Rotary Distributors - Trickling Filters

A rotary distributor or trickling filter as it is also known, spreads incoming flow evenly, as a thin layer, over the surface of a rock filled basin. An electrical motor or the hydraulic impulse of wastewater leaving the distributor slowly rotates the assembly. Flow passes over the stones absorbing oxygen from the air in the voids of the filter bed. 

In this aerobic environment a microbial growth develops fed by organics in the wastewater. 

In time the lower layer of microbes do not get enough oxygen and shift to anaerobic endogenous metabolism. The underdrain system is a network of channels discharging into the main collection channel running down the middle of the unit. The settled sludge returns to the primary clarifier. 

Temperature can have an effect on performance. Rising wastewater temperature can increase the rate of metabolism whilst decreasing temperatures slow it down. The seasonal impact is more noticeable where extreme changes occur.

In conventional use there are two types of trickling filters, low-rate filters and high-rate filters. Low rate trickling filters depend on incoming flow for operation, a device called a dosing siphon is used to regulate flow onto the filter bed. High-rate filters incorporate recirculation.

The main advantages of a rotary distributor/trickling filter is its basic simplicity, low power consumption and ease of operation and maintenance.