In 1986 a pilot-scale sludge freezing bed was constructed. This bed was operatedover the next three years using both an aerobically and aerobically digested sludges. These tests demonstrated that both sludges can be effectively dewatered by this process. The final solid contents were 39.3% and 24.5% for an aerobically digested and aerobically digested sludges, respectively. The quality of the meltwater was similar to raw waste water. Odors were not a problem if the meltwater was drained away as quickly as it formed. Both sludges were easily removed with a front-end loader. The actual depth of sludge frozen and thawed in the bed during each year of operation was very close to that predicted by design models. Some northern water treatment plants have successfully used natural freezing thawing in their lagoons or drying beds.
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