INNOVATION IN SLUDGE DEWATERING

Pascal GINISTY

Milan – The 8th of February 2019

Institut de la Filtration

et des Techniques Séparatives « Association Loi 1901 » created in 1981

Technical Center (SME)

Industrial Members – Cross-sectorial activities

Liquid-Solid separation expertise

Scientific

and

Technical

Research

Suppliers End-users

Suspensions and media characterization

Filtration (from sieving to reverse osmosis),

settling, flotation, cycloning, centrifugation;

Conditiong, filter aids, adsorbents

I.F.T.S. 4 km from Agen

Middleway between Toulouse / Bordeaux

International Filter

Testing Services

IFTS Inc. à New York

IFTS Asia à Shanghaï

2

Laboratory of Measures & Characterization (LMC)

European Filter Testing Center (CEEF)

Technological Consultancy/Expertise

Water Analysis Laboratory (LAE47)

Membrane Separation Pôle (PSM)

Training and E-Learning

Research and Technical Studies (CEOPS)

Design and manufacture of test equipment

3

NEW ISO TC 275 (Paris, November 2013)

« Sludge recovery, recycling, treatment and

disposal

CEN TC 308 (1995) “Sludge

characterization and management

Activities in sludge standardization

Background

4

Sludge processing

Sludge management is a sustainabily

problem which should be suited to local

context

o Minimization of the amount of

sludge to be handled, stored and

transported (stricter regulations vs

sludge routes) → sludge of high

dryness required

o Maximization of materials recovery

(P, N, metals, biomaterials) / energy

→ sludge of high quality required

o Minimization of impact on

environment (decrease of polymer

demand, energy consumption…)

Cost of sewage sludge treatment from

5000 to 200000 PE account for 50% of

total operating costs with approximately :

o 15% for polymer consumption

o 55% for water removal

o 30% for dry solids disposal

Market Europe (2006) : 28% belt presses – 23

% filter-presses - 41 % centrifuges - 8 % others

Technical innovations and development for : Higher performances of machines :

Clarification level (high capture ratio – decrease of charge of return waters)Dewatering levelProductivity (continuous mode, automation…)

Better operating conditionsLabour reduction (maintenance, supervision, CIP)Labour safety (closed environment, inerting, hybrid machines)Water consumption decrease Energy efficiencyPolymer consumption decreaseNoise level

Emerging markets Digested sludges Industrial sludges (eg : waterworks sludge….)

Drivers of innovation

Classical filter-press Membrane filter press

Better quality of filter cloth

Full automation (cake discharge, cloth washing)

Staff safety

Closed filter-press

Leaks recovery systems

Measurement of mass balance

Special filter-press Vertical filter-press : continuous filter-press (industrial sludges)

Improvement of classical equipments

Classical belt press Even sludge distribution systems (weir, plate, paddle wheel…)

Faster belt speeds

Higher rolls number and decrease of rolls diameter

Roll coating : protection against belt wear

Automation (SS meter, flow meter, floc quality…)

Closed belt press (odor control)

Water consumption reduction

More Compact systems

Special belt press Vertical belt press, 2 to 1 systems : belt thickener + belt press

Improvement of classical equipments

Classical screw centrifuge Rotor high performances

New geometries of screw (HP)

Liquid ring modification during operation

Screw protection against abrasiveness

Brake and fluid energy recycling (energy savings)

Automation (panel and remote control, holograms)

Noise reduction

Decrease of polymer demand (hydraulics)

Special screw centrifuge Increase of centrifuge acceleration until 9000 g

Vertical screw centrifuges (industrial sludges)

Improvement of classical equipments

Rotary press Modular system - Expandability

Full automation

Low energy demand

Self cleaning (5 min / say)

Low maintenance

Other equipments

Classical screw press Higher productivity (to have more markets)

Energy efficiency

Easier maintenance

Automation, remote control

Closed press (odor control)

Water consumption reduction

Progressive decrease of filtration rate (several parts)

Special screw press Inclined machines (10-15°)

Other equipments

Disc press Higher productivity

Energy efficiency

Reduction of cloth clogging (autocleaning)

Noise and odour reduction

Decrease of chemicals consumption

Compacity

Other equipments

Piston press High dewatering level

High level of automation

Goal : sludge autothermicity

High flexibility

Low noise level

Low energy consumption

Other equipments

Lamellar centrifuge Spiral Plate technology

Acceleration until 4000 g

Low turbulences (laminar)

Semi continuous

Application for some industrials sludges

Laminar flow centrifuge Acceleration until 7000 g

Continuous Equipement

High clarification and dewatering expected

Low shearing

Low turbulences

Application for some industrial sludges

Other equipments

Sludge pretreatment : conditioning

14

Innovation in products Synthetic polymers

Increase of MW to decrease linear polymer consumption (1980)

Development of medium MW branched polymers to increase drainage rate of BP (1990)

Development of high MW branched products for centrifuges (2000-2010)

Development of new emulsions for high drainage capability and floc strength for new dewatering equipments (screw press, piston press) : from 2010 to now

Future : Lower mixing time, good reflocculation, increase the structure degree, improve of dissolution, biodegradability, better handling (beads vs powders)

Other products Coagulants : products without residual Al and Fe

Biopolymers : starches, tannins, alginates, chitosan, Opuntia ficus Indica,,,

Lime : delayed reactivity quick lime, highly concentrated lime milk

Additives : cellulose powder or fibers, MgO, ashes…

Sludge pretreatment : conditioning

15

Mechanical conditioning (®SLG Orege)

Sludge pretreatment : thickening

16

Improvement of techniques for sludge concentration with very low energy and chemicals demand in order to reduce the size of dewatering equipment and associated costs (energy, chemicals demand) and to reduce odours

Gravity thickener

Flotator

Belt thickener

Disc thickener

Drum thickener

Screw thickener

Drainage tube

Vacuum beltthickeners

Innovation in lab devices

17

Need of innovative lab tools to evaluate sludge properties to be treated by mechanical thickening and dewatering and associated methods/standards

Bootest for sludgeconditioning (EN 14742)

Flottatest for floatability

Filtration-compression bench for filterability (EN 14701-2)/ compressibility

(EN 14701-3)

Specific column for settling velocity(EN 140702-3)

SSVI (EN 14702-2) Lab centrifuge for screw decanters

CST (EN 14701-1)

Lab filter-press

Automated test « torchon » for piston

press

Cake adhesion to filtercloth

Innovation in parameters

18

New parameters for a better description of sludge properties or treatability -Others to be invented (floc strength, floc cohesion, sludge plasticity…) or to be simply defined (floc size, floc shape)

Fi 3 / 8 g h r / l

Flowability index for liquid sludgedefinition (< 30 Pa) : EN 16720-1

Rejected drainage Eg < 2.2 Bad drainability kinetics

Medium drainage 2.2 < Eg < 6 1 or 2 parameters not

accepted

Good drainage 6 < Eg < 10.5 All parameters values are

accepted

Limit drainage 10.5 < Eg < 12.3 To be analyzed carefully

according the case

Rejected drainage Eg > 12.3 No flocculation

Drainability index (EN 14701-4) for treatment

in a belt thickener

Innovation in parameters

19

𝑆 =𝑎𝑡

𝑏 + 𝑐𝑡=

𝑎

𝑐 +𝑏𝑡

𝑡

𝑆(𝑡)=

𝑏

𝑎+

𝑐𝑡

𝑎 𝑆∞ =

𝑎

𝑐

y = 0.0397x + 112.27R² = 0.9997

0

200

400

600

800

7000 9000 11000 13000 15000tim

e/d

ryn

ess (

s/%

)

Time (s)

Number

of

sludges

Full scale

Dryness

Average SD

Limit

Dryness

Average SD

Ratio Centrifuge

Limit dryness

tested (%) (%) (%) (%) (%)

Activated sludges 17 19.9 2.2 28.4 5.8 70

Digested sludges 8 24.8 4.6 34.1 7.6 73

Waterworks sludges 6 25.5 6.8 48.3 8.3 53

Industrial sludges 14 18.5 4.6 27.0 7.2 69

Correlation between sludge dewaterability and behavioural

sludge property (limit dryness NF 97001-1 - 2018)

Conditions : flocculation according EN14742, filtration-

compression with plug, pressure filtration : 4 bar, cake

thickness : 5,5±0,5 mm, loss of solids : < 10%

Comparison with full scale centrifuge machines for different

sludgesLIMIT DRYNESS represents the sludge

potential of mechanical dewatering

independently of the equipment : basis for

warranty given by suppliers to take into account

sludge origin, property and variability

20

The classic association of dewatering processes

Centrifuge process can not dewater completely the cake (mainly due to

capillary effects).

To completely dry the cake Thermal energy.

Coupling of physical processes : hybrid process (synergy expected)

Centrifugation

/ filtration Thermal

drying

Centrifugation

Thermal

drying

HYBRID SYSTEMS

Filtration

Hybrid machines : centrifugation + convective drying

Vapour + product

outlet

Deflector cone

Hot vapour

inlet

Centrate

Feed

HYBRID SYSTEMS

Thermal assisted filtration

Hybrid systems

Filter-dryer

Hybrid systems

• Feeding pump

• Polymer dosing

• Filterpress frame (from 0,15 to 1,5 m)

• Plate pack

• Core washing/blowing

• Heating equipment (95°C)

• Vacuum equipment (30-50 mbar)

• Discharge conveyor

• Recovery of condensates

Filtering centrifuge (3000 g) + microwave (1200 W)Hybrid systems

Microwave + centrifugation with filter

cloth : drying, extraction1. Filtering

centrifuge (C)

2. Magnetron (MW)

3. Wave guide

4. Condenser

Cells destruction under MW

UPLC

analyses

Extract

collect

+MW + Centri

Before After 80% of volume reduction,

polyphenols recovery in liquid

extract

25

ElectrodewateringHYBRID SYSTEMS

Dry Matter :

1-3%w/w20-35%w/w 40-47%w/w –

0,25-0,6 Kwh / kg

26

ElectrodewateringHYBRID SYSTEMS

27

Electrofiltration (without chemicals)HYBRID SYSTEMS

Sludge Initial DS

(%)

Without field

(%)

With field

(%)

Drilling 10 28 50

Biological 3 10 55

Hydrocarbons 10 28 73

Platform for innovation testing

28

• IFTS platform : first independent test center in Agen (France) ,

inaugurated the 6th of November 2018 to assess performances at

industrial scale

What will it be possible to do in this new center ? Evaluation of technologies

(e.g : a way to compare performances of different centrifuges on the same basis : urban sludges)

Qualification of equipments, Benchmarking of technologies

Feasability and optimization studies

Test of new separation units and innovations on equipments,

Endurance tests, Energy consumption studies

Water reuse strategies assessment

Validation, assessment, certification of performances

Test of remote control, automated systems, new sensors

Water and sludge analysis, training

Research : Platform for testing/demonstrate innovative systems for water and/or sludge treatment

Standardization : interlaboratory tests on different types of fresh water(s)/sludge(s) with stable properties

Long run tests up to one year

5-Conclusions

29

• The history of sludge thickening/dewatering points out a lot of innovative systems developed for

decades with its own advantages/drawbacks

• New technical challenges as now, sludge treatments don’t only aim to reduce volumes but also to

recover materials, nutrients, energy

• Also, environmental challenges are important to reduce chemicals, noise, odors, energy and water

consumption

• Hybrid systems have a future as it is required to push the limits of mechanical dewatering

• Cost reduction is always the main driver

• Questions are always remaining for operators :

What are the key indicators of treatment (sludge and flocs properties) ?

How to predict performances ? How to select the most adapted polymer ?

How polymer demand changes with sludge variability and operating conditions ?

Who is responsible of bad performances : the machine ? The sludge ? The operator ?

• A step by step approach is necessary to limit final tests at full scale (time and staff consuming)

• Necessity to test innovations of suppliers in full scale test platform in comparable conditions

• Standardization is a tool to share good practices, experiences, methods

• In ISO TC 275 program, a guide on « thickening and dewatering » (TR 19995) is under progress and

nearly finished. We need contributors for conclusions and future trends and innovations.

• Volunteers ?

30

Any questions ?

Thank you for your attention