To solve the disposal problems of residual sludges, wastewater treatment sludge (WWTS) and drinkingwater treatment sludge (DWTS) were tested as components for producing ceramsite. Fe2O3, CaO, and MgO were the major basic oxides in WWTS and DWTS, so their effect on characteristics of ceramsite was also investigated to optimize the process. Results show that WWTS and DWTS can be utilized for producing ceramsite with optimal contents of Fe2O3, CaO, and MgO ranging 5-8%, 2.75-7%, and 1.6-4%, respectively. Ceramsite within the optimal Fe2O3, CaO, and MgO contents ranges was characterized using thermal analysis, X-ray diffraction (XRD), morphological structures analyses, and compressive strength measurements. Higher strength ceramsite with more complex crystalline phases and fewer pores can be obtained at 6%≤Fe2O3 ≤8%. Lower strength ceramsite with more pores and amorphous phases can be obtained at 5%≤CaO≤7%, which implies that excessive Ca2+ exceeds the needed ions for producing electrical neutrality of silicate networks. Ceramsite characteristics are not dramatically influenced by MgO because Mg2+ cannot destroy the unity of crystalline structures. This revolutionary technology of utilization of WWTS and DWTS can produce high performance ceramsite thus reducing costs of sludge disposal, in accordance with the concept of sustainable development.

An investigation was made to study the feasibility of recovering the Alum from coagulation sludges and reusing it in chemically enhanced primary treatment (CEPT) process to make the CEPT more cost-effective and recover the resource (Alum) efficiently. The optimum condition and efficiency of the acidification method for Alum recovery from coagulation sludge were investigated in the test. The results show that when the recovery rate of Alum reaches its highest level, 84.5%, the reduction rate of sludge is 35.5%. It turns out that the capability of recovered coagulant to remove turbidity, UV254 and COD are 96%, 46% and 53%, respectively. The results prove that the recovered coagulants could be used in CEPT and the efficiency of recovered coagulant to remove pollutants is similar to that of fresh coagulant. Although some substances will be enriched during recycle, they have little effect on the quality of treatedwastewater. The experiments verify that itwould be an advisable and cost-effectiveway to recover Alum from coagulation sludges in water treatment and chemical wastewater treatment, and it could be then recycled to CEPT as well as reduce sludge volume.

Making lightweight ceramsite with sewage sludge is a new effective approach for disposal of sludge. However, there is a concern as to whether the heavy metals such as Cr6+ in sewage sludge can be solidified in ceramsite after sintering. The configuration of Cr6+ in ceramsite was analyzed by X-ray diffraction (XRD) and leaching tests were conducted to determine the effects of sintering temperature, pH and H2O2 concentration on the stabilization of Cr6+ in ceramsite. The results show that leaching of Cr6+ changes little at temperatures above 900℃, and both pH and H2O2 concentration have some effects on the leaching of Cr6+. Leaching test results indicate that Cr6+ is stabilized in ceramsite and cannot be easily released to the environment again as secondary pollution, which eliminates the concern for its application. XRD analysis of ceramsite sintered at 1000℃ reveals that the main compounds of Cr6+ in ceramsite are Cr2O3 and FeCrO4. The test results provides a better understanding of the factors that affect the mobility of Cr6+, and show it is a safe way to make ceramsite with sludge as an additive.

Chemically enhanced primary treatment (CEPT) in municipal wastewater treatment is particularly suitable for rapidly growing cities. The focus on CEPT process now might be the cost of chemicals and disposal of chemical sludge. In this study, the potential application of adsorbent made from CEPT sludge in CEPT wastewater treatment was investigated in various conditions, such as the adsorbent dosage, pH, and dosing modes of ferric chloride and adsorbent. It was found that sludge-derived adsorbent was a good way of sludge disposal while enhanced pollutants removal rate and reduced the fresh ferric chloride dosage. With the use of 10.0mg L 1 of ferric chloride and 0.6 g L 1 of the adsorbent at the first stage simultaneously, the enhanced removal efficiencies of turbidity, UV254, COD, TP were 83.3%, 52.3%, 48.8% and 89.0%, respectively. The experiments showed that ferric chloride dose was reduced about 50%. The pH played a significant role in coagulation and adsorption process.