As TooTallTim says it is a macerator. It is full of shit and piss and possibly dental floss/wet wipes/johnnies and tampons.
If it’s in trouble get it sorted soon as, because when those things go wrong, they can go very wrong
My worst experience of them is one backing up and then proceeding to fill up an eaves space for many days. Inevitably the lathe-and-plaster bulkhead gave up the fight and a shitpiss cocktail cascaded down the stairwell.
As TooTallTim says it is a macerator. It is full of shit and piss and possibly dental floss/wet wipes/johnnies and tampons.
If it’s in trouble get it sorted soon as, because when those things go wrong, they can go very wrong