Improving Phosphorus Removal with

Magnetite Assisted Settlement.

BioMag and CoMag

Adam Brookes, Bernie Glanville, Stephen Tomlin, Jane Youdan.

Anglian Water, Northumbrian Water, Wessex Water.

The BIG P conference, Manchester, 5th July 2017

National Collaborative Project

Improving Phosphorus Removal with Magnetite Assisted Settlement

Content:

• Process background – the use of magnetite

• Trial sites and results

• Common findings

Process Background

• Magnetite assisted settlement

• Both BioMag and CoMag can be retrofitted

• Magnetite recovery system

• Co-Mag:

– Use of magnetite to assist with settlement after secondary

treatment (trickling filters or activated sludge)

– Separate floc tank and settlement tanks

• BioMag:

– Addition of magnetite into activated sludge

– Use of existing FST

• Shear mill

• Magnetic recovery drum

• Return of magnetite to

process

• Removal of excess

sludge

Magnetite Recovery

System

Trials

• Part of the AMP6 national phosphorus removal technology trials.

• Market Harborough STW, Anglian Water. CoMag

– Oxidation ditch, followed by CoMag, PE = 23,000

• Esh Winning STW, Northumbrian Water. Co-Mag

– Trickling filters, PE = 5,000 (100% of flow)

• Bowerhill STW, Wessex Water. BioMag

– ASP, PE treated = 4,000 (50% of site flow)

CoMag

Market Harborough STW

Market Harborough STW

Overview of CoMag Process Installation

• CoMag installed post ASP, fed from feed/overflow chamber

Note: upstream chemical dosing for P removal to target of around 1 mg/L

Market Harborough STW

CoMag Installation

Market Harborough STW

Results of CoMag Trial

Influent total P

Average

(mg/l)

Effluent total P

Average

(mg/l)

Effluent total P

Min

(mg/l)

Effluent

total P

Max

(mg/l)

% removal

1.13 0.17 0.06 0.4 85

Market Harborough STW Summary

• The principal issues encountered during the trial were the

robustness and reliability of individual components that are

fundamental to successful and stable operation.

• Numerous problems with polymer make up and dosing system.

• Duty only on trial plant so single point of failure

• The performance of the clarifier was identified by EWT as being

deficient, limiting the overall performance of the plant

• Relatively high chemical use per volume treated and load

removed (polymer and ferric)

• Excellent performance when everything was working correctly

CoMag

Esh Winning STW

Esh Winning STW

Overview of Comag Process Installation

• Comag retrofit between the trickling filters and the humus tanks

• Diversion of flows post trickling filters into wet well then pumped

into package plant for ferric and caustic dosing

• Flow passing through several reaction tanks mixing with sludge

returns and polymer

• Flow passing into humus tanks for settlement and sludge

recovery

• Initial hydrostatic valves for desludge of humus tanks. Required

replacement with progressive cavity pumps due to blockages

• Sludge wastage and magnetite recovery process

• Note; no upstream chemical dosing for P removal

Esh Winning STW – Process Layout

Esh Winning STW

Impact of Process Stability on Final

Effluent

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

24

-May

31

-May

07

-Jun

14

-Jun

21

-Jun

28

-Jun

05

-Jul

12

-Jul

19

-Jul

26

-Jul

02

-Aug

09

-Aug

16

-Aug

23

-Aug

30

-Aug

06

-Sep

13

-Sep

20

-Sep

27

-Sep

04

-Oct

11

-Oct

18

-Oct

25

-Oct

01

-Nov

08

-Nov

15

-Nov

22

-Nov

29

-Nov

06

-Dec

mg

/l P

ho

sp

ho

rus FE total P

FE SRP

P 1

SRP 1

P 2

SRP 2

Level of Control

Esh Winning STW

The Good and the Bad

When stable, good settlement

and visibility within the humus

tankWear on PC pumps after 3

months

Esh Winning STW – Summary of Trial

• Major equipment failures during the trial; shear mill, transfer pumps and

dosing systems, resulting in an unstable process.

• When the plant was working correctly the final effluent quality was good

with total P levels down to 0.22mg/l and less.

• SRP values were less than 0.1mg/l unless the chemical dosing system

failed.

• If the dosing system failed the final effluent quality deteriorated within 24

hours.

• If the magnetite sludge was allowed to settle for more than 2 hours in

the tanks a vactor was required to re-suspend or remove it.

• Further investigation of the control and set up of the technology required

BioMag

Bowerhill STW

Bowerhill STW

BioMag Installation

• Aeration lanes

• PE approx. 4000

• Primary ferric ahead of the PSTs

• Additional secondary ferric dose into aeration lanes

• Polymer dose at outlet of aeration lanes

Primary

Settlement

Tanks

Sludge Storage Tank

ASP

Inlet Works

Final Effluent to River

Final

Settlement

Tank

RAS

BioMag® Unit… …

SAS

Shear Mill

Magnetic Drum

SAS Buffer Tank

Recovered

Magnetite

SAS

Addition of

magnetite

Bowerhill STW

BioMag Results

• Results (1 year period):

– Average Total P = 0.23 mg/l

– Average SRP = 0.10 mg/l

Bowerhill STW

BioMag Summary

• Other findings:

– The polymer did not show any impact on results

– Due to settlement of magnetite in the aeration lanes, it was

challenging to maintain the suggest magnetite:MLSS ratio

– Secondary ferric dose was critical to low P concentrations

• The BioMag system could be used to increase treatment capacity,

but this was not looked at as part of this trial.

Common Findings

BioMag & CoMag

Common Findings

• Total P concentrations of between 0.17 mg/l and 0.23 mg/l

• No benefit seen from use of polymer in BioMag

• Issues with reliability of process

• Some issues with replacement parts for magnetite recovery system

• Issues with settlement of magnetite

• Magnetite measurement method was not user friendly

Any Questions?