Q794. If I have multiple anaerobic lagoons, do I need to report for each one?

A794.  Subpart II, 98.352 requires a facility to report CH₄ generation, CH₄ emissions and CH₄ recovered from treatment of industrial wastewater at each anaerobic process. For anaerobic reactors and lagoons, the rule states that facilities must calculate CH₄ generation using the volume of wastewater sent to an anaerobic treatment process and average concentration of COD or BOD₅ of wastewater entering an anaerobic treatment process with either equation II-1 or II-2.  Equations II-1 and II-2 include the variable MCF, or methane conversion factor. Reporters must use MCF of 0.8 for anaerobic deep lagoons (depth more than 2 m) or MCF of 0.2 for anaerobic shallow lagoon (depth less than 2 m).

If the multiple anaerobic lagoons include both deep and shallow lagoons, reporters must treat the lagoons as separate anaerobic processes and calculate methane generation using the appropriate MCF, wastewater flow, and BOD₅ or COD concentration.

Equations II-1 and II-2 also include terms for Flow_w, the volume of wastewater sent to the anaerobic process and for BOD_5,w  or COD_w, for an average concentration of organic material entering the anaerobic process. As required by §98.354 (d), the flow measurement location must correspond to the location used to collect samples analyzed for COD or BOD₅ concentration. If the multiple lagoons are either all deep or all shallow, and if the total flow into the multiple lagoons is measured at one point, and COD or BOD₅ are measured at that same point, you may treat the anaerobic lagoons as one process and need only report for that one anaerobic lagoon process. This methodology can apply to lagoons arranged both in series and parallel.