Costing Metrics

CACTUS collects empirical data from real urban sanitation projects and has created a process for normalising this to enable the generation of meaningful comparable cost estimates for a range of sanitation service delivery options in a range of locations.

General Principles

CACTUS collects costs from existing and completed operational sanitation systems, rather than from a bottom up design basis. The approach is based on a number of key concepts which can be summarised as follows:

  • CACTUS costs are based on semi-analytic estimation, and are therefore ball park estimates, commensurate with strategic or conceptual planning rather than detailed design or construction estimates.
  • CACTUS costs estimates are predicated on the assumption that a single virtual service provider provides services across the entire value chain (collection, emptying, transport, treatment). While this is rarely true in practice, it means that transfers between the steps of the value chain are not included in the costs estimates, and the focus is on real costs of ‘Make’ and ‘Buy’ elements of the system (see Figure 1).
  • CACTUS recognises that most service providers lack complete information on total costs incurred and/or are unable to report on all costs (for example taxes may not be paid, or the cost of land purchase may be offset). Ultimately we intend to fill all missing data gaps using averaged data from the CACTUS database but currently such gaps are usually filled in consultation with delivery partners and/or through inspection of the existing database.
Standard metrics

CACTUS uses two standard cost metrics to describe costs associated with different sanitation service delivery options.

  • Total Annualised Cost Per Household (TACH)
  • Total Annualised Cost per Capita (TACC)

Total Annualised costs include capital costs annualised over the lifetime of the relevant infrastructure or equipment, including costs of capital and discounting, plus the annual operational costs associated with that element of the sanitation service delivery option.

All costs are normalised in the database to a single currency and date to allow for easy comparisons.

Definition of Sanitation System

There are multiple technical approaches to the delivery of urban sanitation. This means that creating comparable data across multiple geographic locations can be tricky. Furthermore, many sanitation service delivery systems are incomplete or partial – so that information on costs does not represent the cost of delivering safely managed sanitation across the entire value chain (for example, many utilities have information on the costs of operating wastewater treatment plants but have absent or incomplete sewer networks).

To address these twin challenges, CACTUS uses twenty seven standard ‘Component Descriptors’ to describe broad categories of technologies generally used to deliver sanitation. These are clustered across five ‘Elements’ of the Sanitation Value Chain. Component Descriptors are designed to identify technological options which serve homogeneous functions and broad categories where costs are likely to be comparable. They are therefore broader than typical technology descriptors used for detailed discussion of individual sanitation systems in the WASH sector.

Sanitation Elements

Provisions of sanitation services starts from the toilet to end at disposal/discharge point. A safely managed sanitation system needs to go through a functional system from collection/capture at the toilet (containment), emptying and transport, treatment and finally disposal , often referred as Sanitation Value Chain (SVC).

Sanitation Value Chain
Emptying Transport
Emptying and Transport
Sanitation Systems

The system is mainly characterised by the stream of faecal waste either waste water which is catered by sewer system or the ranges of faecal sludge (FS) - thicker in concentration than waste water e.g. septage or contents of faeces cartridges etc. from on-site sanitation system. CACTUS organises the different technical options composing one sanitation value chain, classifying into systems, elements.

Component Descriptors for sanitation systems

Component: A cluster of technologies which have generally similar characteristics, which can deliver the functionality of a single Element of the SVC and which are likely to have similar cost profiles.

Hilighted cells show possible Components that can be part of a complete sanitation system

Emptying Emptying and Transport Transport
Pipes - conventional, separate, with pumping
Pipes - conventional, separate, no pumping
Pipes - conventional, combined, with pumping
Pipes - conventional, combined, no pumping
Pipes - simplified, separate, with pumping
Pipes - simplified, separate, no pumping
Pipes - simplified, combined, with pumping
Pipes - simplified, combined, no pumping
Passive aerobic waste water1
Machine-powered aerobic waste water
Anaerobic waste water
Sealed tank with infiltration structure
Sealed tank without infiltration structure
Infiltrating pit
Manual (no specialised equipment) Wheels - human-powered (transport only)
Human-powered with specialised equipment Wheels - machine-powered (transport only)
Machine powered Wheels - human- and/or machine-powered with transfer station (transport only)
Wheels - human-powered
Wheels - machine-powered
Wheels - human- and/or machine-powered with transfer station
Aerobic FSM
Anaerobic FSM

1 Waste water treatment unit can sometimes incorporated to co-treat faecal sludge transported from on-site sanitation systems. In this case the facility would still be classified as waste water treatment rather than faecal sludge treatment.

2 Conventional sewers use ‘traditional’ hydraulic design approach, usually free flowing and laid under the road network.

3 Simplified sewers use a modified hydraulic design approach. They are smaller diameter and laid at shallower depths than conventional sewers. Network may be laid to follow shortest route subsequently optimising length of pipes.

Cost Elements

Cost elements in CACTUS are divided into categories that align broadly with standard approaches to estimating costs in infrastructure projects.

  • CAPEX Capital expenditures
  • 1. Land
  • 2. Infrastructure and Buildings
  • 3. Equipment
  • 4. Staff Development
  • 5. Major and Extraordinary Repairs
  • 6. Other CAPEX
  • 7. Administrative Charges
  • 8. Financing
  • 9. Taxes
  • OPEX Operational expenditures
  • 1. Land
  • 2. Infrastructure and Buildings
  • 3. Equipment
  • 4. Staffing
  • 5. Consumables
  • 5.1. Utilities
  • 5.2. Fuel
  • 5.3. Chemicals
  • 5.4. Services
  • 5.4.1. Consulting/advisory
  • 5.4.2. Legal
  • 5.4.3. Insurance
  • 5.4.4. Regular Maintenance
  • 5.4.5. Other services
  • 5.5. Other consumables
  • 6. Other CAPEX
  • 7. Administrative Charges
  • 8. Financing
  • 9. Taxes
Underlying Assumptions

CACTUS is designed to enable the generation of cost estimates for the entire sanitation value chain, as if a single utility were providing services. It also includes both "Make" or internal costs and "Buy" or external costs. It does not include transfers, subsidies or fee payments which transfer funds from one step on the value chain to the next.

Sanitation Value Chain

WASH Research Group, School of Civil Engineering, University of Leeds |
© 2022 CACTU$ Costing