There could be several ...
Published by Malcolm Fabiyi, President at Hydromantis, USA
There could be several reasons (i) plants receive more sewage than they were designed for (ii) in countries with power outages, aeration systems might fail to function for periods of time (iii) indequate provision for wet weather events and extreme weather conditions (iv) unmetered industrial discharges that increase the load (v) absence of online sensors - flowmeters, probes, etc - that provide advance or realtime warning on overloads and (vi) operator training