Relevant Statutes:
The Deposits in the Sea (Public Registers of Information) Regulations 1996
It is prohibited to dispose of any garbage, except ground food, into the sea from offshore installations , or from any ship alongside or within 500 m of the installation.
Synthetic materials floating or submerged are impervious to rot and create a hazard. Ropes and other cables can foul propellers and present a very real hazard to divers. Plastic sheeting, bags and containers can block cooling water intakes and heavy objects can be moved considerable distances. Special precautions should be taken to prevent the loss of such materials when being towed. and every reasonable attempt should be made to recover them.
Food Waste
Food waste is excepted provided it is ground (comminuted is the word used in the regulations) and passed through a 25 rum mesh There is no mention of sewage in the regulations and it appears it fans into the same category as waste food.
Reception Facilities
Harbour Authorities, or in the case of terminals, terminal operators have a duty to provide adequate reception facilities for garbage from ships for which they are allowed to make a reasonable charge.