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. The Older CSF technology used a batch process to effect operations. One Batch is passed on top of BR1 in the trenches and TSS collected. Water quality was not immediately good and the process required constant recycling over the same shallow bioreactor to reach desired treatment standard. The BR1, its underdrain and CT1 attached to the system needed 1 day of holdup to reach desired result. Once the Trenches where water was being percolated were totally clogged the percolation rates reduced (typically around 2 weeks of operations). At this point the BR1 was allowed to rest and the consumption of accumulated TSS by earthworms was started. In this time the water was diverted into BR2 with similar recycling protocol. 

Note that the BR1/BR2 in CSF system is designed for peak flows + recycle flow from the CT and  each BR1/BR2 were typically 2000 sqm/MLD each or more (during operations only 50% BR1 is actively used allow for TSS deposited over the previous cycle to dry off for manual harvesting) 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 design is better suited for batch operations especially for BNR.  CSF technology is suited for very small plants typically less than