The filter paper is too expensive for early game players and players who spawns in a biome without sugar cane,as collecting a lot of paper and charcoal seems is too difficult.Or I think you should add durability to the filter paper,as real life filter paper can be reused for a lot of times.
Also to encourage players to filter their water,dirty water should sometimes give hunger effects to players instead of always giving thirst to players,now no one cares about drinking dirty water.And please make the filter water clean.