Studio on Wastewater Management - Infrastructure Planning

WATER AND SANITATION Studio

FACULTY OF PLANNING

PRASENJIT SHUKLA PP0007216 III Semester | MURP July – Nov 2017

CENTRALISED SEWERAGE NETWORK

Wastewater Management Under Guidance of

MEERA MEHTA

MONA IYER PLANNING MAITREE PATEL FACULTY OF

CONTENTS

01 Introduction

04 Need for Retrofitting Intervention

02 Spatial Growth & Expansion of Sewer

05 Flow Assessment and Detailed Intervention

As a part of Infrastructure Planning Studio, on water and sanitation of Ahmedabad, this study aims to assess key challenges with Centralised Sewer Network in the city, and provides detailed interventions to improve the same.

Network Scenarios

Government’s Proposals on expansion of sewer networks under various schemes were identified. Two possible scenarios were then assessed upon complete and limited expansion respectively.

03 Existing Sewer Network Assessment

Frequent complaints related to breakdown or blockage of sewer lines were mapped to identify major concern areas and 3 possible causes for the same.

Literature review

The flow assessment was done for 6.2 km long trunk network connecting five sewage pumping stations in Central Zone. The findings from this further led to intervention on retrofitting sewer lines for efficiency improvement.

06 Costing and Phasing | Conclusion

Phasing and costing of the entire process has been done while looking at the Capital Expenditure followed by conclusion.

Site visits

Secondary Data Collection

Prasenjit Shukla | PP0007216

Identifying need for intervention (retrofitting existing Sewer lines in Central Zone) by assessing Carrying Capacity (CC) and flow velocity of Sewer Lines through Flow Assessment.

Proposed Technology

Calculation & Projection

Centralised Sewerage Network| Wastewater Management

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INTRODUCTION | Waste Water Management INTRODUCTION The infrastructure studio focuses on Water and Sanitation of Ahmedabad city.

The students were divided into five groups with respect to 5 sectors such as Water Sensitive Planning, Wastewater Management, Financing Program and Governance, Water as Heritage, Swacch Ahmedabad.

VISION | Water sensitive and sanitized Ahmedabad Centralized Sewerage Network in Ahmedabad City REUSE

NON-SEWERED

SEWERED

Service Chain

Conveyance

Collection

Treatment

Disposal/Reuse

SCOPE Sewerage Network

2500 km

Area Covered by Sewer Network

90%

Household Coverage

85%

Efficiency of Collection of Sewage

97%

Sewage Generation

Sewage Treatment Capacity

2017

880 MLD

813 MLD

2031

1180.44 MLD

1388.6 MLD

(estimated)

Source: Sewerage SLIP, AMRUT, 2017

VISION | Wastewater as a Resource Prasenjit Shukla | PP0007216

SEWERAGE NETWORK | AHMEDABAD Ahmedabad, a large metropolitan city is highly dependent on its centralized sewerage system for managing wastewater generated from 85% households*.

• The basic service chain of the centralized sewer network involves transferring of 840 MLD* of black and grey water from households to the intermediate SPS, and then further to the STPs. • On assessing the performance based on current (2017) and future (2031) demand-supply gap, it was observed that, augmented treatment capacity of existing STPs, is sufficient to treat the wastewater in 2031.

• Is the network carrying capacity sufficient or there is a need for expansion? * Source: Sewerage SLIP, AMRUT, 2017

Centralised Sewerage Network| Wastewater Management

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CITY SPATIAL EXPANSION SCENARIOS Proposed Networks 1. 8.3 km Trunk line from Odhav to Vinzol. (AMRUT)

EXPANSION SCENARIOS 6

2. Network in TP 98 and part of Nobalnagar. (SJMMSVY)

3. 2 km Sewerage pipeline (bypass) from Panjarapol to Ramol toll plaza. (SJMMSVY)

4 2

4. 1.5 km Sewerage network in Vejalpur Area. (SJMMSVY)

1 3

5. 21 km Sewerage Network Lambha. (SJMMSVY) 6. 15 km of Sewerage Network at Sola. (SJMMSVY)

Completion of all the proposed networks will improve the coverage of network and collection efficiency to almost 95%.

5

Image Source: Google Earth

Scenario 1

Expansion of Sewer Network as per Government’s Proposals

Scenario 2

In order to understand need for expansion of network, 2 scenarios were assessed. First, when there is complete expansion in all directions as per government proposals, and second, when there is limited expansion. First scenario will certainly increase both Capex and Opex. Whereas, restricting expansion in southern low lying areas, where potential to develop OSS is high will ensure about 12% capex savings and will reduce the pressure on pumping stations.

Under the Development Plan of 2021, densification of some core areas of the city are planned through Central Business Districts and Transit Oriented Zones. This will put additional pressure on the existing trunk network systems. Therefore, efficiency of existing Sewer network needs to be assessed.

Source: Sewerage SLIP, AMRUT, Swachhta Report-2017

Limited Expansion (Combined Off-Site and OSS Systems for the City)

Total Cost for Network 83.3 Crores Total Length 47.8 km STP Location Direction of Sewer Network Expansion

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SCENARIO

OSS: On-Site Sanitation

Cost and Time Efficient • Environmental benefits.

•

Decentralization of the Sewage collection and treatment will reduce the pressure on the trunk network

Centralised Sewerage Network| Wastewater Management

12% CAPEX Reduction 21 km Reduced STP Location

Direction of Sewer Network Expansion Development of On-Site Sanitation Facility FACULTY OF PLANNING

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EXISTING SEWER NETWORK Existing Sewer Network | Central Zone Frequent Complaints of breakdown and blockage (September 2017)

CENTRAL ZONE •

39% Complaints of breakdown and blockage were reported from North and Central zone

• Old city: drainage lines were laid in 1921.

NZ

39%

CZ

•

Manhole Repair

•

Sewer Breakdown

•

Manhole cleaning

•

New Manhole Water borne diseases - Cases

2000

No. of Cases per year

1500 1000

• Highest Density : 415 PPH

500

0

• Increasing cases of water borne diseases (Jaundice, Typhoid).

2000

2002

2008

Jaundice Case: Central Zone

2011

2011

2001

• No interventions proposed by government

0

Image Source: Google Earth Data Source: AMC Sewa App

200

400

600

800

Source: Impact of improper sewerage system and its management in urban areas.

Anusha Pallapu

IDENTIFYING ISSUES

CAUSES

In order to identify issues with existing sewer network, frequent complaints related to breakdown or blockage of sewer lines were mapped, to identify major concern areas. It was noted that, about 39% complaints were received from highly dense North and Central zones, where sewer network was laid 80 years back.

The 3 possible reasons for frequent occurrence of these complaints are: • Inefficiency of sewer network (need for retrofitting), • Inefficiency of SPS (need for operation and/or contract improvement) or • Lack of management initiatives of these sewer lines.

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Centralised Sewerage Network| Wastewater Management

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INTERVENTION | Need for Retrofitting INTERVENTION : Identifying need for retrofitting existing Sewer lines in CENTRAL ZONE Identify carrying capacity (CC) and flow velocity of sewer lines (Flow assessment) Scenario 1

Scenario 2 Sewage Carried (present and future) < CC

Sufficient for present and future demand

Sewage Generated (2017)

CC

Sewage Carried (present or future) > CC

Need for Retrofitting of Sewer lines

89 MLD

74.48 MLD

CC

Sewage Generated (2031)

Diameter (mm)

Existing flow rate (m3/hr)

Desired flow rate (m3/hr)*

Existing velocity (m/s)

Scouring velocity (m/s)

Efficiency

SHAHIBAUG

750

266

1145-1908

0.29

0.9

32

OLD GIRDHARNAGAR

450

128

412-687

0.28

0.9

31

NEW GIRDHARNAGAR

500

290

509-848

0.51

0.9

57

DARIYAPUR

1400

719

3988-6477

0.16

0.9

18

JAMALPUR

1800

1576

6592-10987

0.22

0.9

24

Location of Sewage Pumping Station in Central Zone

INTERVENTION This was done by measuring designed carrying capacity of trunk lines in central zone by assessing difference (gap) between actual sewage that is carried in them and Carrying Capacity. If actual sewage carried is close or more than carrying capacity, then there is a strong need for retrofitting. If it is less, then there is need to calculate the existing velocity to know the efficiency.

Total Length of trunk line: 6.2 km

(%)

* For desired flow rate, velocity ranges between 0.9-1.5 m/s

Existing flow rate of WW is much lower than the desired flow rate.

Existing flow velocity lower than scouring velocity causing silting.

Sufficient Design CC of sewer

(Chances of abrasion, pipe

lines

burst)

Zone Boundary Trunk Lines Water Bodies Roads

Sewage Pumping Station Image Source: Google Earth

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Centralised Sewerage Network| Wastewater Management

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FLOW ASSESSMENT Assumption : 40 % SILT

Design Carrying capacity* V S Available capacity** 7000

* Considering minimum Scouring Velocity as 0.9 m/s ** Assuming 40% silt deposition

6000 CC

Available Capacity

Existing Flow Rate

Available Capacity

(Utilised Capacity)

(After 40% Silt Capacity)

40 % Silt

Shahibaug

5000

4000 Existing flow rate

Available Capacity is very less because of the silting, which will be insufficient for our design year.

Old Girdharnagar

>

3000 Available Capacity

2000 1000

New Girdharnagar

0

Dariyapur

Jamalpur

Equipment with AMC *

Trenchless Technology Installation

Design CC

Time Saving

Replacement

No disturbance to surrounding

Rehabilitation

Cost efficient

Rickshaw mounted Grad Machine

10

Jetting Machine

Super sucker

High flow Jetting

Gully Emptier

35

12

8

8

* Source: Sewerage SLIP, AMRUT, 2017

FLOW ASSESSMENT

TRENCHLESS TECHNOLOGY

The results from flow assessment indicated the old sewer lines of Central zone are heavily silted. This was also confirmed by the AMC officials, who told that lines are silted due to age. If this siltation continues, the chances of pipe burst and abrasion will increase and have major cost implications on AMC. Hence, there is an urgent need for retrofitting these old sewer lines.

In order to improve the efficiency of these old sewer lines, the technology identified for retrofitting was Trenchless technology. This technology has time-cost saving advantages without causing disturbance to the surrounding built environment.

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Centralised Sewerage Network| Wastewater Management

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PHASING AND COSTING PHASING AND COSTING

PHASING AND COSTING

Funding & Implementation

AMC, Central / State Grant

Operation & Maintenance

AMC

Time Period

TOTAL LENGTH TO BE RETROFITTED

KM

4 Year

TOTAL COST

Capital Expenditure : ₹ 332 Crores (2017-18) Phase 1

2018-19

26.5 Cr

1.7 km

Phase 2

2019-20

23.4 Cr

1.5 km

Phase 3

2020-21

23.4 Cr

1.5 km

Phase 4

2021-22

23.4 Cr

1.5 km

AMC is already equipped with the machinery required for trenchless retrofitting process.

Therefore, the cost estimation was done considering Rs. 15.6 Cr. cost per km of sewer line (AMC, 2017). This process has been phased out into 4 parts. Total Capital expenditure for retrofitting 6.2 km trunk line is estimated to be Rs. 96.7 Crores.

CRORES Shahibaug SPS

Implementation of this project will ensure sufficient carrying capacity for the future population.

New Girdharnagar SPS Girdharnagar SPS

Dariyapur SPS

CONCLUSION The same Intervention can be extended for other zones as well. Improved efficiency of existing sewerage system will ensure a reduction in operational expenditure, along with energy savings. An efficient sewerage system can contribute positively in achieving sanitation in urban areas. On implementing thematic interventions of Off-Site Sanitation in non-sewered areas, the vision of overall wastewater management study can be achieved i.e. using “Wastewater as a Resource” for Ahmedabad city and its peripheries.

Jamalpur SPS

Phasing Source: * AMRUT SLIP, under NRCP Scheme

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FACULTY OF PLANNING

PRASENJIT SHUKLA PP0007216 prasenjit.Shukla.mplan16@cept.ac.in

FACULTY OF PLANNING