1. Robert Gensch, Xavier University
Leach Fields
Robert Gensch, Xavier University

2. Copy it, adapt it, use it – but acknowledge the source!
Copyright & Disclaimer
Copy it, adapt it, use it – but acknowledge the source!
Copyright
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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.

3. How it can optimize SSWM Design principals Treatment
Contents
Concept
How it can optimize SSWM
Design principals
Treatment
Operation and maintenance
Applicability
Advantages and disadvantages
References 3

4. 1. Concept
If there is no intention or no need to reuse wastewater or greywater, leach fields can offer an opportunity for a partial secondary treatment and a safe way of discharging it to the environment and therewith recharging groundwater bodies.
A leach field is a network of perforated pipes that are laid in underground gravel-filled trenches to dissipate effluent from a water- based collection and storage/treatment facility (e.g. septic tank). (TILLEY et al. 2008)
It allows for a further treatment of the effluent and to recharge groundwater bodies.
Concept and functional design of a leach field Source: TILLEY et al. (2008) 4

5. 1. Concept
Concept and functional design of a leach field Source: TILLEY et al. (2008) 5

6. 2. How can it optimize SSWM
Implementation and use of Leach Field can help in optimizing your local water management and sanitation system and make it more sustainable by:
Allowing for a partial treatment of wastewater and greywater
Offering an option for safe discharge into the groundwater
Allowing for a controlled disposal of water into the environment 6

7. 3. Design Principles Why reuse? (Sample subtitle)
The overflow effluent from the septic tank is fed into a distribution box, which directs the flow into several parallel channels. (TILLEY et al. 2008)
Either, a small dosing system releases the pressurized effluent into the leach field on a timer or the water flows continuously by gravity.
If the distribution is by a gravity, the slope must be sufficient until the end of each leaching line in order to assure a good drainage.
Functional design of a leach field Source: http-//geoscape.nrcan.gc.ca/h2o/bowen/images/septic_e.jpg. [Accessed: ] 7

8. 3. Design Principles Why reuse?
Each trench is 0.3 to 1.5m deep and 0.3 to 1m wide.
The bottom of each trench is filled with about 15cm of clean rock and a perforated distribution pipe is laid overtop.
More rock covers the pipe so that it is completely surrounded.
The layer of rock is covered with a layer of geotextile fabric to prevent small particles from plugging the pipe.
A final layer of sand and/or topsoil covers the fabric and fills the trench to the ground level.
The pipe should be placed 15cm from the surface to prevent effluent from surfacing.
The trenches should be dug no longer than 20m in length at least 1 to 2m apart.
(TILLEY et al. 2008) 8

9. 3. Design Principles
Example
Leach field pipes Source: G. Mauk 9

10. 4. Treatment
The wastewater effluent is absorbed by soil particles and moves both horizontally and vertically through the soil pores.
The dissolved organic material in the effluent is removed by bacteria living in the top ten feet of the soil.
The wastewater generally percolates downward through soil and eventually enters a groundwater aquifer.
A portion of the wastewater moves upwards by capillary action and either evaporates at the surface or is taken up by plants. 10

11. 5. Operation and Maintenance
A leach field will become clogged over time, although with a well- functioning pre-treatment technology, this should take many years.
It should require minimal maintenance, however if the system stops working efficiently, the pipes should be cleaned and/or removed and replaced.
To maintain and protect the leach field, deep rooteing plants or trees should not been planted above it. Also traffic, which may crush the pipes or compact the soil should be avoided.
(TILLEY et al. 2008) 11

12. 6. Applicability
Leach fields require a large area and soil with good absorptive capacity to effectively dissipate the effluent.
To prevent contamination, a leach field should be located 30 m away from a drinking water supply.
Leach fields are not appropriate for dense urban areas.
They can be used in almost every temperature, although there may be problems with pooling effluent in areas where the ground freezes.
Trees and deep-rooted plants should be kept away from the leach field as they can crack and disturb the tile bed.
(TILLEY et al. 2008) 12

13. 7. Advantages and Disadvantages
Can be used for combined treatment of greywater, stormwater and wastewater (after a primary treatment comprising a settling unit: e.g septic tank)
Can be used in almost all climates (not when the ground freezes)
Has a lifespan of 20 years or more (depending on conditions)
Low to moderate capital cost
Low operating cost
(TILLEY et al. 2008)
Disadvantages:
Requires experts for design and construction
Requires large area (on a per person basis)
Not all parts and materials may be available locally
Pre-treatment is required to prevent clogging
May negatively affect soil and groundwater properties
(TILLEY et al. 2008) 13

14. 8. References
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) 14

15. “Linking up Sustainable Sanitation, Water Management & Agriculture”
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