Manure handling and disposal in the livestock industry is one of the critical factors affecting cost and viability in a highly competitive market.
Effective waste handling can bring higher revenues from a previously resource-intensive operating expense.
The separation of manure into its solid and liquid components is important for two reasons.
Firstly, the value of dry manure is much more than that of the wetter kind.
Secondly, dry manure solids' transportation is practical and cost-effective compared to manure cost with a large water percentage.
Besides, the solids' physical separation reduces the phosphorus, which is crucial for the separated water's disposal consideration.
The separation of manure is the process of fractionating the manure into its liquid and solid phases. Separated manure sludge yields more value as a fertilizer and is easy to transport.
The water separated from the manure is mostly free of solids and nutrients, making it suitable for disposal.
Physical means of manure separation range from gravity-separation in lagoons to media separation devices (presses) and mechanical separator centrifuges.
Though each of these separation methods has a role in the livestock industry waste management, the decanter centrifuge is the most durable, cost-effective long-term solution.
A manure centrifuge separates manure solids from the water using high centrifugal forces over 3,000 Gs. The solids are heavier and settle out to the rotating bowl wall.
The relatively lighter water stays in the center and flows out the liquid end. The rotating conveyor scrapes the manure solids to the solids' end of the bowl.
It is important to note that most Phosphorus is bound to the solids and therefore ends up the separated solids. About 50% of the Nitrogen is retained in the liquid manure.
The introduction of some chemical flocculant enhances the separation process allowing for smaller particles, less than 50 µm to be separated.
The following are the specifications for a typical Alfa Laval decanter centrifuge for manure separation.
|Processing Capacity||25 GPM on Untreated Liquid Manure|
|Centrifuge Type||Horizontal, Scroll Type Decanter Centrifuge|
|Bowl Speed||4,000 RPM|
|Centrifugal Force (RCF)||3,150 Gs|
|Scroll Differential Speed||6 ~ 50 RPM|
|Gear Box (Torque & Type)||2.5 kN-M; Planetary|
|Motor Power||15 HP (11 kW)|
|Dimensions & Weight||3' x 8' x 5' (H) 2,500 Lbs|
Centrifuges offer many advantages over other mechanical separation devices like filter presses, belt presses, etc.