We recently had to vacuum a large grease trap [It was a Rofo RGT2000] serving a daytime-only restaurant because the staff had been washing all the fatty deposits from the plates, and the walls of the fryers, down the drains.
We removed around 1,500 lt from the system which had built up over 4 months [some 12lt/day] since the previous ‘deep clean’. At the average organic loading of 55g fat per three course meal, this indicates over 2,000 lunches a day [the actual figure was in the region of 600 max / day]. This is a clear indication that staff had been pouring excess oil down the drain, probably because to capture and pour it into waste containers for re-cycling was just too much trouble.
Several factors came to light here:
There was absolutely no odour, even when the oil was stirred up – necessary as it was palm oil [shortening] based; and this material solidifies at below 18’C [it’s winter time here]. Hence the need for a powerful vacuum tanker/pump.
The stainless steel walls of the inner chambers of the trap were clean, and devoid of the customary oily ‘clagg’ one would expect to find. These factors indicate that the weekly added B220 powder was working as intended.
Because the solids retention baskets – there are two of them – were properly designed and a ‘snug fit’, no food particles had found their way into the stilling tank where they [customarily] settle on the floor, building up to a septic, anaerobic sludge responsible for most of the foul odours associated with grease traps.
Because of the efficiency of the solids baskets, they MUST be emptied at least every day...otherwise the trap will overflow.
However, efficient floor drains in a properly managed kitchen will alleviate this need to once a day – the baskets are large enough.
Management of staff and the commercial kitchen as a whole, was non-existent.