sludge drying beds 1 dorothee spuhler, seecon gmbh

Sludge Drying Beds

Sludge Drying Beds

1

Dorothee Spuhler, seecon gmbh

Sludge Drying Beds

Find this presentation and more on: www.sswm.info.

Copy it, adapt it, use it – but acknowledge the source!Copyright

Included in the SSWM Toolbox are materials from various organisations and sources. Those materials are open source. Following the open-source concept for capacity building and non-profit use, copying and adapting is allowed provided proper acknowledgement of the source is made (see below). The publication of these materials in the SSWM Toolbox does not alter any existing copyrights. Material published in the SSWM Toolbox for the first time follows the same open-source concept, with all rights remaining with the original authors or producing organisations.

To view an official copy of the the Creative Commons Attribution Works 3.0 Unported License we build upon, visit http://creativecommons.org/licenses/by/3.0. This agreement officially states that:

You are free to: • Share - to copy, distribute and transmit this document • Remix - to adapt this document. We would appreciate receiving a copy of any changes that you have made to improve

this document.

Under the following conditions: • Attribution: You must always give the original authors or publishing agencies credit for the document or picture you are

using.

Disclaimer

The contents of the SSWM Toolbox reflect the opinions of the respective authors and not necessarily the official opinion of the funding or supporting partner organisations.

Depending on the initial situations and respective local circumstances, there is no guarantee that single measures described in the toolbox will make the local water and sanitation system more sustainable. The main aim of the SSWM Toolbox is to be a reference tool to provide ideas for improving the local water and sanitation situation in a sustainable manner. Results depend largely on the respective situation and the implementation and combination of the measures described. An in-depth analysis of respective advantages and disadvantages and the suitability of the measure is necessary in every single case. We do not assume any responsibility for and make no warranty with respect to the results that may be obtained from the use of the information provided.

Copyright & Disclaimer

Sludge Drying Beds


3

Contents

1. Concept

2. How can Drying Beds Optimise SSWM

3. Design Principals

4. Treatment Efficiency

5. Operation and Maintenance

6. Applicability

7. Pros’ and Cons’

8. References

Sludge Drying Beds


4

Background

1. Concept

All organic degradation process produce sludge. (SASSE 1998)

Sludge has a total solid content of 2 to 10 % and can not be transported easily with simple equipment. (SASSE 1998)

Apart from this, sludge is contaminated and occupies large volumes for storage. (SASSE 1998)

Therefore it is better to dry or sludge (dewatering) before further use or dumping. (SASSE 1998)

Anaerobic sanitation systems (e.g. latrines, septic tanks, aqua privies, anaerobic baffled reactors, biogas reactors) produce less sludge than aerobic treatments (e.g. from trickling filters, activated sludge) and anaerobic sludge also dries better and results in less odour as it is more stabilised.

Sludge Drying Beds


5

What is a Sludge Drying Bed ?

1. Concept

Sludge drying beds are one of the simplest and oldest techniques for sludge dewatering. (SANIMAS 2005)

They are impermeable beds filled with different layers of gravel and sand.Draining pipes are in incorporated in the bottom of the beds.Sludge is applied in layers on the top gravel beds.Drying is achieved by evaporation and gravity percolation. In planted drynge bed, the removal of humidity is enhanced by evapotranspiration.Dried sludge is not stabilised, but additional composting (e.g. co-composting) will allow to recycle nutrients and organic matter into agriculture.The effluent (percolate) that is collected in the drainage pipes must be treated correctly.

Sludge Drying Beds


6


1. Concept

Fertiliser for agriculture

Sludge drying beds

Faecal Sludge

Septic tank

Aqua priviy

Latrines

Biogas plants

gasmanholes

inflow

scum outflow

sludge

sedimentation inoculation of fresh wastewater with active sludge final settler

Anaerobic baffled reactor

Trickling filtersCo-composting

Conveyance

Source: adapted from EAWAG/SANDC (2008); TILLEY et al. (2008); WAaF (2002 ); SANIMAS (2005); BALASUBRAMANIYAM (2008); www.Clker.com and http://whrefresh.com/wp-content/uploads/2010/01/potato_field.jpg [Accessed: 10.06.2010]

Sludge Drying Beds


7

The Role of Sludge Drying Bed in Faecal Sludge Management

1. Concept

Source: STRAUSS & MONTANGERO (2002) Source: STRAUSS & MONTANEGRO 2004

Sludge Drying Beds


8


1. Concept

Sludge drying beds can be •Unplanted •Planted

Unplanted sludge drying beds•Design similar to unplanted filters sand/gravel filters•Require desludging after every cycle of drying (manpower

required)Planted sludge drying beds

•Design similar to reed beds or vertical constructed wetlands•Do not need desludging after every cycle: (STRAUSS & MONTANGERO 2002; SASSE

1998; TILLEY et al. 2008)

◦ Porosity is maintained by the root systems of the plants.◦ Sludge is transformed into biomass (plants) and can be

harvested.

Source: STRAUSS & MONTANEGRO 2004

Planted Unplanted

Sludge Drying Beds


9

Examples: Unplanted Drying Bed

1. Concept

Source: SASSE (1998)

Sludge Drying Beds


10

Examples: Planted Drying Bed

1. Concept

Source: TILLEY et al. (2008)

Sludge Drying Beds


11

Examples

1. Concept

Unplanted drying bed at a waste

stabil- isation pond (WSP) site in

Colombia. Source: IRC (2004)

Source: EAWAG/SANDC (2008)

Unplanted drying beds in Ghana (Sandec)

Covered sludge

drying bed at the Arcata

wastewater treatment

plant (USA)http://www.humboldt.edu/arcatamarsh/compost.html

Sludge Drying Beds


12

Examples

1. Concept

Source: EAWAG/SANDC (2008)

New installation of a constructed wetland with ventilation pipes at the Asian Institute of Technology (AIT) in Bangkok, ThailandPrimary sludge drying

bed and reed bed (in the background).

Source: MUENCH, E.,von 2009)

Sludge Drying Beds


13

2. How it can optimize SSWM

Faecal sludge collected from on-site sanitation installations are commonly dumped untreated, because it is difficult to transport and treatment facilities lye often far away or are not available at all.

This causes heavy environmental pollution and major risk for the transmittance of diseases.

Sludge drying beds are a simple mean to reduce the volume of the sludge and prepare them for co-composing, which transform them to a safe and valuable fertiliser.

Indiscriminate disposal of faecal sludge, Ouagadougou. (Photo: Eawag/Sandec)

Lettuce farm fertilised with compost at Gyenyasi farmers

association in Kumasi.

Source: ERIKSEN-HAMEL & DANSO (2002)

Source: EAWAG/SANDEC (2008)

Sludge Drying Beds


14

Basics


Treatment objective:Separation of solid from the liquid fraction of faecal

sludge.Similar treatment options: sedimentation/thickening pondsPre-treatments: Latrines, septic tanks, aqua privies, anaerobic baffled reactors, biogas reactors, trickling filters, activated sludge, etc.Post-treatment: Co-composting in order to transform it into fertiliserMain-components:

•Impermeable shallow pond•Drainage pipes in the bottom (perforated PVC pipes or

hollow blocks)•Different layers of coarse gravel, gravel, sand•Slightly sloped surface for drainage (1:20) (STRAUSS & MONTANEGRO 2004)

Sludge Drying Beds


15

Unplanted Sludge Drying Bed


Sourc

e:

STR

AU

SS

& M

ON

TA

NEG

RO

(2

00

4)

Sludge application depth: about 20 cm (STRAUSS & MONTANGERO 2002; WSP 2007)

Loadings: 100 to 200 KgTS/m2/year (STRAUSS & MONTANGERO 2002)

Percolation: 50 to 80 % of initial Volume (STRAUSS & MONTANGERO 2002)

Time required for drying: 10 to 20 days (STRAUSS & MONTANGERO 2002)

Achieved drying: 40 to 70 % TS (STRAUSS & MONTANGERO 2002)

Land requirements: 0.05 m2 per capita for a 10 days cycle (STRAUSS &

MONTANGERO 2002)

Drainage

Sludge

Percolate

Sludge Drying Beds


16


Sourc

e:

STR

AU

SS

& M

ON

TA

NEG

RO

(2

00

4)

Drainage

SludgeFilter bed (EAWAG/SANDEC 2008)

Large gravel (d=20mm): 25 cmFine gravel (d=5mm): 25 cmSand: 10 cm

Sludge application depth: about 20 cm (STRAUSS & MONTANGERO 2002 WSP 2007)

Loadings: 250 KgTS/m2/year (STRAUSS & MONTANGERO 2002)

Percolation: 50 to 80 % of initial Volume (STRAUSS & MONTANGERO 2002)

Application: Once a week; Desludging: every 5 to 6 years (STRAUSS &

MONTANGERO 2002

Achieved drying: 40 to 70 % TS (STRAUSS & MONTANGERO 2002)

Planted Sludge Drying Bed

Sludge Drying Beds


17

Treatment Efficiency (STRAUSS & MONTAGERO 2002)


Suspended solids: >= 95 %COD 70 to 90 %Helminth eggs 100 %NH4 40 to 60 %

Dewatered sludge is still infectious; Additional composting of dried sludge in heaps or wind-rows will further stabilise recycled organic materials. (SANIMAS 2005)

A splash spate should be used for application of the sludge.In the case of unplanted beds, sludge must be removed frequently.Checking of drainage capacities.

Health aspects

Operation and Maintenance

Sludge Drying Beds


18

6. Applicability

Any kind of sludge can be treated in drying beds.

It is best combined with co-composting in order to produce fertiliser.

The method is simple but requires professional design and trained manpower for the operation.

However, large land areas are required for the construction.

Drying beds are centralised treatment options and thus adapted for larger areas. The operation and maintenance requires an efficient community organization.

As odour could be an issue, they should be constructed far away from households.

The bottom needs to be sealed to prevent groundwater pollution and the percolate must be treated.

Therefore, drying beds are not adapted for areas prone to flooding.

At places with frequent rain must be roofed.

Sludge Drying Beds


19

7. Pros’ and Cons’

Advantages:

• Easy to operate

• Dried sludge can be composted and used as fertiliser

• Simple operation, no skilled personnel required

• Results in much reduced volume of sludge

• Can achieve pathogen removal

• Can be built with local materials

Disadvantages:

• Requires large land area

• Re-use or treatment of seepage water required

• Only applicable during dry seasons or needs a roof

• Manual labour or specialised equipment is required to remove dried sludge from beds

• Can cause odour problems

Sources: adapted form SANIMAS (2005); http://www.training.gpa.unep.org/content.html?id=215&ln=6 [Accessed: 10.07.2010]

Sludge Drying Beds


20

8. References

BALASUBRAMANIYAM, U., ZISENGWE, L.S., MERIGGI, N., BUYSMAN, E. (2008): Biogas Production in Climates with long cold Winters. Wageningen: Wageningen University Available at: http://www.wecf.eu/english/publications/2008/biogas-coldclimates.php [Accessed: 20.04.2010]

EAWAG/SANDEC (2008): Fecal Sludge Management. Lecture notes. (=Sandec Training Tool 1.0, Module 5). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC)

EAWAG/SANDEC (2008): Fecal Sludge Management. Presentation. (=Sandec Training Tool 1.0, Module 5). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC)

ERIKSEN-HAMEL, N.S., DANSO, G. (2008): Urban Compost: A Socio-economic and Agronomic Evaluation in Kumasi, Ghana in REDWOOD, M. (ed) (2008): Agriculture in Urban Planning: Generating Livelihoods and Food Security. Earthscan/IDRC. Available at: http://www.idrc.ca/en/ev-135127-201-1-DO_TOPIC.html

SANIMAS (2005): Informed Choice Catalogue. PPT-Presentation. remen Overseas Research and Development Agency (BORDA) and United States Agency for International Development (USAID)

SASSE, L. (1998): DEWATS Decentralised Wastewater Treatment in Developing Countries. Bremen: Bremen Overseas Research and Development Association (BORDA) Available at: http://www.borda-net.org/modules/wfdownloads/uploads/062%20BORDA_Dewats-Handbook.pdf [Accessed: 27.05.2010]

STRAUSS, M., MONTANEGRO, A. (2002): FS Management – Review of Practices, Problems and Initiatives. London and Duebendorf: DFID Project R8056, Capacity Building for Effective Decentralised Wastewater Management, Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). Available at: http://www.eawag.ch/organisation/abteilungen/sandec/schwerpunkte/ewm/fsm/index_EN [Accessed: 10.06.2010]

STRAUSS, M., MONTANEGRO, A. (2004): Fecal Sludge Treatment, Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). Available at: http://www.eawag.ch/organisation/abteilungen/sandec/schwerpunkte/ewm/fsm/index_EN [Accessed: 10.06.2010]

TILLEY, E., LUETHI, C., MOREL, A., ZURBRUEGG, C., SCHERTENLEIB, R. (2008): Compendium of Sanitation Systems and Technologies. Duebendorf and Geneva: Swiss Federal Institute of Aquatic Science (EAWAG) & Water Supply and Sanitation Collaborative Council (WSSCC) Available at: http://www.eawag.ch/organisation/abteilungen/sandec/publikationen/compendium_e/index_EN Accessed: 09.04.2010]

WAaF (2002) Sanitation Technology Options. Pretoria: Department of Water Affairs and Forestry (WAaF) Available at: http://www.bvsde.paho.org/bvsacd/cd66/Technical.pdf [Accessed: 27.05.2010]

Sludge Drying Beds


2121

Main Funding Partners:

Further Funding, Content & Dissemination Partners

Compiled by:

“Linking up Sustainable Sanitation

and Water Management”

Sludge Drying Beds 22

“Linking up Sustainable Sanitation, Water Management & Agriculture”

SSWM is an initiative supported by:

Compiled by:

sludge drying beds 1 dorothee spuhler, seecon gmbh

Documents

sswm toolbox

sludge dewatering

open source

open source concept

opensource concept

respective authors

respective situation

official copy