Organic Waste Recycling

Composting 125

General description Digested sewage sludge is mixed with wood chips (1:3 volume ratio) in windrows 1.8 m high and 2.1 m wide. The windrows are turned daily for at least 2 weeks, then they are spread out, dried, and cured for 30 days. The wood chips are screened out for reuse The sludge (25% solids) mixed with bark (1:3) and composted in windrows for at least 21 days. In general, temperatures of 50-75

°C are

maintained for at least half of this time (Full-scale experimental plant) The sewage sludge (25-30% solids) was mixed with straw (1:1 volume) and composted in windrows, which were turned eight times for 3 months. At the end of this time the com

post was read

y for use. Tem

peratures of 55-60

°C were

Experiment. Digested sludge was mixed with straw at a ratio of 1: 1.25 in windrows for 6 weeks during which temperature of 65-70

°C

were achieved.

Raw material Sewage sludge and wood chips Raw dewatered sewage sludge and bark Raw dewatered sewage sludge and straw Digested sludge and straw

Table 3.3 Non-reactor composting systems (continued) Composting system