| ACROSS | DOWN |
| 3 This stage of sewage treatment attacks particulate organic matter | 1 Produced by a sludge digester; make for great fertilizer |
| 4 These are not properly called 'sewers', apparently. | 2 Water coming in from primary treatment is sprinkled over a rock bed |
| 6 What settles out in the clarifier tank of an activated sludge system | 5 Colloidal or dissolved _______ material includes urine, soap or bacteria |
| 7 Sludge is mixed with something absorbent and then laid out to decompose | 8 Number of parts (sewage) per million constitutes 'raw sewage' |
| 9 Used to settle out grit | 11 Plastic bags, candy wrappers, diapers, maybe |
| 10 Last step in any water treatment process | 14 Dissolved _________ material includes nitrogen and phosphorus |
| 12 Digestion involved in a sludge digester (which processes raw sludge) | 15 Heating to kill pathogens |
| 13 Sand and gravel | 16 Particulate organic matter plus fatty castoff |
| 17 Tank of slow-moving water; particulate organics settle out and lipids float | 17 This kind of organic material includes toilet paper and banana peels |
| 19 Used to filter debris | 18 Also called 'biological treatment'; removes colloidal and dissolved organics |
| 20 Removed after secondary treatment to prevent eutrophication, often biologically | 21 Produced by a sludge digester; 2/3 methane, suitable for fuel |
| 22 System where detritus feeders are mixed with incoming water in an aerated tank | |
| 23 This stage of sewage treatment bars debris and grit |