FEASIBILITY OF THE UPFLOW ANAEROBIC SLUDGE BLANKET
(UASB) PROCESS FOR THE TREATMENT OF LOW-STRENGTH WASTES
Gatze Lettinga. Professor
Department of Water Pollution Control
Agricultural University
Wageningen, The Netherlands
Johannes N. Vinken, Engineer
Adviesbureau Arnhem
Consulting Engineers
Wageningen, The Netherlands
Considerable efforts are and have been made in recent years in the Netherlands on the
research on anaerobic wastewater treatment. This research started at the Department of
Water Pollution Control of the Agricultural University in Wageningen and resulted in the
development of a new anaerobic treatment process, now known as the Upflow Anaerobic
Sludge Blanket (UASB) process [1, 2]. In a rather early stage the potentials of this treatment concept were recognized by the CSM- sugar beet company, and then as a result of
combined comprehensive research the process could be shown feasible at 6 m pilot plant
scale. Since that time also other universities participated in specific fields of the research
and, mainly as a result of financial injections of the Governmental Department of Environmental Protection, the UASB-process could be brought to full scale application in 1977,
that is five years after the first laboratory studies had been made [3]. At present anaerobic
wastewater treatment is an almost completely accepted technology in the Netherlands,
and the interests in the method with potential users has increased the last years accordingly.
In fact we ultimately have reached the situation that anaerobic treatment receives the
attention which it truly deserves (4|.
Anaerobic disgestion as a waste treatment method offers a number of significant benefits
over other wastewater treatment methods, whereas it in fact is accompanied with little
serious or insuperable drawbacks. Benefits and drawbacks of the anaerobic treatment process
have been summarized in Table I. As a matter of fact one of the most serious problems
in the use of anaerobic treatment for low strength wastes, being the retention of a sufficient
quantity of viable sludge under conditions of high loading, now seems to be solved as a
result of the development of the UASB-process and presumably also of the anaerobic filter.
Table I. Benefits and Limitations of Anaerobic Waste Treatment
Benefits
1. Low production of (stabilized) waste solids, and accordingly a low requirement of nutrients
2. No energy requirement for aeration.
3. Production of methane which is a high grade fuel.
4. Very high loading rates can be applied under favorable conditions.
5. Active adapted anaerobic sludge can be preserved unfed for many months without severe
deterioration in sludge properties.
Limitations
1. Anaerobic digestion is a rather sensitive process (e.g., for compounds such as CN~, CHC13
etc.).
2. The first start-up of the process requires a period of several weeks.
3. Anaerobic treatment is essentially a pretreatment method.
4. Little practical experience has been gained with the application of the process up to now.
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