Review of Techniques for Treatment and Disposal of Phosphorus-Laden Chemical Sludges

摘要

The report summarizes the effects of phosphorus removal by chemical addition on sludge handling and disposal options at full-scale wastewater treatment plants. American and Canadian plants which generate phosphorus-laden chemical sludges were surveyed by questionnaire, and 174 responses were received. Investigations at selected plants that were using a variety of phosphorus removal chemicals, points of chemical addition, and sludge treatment/disposal methods were conducted. The plant operating experiences have shown that all of the various sludge treatment unit processes for thickening, stabilization, conditioning, dewatering, and reduction are adversely affected by phosphorus removal. The adverse effects result from both increases in sludge quantity and changes in sludge characteristics. The adverse impacts are reduced when adequate capacity is available to handle the increased sludge quantity. However, many plants have inadequate capacity, and therefore have been forced to find innovative solutions to problems. This report documents such problem-solving attempts and the results achieved. It also compares the various sludge handling alternatives, and finds that relatively few problems have been encountered with pressure filtration of iron sludges, flotation thickening of iron and aluminum sludges, thermal conditioning of iron sludges, and land disposal of lime sludges. The report contains a bibliography of literature dealing with phosphorus-laden sludges, with an indication as to the scope of each reference.