best available technologies for manure treatment - Baltic Green Belt

Best Available Technologies for manure treatment baltic sea 2020
Best Available Technologies for manure treatment baltic sea 2020
ANNEX E: TABLES WITH SHORT DESPRIPTION OF LIVESTOCK MANURE TREATMENT TECHNOLOGIES
Best Available Techniques for manure treatment - for intensive rearing of pigs in Baltic Sea Region EU Member States Technical Report "Best Practice Manure Handling, Phase 2"
Ref No. 57 Nitrification-denitrification
Brief description
The nitrification-denitrification process converts the N in the slurry to free N, N
2
, a process that is commonly used in waste water
treatment facilities. Biological conversion of ammonia to N gas is a two step process. Ammonia must first be oxidized to nitrate; nitrate
is then reduced to N gas. These react ions require different environments and involve two tanks, an anoxic tank and an anaerobic
digestion tank. The first step in the process, conversion of ammonia to nitrite and then to nitrate, is called nitrification (NH3 NO2 NO3).
The process is summarized in the following equations:
-
NH
4
+ 3/2 O
2
NO
2
+ 2H+ + H
2
O
-
-
NO
2
+ 1/2 O NO
3
It is important to note that this process requires and consumes oxygen, and thus contributes to the BOD (biochemical oxygen demand).
The process is mediated by the bacteria Nitrosomonas and Nitrobacter, which require an aerobic (presence of oxygen) environment for
growth and metabolism of N. Thus, the nitrification process must proceed under aerobic conditions. The second step of the process, the
conversion of nitrate to N gas, is referred to as denitrification. This process can be summarized as:
-
NO
3
+ 5/6 CH
3
OH 1/2 N
2
+ 5/6 CO
2
+ 7/6 H
2
O + OH -
Description of the effect on
leaching (positive or negative) of
N and P
See the description for
composting, technology
references number 41 and 41A.
This process is also mediated by bacteria. For the reduction of nitrate to N gas to occur, the dissolved oxygen level must be at or near
zero; the denitrification process must proceed under anaerobic conditions. The bacteria also require a carbon food source for energy
and conversion of N. The bacteria metabolize the carbonaceous material or BOD in the wastewater as this food source, metabolizing it
to carbon dioxide. This in turn reduces the BOD of the sewage, which is desirable. However, if the sewage is already low in BOD, the
carbon food source will be insufficient for bacterial growth and denitrification will not proceed efficiently. In the aerobic digestion tank
the conversion of ammonia to nitrate and nitrite takes place. In the anoxic tank, microorganisms use the free oxygen in nitrate
compound as a source of energy. The process produces more bacteria and removes N from the slurry by converting it into free N gas,
which is released into the air. The system is build so that oxygen is provided to the slurry by way of tiny aerating bubbles provided by
diffusers.
Innovation stage
Investment price,
Basic Variable
Operational costs,
per tonnes
per kg saved N
or P leaching
Complexity of
implementation
Research
Pilot
Practice
Major references
No data No data
Condition for
leaching reduction
effect
CBMI, 2009 Scenarios II - V
Prices Low
Effect on leaching High
No data, however a Spanish plant visited by CBMI in June
2009 used 15-20 kWh per ton, alone for electricity, but
including separation and composting operations.
Certainty of information
Depends on the
situation of the
individual farm.
High – shall be implemented
as a community plant.
76
Side 78
76