Which two criteria are used to control trickling filter operations?

The correct choice is based on the understanding that trickling filters are a type of biological treatment process used in wastewater treatment. In this context, organic loading refers to the amount of organic matter present in the influent wastewater, which directly impacts the biological processes occurring within the filter. Hydraulic loading, on the other hand, measures the volume of water being applied to the filter per unit area, affecting how effectively the filter can treat the wastewater.

Controlling both of these parameters is vital for optimal operation. If organic loading is too high, it could overwhelm the microorganisms in the filter, leading to inadequate treatment and possibly system failure. Similarly, if hydraulic loading is improperly managed, it can result in either insufficient contact time for the microbes to process the organic material or excessive water flow that could wash out the biomass from the filter.

While the other choices propose various factors that could be relevant in different contexts, they do not specifically address the key operational factors for trickling filters. For instance, filtration pressure and flow rate are more associated with mechanical filtration systems rather than the biological treatment processes employed in trickling filters. Similarly, while pH levels and oxygen content are important in biological treatment, they are not the primary criteria used to directly control the operations of trickling filters