Grease Separator Calculation

The Water Authorities have been demanding calculation of FOG separators and rejecting all calculations. I discovered the European method of NS and copied it and inserted my figures but without really understanding it. Now I took a minute to learn what it is about, and learnt that NS is the throughput in liters per second. This method is valid for surface runoff, and a 2100 Romold fuel separator's NS is 6 lt/sec.

But kitchen flows are much lower in the order of 0.1 lt/sec. So the NR calculation is not valid for food industry - or is it? - , but they have been accepting my calculations. Apparently no one in the Water Authority+Ministry of Environment +Ministry of Health knows how the calculation is done. My dilemma, now, consists in how to keep them satisfied in a situation where the regulators have not the vaguest idea of the method. I'll continue with the successful pretending of how to calculate separator volume according to the desired system. I certainly shall not try to explain or teach them. That is one of the disadvantages of being too clever.