featurearticle

Small to medium sized operations often produce wastewater with highly variable quality, which presents a number of problems to conventional filtration systems. V-FoldTM, a redesigned belt filter press, on the other

hand, offers continuous dewatering regardless of slurry flow rate or compostion, and with minimal operator intervention. Paul Day founder of Dayco Pty Ltd, Australia, explains.

Innovative Belt Filter Press Takes the Hard Work Out of Sludge

Dewatering

A unique slurry dewatering filter press that can handle

irregular slurry flow rate and composition without

operator intervention has been developed. The V-Fold

was conceived to tackle the variable flow and composition of

effluent slurries often generated during production cycles in

industries such as food processing, wineries, tanneries and

printing. The shortcomings of traditional dewatering devices

have long been a cause of unwelcome process difficulties

and high operating and maintenance costs for these industries.

The V-Fold’s unique V belt design concept (Figure 1)

overcomes these difficulties. It is inherently forgiving of

variations in slurry feed rate and composition, and as a result

dewaters continuously, and normally without operator

intervention, to produce a consistently spade-able filter cake.

The secret of the V-Fold’s success is its simple design and

forgiving nature compared with conventional filters used in small

to medium dewatering applications. Industries in this size range

often produce highly variable wastewater quality, leading to

irregular slurry flow rate and composition that can cause

problems for many conventional filtration systems. For example,

two-belt filters can suffer from slurry spills when poorly

conditioned feed is delivered to the filter, while centrifuges often

require operator adjustments to maintain good performance on

variable feeds or wet product, and dirty decant can result. Plate

and frame filter presses (chamber presses) tend to be more

Figure 1: Operating principle of the V-Fold folding belt filter press.

18 October 2002

resilient to feed conditioning in many circumstances, but cloth

blinding sometimes causes prolonged cycle times and a sloppy

cake to be discharged. Furthermore, the batch process of these

filters requires an operator to empty the cake whenever the filter

cycle is complete, which often means high operating costs.

The combination of the V-Fold’s unique V belt design concept

with an automated feed rate control overcomes these difficulties.

As a result it operates continuously and normally without

operator intervention.

How V-Fold Operates

In essence, the V-Fold is a continuous conveyor belt that folds

longitudinally as it passes around a series of vertical rollers. The

folding action forms a V-shaped cavity that can hold dilute

slurries for gravity dewatering.

Slurries to be dewatered are usually composed of a mixture of

particulate solids in water, ranging from sub-micron clays, to

grits and organic materials several millimetres in size. These are

normally ‘conditioned’ with conventional polyelectrolytes to

flocculate the particulates into soft agglomerations. The feed

enters the cavity, where most of the liquid passes through the

filter fabric as gravity draining takes place (Figure 2).

The V-Fold differs from other belt presses by using a single belt

made from a conventional filter fabric, with a reinforced centre

line where it folds. Sludge trapped in the V-shaped cavity is

wedged between the sides of the filter belt and squeezed as it

passes around the series of vertical rollers. The belt unfolds to

reveal a filter cake that is scraped from the belt and falls onto a

pad or into a bin.

The belt then passes around the drive roller and water sprays

wash both sides of the fabric, so it remains clean. In some

applications recycled water can be used for belt washing, but

because the flow is small it is also feasible to use mains water.

Like all dewatering devices, the performance of the V-Fold

depends on the composition and quality of feed slurry. In

general, it produces a filter cake with slightly higher moisture

content. Slurry feed rates are up to 1500 litresih, and filter cake

discharge rates are up to 300 litres/h, depending on the process it

is serving. Table 1 lists the performance of the V-Fold filter in

various actual applications.

www.filtsep.com

Figure 2: Watewater from winery is fed into V-shaped cavity.

The Roland Flat winery (part of the Orlando-Wyndham

Group producing Jacob’s Creek wines) in Barossa Valley, South

Australia was the first V-Fold customer. It has subsequently

bought three more V-Folds for its other Orlando sites. One of its

winery services managers, Jim Oxby, described its experiences

with it. “it’s maintenance free. We only have to clean it down

thoroughly when we want co shut it down for more than one or

two shifts. Day to day we just hose it down around the rollers

and leave it at that.”

In addition to taking much of the ‘hassle factor’ out of sludge

dewatering, V-Fold customers have also gained substantial

bottom line benefits. In a variety of applications it is reported to

have paid for itself in 8-12 months through savings in manpower,

maintenance and operation costs.

Optimum Performance 6; Minimum Cast

The unique V-shaped belt is not only able to handle variations in

slurry parameters, but also offers a number of additional

advantages to optimize performance and minimize operating

costs and operator attention.

(i] Slurry feed automation is easy and ensures the rate of slurry

feed adjusts according to its composition. An ultrasonic

lcvei detector over the feed cavity controls the feed pump

rate to maintain the desired slurry level in the feed cavity

This indirectly controls the polyelectrolpte to feed solid

ratio, and allows good dewatering despite wide feed

variations. h4any industrial ~~ppiic~ltioIls find this makes the

(ii)

(iii)

(iv)

The Design Challenge

Paul Day founded Dayco in 1992 as a consultancy designing and installing effluent treatment systems for small to medium sized businesses. According to Paul Day, “In the first five years of business we saw so many customers getting frustrated with the ‘hassle’, downtime and cost of operating their belt filters. Food processors, wine producers, printers,

. . metal mushers I;OLI name it - whatever the industry, they were all facing the same problems. In I997 a customer challenged us to come up with a design that would do away with the problems and costs of coping with variable slurry

comp(~sition and flow rate.” “The old saying that genius is 99% perspiration and only

I % inspiration certainly proved to be true when we came up with the V-Fold. Although the concept came to me simply by

wrapping a piece of paper around a pencil, it took three years of prototyping, testing and refinement to turn it into a commercial reality. When we launched the V-Fold in 2000 we quickly found a market niche in companies with effluent processes producing up to 30 000 litres of slurry a day We’ve already sold more than 20 V-holds into 3 wide range of industries and applications including dewatering slurries from settling pits, clarifiers and DAF systems.”

difference between needing frequent operator attention to

adjust slurry and polyelectrolyte feed rate and leaving the

dewatering filter to run almost unattended.

Some processes such as dissolved air notation (DAF) can

discharge slurry directly into the V-Fold feed cavity and do

away with the need for intermediate storage to smooth the

inevitable slurry variations (Figure 3). -Many industrial sires

find slurry storage tanks are prone to solids settling out

and odour-generating bacterial growth. Also, agitator

shear can break floes formed in upstream processes and re-

flocculation before the dewarering device becomes more

difficult.

The combination of horizontal and vertical rollers make the

fiber belt ‘self-tracking’, so no tracking devices are needed

on the V-Fold.

Its simple design and slow moving belt (typically 2-J mimin)

mean power reqL~ir~rneilt is low (0.37 kW drive) and little

Industry

Winery

Printing

(cardboard]

Tannery

Slurry eource Slurry feed rate”) Slurry dry Filter cake (litres/h) solidslll I%) dry solids(‘l (%)

Slurry pumped from IDDO 5 >20

settling pit floor to

‘day tank’.

Slurry pumped

directly from DAF overflow to V-Fold

feed cavity,

Slurry pumped directly from clarifier

underflow to V-Fold

feed cavity.

600 >2D

600 10 20

Upstream process route

Lime slurry neutralization

of winery wastewater

then settling in settling

pits.

Coagulation and

flocculation of ink-

wastewater then DAF.

Lime slurry neutralization

of chrome wastewater then settling in a clarifier.

[I) Typical values - actual performance depends on prevailing operating conditions.

Filtration+Separation October 2002 19

featurearticle

Waste water I)

Polymer dosing

I,-xL--

a- Clarifier

7 V-fold filter

Fifes = E+-ppJ!e Filtrate and belt wash return

Figure 3: A typical process flow on a clarifier underflow.

maintenance is needed. The filter belt is the main wear

component and needs occasional replacement. This is a

simple task which takes approximately 45 minutes.

Case Study: Printing Ink Slurry An Australian cardboard packaging manufacturer using water-

based inks for printing treats its wastewater with coagulants, a

polyelectrolyte and ‘antifoam’ to flocculate the ink. These are

then removed by an induced air flotation (IAF) process that

produces clean water for discharge to sewer, and ink slurry. The

effluent plant originally used a tank for intermediate slurry

storage and a plate and frame filter press to generate a filter cake

for disposal. However, the plate and frame filter was expensive

and inconvenient to run because it needed to be emptied almost

every shift - occasionally at inconvenient times when the

operator was busy. Also, its filter cloths quickly blinded despite

in-situ cleaning and required removal for washing.

The plate and frame filter was replaced with a V-Fold filter

model SS600. The ink slurry is now pumped directly from the

Figure 4: Filter cake produced from effluent treatment of printing wastewater.

flotation unit to the filter, where additional polyelectrolyte is

dosed into the pump suction to assist filtration. The feed slurry

produced by the factory is highly variable in flow rate and solid

content. Also, the IAF unit occasionally floods when waste-

water overflows with the ink slurry. Despite these variations the

V-Fold produces consistently spade-able filter cakes. In general

the feed slurry is at 2-5% dry solids, while the generated filter

cake contains more than 20% dry solids. The V-Fold runs

whenever the IAF operates, which can be up to 20 hours a day.

Typically 80 litresih of filter cake is produced at the factory

and removed from the site with other dry waste for landfill

disposal (Figure 4).

Factory personnel estimate the V-Fold paid for itself within

12 months by reducing operator workload and eliminating the

cost of laundering filter cloths. They are particularly happy

with the V-Fold’s ability to operate continuously with little

supervision and that the intermediate slurry tank was taken out

of the circuit.

V-Fold Goes International Its simple design and forgiving nature have already made the V-

Fold folding belt filter press a success in its home country of

Australia. Having scaled up production capacity Dayco is now

equipped to supply the wastewater treatment market

internationally. The first step is to launch V-Fold in the USA

and UK. To this end Dayco have set up exclusive marketing

licences wirh Simon-Hartley of the UK and Ashbrook Corp of

the USA, both established market leaders in slurry dewatering.

Simon-Hartley’s market development manager Paul Giles is

confident about the prospects for V-Fold in the UK,

“Traditionally the wastewater treatment industry has focused

on providing large-scale capital plant required by municipal

sewage treatment works and large scale manufacturing

industries. Few developments have specifically addressed the

needs of small to medium sized operators. The V-Fold is a

timely and welcome innovation for such businesses increasingly

facing tighter environmental controls and escalating costs of

waste disposal.”

Paul Giles is also confident about the financial benefits it will

yield. “Businesses processing waste effluent on-site, with a

conventional small filter press, will see savings from investing in

a V-Fold” he explains. “Small to medium sized businesses

currently relying on off-site processing and disposal will see even

greater savings. For a business currently producing one to three

tankers of liquid waste a week we expect the V-Fold to pay for

itself comfortably in the first year of operation. ” 0

Contact: Paul Day, technical director, Dayco Pty Ltd,

25 Myrtle Avenue, Myrtle Bank, SA 5064, Australia.

Tel: +61 8 8338 1823; Fax: +61 8 8338 3532;

E-mail: daypaul@ozemail.com.au; Website: www.vfold.com.au; or

Paul Gilas, market development manager, Simon-Hartley, Garner Street, Etruria. Stoke-on-Trent,

Staffordshire. ST4 7BH. UK. Tel: +44 i7B2 202300; Fax: +44 1782 260534;

E-mail: paul.giles@uk.ashbrookcorp.com; Website: www.simonhartley.com

20 October 2002 www.filtsep.com