In addition to the Acorn Environmental/Bord Na Mona plant we have just finished uprating, we looked at an overloaded Titan/Entec/Kingspan plant last weekend, as shown above.
The evident maldistribution of effluent to the top media bale in the pic is as a result of the cack-handed attempt by another company to reset the airlift flow rates. This and other inexpert interventions cost the client £750 ex VAT for two hours of work, and resulted in his effluent going from a just failing level at 30:30:20 (BOD:SS:NH4) to a threat of prosecution 300:300:40 standard.
As is so often the case, the monkey passing himself off as an engineer failed to get to the bottom of the problem, which is a combination of biological overloading, a problem with one of the airlifts, intermittent and very high pumped flows, and high levels of untreatable solids being put to drain on the site. Other than the biological overloading, these were all fixable on a one-day visit.
British Water's guidance for users of package plants should be given to all new and existing owners - my advice on what do do if your package plant misbehaves is also worth reading. Better yet, read them both before you buy a plant, and avoid problems in future.