Use of the upflow sludge blanket (USB) reactor concept for biological wastewater treatment, especially for anaerobic treatment

TLDR

Recent Dutch research has focused on advanced anaerobic processes capable of treating low‑strength waste with short liquid detention times of 3–4 h. This paper evaluates laboratory, pilot‑plant, and full‑scale results of the UASB reactor concept. The study focuses on the UASB reactor’s operating characteristics and preliminary laboratory tests of the USB concept for denitrification and acid formation. The UASB reactor successfully treated 15–40 kg COD m⁻³ day⁻¹ at 3–8 h detention in pilot studies and 16 kg COD m⁻³ day⁻¹ at 4 h in a 200 m³ full‑scale plant, while USB trials showed effective denitrification and acid formation at high hydraulic and organic loading rates.

Abstract

In recent years considerable effort has been made in the Netherlands toward the development of a more sophisticated anaerobic treatment process, suitable for treating low a strength wastes and for applications at liquid detention times of 3–4 hr. The efforts have resulted in new type of upflow anaerobic sludge blanket (UASB) process, which in recent 6 m3 pilot-plant experiments has shown to be capable of handling organic space loads of 15–40 kg chemical oxygen demand (COD)·m−3/day at 3–8 hr liquid detention times. In the first 200 m3 full-scale plant of the UASB concept, organic space loadings of up to 16 kg COD·m−3/day could be treated satisfactorily at a detention times of 4 hr, using sugar beet waste as feed. The main results obtained with the process in the laboratory as well as in 6 m3 pilot plant and 200 m3 full-scale experiments are presented and evaluated in this paper. Special attention is given to the main operating characteristics of the UASB reactor concept. Moreover, some preliminary results are presented of laboratory experiments concerning the use of the USB reactor concept for denitrification as well as for the acid formation step in anaerobic treatment. For both purposes the process looks feasible because very satisfactory results with respect to denitrification and acid formation can be achieved at very high hydraulic loads (12 day−1) and high organic loading rates, i.e., 20 kg COD·m−3/day in the denitrification and 60–80 kg COD·m−3/day in the acid formation experiments.