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Conventional systems for urban sanitation and wastewater management in middle- and high-income countries
Published in Thomas Bolognesi, Francisco Silva Pinto, Megan Farrelly, Routledge Handbook of Urban Water Governance, 2023
Other alternatives to gravity sewers use pressurized pipes. Low-pressure sewers can also be installed when the terrain is variable, difficult to excavate, or if the location is below the mainline sewer elevation. These systems have a grinder pump installed at each household connection that “pushes” the wastewater to the mainline sewer. Low-pressure sewers can thus be installed without deep excavation. Similarly, vacuum sewer systems use air pressure to create a partial vacuum that “pulls” wastewater from the point of generation to a central vacuum station. An advantage of vacuum and pressurized sewers is that they operate well with minimal water in the system, thus being the most appropriate options for ultra-low flush and water-saving toilets. They also offer environmental advantages since infiltration from groundwater into these systems is minimized, and, in the case of vacuum sewers, leakages from exfiltration are also avoided. Construction costs for pressurized systems are generally lower than gravity systems. However, maintenance costs can be higher. They often have a higher number of pumps than gravity systems and rely on electricity for pump operation. Pressurized sewers can thus be sensitive to power outages. Similar to simplified sewer, pressurized system use smaller diameter pipes that can be prone to blockages, thus requiring more maintenance. However, with improved fault-finder sensors and automation in the network, operational challenges with alternative sewers can be minimized. Life cycle replacement costs are expected to be higher for pressurized systems since the components have lower life expectancies than conventional gravity systems.
Impact of new sanitation technologies upon conventional wastewater infrastructures
Published in Urban Water Journal, 2018
Carlo Gottardo Morandi, Stephan Wasielewski, Karen Mouarkech, Ralf Minke, Heidrun Steinmetz
Due to the requirement of an incremental set-up of a vacuum sewer, future research should also contemplate energy balances within both the sewer system and the WWTP rather than the latter only. Additionally, transition concepts including further scenarios and technologies other than blackwater co-digestion should be assessed in future works.