Entex Technologies Inc.

Contact Stabilization Activated Sludge Process (CSASP)



The contact stabilization activated sludge process (CSASP) typically achieves the same treatment efficiency in a smaller volume than conventional activated sludge plants. CSASP is particularly suited for small to mid-scale plants where influent wastewater contains a high fraction of particulate COD. With CSASP, the same amount of mass sludge can be retained in the system with almost 30% volume reduction compared to conventional activated sludge plants.

By keeping the majority of the biomass in the stabilization reactor, the nominal hydraulic retention time of the system decreases. However the sludge distribution factor must be high enough to ensure an acceptable effluent quality.

ENTEX’s Webitat fixed media modules can be used very effectively both as as part of a system that is being converted from contact stabilization to IFAS, or as part of the contact stabilization system itself.  In both configurations, the Webitat modules facilitate nitrification that would be otherwise difficult to achieve in traditional contact stabilization systems.  Below is an example of each configuration:

The Colony, TX - A Contact Stabilization Conversion

ENTEX converted the contact stabilization system at The Colony, TX to an IFAS system which uses 24 Webitat modules in the existing basins. The overall system capacity was increased by 33%, and the treatment was upgraded from simple carbonaceous removal to nitrification to meet the stricter effluent requirements.

Coeur D'Alene - A Contact Stabilization Update

When Coeur D’’Alene, ID decided that they needed to update their 6 MGD contact stabilization system to improve nitrification , they chose ENTEX.  Unlike The Colony which converted from contact stabilization to IFAS, Coeur D’Alene, ID decided to install the Webitat modules as part of the contact stabilization system.  Initially, five Webitat modules with BioWeb fixed media were installed. They were so effective that the city purchased another five modules the next year.  The challenge of nitrification at this mountain resort town was increased by the extreme cold temperatures routinely experienced.

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