Composting sewage sludge of wastewater treatment plant

The sewage sludge of Shenzhen Binhe Wastewater Treatment Plant was used as the research object, the dry sludge and returned sludge as the water amendment, the leaves powder and woodchip as C/N and water conditioner, the four aerated static pile (ASP) systems (1.5 m×1 m×1.5 m) as the composting equipment, the sewage sludge composting process conditions were studied. The results showed that using the dry or returned sludge as water amendment to mix with the fresh sludge to the volume ratio of 1:1, the water content of the mixture could meet the composting conditions. Using leaves powder or woodchip as the C/N and water conditioner to mix with fresh sludge is more useful than using the dry or returned sludge, but it could increase the cost of the compost. For the different treatments the time the temperature of the compost over the 55°C is more than 12 d, and the compost satisfied the standard of harmless and stabilization. The two pilot-scale ASP systems (10 m×2 m×1.5 m) were used to confirm the conditions come from the small ASP systems experiment. The results indicated that one volume of fresh sludge mixed with one volume of dry or returned sludge the water content of the mix is appropriate for composting, but the volume ratio of 1:1 fresh sludge mixed with dry sludge is more effective than that of returned sludge and the compost could meet the standard of harmless and stabilization.