IRBC's installed at Balladoole STW

Summary

The request sought technical specifications and operational details for Integrated Rotating Biological Contactor (IRBC) units at Balladoole Sewage Treatment Works. The authority disclosed design capacities, operational noise levels, flood risk assessments, and confirmed that the units are not airtight and rely on natural ventilation for odour control.

Key Facts

• The IRBC units are designed to meet a requirement of 1302 Population Equivalent (PE) per unit.
• The site discharge performance targets are 60 mg/l suspended solids and 40 mg/l BOD.
• The units are designed for permanent continuous operation with negligible noise levels above ambient.
• The site is approximately 20m above sea level, presenting no river, tidal, or surface water flood risk.
• The units are not airtight as they require an air supply for aerobic digestion, and odours disperse via natural ventilation.

Data Disclosed

• 1302 PE
• 60 mg/l
• 40 mg/l
• 20m
• 11,714
• 9 No
• 2018-04-09
• 2018-05-03
• 13.05.2014
• 16th March 2015

Original Request

1) Please provide me with the technical data for one Independent Rotating Biological Contactor unit installed at the Balladoole Sewage Treatment Works, including its Population Equivalent capacity, overall size, volume and noise level when operating. (Updated: this should read "Integrated" instead of "Independent"). 2) Please also provide me with the Manufacturer's and Suppliers' recommendations regarding location and site specifications, maximum continuous working hours, proximity to neighbouring receptors and potential flood risks. 3) Please would you advise me if the IRBC's are airtight, and whether insects are able to enter and leave the units. 4) Please would you also advise how any gas or odours produced during the operating processes are dealt with.

Data Tables (6)

Full Response Text

Manx Utilities PO Box 177, Douglas Isle of Man, IM99 1PS

e: foi@manxutilities.im t: 01624 687687 www.manxutilities.im

Our ref: 423336 2 May 2018

Dear ###

We write further to your request made under the Freedom of Information act 2015 which was received on 9 April 2018. Our responses follow each of your requests; 1) Please provide me with the technical data for one Independent Rotating Biological Contactor unit installed at the Balladoole Sewage Treatment Works, including its Population Equivalent capacity, overall size, volume and noise level when operating. (Updated: this should read "Integrated" instead of "Independent"). The IRBC is designed by the manufacturer to meet the requirements of 1302 PE and the site discharge performance of 60 mg/l suspended solids, 40 mg/l BOD. The manufacturer’s design is unique to each site. The dimensional details are on the attached specification – process volumes are given but overall volume is not specified; the noise level is negligible above ambient at the perimeter of the site. 2) Please also provide me with the Manufacturer's and Suppliers' recommendations regarding location and site specifications, maximum continuous working hours, proximity to neighbouring receptors and potential flood risks. Proximity to adjacent devices is designed by the manufacturer to suit the site and MU requirements for access and maintenance purposes. There is no physical location specification or restriction on this type of device. The elevations of all flow processing elements on the site are set during the hydraulic design of the site which determines the flow path levels to allow the processed flows to run through the works. This equipment is designed for permanent continuous operation. There is no river, tidal or surface water flood risk to this site as it is approximately 20m above sea level. 3) Please would you advise me if the IRBC's are airtight, and whether insects are able to enter and leave the units. The IRBC process is aerobic digestion, so requires an air supply to function. The units are not, nor is there any requirement in the UK or IOM for, them to be sealed against insect entry.

4) Please would you also advise how any gas or odours produced during the operating processes are dealt with. The units do not produce “gas”; odours disperse by natural ventilation.

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I will now close your request as of this date.

Yours sincerely

Technical Data Sheet

PACKAGE TYPE “IRBC “ INSTALLATION REF M3155 Revision III TOTAL POPULATION SERVED 11,714 SEE

           DETAILED DESIGN SUMMARY ( dated 13.05.2014 )

RoBeC (ROTATING BIOLOGICAL CONTACTOR)

Application:- BALLADOOLE WwTW , ISLE of MAN,

Prepared by:- R Robson

                                           DATE 16th March 2015

Brief description of layout : 9 No 1,302 population Robec Package Type RBC`s

Dimensional Drawing No: Sheet 4 attached.

ITEM No.

DATA

UNITS

T&B DATA 100%

COMMENTS 11.11%

A. DESIGN DATA

Design population equivalent (P.E. at 180 l/h/d) Actual population

No .

11,714 *

1,302 *

Design D.W.F.

l/h/d

150 *

150 *

Design D.W.F. (1) x (2) ( Infiltration = 2134 m3/d * )

m3/d

1,754 + 2,134 = 3,888 *

432

Maximum Permissible Peak Flow and Ratio (3) x 3 to receive treatment 1000

m3/d

7491 *

832.33

1.                                              Peak Flow Make Up *
   

   (4) Ramsey – 80.00 l/s 24 hours ( 86.70 l / sec * ) Andreas – 5.70 l/s Septic - 1.00 l/s

m3/h

312.12 *

34.68

Crude sewage B.O.D. 5 Applied load

g/h/d

60 *

60 *

Total B.O.D.5 Applied Load (6) x (1)

g/d

702,840 *

78,094

Crude Sewage B.O.D.5 Strength (6) x 1000 (2)

mg/l

400 *

400

Settled Sewage B.O.D.5 Strength (8) x (1 – x) Where x = 30%* = Reduction in Primary Settling Zone

mg/l

280 *

280

Settled Sewage B.O.D.5 Applied load to discs (6) x (1) x (1 – x)

g/d

491,988 *

54,666

Design B.O.D.5 Applied load rating to discs

g/m2/d

5.0 *

5.0

• Stated in the Enquiry.

Technical Data Sheet

                                         REF  M3155 Revision III

RoBeC (ROTATING BIOLOGICAL CONTACTOR)

Brief description of layout: 9 No 1,302 population Robec RBC Package Plants.

ITEM No.

           9 No identical 1,302 population Robec RBC

DATA Package Plants each comprising :-

UNITS

T&B DATA 11.11%

COMMENTS

12

B. PRIMARY SETTLING ZONE DATA (P.S.Z.)

Volume of P.S.Z = 150 x P + 2000 = 197.30 m3 1000

m3

208.76 Hydraulics 34.68 x 1.33 = 46.12 m3
Sludge
1,302 x 1.5 x 80

13

Retention in P.S.Z. @ 3 x D.W.F. (12) (5)

h

6.02 = 156.24
Total = 202.36
m3

14

Free Area of P.S.Z.

m2

48.42

15

Upward Flow Velocity in P.S.Z. @ 3 x D.W.F. (5) (14)

m/h

0.72

16

C. BIOZONE DATA (B.Z.)

Volume of B.Z. H = 8.10 m

m3

35.13

17

Number of Baffles in B.Z.

No.

4

18

Retention in B.Z. @ 3 x D.W.F. (16) (5)

h

1.10

19

Percentage Immersion Discs in B.Z.

%

35

20

No. of discs in each bank:-

Bank No. 1

Bank No. 2

Bank No. 3

Bank No. 4

Bank No. 5

No. No. No. No. No.

38 38 38 38 38

21

Gaps between Discs:-

mm

29

22

Speed of Rotation of Discs

r.p.m.

1.00

23

Diameter of discs

m

3.80

24

Peripheral speed of discs X x (22) x (23) 60

m/s

0.20

Technical Data Sheet

                                           REF M3155 Revision III

RoBeC (ROTATING BIOLOGICAL CONTACTOR)

Brief description of layout: 9 No 1,302 population Robec RBC Package Plants.

ITEM No.

DATA

UNITS

T&B DATA 11.11%

COMMENTS

25

Effective Biological area per disc (E.B.A.) Sandex Media

m2

58.37

26

Total E.B.A. required (10) @ 5.00 B.O.D.5 g/m2/d (11)

m2

10,934

11,090 provided

27

No. of Discs required (26) @ 5.00 B.O.D.5 g/m2/d (25)

No.

190

28

D. FINAL SETTLING ZONE (F.S.Z.)

Volume of F.S.Z. = 135p0.85 = 60.00 m3 1000

m3

90.82

29

Free Area of F.S.Z. = 3p0.85 = 33.30 m 2 40

m2

36.28

4 No Sludge Hoppers 2.375 m long x 0.85 m wide

30

Retention in F.S.Z. @ 3 x D.W.F. (28)

(5)

h

2.62

31

Upward Flow Velocity in F.S.Z. 3 x D.W.F. (5) (29)

m/h

0.96

32

E. MECHANICAL DATA

Length of Rotor Shaft between Outer Bearings

m

8.30

33

F. ELECTRICAL DATA

Rotor rating – Rotor Drive 3 Phase

kw

3.00

34

Power consumed input to motor

Kw Demand at Motor Shaft x 24 Motor Efficiency as a Decimal

kwh/d

97.00

35

Consent Standard (1) Suspended Solids (2) B.O.D.5 (3) Ammoniacal Nitrogen

mg/l mg/l mg/l

60 40 --

F.E.S * STATED

PLANT LAYOUT

LEGEND SALIENT DIMENSIONS (m) A Tank Length 17.16 + 1.172 + 7.72 26.052 B Tank Width 4.70 C Tank Depth 3.70 D Cover Depth 2.30 E Total Depth 6.00

F1 Tank Flange to Inlet Pipe Invert 0.30 F2 Tank Flange to Outlet Pipe Invert 0.52 G Primary Settling Zone Length 17.16 H Biozone Length 8.00 I Biozone Width 4.10 J Disc Diameter 3.80 K Biozone Radius 2.05 L Final Settling Zone Length 7.72 M Height of Webs 0.14 N
Depth of Water From T.W.L. P.S.Z. 3.36 P
Depth of Water From P.W.L. F.S.Z. 3.18 U Shimming Allowance 0.015 d Trapped Pipe Diameter 0.20

Approximate Weights

Condition Kg Dry 50,000 Operational 455,000