Constructed wetlands - info gleaned recently

Lawrence F. London, Jr. london at
Mon Oct 25 13:28:38 EDT 1999

From: "Myk Rushton" <permaculture at>
Subject: Constructed Wetlands/Reedbeds Revision notes
Date: Mon, 18 Oct 1999 19:58:48 +1300
Organization: Ecotech Culture

Ecotechnolgy Revision notes. General notes, abstracts, straight from
books/reports, others. No refs.

Constructed Wetlands/Reedbeds (UK)
06 october 96

Definition: A constructed wetland/reedbed (CW/R) is a designed and man made
complex of saturated substrates, emergent and submergent vegetation,
animallife, and water that simulates natural wetlands for human use and
benefit. (Constructed wetlands for wastewater treatment: Municipal,
industrial, agriculture, 1989, D.Hammer. Ed.)

In schematic form CW/R's are man made inclined floor beds (1-8%) filled with
a porous matrix in which rooted aquatic plants and microbial activity are
used as a method of effluent treatment

[Snip - Figure 1.] Schematic image showing: rooted aquatic plants; litter
layer, thermal insulation; inlet pipe, dispersed flow, inlet cambian,
crushed stones - biofilm layer; slope 1-8%; porous matrix (substrate),
Hydraulic conductivity (HC), gravel > HC, soil < HC, Impervious liner, can
be puddled, Roots and rhizomes, only large during summer, die back during
winter (temperate).

The Germans, major investors in  CW/R over the last 30 yrs both R&D,
have/had the greatest number of CW/R often very small ones for treating
leachate, domestic waste from individual houses or attached to farms. The US
also has CW/R systems particularly the southern states (Florida) where they
have a longer growing season. The plant root systems are active for a longer
period of the year.

In the UK there are @400 CW/R with two of the major nine water authorities,
Severn Trent, Yorkshire Water (which has some very simple systems) being the
major players. Other water authorities have tried in the past to build and
run CW/R  with little success and no further investment. The majority of
CW/R are used in secondary and tertiary treatment of sewage effluent and are
generally added to conventional systems. However, they are also being used
to treat highway/carpark runoff before it reaches storm drains.

In the UK CW/R are known as reedbeds because of the common name of the
aquatic plants used i.e Reed mace, /Typha ltifolia/

Effluent suitable for treatment by CW/R
*Domestic waste water
* Animal slurry
*Silage liqueur
*Urban run off
*Pretreatment of water entering sensitive areas.

There are two main species of plant generally used in CW/R systems in the


/Typha latifolia/. Tall (max 2.0M), stout, Agressicely creepting perennial.
Leaves, long, flat, greyish. 10-20mm wide. Flowers in two tight contiguous
spikes, 10-15mm long, the straw coloured male immediately abut the much
stouter chocolate brown, sausage shaped female, Jul-Aug.

/Typha angustifolia/. Slender than /T, Latifolia/ and differing in its
narrower leaves 5mm wide, and the male and female spikes being well apart.

Typha spp. Are found extensively in the northern hemisphere and south
towards the equator.


/Phragmites australis/. A common, v.tall, stout, coarse perennial, forming
extensive beds with its creeping rootstock. Leaves greyish, smooth-edged to
50cm wide, collapsing in winter. Lingule a line of hairs. Inflorescence a
spreading panicle. The numerous unawned, usually dark purple spikelets with
2-10  florets and  long silky hairs along the axis. Flowering Aug-Oct/ New
shoots arising from rhizomes

Phragmites spp. Are very wide spread throughout the world and the most
commonly used in CW/R systems.

Plant selection
*The aquatic plants used fulfil several requirements adaptable to local
*High photosynthetic rate and biomass
*High oxygen transport ability
*Tolerance of pollution
*Pollutant assimilative capacity. If not in the plant tissue. around or in
the root structure
*Resistance to pests and disease
*Easy of management
*Planting density?

* Inlet pipe allows even distribution of effluent across width of bed i.e.
gutter type construction, rate of flow v.slow.

* Inlet filled with crushed rocks (forming cambion), 60-150mm dia, which act
as a large filter absorbing large solids. Effluent travels down, assisted by
gravity, and across the inlet further into the system. Eventually, after
construction, a biofilm of bacteria and fungi develops on the surface of the
stones e.g. similar to a contemporary trickle feed system.

* Material flows horizontally across the CW/R. The system shown in figure 1
is a subsurface design with the material crossing the bed through the porous
matrix of the substrate. It is also possible to design & build surface flow
CW/R that have the advantage of not requiring substrate. however, these type
of CW/R are not as effective per unit area as subsurface systems, therefore
more land is required.

* Size per bed 3-5m*m pe-1 (pe = people equivalent - 6 people = 1 cow.
Tendency for downsizing. Ratio 3:1 (Length:width)

*The inclined bed of the system assists in the movement of effluent across
the bed. The slope may be between 1-8% with a preference for lower values.

*Flow rate (horizontal velocity) maximum 0.0001ms. V.Slow.

*Depth @0.6m, Maximum rhizome and root structure depth 0.3m (gravel greater)

* Control of input in a separated supply system is relatively easy
guaranteeing a steady effluent supply. Heavy rain fall causes variation in
input volume possibly causing overflow. High (bund) walls and secondary
systems to absorb ovrflow are included in designs.

*Important that the surface of the bed is level, regular flooding, by
sealing outlet, helping to kill of terrestrial weeds until aquatic plants
are established.

*The impervious liner of the CW?R serves to seal the bed and prevent
leakage. Man made materials i.e. low density polythene or bentonite (v.fine
clay) and geotextile layering are used but some systems are puddled.

*The substrate must allow flow of the liquid (hydraulic capacity) through
its matrix at a sufficient rate which allows treatment to occur. Liquid
passing through he matrix to fast will undergo no chemical/biological
changes i.e. the hydraulic capacity (HC) must be correct for the design.

*Mixtures of soil and gravel seem to be the preferred substrate providing a
suitable rooting medium with good HC (soils low HC, gravel high HC). Pea
gravel <10mm dia usually recommended.

*Longer effluent retention time enhances treatment. Not necessarily
important, based on size.

*soils (esp. clays absorb metals due to their high cation exchange capacity
(CEC) (exchanging positive metals with toxic metals in the liquid). This can
lead to acute accumulation which will require removal and disposal of the
substrate i.e. absorption of lead and release of calcium. Clays can be
selected to absorb particular metals. The accumulation of toxic metal
cations as a result of cation exchange is NOT bioaccumulation.

*Organic material i.e. litter layer or composted settled solids in surface
systems) can also remove metals. eventually the CEC of the substrate can
become saturated and it is necessary to test the cation levels in the
substrate and replace it if necessary with contaminated substrate being
removed (land fill, processing - metal extraction?)

*The lifespan of a CW/R is undefinable, and dependant on the effluent type
being treated. Several beds are usually designed side by side  in
compartments which can be isolated individually for maintenance.

*The substrate contains the roots and Rhizomes of the aquatic plants. The
rhizomes branch laterally and vertically to  produce more leaf growth above
the surface and stem growth below. The roots, which absorb material, create
extensive networks. The root hairs provide a large surface area interface
with the soil. The type of plants used take oxygen down through the leaves
in to the underground rhizomes/roots and into the surrounding substrate.
This creates an aerobic zone around the roots in an otherwise anaerobic
environment allowing two populations of bacteria to grow, aerobic  in the
rhizosphere and anaerobic below the rhizosphere. In winter the upper portion
of the leaves dies off providing thermal insulation of the substrate;
organic material input (gradually increasing the depth of the substrate
5-20mm / yr), and the roots die back. The rhizomes are unaffected. The
growing season of the plant is a major factor in the overall efficiency of

*Relatively low capital costs. Compared with standard sewage/effluent
methods/plants. Surface flow > land > cost.
*Relatively simple construction. Subsurface > cost
*Relatively low maintenance costs. Monitoring: effluent; substrate;
*Robust process. Vulnerable during initial phase
*Environmentally acceptable. Natural principals using plants to mop up
pollution from aquatic pollutants
*Ecological benefits. Naturally treated water input

*Low loading rates

*Minimum frequency - monthly/seasonally
*Parameters monitored: suspended solids, biological oxygen demand, total
organic nitrogen
the water quality parameters which can be examined include temperature, pH,
DO, total suspended solids, volatile suspended solids, CBOD5 (total and
soluble), COD (total and soluble), TKN, NH3-N, total P and feacl coliform



         Mark Lomas        :  mlomas at
      Web  :

    Natural Technology Systems, Co.Clare, Eire.
Reed Bed Wastewater Treatment. Eco-Construction

  (RBTS= Reed Bed Treatment System, Constructed Wetland
BOD = Biochemical Oxygen Demand
SS= Suspended Solids)

Reduction of soluble organic compounds is the most important aspect of a
RBTS, since these processes lead to major reductions in BOD and SS. Complex
microbiological effects take place, but, in simple terms, micro-organisms
(bacteria, protozoa) use the carbon from the dissolved organic matter for
the synthesis of new cellular material, and in so doing produce stabilised
by-products such as water and carbon dioxide.
In an aerobic situation, such as a vertical flow reed bed,  aerobic
chemoheterotrophs oxidise organic compounds and release ammonia, while
chemoautotrophs oxidise ammoniacal nitrogen to nitrite and nitrate
(nitrification). Thus :

Organic Matter (C+H+N+O) + Bacteria + O2 >> New Cells + CO2, NH3, H20

In anaerobic conditions, a two-step process occurs, mainly involving
anaerobic heterotrophic bacteria.

Organic matter + bacteria >> alcohols, acids, new cells  >>
CH4,H2S,NH3,CO2,H20 + new cells

The methane-forming bacteria operate at optimum between pH6.5 and pH7.5, and
it is preferable to promote this range, since gases formed in more acidic
conditions are more unpleasant (eg. Hydrogen Sulphide, Ammonia).

4. Nitrogen :
The main mechanism for removal of nitrogen is nitrification (ammonia >
nitrite) followed by denitrification (nitrite > nitrate). Nitrates are
either converted to harmless Nitrogen gas by bacteria in anoxic zones or
taken up by plants in the treatment system. Other methods of nitrate removal
include volatilisation and adsorption, although these are of lesser
Organic nitrate is easily mineralised to ammoniacal nitrogen, whether in
aerobic or anoxic conditions. There follows microbial nitrification, where
Nitrosomonas and Nitrobacter microbes convert ammoniacal nitrogen to nitrite
and nitrate. Biological denitrification is carried out by several genera of
heterotrophic bacteria, including : Achromobacter; Aerobacter; Alcaligenes;
Bacillus; Brevibacterium; Flavobacterium; Lactobacillus; Micrococcus;
Proteus; Pseudomonas and Spirillum. Although a temporary step in the
de-nitrification process produces nitric oxide and nitrous oxide, these are
usually converted and passed into the atmosphere as nitrogen gas.

The above is extracted from something I wrote for convincing planning
departments that our reed beds do the job.
It doesn't help with designing or sizing them, but our website will soon be
carrying this type of practical info. If anyone's experimenting with
aquaculture or nutrient recycling systems, we'll help out by e-mail, but I'd
suggest buying a cheap pond test kit and playing about with the basic tests
for ammonia, nitrite and nitrate, and sizing the bed for a particular
application. If you're looking for re-use of nitrate eg. in feeding
greenhouse crops, you'd want to hold back the treatment to give high
nitrate, but if you were wanting to dispose of effluent to a watercourse,
you'd also want low nitrate.


On Fri, 22 Oct 1999 02:05:26 +1300, "Myk Rushton" <permaculture at> 
wrote in the alt.permaculture newsgroup:

After our discussion on reedbeds I came across the following in the 
Bamboo Specialist Nursery (NZ, Auckland) catalogue

Sewage filter bamboo: P. makinoi, C. marmorea, P. hindsil, P. aurea, P. hebonis.

all species shown are suckering and C. hebonis is considered invasive in
warmer climates.


From: James Mortensen <jmbamboo at>
Newsgroups: rec.gardens.bamboo
Subject: Re: Bamboo varieties for sewage filtering in constructed wetlands
Date: Thu, 21 Oct 1999 23:02:55 -0500

Not sure what P. (or C.) hebonis. Also, what do you mean by "suckering." 
At least 3 on the list are monopodial and invasive.
Jim Mortensen


From: "David Priem" <dpriem at>
Newsgroups: rec.gardens.bamboo
Subject: Re: Bamboo varieties for sewage filtering in constructed wetlands
Date: Fri, 22 Oct 1999 00:27:33 -0500

For sewage filtering.

Darwin Nelson, who has a large bamboo farm in South Texas is experimenting 
with bamboo for just this purpose.  One of the bamboo species he is trying 
is Semiarundinaria fastuosa.  There may be some others he is trying as well.



From: "Phillip Davidson" <phildavidson at>
Newsgroups: rec.gardens.bamboo
Subject: Re: Bamboo varieties for sewage filtering in constructed wetlands
Date: Sat, 23 Oct 1999 23:57:25 -0700

Check on page 27 of the latest issue of Pacific Nw Bamboo. there is an
article entitled 'Double Happiness' by Oregon St Univ Ag Experiment Station
that details bamboo used as a "sludge suck-up."
Very interesting article.


Editor, Pacific NW Bamboo

Jade Mountain Bamboo Nursery
"We Specialize in Hardy Bamboos"


  This section answers the most frequently asked questions regarding RBTS.

  Marshlands are Nature's kidneys, just as forests are her lungs. They clean water using processes as old as Life itself :

  What is a Reed Bed System ? An excavated or constructed container, filled with gravel and sand or soil. It is planted with a
  variety of aquatic plants, with an emphasis on species such as the Common Reed (Phragmites Australis) and Reedmace (Typha
  Latifolia). There are two main types of gravel-based reed bed (such as those designed by Natural Technology Systems) :

      a.Vertical Flow Reed Beds (VFRB's) : These can handle large quantities of sewage, and are most effective at reducing
       BOD by oxygenation, and Suspended Solids. The liquid flows onto the surface and percolates downwards and quickly
       away, before the airspaces between the gravel fill up with air again.
      b.Horizontal Flow Reed Beds (HFRB's) : These are continuously full of water (to just below the gravel surface),
       encouraging zones of anaerobic activity which are effective at stabilising ammonia and nitrates. 

  How Do They Work ? The reed bed is preceded by a settlement/septic tank, which settles out and liquifies the sewage. A
  two-chamber tank, conforming to local Building Codes, is recommended. As the wastewater enters the reed bed, organic material
  and fine particles are filtered by the gravel, and form a slime on the gravel. Large populations of bacteria and other organisms
  convert the slime into harmless forms, such as water, carbon dioxide, nitrogen. They also convert nitrates in the wastewater into
  forms which are more easily taken up by plants. Harmful pathogens, such as E.Coli and Salmonella, are killed off by other
  bacteria which are much more suited to the reed bed environment.

  Does the Reed Bed need the plants ? Yes. The plants, which are all native, provide ideal conditions around their roots for the
  sewage-eating bacteria to operate. Some of the plants pass oxygen down from their leaves to this root zone. The aggressive root
  systems of the plants, in what is, for them, ideal growing conditions, continually force the gravel apart, maintaining a hydraulic
  pathway which would soon be blocked up without the plants.

  How big is a Reed Bed System ? : Using a combination of vertical and horizontal beds, full treatment can be achieved in around
  3 m2 per person. The systems are designed to blend into the general landscape of their surroundings, and, once established,
  become a landscape feature and wildlife habitat in their own right.

  What services do NTS provide ? :  We can either design a RBTS for 'Self-Build' construction by our clients (or their own
  contractor), or we can contract to carry out the complete installation. With our design and construction information, the actual
  construction of a RBTS is not difficult. For self-build projects, we can also supply liners, plants, geo-textiles etc. (if they're not
  available locally), and will 'oversee' the project at critical stages of construction. 
  We can provide design and supervision on-line to anyone with a little common sense (and a tape measure). Our consultancy rates
  are reasonable. Please e-mail for details.

  Are Reed Beds acceptable to Planning Authorities ?  Yes. We provide all necessary documentation and design drawings to
  accompany a planning application. RBTS's have now been installed throughout Europe and USA, and although local codes may
  differ, wastewater is much the same everywhere.

  In what circumstances is a Reed Bed System appropriate ? On all sites which fail the standard tests for groundwater and/or
  percolation, or are unsuitable for a conventional septic tank because of proximity to boundaries, wells etc.; In areas which have a
  problem with contamination of groundwater or eutrophication of watercourses; In developments where mains sewage treatment, or
  alternative package treatment plants would be too expensive; In commercial/industrial/agricultural situations.


  What are the alternatives to a RBTS ?  Other domestic package systems exist. They usually involve a big plastic tank with
  pumps and lots of other moving parts which get clogged or break down, and have a matrix covered in micro-organisms which do
  the same job as a reed bed system. These are about three times the cost of a RBTS to install, and need regular, expensive
  maintenance.  Dry composting toilets are another option (with a small reed bed system to treat 'greywater' from baths, showers,
  basins, washing machines etc.) if you can convince your local planning authority (and your mother-in-law).

  Can a RBTS cure a faulty old septic tank with leachfield or soakpit ? Yes. Most problems with existing systems arise from a
  high level of suspended solids which eventually clog up the leachfield or soakpit. We can advise on the most effective ways to
  deal with faulty systems.

  Is a sloping site necessary ?  No. Reed bed systems can be built on flat land, and pumps can make installation possible on
  almost any unsewered site. If you're off the grid, the small amount of pumping involved can easily be handled by a Photovoltaic
  panel or run from a renewable power installation.

  Do RBTS's work in winter ?  Yes. BOD  (Biochemical Oxygen Demand - the main signifier of organic pollution) is dependent on
  temperature. In very cold climates, some special measures may need to built in.

  Is a RBTS suitable for a holiday home ?  If the house is unoccupied for long periods, a horizontal flow bed would be the best
  option, but it would need extra fertiliser until the plants became established.

  Do they need a lot of maintenance and specialist knowledge by the householder ? Reed beds need much less maintenance
  than other package systems. A quick occasional check for blockages can be carried out, but float-switches can be installed to
  alert the owner to potential problems, and overflows are designed to divert effluent from blocked sections to the next stage. A
  valve is installed on VFRB's and is switched across every three to seven days. Plants should be cut back to ground level in
  autumn, and levels in the horizontal stage should be altered occasionally during establishment to promote root growth downwards.
  NTS provides full instructions and back-up with all systems designed, and a regular mail-out to remind clients when specific
  operations are required. A Pond Test Kit is provided with each system (Ammonia, Nitrite, Nitrate and pH), and, a feature recently
  introduced is tracking the results of these simple tests in a computer order to warn of possible problems.  In a worst
  case scenario, with absolutely no maintenance from the homeowner over years, natural balances would ensure that the system
  remained effective far longer than other package systems. 

  Are reed beds a danger to small children ? The gravel matrix will support several tonnes and is usually near ground level, and
  so there is no risk of children falling into danger. Gravel based reed beds have no areas of water showing above the surface, and
  so there is no risk of drowning. Systems which incorporate ponds, usually for aesthetic purposes, are always designed with a
  gradual slope up from deeper water, and are rarely more than 1metre deep, but these should be treated with the same caution as
  any garden pond, and can be fenced off if necessary. As regards any health risk associated with children playing near the reed
  bed, children should be educated not to play within the actual treatment area. However, the health risks associated with reed beds
  are less than the risks involved in playing around farmyards or on playing fields contaminated with dog excrement. If in doubt,
  fence them out.
  Do Reed Beds smell ? Any smell associated with a well-designed and properly functioning reed bed is due to untreated effluent
   from the septic tank at the reed bed inlet. This is no more of a problem than the smell from the vents on the septic tank itself,
   but can be eliminated by constructing a porous cover over the inlet dispersal pipe. After entering the reed bed, breakdown of the
   effluent begins, and when operating properly, the gases produced are mostly carbon dioxide, nitrogen and methane, which are
   odourless. It is only when the system is not operating properly that noxious odours, such as ammonia and hydrogen sulphide,

   What will a system cost ?  In a self-build situation, where we provide design and overseeing of the project, a complete
   treatment system can be installed  for between £1000 and £1500, but this depends on local availability of materials. (In the US,
   materials are generally cheaper than here in Europe).

   What Back-up do NTS provide ?  Design-Only : We provide all calculations, drawings, documentation and construction details,
   after carrying out a site survey for percolation, levels etc. (or providing remote clients with the necessary information to carry
   out the survey).  We over-see the construction process, and provide a maintenance and testing schedule. We can supply all
   liners, geo-textiles, plants and equipment. Full Construction :  We can only provide this service in Ireland and South West
   In all cases, a Pond Tet Kit is supplied for weekly testing (which takes 5 minutes) by the householder. Results are posted, faxed
   or e-mailed to NTS for tracking in our database.

   Worldwide Service : If you can read a tape measure, we can give you all the information required to carry out the site survey,
   and conduct the whole design & supervision via e-mail. 
   For larger systems, we are available to travel to projects.

    Applications of Reed Bed Treatment Systems :

    Reed Bed Treatment Systems are being used throughout the world to treat a wide variety of wastewaters. In addition to
    domestic sewage, they have been successfully employed in the treatment of agricultural and industrial pollution, and are
    ideally suited to most forms of organic pollution. Although not all wastewater requires treatment, there are several scenarios
    where a RBTS is the most viable form of treatment :

    Domestic Sewage Treatment :  In simple terms, any site which fails local Building Codes for groundwater level and percolation
    tests can benefit from installation of a RBTS, and this is usually the most cost-effective solution.  
    Sites which fail because of high groundwater level are often natural wetlands, and therefore a RBTS fits perfectly into the
    situation. Effluent is treated fully before gradual dispersal to ground via an unlined pond and subsequent plantation of willow
    spp. which provide a 'sink' to release water gradually and prevent surface flow to neighbouring land. Soil permeability needs to
    be carefully assessed before 'puddled clay' construction can be specified, since high groundwater is unrelated to percolation
    characteristics (except in 'perched' water table situations). 
    When failure of the site is due to high percolation,  ie. where effluent flows too quickly downwards and could contaminate
    drinking water supplies, a reed bed system holds back the effluent for full treatment. Final disposal can be as above, with
    ponds and wet woodland areas, or a minimal percolation area can be constructed without fear of contaminating groundwater.
    Such sites are, however, unsuitable for 'puddled clay' construction.
    Sites with low percolation, likewise, benefit from a RBTS, although final disposal becomes the over-riding concern . In this
    case, pond and woodland areas are designed  with reference to percolation/permeability rates, and the direction and rate of
    outflow are controlled so as not to cause a nuisance to neighbouring property.
    All new septic tank installations can benefit from inclusion of a RBTS. The life of any percolation area will be greatly improved.

    Hotels, Estates,Villages etc.  Treatment systems can be designed to handle the effluent from groups of  dwellings, using the
    same criteria regarding ground conditions as for domestic systems. The size of a reed bed is not directly proportional to
    occupancy (population equivalent, or 'pe'), and so overall size (square metres per person) reduces at higher loadings.
    In addition to treating wastewater in difficult ground conditions, reed beds can be very attractive in remote situations where it is
    unlikely that central (mains) sewage treatment will ever be installed, due to cost. Existing sewage treatment which no longer
    satisfies more stringent quality standards, or which, simply, is no longer working effectively (eg. septic tanks where a soakpit
    was built in the past, or where the percolation area is malfunctioning) are also suitable for treatment by RBTS.
    In addition, RBTS can be added as tertiary treatment to large-scale 'conventional' sewage works where effluent needs to be of
    the highest quality.

    Commercial/Industrial :  Many commercial processes produce waste water which can be viably treated by RBTS. Organic
    pollutants are the most suitable, and so Reed Beds can be specified for processes such as dairying & cheesemaking ;
    breweries ; food processors and manufacturers ; butchers &  slaughterhouses, although systems have been designed to
    remove everything from phenols to heavy metals.

    Agricultural :  Certain agricultural wastes are suitable for treatment by RBTS. Yard run-off and dairy parlour washings are the
    most suitable, although it can be viable to treat stronger pollutants (slurry, silage effluent etc.) after breakdown in lagoons.
    Since certain intensive farming activities now require an EPA license before the granting of planning permission, reed bed
    systems may become even more viable in the future, although traditional farming practises (deep litter, composting etc.) will
    prove the best option in the long run.


  Summary of Main Removal Mechanisms In RBTS :

  Constituent                                             Removal Mechanism
  BOD                                                         Aeration
                                                                   Microbial action

  Suspended Solids                                     Sedimentation

  Soluble organic matter                              Aerobic microbial degradation
                                                                   Anaerobic microbial degradation

  Nitrogen                                                    Ammonification + microbial nitrification                     
                                                                   + microbial denitrification
                                                                   Plant uptake
                                                                   Matrix adsorption
                                                                   Ammonia volatilisation

  Phosphorus                                              Matrix sorption
                                                                   Plant uptake

  Metals                                                      Adsorption and cation exchange
                                                                  Plant uptake
                                                                 Microbial oxidation/reduction

  Pathogens                                               Sedimentation
                                                                  Natural die-off
                                                                  UV irradiation
                                                                  Excretion of antibiotics from macrophyte                      


  Efficiency of Reed Bed Treatment Systems :

  RBTS are effective in reducing all the major signifiers of pollution in wastewater.
  Results from a sewage treatment RBTS show that high levels of removal are possible :

                                          Influent          Effluent      % Reduction
  SS        (mg/l)                     333                11                96.7

  BOD5                                  544               0.06              99.99

  NH4                                    158               87.5              94.94

  PO4                                      83               26                 65.06

  F.Coliforms (No/100ml)      5x107          2x103               99.99
  Blackwater & Greywater :

  For the purposes of treatment, wastewater is classified as black or grey. By separating the two at source, overall efficiency is
  raised by decreasing the loading on the septic tank. Greywater is high volume, low BOD, low pathogen content, and the two
  types are classified as follows :

  Blackwater     WC's                               Greywater      Basins
                        Kitchen Sink                                         Baths
                        Dishwasher                                           Showers
                                                                                    Washing Machine

  In a new-build situation, it is simple to run a second soil-pipe taking greywater direct to the reed bed. When a composting toilet
  is acceptable, the greywater reed bed system will also need a combined grease/silt trap to cope with the added loading from
  kitchen sink and dishwasher.

  If you have a garbage disposal unit in the kitchen sink, take out the fuse and compost your kitchen waste or build a Wormery.
Date: Fri, 14 Oct 1994 09:56:58 -0500 (CDT)
From: Steve Diver <steved at>
To: Larry London <london at>
Cc: permaculture-mg at
Subject: Re: E-Z Home Aquaculture (fwd)

> From: wbw at (William B. Warren)
> Newsgroups: sci.environment,
> Subject: E-Z Home Aquaculture
> Date: 13 Oct 1994 16:31:32 -0400
> Organization: North Shore Access; a service of Eco Software, Inc.

> If one were to grow some tilapia in a solar algae tank or two, pump 
> the wastewater through a nitrifying tank, and then divert the water 
> through hydroponically grown grasses, herbs, etc. before returning it to 
> the fish tank(s), is this water a satisfactory nutrient solution? 
> Does one need to feed the fish a particular food, or a particular variety of
> foods to obtain a complete nutrient solution for the plants? Or would one 
> need to regularly add certain trace elements or salts?
> Ideas,Comments,Suggestions,Criticism?
> Thanks in Advance,
>                Will

Tom Speraneo in West Plains, MO, has developed an integrated
system based on tilapia and basil culture.  He has also
raised tomatoes & cukes, but like other folks who've tried 
aquaponics, he found herbaceous plants are better adapted 
than heavy-feeders like fruiting plants. 

Effluent from the bottom of the fish tanks is trickle irrigated 
"directly" onto gravel-cultured hydroponic vegetable beds.  
There is no intermediary stage like a biofilter or
nitrifyer.  The plant roots and bacteria living in the
gravel serve as the biofilter.  They remove the nitrates and
other nutrients as food.  The purified water is then
recirculated back to the fish tanks after going through an

The fertility input to hydroponic production is the fish
feed.  Adjustment of protein level in the fish feed helps 
regulate pH, etc.  Fish metalobolites (i.e., manure), 
decomposing fish food, and algae are the source of
nutrients.  The bacteria in the gravel run the whole show. 
To inoculate the system, collect a liter of tank water from 
a plain home aquarium and dump it in the fish tanks.  

The aquatic product, tilapia, is a secondary product.  The 
largest biomass and salable product is the vegetable/herb
produce.  At one time, he estimated 70 lbs produce to every
1 lb. tilapia.  North Carolina State Univ. research data was
2:1.  Speraneo modeled his system after NCSU and then
modified it about a dozen times to get where he is today. 

The Freshwater Insititute in West Virginia does it very 
differently.  They focus on cutting edge recirculating 
trout aquaculture.  Using oxygenation and ozonation, plus
demand feeders and injected aerated stream water, they are
able to get impressive trout yields in tanks.  Recirculated
water is treated with an expensive clarifier, sand biofilter, 
and aerator.  

Prior to returning the water back to the natural stream 
(with a natural P of 3 ppb), they remove the several hundred 
parts per million P, plus N, etc., by running it through 
aquaponics or constructed wetlands in greenhouses.  Aquaponic plants 
raised include strawberries and lettuce.  Constructed wetland plants 
used include turf grasses and vetiver grass.  P removal is 
80% first time through.  Biomass prouduction is solely based on 
nutrients in used fish tank water except for iron injection. 

Hope these notes and ideas are helpful.  I've been tracking
these and other aquaponic systems because they represent a 
fine model of sustainable food production, and fit well with
the goals and concepts of permaculture. 

Steve Diver
Fayetteville, AR

Sun Oct 16 23:08:22 EDT 1994
Article: 2392 of
From: M.E.Thornton at (Mark E. Thornton)
Newsgroups: sci.environment,
Subject: Re: E-Z Home Aquaculture
Date: 14 Oct 1994 12:35:59 GMT
Organization: The University of Birmingham, UK

In article <37k5f4$adc at>, wbw at (William B. Warren) says:

>If one were to grow some tilapia in a solar algae tank or two, pump 
>the wastewater through a nitrifying tank, and then divert the water 
>through hydroponically grown grasses, herbs, etc. before returning it to 
>the fish tank(s), is this water a satisfactory nutrient solution? 
>Does one need to feed the fish a particular food, or a particular variety of
>foods to obtain a complete nutrient solution for the plants? Or would one 
>need to regularly add certain trace elements or salts?
>Thanks in Advance,
>                 Will

Try and catch the latest copy of 'SunWorld', the magazine of the International
Solar Energy Society - it has an article in it about farming parent prawns using
solar energy. I don't know how useful it would be, though.

You can e-mail the editor at <teasdale at>

Hope this helps,


From: steved at (Steve Diver)
Newsgroups: alt.sustainable.agriculture
Subject: Aquaponics revisited
Date: 17 Oct 1994 19:15:12 -0000

In my discussion on Tom Speraneo's integrated tilapia and 
basil culture system, I said he'd switched to herbaceous
crops to avoid heavy feeders like tomatoes and cukes which
are fruiting crops.  

This was an error on my part*.  In fact, Speraneo has raised 
tomatoes and cukes very nicely in the past, has done so just
recently, and plans to move away from basil back to these 
two crops as well as peppers in the near future. 

* [although I am aware of other systems where herbaceous 
crops were chosen over fruiting crops due to the "heavy
feeder" syndrome]

Largely due to NAFTA, Mexican basil at $2.00/lb. has undercut 
Speraneo's normal $8.00/lb restaurant herb market in St.
Louis.  Thus, he plans to raise crops that market well 

Steve Diver
Fayetteville, AR

Article: 2444 of
From: wbw at (William B. Warren)
Newsgroups: sci.environment,
Subject: Re: E-Z Home Aquaculture
Date: 17 Oct 1994 07:24:30 -0400

The idea is to treat the fish wastewater with hydroponically grown plants,
not human wastewater.

On board my 53' biobarge I treat small amounts of human sewage 
biologically in a series of 22 tanks. Almost no pathogens make it through 
my 'marshland' tanks (hydroponically grown spartina).

Perhaps Ma nature knows her stuff,


Lawrence F. London, Jr.  Venaura Farm  
/intergarden /permaculture /permaculture-online
lflondon at  london at

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