Abstract |
Tertiary treatment of municipal sewage with lime effectively removes phosphate but generates considerable quantities of sludge and a sludge disposal problem. Evaluation of technical and economic aspects of potential sludge utilization, or disposal concepts considered agricultural applications, conversion of sludge to products of known market value, and transporting sludge from the plant site by various means. The phosphate industry appeared to offer the greatest potential for use of the sludge provided sludge phosphate content could be enriched. Methods considered for phosphate enrichment were: thermal beneficiation, carbonation, and calcining/slaking. In areas where the magnesium content of wastewater is relatively high, sludge processing to recover both phosphate and magnesium could be economical. Preliminary cost estimates are presented for several levels of process complexity in liming secondary effluent with potential recovery of lime and phosphate. A summary of transportation costs, by various means, for removal of sludge from the treatment plant site is also presented. (Modified author abstract) |