Temperature-dependent and surface specific formaldehyde degradation in submerged biofilters

This study investigated formaldehyde removal in submerged fixed media biofilters in commercial and pilot scale recirculation aquaculture systems. Steady removal of formaldehyde (F) was observed immediately after simulated therapeutic treatment in closed systems and complete removal occurred within 1-4 days depending on water temperature. Formaldehyde removal was dependent on available biofilter surface area, and comparable rates of surface specific removal (SSR) were observed in two different systems. SSR was positively correlated to temperature (Q10 = 3.4) with estimates of 2.1 mg F/(m2 h) at 5.7 °C to 6.5 ± 0.2 mg F/(m2 h) at 14.5 °C. The estimates for SSR of formaldehyde can be used to predict actual treatment and effluent concentration with more accuracy. Furthermore, the results allow calculation on biofilter removal capacity of formaldehyde, applicable for developing biofilters ensuring sufficient formaldehyde removal in effluent water.