Treatment Process Design Calculations by Group One

Group One Project Management Expertise, Technology, Results

Treatment Process Works Design Calculations

Client

Revision

Date

Compiled

Checked

Approved

16/04/2013

Board of Management AIT C/o Group One Consulting Engineers Ltd, Athlone, Co. Westmeath

B.Eng(Hons) Civil Engineering

Group One Project Management

Contents Contents ................................................................................................................................ i 1

Primary settlement tank design.................................................................................... 1 1.1

Introduction ........................................................................................................... 1

1.2

Hydraulic Sizing ...................................................................................................... 2

1.3

Geotechnical Design: Uplift (EC7).......................................................................... 3

1.4

Structural Design (EC 2) ......................................................................................... 4

PFBR unit outline design ............................................................................................... 7 Media chamber sizing ...................................................................................................... 7

Group One Project Management

1 Primary settlement tank design 1.1 Introduction The primary settling tank for this facility will consist of 2 sections: 1. Settling chamber 2. Buffer tank The use of published Environmental Protection Agency (EPA) guideline documents in the assistance of the design simplifies the design process considerably. The design document for this design will be the ‘Treatment Systems for Small Communities, Business, Leisure Centres and Hotels Wastewater Treatment Manual’ for hydraulic sizing. The design includes geotechnical design for the ULS of uplift according to: 

BS EN 1997 – 1

Reinforced concrete design according to: 

BS EN 1992 – 1

This report is to be read with reference to the following drawing: 

13_AD_007 Primary Settlement Tank Design

Group One Project Management Job Title: Primary Settlement Tank Structure Ref: 1.2

Hydraulic Sizing

Reference EPA Design Manual Table 3

Job No. AITWWTF Made By: Luke Molloy Checked by: FK Approved by: JC

Sheet 1 0f 5 Date: 13/04/2013 Date: 15/04/2013 Date: 15/04/2013

Calculations Wastewater characterisation :

Output

For schools that are non-residential and have cooking onsite the following loadings are recommended: Hydraulic loading = 60 litres/day/person Biological loading (BOD5) = 30g/day/person Proposed design parameters: Population equivalent (PE) = 500

$4.1.1

Conventional primary settlement tank design: Horizontal tank base area

Eqn. 2

Eqn. 3

The minimum surface area of the settlement tank is equated as follows: A = x P 0.85 = 19.68m2 This value is based on dry weather flow (DWF) of 180l/person so to allow for the reduced value of 60l/person/day the figure is modified by a conservative 0.5 Modified A = 19.86 x 0.5 = 9.84m2

Tank area = 9.84m2

Horizontal tank capacity The capacity of the primary settlement tank can be equated as follows: C = 180 x P0.85 = 35432 litres Modified capacity for 60l/person/day = 17716 litres

Tank Vol =18m3

Tank dimensions Taking a ratio of length = 3 x width Width = 1.8m Length = 5.4m Height = 2.5m Allowing 400mm min clearance from top water level to top of tank

Group One Project Management Job Title: Primary Settlement Tank Structure Ref: 1.3

Geotechnical Design: Uplift (EC7)

Reference EN 1997 -1 $2.4.7.4

Eqn. 2.8

Job No. AITWWTF Made By: Luke Molloy Checked by: FK Approved by: JC

Sheet 2 0f 5 Date: 13/04/2013 Date: 15/04/2013 Date: 15/04/2013

Calculations Verification for uplift (UPL) shall be carried out by checking that the design value of the combination of destabilising permanent and variable vertical actions (Vdst) is less than or equal to the sum of the design value of the stabilising permanent vertical actions (Gstb) Vdst,d Gstb,d

Output

Vdst,d = Gstb,d =

These values are design values hence partial safety factors are required for ULS

National Annex, A Table A.1

Required partial safety factors Îłg,dst = 1.1 Îłg,sta = 0.9 Taking the unit as a whole and water level at a height of 1.5m from the base of the tank: Vdst,d = 1.1 x 10 x 1.5 x 5.2 x 6.2 = 531.96 kN Gstb,d = 0.9 x 25 x 38 = 855 kN Uplift OK Vdst,d

Gstb,d therefore tank satisfies the uplift condition

Group One Project Management Job Title: Primary Settlement Tank Structure Ref: 1.4

Structural Design (EC 2)

Reference

Job No. AITWWTF Made By: Luke Molloy Checked by: FK Approved by: JC

Sheet 3 0f 5 Date: 13/04/2013 Date: 15/04/2013 Date: 15/04/2013

Calculations This design is based on the longest wall of the tank and based on the external drained active soil pressure against it while the tank is empty. Wall dimensions = 6.2m x 2.5m

Output

g = gravity = 9.81m/s2

EN 1992-1 Table NA.7

EN 1992 – 1

Assumed values for soil: Ka = 0.27, active earth pressure coefficient (Ranking) ρs = 19kN/m3, soil weight ρw = 10kN/m3, weight of water fyk = 500N/mm2, characteristic tensile strength of steel fck = 30N/mm2, characteristic compression strength of concrete (class designation XD2) Surcharge load = 10kN/m2 Partial safety factors: γf = 1.35 at ULS for permanent loads Horizontal of soil on wall: Hsoil = γf x ρs x Ka x g x h2 x 0.5 = 212kN Hsurcharge = γf x Ka x h x surcharge = 9.11kN Hsoil acts h/3 lever arm Hsurcharge acts h/2 lever arm MED = design applied bending moment: MED, Soil = 212 x 0.84 = 178.1kNm MED, Surcharge = 9.11 x 1.25 = 11.4kNm MED, Total = 178.1 + 11.4 = 190kNm

MED, = 190kNm

This moment is used as the moment needed to provide resistance to by the reinforcement steel in the tank wall

Group One Project Management Job Title: Job No. AITWWTF Primary Settlement Tank Made By: Luke Molloy Structure Ref: Checked by: FK Structural Design (EC 2) Contd. Approved by: JC Reference Calculations EN 1992 – 1 Longitudinal reinforcement:

Sheet 4 0f 5 Date: 13/04/2013 Date: 15/04/2013 Date: 15/04/2013 Output

Walls Breath of member = 2500mm Height of member = 400mm EN 1992-1 Table NA.7

Cover required = 50mm (class designation XD2) Assumed bar size = 20mm diameter Effective depth to reinforcement = 340mm K=

= 0.022

z/d = 0.5(1+√

) = 0.98

limit z/d to 0.95 z = 0.95 x d = 323mm

Required area of steel reinforcement is given by:

As 

M Ed 0.87f ykz

As = 1285mm2 Provide 15 No. H12 @180mm spacing to be provided on both faces and also as longitudinal reinforcement. See drawing No 13_AD_ Base Assuming worst case of water pressure uplift on the base = FED = 1.5 x 10 x 5.2 x 6.2 x 1.35 = 653kN This acting along the short span gives: 653/6.2 = 105kN/mrun, use for MED as w l = 6.2m MED, = wl2/8 = 504kNm

MED = 504kNm

Sheet 5 0f 5 Date: 13/04/2013 Date: 15/04/2013 Date: 15/04/2013 Output

As = 2771mm2 Provide 9 No. H20 bars @ 125mm spacing This can be provided as transverse steel also. Central dividing wall In a similar process to the external walls except using the wall height as depth of water considering worst case if only one compartment of the tank is completely full and the other is completely empty. Fw = force from water FW = γf x ρw x g x h2 x 0.5 = 414kN Acting h/3 from base MED = 348kNm

MED = 348kNm

As = 2477mm2 Provide 15 No. H16 @ 180mm spacing Provide H16 @ 200mm spacing transverse

Group One Project Management

2 PFBR unit outline design Job Title: Pumped Flow Biofilm Reactor Tanks Structure Ref: Media chamber sizing

Reference

Job No. AITWWTF Made By: Jason Corbett Checked by: FK Approved by: LM

Sheet 3 0f 5 Date: 13/04/2013 Date: 15/04/2013 Date: 15/04/2013

Calculations

Output

Flow to unit: 60 litres per person per day for 500 PE = 30,000l/day Unit operates for 3 cycles at 10,000l per cycle Hewitech CF 25 Product Data Sheet

Unit volume = 10,000l Media occupy 96% of tank volume: 10,000 x 1.04 = 10.4m3 with an increase to 11m3 due to microbial growth on media Estimated tank dimensions given clearance of 0.8 metres Tank dimensions: Height = 2m Breadth = 2.3m Length = 4m Allowing for a base thickness of 0.5m and a wall thickness of 0.4m and a cover plinth of 0.2m the overall tank dimensions are: Height = 2.7m Breadth = 3.1m Length = 4.8m

These are the dimensions for each tank. There are two tanks involved in this process.

Tank dim: H = 2.7m B = 3.1m L = 4.8m