Chemicals Investigation Programme 2

Continuous backwash gravity sand filters: experiences from BluePRO ® installations

Victoria Wilson1, John Williams1, Adam Brookes2, Tina Popple2, Pete Vale3, Luca Alibardi3

1 Dwr Cymru Welsh Water2 Anglian Water3 Severn Trent WaterThe Big Phosphorus Conference, Manchester, 4th and 5th July 2017

National Collaborative Project

Drivers and Objectives

How low can we go?

Is 0.1mg/l TP actually achievable with current or future technologies?

The national P TWG coordinated 3 approaches to answering this

question:

• Novel Technologies

• Optimisation

• Innovation

We will be covering one of the Novel Technologies - BluePro

CIP2 Low P Programme – BluePRO® trials objectives

• Technology utilised in USA achieving low level P limits 0.02mg/l

• Gain experience and understanding of operating at full scale

• “Hands off” operation – to be optimised before sampling

• Extensive programme of sampling – stakeholders agreed

• Determine the long term efficacy

• Understand CAPEX & OPEX costs of running the BluePRO

• 3 Sites across 3 Water Company’s- Anglian, Severn & Dwr Cymru

(Dwr Cymru was monitoring only & new 0.5mg/l Total P consent)

• Assess maintainability & operability

BluePRO® unit - continuous upflow sand filter

• Sand continuously moving down • Clean water up

(Continuous backwash)

• Sand is airlifted up to wash box

• Phosphorus ferric complex is removed through the patented wash box

BluePRO® – The mechanism

• Dynamic combination of both co-precipitation and adsorption processes. • Ferric chemical is dosed into the patented rapid conditioning zone and then feeds into

a centra-flo upflow moving bed reactive sand filter. • Hydrous ferric oxide coated sand (HFOCS) is formed within the reactive filter• HFOCS being the adsorbent media coating the sand. • The sand is spherical shaped and has an effective size of 1.0mm with a SG>2.5

Scanning electron microscope image of the Blue Pro Centra-Flo sand particles; followed by the x ray fluorescence image of iron coating the sand particle; finally an x ray fluorescence image of the phosphorus adsorbed onto the Hydrous Ferric Oxide.

Company PE site Upfront

Process

No. filters Trial max flow

Anglian Water 1,837 Biofiltration 1 14.1 L/s

Dŵr Cymru

Welsh Water2,107 Biofiltration 2

28 L/s (14 L/s per filter)*

Severn Trent

Water11,000 Biofiltration 5

88 L/s (17.6 L/s per filter)

CIP2 Low P Programme – BluePRO® trial sites

* TSS issues on site restricted the flow to the filters

Dŵr Cymru – BluePRO® trial site

• 2 no. Blue PRO® filters

(5.9m2 surface area, 1.5m depth, 2.7m diameter) per filter

• Max 20 L/s ( 10 L/s per filter)

• Ferric sulphate dose: 10-15 mgFe/L

• *Inf. TP = 1.0 – 3.0 mg/L

• *Inf OrthoP = 70% of TP

• *Inf. Alk = 70 - 130mgCaCO3/L

• *Inf TSS = 20 - 30 mg/L

* Requirement from supplier

Severn Trent – BluePRO® trial site

Primary Settlement Tanks

Biological Filters

Humus Tanks

Nitrifying Submerged Aerated Filter

Deep Bed Sand Filters

Blue PRO Filters

Inlet Works

43

Final Effluent to River

Storm Tanks

Pre Trial Site Configuration

Trial Site Configuration

1 pH monitor

2 On line Fe monitor

Legend

Pumping Station

Pumping Station

Ferric sulphate dosing rig Reject pump

3

4

On line P monitor

On line Turbidity monitor

21

432

• 5 no. Blue PRO® filters

(each of 25m3, 3m diameter)

• Max 88 L/s (17.6 L/s per filter)

• Ferric sulphate dose: 10-13 mgFe/L

• *Inf. TP = 1.0 – 1.5 mg/L

• *Inf OrthoP = 0.3 – 1.1 mg/L

• *Inf. Alk = 70 - 130mgCaCO3/L

* Requirement from supplier

Anglian Water – BluePRO® trial site

Primary Settlement Tanks

Biological Filters

Humus Tanks

Blue PRO Filter

Inlet Works

Final Effluent to River

Pre Trial Site Configuration

Trial Site Configuration

Legend

Pumping Station

Reject tank

• 1 Blue PRO® filter

5.9m2 surface area, 1.5m depth

• Max 14.1 L/s

• Ferric sulphate dose: 12 mg Fe/L

• Inf. TP = 1.3 – 5.9 mg/L

• Inf. SRP = 1.2 – 5.3 mg/L

Ferric dosing

Programme sample

Results of BluePRO® trial – Summary of influent Total P

Company Average

TP

(mg/l)

Min TP

(mg/l)

Max TP

(mg/l)

Anglian Water 3.45 1.34 5.93

Dŵr Cymru

Welsh Water1.25 0.12 6.1*

Severn Trent

Water1.55 1.08 2.33

* Sampling was taken during a plugging event

Results of BluePRO® trial – Summary of effluent Total P

Company Average

TP

(mg/l)

95 %ile

(mg/l)

Min

(mg/l)

Max

(mg/l)

Averageremoval

(%)

Anglian Water 0.23 0.50 0.05 0.50 93

Dŵr Cymru

Welsh Water0.63(0.27)

2.49(1.33)

0.017.9*(1.8)

86.7

Severn Trent

Water0.19 0.60 0.06 0.82 88

* Sampling was taken during a plugging event. (Data without plugging event )

Dŵr Cymru – BluePRO® trial results

0

1

2

3

4

5

6

7

8

Co

nce

ntr

atio

n (

mg/

)

Soluble Reactive P (SRP)

Influent SRP

Effluent SRP

0

1

2

3

4

5

6

7

8

9

Co

nce

ntr

atio

n (m

g/)

Total Phosphorus (TP)

Influent TP

Effluent TP

Dwr Cymru – BluePRO® trial results

Severn Trent – BluePRO® trial results

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0

0.5

1

1.5

2

2.5

Effl

ue

nt

(mgP

/L)

Infl

uen

t (m

gP/L

)

Inf TP Eff TP

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0

0.5

1

1.5

2

2.5

Effl

ue

nt

(mgP

/L)

Infl

ue

nt

(mgP

/L) Inf SRP Eff SRP

Total Phosphorus (TP) Soluble Reactive P (SRP)

0

0.5

1

1.5

2

2.5

0 5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

10

0

(mgP

/L)

%ile

Inf TP

Inf SRP

Eff TP

Eff SRP

Severn Trent – BluePRO® trial results

-60

-40

-20

0

20

40

60

80

100

0.01

0.10

1.00

10.00

100.00

TP SRP TSS AMON BOD COD FED FET pH

Re

mo

val (

%)

(mg/

L)

Influent Effluent Removal

Anglian Water – BluePRO® trial results

0.0

1.0

2.0

3.0

4.0

5.0

6.0

SRP

(m

g/L)

SRP influent

SRP effluent

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

Tota

l P (

mg/

L)

TP influent

TP effluent

Soluble Reactive Phosphorus (SRP)

Total Phosphorus (TP)

Anglian Water – BluePRO® trial results

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

31/01/16 21/03/16 10/05/16 29/06/16 18/08/16 07/10/16 26/11/16 15/01/17

Dis

solv

ed

iro

n (

mg/

l)

Dissolved iron influent

Dissolved iron effluent

0

0.5

1

1.5

2

2.5

31/01/16 21/03/16 10/05/16 29/06/16 18/08/16 07/10/16 26/11/16 15/01/17

Tota

l iro

n (

mg/

L)

Total iron influent

Total iron effluent

Dissolved Iron

Total Iron

Anglian Water – BluePRO® trial results

0

1000

2000

3000

4000

5000

6000

7000

13/03/16 14/03/16 15/03/16 16/03/16 17/03/16 18/03/16 19/03/16 20/03/16 21/03/16 22/03/16 23/03/16 24/03/16

Tota

l P C

on

cen

trat

ion

(µ

g/l)

Date

South Witham Total P Concentrations - Composite Samples

Crude

Filter Feed

Filter Effluent

Challenges• Concerns with the ability of the system to cope with rapid flow changes

• The reject lines had to have frequent cleaning for blockages

(Severn Trent - filter 3 was particularly susceptible to the reject line

blocking; Dŵr Cymru both filters had blocking/plugging issues).

• Movement in horizontal and vertical plan of wash box has shown to

contribute to plugging events. Confined space entry currently to adjust

• The design of wash boxes and reject lines may have contributed to loss

of media seen under certain conditions.

• The feed solids and upfront feed pipework & pumping

• Issues with the upstream boll filter and bypass were encountered

initially.

Lessons Learned• Monthly spot samples might not be enough to evaluate the

performance of a new low-P technology, especially when the site permit will be based on composites.

• A new technology requires a greater process support, especially at the start of operating the process.

• BluePRO performance is best when the rate of change in flow is low.

• Control philosophy and cut in/out set points to avoid excessive flow variations.

• Flow control of more than one filter is critical to controlling headlossand shut down.

• BluePro susceptible to TSS levels <5 mg/L and 30 mg/L

• Contact tank not sure is required and settled solids

• Going from one to two filters -design, flow & dose control complicated

• Installing separate Points of Application dose points is needed

Next Steps

• Resolve the wash box weaknesses

• Improve the maintenance of internals and remove requirement of

confined space entry

• Resolve the critically important spares – delivery time not good

enough to meet the compliance limits

• Consistency & improvement of control philosophy to remove

weakness with flow control.

• Sand plugging detection to prevent loss

Thank you for your attention.

Questions?