Environmental Engineering Reference
In-Depth Information
12.7
Relation between dry matter content of digestate and amount of
solid fraction accumulated (Bauer
et al.,
2009).
Table 12.9
Typical separation performance of screw press separators
Percentage
of fresh
matter (%)
Degree of separation (%)
TS
VS
COD
NH
4
-N TN
PO
4
-P K
Solid fraction 10.0
48.1
56.3
48.8
9.2
17.0
21.8
10.0
Liquid fraction 90.0
51.9
52.4
51.2
82.0
83.0
78.0
90.0
Source: KTBL (2008).
certain circumstances (Westerman and Bicudo, 1998). Chemical precipita-
tion of animal manure involves the addition of chemicals to alter the
physical state of dissolved and suspended solids to facilitate removal (Zhang
and Westerman, 1997; Westerman and Bicudo, 1998).
12.3.4 Further processing of the solid fraction
After solid-liquid separation and depending on the feedstock type, the solid
fraction can be either directly used as a soil improver or it can undergo
further processing. The latter includes composting or further drying.
Composting
Composting will require additional organic fibrous material (such as
woodchips) as the digestate is usually too wet and too dense for direct
composting. A special application of composting is vermiculture using
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