Phosphorus Removal:

Advanced Chemical

Dosing using Real Time

Control (RTC) systems

Stuart Ainsworth RTC Optimisation Specialist

SWIG workshop November 26th, 2014

I. Chemistry of P removal

II. General Site Characteristics

III. P-RTC compared to existing methods

IV. Equipment Reliability / Suitability

V. Case Studies

2

Chemistry of Phosphorus Removal

Clear link between molar ratio and % removal ortho P

Jar tests limitations

Mixing important but NOT as critical as clean water applications

Knowing the concentration of ortho P is very important for accurate dosing!

11/12/2014 HACH LANGE 3

0 10 20 30 40 50 60 70 80 90 100

Mo

lar

Ra

tio

% Ortho P Removed

Ferric P Removal Efficiency vs. Aluminium

Ferric Sulphate Real Resultsat Burscough

Ferric Sulphate Jar test

Aluminium Sulphate Jar Test

I.

Ferric Sulphate Removal at

WwTW

Validated results from alternative WwTW & chemical supplier

Good Correlation

11/12/2014 HACH LANGE 4

R² = 0.9958

R² = 0.9579

0 20 40 60 80 100

Mo

lar

Ra

tio

% Removal

Validation check of Precipitation Chemicals

Ferric Sulphate 12.5%

Aluminium Sulphate 5.4%

I. Chemistry of Phosphorus Removal

I. Chemistry of P removal

II. General Site Characteristics

III. P-RTC compared to existing methods

IV. Equipment Reliability / Suitability

V. Case Studies

5

There is NO credible link between flow and

load (when considering all conditions).

Flow paced dosing systems are NOT in

control!

Establishing an effective storm suppression

dose is very difficult.

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There is a credible link between time and

load BUT there are very significant variations

in load for any given time.

Profiled dose systems do not take into

account “load to be removed”.

Profiled dose not account for profile changes

due to changing flow conditions.

II. General Site Characteristics

Based on real data from

typical domestic catchment

(P.E. circa 30K)

Note: minimum & maximum

concentrations very close

Slight increase in flows can

lead to extended “no-dose”

events

True load profile is much

more dynamic than typical

fixed profile dose systems

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II. General Site Characteristics

Less load is required to be

removed for any rain event.

The molar ratio required is

reduced through lower %

removal requirement.

Real time control can exploit

this for chemical savings.

Real time control focus on

load peaks.

11/12/2014 HACH LANGE 8

II. General Site Characteristics

Demonstrates the problem

of when to reinstate

“normal” conditions after

storm suppression dose.

Shows how static profiled

dose can be unsuitable.

Much wider dynamic range

to accommodate peak

minima & maxima.

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II. General Site Characteristics

Scope of Presentation

Chemistry of P removal

General Site Characteristics

P-RTC compared to existing

methods

Equipment Reliability / Suitability

Case Studies

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P-RTC compared to existing methods

The correct amount of precipitant is added at the correct time

True site chemical efficiency is taken into account

Establishing an effective storm suppression dose is very difficult. This is automatically

controlled with P-RTC

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Realtime flow

(flowmeter)

Measured [orthoP]

orthoP % removal

Molar ratio Fe:orthoP

Precipitant Flow rate

orthoP target

“Beta” curve

Load to be removed

Standardized software for P-Elimination (open / closed-loop)

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waste water

precipitationagent

Dosing

pump

Precipitation Process

QPrecPO4-P

X

Qprec

PO4-Pload

Q

PO4-P

Degree of elimination

waste water

Precipitationagent

Dosing

pump

Precipitation Process

QPrec PO4-P

Set point

Qprec

PO4-Pload

X

Q

Advantage

High process control

Set point

w = Limit - cSS · cP,SS - safety

Requirements

PO4-P and flow [Q] online measurements

Advantages

Immediate reactions to load changes

Easy to adjust

Set point

Biological P-elimination to be considered

Requirements

PO4-P and flow [Q] online measurements

Scope of Presentation

Chemistry of P removal

General Site Characteristics

P-RTC compared to existing

methods

Equipment Reliability / Suitability

Case Studies

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Instrumentation Features

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Proven method for ortho P analysis

***** Exclusive use of “TMS” filter system – game

changer on crude sewage analysis! *****

Very secure “fall back” position based on bespoke load

analysis / look up table as part of the commissioning

process.

Suitable for all chemical application points / treatment

stages.

Opens the opportunity to comply with ultra low P and

metal consents using conventional dosing.

Simple to Retro-fit

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Completely integrated solution

Standardised system

No. Task Status

1. Definition of control algorithm ✓ Done

2. Programming of control

algorithm ✓ Done

3. Implementation on hardware ✓ Done

4. Testing of software and

hardware ✓ Done

5. User interface ✓ Available

6. User manual ✓ Available

7. Backup stages ✓ Available

8. Communications interface ✓ Available

9. Setting of the plant-specific

parameters

During

commissioning

Standardized hardware for P-Elimination

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Flow

Precipitant

dosing

PHOSPHAXsc

On-line analyzer

SC1000

parameterization WTOS module

(P-Module)

Standardized hardware for P-Elimination

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Flow

Precipitant

dosing

PHOSPHAXsc

On-line analyzer

SC1000

parameterization WTOS module

(P-Module)

PLC

SCADA

12.11.2014 HACH LANGE 18

Standardized Software for P-Elimination

Inlet sample preparation - Key to sustainable measurement

19

Scope of Presentation

Chemistry of P removal

General Site Characteristics

P-RTC compared to existing

methods

Equipment Reliability / Suitability

Case Studies

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21

Population 17,000 pe

Flow 800 m3/hour Maximum

Consent limit 2mg/l annual average

Effluent average concentration 0.8 mg/l

Coagulant Ferric sulphate

Max. dose rate 198 l/h

Dose rate 30 l/h fixed speed by hand

Open loop control system: Northwest UK

22

Savings:

20,000 £/ year 30 l/h

16,5 l/h

45%

red.

Before

RTC

After

RTC

ROI 14 months

Open loop control system: Northwest UK PO4-P concentration

Closed-loop control system: wwtp Flieden, GERMANY

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Size 15,000 pe

Ptot limit 2.0 mg/l

Dosing point Inflow aeration

Precipitant FeCl3

Ø dosing rate 6.5 l/h based on daily lab measurement

Characteristics Exceeding limit due to seasonal load peaks from juice

production

Target Maintain effluent limit Ptot

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0

1

2

3

4

5

6

7

8

10.02.2011 15.02.2011 20.02.2011 25.02.2011 02.03.2011

Pd

os [

l/h

] &

Q

[(m

³/h

)/1

00

]

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

2

PO

4-P

[m

g/l]

Pdos Qin/100 PO4-P

Closed-loop control system: wwtp Flieden, GERMANY

minimum dose

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Safe process control

Reduced precipitant consumption by 60% (7,000€/y)

Simple installation

6.5 l/h

2.6 l/h

Before With RTC

60%

7.000 €

reduced

Closed-loop control system: wwtp Flieden, GERMANY Results

Summary: P-RTC compared to existing methods

The correct amount of precipitant is added at the correct time

True site chemical efficiency is taken into account

Dosing can stop immediately when rainfall dilution allows

Protection against

overdosing and metal noncompliance

alkalinity issues

extreme flow events (extended dry periods)

Opens up the opportunity to comply with more stringent Consents

11/12/2014 HACH LANGE 26

Thank you.