Trickling Filters: Reliability, Stability and Potential Performance,

Trickling filters can be best designed using pilot scale studies. Estimates of process performance can be made using simple models incorporating loading rate parameters and the reliability of process can be estimated for a given effluent standard using Figure 2. Process stability cannot be predicted, but it is clear that the lower the effluent BOD and suspended solids concentrations are the more stable a plant will be. High rate trickling filters can produce good quality effluent. In general the lower the organic and hydraulic loading rates the better the effluent quality will be. The performance history of low rate systems is quite good, but capital and land requirements are high and this will probably restrict their use to smaller communities even under current energy restrictions. High rate trickling filters can be competitive with activated sludge processes in terms of land and cost, but effluent quality is definitely lower than activated sludge processes. Application of 30-30 standards makes selection of high rate trickling filters risky unless further treatment is included. If standards are allowed to reflect a particular set of discharge conditions trickling filters would be a more widely used alternative.