Ocean pollution Sources of ocean pollution Sludge dumping
By 1990, the United States alone had already given out 38 trillion liters of  into the waters along its coasts. Raw sewage is all the liquid and solid wastes that go down toilets and drains. After collecting in sewer drains, raw sewage goes through a 'treatment plant', where it is cleaned, and the solid waste is removed. Once the liquid is treated, it goes to nearby waterways. The remaining solid waste is called 'sludge'. This toxin and bacteria-filled sludge is often dumped into the ocean. The people who dump it in think it will sink to the ocean floor.