title: Effects of particulate and soluble substrates on microfauna populations and treatment efficiency in activated sludge systems.
abstract: To determine the effects of particulate and soluble compounds on microfauna populations and treatment efficiency in activated sludge systems, two experimental wastewater treatment plants were set up and evaluated for a period of five months. The plants were fed with pre-flocculated domestic sewage enriched with starch or glucose as model substrates of particulate and soluble organic matter, respectively. It was observed that the starch-enriched system presented lower abundance of filamentous bacteria that turned into a better sludge sedimentation. Mean sludge volume index (SVI) values for the starch and glucose-enriched systems were 54+/-24 and 885+/-845 mL g(-1), respectively. Although no differences in organic matter removal were detected between the systems, nitrification and denitrification were higher in the starch-enriched system, which is likely to have been the result of its more compact flocs. The mean ammonia-N effluent concentrations for the starch and glucose-enriched systems were 4.7+/-5.7 and 16.2+/-9.7 mg L(-1), respectively, whereas the nitrate-N concentrations were 20.1+/-10.8 and 30.8+/-12.2 mg L(-1), respectively. Concerning microfauna analysis, ciliated protozoa specifically, attached ciliates were the dominant microfauna group in both treatment systems, whereas metazoa, particularly Lecanidae rotifera, were more abundant in the starch-enriched system. Lecanidae rotifera abundances above 400 ind mL(-1) reduced the mean floc area from 60 to 20mm(2) without affecting sludge settleability in the starch-enriched system. Finally, the reduction in floc area caused by metazoa feeding led to effluents of lower nitrogen quality, although no differences in sludge production were detected.
authors.affiliation: Dpt. Enginyeria Hidràulica, Marítima i Ambiental, Universitat Politècnica de Catalunya, Jordi Girona 1-3, 08034 Barcelona, Spain.
authors.forename: Jaume
authors.initials: J
authors.lastname: Puigagut
authors.forename: Humbert
authors.initials: H
authors.lastname: Salvadó
authors.forename: Xavier
authors.initials: X
authors.lastname: Tarrats
authors.forename: Joan
authors.initials: J
authors.lastname: García
mesh_terms: D000641:Ammonia / Q000378:metabolism; D000818:Animals; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005947:Glucose / Q000494:pharmacology; D010316:Particle Size; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology* / Q000469:parasitology; D012995:Solubility; D013213:Starch / Q000494:pharmacology; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012722:Sewage; D000641:Ammonia; D013213:Starch; D005947:Glucose