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Reduction of industrial sewage sludge by biological and biochemical agents

Identification

Key words waste, sewage, sludge, meat, dairy, slaughterhouses, encapsulation, surfactant, eco-innovation, waste water treatment plants (WWTP)
Latest version 2012/02/28
Completed by IRTA

How does it work?

Primary objective To reduce the large amounts of sewage sludge generated in industrial biological waste water treatment plants (WWTP).
Working principle There are different methods to reduce industrial sewage sludge, the ones that focus on reducing sludges once are generated (disintegration processes) and the ones based on the prevention principle (effect on the metabolism of the microorganisms, thus reducing biomass generation).

To date there are different commercial products to affect the metabolism of the microorganisms and reduce the sewage sludge in a WWTP:

  • Biologic agents as folic acid, f.i. DOSFOLAT® XS: used since 1983, but due to the increasing price of folic acid, its use has decreased in last years
  • Biochemical surfactants as LIPISOL: tested by the company Bioserve GmbH till 2004. Reductions from 20% to 37% were reported (2,3)
  • Biological and biochemical agents as LODOred (1), mainly for meat, dairy and slaughterhouses WWTPs

Activated sludge is a process for treating sewage and industrial wastewaters using air and a biological floc composed of bacteria and protozoans. An agent with a biological and biochemical effect consist of an aqueous preparation with a mixture of vitamins, enzyme stabilisers and substances; once added to the activated sludge, it enwraps microorganisms and leads to the formation of compact activated sludge flocs (Fig. 1). These flocs may also incorporate small suspended mineral particles leading to an increase of floc density, thus improving the sedimentability.

Floculation proceeds as follows: 1) the aqueous preparation encapsulates the microorganisms; 2) highly selective membrane coatings are created, which works in the same way as membrane bioreactor systems; 3) auxiliary substances facilitate the mass transfer into and out of the flocs, improving degradation efficiency.

2 2 3 wastered.jpg

Fig. 1 Encapsulation of microorganisms by means of LODOred. (© WASTEred)
The aqueous preparation affects the metabolism of the microorganisms, so that their initial anabolism activity (creation of new cell mass) turns into catabolism, generating additional energy to supply the intensified microbial degradation activity. As a result, fewer microorganisms are needed to delete the same organic load and there is a drastic reduction of surplus sludge production (up to 35%) after 4 to 6 weeks of application.

Images
Additional effects
  • Improved effluent quality (e.g. BOD- Biochemical oxygen demand, COD- Chemical oxygen demand, N, P, suspended particles, etc.), reducing eutrophication at the surface of the receiving water bodies (lakes and rivers)
  • Improved dewaterability: reduced polymer consumption (up to 25%), less time for sludge dewatering required and increased equipment lifetime
  • Lower disposal costs
  • Lower energy consumption (reduction by 25%)
  • Lower ecological footprint of the complete wastewater treatment process
  • Lower associated costs (sludge dewatering, transport and disposal; pollution fees). Disposal costs are reduced by one third
Important process parameters BOD, COD and pH (sewage), polymer for sludge dewatering, dose of the commercial product, temperature
Important product parameters

What can it be used for?

Products WWTP sewages
Operations Encapsulation, stabilising, dewatering
Solutions for short comings Potential needs:
  • To reduce the large amounts of sewage sludge generated in industry
  • Improve ecological footprint of industrial systems

What can it NOT be used for?

Products -
Operations The aqueous preparation, acting in a biological and biochemical level, is only suited for municipal and industrial biological WWTPs without anaerobic digestion.

LIPISOL has been tested from 2002 till 2004, only in municipal WWTP.

Other limitations In case of microbiological contamination of the product, due to wrong manipulation, the product efficiency could be affected.
Risks or hazards LODOred is a non-hazardous, non-toxic and fully biodegradable product. It is not classified as a dangerous preparation according to the EU standards (Commission Directive 2001/60/EC).

LIPISOL is a biodegradable product, even in anaerobic conditions (4).

Implementation

Maturity The aqueous preparation, marketed as LODOred-100k, has been tested since 2005. Application in industrial plants in Spain, Germany and Poland has resulted in sludge reduction ranging from 10 to 35%.

LIPISOL wast tested in two german municipal WWTPs (Neuss and Moosburg) from 2002 to 2004. Results on its technical and economical revenue can be found in the IWB- Institut für Wasser und Boden e. V. survey report (4).

Modularity /Implementation LODOred is sold in containers or canisters as a liquid concentrate, to be dosed in the biological reactor. In some cases (small sewage works) it might need to be diluted in potable water previously.

It only needs a simple dosing pump to be installed and a storage reservoir. LIPISOL needs to be mixed with water. Concentration depends in each case study. Estimated dosis can be found in the IWB survey report (4), p.45.

Consumer aspects Lower ecological footprint processes are socially well accepted.
Legal aspects
  • Directive 91/271/EC concerning urban waste-water treatment
  • Directive 86/278/EC concerning the application of sludge from wastewater treatment plants
Environmental aspects
  • Reduction of surplus sludge
  • Reduction of chemical polymer
  • Reduction of energy consumption for sludge handling, dewatering, drying, transport for disposal and burning (through incineration)
  • Enhancing of water quality of effluents
  • Reduction of air pollution (transport for disposal decreases and less sludge needs to be incinerated)

Further Information

Institutes TTZ, Institut für Wasser und Boden
Companies Bioazul, COVAP, Bioserve, Polyoxetane
References 1. http://www.wastered.eu/

2. http://www.bioserve.info/Studien-u-ErfahrungsBerichte/Tenside-reduzieren-Ueberschussschlamm-53223

3. http://www.bioserve.info/Studien-u-ErfahrungsBerichte/St

4. Gutachten über einen ganzheitlichen Optimierungsansatz zur Leistungssteigerung der Abwasserbehandlung bei gleichzeitiger Kosteneinsparung am Beispiel der Kläranlage Moosburg A.D. isar, 2007. IWB- Institut für Wasser und Boden e. V.



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Created by Hte irta on 28 February 2012, at 08:56