New applications for flotation technology

The Jameson Cell induced air

flotation (IAF) device was

invented by Professor Graeme

Jameson of the University of

Newcastle, NSW, Australia in the late

1980s. The Cell, which is patented by

The University of Newcastle

Research Associates (TUNRA)

Limited, was initially developed for

the coal and mineral industries, and

the licensing rights were acquired by

MIM Holdings Limited, Brisbane.

Environmental Group Limited

(EGL) acquired the business of

Jetflote Pty Ltd in September 1999,

including the exclusive worldwide

licence of the Jameson Cell technology

for water applications. EGL is an

Australianowned public environmental

technology company listed

on the Australian Stock Exchange.

Particle removal

Flotation is an extremely effective means of removing fine particles from liquid

wastewater streams. In the process, finely dispersed air bubbles are brought

into contact with the chemically conditioned slurry and particlebubble attachment

occurs. The particle-laden bubbles float to the surface where they are removed

from the cleaned wastewater.

In the Jameson Cell, a ‘low shear’

method is used to mix the air,

untreated wastewater and flocculants.

The untreated wastewater and

flocculants are introduced into the

top of the downcomer at low head. A

portion of the clean effluent is recycled

back into the top of the down

comer. The recycle stream passes

through an orifice, accelerating the

liquid to produce a simple liquid

plunging jet. The kinetic energy of

the jet results in air being entrained

into the downcomer in much the

same way as air might be entrained

into a bucket of water using a hose.

Air is dragged down into the liquid

and the turbulence created around

the recycle jet dissipation area breaks

up the air film into small bubbles of

mean size 300 microns. The Jameson

Cell thereby utilises the energy of the

fluid to induce air into the cell, rather

than requiring an external compressor

or blower. The bubble size ranges

from below 50 micron up to 1 mm.

The presence of air bubbles at the

time of flocculation is extremely beneficial

as it results in the bubbles

being entrapped within the actual

floc structure. The incorporation of

bubbles in the floc structure provides

buoyancy and allows particles to be

floated independent of their surface

characteristics.

The downward velocity of the

bubble/liquid mixture in the downcomer

is chosen such that all bubbles

have to descend and emerge into a

reservoir (or cell) at the bottom of

the downcomer. The reservoir acts

as a disengagement zone allowing the

aerated floc structures to ‘float’ to the

surface to form a sludge layer. The

sludge overflows the reservoir into a

launder whilst the cleaned effluent

passes to the next stage in the

process. Sludge removal is facilitated

using either a rotating paddle or

chain & flight scraper arrangement.

Advantages over conventional

flotation technologies include:

• the cell has minimal moving

  parts and therefore requires a minimum

  of maintenance

• no compressor is required
• the process is inherently a low

  power consumer. The air is self

  induced as a result of the action of

  the plunging jet in the vertical down

  comer. Process power is typically less

  than 0.1 kWh per cubic metre of

  water treated

• the low residence time of the cell

  makes it simple to operate and control

• compact design (total footprint based on rise rate greater than 18 m³

  /m² .h)

• the cell is capable of operating at

  temperatures of up to 70°C as compared

  to a process relying on

  dissolved air which is typically ineffective

  above 45°C due to reduced

  solubility of the air in the wastewater.

IAF process

The Jameson Cell technology is widely installed as a primary treatment system

for the removal of suspended solids, oil and grease. As a general rule, the

IAF process will remove 95-99% of the insoluble components. Flotation cannot

remove the soluble components of contaminants unless they can be easily precipitated

(eg. phosphorus). The process is particularly suited to removing emulsified

fat, oil and grease in addition to the BOD/COD associated with the emulsion

and the suspended solids.

A recent application of the

Jameson Cell has been for the

removal of filter media (eg. diatomaceous

earth) from highstrength wine

production effluents.

The IAF process has also been

found to be extremely effective for

biomass separation following secondary

treatment. The main advantages

are the low footprint and high

sludge solids content (4% to 8%)

compared to conventional clarification.

The process is equally effective

for sludges generated from aerobic

and anaerobic treatment, and is particularly

useful for ‘bulking’ biomass

that typically won’t settle in a

clarifier.

A major problem with many

inland wastewater treatment plants is

the proliferation of bluegreen and

green algae in wastewater stabilisation

ponds. The generation of algae

in ponds often results in EPA licence

exceedances due to elevated suspended

solids and pH levels. Despite

this problem, ponds have a number

of important advantages which

include providing treatment for wet

weather bypasses of the secondary

treatment process and as an important

backup in the event of upstream

process failure.

A Research Syndicate was established in 1995 and Jetflote conducted

extensive research on developing

flotation technology to remove algae

from affected wastewater streams.

The first stage of the project involved

culturing of Microcystis sp. and

Anabaena sp. and undertaking laboratory

testing to develop appropriate

mechanisms for flotation of the algae.

The next stage involved construction

of an IAF pilot plant to further

develop chemical regimes and the

optimum configuration for operation

of the IAF unit. The pilot plant was

extensively evaluated onsite on several

algaeladen pond storages.

The proving of this technology

was the culmination of three years of

research and onsite trialing in the

Hunter Valley and other inland sites

in Australia where raw water algae

levels exceeding one million cells per

mL of algae (corresponding to raw

water suspended solids levels of the

order 150200 mg/L). Treated water

algae levels have been generally

below 5,000 cells/mL.

Phosphorus: The IAF process can

be combined with conventional

metal salt precipitation/coagulation

of soluble phosphorus is order to

simultaneously remove algae and

phosphorus from wastewater effluents

Very low levels of residual phosphorus

can be achieved by singlepoint

coagulant dosing of aluminium

sulphate or ferric chloride e.g. total

phosphorus less than 0.2mg/L can be

achieved from raw water orthoP levels

in excess of 8 mg/L.

The Jameson Cell IAF technology

provides a cost effective alternative to

upgrading inland wastewater treatment

works since it addresses the

problem of algae growth in ponds,

thereby allowing water authorities

and councils to continue to utilise

the benefits of wastewater pond systems.

The aim of providing an effective

means of simultaneous phosphorus

removal is also addressed.

The first municipal unit to remove

algae and phosphorus from treated

sewage (maturation pond) effluent

was installed for Wagga Wagga City

Council at their Narrung Street

Sewage Treatment Plant. The plant,

treating up to 18ML/d, was commissioned

in June 1999, and has met or

exceeded all performance expectations,

producing water suitable for

discharge to sensitive receiving

waters. Process plants have since

been installed for Wagga Wagga City

Council and North East Region

Water Authority.

Jameson Cells are installed in

Korea and Malaysia for effluent

treatment from compressed timber

products manufacture and terminal

tank washing facilities. In UK the

technology is represented by

Brightwater Engineering.

There remain numerous application

areas for which the Jameson Cell

is likely to be a leading edge technology

solution. The IAF process has

been demonstrated for several applications

in sewage treatment including

primary solids removal, clarifier

supplementation or replacement,

biomass separation and effluent polishing

(algae and phosphorus

removal). The process is very compact

and cost efficient compared to

traditional technologies, with a footprint

based on a rise rate of 18 m/h or

more. The process is well suited to

stormwater and combined sewer

overflow (CSO) treatment due to the

features of low startup time, high

process rate, and ease of augmentation

to an existing site.

Pilotscale rigs (20 L/min) are

available for onsite testwork to confirm

process amenability and to evaluate

reagent addition requirements.

The article first appeared in the March

edition of WaterJournal of the Australian Water

Association.