Representative van Krevelen diagrams showing all formula classes for (a) primary effluent, (b) UCT secondary clarifier effluent, (c) final effluent, and (d) Ostara effluent samples determined using positive mode FT-ICR MS. The rectangles indicate regions associated with (1) lipids, (2) proteins, (3) aminosugars, (4) carbohydrates, (5) condensed hydrocarbons, (6) lignin, and (7) tannin.