Environmental Engineering Reference
In-Depth Information
Example 10.35
Problem:
Biosolids are currently applied to a site twice annually. Based
on the lead content of the biosolids, the maximum number of applica-
tions is determined to be 135 applications. Based on the lead loading
and the application rate, how many years can this site be used?
Solution:
135 applications
2applications pe
Site Life
=
=
68 years
r year
Note:
When more than one metal is present, the calculations must be
performed for each metal. The site life would then be the lowest value
generated by these calculations.
10.9 ChaPTer revieW QuesTions
10.1
What is the advantage of thickening biosolids before they move
on in the treatment process?
10.2
Which thickening process is best for thickening process residu-
als from primary treatment?
10.3
Which thickening process is best for thickening process residu-
als from secondary treatment?
10.4
Name three devices that can be used to thicken waste activated
sludge.
10.5
Name three factors that affect the performance of the gravity
thickener.
10.6
Name three processes that use biological activity to stabilize
wastewater solids.
10.7
When operating an aerobic digester, the dissolved oxygen level
should be maintained at
mg/L or higher.
10.8
What is the normal operating temperature of a heated anaerobic
digester?
10.9
Any daily temperature change of more than °F
will cause the anaerobic digester production of methane gas to
decrease.
10.10 The supernatant contains 340 mg/L volatile acids and 1830 mg/L
of alkalinity. What is the volatile acids-to-alkalinity ratio? Based
on the ratio, is the digester operating properly?
10.11 The digester is 40 ft in diameter and has a depth of 25 ft. Solids
are pumped to the digester at the rate of 5000 gpd. What is the
digestion time based on flow?
10.12 The primary treatment residual solids pumped to the digester
contain 70% volatile matter. The digested biosolids removed from
the digester contain 48% volatile matter. What is the percent vol-
atile matter reduction?
