Organic Waste Recycling

186 Organic waste recycling: technology and management

Remedy Outlet part of the plant should be packed in layers of soil of 30 cm thickness each, with

sufficient water,

after the construction of the digester is completed. This would increase the life of the structure and also reduce seepage loss to some extent. Pressure is neutralized when the plant is full. So where the water table is high the plant should always remain full. a) Scum should not be allowed to dry and should be forced down with a rod 2-3 times a week. b) Guide pipe should be rewelded and rivetted and guideframe, etc., should be checked before installing it in the digester.

Possible cause Lack of consolidation of soil on the outside of the digester wall, resulting in cavities in soil surrounding the masonry wall, and leading to the development of cracks in the digester wall. a) Faulty compaction of the bottom. b) Hydraulic pressure of ground water. a) Gas holder at the top becomes jammed in the digester due to drying of the scum in between the gas holder and digester and restricting movement of the holder. b) Guide frame gets loosened from its support and the holder cannot move freely.

Problem 1. Cracking of the digester wall due to hydraulic pressure from inside or from outside in horizontal gas plants. 2. Rising of the digester floor with the rise of ground water table. 3. Bursting of the digester with excessive gas pressure.

Digester

Table 4.18 Problems with the digester, gas holder, and pipes (adapted from Tata Energy Research Institute 1982)