5
Removal of carbon, nitrogen and phosphorus from the separated
liquid phase of hog manure by the multi-zone BioCAST technology
=============================================
The removal of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) at concentrations
of 960
±
38 to 2400
±
96 mg/L, 143
±
9 to 235
±
15 mg/L and 25
±
2 to 57
±
4 mg/L, respectively,
from the separated liquid phase of hog manure by the multi-zone BioCAST technology is discussed.
Despite the inhibitory effect of hog waste toward microbial activities, removal efficiencies up to 89.2%
for COD, 69.2% for TN and 47.6% for TP were obtained during 185 d of continuous operation. The free
ammonia inhibition was postulated to be responsible for the steady reduction of COD and TP removal
with the increase of TN/TP ratio from 3.6 to 5.8. On the contrary, the increase of COD/TN ratio from 4.8 to
14.1 improved the removal of all contaminants. Nitrogen removal did not show any dependence on the
COD/TP ratio, despite the steady increase of COD and TP removal with this ratio in the range of 19.3–50.6.
The removal efficiencies of organic and inorganic contaminants increased progressively owing to the
adaptation of microbial biomass, resulting from the presence of suspended biomass in the mixed liquor
that circulated continuously between the three zones of aerobic, microaerophilic and anoxic, as well as
the attached biomass immobilized inside the aerobic zone.