[Sdpg] The Overstory #99--Greywater for Trees and Landscape

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Overstory #99 - Greywater for Trees and Landscape

by Art Ludwig

Contents:

: WHAT IS GREYWATER?
: WHY USE GREYWATER?
: MULCH BASINS
: SELECTING PLANTS FOR GREYWATER TREATMENT/DISPOSAL
: SELECTING PLANTS FOR GREYWATER REUSE
: EXAMPLES OF PLANTS FOR GREYWATER REUSE
: WHEN NOT TO USE GREYWATER
: HEALTH CONSIDERATIONS CONCERNING GREYWATER USE
: NOTE ON HEALTH RISKS
: CAUTIONS FROM THE AUTHOR
: REFERENCES
: ABOUT THE AUTHOR
: WEB LINKS
: RELATED EDITIONS OF THE OVERSTORY
: PUBLISHER NOTES


This edition of The Overstory introduces some practical ways to use water
from homes (from dishes, laundry, bathing, etc., NOT from toilets) as
irrigation water for trees and landscapes. Rather than contaminate usable
water by combining it with sewage, greywater systems keep dish and wash
water separate from sewage and reuse it in the landscape. This is a classic
means of "turning waste into a resource." This article is adapted from
three publications by special guest author Art Ludwig, and introduces some
of the practical concepts behind greywater reuse. For specific design and
installation details for greywater systems, further study of the original
publications is highly recommended.


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WHAT IS GREYWATER?

Any water that has been used in the home, except water from toilets, is
called greywater. Dish, shower, sink and laundry water comprise
approximately 80% of residential "wastewater." This may be reused for other
purposes, especially landscape irrigation. Toilet-flush water is called
blackwater. Contaminated greywater or wastewater that is difficult to
handle, such as solids-laden kitchen sink water or water used to launder
diapers, is sometimes called "dark grey" or blackwater. Reclaimed water
(highly treated municipal greywater and blackwater, usually piped to
large-volume users such as golf courses in a separate distribution system)
is outside the scope of this article.


WHY USE GREYWATER?

It's a waste to irrigate with great quantities of drinking water when
plants would thrive on used water containing small bits of organic matter.
Unlike a lot of ecological stopgap measures, greywater use is a part of the
fundamental solution to many ecological problems and will probably remain
essentially unchanged in the distant future. The benefits of greywater
recycling include:

--Lower fresh water use
Greywater can replace fresh water in many instances, saving money and
increasing the effective water supply in regions where irrigation is
needed. Residential water use is almost evenly split between indoor and
outdoor. All except toilet water could be recycled outdoors, achieving the
same result with significantly less water diverted from nature.

--Less strain on septic tank or treatment plant
Greywater use greatly extends the useful life and capacity of septic
systems. For municipal treatment systems, decreased water flow generally
means higher treatment effectiveness and lower costs.

--Highly effective purification
Greywater is purified to a spectacularly high degree in the upper, most
biologically active region of the soil (Center for Study of Federalism
1972). This protects the quality of natural surface and ground waters.

--Site unsuitable for a septic tank
For sites with slow soil percolation or other problems, greywater use may
be a good alternative to a very costly, over-engineered system.

--Less energy and chemical use
Less energy and chemicals are used due to the reduced amount of both
freshwater and wastewater that needs pumping and treatment. For those
providing their own water or electricity, the advantage of a reduced burden
on the infrastructure is felt directly. Also, treating your wastewater in
the soil under your own fruit trees definitely encourages you to dump less
toxic chemicals down in the drain.

--Groundwater recharge
Greywater application in excess of plant needs recharges groundwater.

--Plant growth
Greywater enables a landscape to flourish where water may not otherwise be
available to support much plant growth.

--Reclamation of otherwise wasted nutrients
Loss of nutrients through wastewater disposal in rivers or oceans is a
subtle, but highly significant, form of erosion. Reclaiming nutrients in
greywater helps to maintain the fertility of the land.

--Increased awareness of and sensitivity to natural cycles
Greywater use yields the satisfaction of taking responsibility for the wise
husbandry of an important resource.

--Just because
Greywater is relatively harmless and great fun to experiment with.
Moreover, life with alternative waste treatment can be less expensive and
more interesting.


MULCH BASINS

If I had just two words to contribute to improve the world's handling of
greywater they would be "mulch basin." Mulch covers the greywater and
provides many other benefits.

The basin contains the water where it is needed and prevents it from
escaping where it is wasted or a nuisance. The island in the middle of the
mulch basin protects the delicate root crown from wet conditions and
possible disease.

Mulch basins are a common feature of existing horticultural practice and
could hardly be simpler to make and maintain. Don't let this fool you.
Though nature takes care of their inner workings, these are fantastically
complex biologically, far more complex than a municipal sewage treatment
plant.

What's more, the treatment level mulch basins provide is far higher than
that of a municipal treatment plant (Los Angeles Department of Water
Reclamation) and instead of consuming copious electricity and chemicals to
create polluted natural waters and piles of toxic sludge (Wagner and Laniox
1958) mulch basins run on sunlight and yield drinkable groundwater and
fresh fruit.


SELECTING PLANTS FOR GREYWATER TREATMENT/DISPOSAL

For disposal, theoretically you don't even need plants; the bacteria on the
soil particles will take care of treatment by themselves (as in a sand
filter). However, you can only do better with plants. With high perk soil
groundwater contamination could occur if wastewater moves through too fast.
With very low perk soil ponding and anaerobic conditions can occur. Plants
improve physical soil conditions including perk rate, and add their own
substantial contribution to getting rid of the water by transpiring it. The
ideal plants for greywater disposal are:

* Tolerant of wet conditions

* Generate their own mulch or physical barrier (keeps greywater from being
seen and kids or dogs from playing in it), so you don't have to

* Keep their leaves all year (so they transpire water all year)

* Look beautiful, make fruit or some other useful thing

Wetland plants also serve as solar-powered oxygen pumps. They literally
pump oxygen down through their roots, maintaining aerobic conditions in
mucky soil. These should be ideally suited for a heavily loaded disposal
basin for this reason. Also, many form such a dense stand that the need for
adding mulch is obviated; the plants themselves preclude access to the
water (if there is even the tiniest area of standing water for more than a
week or two, mosquitoes will hatch from it).


SELECTING PLANTS FOR GREYWATER REUSE

Trees are the best thing to irrigate with the branched drain system. Water
delivered anywhere in the root zone will benefit the whole plant. It is a
heck of a lot easier to hit a few big root zones than numerous small ones.
Anything smaller than a big shrub is just too small for most greywater
systems, which supply only a dozen or so outlets (as compared to hundreds
in a drip irrigation system). Even if it were possible to supply more
outlets, an inch and a half (4 cm) pipe to every flower would be a lot of
plastic.

If your fruit trees are already planted, that's what you'll be watering. If
you have evergreen fruit trees, they are the priority. If your trees are
not planted, then you have the opportunity to optimize the coordination
between the greywater system and layout of the edible landscaping (Office
of Aridland Studies).


EXAMPLES OF PLANTS FOR GREYWATER REUSE

Bananas--Premier plant for greywater in warm climates. Make sure there is
enough basin area and plants so there is no standing water; they are not
wetland plants. Clumps will expand until they are using all available
water. If they look like they need more water, chop a few down and the rest
will do better. For maximum fruit production, each clump should have a
mature, medium and small stalk.

Citrus

Avocado and Mango--Grow into enormous trees. Make sure you have an idea of
how to water it when it is forty feet tall!

Pineapple guava--Can be maintained as a four foot hedgerow, or shaped into
a twenty foot specimen tree

Fig--No paradise is complete without figs. While deciduous, there is a
shorter interval between dropping leaves and growing new ones than for most
deciduous fruit trees.

Apple

Plum

Peach


WHEN NOT TO USE GREYWATER

There are a number of possible reasons not to use greywater or to use it
only during certain times of year:

--Insufficient space
In some situations, neighbors are too close, the yard too small or
nonexistent.

--Drain pipes impossible to get to
If all plumbing is entombed in a concrete slab, accessing most of the
greywater won't be economical.

--Unsuitable climate
In very wet climates, where using greywater for irrigation is of little
benefit, better ways to dispose of it may be available. In very cold
climates, freezing may prevent the use of a greywater system for part of
the year.

--Insufficient combined waste flow
If all greywater is reused all the time, the flow through municipal sewers
may occasionally be insufficient to move toilet solids through.

--Unsuitable soil
Soil that is extremely permeable or impermeable may preclude the use of a
greywater system or at least require special adaptations.

--Legality concerns
In most parts of the country, the legality of greywater systems is a "grey"
area. However, there seems to be a general movement toward a less paranoid
and more realistic official attitude regarding greywater recycling,
concurrent with increased experience and improved systems (not to mention
more prevalent water shortages and pollution problems) (California Plumbing
Code). Authorities generally turn a blind eye toward greywater use even
where illegal. In the 1970s, the state of California published a pamphlet
that explained the illegality of greywater use and, at the same time, how
to do it, and get a tax credit for it!

--Health concerns
The main reason greywater remains illegal in many areas is concern for
public health. However, in practice, the health threat from greywater has
proven to be insignificant. I know of no instance in which a person in the
U.S. became ill from greywater. The first actual field test by the
Department of Water Reclamation in Los Angeles found that greywatered soil
teemed with pathogens. However, the control soil did, as well. Their
conclusion: don't eat dirt, with or without greywater! (Los Angeles
Department of Water Reclamation)

--Poor cost/benefit ratio
In some situations, especially when legal requirements mandate a complex
system for a small flow of water, the ecological cost of the system may
outweigh the benefits.

--Inconvenience
So far, most greywater systems are either more expensive or require
considerably more user involvement than well functioning septic or sewer
systems.


HEALTH CONSIDERATIONS CONCERNING GREYWATER USE

Greywater may contain infectious organisms, so keep this in mind when
designing and using a system. In practice, the health risk of greywater use
has proven to be minimal. It is, after all, the water you just bathed in,
or residue from clothes you wore not long ago. At the same time, it's
definitely poor form to construct pathways for infecting people into your
design, and totally unnecessary. All greywater safety guidelines stem from
these two principles:

1)    Greywater must pass slowly through healthy topsoil for natural
purification to occur.

2)    Design your greywater system so no contact takes place before
purification.

Here are examples of applying these principles to correct possible
problems:

*   Direct contact or consumption. SOLUTION: Carefully avoid cross
connections and label greywater plumbing, including greywater garden hoses.
Use gloves when cleaning greywater filters.

*   Breathing of microorganisms. Droplets from sprinklers can evaporate to
leave harmful microorganisms suspended in the air, waiting for someone to
breathe them. SOLUTION: Don't recycle greywater through sprinklers.

*   Microorganisms on plants. Direct application to foliage can leave
untreated microorganisms on surfaces. SOLUTION: Don't apply greywater to
lawns or directly to fruits and vegetables that are eaten raw
(strawberries, lettuce, or carrots, for example). Fruit trees are
acceptable if greywater is applied only to the roots.

*   Contamination of surface water. If greywater does not percolate through
the soil, it can flow into creeks or other waterways untreated. SOLUTION:
Discharge greywater underground or into a mulch-filled basin. Don't apply
greywater to saturated soils. Apply greywater intermittently so that it
soaks in and soil can aerate between waterings. In general, contained
greywater application at least 50 feet from a creek or lake is not a
problem.

*   Contamination of groundwater. It is all but impossible to contaminate
groundwater with a greywater system. However, property owners with wells
should not irrigate with greywater any closer to the well than county
regulations allow for a septic tank leach field.

*   Chemical contamination. Biological purification does not usually remove
industrial toxins. Toxins either will be absorbed by plants or will pollute
groundwater. Many household cleaners are composed of chemicals that are
unsuitable for introduction into a biological system. SOLUTION: Don't buy
products that you wouldn't want in your greywater system. Divert water
containing those you can't avoid to poison the sewer or septic instead.

*   System overload. Greywater systems are safest when using water that is
fairly clean initially. Greywater should not contain water used to launder
soiled diapers or by anyone with an infectious disease; in both cases,
greywater should be diverted to the septic tank or sewer. Also, DON'T STORE
GREYWATER; use it immediately, before bacteria multiply. Finally, if you
are having a party where 50 people are going to use a system designed for
two, consider diverting greywater to the sewer for the night.


NOTE ON HEALTH RISKS

Much fuss has been made over the potential health risk of greywater use,
without comparison with the actual risk of the current practice of
disposing of sewage into natural waters used for swimming, drinking and
fishing. This questionable practice short circuits effective natural
purification in soil and is considered one of the least desirable
techniques by the World Health Organization (Wagner and Laniox 1958).

Approximately 20% of all U.S. communities still dump sewage in natural
waters after primary treatment (solids removal) only. After heavy rains,
even the most technologically advanced secondary treatment plants are
forced to abandon all pretense of treatment and let raw sewage flood into
the ocean or river.

Widespread greywater use in a population mostly unaccustomed to taking
responsibility for utilizing natural systems would not be 100% risk-free.
However, even with the inevitable misuses, greywater recycling as described
here is safe compared to other common activities, such as kissing, dogs
pooping on lawns, and swimming downstream of municipal sewers.


CAUTIONS FROM THE AUTHOR

The design and use of greywater systems carry legal, public health,
horticultural, and ecological consequences. The author encourages people to
follow common sense and local regulations for greywater treatment. Do not
use greywater for food crops or lawns unless you take appropriate
precautions against the possibilities of transmitting disease and
contamination from household chemicals.


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REFERENCES

California Plumbing Code, Title 24, Part 5, California Administrative Code,
Appendix J: Greywater Systems for Single Family Dwellings. Department of
Water Resources, State of California, 1020 9th Street, 3rd Floor,
Sacramento, CA 95814.

Center for the Study of Federalism. 1972. Green Land-Clean Streams: the
Beneficial Use of Waste Water Through Land Treatment. Center for the Study
of Federalism, Temple University, Philadelphia, Pennsylvania.

Los Angeles Department of Water Reclamation. "Greywater Pilot Project Final
Report." Report on first quantitative field testing of greywater health
safety. May be available from Hoover Ng, Los Angeles Department of Water
and Power, P.O. Box 111, Room 1458, Los Angeles 90051-0100.

Office of Aridland Studies, University of Arizona. Cleaners for Greywater
Systems. Office of Aridland Studies, University of Arizona, Tucson, AZ
85719.

Wagner, E. and J. Laniox. 1958 (reprinted 1971). Excreta Disposal for Rural
Areas and Small Communities. Monograph #39, The World Health Organization,
Geneva, Switzerland.


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ORIGINAL SOURCE

This edition of The Overstory was adapted with the kind permission of the
author from:

Ludwig, A. 2000. Create An Oasis With Greywater: Your Complete Guide to
Choosing, Building and Using Greywater Systems. Oasis Design, Santa
Barbara, CA, USA.

and

Ludwig, A. 2001. Branched Drain Greywater Systems: Reliable, Economical
Sanitary, Low Maintenance Distribution of Household Greywater to Downhill
Plants without Filtration or Pumping (A supplement to Create an Oasis with
Greywater). Oasis Design, Santa Barbara, CA, USA.

and

Ludwig, A. 1999. The Builder's Greywater Guide: Installation of Greywater
Systems in New Construction and Remodeling (A supplement to Create an Oasis
with Greywater). Oasis Design, Santa Barbara, CA, USA.


These publications can be ordered from: Oasis Design, 5 San Marcos Trout
Club, Santa Barbara, CA 93105-9726, USA for $17.95 each, or $42.85 for all
three, including tax & shipping, or visit the web site:
<http://www.oasisdesign.net>.


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ABOUT THE AUTHOR

Art Ludwig is an ecological systems designer. He has broken new  ground in
design of transport bicycles, gravity feed water systems, greywater and
blackwater reuse systems, composting toilets, and other areas. He developed
the first household cleaners designed to biodegrade into plant food. His
specialty is the interconnections between systems. For example, rainwater
harvesting supplies super efficient fixtures, which drain through a
greywater system to water and feed fruit trees, which in turn shade the
house in summer and let sun pass in the winter, as well as feed the
inhabitants. He currently lives and works in a 1920 summer cabin surrounded
by a food jungle in a canyon above Santa Barbara, California with his wife
two children, and a nice swimming hole. Web site:
<http://www.greywater.net>.


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WEB LINKS

Greywater Central hosted by Oasis Design has a wide range of information on
greywater systems: <http://www.greywater.net/>

A good introduction to greywater: <http://www.greywater.com>

Oasis Designs web links: <http://oasisdesign.net/links/index.htm>


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RELATED EDITIONS OF THE OVERSTORY

The Overstory #96--Sheet Mulch: Greater Plant and Soil Health with Less
Work
The Overstory #87--Urban Forestry
<http://www.agroforester.com/overstory/overstory87.html>
The Overstory #81--The Soil Foodweb: It's Role in Ecosystem Health
<http://www.agroforester.com/overstory/overstory81.html>
The Overstory #72--Microenvironments (Part 1)
<http://www.agroforester.com/overstory/overstory72.html>
The Overstory #64--Homegardens
<http://www.agroforester.com/overstory/overstory64.html>
The Overstory #46--Human Health and Agroecosystems
<http://www.agroforester.com/overstory/overstory46.html>
The Overstory #22--Pioneering Difficult Sites
<http://www.agroforester.com/overstory/overstory22.html>
The Overstory #17--Microcatchment
<http://www.agroforester.com/overstory/overstory17.html>

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PUBLISHER NOTES

Publisher: Permanent Agriculture Resources, P.O. Box 428, Holualoa, HI
96725 USA; Tel: 808-324-4427; Fax: 808-324-4129; E-mail:
<par at agroforestry.net>; Web site: <http://www.agroforestry.net>

Editors: Craig R. Elevitch and Kim M. Wilkinson

Past editions of The Overstory: <http://www.overstory.org>

This publication is Copyright 2002 Permanent Agriculture Resources.  All
rights reserved worldwide. For conditions of use please send an e-mail to
<par at agroforestry.net> or write to Permanent Agriculture Resources at the
address above.

This newsletter is designed to provide agricultural information, but is
sent with the understanding that the editors and publishers are not engaged
in rendering consultation. If expert assistance is required, the services
of a professional should be sought.

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