化学调理对市政污泥真空预压处理过程中低渗透层控制效果试验研究

Experimental study on inhibition effect of chemical conditioning on low permeability sewage sludge layer under conditions of vacuum preloading

由于市政污泥真空预压处理过程中排水板周围易形成低渗透层，从而降低污泥的排水效率，利用真空抽滤试验和装置模拟和研究在滤布上方（O～5cm）污泥中添加化学调理剂和改变土工布孔径2类措施对低渗透层的控制效果．抽滤过程中测试抽滤液总量、含固量及抽滤速度，试验结束后，对不同高度处的污泥柱体进行切片取样来测量污泥残余含水量．结果表明，增大土工布孔径不能显著改善污泥排水效果，滤饼在试验后1h会形成．采用氯化铁、氧化钙及粉煤灰组合调理剂整体排水效果最好，滤布上方（0-3cm）污泥残余含水量降到200％左右；采用氯化铁一阳离子聚丙烯酰胺或者氯化铁一壳聚糖组合调理剂可显著提高污泥排水效率，滤布上方（0—3cm）污泥含水量降到250％左右．在实际工程中可利用氯化铁、氧化钙及粉煤灰组合配方来调理污泥．

Due to the low permeability layers formed around drainage plates under conditions of sew- age sludge vacuum preloading can decrease the dewatering efficiency, vacuum filtration installations and tests are used to simulate and study the inhibition effects on the low permeability layers, taking two methods of adding different chemical conditioners into the sludge above the filter （0 to 5 cm） and changing pore-opening size of geotexiles. During the filtration process, cumulative amount of filtration（CAF） ,filtration rate（ FR）, and solid content（SC） are calculated; after the test, sludge residual water content（SRWC） is obtained by slicing the sludge samples at different heights. The re- suits indicate that the enlargement of geotexile pore size can not improve the dewatering efficiency, and the low permeability layer are formed in 1 h after the test. The utilization of ferric chloride, lime, and fly ash at vicinity area of filter shows the best dewatering efficiency and inhibits the forma- tion of low permeability layer, getting a water content of 200 % （ dry basis） at vicinity area of filter （0 to 3 cm）. And the conditioners of ferric chloride with cationic polyacrylamide or chitosan obtain a water content of 250% （dry basis） at vicinity area of filter （0 to 3 cm）. In actual engineering, the combination of ferric chloride, lime, and fly ash can be used efficiently.