降解和压缩作用下城市生活垃圾的持水量变化

在自制的城市生活垃圾降解-压缩-渗流仪中开展了5组持水量试验，分别研究不同温度和逐级递增应力条件下新鲜高厨余垃圾的持水量随时间的变化，新鲜高厨余、新鲜无厨余和基本降解垃圾的持水量随应力的变化.试验结果表明：在恒定应力条件下，新鲜高厨余垃圾的持水量随时间呈指数下降，即MRC=a-b（1-exp（-ct^d））；在应力10kPa和室温（0～27℃）条件下，持水量下降较慢（c=0.003，d=1.18）；在应力10kPa和恒温（40±3℃）条件下，持水量下降较快（c=0.173，d=0.601）；应力从50kPa逐级递增至100kPa、200kPa和400kPa后，持水量分别瞬时下降3.0%、2.3%和1.9%；新鲜高厨余、新鲜无厨余和基本降解垃圾的持水量均随应力的对数呈线性下降，即MRC=m-n×lg（σ）；当应力从10kPa增大至400kPa时，新鲜高厨余、基本降解和新鲜无厨余垃圾的持水量分别从63.0%、46.5%和37.9%下降至46.0%、35.3%和30.4%.通过对比分析国内外持水量试验结果，揭示了在相同应力条件下新鲜垃圾持水量随厨余含量的增加而增大、不同组分老垃圾持水量基本相同的规律.分析了生化降解和应力压缩对新鲜高厨余垃圾持水量的影响机理，并提出了增大新鲜高厨余垃圾脱水速率和脱水量的工程建议.

Variation of moisture retention capacity of municipal solid waste under the influence of degradation and stress

Five sets of moisture retention capacity (MRC) experiments were conducted in degradation-compression-permeation cells for municipal solid waste (MSW). The variations of MRC with degradation time under different temperature conditions and incremental stresses for fresh high food waste content (HFWC) MSW were characterized, and the variation of MRC with stress for fresh HFWC-MSW, fresh zero food waste content (NFWC) MSW and decomposed MSW (D-MSW) were determined. Based on the experimental results, the following findings were obtained:MRC of fresh HFWC-MSW decreased exponentially with the degradation time, i.e., MRC=a-b(1-exp(-ct^d)); the values of c and d were obtained as 0.003 and 1.18 under the stress of 10kPa and room temperature of 0~27℃, while 0.173 and 0.601 under the stress of 10 kPa and constant temperature of (40±3)℃. MRC of fresh HFWC-MSW sharply dropped 3.0%, 2.3% and 1.9% after the application of incremental stresses of 100kPa, 200kPa and 400kPa, respectively. MRC appeared to decrease linearly with an increase of logarithmic stress for fresh HFWC-MSW, NFWC-MSW and D-MSW, i.e., MRC=m-n×lg(σ). The MRCs of fresh HFWC-MSW, D-MSW and NFWC-MSW decreased from 63.0%, 46.5% and 37.9% to 46.0%, 35.3% and 30.4%, respectively, with an increase of stress from 10kPa to 400kPa. It was concluded from the analyses of reference data that the MRC of fresh MSW increased with the food waste content and the MRC of aged MSW with different compositions were basically consistent under a given stress. The influence mechanism of degradation and stress on MRC of fresh HFWC-MSW was discussed, and the practical implications were proposed to enhance the dewatering of fresh HFWC-MSW.