artificial methods of sludge dewatering Filter cake from a chamber filter press
1b) Artificial methods of sludge dewatering Sludge storage and mobile decanter centrifuge with sludge storage
1b) Artificial methods of sludge dewatering Decanter centrifuge
1b) Artificial methods of sludge dewatering Stationary decanter centrifuge and sludge storage
1b) Artificial methods of sludge dewatering Sludge transport
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 process corresponds to the cycle principle - Agricultural use is a process with long-term experience on a secure legal and scientific basis - Recycling in agriculture is, in comparison to other means of disposal, a cost-efficient solution - Efficient organization and qualified service providers enable effective monitoring for low-risk agricultural recycling
2.) Necessity of (mobile) sludge dewatering 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 not available in the soil
2.) Necessity of (mobile) sludge dewatering 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, trace organic 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 and before sowing)
2.) Necessity of (mobile) sludge dewatering 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)
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
3.) Problems of the (mobile) sludge dewatering 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 require different substances
3.) Problems of the (mobile) sludge dewatering Dewatered sludge is to be recycled as soon as possible.
3.) Problems of the (mobile) sludge dewatering The sludge water (centrate, filtrate) is recycled to the wastewater treatment plant inlet and generates a high return of the plant load - sludge water has high concentrations of chemical oxygen demand, total nitrogen and 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
3.) Problems of the (mobile) sludge dewatering Concentrations in sludge water and municipal wastewater parameter sludge water minimum mg/l sludge water maximum mg/l Municipal wastewater average mg/l CSB 400 8.000 500 BSB 5 200 6.000 250 N ges 150 1.600 55 NH 4 -N 100 1.200 45 P ges 20 200 8
4.) Conclusion and Summary Sludge dewatering increases the possibilities of sludge disposal and 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
4.) Conclusion and Summary 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 in a contract - parallel provisions of the drainer and operator of the system in the dry matter content - limit the amount of daily sludge to be dewatered
4.) Conclusion and Summary Thank you for your attention and I look forward to your questions. Wolfgang Stump Öko-control GmbH Schönebeck Phone: +49 (0)3928 / 42738