Dear  Cees Vallentgoed No ...

Dear  Cees Vallentgoed 

No more clogging risks expected by using these new fillings.
Your new filling as per design criteria no doubt,you may increase the circulation rate as well as flushing frequency.

A material with a specific surface area between 45 and 60 m2/m3 for rocks and 90 to 150 m2/m3 for plastic packing is normally used. Larger pores (as in plastic packing) are less prone to clogging and provide for good air circulation . Primary treatment is also essential to prevent clogging and to ensure efficient treatment. Trickling filters are designed primarily for  BOD removal. A structured ​plastic media ​comprising ​corrugated ​layers on a ​diagonal angle​will be much ​more resistant ​to clogging ​than mineral ​media ​ Treatment performances depend on wastewater characteristics, hydraulic and organic  loading, medium type, maintenance of optimal dissolved oxygen levels, and recirculation rates. A BOD  reduction of 60 to 85 % can be expected with loading rates of 1 kg BOD /m3/day  Bacterial reductions have been reported to be 1 to 2 logs of faecal respectively 60 to 90 % of total Coliforms

A trickling filter, also called trickling bio filter, bio filter, biological filter and biological trickling filter, is a fixed-bed, biological reactor that operates under (mostly) aerobic conditions. Pre-settled wastewater is continuously ‘trickled’ or sprayed over the filter. As the water migrates through the pores of the filter, organics are aerobically degraded by the biofilm covering the filter material.

Organisms that grow in the thin biofilm  over the surface of the media oxidize the organic  load in the wastewater  to carbon dioxide and water, while generating new biomass . This happens mainly in the outer part of the slime layer, which is generally of 0.1 to 0.2 mm thickness

The primary factors that must be considered in the design of trickling  filters  include

1. The type of filter media to be used.
2. The spraying system, and
3. The configuration of the under-drain system.
4. The flushing rate (or ​Spulkraft ​number) is also ​important.
5. ​Recirculation ​rate will ​normally help ​to reduce ​clogging. 

 The ideal filter material is low-cost and durable, has a high surface to volume ratio, is light, and allows air to circulate

.Physical adsorption of virus  on the biofilm  or elimination by predation are additional factors in pathogen elimination in trickling filters Total suspended solids  (TSS) removal is expected to be very low (due to the down-flow regime  and pre-settling  as well as removal of the solids from the effluent  is recommended. Because aerobic bacteria convert ammonia to nitrate some nitrification can also be achieved, depending on the organic loading rate to the filter, the temperature and the aeration. Total nitrogen removal varies from 0 to 35 %  while phosphorus removal of 10 to 15 % might be expected  However, the capacity for nutrient  removal of trickling filters  depends strongly on the operation conditions, and while some sources indicate a high removal of ammonia other indicate no capacity of trickling filters  for nutrients.

Regards,

Prem Baboo