Organic Waste Recycling

Biofuels production 183

Table 4.15 Characteristics of the UASB process (adapted from Weiland and Rozzi 1991)

Advantages Disadvantages

High organic removal capacity

Short HRT

Low energy demand

No need of packing media

Long experience in practice

Granulation process difficult to control

Granulation depends on wastewater properties

Start-up eventually needs granular sludge

Sensitive to organic and hydraulic shock loads

Restricted to nearly solid free wastewater

Ca2+ and NH 4 + inhibit granular formation

Re-start can result in granular flotation

Figure 4.16 Upflow anaerobic sludge blanket digester

4.4.3 Trouble-shooting

All biogas digesters will have problems sooner or later with their structure
components and in the operation and maintenance. Tables 4.18 and 4.19 deal
with problems associated with the dispersed-growth digesters, their causes and
remedies; while Table 4.20 deals with those of the attached-growth digesters,
i.e. anaerobic filters and UASB.

Liquid inlet

Settler/gas

separator

Liquid

Sludge blanket

Liquid outlet

Gas outlet