title: The effect of different aeration conditions in activated sludge--Side-stream system on sludge production, sludge degradation rates, active biomass and extracellular polymeric substances.
abstract: On-site minimization of excess sludge production is a relevant strategy for the operation of small-scale and decentralized wastewater treatment plants. In the study, we evaluated the potential of activated sludge systems equipped with side-stream reactors (SSRs). This study especially focused on how the sequential exposure of sludge to different aeration conditions in the side-stream reactors influences the overall degradation of sludge and of its specific fractions (active biomass, extracellular polymeric substances (EPS), EPS proteins, EPS carbohydrates). We found that increasing the solid retention time from 25 to 40 and 80 days enhanced sludge degradation for all aeration conditions tested in the side-stream reactor. Also, the highest specific degradation rate and in turn the lowest sludge production were achieved when maintaining aerobic conditions in the side-stream reactors. The different sludge fractions in terms of active biomass (quantified based on adenosine tri-phosphate (ATP) measurements), EPS proteins and EPS carbohydrates were quantified before and after passage through the SSR. The relative amounts of active biomass and EPS to volatile suspended solids (VSS) did not changed when exposed to different aeration conditions in the SSRs, which indicates that long SRT and starvation in the SSRs did not promote the degradation of a specific sludge fraction. Overall, our study helps to better understand mechanisms of enhanced sludge degradation in systems operated at long SRTs.
authors: Eawag: Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland; Institute of Environmental Engineering, ETH Zürich, 8093 Zürich, Switzerland.
authors: Jonathan
authors: J
authors: Habermacher
authors: Eawag: Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland; Universidade Federal do Rio Grande do Sul, CNPq, Av. Bento Goncalves 9500, Porto Alegre, Brazil.
authors: Antonio Domingues
authors: AD
authors: Benetti
authors: Eawag: Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland; Institute of Environmental Engineering, ETH Zürich, 8093 Zürich, Switzerland. Electronic address: nicolas.derlon@eawag.ch.
authors: Nicolas
authors: N
authors: Derlon
authors: Eawag: Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland; Institute of Environmental Engineering, ETH Zürich, 8093 Zürich, Switzerland.
authors: Eberhard
authors: E
authors: Morgenroth
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis; D018533:Biomass; D019149:Bioreactors; D011108:Polymers / Q000032:analysis / Q000737:chemistry; D012722:Sewage; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater
chemical_list: D000255:Adenosine Triphosphate; D011108:Polymers; D012722:Sewage; D062065:Wastewater
keywords: EPS; Endogenous decay; Exoenzymes; Side-stream reactor; Solid retention time; Starvation