Encouraging filament growth in an activated sludge treatment plant of the chemical industry

• Published in: Water research (Oxford) Vol. 34; no. 2; pp. 699 - 703
• Main Authors: Jobbágy, Andrea, Németh, Norbert, Altermatt, Rolf H, Samhaber, Wolfgang M
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.02.2000; Elsevier Science
• Subjects: activated sludge; Activated sludge process; Applied sciences; Biological and medical sciences; Biological treatment of waters; bioreactor arrangement; Bioreactors; Biotechnology; Chemical industry; Effluent treatment; Environment and pollution; Exact sciences and technology; filament growth; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; Industrial wastewaters; Pollution; sludge structure; total suspended solids; Wastewaters; Water treatment and pollution; Europe; bioreactor arrangement; filament growth; sludge structure; chemical industry; activated sludge; Activated sludge; Chemical industry; Bioreactor; Filament; Growth; Industrial waste water; Waste water purification; Flock; Biological purification
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(99)00149-9

An activated sludge treatment plant of Sandoz and Ciba–Geigy (currently Novartis) had difficulty meeting the effluent total suspended solids (TSS) permit requirement of 40 mg l −1. The plant commonly contained small, weak flocs with a characteristic lack of filaments. It was hypothesized that optimization of the plant’s bioreactor arrangement (i.e. the manner in which the feed was introduced into the six activated sludge basins connected in series) would lead to stronger activated sludge flocs with filamentous backbones, and that these flocs would provide a clearer supernatant and be less sensitive to changes in the wastewater composition. In order to optimize the bioreactor arrangement, bench-scale experiments were carried out using two model activated sludge systems operated simultaneously. A better floc structure and consequently lower effluent TSS concentrations were achieved in the system in which the influent was split between basins 1 and 2 rather than being introduced into basin 1. Furthermore, an excess sludge removal strategy of controlling the MLSS concentration proved to be more favorable than that of maintaining a stable solids retention time (SRT). Through implementation of the results in the full-scale plant, the effluent TSS values were stabilized well below the permitted level.