Influence of clay minerals on municipal sludge degradation

The influence of the different clay minerals, especially kaolinite and montmorillonite, was studied to evaluate the effect of mixing ratios on municipal digested sludge (MDS) degradation and the production of off – gas. Different mixing ratios ( clay minerals to sludge) ranged between 10% and 80% by weight as well as various pH ( values varied from 5 to 9) were investigated. It was found that in case of kaolinite mixture, the off – gas production started at the third week of the experiment, while in case of montmorillonite, the production of gas started from the beginning. It was noticed that both minerals gave the maximum volume of off – gas at the end of the third week at pH value of 7. At the begininig of the seventh week total off – gas continued at the same level in case of montmorillonite – sludge mixture at pH 7, but in case of kaolinite – sludge mixture the amount of off– gas increased to reach its maximum volume at pH 9. These set of experiments reflect the importance of the pH value in controlling the production process of off – gas.