A review of the current literature indicates that freezing drastically alters the dewatering characteristics of alum sludges. However, the degree of alteration varies among different sludges and consequently laboratory experimentation is necessary to determine its effectiveness in dewatering a specific sludge.

The results of the analyses performed on samples collected from the water treatment plant serving the Elgin Area Water System confirm that natural freezing is a satisfactory method for dewatering the alum sludge produced at this plant.

It would appear that two lagoons, each having a surface area of one and a quarter acres could be constructed to treat the sludge. One lagoon will store the annual volume of sludge discharged from the sedimentation basins and the other will receive the sludge that will be transferred from the first lagoon during the winter months. The freezing and dewatering process would take place in this second lagoon. The clear water obtained after the frozen sludge has thawed would be recycled with the raw water for further treatment.

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© CAWQ 1974