CSF

The raw sewage is screened through a fine screen and passed into a pre-sedimentation tank (PST) to remove fast settling grit from the inlet water. The  Organic TSS rich component is distributed evenly over a shallow cultured (0.4m-0.5m)  soil media. The top layer of BR1 in CSF arrests the organic suspended solids which are manually scraped off and manually transferred to Sludge drying bed  to be composted along with the grit from the PST. Note that the BR1 in CSF system is designed for peak flow and is typically 1500 sqm/MLD or more (during operations only 50% BR1 is actively used allow for TSS deposited over the previous cycle to dry off for manual harvesting) based on this only 50% of the BR1 is active and has to be accounted for during process design. In case the entire BR1 is used then after total clogging of the top of the reactor the TSS has to be scrapped off from top by resting the BR1 for 1 week or more. Failure to remove TSS from the top will allow the TSS to enter the Soil bed requiring replacement of the entire Soil Bed. The percolated water from BR1 is collected in CT1. Water from CT1 is percolated through BR2 (800 sqm/MLD) where denitrification is achieved via recycling from CT2 over BR2. The final treated water is disinfected as required using Chlorination, UV, Ozone or other techniques via a bleed stream from CT2.  BNR in the CSF process typically requires recycling. The Media in CSF process has to be sieved earth of less than 1mm size which can be ingested by earthworms for regeneration.  Given all the above the CSF-SBT design is better suited for batch operations especially for BNR.