Heat Loss on Stone and Plastic Media Trickling Filters

ABSTRACT Temperature surveys were conducted on three conventional low‐rate stone media trickling filter plants, typical of those used in the United Kingdom, and one set of shallow (1.8 m) structured plastic media filters was surveyed. Filter feed, effluent and ambient air temperatures were continuously monitored for 6–13 months and covered winter conditions in all cases. A strong link was observed between measured heat loss from the effluent and the convective airflow driver, defined as the temperature differential between the wastewater feed and ambient air. The relationships were quantified for stone and plastic media to produce models that describe the observed heat loss in terms of this temperature differential, hydraulic load in the case of the plastic media model and media depth. Plastic media was found to have a higher cooling capacity and lacks the thermal inertia associated with traditional stone media units. Results and potential mechanisms are discussed.