Are Trickling Filters Making a Comeback?

By Jorge Iduate, Director of Engineering, Emeritus


There is a growing interest in the utilization of trickling filters in Wastewater Treatment Plant designs. This is even more evident in Latin-American countries. Why have trickling filters become popular again?


With the introduction of plastic filter media to replace the rock media, speed control, and more reliable rotary distributor mechanisms, the performance of trickling filters has been greatly enhanced. Controlling the speed of the trickling filter allows for extreme ranges of flow to the filter and high flushing intensity that helps remove any biomass on the media surface. Trickling filters offer many benefits that include a simple design and a cost-effective method of organic removal. Trickling filters are also very good for handling hydraulic peak loads.


Problems with trickling filters in the past included solids build-up on media surface, inconsistent dousing rates, poor ventilation, plugging, putrefaction, production of odors, and flies. Other problems common with old trickling filters included unreliable and high maintenance costs of rotary distributor center mechanisms. Some of these problems resulted from leaky seals and failed turntable bearings. In most cases, the main turntable bearing was located at the lower end of the rotary distributor mechanism and exposed to water. Any service performed would require a crane and complete removal of the rotary distributor mechanism, guy rods, and arms.


With DBS motor-driven rotary distributor center mechanisms, the performance of the trickling filters are greatly improved and the problems associated with the old rotary distributors are eliminated. The mechanisms include an enclosed gear drive with speed control. The turntable bearing is a heavy duty precision bearing specifically designed for combined thrust, moment, and radial loading. The entire power train, including the turntable bearing, is placed on top of the rotary distributor and away from damaging water and moisture. The seal-less design eliminates any leak problems. Large access ports are provided for easy maintenance and cleaning. The turntable bearing can be replaced without removing the rotary distributor and arms.


The cost to operate a trickling filter is very low. Motor-driven rotary distributors are powered by fractional horsepower electric motors. With the new filter media and reliable rotary distributor center mechanisms, trickling filters are more efficient than ever.