Organic Waste Recycling

128 Organic waste recycling: technology and management

General description Reactor consists of a vertical tower with 10 floors one above the other. Each floor contains a hydraulically operated valve which allows material to be discharged to the next floor. Oxygen is introduced by force aeration.Dewatered sludge, recycled compost and ground bark mixed in proportions of 2: 2: 1 volume. Composting mixture is about 1 m deep on each floor. Residence time is about 3 days on each, giving a total reactor time of 30 days Two cells consisting of three horizontal decks. Horizontal ribbon screws extending the length of each deck recirculate ground refuse from deck to deck. Air introduced in bottom of cells. Three days composting followed by curing for 7 days in a bin. Reactor is a concrete tower called a “Hygiensator” which is divided into four separate vertical compartments. Residence time of 4-15 days depending on feed and temperature of 70-80

°C are achieved. Air is pulled out of top of

reactor. Screw extractor removes and agita

tes material from bottom of reactor.

Extracted material is recycled three to five times during compost period to avoid compaction at bottom. Curing period of 2-4 months. The digested sewage sludge is mixed with rice hulls and finished compost (1:1:1 volume) and fed into a trough where it is composted for 2 weeks by forced aeration and turning. This is followed 1-2 months of maturation. Tem

peratures reach u

p to 70

°C.

Raw material Dewatered sludge, recycled compost and ground bark Municipal refuse Municipal refuse, sewage sludge, bark, sawdust Sewage sludge and rice hulls and recycled compost

Table 3.4 Reactor composting systems (continued) Composting system Schorr “Biocell” System T.A. Crane Triga Trough fermenter