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Optimization through Solids Measurement

Heli Karaila product manager

Measurements Metso

Timo Riippa Metso partners

Instrumentation, Process Control & Automation Conference

Brisbane 2012

Optimization through Solids Measurement

• Sludge general

• Optimization possibilities with the online measurements

• Metso Waste Water Sludge treatment online measurements

Metso TS

Metso LS

The wastewater

treatment industry

has a mandate to

protect the water

environment.

In fulfilling this

mandate, wastewater

treatment plants

produce large

quantities of residual

solids, commonly

referred to as sludge.

Amount of the Sludge in the

waste water plant• Each reduced BOD7 kg creates 0,7 –

1,2 kg solid material in the waste

water plant. www.ympäristö.fi

• Generally,solids production rates

range between 0.2 and 0.3 kg/m3 of

wastewater treated Turovskiy I. and Mathai P. ( 2006)

Solids removal is needed in

the waste water plant

• Solids removal is normally defined

in the waste water plant’s

environmental permission as one of

the key parameters ( Suspended

Solid in the leaving water )

• The only way solids can be

removed from the waste water plant

is via sludge dewatering

• Solids circulation should be avoided

inside the plant

Costs of the sludge removal

• The cost for treatment + disposal of

sludge in European countries has

been estimated to reach, on average,

approximately 500 € per tonne of dry

mass, according to the type of

treatment and disposal . www.iwawaterwiki.org

• The sludge management costs are

about 40 to 50% of the total

wastewater treatment costs. Turovskiy I. and

Mathai P. ( 2006)

Waste water treatment planWaste water treatment process

Sludge treatment process

Optimization possible only with

online measurements

• the laboratory based measurement

are always too late and it is not

possible to create control on the basis

of the laboratory measurements

• There is a need for a reliable online

measurements

There are following technologies in mostly in

use for measuring solids online in the

waste water area:

• Optical ( scatter, absoption)

• Optical that utilized compined signals

• Coriolis

• Torque

• Microwave

Example of the Maintenance needs of

scatter, absorption measurements

Instrumentation Testing Association suspended Solids and Turbidity

measurements maintenance benchmark study MBS99SS-

001p (1999 )

Sludge treatment online measurement

benefits / optimization

• Sludge Pumping from Primary & Secondary

Sedimentations

• Digester Feed

• Dewatering

• Dewatered sludge “Dry Cake”

• Reject water TSS measurement

Sludge Pumping from Primary &

Secondary Sedimentations

12

Sludge pumping control on primary

& secondary sedimentations

• Target:

– Keep total solids of the sludge

high as possible from the begging

of the sludge treatment process

by measuring total solids accurate

way and controlling the pumpings

based on the measurements

• Results:

– Increased pumping capacity

means higher water processing

volumes and postponed

investments

– Harmonized operations

– Optimized quality

– Optimized and reduced costs of

the sludge pumping

13

Digester Feed

15

Digester Feed

• Target

– maintain optimum sludge

solid to digesting process

• Results:

– Improved process control and

significant savings

– Increased sludge digestion

time to produce more biogas.

– Decreased heating energy

>> more electric energy can

be produced and transferred

for the aeration of biological

reactors

16

Dewatering

18

Dewatering• Target:

– Accurate measurement for

polymer dosage- and

dewatering equipments

control

• Results:

– Reduced polymer costs

– Stabilized quality of both the

dewatered sludge and the

centrate water.

– Reduced sludge

transportation costs

– Improved incineration

efficiency when the sludge is

burned

– Lowered energy consumption

and maintenance costs of

dewatering equipment19

More than 20% savings on polymer costs

• Optimum polymer dosage can

be defined only by a reliable

solid content measurement

and saving of 20% in polymer

costs can be achieved.

• Depending on process

capacity, the return of

investment can be surprisingly

short.

• In middle size WWT plant (PE=

500 000) ROI can be just a

months.

20

Feed sludge ~ 2%TS

+ polymer

Centrate water

< 0,1 TS%

Cake solids

~ 25 TS%

Dewatered sludge “Dry Cake”

21

Dry Cake• Target:

– Accuracy total solids results for

dewatering- and incinerator control

• Results:

– Efficient combustion of the

wastewater solids while maintaining

fossil fuel consumption.

– Operator can proactively adjust the

feed rate of both the natural gas and

the fuel oil based on the incoming

solids of the sludge.

– Significant energy cost savings.

– A new higher pressure sensor model

for pressure rating ( PN100 / Class

600 / JIS63K) available

22

Reject water TSS measurement

Laboratory measurement is not enough

0

1000

2000

3000

4000

5000

6000

30.11.10 0:00 5.12.10 0:00 10.12.10 0:00 15.12.10 0:00 20.12.10 0:00 25.12.10 0:00 30.12.10 0:00

Mittari Labra

0

500

1000

1500

2000

2500

3000

3500

19:12 0:00 4:48 9:36 14:24 19:12 0:00

Mittari Labra

Quality control of

centrate water

based on infrequently

taken lab samples

is not adequate

Lab sample represents

centrate quality at that

specific moment:

- After a half an hour

the situation can be

completely different!

mg/l

mg/l

Metso LS Laboratory

online measurement Laboratory

24

Finding out the optimum polymer dosage

2011 TRa25

– Polymer flow – Sludge flow – Total suspended solids

Polymer saturation point

Polymer flow

Sludge flow

Total Suspended Solids

Online polymer test possible

Control application feedback

based on Metso LS measurement

26

0

500

1 000

1 500

2 000

2 500

3 000

21.1. 22.1. 23.1. 24.1. 25.1. 26.1. 27.1.

mg

/l, kg T

S/h

0,0

2,0

4,0

6,0

8,0

10,0

kg P

E/ t T

S

TS-kuorma LINKO 4. REJEKTI SS Polymeeri

0,0

2,0

4,0

6,0

8,0

10,0

12,0

0,0

500,0

1 000,0

1 500,0

2 000,0

2 500,0

22.2. 23.2. 24.2. 25.2. 26.2. 27.2. 28.2.

kg

PE

/ t T

S

mg

/l, k

g T

S/h

TS-kuorma LINKO 4. REJEKTI SS Polymeeri

Manual control Automatic control

--- sludge to drying --- polymer --- total suspented solids

Automatic control : Polymer dosage is managed on the basis

of centrate quality within given limits

Control example- control decreases polymer flow whenever possible

2011 TRa27

Control auto days days

Saving possibilities by reject

water TSS minimizing

- Minimize the circulating material

- Dewatering costs minimizing (

polymer , dewatering unit costs )

- Circulating solids needs pumping,

chemicals etc. again in the plant

- Circulating material is challenging for

the wastewater plant

Sludge online measurements

Metso

• Microwave technology ;

– Metso Total Solid

measurement ; Metso TS

• Laser and LED technology ;

– Metso Low Solid

Measurement; Metso LS

Date Author Title30

Benefits gained using microwave

technology

• A most representative measurement -

transmitter measures the time of flight of a

microwave signal in all the process

medium.

• Microwave measurement does not react

to changes in the composition of solids.

• Reliable single-point calibration

• Practically maintenance-free

• Measurement range 0-40 %

Supreme Measurement Accuracy

• Excellent correlation to

laboratory results.

• Reduced need of

laboratory analyses.

• Typical fluctuation of

primary sludge solids.

• Solids measured and

controlled independently

of discharge sequences.

31

Metso LS

- total suspended solids measurement• Total suspended solids 0–

5000 mg/l – if over 5000

please contact Metso

• Entrained air index

Customer statement:

”The first measurement

system that really works in

centrate water”

2011 TRa32

Metso LS

for reliable centrate TSS measurement

• So far no reliable measurement in the market

– Accuracy & reliability have been major problems

• It is very important to know the quality of centrate water

– For choosing the right polymer type

– For dosing the polymer economically

– For process monitoring

• Laboratory follow up is not enough

– Based on laboratory it is not possible to tune polymer dosing

successfully

• Reliable measurement enables big savings in

– Polymer dosage

– Centrifuge usage

– Management of plant internal solids cycle

Date Author Title33

Metso LS: excellent follow-up results

Date Author Title34

Online measurements key to the

optimization of the waste water plant

• Today there are reliable online

measurements available for the

wastewater optimization; example

Metso TS and Metso LS.

• With the online measurements the

optimization / cost reductions are

possible