Using Techno-Economic Assessments to Determine the Degree of Centralization in Municipal Wastewater Infrastructure in the Context of Urban Environments
Rapid urbanization, aging infrastructure, high energy demand, and water scarcity challenge
the strong reliance and sustainability of centralized municipal wastewater infrastructure. On the
other hand, decentralized wastewater treatment systems (DWWTS) have gained popularity as a
potential cost-effective alternative compared to costly (capital, operational, and maintenance)
centralized wastewater treatment systems (CWWTS). However, determining the extent to which
a municipal wastewater infrastructure should be centralized remains a daunting task. Previous
studies have attempted to numerically characterize the degree of centralization within areas that
have existing infrastructure. Unfortunately, no study has been conducted to determine the degree
of centralization for areas without extensive existing infrastructure.
This research aims to assess the viability of various decentralized treatment systems, in the
context of urban cities with high population densities and potential of water scarcity, by comparing
their economic and environmental performances to centralized wastewater infrastructure. Using
two wastewater modeling and simulation softwares (GPS-X and CapdetWorks), the technical and
economic performance of DWWTs are compared to that of CWWTs. Both suspended and attached
growth treatment processes were analyzed. Examples of suspended growth treatment processes
include conventional activated sludge (CAS), sequencing batch reactors (SBR) and membrane
bioreactor (MBR). Examples of attached growth treatment processes analyzed included trickling
filter (TF), rotating biological contactor (RBC) and integrated fixed-film activated sludge (IFAS).
This research’s main conclusion is that when keeping the technical performance constant, it is cost-prohibitive to decentralize municipal wastewater infrastructure. This is primarily because when
the influent flow is halved, the total treatment cost is not halved. It takes almost the same treatment
unit ops to treat half of the flow as it would take to treat the full flow
