During design of trickling filter, there are several factors that need to be taken into consideration to come up with a system best suited to your plant treatment needs and capacity. Following is the list of factors that will affect your decision.
- Hydraulic loading rate
- Incoming BOD of influent feed
- Depth of settling tank
- Recirculation ratio
- Needs for establishment of nitrifying bacteria
- Types of filter bed to use
- Ventilation system, either forced air or natural
Loading rate is one of the important aspects to consider before you come up with your trickling filter design. In order to optimize on efficiency, there should be a continuous growth of biomass and also on the sloughing of excess generated to maintain a well-balanced system. There are different dosing rates you can apply and basically the value can be obtained by multiplying the organic loading rate by 0.12. The rotational speed of the distributor is also another criteria and the speed in which it turns, is determined by the flow rate and also loading rate. A well-designed trickling filter system should have the wastewaste stream discharge from the nozzle to spread out evenly so that the idea is, to have the whole filter media bed uniformly covered.
Selection of filter media for your trickle filters must consist of material with high surface area to allow water to pass through freely without clogging. Typical packing can either be rock, redwood, plastic vertical flow plate and each media have different costs consideration and durability in mind. Air flow is another fundamental aspect towards successful operation of the filter. The driving force in an open system is draft plus natural wind. If the incoming wastewater temperature is lower than ambient air, then air will flow towards downward direction, which in terms of mass transfer factor, this is considered more economical.
