5. Easy to empty and maintain.
6. Difficult materials, like water hyacinths, can also be digested in this type of plant.
7. High temperature even in warm climates.
Disadvantages of Bag Digester/Balloon Plants
1. Plastic balloons are easily damaged and susceptible to physical and mechanical
damage leading to shorter lifespan (2–5 years).
2. Difficult to repair.
3. High-grade plastic material is required to construct plant.
4. Insulation is quite difficult.
5. No local employment.
6. No scum removal technology.
3.7.1.6 Plug Flow Digester
The first report for plug flow digester was reported from South Africa in 1957 (Fry
1974). The design of the plug flow digester is very similar to bag digester. It contains
a concrete-lined trough, which is five times longer than its width and also insulated
with flexible gasholder (steel or fibreglass), reinforced concrete, or galvanized iron
sheet (Singh et al. 1987).
1. The digester is feed with manure at a constant rate.
2. The feed moves along the digester as a plug.
3. Gas outlet is presented on the top of the digester connected with gas collector.
Advantages of Plug Flow Digester
1. Simple to understand
2. Economically good and easy to operate
Disadvantages of Plug Flow Digester
1. Because of plug flow type, sometimes the parts of the waste material travel faster
than others.
2. Limited in applications with substances which floats or settles on the digester.
3. Difficult to clean if particles are settled or float.
Operating Temperature
Based on the temperature, the AD systems are divided into two types such as
mesophilic and thermophilic systems. The psychrophilic system is not suitable for
AD process (Vögeli et al. 2014).
Stages
The single and multistage systems are available in AD process. Multistage system is
comparatively advantageous than single stage, since it does not require the optimal
environmental conditions for both. In single-stage processes, all three stages of
anaerobic process occur in single digester (Tucker 2008), whereas in multistage
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6. Difficult materials, like water hyacinths, can also be digested in this type of plant.
7. High temperature even in warm climates.
Disadvantages of Bag Digester/Balloon Plants
1. Plastic balloons are easily damaged and susceptible to physical and mechanical
damage leading to shorter lifespan (2–5 years).
2. Difficult to repair.
3. High-grade plastic material is required to construct plant.
4. Insulation is quite difficult.
5. No local employment.
6. No scum removal technology.
3.7.1.6 Plug Flow Digester
The first report for plug flow digester was reported from South Africa in 1957 (Fry
1974). The design of the plug flow digester is very similar to bag digester. It contains
a concrete-lined trough, which is five times longer than its width and also insulated
with flexible gasholder (steel or fibreglass), reinforced concrete, or galvanized iron
sheet (Singh et al. 1987).
1. The digester is feed with manure at a constant rate.
2. The feed moves along the digester as a plug.
3. Gas outlet is presented on the top of the digester connected with gas collector.
Advantages of Plug Flow Digester
1. Simple to understand
2. Economically good and easy to operate
Disadvantages of Plug Flow Digester
1. Because of plug flow type, sometimes the parts of the waste material travel faster
than others.
2. Limited in applications with substances which floats or settles on the digester.
3. Difficult to clean if particles are settled or float.
Operating Temperature
Based on the temperature, the AD systems are divided into two types such as
mesophilic and thermophilic systems. The psychrophilic system is not suitable for
AD process (Vögeli et al. 2014).
Stages
The single and multistage systems are available in AD process. Multistage system is
comparatively advantageous than single stage, since it does not require the optimal
environmental conditions for both. In single-stage processes, all three stages of
anaerobic process occur in single digester (Tucker 2008), whereas in multistage
86
S. Elangovan et al.