This is probably fine for non-industrial wastewater tbh. Feces, urine and biodegradable toilet paper aren't putting anything in the ocean that isn't already there in vast quantities.
It's honestly not so wonderful an idea when you're downstream of it, which given the Med has a significant and continuous in-flow, means that people along the Costa del Sol swimming in the sea are probably having more than their fair allowance of Gibraltarian effluent.