Leach Fields
Robert Gensch, Xavier University
Leach Fields
1
Find this presentation and more on: www.sswm.info.
Copyright & Disclaimer
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 opensource 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.
Leach Fields
Find this presentation and more on: www.sswm.info.
Contents
1. Concept
2. How it can optimize SSWM
3. Design principals
4. Treatment
5. Operation and maintenance
6. Applicability
7. Advantages and disadvantages
8. References
Leach Fields
3
Find this presentation and more on: www.sswm.info.
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 waterbased 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)
Leach Fields
4
Find this presentation and more on: www.sswm.info.
1. Concept
Concept and functional design of a leach field Source: TILLEY et al. (2008)
Leach Fields
5
Find this presentation and more on: www.sswm.info.
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
Leach Fields
6
Find this presentation and more on: www.sswm.info.
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: 20.01.2010]
Leach Fields
7
Find this presentation and more on: www.sswm.info.
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)
Leach Fields
8
Find this presentation and more on: www.sswm.info.
3. Design Principles
Example
Leach field pipes Source: G. Mauk
Leach Fields
9
Find this presentation and more on: www.sswm.info.
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.
Leach Fields
10
Find this presentation and more on: www.sswm.info.
5. Operation and Maintenance
• A leach field will become clogged over time, although with a wellfunctioning 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)
Leach Fields
11
Find this presentation and more on: www.sswm.info.
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)
Leach Fields
12
Find this presentation and more on: www.sswm.info.
7. Advantages and Disadvantages
Advantages:
Disadvantages:
• Can be used for combined
treatment of greywater,
stormwater and wastewater (after
a primary treatment comprising a
settling unit: e.g septic tank)
•Requires experts for design and
construction
• 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
•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)
(TILLEY et al. 2008)
Leach Fields
13
Find this presentation and more on: www.sswm.info.
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)
Leach Fields
14
“Linking up Sustainable Sanitation,
Water Management & Agriculture”
SSWM is an initiative
supported by:
Compiled by:
Leach Fields
15