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
FACULTY OF PLANNING
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.
Prasenjit Shukla | PP0007216
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.
Prasenjit Shukla | PP0007216
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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Centralised Sewerage Network| Wastewater Management
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FACULTY OF PLANNING
PRASENJIT SHUKLA PP0007216 prasenjit.Shukla.mplan16@cept.ac.in
FACULTY OF PLANNING