Abstract: A liquid treatment system and methods for removing contaminants from a liquid flow is disclosed. The treatment system having a treatment zone, a nanobubble diffuser system and a skimmer cassette assembly configured to remove the nanobubble and contaminant agglomeration from the liquid flow. The nanobubble diffuser system configured to diffuse negatively charged nanobubbles into the liquid flow whereby the nanobubbles adhere to positively charged contaminants and the nanobubble and contaminant agglomeration is urged to float towards a surface of the liquid flow in the treatment zone and be removed by the skimmer cassette assembly. In some embodiments, larger bubble diffuse systems are provided to increase the rise rate of contaminants. In some embodiments, the treatment system is a floating vessel. In some embodiments, the treatment system is configured to remove microplastics down to a size of about 1 mm and less.