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The accelerated carbonation of high Ca content Municipal Solid Waste Incineration (MSWI) fly ash was investigated with an L:S ratio of 0.25:1 to study the effect of accelerated carbonation on the leaching of critical heavy metals (As, Cd, Cu, Zn, Sb, Pb) in the fly ash. The results of XRD analysis showed after carbonation the peaks of Ca(OH)2 and CaClOH disappeared, while the peaks of CaCO3 became intense. After carbonation, the mineral phase of Pb was changed and Cu compound (CuTi2.05S4) was identified. The TG/DTA analysis showed the weight gain of the fly ash before 440 degrees C reached 5.70%. Furthermore, the SEM-EDS analysis confirmed the occurrence of the reaction of Ca(OH)2 (s) + CO2 (g) --> CaCO3 (s). The TCLP test of carbonated fly ash revealed that the leaching concentration of the critical heavy metals, except Cd, decreased within the carbonation time of 2 h. When the carbonation time was longer than 50 h, the leaching concentration of critical heavy metals, except Ph were higher than that of un-carbonated fly ash.

The changes of sludge disintegration degree, microbial activity and particle size were examined synchronously, and the relationships between the changes and the effect of ultrasonic parameters on microbial activity were also analyzed. The results show that the process of ultrasonic sludge treatment can be divided into two stages: at the first stage, sludge flocs are disrupted into small micro-floc aggregates with the diameter of 10-20 microm, the extracellular organic substances are dissolved, bacteria are dissociated from flocs, and the microbial activity is enhanced; at the second stage, the micro-floc aggregates are disintegrated further into bacteria bodies with the diameter less than 10 microm, the intracellular organic substances are released, and the microbial activity are decreased. The two stages are not entirely separated because sludge is inhomogeneity. When sludge disintegration degree is lower than 20%, sludge floc disruption is the main effect and the microbial activity can increase over 20%; when sludge disintegration degree is between 20%-40%, some bacteria are hurt and the microbial activity can increase by less than 20%; when sludge disintegration degree is over 40%, most bacteria are damaged and sludge activity would decrease quickly. Because low energy ultrasonic can disrupt sludge floc with no damage to microorganism in a long treatment duration time, it is suitable to stimulate sludge microbial activity.

An experimental work was carried out to investigate the effect of additives (clay and coal fly ash) and washing-pretreatment on the stabilization of critical heavy metals (Cd, Cu, Zn, Pb, Cr, Ni) during a sintering process of municipal solid waste incinerator (MSWI) fly ash. The proportions of the three constituents were varied to adjust the mixture compositions. The washing time were 8 h, 16 h and 24 h. The material was compacted in cylindrical specimens at 3 kN and treated at 1,100 degrees C for 4 h. When the clay content was increased to 70%, the stabilized ratio was increased from 16.96% to 28.42% for Cd, from 10.58% to 37.02% for Pb, from 46.38% to 55.14% for Cu, from 42.14% to 64.47% for Zn, but the stabilized ratio of Ni and Cr was decreased. When coal fly ash was increased in the MSWI fly ash, the stabilized ratio was decreased from 16.96% to 4.67% for Cd, increased from 46.86% to 81.43% for Cu, but the addition of coal fly ash did not increased the stabilized ratio of Zn, Pb, Ni and Cr. Washing pre-treatment increased the stabilized ratio of Cd, Cu and Pb significantly. The leaching behavior of the heavy metals in the sintered products was studied by the toxicity characteristic leaching procedure (TCLP), the results showed that the leaching concentration of the six heavy metals were very low.

Both cement rotary kiln co-processing hazardous wastes and cement solidification/stabilization could dispose heavy metals by fixation. Different fixation mechanisms lead to different fixation effects. The same amount of heavy metal compounds containing As, Cd, Cr, Cu, Pb, Zn were treated by the two kinds of fixation technologies. GB leaching test, TCLP tests and sequential extraction procedures were employed to compare the fixation effects of two fixation technologies. The leached concentration and chemical species distribution of heavy metals in two grounded mortar samples were analyzed and the fixation effects of two kinds of technologies to different heavy metals were compared. The results show the fixation effect of cement rotary kiln co-processing technology is better than cement solidification/stabilization technology to As, Pb, Zn. Calcinations in cement rotary kiln and then hydration help As, Pb, Zn contained in hazardous wastes transform to more steady chemical species and effectively dispose these heavy metals compounds. Cr3+ is liable to be converted to much more toxic and more mobile Cr6+ state in cement rotary kiln. And so Cr wastes are more fit for treatment by cement solidification/stabilization technology. The work could provide a basis when choosing disposal technologies for different heavy metals and be helpful to improve the application and development of cement rotary kiln co-processing hazardous wastes.

In order to enhance the degradation efficiency of waste activated sludge (WAS) in conventional aerobic digestion, various ultrasonic assisted treatment methods were investigated including ultrasonic disintegration of influent sludge, ultrasonic improvement of influent sludge activity and ultrasonic disintegration of return sludge. Firstly the effects of ultrasonic sludge treatment were studied to choose appropriate ultrasonic parameters, and then the experiments of aerobic digestion with different ultrasonic treatments were carried out. The results show that 1.0 W/mL, 10 minutes ultrasonic treatment can increase soluble chemical oxygen demand (SCOD) in the supernatant phase of sludge sample by 5.4 times and decrease total suspended solid (TSS) by 16%; 0.05 W/mL, 10 min ultrasonic treatment can increase the specific oxygen uptake rate (SOUR) of sludge sample by 29%. The two kinds of ultrasonic influent sludge pretreatment can't improve aerobic digestion effectively. Ultrasonic return sludge disintegration can enhance the volatile suspended solid (VSS) degradation ratio by 15%. Furthermore, the settlement performance of digested sludge is still good and the pollutant concentrations of supernatant phase increase slightly. So ultrasonic return sludge disintegration is considered as the most appropriate assisted treatment mode for aerobic digestion.

Technical parameter, condensed steam water quality and flue gases were studied and organic compound hydrolysis mechanism was discussed. During experimental study, observed that the relationship between water content of sewage sludge and residence time have a negative exponential function. The condensed steam water has a high-concentration organic content. Total organic carbon (TOC), volatile fatty acid (VFA) and NH3 -N of the water were very high and the pH value was between 9 and 9.5. VFA and NH3 -N come from two sections: (1) In the 110 - 130 degrees C temperature range, hydrolysis of protein occurred with the formation of VFA and NH3 -N; and (2) In the 140 - 150 degrees C, fats hydrolyzed into VFA. There was no gaseous pollution produced in the whole experimental progress.

In order to ameliorate the dewaterability and degrease performance of restaurant garbage, and to improve the treatment effect, a complete trail series with 2 factors on 5 levels was implemented. The 2 factors were temperature and retention time respectively as the main influencing factors of hydrothermal process. By means of analyzing the variation of the resistance, dewatering rate and floatable oil content of the treated restaurant garbage, and constructing the solid grease extracting kinetics, the mechanism of impact of hydrothermal process on the dewaterability and degrease performance of restaurant garbage was studied. It showed that the dewaterability of the product decreases at the beginning, after heating for 40min, it begins to increase. Moreover, it increases more quickly as temperature increases. The optimal dewaterability of the treated garbage appears at 180 degrees C and heating for 100 minutes. As temperature rises and heating time increases, the degrease performance is improved. Furthermore, this trend becomes more remarkably as temperature increases. When the temperature and retention time reach 160 degrees C and 80 minutes respectively, most of the solid grease in the garbage is extracted out to become floatable oil which can be separated and recovered readily. Subsequently, the amount of floatable oil begins to decrease since chemical reactions such as the partial hydrolysis of the oil take place. Additionally, the extraction of solid grease from interior accords with first-order reaction dynamic model.