Improving Phosphorus Removal with Magnetite Assisted

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?