Systems are cost-efficient and can be scaled up or down as needs change

Decentralized wastewater treatment, traditionally associated with remote areas, is gaining traction as a viable and advantageous solution for urban environments. While centralized systems have long been the norm in cities, aging infrastructure, increasing costs, and the desire for more localized control are prompting a reevaluation of this paradigm.

The key difference between decentralized treatment plants and their centralized counterparts is the way the wastewater is collected and conveyed to the treatment facility. Centralized treatment involves collecting wastewater from a large area through a network of sewers and transporting it to a single, large, centrally located plant.

With decentralized systems, wastewater is treated at or near the point of generation rather than being transported to a centralized treatment facility. This approach offers several benefits over traditional methods, including reduced infrastructure costs, increased scalability, energy efficiency, faster deployment, and improved resilience.

Benefits of Decentralized Treatment in Urban Areas

Decentralized wastewater treatment offers real benefits over centralized treatment:

• Reduced infrastructure requirements: Decentralized systems reduce the need for costly sewer networks, which are particularly expensive and disruptive to install in densely populated areas. Initial infrastructure costs are typically much lower compared to the capital investment required for large, centralized treatment plants and extensive pipelines.
• Scalability and flexibility: Decentralized plants often consist of modular systems that can be installed in phases, allowing for expansion with population growth. Decentralized systems can be designed to meet the specific needs of a community, offering more flexibility for urban settings.
• Cost-effectiveness. Decentralized systems tend to be more energy-efficient than centralized ones, especially when using gravity-fed systems and renewable energy sources. Additionally, less energy is required since wastewater is not transported over long distances, cutting energy costs further.
• Faster deployment and implementation. Decentralized wastewater treatment plants are often designed as modular units that can be prefabricated off-site and assembled on-site, reducing on-site construction time. The use of standardized, factory-built components allows for quick assembly and integration, reducing delays.
• Improved resilience and reliability. Multiple decentralized units spread across several communities in a region can provide redundancy and enhance disaster preparedness, making the overall system more resilient. Decentralized units can continue to function independently during emergencies, providing continuous treatment services even if parts of the network are compromised.

These advantages make decentralized systems an ideal solution for many urban areas.

Fluence’s Aspiral™ Flex for Urban Wastewater

To fully realize these benefits, Fluence offers Aspiral™ Flex, which packages membrane aerated biofilm reactor (MABR) technology inside a standard shipping container, allowing it to be shipped anywhere in the world. As decentralized systems, they are designed to minimize noise and odors, resulting in minimal disturbance to the communities they serve. Their modular design provides the flexibility to scale up or down by simply adding or removing units as a community’s needs change.

MABR systems combine nitrification and denitrification in a single tank using a spirally wound membrane. This innovative approach, coupled with passive aeration, reduces energy consumption by up to 90% compared to traditional methods.

With treatment capacities ranging from 5,000-90,000 GPD (20-340 m³/d), Aspiral™ plants are suited for small towns, residential communities, and other urban settings, and their energy efficiency makes them a great choice for off-grid settings, such as remote villages and resorts.

Each Aspiral™ shipping container features up to five MABR units, each consisting of a spirally wound membrane submerged within a wastewater treatment tank. In a Fluence MABR system, low-pressure aeration is used, resulting in significantly lower energy usage than in systems that use conventional high-pressure aeration. The configuration of MABR membranes allows nitrification and denitrification processes to occur simultaneously within the same tank, whereas conventional treatment requires separate chambers for these processes and thus a larger footprint.

Fluence’s MABR technology uses gas-permeable membranes to deliver oxygen directly to the nitrifying biofilm growing on the membrane surface, while denitrification is performed by anaerobic denitrifying bacteria in the anoxic bulk liquid. This approach enhances the efficiency of biological wastewater treatment by optimizing oxygen transfer and promoting effective microbial activity that results in simultaneous nitrification and denitrification (SND) within the tank. Unlike conventional aeration, where bubbles rise through the water and result in significant oxygen loss, MABR provides a more efficient and direct oxygen supply to the biofilm.

Aspiral™ Decentralized Treatment in Action

Xilingang Town, located in Hunan Province, China, was discharging untreated wastewater directly into the Zhixi River, harming the surrounding environment. The town needed an environmentally friendly, energy-efficient, and cost-effective wastewater treatment facility with the capacity to treat 211,300 GPD (800 m³/d). The plant needed to meet Class 1A effluent standards and meet goals outlined in China’s recent five-year development plan.

They chose an Aspiral™ wastewater treatment system employing MABR technology. The system features pretreatment with a screen filter and selection tank; four MABR Aspiral™ L4 containerized systems; a secondary clarifier; a tertiary media filter and disinfection unit; and smart management software for remote monitoring and control. The facility provides high-quality effluent that can be discharged into the environment without fear of contamination while keeping energy consumption and operational costs at a minimum.

Real-World Application and Benefits

Decentralized wastewater treatment solutions provide a range of benefits for urban areas, including energy efficiency, cost savings, environmental sustainability, resilience, and scalability. These systems offer practical and effective wastewater management solutions that can be quickly deployed and adapted to the specific needs of urban communities, making them a valuable complement or alternative to traditional centralized systems.

Contact Fluence’s team of experienced engineers for more information on how Aspiral™ Flex can transform your community, or to tailor a customized solution best suited for your unique wastewater challenges.