How is organic loading for a trickling filter typically expressed?

Organic loading for a trickling filter is typically expressed as the amount of biochemical oxygen demand (BOD) per volume of wastewater being treated, over a specific duration. This is essential for evaluating the performance of the trickling filter and ensuring it is adequately handling the incoming organic matter.

The correct expression for organic loading is kg BOD/100m3xd (lb BOD/1000 ft3/d). This measure provides a standardized way to assess the quantity of organic matter that the trickling filter is expected to process, relative to the volume of wastewater being treated on a daily basis. By using this expression, operators can determine whether the filter is functioning effectively and how it might need to be adjusted based on the incoming organic load.

The other options do not provide the appropriate context for trickling filters. For instance, expressing organic loading as kg BOD (lb BOD) does not take into account the volume or the time component necessary to gauge the filter's performance accurately. Similarly, mg BOD/d (oz BOD/d) is too small of a measurement for typical wastewater applications, while expressing organic loading in terms of surface area (kg BOD/100m2xd) is more relevant to certain types of aerated biological processes rather