Source: U.S. EPA., 2001.

FIGURE 1 THE OPEN AEROBIC TANKS

OF THE LIVING MACHINE® IN SOUTH

BURLINGTON, VT

United States

Environmental Protection

Agency

Wastewater Technology Fact Sheet

The Living Machine®

DESCRIPTION

The Living Machine® is an emerging wastewater

treatment technology that utilizes a series of tanks,

which support vegetation and a variety of other

organisms. The Living Machine® was conceived by

Dr. John Todd, President of the non-profit

organization Ocean Arks International, and gets its

name from the ecologically-based components that

are incorporated within its treatment processes

(microorganisms, protozoa, higher animals such as

snails, and plants). The Living Machine® has

sometimes been referred to as the “Advanced

Ecologically Engineered System” or AEES. The

Living Machine® is now designed and marketed by

Living Machines, Inc. of Taos, New Mexico.

The Living Machine® is a second generation design.

Dr. Todd developed the Living MachineTM design

concept after working on a number of similar small

pilot-scale facilities, now referred to as Solar

AquaticsTM and marketed by Ecological

Engineering Associates of Marion, Massachusetts.

The Living Machine® incorporates many of the

same basic processes (e.g., sedimentation, filtration,

clarification, adsorption, nitrification and

denitrification, volatilization, and anaerobic and

aerobic decomposition) that are used in

conventional biological treatment systems. What

makes the Living Machine® different from other

systems is its use of plants and animals in its

treatment process, and its unique aesthetic

appearance. While these systems are aesthetic

appealing, the extent to which the plants and

animals contribute to the treatment process in

current Living Machine® designs is still being

verified (U.S. EPA, 2001). In temperate climates,

the process is typically housed within a large

greenhouse, which protects the process from colder

temperatures.

Living Machines, Inc. describes the Living

Machine® as being a wastewater treatment system

that:

• Is capable of achieving tertiary treatment;

• Costs less to operate than conventional

systems when used to achieve a tertiary

level of treatment; and 

• Doesn’t typically require chemicals that are

harmful to the environment” as a part of its

treatment process (Living Machines, Inc.,

2001).

Several federally-funded Living Machine®

demonstration systems have been constructed, the

largest of which handled design flows of up to

80,000 gpd. As configured for these

demonstrations, these systems treated municipal

wastewaters at various strengths, and reliably

produced effluents with five-day biochemical

oxygen demand (BOD5), total suspended solids

(TSS), and Total Nitrogen < 10 mg/L, Nitrate

< 5 mg/L, and Ammonia < 1 mg/L (U.S. EPA, 2001

and see Table 1). With regard to phosphorus

removal, the Living Machine® process is capable of

about 50 percent removal with influents within the

5-11 mg/L range (U.S. EPA, 2001). In addition to






 

Source: Living Machines Inc., 2001.

FIGURE 1 THE COMPONENTS OF THE LIVING MACHINE®: (1) ANAEROBIC REACTOR,

(2) ANOXIC REACTOR, (3) CLOSED AEROBIC REACTOR, (4) OPEN AEROBIC

REACTORS, (5) CLARIFIER, AND (6) “ECOLOGICAL FLUID BED”

the demonstration projects, the Living Machine®

technology is being used by a variety of municipal

and industrial clients, where similar performance

has been reported.

Treatment Process

A typical Living Machine® comprises six principle

treatment components, after influent screening. In

process order (see Figure 1), these are (1) an

anaerobic reactor, (2) an anoxic tank, (3) a closed

aerobic reactor, (4) aerobic reactors, (5) a clarifier,

and (6) “ecological fluidized beds” (EFBs). While

the open aerobic reactors and EFBs are found in

almost all Living Machines®, the other components

are not always utilized in the treatment process.

The specific components used are selected by the

designers depending upon the characteristics of the

wastewater to be treated and the treatment

objectives. Sometimes additional process

components may be added if considered necessary

by the designers. For example, the demonstration

system in Frederick, Maryland utilized a “Final

Clarifier” and a high-rate subsurface flow (SF)

wetland as the last two components of its treatment

train.

Anaerobic Reactor (Step 1)

When it is employed, the anaerobic reactor serves

as the initial step of the process. The reactor is

similar in appearance and operation to a septic tank,

and it is usually covered and buried below grade.

The main purpose of the anaerobic reactor is to

reduce the concentrations of BOD5 and solids in the

wastewater prior to treatment by the other

components of the process. When necessary, gases

are passed through an activated carbon filter to

control odor.

Raw influent enters the reactor, which acts as a

primary sedimentation basin. Some of the

anaerobic reactors used have an initial sludge

blanket zone, followed by a second zone for

clarification. Additionally, strips of plastic mesh

netting are sometimes used in the clarification zone

to assist with the trapping and settling of solids, and

to provide surface area for the colonization of

anaerobic bacteria, which help to digest the solids.

Sludge is typically removed periodically via

perforated pipes on the bottom of the reactor, and

wasted to a reed bed or other biosolids treatment

processes. Gasses produced are passed through an

activated carbon filter or biofilter for odor control.

Anoxic Reactor (Step 2)

The anoxic reactor is mixed and has controlled

aeration to prevent anaerobic conditions, and to

encourage floc-forming and denitrifying

microorganisms. The primary purpose of the anoxic

reactor is to promote growth of floc-forming

microorganisms, which will remove a significant

portion of the incoming BOD5.

Mixing is accomplished through aeration by a

coarse bubble diffuser. These diffusers are typically

operated so that dissolved oxygen is maintained
below 0.4 mg/L. The space over the reactor is

vented through an odor control device, which is

usually a planted biofilter. Additionally, an

attached growth medium can be placed in the

compartment to facilitate growth of bacteria and

microorganisms.

Settled biosolids from the clarifier (Step 5), and

nitrified process water from the final open aerobic

reactor (Step 4) are recycled back into this reactor.

The purpose of these recycles is to provide

sufficient carbon sources to the anoxic reactor to

support denitrification without using supplemental

chemicals, such as methanol.

Closed Aerobic Reactor (Step 3)

The purpose of the closed aerobic reactor is to

reduce the dissolved wastewater BOD5 to low

levels, to remove further odorous gases, and to

stimulate nitrification.

Aeration and mixing in this reactor are provided by

fine bubble diffusers. Odor control is again

achieved by using a planted biofilter. This biofilter

typically sits directly over the reactor and is planted

with vegetation intended to control moisture levels

in the filter material.

Open Aerobic Reactors (Step 4)

Next in the process train are the open aerobic

reactors, or aerated tanks. They are similar to the

closed aerobic reactor in design and mechanics (i.e.,

aeration is provided by fine bubble diffusers);

however, instead of being covered with a biofilter,

the surfaces of these reactors are covered with

vegetation supported by racks. These plants serve

to provide surface area for microbial growth,

perform nutrient uptake, and can serve as a habitat

for beneficial insects and microorganisms. To what

extent the plants enhance the performance treatment

process in the Living Machine® is still being

verified (U.S. EPA, 2001). However, with the

variety of vegetation present in these reactors, these

units (along with the Ecological Fluidized Beds -

Step 6) set the Living Machine® apart from other

treatment systems in terms of their unique

appearance and aesthetic appeal.

The aerobic reactors are designed to reduce BOD5 to

better than secondary levels and to complete the

process of nitrification. The size and number of

these reactors used in a Living Machine® design are

determined by influent characteristics, effluent

requirements, flow conditions, and the design water

and air temperatures.

Clarifier (Step 5)

The clarifier is basically a settling tank that allows

remaining solids to separate from the treated

wastewater. The settled solids are pumped back to

the closed aerobic reactor (Step 3), or they are

transferred to a holding tank, and then removed for

disposal. The surface of the clarifier is often

covered with duckweed, which prevents algae from

growing in the reactor.

Ecological Fluidized Beds (Step 6)

The final step in the typical Living Machine®

process are the “ecological fluidized beds” (EFBs).

These are polishing filters that perform final

treatment of the wastewater, and one to three are

used in series to reduce BOD5, TSS and nutrients

meet final effluent requirements.

An EFB consists of both an inner and outer tank.

The inner tank contains an attached growth medium,

such as crushed rock, lava rock, or shaped plastic

pieces. The wastewater flows into the EFB in the

annular space between the inner and outer tanks and

is raised by air lift pipes to the top of the inner ring

that contains the media. The bottom of the inner

tank is not sealed, so the wastewater percolates

through the gravel media and returns to the outer

annular space, from where it is again moved back to

the top of the gravel bed. The air lifts also serve to

aerate the water and maintain aerobic conditions.

The unit serves as a fixed bed, downflow, granular

media filter and separates particulate matter from

the water. Additionally, the microorganisms that

occupy the granular media surfaces provide any

final nitrification reactions.

As sludge collects on the EFB, it reduces its ability

to filter. This would eventually clog the bed

completely. Therefore, additional aeration diffusers
beneath the gravel bed are periodically turned on to

create an upflow airlift, reversing the flow

direction. This aeration is intended to “fluidize” the

bed and release the trapped sludge (hence the name

of this unit). This sludge is washed over and

accumulated at the bottom of the outer annular

space where it can be collected manually, and

wasted along with the biosolids from the anaerobic

reactor. Consequently, the name “ecological

fluidized bed” is somewhat misleading for this unit

since, in its treatment mode, it acts like a typical,

conventional, downflow coarse media contact filter

unit. Only during backwash cleaning does the bed

become partially fluidized.

After this last step, the wastewater should be

suitable for discharge to surface waters or a

subsurface disposal system, or reused for landscape

irrigation, toilet flushing, vehicle washing, etc.

(Living Machines, Inc., 2001).

APPLICABILITY

The Living Machine® is well suited for treating

both municipal and some industrial wastewaters.

As with most treatment systems using plants, it can

require a larger footprint than more conventional

systems, and its requirement for a greenhouse in

more temperate climates can impact costs.

However, its unique and aesthetically pleasing

appearance make it an ideal system in areas that

oppose traditional treatment operations based on

aesthetics (i.e., smell and appearance). The

designers also stress the educational benefits of the

Living Machine ®

(http://www.livingmachines.com/htm/planet2.htm)

in raising awareness of wastewater treatment

methods and benefits.

ADVANTAGES/DISADVANTAGES

Advantages

• Capable of treating wastewaters to BOD5,

TSS, and Total Nitrogen < 10 mg/L, Nitrate

< 5 mg/L, and Ammonia < 1 mg/L.

• Offers a unique, aesthetically pleasing

environment for treating and recycling

wastewater. This may be helpful when

attempting to locate the treatment system in

areas where the public opposes traditional

wastewater treatment operations for

aesthetic reasons.

Disadvantages

• The Living Machine® has only been shown

to remove about 50 percent of influent

phosphorous (with influents in the range of

5-11 mg/L). The removed phosphorus

appears to be primarily associated with the

incoming solids.

• The process requires a greenhouse for

reliable operation in the cold weather of

more temperate climates, adding to system

costs.

DESIGN CRITERIA

Every Living Machine® system is designed by

Living Machines, Inc. based upon the expected

wastewater volume and content, as well as the

treatment requirements and local climate. Once

these factors are known, the designers then

determine whether a greenhouse is necessary, what

types of reactors are needed, how many of each type

of reactor are required, and what capacity is required

to achieve the suitable residence times.

PERFORMANCE

The Living Machine® has reliably achieved

treatment goals of BOD5, TSS, and Total Nitrogen

< 10 mg/L, Nitrate < 5 mg/L, and Ammonia <

1 mg/L. Table 1 shows the results of independent

evaluations of two demonstration systems. The

Living Machine® demonstration project in

Frederick, Maryland was designed to treat

40,000 gpd of screened and degritted wastewater.

It employed a single anaerobic reactor for primary

solids digestion, then three parallel treatment trains,

each comprised of two open aerobic reactors, a

clarifier, three “ecological fluidized beds,” a final

clarifier, and a small, high-rate subsurface flow

wetland. The demonstration project located in

South Burlington, Vermont was designed to treat

80,000 gpd of screened and degritted wastewater,
and employed five open aerobic reactors (though

one of these was later converted to an anoxic

reactor), a clarifier, and three “ecological fluidized

beds.”

In these instances, the Living Machine® was

capable of BOD5 and TSS removal in excess of

95 percent. While the Frederick system did not

consistently achieve its goal of < 5 mg/L for

Nitrate, the Burlington Living Machine® did. The

Living Machine® reliably demonstrated about

50 percent removal of Total Phosphorous (TP),

although the Burlington system had a low influent

TP concentration (U.S. EPA, 2001).

While the Frederick Living Machine® achieved

quite good coliform removal (< 200 MPN/100mL),

the Burlington system’s effluent was above

1,000 MPN/100mL. Consequently, disinfection

may be required as an additional step depending

upon system configuration and effluent

requirements.

OPERATION AND MAINTENANCE

Routine Activities

The routine operation and maintenance (O&M)

requirements for Living Machines® are similar to

the requirements for a conventional wastewater

treatment plant, with a few additional requirements.

These additional requirements include cleaning the

inlet/outlet structure; cleaning the screen and tank;

removing and disposing sludge; and maintaining

and repairing machinery. Other requirements are

vegetation management, including routine

harvesting to promote plant growth, and removal of

accumulated plant litter. Additionally, it may be

necessary to manage fish and snail populations, and

control mosquitoes and flies (if applicable).

Residuals Management

The Living Machine® produces residuals

comparable in quantity to conventional treatment

systems. However, some of these residuals are

biosolids, while others are in the form of plant

TABLE 1 PERFORMANCE OF THE FREDERICK AND BURLINGTON LIVING

MACHINES®

FREDERICK BURLINGTON

Parameter Influent

mg/L

GH

Influent

mg/La

Effluent

mg/L

%

Removal

Influent

mg/L

Effluent

mg/L

%

Removal

Effluent

Goal

BOD5 230 156 4 97 227 5.9 97 <10

COD 944 378 21 94 556 35.9 94 --

TSS 381 70 2 97 213 5.3 98 <10

NH3 - 22 1.2 94 16.3 0.4 98 <1

NO3 - 20.8 10 52 15.9b 4.9 69 <5

TN (total

nitrogen)

- 44 11 75 29.3 5.6 81 <10

TP (total

phosphorus)

11 7.7 6 45 6.0 2.0 67 <3

a Effluent from the anaerobic reactor at Frederick into the reactors contained within the greenhouse.

b Assumes that all removed ammonia is converted to nitrate.

Source: U.S. EPA, 2001.
material. Analyses at the Frederick demonstration

system showed that plant residuals could be

composted and used for many agricultural or

horticultural purposes. The biosolids would likely

require stabilization and treatment to reduce

pathogens and indicator organisms before they

would meet Part 503 limits for sewage sludge (U.S.

EPA, 2001).

COSTS

Since the Living Machine® is designed, marketed

and trademarked by Living Machines, Inc., precise

cost data are proprietary. However, a cost

comparison with “conventional” treatment systems

was performed as a part of an independent U.S.

EPA evaluation of the Living Machines® (U.S.

EPA, 2001). Table 2 summarizes the results of this

cost comparison.

This analysis concluded that Living Machines® are

typically cost competitive with more conventional

wastewater treatment systems at flow volumes up to

1,000,000 gpd, if they are located in a warm climate

where a greenhouse is not necessary. However, if

the climate cannot support the plants year-round

and a greenhouse must be constructed, construction

costs will increase. Addition of a greenhouse

structure makes the Living Machine® cost

competitive with more conventional systems up to

flow rates of around 600,000 gpd.

REFERENCES

Other Related Fact Sheets

Other EPA Fact Sheets can be found at the

following web address:

http://www.epa.gov/owm/mtb/mtbfact.htm

1. Living Machines, Inc., 2001. Web Site:

http://www.livingmachines.com/

2. Massachusetts Foundation for Excellence in

Marine and Polymer Sciences, Inc., Boston,

MA, Ocean Arks International, Living

Technologies, Inc., 1997. Advanced

Ecologically Engineered System, South

Burlington, Vermont.

3. U.S. EPA, 2001. The “Living Machine”

Wastewater Treatment Technology: An

Evaluation of Performance and System

Cost. EPA 832-R-01-004.

ADDITIONAL INFORMATION

Living Machines, Inc.

125 La Posta Road

8018 NDCBU 

Taos, New Mexico 87571

http://www.livingmachines.com/

TABLE 2 PRESENT WORTH COMPARISON OF “LIVING MACHINES®” AND CONVENTIONAL

SYSTEMS

Process 40,000 gpd 80,000 gpd 1 million gpd

“Living Machine” with

greenhouse

$1,077,7771 $1,710,2801 $10,457,5422

“Living Machine” without

greenhouse

$985,391 $1,570,246 $9,232,257

Conventional System $1,207,0361 $1,903,7511 $8,579,9782

(1) Cost difference is less than 20 percent

(2) Cost difference is greater than 20 percent

Source: U.S. EPA, 2001.
For more information contact:

Municipal Technology Branch

U.S. EPA

ICC Building

1200 Pennsylvania Ave., NW

7th Floor, Mail Code 4201M

Washington, D.C. 20460

The mention of trade names or commercial

products does not constitute endorsement or

recommendation for use by the U.S. Environmental

Protection Agency.

Office of Water

EPA 832-F-02-025

October 2002