Mechanical dewatering of sludge is an important part of sludge reduction. The key lies in the selection of sludge conditioning methods and the selection of dehydrators. There are four problems in the current choice of chemical conditioning and sludge mechanical dewatering models:
1 Principles and functions
The function of sludge concentration is to remove part of the water in the sludge by gravity or mechanical means to reduce the volume, and the function of sludge dehydration is to mechanically separate part of the interstitial water in the sludge to further reduce the volume. The moisture content of concentrated sludge can generally reach 94% ~ 96%. The moisture content of dewatered sludge can generally reach about 80%.
1 Principle and function of thermal drying
In order to meet the requirements for subsequent disposal of sludge, the water content of conventional mechanical dewatered sludge needs to be further reduced. Thermal drying of sludge refers to the process of removing moisture from sludge by evaporation through the heat transfer between sludge and a heat medium.
Background: According to data released by the Ministry of Housing and Urban-Rural Development, as of the end of September 2016, a total of 3,976 urban sewage treatment plants have been built nationwide with a sewage treatment capacity of 170 million m3 / d. Calculated based on 5 ~ 8t of sludge produced per 10,000m3 of domestic sewage (calculated at 80% moisture content), the current annual output of sludge in China exceeds 40 million tons, at a rate of 10% per year. The annual output of sludge will exceed 60 million tons (calculated based on 80% moisture content).
